bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupled Vibration of Unshrouded Centrifugal CompressorImpellers. Part I: Experimental Investigation
Authors: Hasemann Heinrich , Hagelstein Dirk , Rautenberg Manfred
Published: March 2007

The increased use of small gas turbines and turbochargers in different technical fields has led to the development of highly‐loaded centrifugal compressors with extremely thin blades. Due to the high rotational speed and the corresponding centrifugal load, the shape of the impeller hub must also be optimized. This has led to a reduction of the thickness of the impeller disc in the outlet region. The thin parts of the impeller are very sensitive and may be damaged by the excitation of dangerous blade vibrations.

dangerous blade vibrations. Experimental investigations by means of holographic interferometry and telemetry were carried out for two different impeller types; one with radial‐ending blades and the other with backswept blades. The results presented in Part I of the paper are able to explain the dominance of coupling effects between the blades and the disc in the middle and higher frequency range of the two tested impellers. Especially excitations caused by downstream sources such as vaned diffusers can endanger the blades and the impeller.

The finite element (FE) code computations presented in Part II of the paper to investigate the coupled vibration behavior of the whole impeller were found to be in close agreement with the experimental results.
On the Discrete–Continuous Modeling of Rotor Systems forthe Analysis of Coupled Lateral Torsional Vibrations
Authors: Szolc Tomasz
Published: March 2007

In the paper, dynamic investigations of the rotor shaft systems are performed by means of the discrete‐continuous mechanical models. In these models the rotor shaft segments are represented by the rotating cylindrical flexurally and torsionally deformable continuous viscoelastic elements. These elements are mutually connected according to the structure of the real system in the form of a stepped shaft which is suspended on concentrated inertial viscoelastic supports of linear or non‐linear characteristics. At appropriate shaft crosssections, by means of massless membranes, there are attached rigid rings representing rotors, disks, gears, flywheels and others. The proposed model enables us to investigate coupled linear or non‐linear lateral torsional Vibrations of the rotating systems in steady‐state and transient operating conditions. As demonstrative examples, for the steam turbo‐compressor under coupled lateral torsional vibrations, the transient response due to a blade falling out from the turbine rotor as well as the steady‐state response in the form of parametric resonance caused by residual unbalances are presented.
One‐dimensional Analysis of Impulse Turbine with Self‐pitch‐controlled Guide Vanes for Wave Power Conversion
Authors: Inioue M. , Kaneko K. , Setoguchi T.
Published: March 2007

A classical one‐dimensional analysis in turbomachinery was presented to estimate
aerodynamic characteristics of an impulse turbine with self‐pitch‐controlled guide vanes
which is proposed by the authors for ocean wave power conversion. With some simplified
assumptions, the efficiency vs/flow‐rate coefficient curves were calculated and compared
with the experimental results both in a unidirectional steady flow condition and a sinusoidally
oscillating flow condition. The estimated results reveal a behavior of the actual characteristics curve of the turbine. Possibility of further improvement in efficiency was discussed from a viewpoint of specific speed and specific diameter.
Laser Velocimeter Measurements in the Pump of an Automotive Torque Converter Part I – Effect of Speed Ratio
Authors: Ainley Steven B. , Flack Ronald D. , Brun Klaus , Rovello Tony J.
Published: March 2007

A torque converter was tested at four turbine/pump rotational speed ratios (0.200, 0.400, 0.600, and 0.800) all with a constant pump rotational speed in order to determine the effect of speed ratio on the torque converter pump flow field. Laser velocimetry was used to measure three components of velocity within the pump and a shaft encoder was employed to record the instantaneous pump angular position. Shaft encoder information was correlated with measured velocities to develop flow field blade‐to‐blade profiles and vector plots. Measurements were obtained in both the pump mid‐ and exit planes for all four speed ratios. Results showed large separation regions and jet/wake flows throughout the pump. The midplane flow was found to have strong counter‐clockwise secondary components and the exit plane flow had strong clockwise secondary components. Mass flows were calculated from the velocity data and were found to decrease as the speed ratio was increased. Also, the vorticity and slip factors were calculated from the experimental data and are included. The mid‐plane slip factors compare favorably to those for conventional centrifugal pumps but less slip was present in the exit plane than the mid‐plane. Neither the slip factor nor the vorticity were seen to be strongly affected by the speed ratio. Finally, the torque core‐to‐shell and blade‐to‐blade torque distributions are presented for both planes.
Theoretical and Experimental Investigation of the Dynamic Behaviour of Centrifugal Fans
Authors: Mariaux G. , Gervais Y. , Crespeau L.
Published: March 2007

In this paper, a theoretical model is proposed to investigate the centrifugal fans′ transient behaviour in response to sudden imposed changes in pressure or flow rate. We are especially interested in the dissipative or creative energy transient behaviour of the fans located in actual aeraulic networks.

