NASA CR-174750

MTI 84TR39

NASA-CR- 174750

19850014089

- DEVELOPMENTOF A MULTIPLANE-MULTISPEED

BALANCINGSYSTEM FOR TURBINEENGINES

_ by Michael R. Martin

MECHANICAL TECHNOLOGY INCORPORATED

Preparedfor

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

NASALewisResearchCenter

ContractNAS3-20609

[IBRAnY

LANGLEYRESEARCHCENTER

LIBRARY, NASA

HAMPTON_,VlRGt_NI_

1. ReportNo. 2. GovernmentAccessionNo. 3. Recipient'sCatalogNo.

CR 174750

4. Title andSubtitle 5. ReportDate

Development of a Multiplane Multispeed Balancing System 19 July 1984

for Turbine Engines 6.Pe_ormingOrganizatcoionde

7. Author(s) 8. PerformingOrganizationReportNo.

Michael R. Martin 84TR39

10. Work Unit No.

9. PerformingOrganizationNameandAddre_

Mechanical Technology Incorporated 11. Contractor GrantNo.

968 Albany-Shaker Road

Latham, New York 12110 NAS3-20609

13. Typeof ReportandPeriodCovered

12. SponsoringAgencyNameandAddre_

U.S. Army Research & Technology Laboratories (AVSCOM) Contractor Report

PropulsionLaboratory 14. SponsoringAgencyCode LewisResearchCenter

Cleveland,Ohio 44135

15. SupplementaryNotes

Project Manager, David P. Fleming, Structure and Mechanical Technologies Division

NASA Lewis Research Center, Cleveland, Ohio

16. Abstract

A prototype high speed balancing system was developed under this contract for

assembled gas turbine engine modules at the Corpus Christi Army Depot (CCAD). The

system permits fully assembled gas turbine modules to be operated and balanced at

selected speeds up to full turbine speed. The balancing system is a complete

stand-alone system providing all necessary lubrication and support hardware for full

speed operation. A variable speed motor provides the drive power. A drive belt and

gearbox provide rotational speeds up to 21,000 rpm inside a vacuum chamber. The heart

of the system is a dedicated minicomputer with attendant data acquisition, storage and

I/O devices. The computer is programmed to be completely interactive with the operatot.

The system was installed at CCAD and evaluated by testing 20 T55 power turbines

and 20 T53 power turbines. Engine test results verified the performance of the high

speed balanced turbines.

17. KeyWords(Suggestedby Author(s)) 18. Oi_ibuti_ S_tement

High Speed Balancing Unclassified - Unlimited

19. Security Classif. (of this report) 20. Security Cla=if. (of this page) 21. No. of Pages 22. Price"

Unclassified Unclassified

* ForsalebytheNational Technical Information Service, SpringfieldVir, ginia22151

MT1-17983

NASA-C-168 (Rev.6-71

TABLE OF CONTENTS

SECTION PAGE

__ LIST OF FIGURES ....................... v

LIST OF TABLES ....................... vii

le0 SUMMARY ........ ''eeoe'-e.eoeeeeeee 1

2.0 INTRODUCTION eeeeeeeoe.e.,eeeeeee,.,. 3

2.1 Program History - BalancingFacility Tasks ....... 3

--_ 2.1.1 Detail Design of High-SpeedBalance Equipment . 3

2.1.2 Fabricationand Checkoutof High-Speed

Balance Equipment ............... 3

2.1.3 PreproductionEvaluationof High-Speed

BalancingSystem ............... 4

2.1.4 Site Modificationsand Rig Installation..... 4

2.1.5 VibrationAnalysis of Low- and High-Speed

Balanced Turbines ................ 4

2.i.6 Documentationand Training ........... 4

m 3.0 DISCUSSION ....... "eeeeoeoeoeeeee... 5

3.1 Detail Design of High-SpeedBalancingEquipment .... 5

3.1.1 Prime Mover ................... 5

3.1.2 Speed Increaser ................. 5

3.1.3 Vacuum Chamber ................ 5

3.1.4 Rotor Bearing Structure ............ . 8

3.1.5 LubricationSystem ............... 8

-- 3.1.6 Drive Coupling ................. 9

3.1.7 Vacuum Seal ................... 9

-- 3.1.8 VibrationTransducers.............. 9

3.1.9 Balance Planes ................. 9

3.1.10 SignalMonitoringand Control .......... i0

3.1.11 InherentSafety Features ........... i0

3.1.12 ExpansionCapabilities ............. ii

3.1.13 CCAD Design Review ............... ii

3.1.14 OperatingProcedures .............. ii

iii
TABLE OF CONTENTS (CONT'D)

SECTION PAGE

3.2 Fabrication and Checkout of High-Speed

Balance Equipment ................... 14

3.2.1 Fabrication ................... 14

3.2.2 Checkout of T53-L-13B .............. 14

3.2.3 Checkout of T55-L-IID .............. 23

3.2.4 Additional Testing of the T53-L-13B

Power Turbines ................ 23

3.2.5 T55 Balancing .................. 28

3.2.6 Checkout of New Thrust Bearing Design ...... 35

3.2.7 Shipping and Installation of the System . . . . • 35

3.3 Preproduction Evaluation of the High-Speed

Balance Equipment ................... 36

3.3.1 Engine Test Results ............... 36

3.3.2 Operations Manuals/Facility Repair Procedures . 40

3.4 Site Modification and Rig Installation ......... 40

3.5 Vibration Analysis of Low and High-Speed-Balanced

Power Turbines ..................... 40

3.5.1 T55 Vibration Data from HSBS .......... 42

3.5.2 T53 Vibration Data from HSBS .......... 42

3.5.3 T53 Engine Test Cell Data ............ 48

3.5.4 T55 Engine Test Cell Results .......... 55

3.5.5. T55 Gas Producer Balance ............ 55

4.0 CONCLUSIONS AND RECOMMENDATIONS .............. 61

4.1 Conclusions ...................... 61

4.2 Recommendations .................... 61

APPENDIX A: T53 ENGINE SPECTRUM PLOTS ............ 63

APPENDIX B: T55 ENGINE SPECTRUM PLOTS ............ 83 ---

iv
LIST OF FIGURES

NUMBER PAGE

i T53/T55 High Speed BalancingSystem ............. 6

2 MTI Balancing System - SoftwareData File Overview ...... 13

3 Data Acquisition Flow Chart................ 15

4 Balance Weight Calculation Flow Chart ............ 16

5 TbS/T55 High Speed Balancing System ............ 17

6 Responseof T53 Before and After Balance at 2750 rpm . . . 18

7 T53 Rotor Amplitudesfor As-InstalledCondition ....... 20

8 First T53 Rotor Vibration at Probe 5 After Balance on

Planes 2 and 3 ...................... 21

9 T53 Rotor Response Showing Spline Shift ........... 22

I0 T55 VibrationData Through 16,000 rpm (Serial No. 265503) • • 25

ii Effect of Preload on T53 Vibration ............. 27

12 Power Turbine Vibrationbefore and after Balancing in the

HSBS, T55 Serial No. 265503 ............... 29

13 Power Turbine Vibrationbefore and after Balancing in the

HSBS, Serial No. 268922 ................... 30

14 InitialVibrationLevel in HSBS, Serial No. U00257 ...... 31

15 T55 VibrationLevel in HSBS CTurbineU00559) ......... 32

16 T55 (U00559_VibrationLevel After PermanentBalance

Weight Grind ......................... 33

17 T55 (SerialNo. 268922_ After PermanentBalance Weight Grind . 34

18 VibrationLevel in HSBS, Turbine End (T55 Serial No. 268922) . 37

19 T55 Overall Engine Vibration ........ -......... 38

20 T55 FrequencySpectrum,SerialNo. 268922 ..... ..... 39

21 Layout of H_gh Speed Balance Machlne ............ 41

22 T55 VibrationLevel in HSBS, Turbine End/SerlalNo. 265530 . 45

23 T53 VibrationLevel in HSBS, Turbine End/SerlalNo. 8873 . . . 49

24 T53 VibrationLevel in HSBS, Turbine End/SerlalNo. 1541 . . . 50

25 T53 VibrationLevel in HSBS, Turbine End/SerlalNo. 9925 .... 51

26 T55 Engine Test Cell Data - FrequencySpectrum ....... 59

27 T55 Engine Test Cell Data _ FrequencySpectrum ........ 60

V

r__

LIST OF TABLES

NUMBER PAGE

1 MAJOR MECHANICAL COMPONENTS .................. 7

2 RESULTS OF INSPECTION& MEASUREMENTOF T53 PILOT BORES AND

PILOT DIAMETERS ........................ 24

3 T55 VIBRATIONDATA IN THE HSBS ............... . 43

4 T53 VIBRATION DATA IN THE HSBS ................ 46

5 T53 ENGINE TEST CELL DATA, V4 SENSOR ............. 53

6 T55 ENGINE TEST CELL DATA, V3 SENSOR ............. 56

7 T55 GAS PRODUCER LOW-SPEED BALANCE CHECK ........... 58

Vii

i.0 SUMMARY

Rotordynamic analysis of the T53-L-13B engine showed that the power turbine

passes through'a bending critical speed. A similar analysis performed on the

T55-L-IID indicated that its power turbine responds to a bending critical

speed and is no longer rigid at its maximum speed. Based on these findings a

high-speed balancing machine to handle both rotor types was designed and

constructed. The system was designed for use at the overhaul facility at

Corpus Christi Army Depot (CCAD).

The balancing system is a stand-alone system including a drive motor, speed

increaser, vacuum chamber, and bearing support structure as well as the asso-

_-- ciated auxiliary systems such as the lubrication system and vacuum pump. The

control console allows the operator to remotely control the rotor speed and

also includes monitoring of vital test parameters. A dedicated minicomputer

__ handles data acquisition and determines the necessary balance correction for a

precision high-speed balance using the stored influence coefficient technique[l]. The system software was designed for use by a semiskilled operator

and requires no previous computer experience. Expendability to T700 power

turbines and automated metal removal was anticipated and is provided in the

design of the hardware.

After development of the system at Mechanical Technology Incorporated (MTI),

it was shipped to CCAD and evaluated over the period of a year. During the

testing period a total of 40 power turbines were tested in the high speed

__ balancing system (HSBS), and the corresponding 40 engines were analyzed in the

engine test cell to correlate the vibration levels recorded in the HSBS with

the power turbine's contribution to the overall engine test cell vibration

levels. The test program clearly demonstrated the ability of multi-

-- plane/multispeed balancing procedures to balance production hardware in the

overhaul cycle.

-- The successful correlation of HSBS vibration levels with engine test cell

vibration levels allowed CCAD personnel to use the HSBS to evaluate the effect

of other changes to the T53 power turbine balance procedure. Using this

__ feature of the HSBS, a change in the current low-speed balance procedure for

T53 power turbines was evaluated and found to produce significantly smoother

running engines than those currently being overhauled. Using the HSBS not to

balance but to test turbines to their full operating speed demonstrates an

--- important benefit derived from the ability to take meaningful data representative of behavior in an engine throughout the full operating speed range of

the power turbine.

2.0 INTRODUCTION

In March 1977, Mechanical Technology Incorporated contracted to perform a

rotordynamic evaluation of the T53-L-13B helicopter engine and a review of the

test cell and balancing procedures being used in the overhaul procedure. The

analysis predicted multiple critical speeds in the operating range of the

power turbine. A review of T53 vibration test data from test cells and from

the airframe was concluded in 1978 and confirmed the results of the analysis.

NASA CR-135449 is the final report for the three-task effort. J2]

A companion project, conducted under NASA Contract NAS3-19408, demonstrated

that the T55-L-IID power turbine operated in the flexible regime due to a

bending critical speed above its maximum operating speed. J3]

The scope of this project, NAS3-20609, was then extended from the three

original tasks discussed in [2] to include the design, manufacture, and testing of a multispeed/multiplane balancing system for use on both T55 and T53

power turbines.

The following sections summarize the program history for the five-task design

and implementation effort. Detailed results for these tasks are presented in

Section 3.

2.1 Program History - Balancin_ Facility Tasks

2.1.1 Detail Design of Hi_h-Speed Balance Equipment

The preliminary design was begun in September 1978. The first coordination

meeting was held at CCAD October i19 1978. Incorporation of the input from

CCAD personnel and input from potential hardware suppliers into the preliminary design was accomplished by December 12, 1978 and the preliminary design

was submitted to CCAD on this date. Ordering long lead items was authorized

by NASA at this time. A complete set of drawings was forwarded to NASA in

January 1979. Design approval from NASA was received in March.

2.1.2 Fabrication and Checkout of High-Speed Balance Equipment

Deliveries of all mechanical hardware and computer equipment were completed by

April 1979. Fabrication and assembly was completed in August. The initial

--- system debugging was performed with the T53 support structure installed. A

thrust bearing failure in October 1979 damaged some of the T53 support structure, as well as the rotor being tested. The balance machine support structure was changed to T55 hardware and the development of the T55 balancing plan

continued. In January 1980 the balancing system was switched back over to T53

hardware incorporating design changes based on analysis of the bearing failure. Balancing of the T53 power turbines was halted in April 1980 due to

-- instabilities caused by a bad spline fit in the power turbine. After high

speed balancing five T55 power turbines, the system was demonstrated to NASA

and AVRADCOM in May 1980. The T55 balance plan was finalized in August. In

July and August 1980, components of the HSBS damaged during the bearing fail- ,

ure were redesigned and new hardware installed. Additional changes were made

to improve the operator-balance-machine interface. The T53 balancing exper-

__ iments were concluded and the balancing system was prepared for shipping to

Corpus Christi.

-- 3
2.1.3 Preproduction Evaluation cf High-Speed Balancin_ Szstem

Work under this task was begun during December 1980. Two T55 power turbine

modules (previously high-speed balanced at MTI) were run in the HSBS after

installation in Test Cell 2B at CCAD. A trim balance was performed on one of

the power turbines. After inspection by CCAD personnel, the power turbine

modules were assembled into engines in the overhaul cycle and evaluated in the

engine test cell during the month of April 1981.

2.1.4 Site Modifications and Ri_ Installation

Mechanical and electrical preparations were completed in Test Cell 2B at CCAD

during October and November 1980. Operational tests were completed in December.

2.1.5 Vibration AnalTsis of Low- and High-Speed Balanced Turbines

The testing phase during which the HSBS was evaluated in the overhaul facility

was accomplished from July 1982 to November 1983. A total of 40 power turbine

rotors were operated in the HSBS and then tracked through the engine assembly

process and analyzed in the engine test cell.

2.1.6 Documentation and Trainin_

Based on the experience gained in the testing phase, the operator and systems

manuals were revised as necessary. The training was accomplished throughout

the testing thanks to the active participation of CCAD personnel. ---

4
3.0 DISCUSSION

• This section relates the results of work accomplished in the technical tasks

authorized under this contract with the exception of the three-task analytical

effort discussed in [2].

3.1 Detail Design of High-Speed Balancing Equipment

In this task, a detailed design of a high-speed balancing facility was

-_ prepared. The facility was designed to establish high-speed balance criteria

for T53 and T55 power turbines, evaluate power shaft splines, and develop

procedures for production high-speed balancing at the Corpus Christi Army

Depot overhaul center. Other design criteria included: meeting OSHA safety

requirements, supplying bearing lubrication, providing for vacuum operation

and ready access to proposed correction planes. Vibration sensors were

located to allow determination of rotor mode shapes and evaluation of

correction plane sensitivities. The design was required to be free of disruptive resonances and to use as much actual engine hardware as practical. The

design efforts were coordinated with appropriate CCAD personnel to ensure that

the requirements of the ultimate user would be met. Expansion capabilities

for the high-speed balancing of T700 power turbines and automated metal

removal were provided for in the design.

All major components of the balancing system are standard commercial products

in order to maximize system reliability. Figure 1 shows the complete balancing system. Each of the major components are summarized in Table 1 and

discussed in the following subsections.

3.1.1 _Prime Mover

The power turbine rotors to be balanced required an end drive arrangement.

Sufficient torque was required to drive at a constant speed and also to accelerate against the drive train and power turbine rotor inertias. Meeting these

power needs required a maximum torque of 27 Nm (20 ib ft) and a speed range of

600 - 21,000 rpm. Speed regulation within ±1% was necessary for the acquisition of accurate vibration data. After reviewing several potential prime

movers such as ac motor/clutch, air/steam turbine, dc motor and variable speed

ac motor, it was decided that the variable speed ac motor best met the program

objectives.

3.1.2 Speed Increaser

The motor speed of 1725 rpm needed to be stepped up to provide the 16,000 rpm

operating speed for T55 turbines and the 21,000 rpm operating speed for the

T53 power turbines. A low loss, low inertia speed increaser capable of smooth

operation throughout the entire speed range was required. After reviewing

various approaches a combination V belt and spur gear increaser was selected.

3.1.3 Vacuum Chamber

The vacuum chamber design serves two important functions. It provides a low

hp loss environment which reduces the drive requirements of the balancing

system and it also provides for the operator's safety. Reducing the horsepower required to drive the turbines to full operating speed is accomplished by

5
Computer/Control

Console Auxiliary Control Panel

CRT Display/Terminal

Gearbox

Test Rotor (T53)

_Vacuum Chamber

_ Hydraulic PumpVac, Chamber Cover

Lube Oil

Scavenge Pump

Figure 1 T53/T55 High Speed Balancing System

6

MTI-19257
J ! l I ) / 1 ) ] 1 ] 1 1 ! ]

TABLE i

_JOR HECII_ICAL COMPONENTS

ITEM VENDOR SI SPECIFICATION ENGLISH SPECIFICATION

Variable Speed Drive Control Product• Corp. • 45 kW 0 181/rad/s m 60 hp @ 1725 rpm

(REGADYNE) Chicago, Ill. I 5 - 180 rad/s continuously • 50 - 1725 rpm continuously

variable speed with 0.1% variable speed with 0.1%

regulation, regulation.

• 22 N.m torque O 75% speed • 16 Ib-ft torque @ 75% speed

• 8 N,m torque @ 100% speed • 6 Ib-ft torque @ 100% speed

• accelerate 0.5 kg m2 tnertta m accelerate 1775 Ib-tn.2

@ 10 radle 2 inertia @ 100 rpm/•

Gearbox Sloan and Be•chaff Inc. • 5.803=1 ratio increase • 5.803:1 ratio increase

(SUNDYNE) Springfield, N.J. • lee• than 5.2 kW loss • lees than 7 hp los•

• ball bearing on input shaft • ball bearings on input •haft

= Journal tilting pad bearings • Journal tilting pad bearing•

on output •haft on output shaft

• axial hydrodynamic thrust • axial hydrodynamic thrust

bearing on output •haft bearing on output •haft

• 150 kW O 2160 rad/s • 200 hp @ 20,600 rpm

• lubricate with Type A ATF • lubricate with Type A ATF

Vacuum Pump Kinney Vacuum Co. • maintain 1.3 kPa absolute • maintain I0 torr absolute

(KDH 80) Boston, Mass. pressure pressure

• discharge effluent to have • discharge effluent to have

99.95% filter efficiency 99.95% filter efficiency

Gearbox Auxiliary Oelaval • 190 rad/s drive provides • 1800 rpm drive provides

Lube Pump IMO Pump Div. 0.3 I/s o 340 kPa 5 gpm @ 50 pstg

(IMO C313A-106) Trenton, N.J. • handle type A ATF from handle Type A ATF from

15 to 93 o C 60 to 200o F

Bearing Lubrication Tr|-Line Corp. I 114 I reservoir • 30 gel reservoir

System Syracuse, N.Y. m deliver 38 ml @ 140 to • deliver 0.6 gpm @ 20 to

1400 kPa 200 pstg

• pump MIL-L-23699C from • pump MIL-L-23699C from

15 to 50 ° C 60 to 120° F

_J
reducing the air pressure inside the chamber to 1.3 kPa (i0 tort). Safety is

provided by the 1.3-cm (i/2-in.) thick chamber wall that is capable of

containing a blade loss and most disk failures. Maximum energy disk burst

containment is provided by 2.5-cm (i-in.) aluminum plate near the disks.

The chamber is cylindrical in shape with a horizontal cut that is hinged

allowing convenient access to the interior of the chamber. A double acting

hydraulic cylinder on each end of the chamber provides a cover lift in 90

seconds as well as providing a mechanical clamp to hold the cover shut. With

the chamber evacuated an additional 12.2 kN (279000 ib) force due to atmospheric pressure assures the cover remains closed and seated properly. After

opening the chamber the cover is held open by both a mechanical and hydraulic

system. A safety rod normally stored in the cover is swung into a vertical

position and locked in a detent on the chamber base. The double acting

hydraulic cylinder requires 7 MPa (i000 psi) to allow the cover to descend.

Without the pump being turned on_ this pressure is not available. An automatic and a manual locking valve are provided in the hydraulic circuit to ensure

that the cover remain open.

3.1.4 Rotor Bearin_ Structure

The primary objectives of the bearing pedestal design were threefold. First,

and most important, was the requirement that the balance machine support

structure accurately simulate the characteristics of the engine supports,

resulting in dynamic behavior of the power turbine in the HSBS indicative of

the power turbine behavior in an assembled engine. The second design objective was to allow for the operation of both T55 and T53 power turbines as well

as expandability to handle T700 power turbines. The final objective of the

bearing structure design was ease of installation and removal of the power

turbines so as to provide for production high-speed balancing capabilities.

The design simulates the characterstics of the engine supports while maintaining interchangeability between rotor types by using a substructure which

remains constant for all engine types and a superstructure tailored to the

particular engine type that uses an optimum amount of actual engine hardware.

The superstructure design provides stiffness and damping values equivalent to

the values for the engine supports. The T53 forward roller bearing and housing are slave items from engine stock that bolt up to the T53 superstructure.

The T53 aft engine bearing fits into the T53 superstructure which contains

flexures simulating hot section stiffness and damping. The T55 forward roller

bearing and housing are also slave items from engine stock which bolt directly

to the front T55 superstructure. The T55 engine power turbine module contains

the aft engine bearings and supports and bolts directly to the aft T55 superstructure.

Preload is supplied to the engine bearings by a 15 = angular contact thrust

bearing loaded by wavy washers. Variable thrust loads from 0 - 530 N (0 -

120 ib) can be applied by a screw adjustment that varies the compression of

the wavy washers.

3.1.5 Lubrication System

Oil is supplied to all power turbine bearings and the gearbox. The ac drive

motor and all pumps have permanently lubricated bearings. The gearbox is

8
supplied with automatic transmission fluid in a closed loop. The engine bearings for both T55 and T53 require MIL-L-23699C synthetic oil in flow rates of

-- 4.5 kg/h (i0 Ib/hr) forward and 23 kg/h (50 ib/hr) aft. The thrust bearing

used to preload the turbine bearings is supplied with a synthetic oil/air

mist.

In order to operate in a vacuum the oil system required a reservoir external

to the vacuum operation. When the vacuum is released, the oil in the internal

sump is automatically returned to the external reservoir.

3.1.6 Drive Couplin_

A miniature flexible disc coupling was selected as the means to connect the

drive system to the power turbine shaft. The model selected was a Rexnord

style CD size 62 with a torque capability of 34 Nm (300-1b/in.).

The 20.3-cm (8-in.) long, 1.6-cm (5/8-in.) diameter shaft that connects the

hub flexures permits the required dynamic misalignment capabilities and

__ provides the pass through the vacuum seal.

3.1.7 Vacuum Seal

The dynamic motion of the coupling spool had to be taken into account in the

seal design since a stable spindle arrangement using carbon seals was prohibitively expensive to design and implement. A floating seal cartridge with

known leakage was selected because the vacuum pump capacity easily offset the

leakage. The cartridge contains three viton lip seals with silicone vacuum

grease as the lubricant.

3.1.8 Vibration Transducers

Noncontacting displacement probes by Bently Nevada were selected to monitor

shaft vibration. Piezoelectric load cells by Kistler were selected to monitor

bearing loads. The location of the vibration probes was selected based on the

predicted mode shapes from the rotordynamic analysis. For both rotor types,

-- the probe locations are near the front bearing, shaft midspan, and near the

first turbine disc. A temporary probe was also installed in the disc seal

surface near the spline on the T53 turbine to study spline effects. Two

_ probes are located at each location to allow observation of shaft orbits on an

oscilloscope. The load cells are located in the bearing support structure.

3.1.9 Balance Planes

The location of the balance planes was determined by the appropriate Department Maintenance Work Requirement (DMWR) and accessability in an assembled

power turbine module. The analysis had predicted that the existing balance

planes were adequate for high-speed balancing. A shaft midspan balance plane

was also evaluated for each rotor type. The accessible existing balance

planes for the T53 power turbine are at either end of the enlarged section on

the shaft and on the aft side of the second stage turbine disc. The T55 power

turbine balance planes are at the forward end of the shaft and on the forward

turbine disc, forward side. Two planes specified in the DMWR were not available due to accessability problems; these are the forward turbine stage on the

T53 power turbine and the aft turbine disc on the T55 power turbine assembly.

9
These two planes cannot be reached with a grinder in the assembled configuration.

3.1.10 Signal Monitorin_ and Control

The operating condition of the balancing system can be monitored at either the

test stand or the operator console which is located remotely from the test

stand for safety reasons. The console contains meters for display of rotor

vibration, lubricant pressure, bearing temperatures, and other indicators of

the test stand status. A speed control potentiometer permits the operator to

control rotor speed while observing a digitial speed display. The test stand

controls duplicate most of the functions of the console allowing the operator

to check for proper operation at low turbine speeds with the vacuum chamber

cover open. The design, fabrication, and operating procedures of the high

speed balancing system emphasize safety. Since any type of high-speed rotating machinery is potentially dangerous, the operator must recognize the limitations of the hardware and his ability to control it. It is, therefore, the

operator that determines the ultimate safety of the system. The following

system parameters are monitored:

• Speed - A Spectral Dynamics fiber-optic tachometer provides a

once-per-revolution signal that is used for both digital speed readout

and to determine the phase angle associated with the vibration readings.

• Thrust Bearin_ Temperature - A thermocouple is attached to the outer

ring of the thrust bearing. A 135°C (275°F) meter trip is recommended.

A temperature above the trip point activates a warning light and an

alarm.

• Oil Temperature - A thermocouple senses the aft bearing drain oil

temperature. A 149°C (300°F) meter trip is recommended. A temperature

above the trip point activates a light and an alarm.

• Vacuum - A pressure sensor monitors chamber pressure. The meter trip

point activates the warning light and an alarm. 14 kPa (2 psia) is

recommended.

• Lubrication Oil Pressure - Lube oil pressure is monitored at the pump

outlet. The meter on the operator's console has a low trip capability.

A 140 kPa (20 psig) trip is recommended. The trip deactivates the

drive motor in addition to the warning light and alarm.

• Power Turbine Vibration - Analog meters display overall vibration from

the forward and aft displacement probes.

3.1.11 Inherent Safety Features

A number of safety measures are built into the system to remove drive power

from the motor when a potential hazard exists. If low oil pressure exists the

motor cannot be started. In addition, if low oil pressure occurs during a

run, drive power automatically is removed from the motor. Low vacuum removes

drive power from the motor if the console controls are in use to run high speed

i0
tests. In addition, depressing the emergency stop button automatically

removes drive power from the motor allowing the rotor to gradually decelerate.

The test stand speed control limits the maximum rotor speed to i000 rpm which

permits adequate identification of mechanical readiness for high speed operation while the operator is in the test cell.

There are several features that prevent operating the rotor from the console

when there is someone in the test cell. Both the console and the test stand

speed control selector switches must be in the same position in order to start

the drive motor. When they are both in the "Test Stand" position, the console

speed control is disconnected. The "Power On" switch on the Regadyne motor

control cabinet can be turned off while working in the test cell.

3.1.12 Expansion Capabilities

Throughout the design of the high speed balancing system, it was acknowledged

that the purpose behind the development of the system was not just to high

speed balance T53 and T55 power turbines but to develop a capability, deliver-

- able to the overhaul facility, that will enable the facility to handle the

balancing of flexible rotors in general. Specifically, the General Electric

T700 helicopter engine, whose power turbine operates above two bending critical speeds, was chosen as a future capability of the HSBS. The substructure

and superstructure of the bearing supports provides the means by which the

balancing system's capabilities can be expanded to accomodate any rotor smaller than the T55 power turbine rotor.