The model is based on the global modelisation of the motor and resistant torques (due to pressure and viscosity actions on the blades) which are present on the rotor and by their coupling with its inertia.

The model is then validated by experimental measurements which show its validity. In the case of the tested fan, the instantaneous characteristics (in particular the flow rate and rotation speed) have been correctly predicted by the model, with regard to time as well as amplitudes, provided the flow is not reversed.
Stresses in Composite Shafts Subjected to UnbalanceExcitation and Transmitted Torque
Authors: Gubran H. B. H. , Singh S. P. , Gupta K.
Published: March 2007

In the present study, stress analysis of fiber reinforced thin composite shafts subjected to unbalance excitation and steady torque, is carried out. Shafts of uniform as well as variable wall thickness are considered. The shaft is modeled as a simply supported Timoshenko beam in which shear deformation, rotary inertia and gyroscopic effects have been included. Modified equivalent modulus beam theory has been adopted. Rayleigh‐Ritz displacements are used for deriving the solution equations. Shafts with a uniform wall thickness, and with variable wall thickness in which the thickness is varied along the axial length of the shaft for three different cases of fiber angles have been studied. Axial variation of stresses is studied in detail. Results obtained indicate that the stresses in the variable wall thickness are smaller than the one with uniform wall thickness, even for the same weight of the shaft.
Pump Damage in the Hanshin Earthquake
Authors: Osada Toshiyuki
Published: March 2007

There was a severe earthquake in the southern area ofHyogo prefecture in Japan on January 17, 1995. In this paper the damage to pump facilities caused by the earthquake, based on field investigation results in the Hanshin (Osaka–Kobe) area is reported. In particular a lot of damage was reported in the pumping facilities for sewage or drainage of storm sewage. This paper also presents recommendations for aseismic design of pump facilities based on the results of the survey.

Some of the kinds ofdamage to pumps were: pump submersion, shaft misalignment, case of pump rotor getting stuck, anchor bolt failure, pump casing cracking, bearing box failure. Most of the damage was fundamentally caused by unequal sinking ofthe building foundation. The damage to the pumps was mainly caused by deformation or collapse of building structures, or by excessive forces to be exerted on the pumps by the piping.

In order to prevent damage to pumps by earthquakes, a study of the earthquake resistance of the whole pumping facility including the pump itself should be made, and appropriate countermeasures and action taken.
Impulse Turbine with Self‐pitch‐controlled Guide Vanes for Wave Power Conversion (Effect of Guide Vane Geometry on the Performance)
Authors: Takao M. , Kinoue Y. , Setoguchi T. , Obayashi T. , Kaneko K.
Published: March 2007

An impulse turbine with self‐pitch‐controlled guide vanes has been developed specially for wave energy conversion by the authors. Based on that work, a large turbine of 1 m diameter has been fabricated and operated on the west coast of India. In a practical turbine system, the guide vanes need substantial supports in order to heighten the strength. Such supports affect the performance of the turbine. In this paper, the etfect of guide vane support geometry on starting and running characteristics of the turbine was investigated experimentally. Two types of cross sections of support were studied, that is, circular type and airfoil type. The effect of support length was also studied.
Rotating Machinery Predictive Maintenance Through Expert System
Authors: Kumar M. Sarath , Prabhu B. S.
Published: March 2007

Modern rotating machines such as turbomachines, either produce or absorb huge amount of power. Some of the common applications are: steam turbine‐generator and gas turbine‐compressor‐generator trains produce power and machines, such as pumps, centrifugal compressors, motors, generators, machine tool spindles, etc., are being used in industrial applications. Condition‐based maintenance of rotating machinery is a common practice where the machine′s condition is monitored constantly, so that timely maintenance can be done. Since modern machines are complex and the amount of data to be interpreted is huge, we need precise and fast methods in order to arrive at the best recommendations to prevent catastrophic failure and to prolong the life of the equipment. In the present work using vibration characteristics of a rotor‐bearing system, the condition of a rotating machinery (electrical rotor) is predicted using an off‐line expert system. The analysis of the problem is carried out in an Object Oriented Programming (OOP) framework using the finite element method. The expert system which is also developed in an OOP paradigm gives the type of the malfunctions, suggestions and recommendations. The system is implemented in C++.
Parametric Identification of a Dynamic Foundation Model of a Rotary Machine Using Response Data Due to Unknown Unbalances
Authors: Prells Uwe , Lees Arthur W.
Published: March 2007