Additional expandability to a laser-based, automated, metal removal system

was also provided for in the design. The internal configuration of the chamber allows straight line access to each balance plane. The vacuum chamber

cover can be readily modified to carry laser optics.

-- 3.1.13 CCAD Design Review

Three design reviews were held at CCAD so the design could benefit from the

__ experience of the overhaul facility personnel regarding production oriented

use in the engine overhaul cycle. Characteristics of the engine build and

engine test processes were also discussed.

-- CCAD personnel recommended locking out the drive spline with a four'jaw collet

mechanism that eliminates spline clearance for both T55 and T53 power turbines

due to potential problems from variations in fits of worn engine hardware.

The T53 shaft to turbine disc spline with a four-jaw collet mechanism that

eliminates spline clearance had already been shown to affect the dynamics of

the engine. Therefore, plans to observe the effect of this spline on

vibration in the HSBS were outlined.

3.1.14 Operating Procedures

The balancing system operating procedures are based on user friendly interactive software that allows operation by personnel with no previous computer

experience. Mechanical experience is required as is the case for operation of

__ any high speed equipment.

ii
The steps required to install a rotor in the HSBS are given in detail in the

operators manual (MTI report no. 81M66). The rotor module is clamped into

place and the drive connection made. Lubrication, electric drive, and vacuum

systems are checked for proper operation. The installation procedure takes

approximately 15 minutes. If there are no audio or visual alarms, the system

is ready to run the computerized data acquisition routine.

Monitoring the operating condition of the system can be accomplished at either

the test stand or the operator console. For safety reasons, the operator

console's location is remote from the test stand. Oil temperatures and pressures, rotor speed, and vacuum and bearing temperature are monitored. Visual

and audible alarms signal parameters exceeding adjustable preset limits. The

only instance in which the system cannot be operated by the operator is in the

event of loss of oil pressure. If this problem occurs, interlocks prevent

system operation and the drive system automatically shuts down.

Low speed operation of the system (less than I000 rpm) can be accomplished

from the auxilliary control panel located on the test stand. This capability

permits the opera=or to check proper operation of all auxilliary systems

before leaving the test stand. Low speed operation can be accomplished with

the vacuum chamber cover open, thus allowing the operator to conduct a visual

check of the rotating turbine. Interlocks prevent high speed operation with

thecoveropen.

Figure 2 is a software block diagram, showing the main communication paths

that exist among the three major files, the four main software subsystems, and __

the various utilities for listing the contents of the system files. The

interaction of the files, subsystem, and utilities will be outlined in the

subsequent discussion. The functions of each component are listed below.

• Files:

- Configuration File - Defines how rotor is to be balanced

- Run File - Contains vibration data for a run ---

- IC File - Contains influence coefficients

• Main Subsystems:

- CFIGEN - Generates configuration file

- DATA - Acquires rotor vibration data

- ICMAIN - Generates influence coefficients

- BALSYS - Calculates correction weights

• Utilities:

- CLIST - Lists a configuration file

- LISTIC - Lists part or all of IC file

- DATLST - Lists run file.

These definitions show the clean organization and modularity of the system.

The configuration file is set up by the balancing engineer to control the

balancing process for a particular type of rotor. Whenever data are acquired

by an operator, synchronous amplitude and phase information is stored as a

function of probe number and speed in the run file. Each run has a separate

file and the system keeps track of file numbers. The influence coefficient

file is filled by the influence coefficient subsystem and is accessed by the

balancing subsystem to perform balancing calculations.

12
CFIGEN

--- "J DATA

FileUrati°n "-I

Run Data Files

m

ICMAIN

CLIST Influence f 1

;oefficient I DATL ST I

File I_. j

-- Listing BALSYS I LISTIC I

I_..... _1

_-- " "_ng

Figure 2 MTI Balancing System - Software

Data File Overview

13
Subsystem CFIGEN creates the configuration file which includes information

such as the number of correction planes, number of sensors, balancing speeds,

speed tolerance, angular relationships between sensors, etc. Subsystem DATA

acquires the vibration data and fills the run file. Subsystem ICMAIN processes run file data to generate influence coefficients and subsystem BALSYS

uses configuration file, run file, and influence coefficient file to determine

correction weights to reduce the vibrations measured in a particular run.

Various utilities are provided to allow file contents to be reviewed: CLIST

shows configuration file contents; LISTIC provides a printout of influence __

coefficients; and DATLST provides a printout of run file vibration data.

Flow charts for the two programs, DATA and BALSYS, used during production

balancing are shown in Figures 3 and 4, respectively. For a detailed

description of the system software, refer to the Balancing Systems Software

Manual (MTI Report No. 81M13).

3.2 Fabrication and Checkout of Hi_h-Speed Balance Equipment

3.2.1 Fabrication

The fabrication of the mechanical hardware was accomplished as follows:

• Modify Sundyne gearbox output shaft

• Mount vacuum chamber base to machine base

' Mount driver on base

• Mount gearbox on base ---

• Install vacuum chamber cover

• Assemble and test chamber cover hydraulics

• Install T55 adaptive hardware and align ....

• Mount auxilliary control box on base

• Install gearbox lubrication system

• Remove T55 adaptive hardware and install and align T53 hardware

• Build and install drive shaft vacuum seal

• Assemble hub adaptors for both rotor types

• Install lube oil scavenge system

• Install variable speed drive controller, vacuum pump, and b_aring

lubrication system

• Connect computer and CRT

• Install instrumentation, temperature, vacuum, vibration

• Calibrate lube oil flow rates to specification

• Install preload bearing assembly

• Install T53 rotor

• Conduct operational tests to 900 rpm with chamber cover open and to

1500 rpm with chamber evacuated

• Debug operating systems.

The assembled hardware is shown in Figures 5a and 5b.

3.2.2 Checkout of T53-L-13B

Figure 6 represents synchronous vibration amplitude for the first T53 power

turbine operated in the HSBS. The as-installed amplitudes for the turbine and

14
I AcRunquisition Data I

I DisplaySpeed Window I

and Monitor RotorSpeedI

- '!

I GetSensor Data I

_Yes

- _ "

_ I NO

I.Notify OperatorI

i =

I DisplayData I

- i

IRun _'°rDataO°_' °

File In

-- !Balance

°°,Speed.°_°.Ixt ,

Speed No

Yes

-- I Data Deleted RunI-_ No Data

__ Yes

Figure 3 Data Acquisition Flow Chart

841277

15
Cntate )

BALSYS

Program

I Specify Rotor I

Type and ID I

I

Locate Run File

Balance

Masses

Weights and No

PredictedResidual /

Vibrations.

I Install --

Yes IWeights I

Yes Least _-

Squares

Minimization

No

Yes No Continue Loop

" Weighting _ Until Satisfied --

Figure 4 Balance Weight Calculation Flow Chart

841278
Hydraulic PumpVac Chamber Cover

Lube Oil

..... Scavenge Pump

B8-1871t

a, Test Equipment and Computer Support System

b. Test Rotor Installed in Vacuum Chamber

Figure 5 T53/T55 High Speed Balancing System

17

MTI-21986
_m mil

o - Probe 6

250 1.01

Before Balance

"-" 200

7.5iProbe Probe

._ 5__ 6

150- Probe 5

5.0 -

o Af'ter Balance

= i00 o

.=

O

'.2,:5

50-

O- 0 l i -I l l

2.5 5.0 7.5 10.0 12.0

Speed (1000 rpm)

Figure 6 Response of T53 Before _nd After Balance at 2750 rpm

841248

18
sensors sh@w a rapid increase that starts at approximately 2500 rpm that

agrees well with the predicted response to the critical speed at 3000 rpm. At

this early stage of the balancing tests conservative limits had been established for maximum amplitude, consequently this initial run was stopped at

2750 rpm and balance weights were calculated. Later in the tests, it was

learned that this peak can easily be passed through and that the amplitudes

drop as fast as they rise in a very well defined peak. Influence coefficients

were developed at 2750 rpm and a successful balance resulted in the amplitudes

labeled "after balance" shown in Figure 6.

After this balance run, the power turbine rotor was removed for inspection.

The inspection revealed that the nozzle had rubbed against the rotating disc

-- spacer. Tolerance stackup of the nozzle fixture was the cause. The nozzle

and fixture were eliminated from the remainder of the tests. Further

inspection of the balance system revealed wear on the shaft passing through

the vacuum seal. The seals were replaced and a new shaft with Rockwell C60

material was installed.

Figure 7 shows the as-installed condition from the test run following the

-- rebuild in which the first critical was traversed. The buildup in amplitude

at 13,000 rpm also agrees with the analytical predictions. The peak evident

at 8000 rpm is structural and does not respond to balancing. At this point in

__ the testing, a considerable number of trial weight and balance runs were made

to develop influence coefficients and to develop the balance plan. Figure 8

shows the results of a two-plane, two-speed balance which allowed operation to

17,400 rpm. Synchronous amplitudes became increasingly unstable in the upper

speed range, making it impossible to acquire consistent high speed data.

Further testing demonstrated the problem to be twofold, with probe bracket

resonance and motion of the machine base both contributing to the oscillating

-- levels. After modifying the probe bracket, the vibration levels were more

stable and influence coefficients were developed for 17,200rpm. Development

of the influence coefficients at the higher speeds was hampered by vibration

amplitude variations caused by shifting of the spline.

Figure 9 represents vibration amplitude versus speed (measured by the turbine

end probes) in a test run that clearly showed a spline shift. Shifts were

occurring at both high and low amplitudes and at various rotor speeds indicating the possibility that a destabilizing mechanism might be involved. Instabilities caused by problems with the thrust bearing might provide sufficient

excitation to cause a spline shift. Consequently, the grease packed thrust

bearing was replaced with an oil fed bearing that could provide more preload.

The new thrust bearing resulted in no change in response at the same preload

used in the earlier runs. A series of tests was conducted in which the preload

on the aft bearing was varied by making changes in the axial load on the thrust

bearing.

-- A lower than nominal preload resulted in no change in response. A higher than

norraal preload raised the rotor speed at which the shift occurred. The measured vibration at the higher speeds was the lowest observed at this time. The

thrust bearing failed at 20,500 rpm due to lack of lubrication (additionally,

18,240 rpm was later determined to be the bearing manufacturers recommended

maximum speed). With the sudden loss of preload, rotor amplitudes became

__ excessive and the forward roller bearing was overloaded to failure. Damage

was limited to the bearings and bearing support structure.

-- 19
Probe 6

um mil

200_

_" Probe 5

150-- Probe5

S.O10G--

2.sZ --

O- I

5 i0 15

Speed (i000 rpm)

p

Figure 7 T53 Rotor Amplitudes for As-Installed Condition

841247

20
Balance Planes

_ 3

2

IO

200-

0 - 0 I I I I

-- 1460 2760 4760 6620 11,120 14,400 15,000 17,400

Speed (rpm)

Figure 8 First T53 Rotor Vibration at Probe 5 After Balance on Planes 2 and 3

-- 841246 21
Probe 6

um mil

o_ o I I I

0 5 i0 15

Speed (i000 rpm)

Figure9 T53 RotorResponseShowingSplineShift

841245

22
A survey of the T53 spline measurements was made to determine the optimum fit

-- for future runs. The inspection revealed that all of the T53 rotors at MTI

were worn such that clearance in the spline pilot exceeded blueprint tolerance. Additionally, two out of three exceeded the CCAD overhaul procedure

wear specification which was used to determine when chrome plating was

required as corrective action. The tabulated values for each of the rotor

assemblies are shown in Table 2.

3.2.3 Checkout of T55-L-II0

The T53 supports were removed and replaced by the T55 superstructure. The T55

probe bracket, which permits displacement orbit determination in three planes

along the power turbine shaft, was installed. Rotor serial number 265503 was

installed for system checkout. After checking the mechanical runout, calibrating the oil flow rates and setting the preload of the grease-packed thrust

bearing at 120 N (27 ib), the balancing system was ready to run.

Early balancing runs of the T55 power turbines were hampered due to a slow

acceleration rate and problems with cooling the thrust bearing. The number of

seals in the drive shaft seal cartridge was reduced from 3 to i and air cooling

was added to the thrust bearing. Measurements of drive current were made to

analyze the slow acceleration problem. It was discovered that the full

44.7 kW (60 hp) was being used. The direction of rotation was reversed,

reducing windage losses and providing an acceptable acceleration rate. The

thrust bearing temperature, however, still limited the duration of a test run.

A representative plot of vibration amplitude versus speed for the first T55

power turbine is shown in Figure I0. The large peaks in amplitude at approxi-

-- mately 4000 and 8000 rpm were diagnosed as structurally related resonances.

One of the tests performed to determine this was the use of an independently

mounted vibration probe to assess whether the rotor itself was vibrating at

the large amplitude or if relative motion of the probe bracket was contributing to the peak readings. The data taken with this probe was much lower,

suggesting a structurally related problem driven by rotor vibration. Impact

tests on the probe bracket revealed natural frequencies present in the range

of the large indicated amplitudes. Various durometer elastomers were used to

attempt to isolate the probe bracket. The peak amplitudes were not reduced

but the repeatability of the vibration data was improved at the higher speeds.

3.2.4 Additional Testing of the T53-L-13B Power Turbines

The deep groove thrust bearing used for thrust loading the T53 power turbine

was replaced with an angular contact ball bearing lubricated by an oil mist.

The new bearing could operate with a preload in excess of 450 N (i00 ib). The

modifications to the design are summarized in the following list:

• provisions for adjustable thrust load

• increased number of wave springs

" oil mist lubrication

• common thrust bearing size for both the T53 and T55 engines

• replace the ABEC 25 bearing with an ABEC 9 bearing

• more rigid thrust pad assembly incorporating precision machining to

eliminate alignment problems.

23
TABLE 2

RESULTS OF INSPECTION & MEASUREMENT OF T53

PILOT BORES AND PILOT DIAMETERS

ITEM i A B !i C FINDINGS

SHAFT No. i 2.995 cm Min 2.999 cm Min - Severe

(SN P6621) (1.179 in. Min) (1.181 in. Min) fretting at A*

2.997cm Max 3.002cm Max Conclusions --

(1.180in. Max) (1.182in.Max) • Out of Print

• Needed Plating

• In Rig at

Failure

SHAFT No. 2 3.003 cm Min 3.004 cm Min - Conclusions:

(SN 8707) (1.1824 in. Min) (1.1828 in. Min) • Out of Print

3.004 cm Max 3.005 cm Max only at one

(1.1826 in. Max) (1.1830 in. Max) point

Status

• Usable (Best

Candidate)

SHAFT No. 3 3.001 cm 3.003 cm - Conclusions:

(SN IF010) (1.1815 in.) (1.1822 in.) • Out of Print

• Should be

plated

I I

i

TURBINE No. i - - 3.021 cm • Out of Print

(1.1895 in.) • Worse Case

(Largest Bore)

• In Rig at

Failure

+TURBINE No. 2 - - 3.020 cm • Out of Print

(1.1890 in.) • Usable

TURBINE No. 3 - - 3.007 cm • Out of Print

(1.1840 in.) (Too small)

• Usable - (Best

Candidate)

Print Dimensions

A = B = 3.004 to 3.005 cm (1.1825 to 1.830 in.)

* c (1.1860 to 1.1880 in.)

Power

Sbt+_ l CCAD Overhaul Procedure __ - Chrome Plate if:

A or B < 3.002 cm

PowerSh,_/ (1 •1820 in. )

Power Turbine

Spllne

Connection

24 --
_-_ Figure I_ T55 ViSrationData Through 16,000 rpm (SerialNo. 265503)

25

841244
A T53 rotor was assembled from the shaft and disks that resulted in the tightest pilot fit. The preload was set at 220 N (50 ib). A single speed balance

at 2750 rpm allowed operation to 12,400 rpm. Spline shifts prevented acquisition of consistent data at higher speeds. Test runs with incremental

increases in preload were conducted to study the effect on the spline. The

speed at which the spline shift occurred increased with each increase in

preload, thus allowing the gathering of vibration data at the higher speeds.

After multispeed balancing at 2,750, 12,7509 and 14,400 rpm, the maximum speed

of 21,000 rpm was reached. Figure ii represents the effect of increasing

preload on the vibration data from the turbine end probe for this balance

condition.

The successful operation of the HSBS up to the maximum speed of 21,000 rpm

permitted the beginning of the development of a comprehensive T53 balance

plan. Rotor sensitivity was evaluated at each of the balance planes and

influence coefficients were calculated at 2,750, 13,000, 17,200, and 21,000

rpm. During these tests it was observed that the rotor repeatability was

deteriorating. Testing was halted and the rotor removed for a complete

inspection. The turbine tie bolt was found to be loose and significant spline

and pilot wear was evident. -

The spline teeth on the third test shaft were in better condition so its pilot

diameter was chrome-plated to give a 50 _m (2 mil) clearance with the second

test disks. The rotor was operated to 13,000 rpm in the as-installed condition. A three plane balance at 27_0 and 13,000 rpm allowed operation to

19,500 rpm. Oscillating synchronous amplitude hampered data acquisition at

the upper speeds. Using accelerometers mounted on the balancing system base,

it was discovered that increased vibration of the base coincided with the

onset of the oscillations in synchronous amplitude of the power turbine.

Bolting the frame to the floor eliminated the oscillations. Vibration levels

were acceptable to 21,000 rpm without further balancing.

As mentioned earlier, rubbing problems required that these balancing tests be

conducted without the nozzle installed between the turbine stages. Nozzle

installation requires disassembly and reassembly of the power turbine module

after high speed balancing in order to install in an engine. Consequently,

tests were required to assess the impact of this operation on the balance

quality. The rotor was therefore removed from the HSBS and disassembled,

including separation of the turbine disks. The rotor was reassembled, reinstalled in the balance machine and operated to 21,000 rpm. The vibration

response was unchanged, demonstrating that the nozzle was not required as part

of the module installed in the HSBS.

Problems with spline shifts continued to hamper the gathering of high speed

vibration data. The thrust bearing was still running hot. It was decided to

inspect the thrust bearing assembly and review the design. Inspection

revealed that the bearing was misaligned angularly, and that the thrust pad

was damaged. This damage caused the wave washers to jam thus creating an

uneven preload. The angular contact thrust bearing being used was an automotive bearing. The tolerances, plastic retainer and retainer configuration

were not well suited for a high speed, vacuum application. An ABEC 9 bearing

of the same size, which provided direct inner race lubrication, was substituted. The thrust pad was repaired and the wave washers were replaced. No

shifts were observed in the succeeding balance runs. The need for a new

26
_m rail

250 - 10 -

._ 200 - 8 -

O2

150 - 6 -

,,j

--- _ 100 - 4 -

ra

=_ 50 - 2-

I

0 -- .,1 I I t t t t I I t t l I I t t t I I I t I

0 5 i0 15 20

Speed _i000rpm)

a) 60 Ib Preload

- - Bm rail

250 - I0-

-- _,= 200 - 8 i!'__

zso _ 6 {u

.__ CJ

m

i00 - 4

m,

m

= 50 - 2

--

0 -- 0 t i t I I I I I I I I I I I I I I I t t t

0 5 i0 15 20

Speed(I000rpm)

b) 80 lb Preload

pm rail

300 - 12

250 - 10

= 200 - 8

-_ o 150 - 6

i00 - 4 -

50 - 2-

0 - 0 t t t I I I I t t t t I I f I t t t I I I

0 5 i0 15 20

Speed (i000rpm)

c) 100ibPreload

Figure Ii Effect of Preload on T53 Vibration

ss_s_7 , 27
balance speed between the ones at 12,750 and 17,200 rpm became evident as

different unbalance configurations were evaluated. A series of trial weight

runs were made and influence coefficients calculated for 15,500 rpm.

3.2.5 T55 Balancin_

The bearing support structure was changed over to the T55 superstructure.

Rotor 265503 (with no low speed balancing performed during overhaul) was

installed and run to a speed of 12,000 rpm. A plot of the vibration data for

this run is shown in Figure 12. A two-speed balance at 8,265 and 12,000 rpm owas effective in reducing vibration levels at the upper speeds although the

low speed peak was not reduced. The influence coefficients were updated by

including additional data taken at 14,000 and 16,000 rpm.

Rotor 268922 was installed and operated to a speed of 14,100 rpm in the

installed condition. A balance calculation based on data at 8,265 and 14,000

rpm followed by a trim calculation at 16,000 rpm reduced the levels as shown -

in Figure 13. The plots for this rotor show the power turbine first critical

speed at approximately 9000 rpm as predicted by analysis.

Rotor U00553 was installed in the HSBS and operated to a speed of 8600 rpm.

Data from this rotor was not consistently repeatable and little success was

achieved in balancing. The rotor was removed from the vacuum chamber.

The next T55 power turbine installed was U00257 which ran to 16,000 rpm with

extremely low vibration levels as shown in Figure 14. No balancing was

required for this power turbine. The peak at 9000 rpm on Figure 14 corresponds to the power turbine's first critical speed.

Rotor U00559 (with no prebalance) was operated to 16,000 rpm as installed. -

The vibration amplitudes were reduced significantly as shown in Figure 15, by

balancing at 8,265, 15,000 and 16,000 rpm.

Up to this point all the balancing was performed using collars for temporary

weight addition on the shaft and safety wire wrapped around turbine blades.

Permanent corrections needed to be made on the rotor's existing balance planes

according to the overhaul center's specifications. Since the diameter of the

shaft where the metal would be ground is different than the diameter of the

temporary collars and the diameter of the material removal on the turbine

disks is different than the blade tip diameter where the temporary weights

were located, the weight removal amounts as calculated by the balancing system

require scaling to give the same results.

The correction weights calculated for rotors U00559 and 268922 were replaced

with permanent corrections ground into the rotor. Detailed instructions for

material removal are included in the operator's manual. The synchronous

amplitude versus speed plots for these two rotors with the permanent

correction weights ground in are presented in Figures 16 and 17.

28

I
Speed CIO00 rpm)

b) After Balancing

851518

Figure 12 Power Turbine Vibration Before and After Balancing

in the HSBS, T55 Serial No. 265503 29
_m rail Probe 2 Pro_

5.0- _ Probe 5

i00 - ProSe i

o

= 2.5-

Probe 1

m 50

0

o

u Probe 6

=

0 - 0 I I I I .__

Z 0 5 l0 15 16

Speed (i000 rpm)

a) Before Balancing

um rail

5.0-

10o.

o

2.5-

= _ Probe l

50 - Probe 1 ' Probe 6

° \ / it = robe 6

o 0 I I

z 0 - 0 5 i0 15 16

Speed (I000 rpm)

b) After Balancing

Figure 13 Power Turbine Vibration Before and After Balancing in the

HSBS, Serial No. 268922

84127{5

30
_-_ Prob_

gm mil robe 5

.-. o 200-

= Probe i

5.0 "

= I00 --

2.5 .

= 50 -

o

o _ Probe 6 =

0

_ -_ Probe i

o_ t t t t

5 10 15 _6

Speed(i000rpm)

F_

FigureIA InitialVibrationLevelin HSBS,SerialNo. U00257

841275

r_ 31
tlm 5.0mil.... Probe 2"--_'_ Probe 5

Probe i

I00

Probe i

2.5 ,-_-----Probe6 --

50

o

O- 0 I I I --

0 5 i0 15 16

=

Speed (i000 rpm)

a) Before Balancing

= _m roll o

m 5.0- _.

=

o

=

moo2.5

0 - 0 I I I Probe i

0 5 I0 15 16

Speed (i000 rpm)

b) After Balancing

Figure15 T55 VibrationLevel in HSBS (TurbineU00559)

8412.74

32
,--" _ Prob_

_L. _ Probe 2

o um 5.0mil _ Probe 5

Probe i

i00 -

Probe 6

-_ _ 2.5 - Probe I

_ 50 -- I Probe Probe 6i

. o 0 0 I I I

=o 0 5 i0 15 16

=

Speed (i000 rpm)

_ Figure16 T55 (U00559)VibrationLevelAfterPermanent

BalanceWeightGrind

,u_ m

f

851519 33
cJ

0

=a mil Probe 2 m um

_I Probe 5 ---

_" 5.0-

Probe i

i00 - r-4

Probe i

Probe 6 _= 2.5.

=_o° 500__ 01

0 5 i0 15 16

4.J

Z Speed (i000 rpm)

Figure 17 T55 (SerialNo. 268922) After PermanentBalance Weight Grind

851S20

34
3.2.6 Checkout of New Thrust Bearing Design

The redesigned thrust bearing assembly included the following new features:

• Bearing maximum speed of 22,000 rpm at 900 N (200 Ib) preload

• More rigid thrust pad

• Precision manufacture to improve alignment

• A four jet oil mist aimed at the beating's inner race.

\ The design was first checked out with a T55 power turbine installed in the

HSBS. No change in response was noted for preload changes from 270 to 530 N

.-- (60 to 120 ib). Higher thrust was not tried.

The balancing system was switched over to T53 supports for additional testing.

After a baseline run of the installed T53 power turbine, the existing influence coefficients were used to calculate the correction weights required. A

two-speed 2,750 and 13,000 rpm, three-plane balance resulted in satisfactory

amplitudes up to 21,000 rpm. Preload is applied by moving the thrust pad

assembly until it contacts the thrust bearing housing. Further motion

compresses a spring and develops a thrust. Rotor vibration response was

compared from 220 to 710 N (50 to 160 Ib) preload. Spline shifting problems

.^_ were minimized at 620 N (140 Ib) preload although any amount between 530 and

710 N (120 and 160 Ib) was acceptable. The tolerance of 180 N (40 ib) allows

the operator to adjust the preload by advancing the adjusting bolt 1-I/3 turns

rather than the time-consuming use of a dial indicator to measure the 1.8 mm

- (0.070 in.) deflection. With the preload set at 530 N (120 ib), the bearing

temperature was lower than the original design.

A method was established for permanent weight removal in the T53 disk. A

large plastic sheet was used to cover the open vacuum chamber. Access to the

area to be ground was provided by cutting a hole in the sheet and taping the

_ edges to the disk. A backup seal for protecting the bearings was made by placing a foam strip between the disk and bearing housing. A 1.7 cm (5/8 in.)

diameter grindstone ball was used in a high speed pneumatic tool to remove

metal. A .i0 cm (0.040 in.) deep cut over a 40 ° arc was calculated as the

- replacement for 2.93 grams of safety wire concentrated at the blade tip diameter. The permanent weight removal provided an acceptable replication of the

temporary weight vibration response.

3.2.7 Shipping and Installation of the System

_ The HSBS was dissassembled and crated as required for shipping. The vacuum

chamber base, motor, gearbox and two pumps were left attached to minimize

reassembly efforts. The test cell at CCAD was only accessible through a 1.06

m (42 in.) wide doorway and a narrow corridor. Therefore, the 2270-kg (5000-

Ib) crate, whose dimensions were 1.36 x 1.03 x 3.51 m (53.5 x 40.5 x 138 in.),

had to be handled on its side.

_% Two trips were made to CCAD by MTI personnel, the first to oversee the installation of the hardware, and the second to verify proper operation of the

system.

35
3.3 Preproduction Evaluation of the High-Speed Balance Equipment

3.3.1 Engine Test Results

Two T55 power turbines that had been high-speed balanced at MTI were run in

the HSBS after installation of the system in Corpus Christi. One of the two

turbines, 268922, was checked in the HSBS during a demonstration given to

CCAD, NASA9 and AVRADCOH personnel.

After an initial run to operating speed at which the peak amplitude was i00 _m

(4 mil), the system was demonstrated by using the data from this one run in

conjunction with the stored influence coefficients to calculate a trim

balance. The calculated weights were then installed and the power turbine was

run to its operating speed to check the balance. The resultant peak amplitude

was reduced to a level of 38 Bm (1.5 mil). The trim weights were therefore

ground into the rotor in preparation for engine testing. Figure 18 represents r

the vertical amplitudes at the forward and aft probes for both as installed,

and after high speed trim balancing conditions.

The second T55 power turbine (U00559) was operated to its maximum speed of

16,000 rpm in the HSBS with a peak vibration reading of 50 Bm (2 mil). The two

turbines were inspected and approved by CCAD personnel prior to engine testing.

The first of the two power turbines was successfully run in an engine during a

visit to CCAD by MTI personnel. The engine used for the test had been tested

earlier in the week and then the power turbine was pulled out and replaced

with the one incorporating high-speed balancing. This power turbine module

(268922) had not been low-speed balanced prior to being high-speed balanced.

The engine was retested and showed a decrease in overall engine vibration.

Figure 19 shows the engine test cell vibration readings for the engine, before

and after the power turbine changeout. The entire remainder of the engine,

including harness and instrumentation was the same for both tests. Figure 20

represents a vibration spectrum plot taken from the engine test with the

high-speed balanced turbine operating at 15,600 rpm (97.5%). This breakdown

of the overall vibration signal into its various frequency components shows

that the compressor (N1) frequency now dominates overall engine vibration.

Any further reduction in the vibration levels measured by the casing mounted

test cell instrumentation would require improving the balance of the compres- -_

sot rotor to a level comparable to the high-speed balanced power turbine.

As mentioned previously the engine used for this test had been run earlier in

the week with a different power turbine. The power turbine that was removed

was tested in the HSBS to aid in further definition of vibration limits. At

16,000 rpm, the peak amplitude was 200 Bm (8 mil) which indicates the limits

of 130 Bm (5 mil) established in the operator's manual are probably conservative since this power turbine had run acceptably in an engine.

The second high-speed balanced T55 power turbine (U00559) was engine tested at -zCCAD a month later. MTI personnel were not present during the test. The

engine was rejected for high vibration, predominantly on the V3 sensor which

is mounted on the waterbrake. CCAD personnel diagnosed the problems as a

faulty waterbrake. Unfortunately, the test was not rerun with an alternate

waterbrake. The test data from the run support the conclusion of a faulty

36
_m rail

250_ i0 _"

--- 4.J o 200

150 --

€_

--- 5

' • i00 -- r

_= _ A O 8

. _ _ 50 __ ,_ S I •

_ .,"__,._',. %' .>...,o",.,-°,

._ O_ 0 I !

o 5 io 15

Speed (i000 rpm)

a. Forward Vertical Probe

_m mil

..... As Installed (Previously High

- " _ 250 _ i0 - Speed Balanced at MTI)

o 200 _ m After High Speed Trim Balance

r

_ 150 m

"._ 5

IOO- [ _,

50

0 5 i0 15

'--" Speed (1000 rpm)

b. Aft Vertical Probe

Figure 18 Vibration Level in HSBS, Turbine End (T55 Serial No. 268922)

/

"-- 851521 37
Data From Standard Production Engine

m/see in./sec

.025 - 1.0 -

Data After Installation of High-Speed --

_ 0.9 _ Balanced Turbine

.02 _ 0.8 -- --

_ - o.7-

V 4

.015 - 0.6 -

.o

o

-- 0.5 --

o .01 - 0.4 - ___

0

_.. _ 0.3 --

J

- 0.i- C).... -

o- o I I I I I I

0 75 80 85 90 95 i00

% N1 Speed r --

Figure 19 T55 Overall Engine Vibration --

851522

38
100 --

•- m = Compressor Speed = 18,150 rpm

Turbine Speed = 15,600 rpm

O o

>

o I I I

6 12 18 24 _ 30 36 42 48 54 60

--_ Frequency (I000 cpm)

Figure 20 T55 Frequency Spectrum, S_rial No. 268922

841592

39
waterbrake. Even at the lowest power engine setting the V3 sensor has an

unacceptable level with all other sensors mounted on the engine reading very

low. At the higher speeds there is some transfer of energy to the V4 sensor

which is the closest engine sensor to the waterbrake.

3.3.2 Operations Manuals/Facility Repair Procedures

Four manuals and one set of engineering drawings are provided with the HSBS.

The manuals are:

• Operators Manual - describes the basic operational procedures for:

rotor installation and removal, high speed operation, computer operation, software user instructions and grinding instructions. Troubleshooting is outlined and maintenance intervals and spare parts are

identified.

• STstem Hardware Manual - detailed information on the computer and data

acquisition system, sufficient for skilled personnel to isolate

faults.

• Software Manual - detailed information on the system's computer

programs including listings of error messages and suggested corrective

action.

• Vendor Manual - data sheets and maintenance instructions for all vendor

supplied equipment.

3.4 Site Modification and Ri_ Installation

Subcontractors were assigned the task of preparing the former Test Cell 2B at

CCAD for use as a high-speed balancing facility. The preparations in the test

cell included the following items=

• preparation of floor mounting pads

• connections to adequate electrical, air and water supplies (included

installation of an isolation transformer)

• reassembly of all balancing equipment components

• establishment of electrical & mechanical interconnections between

components of the balancing system

• operational checkout of the entire system

Figure 21 details the layout of the hardware as installed in Test Cell 2B.

3.5 Vibration AnalTsis of Low and Hi_h-Speed-Balanced Power Turbines

This task involved checking and recording the HSBS-determined vibration characteristics of 20 T53 power turbines and 20 T55 power turbines. After operation in the HSBS, the power turbines were tracked through engine assembly and

vibration characteristics of the assembled engine in the test cell were

recorded and analyzed.

The power turbine modules of each type (T53 and T55) were divided into three

lots. The power turbines in the first and second lots were low-speed balanced __

prior to testing in the HSBS. The power turbines in the third lot were not

40
+__ +

Pump Control

TestCell 2B_ ...D_-R'-_m'_o

" Vacuum Chamber

_ ,, n--_-.---k_, 7

Regadyne__----T_ ,, ill /- I--

"-- acMoto.r F'__ _l"_'Llll -- -I---'-']

'_O"um---I°--_11;I

"_ Bearing I I _ i /I I III

Lubrication []1 I i .... ir

System _ _ , _ L._

-- Auxiliary_.t --Gearbox Controls

Water

._ __ f_..andAir | l J Scale_._ 1 in._..___ L CRT

-l_ Supply • Rega Drivedyne

- Controls Hoist 'I Pathof Computer

.- +-- _1 k

Figure 21 Layout of High Speed Balance Machine

841591

41
low-speed balanced. Lot i was tested in the HSBS but not high-speed balanced.

These modules provided a baseline correlation between shaft vibration as measured by HSBS sensors and engine case vibration as measured by test cell

sensors. The second and third lots of power turbines were high-speed balanced

and tracked in a similar manner.

The large number of rotors evaluated in their task afforded the opportunity to

use the HSBS to determine the influence of various power turbine parameters on

engine vibration. Examples of the parameters studied that will be discussed

in later sections include:

• dynamic imbalance between turbine stages

• spline fit variation

• low-speed balance results.

3.5.1 T55 Vibration Data from HSBS

The vibration data for all of the T55 power turbines tested in the HSBS is

presented in Table 3. The general trend of vibration amplitudes versus rotor

speed for the T55 power turbines was that of low amplitudes up to around

14,000 rpm followed by increasing levels up to the maximum speed of 16,000

rpm. All but one of the T55s was operated to its full speed in the asinstalled condition. The only exception was a Lot 3 rotor that showed high

amplitudes at 14,000 rpm. This agrees well with the analysis that predicts

the onset of rotor bending in the mode shape of the second critical speed as

the power turbine approaches it operating speed. Figure 22 represents a typical T55 amplitude versus speed plot. In all cases high speed balancing was --

effective in reducing the vibration levels at 16,000 rpm.

3.5.2 T53 Vibration Data from HSBS

The vibration data for all the T53 power turbines operated in the HSBS is

presented in Table 4. The vibration amplitudes for the T53s showed a much

higher variability than the levels measured for T55s. The low-speed balance

data was recorded for the turbines of Lot i and was found to be of no value in

predicting behavior in the HSBS. The vibration levels measured at 159500 rpm

in the HSBS for the Lot 1 turbines varied from 50 to 500 Bm (2 to 20 mil) whereas the low-speed balance results were very tightly grouped.

After determining that the low-speed balance results did not correlate with

the high-speed vibration levels, another explanation for the large variation

in the T§3 vibration levels was sought. Based on discussions with CCAD

personnel concerning multiple reject engines that had been problems in the

past, it was evident that the couple unbalance between the turbine stages of --

the T53 power turbine rotor was a potential cause of the high vibration levels

measured for some of the rotors. The current production procedure at CCAD

calls for a static balance on the third stage turbine, assembly of the third

and fourth stages and then a static balance on the fourth stage to balance the

assembly. This procedure can and does result in a large residual couple

between the stages with some rotors. The low-speed balance machines at CCAD

can measure the level of this 'dynamic unbalance' although it is not part of

the current production procedure. For the purposes of these tests, the levels

were checked for a group of 8 rotors. In addition, 3 of these rotors were

dynamically balanced (couple removed) and tested in the HSBS. The vibration

42 --
TABLE 3

T55 VIBRATION DATA IN THE HSBS

.... Amplitude Amplitude

As Installed After Balancing

Serial Lot Probe Speed Peak-to-Peak Peak-to-Peak

No. No. No. (rpm) (pm) (mil) (_m) (mil)

U00259 I 1 16,000 114 4.5

3 163 6.4

_ 5 71 2.8

U00212 I 1 16,000 107 4.2 No high-speed balancing

3 137 5.4 was conducted for Lot

• 5 53 2.1 No. i rotors.

268920 i 1 16,000 125 4.9

-_ 3 206 8.1

5 107 4.2

265530 I 1 16,000 117 4.6

3 188 7.4

5 94 3.7

_ - 261830 1 1 16,000 104 4.1

3 158 6.2

5 74 2.9

265539 1 1 16,000 53 2.1

3 89 3.5

5 38 1.5

95250 1 1 16,000 48 1.9

3 36 1.4

5 i0 0.4

265549 2 i 16,000 183 7.2 49 1.9

_- 3 287 11.3 74 2.9

5 130 5.1 43 1.7

U00433 2 1 16,000 91 3.6 ....

3 43 1.7 ....

5 23 0.9 ....

U00316 2 I 16,000 70 2.74 27 1.05

3 81 3.17 51 2.0

5 38 1.5 25 1.0

43
TABLE 3 (Cont'd)

Ampiirude Ampiirude r_

As Installed After Balancing

Serial Lot Probe Speed Peak-to-Peak Peak-to-Peak

No. No. No. (rpm) (_m) (mil) (_m) (mil)

U00589 2 1 16,000 142 5.6 104 4.1

3 218 8.6 140 5.5

5 99 3.9 69 2.1 --

268541 2 i 16,000 114 4.5 15 0.6

3 165 6.5 23 0.9

5 86 3.4 i0 0.4

268934 2 1 16,000 208 8.2 69 2.7

3 325 12.8 84 3.3

5 158 6.2 31 1.2

265566 2 I 16,000 158 6.2 61 2.4

3 239 9.4 91 3.6

5 102 4.0 48 1.9

U00295 2 i 16,000 274 10.8 51 2.7

3 429 16.9 140 5.5

5 211 8.3 64 2.5

268922 2 1 16,000 224 8.8 140 5.5

3 318 12.5 142 5.6

5 163 6.4 59 2.3

265499 3 i 16,000 58 2.3 ....

3 64 2.5 .... --

5 20 0.8 ....

U00559 3 1 16,000 64 2.5 ....

3 56 2.2 ....

5 31 1.2 ....

M265682 3 i 16,000 41 1.6 .....

3 56 2.2 ....

5 36 1.4 ....

M254954 3 1 16,000 130 5.1 74 2.9

3 165 6.5 86 3.4

5 71 2.8 36 1.4

265604 3 i 14,000 150 5.9 81 3.2

3 249 9.8 76 3.0

5 132 5.2 19 0.75

265604 3 1 16,000 .... 58 2.3

3 .... i09 4.3

5 .... 53 2.1

iM261845 3 1 16,000 99 3.9 18 0.7

3 152 6.0 31 1.2

5 76 3.0 18 0.7
_m rail

5 - Maximum

125 --

Speed = 16,000 rpm

i00 _ 4 -

75-- 3 -

= 50 2 -

4J

_-- 25-- i

o- o 1 I

0 3 6 9 12 15 18 21 24 27 30

.-- Speed (i000 rpm)

Figure22 T55 VibrationLevel in NSBS,TurbineEnd/Serlal_To.265530

851523

45
TABLE 4

T53 VIBRATION DATA IN THE HSBS

Amplitude Amplitude

As Installed After Balancing

Serial Lot Probe Speed Peak-to-Peak Peak-to-Peak

No. No. No. (rpm) (_m) (mil) (_m) (mil)

1896 1 1 17,200 145 5.7 I

3 254 i0.0

5 226 8.9

5247 i i 17,200 46 1.8 No high-speed

3 79 3.1 balancing was

5 53 2.1 conducted for

Lot No. I

rotors.

8873 1 I 21,000 53 2.1

3 25 1.0 --

5 25 1.0

1377 i i 15,500 173 6.8

3 180 7.1

5 152 6.0

5586 1 i 15,500 81 3.2 -_

3 165 6.5

5 234 9.2

U00278 i I 17,200 102 4.0

3 198 7.8

5 155 6.1

C9MI1244 1 1 17,200 152 6.0

3 132 5.2

5 102 4.0

2484 i i 15,500 104 4.1

3 61 2.4 ._

5 69 2.7

9925 1 1 17,200 53 2.1

3 74 2.9

5 86 3.4

1541 i 1 17,200 69 2.7

3 53 2.1

5 38 1.5

46
- TABLE4 (Cont'd)

Amplitude Amplitude

.--- As Installed After Balancing

Serial Lot Probe Speed Peak-to-Peak Peak-to-Peak

No. No. No. (rpm) (_m) (mil) (_m) (mil)

LE21788 2 i 15,500 76 2.99 49 1.91

3 86 3.4 37 1.47

5 119 4.7 32 1.26

M289659 2 i 15,500 94 3.7 81 3.2

3 66 2.6 53 2.1

- 5 81 3.2 i19 4.7

12956 2 1 17,200 142 5.6 17 .67

3 325 12.8 43 1.66

5 246 9.7 43 1.7

96441 2 i 15,500 61 2.4 33 1.3

3 76 3.0 38 1.5

5 76 3.0 25 1.0

-- P5132 2 1 17,200 107 4.2 41 1.6

3 295 11.6 38 1.5

5 285 11.2 69 2.7

3494 2 i 17,200 185 7.3 81 3.2

3 150 5.9 84 3.3

5 180 7.1 56 2.2

82C004 3 i 15,500 221 8.7 51 2.0

3 277 10.9 714 5.3

_- 5 259 10.2 122 4.8

82C012 3 1 15,500 150 5.9 84 3.3

3 191 7.5 66 2.6

_-_ 5 114 4.5 89 3.5

80K003P 3 I 15,500 218 8.6 69 2.7

-_ 3 274 10.8 56 2.2

5 226 8.9 36 1.4

4871 3 1 17,200 315 12.4 191 7.5

3 490 19.3 201 7.9

5 358 14.1 84 3.3

82C011 3 1 17,200 56 2.2

3 150 5.9

5 79 3.1
levels as measured by the HSBS for these 8 rotors correlated directly to the

dynamic unbalance levels measured by the CCAD low-speed balance machines.

This correlation was confirmed by the engine test results for the engines __

containing these power turbines. The engine test results are discussed in the

following section.

Dynamically balanced power turbine 8873 was operated to its maximum speed of -

21,000 rpm with extremely low vibration levels. A plot of the vibration data

from the turbine end probe for a run to 20,600 rpm is included as Figure 23.

The relatively constant low amplitude shown from 15,000 - 21,000 rpm is only

observed for dynamically balanced power turbines and the best of the

high-speed balanced turbines. The other two dynamically balanced T53 power

turbines, 1541 and 9925, were also tested to near 21,000 rpm. Spline shafts __

prevented the acquisition of data at 21,000 rpm. Plots of vibration amplitude

versus speed for rotors 1541 and 9925, operated in the HSBS are included as

Figures 24 and 25, respectively. The T53 turbine assemblies that were found

to have the highest level of couple imbalance were 12956 and 4871. The levels

for 12956 measured on the low'speed balance machine at CCAD were 15.4 gm in.

at 137 ° in the third stage turbine and 16.8 gm in. at 318 ° in the fourth

stage. The angles given are relative to a reference mark used by the operatot. Since the unbalance levels measured are very close to equal and opposite

(i.e. 180 ° phase difference) the assembled turbine stages meet the currently

used production balance specification. The resulting amplitude for the shaft _

center probe in the HSBS was 325 _m (12.8 mil) at 17,200 rpm and rising rapidly with increasing speed.

Rotor 4871 was an unusual case. The third stage turbine disk was brand new and

was not low speed balanced. The low-speed balance check indicated a dynamic

unbalance level of 133 gm cm (52.5 gm in.) at the third stage and 27 gm cm

(10.5 gm in.) at the fourth stage. The static check which is the only one

used in the current procedure yields the difference between the two vectors,

98 gm cm (38.5 gm in.). The resulting amplitudes for the shaft center probe

in the HSBS was 490 _m (19.3 mil) at 17,200 and also rising rapidly.

The high-speed balancing of the T53 power turbine was successful in reducing

amplitudes for each rotor, although much more difficult than the T55 balancing. The sensitivity to the dynamic unbalance along with problems with spline

shifts cause the extra difficulty. The T55 turbine disks are dynamically

balanced. For the T53 power turbines with any significant third stage balance

(only encountered in new parts rotors, Lot 3) the high-speed balance quality

is compromised due to the unavailability of the third stage as a correction

plane. Therefore, any correction to compensate for the third stage unbalance

must be installed on the fourth stage introducing a couple.

The balancing software was effective in reducing the amplitude for these

worst-case rotors but was not capable of producing the low-amplitude levels

reached by eliminating the dynamic unbalance directly. The high-speed balancing of the T53 rotors in Lot 2 and those in Lot 3 that did not contain new

parts was very successful and resulted in smoother running T53 engines.

3.5.3 T53 Engine Test Cell Data

The T53 engine is instrumented with three case-mounted sensors when operated

in the engine test cell. The engine is set at specific test points that are

48
_m rail

250- i0-

m

Maximum

._ Speed = 20,600 rpm

50-

O -. I I I I I I I I I

3 6 9 12 15 18 21 24 27 30

Speed (i000rpm)

Figure23. T53 VibrationLevelin HSBS,TurbineEnd/SerlalNo. 8873

i

" 49

%
_m (mil)

250- io I i i I I J i

200 -

Max. Speed = 18,400 m

150 -

i00 -

m

50 - -

u

o- a I i i l I I J I i i0 3 6 9 12 15 18 21 24 27 30

Speed (i000 rpm)

Figure 24 T53 Vibration Level in HSBS, Turbine End/Serlal No. 1541

|

50
IJm rail

---- 250 - 10 I I I I I I I I i

!

200 - -

• Maximum

- . Speed = 20,500 rpm B

150 -- -

o 5-

_ -

= i00 - - V m

m

o- o _ ._ t I t I t

0 3 6 9 12 15 18 21 24 27 30

Speed (i000 rpm)

Figure 25 T53 VibrationLevel in HSBS, Turbine End/SerlalNo. 9925

51
defined by the two rotor speeds (power turbine rotor and compressor rotor) and

the overall vibration reading from each sensor recorded and compared to a

specified limit. The term, overall vibration, refers to the total case

vibration that is made up of the sum of all the various components at different frequencies. The overall vibration will therefore include numerous components at discrete frequencies such as: a contribution at the power turbine --

freuqency, a contribution from the compressor rotor, contributions from any of

the engine auxilliaries running off one of the main rotors, and a contribution

from the test cell waterbrake, among others. Table 5 presents the overall

vibration reading from the test cell sensor on the turbine end of the engine

(V3) for all of the T53 engines tested. This sensor is the most sensitive to

the power turbine vibration. The T53 engine test cell data is characterized

by a dominant power turbine frequency that makes up a large percentage of the

overall vibration for most of the engines tested. For this reason, changes in

the T53 power turbine balance show up clearly as changes in overall engine

vibration. A frequency spectrum plot for each T53 engine tested appears in

Appendix A. The plots are a breakdown of the overall vibration signal from

the V3 sensor into its various frequency peaks, taken from the vibration test

point with the power turbine operating at 100% speed (_21,000 rpm). The measured overall vibration at the test point is included on each plot.

The objective of running the Lot i power turbines was twofold. First, it

determined if a correlation exists between the levels measured in the HSBS and --

the vibration resulting from the power turbine in the assembled engine.

Second, it determined what levels in the HSBS would result in acceptable

engine vibration levels. An acceptable engine is determined by the vibration

specification listed in the DMWR; for the V3 sensor on the T53, the allowable

limit is 81 _m (3.2 mil) above 85% power turbine speed and is determined by a

curve for the lower speeds. The HSBS data showed the worst levels of Lot 1 for

power turbine 1896 and the best levels for turbine 8873. The engine test

results agreed with the HSBS results; turbine 1896 was very near to being a

vibration reject with a peak level of 94 _m (3.7 mil) at the 80/80 check

point. On the other hand, turbine 8873, which had been run to 21,000 in the _"

HSBS, showed a peak level of only 41Bm (1.6 mil). The correlation between

HSBS levels and engine test results was confirmed by the T53 turbines from

Lots 2 and 3. The dynamically balanced power turbines (8873, 1541, 9925) all --

showed very low vibration levels in the HSBS and resulted in exceptionally

smooth running engines. Power turbines P5132 and LE2178 were the best of the

high speed balanced power turbines and also resulted in very smooth engines.

The peak vibration levels for these two engines were 23 and 33 Bm (.9 and 1.3

mil), respectively.

The T53 power turbines that resulted in the worst running engines were 1896,

5586, 80K03P, 82C012, and 4871. As previously mentioned, 1896 was the roughest running Lot 1 power turbine in the HSBS and power turbine 5586 was the

second worst Lot i rotor. The other three power turbine rotors are Lot 3

rotors that were tested as examples of the worst case non-low-speed-balanced

turbines that could possibly occur in the overhaul cycle. This required the

use of completely new turbine disks and blades that had not been low-speed

balanced. The three power turbines were assembled with three different angular orientations of the two turbine disk's imbalances. That is, the heavy

area of the two disks was in line in one case, 180 ° and 90 ° apart in the other

two cases. This was done to thoroughly test the ability of the HSBS to handle

actual nonbalanced parts. The other Lot 3 rotors tested were

52
• %

TABLE 5

T53 ENGINE TEST CELL DATA, V4 SENSOR

Power _rblne Speed - N1Z/g2Z

Serial g_ber 75175 80/80 85/97 90195 90197 911100 95/97 100197

mil 2.0 1.8 1.2 i.i .1 0.9 1.1 1.5

4871 wm _JECTED AT ID_

mi_

_21788 _m 33 23 13 18 18 18 20 23

mil 1.3 0.9 0.5 0.7 0.7 0.7 0.8 0.9

M289659 um 53 76 74 71 71 -- --

miL 2.1 3.0 2.9 2.8 2.8 -- -- --

_-- 1541 Um i0 10 118 18 18 18 15 20

miL 0.4 0.4 0.7 0.7 0.7 0.7 0.6 0.8

82C012 ummil 843.3 793.1 26.45 793.1 72.9 4 692.7 692.7 742.9

82C004 _m 53 89 64 79 54 53 74 --

miL 2.1 3.5 2.5 3.1 2.5 2.1 2.9 --

--_ 80[03P _m 61 99 64 53 53 48 -- --

mil 2.4 3.9 2.5 2.1 2.1 1.9 2.3 2.1

U00278 um 23 25 15 15 15 13 20 15

_._ mi_ 0.9 1.0 0.6 0.6 0.6 0.5 0.8 0.6

C9Hl12_ Um 43 28 23 18 23 23 23 33

miL 1.7 1.1 0.9 0.7 0.9 0.9 0.9 L.3

9925 um 41 22 10 10 8 8 13 10

miL 1.6 0.9 0.4 0.4 0.3 0.3 0.5 0.4

2_A Um 36 41 33 31 33 38 38 38

miL 1.4 1.6 1.3 1.2 1.3 1.5 1.5 L.5

P5132 .m 23 18 18 18 18 18 18 18

miL 0.9 0.7 0.7 0.7 0.7 0.7 0.7 0.7

--_ 96_1 Um 25 64 41 41 41 41 41 --

mil 1.0 2.5 1.6 1.6 1.6 1.6 1.6 --

12956 um 56 _ 43 36 33 20 46 56

miL 2.2 1.9 1.7 1.4 1.3 0.8 1.8 2.2

1896 um 84 94 38 41 43 43 33 --

miL 3.3 3.7 1.5 1.6 1.7 1.7 1.3 --

+_- 5247 um 74 25 33 25 33 36 38 23

mil 2.9 1.0 1.3 1.0 1.3 1.4 1.5 0.9

8873 um 41 33 36 33 31 31 36 --

mil 1.6 1.3 1.4 1.3 1.2 1.2 1.4 --

1377 um 53 28 28 23 28 28 28 53

miL 2.1 1.1 1.1 0.9 1.1 1.1 1.1 2.1

5586 _ 53 81' 18 15 15 15 15 18

miL 2.1 3.2 0.7 0.6 0.6 0.6 0.6 0.7
non-low-speed-balanced as far as that particular overhaul was concerned.

Since the rotors had been low speed balanced at one point they were only

slightly out of the balance specification. This latter case involving the

non-low-speed balanced rotor represents the typical rotor that is found in the

overhaul cycle. The high-speed balancing of the three rotors involving new

turbine disks was difficult due to the excessive unbalance at the inaccessible --

third stage disk. Power turbine 4871 had a third stage disk that was

132 gm cm (52 gm in.) out of balance. The initial run of this power turbine

in the HSBS was characterized by very large vibration amplitudes measured at

the lowest balance speed, i000 _m (40°mil) at 2750 rpm, as well as high levels

at the top balance speed, 482.6 _m (19 mil) at 17,200 rpm. The balance calculation based on this run gave correction weights too large to be ground in the

rotor. Using the rebalance option in the balancing program to calculate

correction weights based on only the upper balance speeds resulted in a more

practical correction weight set. Installing this weight set in the form of

temporary weights reduced the 483 _m (19 mil) amplitude at 17,200 rpm to

201 _m (7.9 mil) but did not affect the peak at 3200 rpm. These weights were

therefore ground in the rotor on the assumption that the engine would not see

any effect from the 3200 rpm peak due to the rapid acceleration through this

speed. The engine test results refuted this assumption, as the engine

rejected at idle and was not accelerated to any of the vibration check points.

This test clearly demonstrated the need to retain the 2750 rpm balance speed.

The other two power turbines containing new parts that had not been low speed

balanced were 80K003P and 82C012. Both of these power turbines were successfully high speed balanced up to 15,500 rpm using the same balance plan as the

Lot 2 rotors. After the engine test results were reviewed, the unbalance

levels measured for these rotors were simulated by the addition of weights to

a well-balanced rotor to allow further testing in the HSBS. The tests indi- -

cared that for the case of a large unbalance installed on the third stage

turbine the amplitudes increased much more sharply between 15,500 and

17,200 rpm than the Lot 2 rotors. Balancing the Lot 2 rotors to a top speed of

15,500 rpm had worked well and eliminated the recurrent spline shift problems.

The increase in vibration between these two balance speeds demonstrated for

the extreme Lot 3 imbalance levels explains why the engine test levels were

higher than the HSBS results would indicate. High speed balancing up to

17,200 rpm would have improved the engine test results but would not match the

low levels of the dynamic balanced rotors due to the known imbalance at the

inaccessible third stage turbine balance plane.

During the period of MTI's testing at CCAD, a total of 151 T53 engines were run

in the test cells out of which twenty failed for high vibration at sensor

number 3 (the sensor most indicative of power turbine imbalance). Of the °-

twenty failures, eighteen were corrected by dynamically balancing the power

turbine, after which all eighteen passed testing with levels of 1.0 mil or

less in the succeeding run. The other two were checked "by the book", i.e.,

static balanced, reassembled, and retested with the same poor results -

rejection because of high vibration. They were then dynamically balanced and

passed engine testing with exceptionally low levels.

It was a common occurrence a few years ago at CCAD to have engines rejected

five to ten times in a row for this same reason. It is probable that the twenty rejects in this group would have resulted in a hundred or more wasted

engine tests had they not been dynamically balanced. Unfortunately, a request

54
to change the balancing procedure was turned down; the following reasons were

cited:

• The number of engines failing test is too small

• The cost to change the procedure would probably exceed savings that

•_ would result.

Not only would the proposed change in procedure have eliminated the twenty

rejects and the multiple time rejects, but also the decrease in overall engine

vibration for all T53 engines would have extended the life of numerous engine

components and provided the aircraft's crew a less fatiguing environment.

3.5.4 T55 Engine Test Results

Table 6 presents the engine test results from the twenty T55 engines tested.

:_ The data was obtained from the V4 sensor which is the hot section sensor

equivalent to the V3 sensor discussed for T53 engines. The vibration limit

for this sensor is .024 m/s (.94 in./sec). Generally the T55 engine test data

_-- is characterized by a large contribution to the overall vibration from the

compressor rotor. Both the HSBS data and the test cell data indicates that

CCAD's current T55 power turbine production balancing procedure yields smooth

running power turbines. All Lot 1 power turbines were operated to the full

speed of 16,000 rpm in the HSBS and all resulted in acceptable engines.

Appendix B includes the frequency spectrum plots for each of the engines,

operating at the 90/100 vibration check point.

The three smoothest running T55 engines tested were those containing power

turbines 95250, M261845 and U00316. All of these engines during the engine

test had a peak value of .0150 m/s (.6 in./sec) or less. Power turbine 95250

was the smoothest running Lot I rotor tested in the HSBS with a peak vibration

reading of 48 Bm (1.9 mil) at 16,000 rpm. Power turbine M261845, a

non-low-speed-balanced unit (Lot 3), was the most successful high speed

balance with a peak reading of 30 _m (1.2 mil) at 16,000 rpm in the HSBS.

Turbine U00316 was a high speed balanced unit from Lot 2 that exhibited a peak

vibration in the HSBS of 51Bm (2.0 mil) at 16,000 rpm. All of the Lot 2

turbines resulted in acceptable engines.

Of the five T55 engines that exhibited the highest vibration levels in the

engine test cell, 265530 and U00259 were two of the roughest Lot i power

.... turbines tested in the HSBS. Power turbine serial number U00295 was the least

successful high-speed balanced turbine from Lot 2. The final peak amplitude

in the HSBS was 140 _m (5.5 mil), a level slightly below the levels recorded

_ for the two Lot i rotors previously discussed. These three rotors help establish the maximum allowable vibration specification for high-speed-balanced

T55 power turbines. The other two power turbines involved in the five engines

.... with the highest vibration levels were Lot 2 rotors. In each case, the

compressor rotor contributed more to overall vibration than the power turbine.

3.5.5 T55 Gas Producer Balance

The original intent of the vibration analysis was to evaluate the power

turbines in the HSBS, in the engine test cell, and in the aircraft. The

-- aircraft tests were found to be unworkable for the overhaul center; additionally, verification of the test cell results had already been done. It was

55
TABLE 6

T55 ENGINE TEST CELL DATA, V3 SENSOR

IPower i Speed - N1Z/N2Z ITurbinei

ISeria_

tgumber 75/95 80/94 85/95 89.7/90 89.7/9_.5 89.7/L00 93/102 9_/9_

_65499;iinm//sec s 1l.0.0375 .007 .3 5 ..50125 [ .01 .525 ii ..015 25 .012 .5 5 j .012 .5 5 1..0175 7 1

i i i

952501 m/s _.0050 .0100 .0100 .0100 i .0100 .0100 .0150 1.0150

lin/secl.2 .4 ._ "_ I .4 .4 , .6 .6

u00316 i =i, . 075 .0075.01000.100 .moo .0125!.0150!.0150

!in/sec:.- .3 I .4 i .4 .4 .5 ! .6 .6

265539 m/s .0125 . 125 .0125 .0125 .0175 .0125 .0175 .0175

in/see • • .5 .5 .7 .5 .7 .7

U00589 m/s .0125 I .0125 .0125 .0125 .0125 .0125 .0175

i

in/see .5 ! .5 .5 .5 .5 .5 .7 .7

t i

2656041 m/s .0200 .0225 i .0200 .0150 .0175 .022§ .0275 .0250

lin/sec .8 .9 ! .8 .6 .7 .9 1.1 !1.0

.0075 . 075 . 075 .0125 . 125 .0125 ;.0175

in/secl.3 .3 [ " " .5 . .5 1.7

.0175 I

268541'I, =is "0125 "017§ i "017 .7 § .7 .7"0175 .01 .025755,.7 .0225 9 1.9 i

in/=ec .5 .7 I I '

l

2655661 mls .0175 .0175 I .0175 .0175 .0175 .0225 I .0225 .0225

I_./,e=+7 .7 1.7 .7 .7 .9 I 9 9 I

uoo29=5i, i

125 .0125 .017§ .0175 .0175 .0225 .0225 .0225 --_

in/sec .5 .7 .7 ! .7 .9 .9 .9

++1in/+' see °°

.1 +1°°.i + °.5 +°°.3 +. . °=.7 I __

2655491 m/s .0075 .0125 I .0125 .0125 .0125 .0125 .0125 .0175

_65682 =/s [.0075 .0075 .0075 .0125 .0125 .0125 .0175 .0175

in/see:.. " .3 .3 .5 .5 .5 .7 |.7 ,

_61845 m/s .0075 .0125 .0125 .0125 .0125 .0125 .0125 .0125

in/see .3 .5 .5 .§ .5 L .5 .5 .5 _

254954 m/s .0100 .0100 .0150 I .0150 .0100 .01501

inlsec!.2 .4 .4 .4 .6 1 .6 .4 .6

I

U00259 ; ' ,

mls .0075 j .0100 .0125 .0150 i .0150 • 150 .0225 .02001

in/see .3 .4 .5 .6 l _ - . .9 .8 ;

265530 m/s .0150 I .0150 .0225 .0175 ! .0175 .0175 .0225 .0225

ln/sec:.6 .6 .9 .7 I .7 .7 .9 .9

2618301 m/s !.0050 I .0050 .0050 .0075 .0075 .0100 .0125 .0125:

lin/secl.2 .2 .2 .3 .3 .4 .5 .5

268934J m/s 1.0100 I .0100 .0100 .0100 .0100 .0100 .0125 1.0125

]in/secL.4 i .4 .4 .4 .4 .4 .5 ,.5

U00212[ =1' i i i

tin/see= :

56
the opinion of depot personnel that if an improvement in vibration levels was

demonstrated in the engine test ceil, the correlation to improved airframe

-- vibration was established. For these reasons, the effort planned for the

airframe tests was refocused to investigate the reason for the large contribution from the T55 compressor rotor to the overall level of engine vibration.

-- CCAD personnel were interested in a possible correlation between high

vibration attributed to the compressor and the dynamic imbalance between the

gas producer stages of the compressor rotor. The reason for the interest was

the similarity between the gas producer (size and bearing configuration) and

the T53 power turbine stages which had been conclusively shown to have a

strong effect on engine vibration, if dynamically out of balance.'

Seven compressor rotors were studied and readings recorded using CCAD

low-speed balance machines. The dynamic imbalance measurements for the gas

producers of these seven compressor rotors is presented in Table 7. Using the

frequency spectrum plots to compare the magnitude of vibration at the c_mpressot frequency (for each of the seven engines), it is evident that the magnitude does not follow the level of dynamic imbalance recorded. This is

illustrated by comparing Figures 26 and 27, the spectrum plots for engine

sequence numbers 843-3005 and 843-2027. The corresponding dynamic imbalance

recorded for the gas producers of these two engines is 14.7 gm-cm (5.8 gm in.)

and I0.7 gm-cm (4.2 gm in.) for 843-3005 and 83.8 gm-cm (33 gm in.) and

71.1 gm-cm (28 gm in.) for sequence number 843-2027. The spectrum analysis

plot for 843-2027 shows a significantly lower peak at the compressor frequency

than the engine with the low level of dynamic imbalance on the gas producer.

It is clear from these results that the cause of the vibration of the compressor rotor is imbalance located along the rotor and not dynamic imbalance of

the gas producer stages.

57
TABLE 7

T55 GAS PRODUCER LOW-SPEED BALANCE CHECK

T55 Engine Power Turbine

Sequence No. Serial No. Gas Producer Imbalance

841-3004 U00433 ist stage 22.9 gm-cm 9 gm-in. @ 143°

2nd stage 25.4 gm-cm i0 gm-in. @ 302°

841-3006 265549 ist stage 23.6 gm-cm 9.3 gm-in. @ 152°

2nd stage 19.1 gm-cm 7.5 gm-in. @ 355 ° --

841-3007 265604 Ist stage 10.2 gm-cm 4.0 gm-in. @ 306°

2nd stage 7.1 gm-cm 2.8 gm-in. @ 184°

843-3005 H265682 ist stage 14.7 gm-cm 5.8 gm-in. @ 75°

2nd stage 10.7 gm-cm 4.2 gm-in. @ 298°

843-3007 H261845 ist stage 31.8 gm-cm 12.5 gm-in. @ 42 °

2nd stage 41.9 gm-cm 16.5 gm-in. @ 232 °

843-3001 268934 1st stage 30.5 gm-cm 12 gm-in. @ 140 °

2nd stage 43.2 gm-cm 17 gm-in. @ 316°

843-2027 H265499 1st stage 83.8 gm-cm 33 gm-in. @ 64 °

2nd stage 71.1 gm-cm 28 gm-in. @ 247 °

58
I I I I el I I I I

_ i00_- Engine Sequence No. 843-3005

Gas Producer Imbalance

90 - ist Stage 5.8 gm-in. @ 75°

2nd Stage 4.2 gm-ln. @ 298 °

80 _

70 _ ._

e_

>

60 ....

= Compressor

= _O - Frequency _ _

om 40

m Power Turbine

Frequency __

> 30

20

3 6 9 12 15 18 21 24 27 30

Frequency (i000 cpm)

Figure 26 T55 Engine Test Cell Data - Frequency Spectrum

59
Ioo I I I I I I I I I

90_ Engine Sequence No. 843-2027 -

Gas Producer Imbalance __

_'_ 80- 1st Stage 33 gm-in. @ 64 ° --

2nd Stage 28 gm-ln. @ 247 °

e_

70-

V _

= 60-

50--

o

m Compressor =

40-- Frequency

>

30--

Power Turbine

Frequency

6 12 18 24 30 36 42 48 54

Frequency (I000 cpm)

Figure 27 T55 Engine Test Cell Data - Frequency Spectrum

60
4.0 CONCLUSIONSAND RECOMMENDATIONS

4•1 Conclusions

The multiplane multispeed balancing system designed and constructed under

this program was successfully demonstrated on production hardware in the overhaul center at CCAD. Test data taken for twenty T53 power turbines and twenty

T55 power turbines demonstrated a direct correlation between the vibration

-- level of the power turbines when tested in the HSBS and when operating in an

assembled engine. High speed balancing successfully reduced the vibration

levels measured by the HSBS forall turbines balanced.

The testing of T53 power turbines balanced by the current production procedure

(not high speed balanced) revealed a wide range of HSBS/engine vibration

levels. The T53 vibration levels were found to correlate directly with the

magnitude of the dynamic imbalance between the two turbine stages. The

by-the-book current production/overhaul procedures do not allow for any check

of the dynamic imbalance level, and until recently it was not an uncommon

occurrence for the same engine to be rejected as many as ten times. Therefore_ some not-by-the-book checking was done in an effort to determine the

reason for the large number of engines rejected for high vibration. Over a

one-year period, the CCAD balance shop determined that the cause of rejection

for 19 out of 20 high-vibration rejects was dynamic imbalance. Correcting the

dynamic imbalance of the power turbines from rejected engines has resulted in

smooth running engines, in all cases, on the second engine test.

Dynamically balanced T53 power turbines tested in the HSBS resulted in exceptionally low vibration levels. The engines containing these power turbines

were also exceptionally smooth running. High speed operation of the power

turbines in the HSBS also served as a proof test of the turbine module. In two

cases_ power turbines with problems were identified in the HSBS prior to

engine assembly.

The T55 power turbines balanced with the current production procedure and

tested in the HSBS showed much less variation in vibration levels than the T53

turbines. The corresponding T55 engines showed acceptable levels of vibration

attributable to the power turbine. The dominant frequency contributing to the

overall vibration of the T55 engines is generally the compressor rotor

frequency. Tests were conducted to determine if the dynamic imbalance of the

T55 gas generator turbine stages, which bolt onto the compressor rotor_ were

the cause of the large contribution from the compressor rotor. No correlation

was observed between the gas generator dynamic imbalance and compressor rotor

-- vibration levels.

The successful development o£ high speed balancing techniques provides the

-- overhaul center with a capability that will enable them to handle the increasing flexible rotor designs incorporated in the modern, lightweight, high

horsepower engine such as the TT00.

4.2 Recommendations

The current T55 power turbine balancing procedure is adequate. Implementation

of high speed balancing is not recommended for this rotor.

61
The current T53 power turbine balance procedure is unacceptable. Implementation of dynamic balancing of the turbine stages would result in a reduction in

the average engine vibration level by a factor of two and would virtually

eliminate vibration rejects. Because of the ease of implementation of dynamic

balancing, high Speed balancing is not recommended for T53 power turbines.

The continuing development of automated material removal techniques such as

laser balancing is essential to the continuing development of precision, high

speed balancing. The effectiveness of high speed balancing is dependant on

the accurate removal of the required balance correction.

Analysis of engine test cell vibration data is needed at CCAD. Currently,

personnel at the overhaul center have only the overall vibration level on

which to base a decision as to the appropriate corrective action for a

vibration reject. The overall vibration reading is a summation of the

vibration components at discrete frequencies. For this reason, a vibration

reject may be due to a large contribution from the waterbrake or from a system

auxiliary or other problems that could be addressed directly rather than

checking all major engine components before retesting. CCAD has the necessary

equipment to do frequency spectrum analysis, although it has not been used

since being purchased. Putting this hardware to use would provide CCAD engineering personnel with the data required to minimize the rework involved in

handling vibration rejects of all engine types.

62
APPENDIX A

T53 ENGINE SPECTRUM PLOTS

63
I
} ) 11 1 1 1 1 1 1 ! 1 } ) 1 1 } 1 )

I I. I I I

too , , , , , I I I I

90 - Compressor Speed = 22,640 m m

Turbine Speed = 21,160

80 --

70,-

m

60 _

4J

50 -

0 _

0

40

_?.

30 -

20 - m

o

0 6 I2 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

o_ F%gure A_I T53 Power Turbine, Serial No. 1896

Ln
_, loo I I I I i I I I I

90 -- - Compressor Speed = 22,640 - -

Turblne Speed = 21,160

2O

10

t

o

o _ _ I ,' ' _1 I I I I I

0 6 12 18 24 30 36 42 48 54 60

Frequency (I009 rpm)

Figure A-2 T53 Power Turblne, Serlal No. 5247

J

I I 1 I I 1 1 1 I I I I I ! i i
I 1 ' ! 5 1 ! ! 1 I 1 1 ) ! ! ! ! 1

I

lOO I. I I ' I , I I ....t I-.............

90-- Compressor Speed ffi 22,640 _..

Turbine Speed = 21,160

80 _ _ _

m 70 .....

_ 60 .....

u

50.....

kl

0

U)

40 ...... r._

>

30 .....

0 _ _ _

o I I t I t I !............t............. I............

0 6 12 l_Z 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure A_3 T53 Power Turbine, Serial No. U12956
' I I I I I I

lOO I I ,

Compressor Speed = 22,640

90 _ Turbine Speed = 21,160

80--

m

70--

60--

4.1 M

50--

o

4o--

>

30_ m

0 _ _

10

I I

o I I , ,

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure A-4 T53 Power Turhlne, Serial No, 96441

I J I 1 ! 1 1 1 I 1 } } I } } i
1 1 ! ! 1 1 1 1 1 1 ). 1 1 ) I 1

I i !

lOO I I I , I , , I I

Compressor Speed = 22,640

90_

Turbine Speed = 21,160 --

"_ 70--

60--

42

4J

50-- ----

o

40-'-

c_

>

30-- --

20--

10_- !

i

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure A_5 T53 Power Turbine, Serial No 8873
100 I I I I I I I I I

0

Compressor Speed = 22,640

90_ Turbine Speed = 21,160 --"

m

w 70--

ow.

60

n

v

50--

o

0

tn

40-- --

o_

30--

.m

0 1 I ! I t

O 6 12 18 24 30 36 42 48 54 60

Freouenev (1000 rpm)

Figure A-6 T53 Power Turbine, Serial No. 1377
} ! ! ! 1 ! ! ! } 1 I 1 1 ! ) ) 1 1

loo ._..........I...........I............I............i.................. I...........I............i......... I............I...............

Compressor Speed = 22,640

90-- Turbine Speed = 21,160 --

70--

to

e_

60-- m

4J

50-- --

0

o

to

4o-- --

i

i

30 -s20-_-

lo__ ! -

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure A-7 T53 Power Turbine, Serial No. 5586
loo I I I I I I I I I

Compressor Speed ffi 22,640

90- Turbine Speed ffi 21,160 --

m

80--

o I I I I I I I I I

0 6 12 18 24 30 36 42 49 54 60

Freauency (I000 rpm)

Figure:A_8 T53 Power Turbine, Serial No. U00278
1 1 1 _ 1 1 ] } 1 1 ] ] I 1 ) I

loo I I I I I I I I I

Compressor.Spe_= 22,640

90-- Turbine Speed = 21,160 i_

80 w _

70-- m

60-- -- v

4J

4J

50-- m

o

tQ

4o--

>

30I

20-- "-J10--

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure A-9 T53 Power Turbine, Serial No. C9MI1244
10o I '

, I I ', I I I I

Compressor Speed = 22,640

90-- Turbine Speed m 21.160 --

0_ - m

70-- m

_60_ m

m

,J

50-- m

o

40-- m

30 ....

o I t I _ t I I

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure A-10 T53 Power Turbine, Serial No, 2484
1 ! i I ] ] 1 ! ] ] ] I I I } }

100 ! I I . !

, , , , I I I I I

90__ Compressor Speed = 22,640

Turbine Speed = 21,160

80_.

70- tQ

60--- m

4J

5o__

o

40--

20--

m

IO--

o _'_/I , , , , , , I I

I I I I I I

O 6 12 18 24 30 36 42 48 54 60

Frequency(I000rpm)

'F_gureA-II T53 PowerTurhlne_SerialNo_ 9925
100 I I l l l l i l I

o_

90__ Compressor Speed = 22,640

! Turbine Speed = 21,160

0- - m

i0

o_ l I l I l i i I l

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure A-12 T53 Power Turbine, Serial No. 15029

I I 1 1 I I ! 1 i I I I 1 I
lOO { I { { I I { { {

90--- Compressor Speed = 22,640

Turbine Speed = 21,160

._ 70-- m

o_

60-- --- v

50---

o

o

40--

o_

>

30---

20--- _

10_ _

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure A-13 T53 Power Turbine, Serial No. 21788
., lOO I I I ' I I I I I I

Compressor Speed = 22,640

90 ....

Turbine Speed _ 21,160

0- - _

lo-- o I I I I I I

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure:A-14 T53 Power Turbine, Serial No. 289659

I I I I I ] I I ] ] I ] I ] , I I i
{ { I I I I I } ) { { I } { )

_oo { { { { { { { l {

90--- Compressor Speed = 22,640

Turbine Speed = 21.160

80---

_- 70---

{0

60--- --

= 50---

O

o

{/l

= .40- -

aJ

>

30--

20_ _ _

| . _ L

| " ,

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

Figure A-15 T53 Power Turbine, Serial No. P5132
Co 5o I I I I I I I I I

O

Compressor Speed = 22,640 m n

Turbine Speed = 21,160

m

i0 -

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure A-16 T53 Power Turbine, Serial No. 82C004
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

I I

50 I I , I t t t , I

Compressor Speed = 22,640 m

Turbine Speed ffi21.160

0

0 6 12 18 24 30 36 42 48 54 60

Freauencv (1000 rpm)

Figure A-17 T53 Power Turbine, Serial No. 82C012
1oo I I I I I I I I I

oo

90--- Compressor Speed = 22,640

Turbine Speed = 21,160

0u _ a m

"_ 70-- m

_ 60-- _

=

50--

o

o

40 ....

03

>

30--

20-- _ --

i0--

oJw'a i

0 6 12 18 24 30 36 42 48 54 60

Frea.enev (10C0 rpm)

Figure A-18 T53 Power Turbine, Serial No. 80KO03P

I I ] I I ] 1 I ] ] I ] I ] ] ! I I ]
APPENDIX B

T55 ENGINE SPECTRUM PLOTS

83

! } I 1 1 1 / } I ] 1 I ) I 1 I I

loo I I ' I I I I I I I

90- - Turbine Speed _ 15,600 rpm --

Compressor Speed _ 17,250 rpm

80- -

70--- m m O_

6o--

4..t

50--

o

14

0

4o-- qm

u_

>

30--

10

o ! I

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

Figure B-I T55 Power Turbine, Serial No. 265499
lOO I I i I I I I I I

90- " Turbine Speed - 15,600 rpm - -

_mpressor Speed = 17,250 rpm

80- -

0 I

I

0 6 12 18 24 30 36 42 48 _6 6Q

Frequency (1000 rpm)

Flgure B-2 T55 Power Turbfne, Serial No. 95259

1 l I I } I I i I 1 1 1 } i I I I
] ! ! ! ! ! ] } 1 ] 1 t ! } ! 1

loo I I I I I I I I I

Turbine Speed = 15,600 rpm

90 -

Compressor Speed = 17,250 rpm

0m m w

u_

70-- m

60-- m

4-I

o 50 ....

0

u_ 4o__

>

30_

20 m

lO

o I t t t t t

0 6 12 18 24 30 36 42 48 54 60

Frequency _lO00 rpm)

Figure B-3 T55 Power Turbine, Serial No. U00316
= lOO I I ' I I I I I I I

co

90--- Turbine Speed = 15,600 rpm

Compressor Speed = 17,250 rpm

Irk_ _ m

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

Figure B-4 T55 Power Turbine, Serial No. 265539

I 1 i 1 I I i I ! 1 I I i J J i J i
I00 I m, . I I I I I I I

90-- Turbine Speed = 15,600 rpm - -

Compressor Speed - 17,250 rpm

lm

m 70---

,_ 60--- _

iJ

o 50 .... o

1,4

O

m

rm_ 40--

cq

30---

20 m m

10

I

0 I

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

m Figure B-5 T55 Power Turbine, Serial No. U00589
loo I I I I I I I I I

0

90-- Turbine Speed = 15,600 rpm --

Compressor Speed - 17,250 rpm

u

80--

J'_ m

70--

v 60_ ---

50--- -- (:3

I..i

o

4o--

>

30--

o I I

0 6 12 18 24 30 36 42 48 54 60

Frequency (lO00 rpm)

Figure B-6 T55 Power Turbine, Serial No. 265604
1 1 1 I ' ! ! ! ! I 1 / 1 / l; I I 1

I I l

lOO , , , | F _ t t 1

90-- Turbine Speed = 15,600 rpm m

Compressor Speed = 17,250 rpm

80- -

70-- m

v 60--

4_

so-- --

o

40-- m

>

30m

20.-- li

I,:

,o ,J o ,--.....• --_ ,,,

' - , I : t t -1 ' I ,

I I

O 6 _ 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure K-7 T55 Power Turbine, Serial No. 268922
Ioo I I I I i I I I I

I,a

90_ Turbine Speed = 15,600 rpm --

Compressor Speed = 17,250 rpm

m D

70-- m

v 60-- m

4J

4_

o 50---

ta

O

O]

40-- --

>

30-- m

0__ _

o 'I 'I t | t

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

Figure B-8 T55 Power Turbine, Serial No. 268541

] I J J 1 I 1 I I I } 1 I I i 1
1 ! ! ) I 1 1 ', _ I 1 I I _ 1 1 1 i

loo I I I I I I I I I

Turbine Speed = 15,600 rpm

90 ....

Compressor Speed = 17,250 rpm

0 _ -

o I

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

_ Figure B.-9 T55 Power Turbine, Serial No. 265566
,_ 10o .... _ I I t t t I I t

Turbine Speed = 15,600 rpm

90-- 1 Compressor Speed = 17,250 rpm

80-- [ --

y

g,o__, I

llJ ..

o 50-- t w

o

40-- i m

30-- ! m

I'

!1 -- h

}

I --

o I I- -I .1 "t I I _.

0 6 12 1B 24 30 36 42 48 54 60

Frequency (lO00 rpm)

Figure B-10 T55 Power Turbine, Serial No. U00295

1 1 I 1 1 ) I 1 ) 1 I 1 I } 1 ] I 1
lOO I I I I I I I I I

90--- Turbine Speed = 15,600 rpm

Compressor Speed = 17,250 rpm

80m

70-- ---

o_

>

v 60m

o 50--

o

m

=

40---

0 _ i m

0 mn M

o t I t !

0 6 12 18 24 30 36 42 48 54 60

Frequency (i000 rpm)

F%gure B-II T55 Power Turbine, Serial No 265549
,_ lOO_ I I I I I I ,' ,

' ',

o_

90- - Turbine Speed - 15,600 rpm _ -

Compressor Speed - 17,250 rpm

0 m n m

m

70--

_60-- " -

4J

4J

o 50--

I.i

0

u]

m 40--

i

30 "-

20_ _ _

lOo-!_" ', --

0 3 6 9 12 15 18 21 24 27 30

Frequency (i000 rpm)

Figure B_12 T55 Power Turbine, Serial No. M265682 °

1 I I i I } J i ) I 1 t } 1 ] I I !
! I 1 _ I 1 _ ! I 1 l ! ! _ 1 I I

lOO i I l I I' i I I i

90--- Turbine Speed = 15,600 rpm --

Compressor Speed = 17,250 rpm

80....

\

70--

I,.4

v 60--

=

50-- 0

0

40--

>

30_

20 w

i0-- ,

o 1_/_ t I _ {

0 3 6 9 12 15 18 21 24 27 30

Frequency (I000 rpm)

Figure B-13 T55 Power Turbine, Serial No. 261845
lOO I { { { l { I { {

90- Turbine Speed = 15,600 rpm - -

Compressor Speed = 17,250 rpm

80-- -

20--

lOu --

o

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

Figure B-14 T55 Power Turbine, Serial No. 254954

I I i I } I i I 1 ) I } } I I I 1
loo I _ I I I I I I I

90-- Turbine Speed - 15,600 rpm --

Compressor Speed - 17,250 rpm

80-- -

"_ 70--

_60--

m B

4J

4-J

o 50--

14

0

4o--

P

30--

20_ --

m m

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure B-15 T55 Power Turbine, Serial No. U00259
!

_, loo I , I I I I I I I

0

o

Turblne Speed - 15,600 rpm

90--

Compressor Speed - 17,250 rpm

0 u _ m

70-- m

v 60--

cA

¢J

o 50--

0

I:l

40....

>

30--

0 m _ m

10--

....iv',_t.,...,..l _,?._ o , I I t t I I ,

0 6 12 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

Figure B-16 T55 Power Turbine, Serial No. 265530

i i I i ] i I I I i I I i } i i i }
1 I ! } _ ! l 1 ! I I I ! ! I ! 1 T

I I . I I I

lOO , , I , , I , I I

90- - Turbine Speed = 15,600 rpm

Compressor Speed - 17,250 rpm

80 m _

70 ....

_60 ....

4J

4J

50-- -._

k

o

4o--

P_

30-- _

20 _ _ _

lo_-, o__, , _ -

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

o Figure B-17 T55 Power Turbine, Serial No. 261830
lOO I I I I I I I I I

F-A

O

90---- Turbine Speed m 15,600 rpm --

Compressor Speed = 17,250 rpm

80--- _

0_ m m _

10-_ 0 _

0 6 12 18 24 30 36 42 48 54 60

Frequency (1000 rpm)

Figure B-18 T55 Power Turbine, Serial No. 268934

I I I I I I i I I I I I I I I I I )
1 _ I I 1 ! ! 1 l 1 1 I _ 1 I ! 1

m A .,|

1oo I , : ", I I '" I I I I

90- - Turbine Speed - 15,600 rpm - -

Compressor Speed = 17,250 rpm

20-- -- m

0

0 6 12. 18 24 30 36 42 48 54 60

Frequency (I000 rpm)

O Figure B-19 T55 Power Turbine, Serial No. U00212

REFERENCES

i. Tessarzik, Juergen M. "Flexible Rotor Balancing by the Influence Coefficient Method - Multiple Critical Speeds with Rigid or Flexible Supports."

NASA CR-2553, 1975.

2. Walter, Thomas J. "Study of T53 Engine Vibration." NASA CR-135449, 1978.

3. Martin_ Michael R. "T55 Power Turbine Rotor Multiplane-Multispeed

Balancing Study." NASA CR-167891, 1982.

105
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