The estimation of a model of the foundation of a rotary machine has been recently attempted by using the difference between two sets of response data at some of the bearing locations from two consecutive rundowns of the machine, with and without known unbalance weights at certain positions on the two balance discs of each rotor respectively. However, it would be a great advantage to be able to perform the estimation with a single rundown. Due to practical restrictions in performing such tests (accessibility, costs etc.), there are cases in which data for only one rundown are available. In this case, the unbalance configuration is unknown and has, therefore, to be estimated, in addition to the unknown foundation model. Due to the special form of the unbalance force, this overall inverse problem can be solved by eliminating the unbalance configuration from the model estimation process. The remaining equation to estimate the foundation model consists of the projection of the response data, where the associated projector depends on the foundation model parameter. First results using the method, applied to a laboratory test rig and to a commercial turbo‐generator, are presented.
Modeling of Tilting‐Pad Journal Bearings with Transfer Functions
Authors: Vázquez J. A. , Barrett L. E.
Published: March 2007

Tilting‐pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor‐bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting‐pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting‐pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.
Using Plücker Coordinates for Pumping Speed Evaluation of Molecular Pumpin the DSMC Method
Authors: Chen Fong-Zhi , Tsai Ming-June , Chang Yu-Wen , Jou Rong-Yuan , Cheng Hong-Ping
Published: March 2007

In this study, the Plücker coordinates representation is used to formulate
the ruled surface and the molecular path for pumping speed performance evaluation of a
molecular vacuum pump. The ruled surface represented by the Pliicker coordinates is used
to develop a criterion for when gas molecules hit the pump surface wall. The criterion is
applied to analyze the flow rate of a new developed vacuum pump in transition regimes by
using the DSMC (Direct Simulation Monte Carlo) method. When a molecule flies in a neutral
electrical field its path is a straight line. If the molecular path and the generators of a ruled
surface are both represented by the Pliicker coordinates, the position of the molecular hit on
the wall can be verified by the reciprocal condition of the lines. The Plücker
coordinates representation is quite convenient in the DSMC method for this
three‐dimensional molecular flow simulation.
Recent Development in Turbine Blade Film Cooling
Authors: Han Je-Chin , Ekkad Srinath
Published: March 2007

Gas turbines are extensively used for aircraft propulsion, land‐based power generation, and industrial applications. Thermal efficiency and power output of gas turbines increase with increasing turbine rotor inlet temperature (RIT). The current RIT level in advanced gas turbines is far above the .melting point of the blade material. Therefore, along with high temperature material development, a sophisticated cooling scheme must be developed for continuous safe operation of gas turbines with high performance. Gas turbine blades are cooled internally and externally. This paper focuses on external blade cooling or so‐called film cooling. In film cooling, relatively cool air is injected from the inside of the blade to the outside surface which forms a protective layer between the blade surface and hot gas streams. Performance of film cooling primarily depends on the coolant to mainstream pressure ratio, temperature ratio, and film hole location and geometry under representative engine flow conditions. In the past number of years there has been considerable progress in turbine film cooling research and this paper is limited to review a few selected publications to reflect recent development in turbine blade film cooling.
A Transient Method Using Liquid Crystal for Film Cooling Over a Convex surface
Authors: Chen Ping-Hei , Hung Min-Sheng , Ding Pei-Pei
Published: March 2007

In order to explore the effect of blowing ratio on film cooling over a convex surface, the present study adopts the transient liquid crystal thermography for the film cooling
measurement on a straight circular hole configuration. The test piece has a strength of
curvature (2r/D) of 92.5, pitch to diameter ratio
(P/D) of 3 and streamwise injection
angle (γ) of 35∘ All measurements were conducted under the mainstream Reynolds
number (Red) of 1700 with turbulence intensity (Tu) of 3.8%, and the density ratio between coolant and mainstream (ρc/ρm) is 0.98. In current study, the effect of blowing
ratio (M) on film cooling performance is investigated by varying the range of blowing
ratio from 0.5 to 2.0. Two transient tests of different injection flow temperature were
conducted to obtain both detailed heat transfer coefficient and film cooling effectiveness
distributions of measured region. The present measured results show that both the
spanwise averaged heat transfer coefficient and film cooling effectiveness increase with
decreased blowing ratio.
Including the Effects of Flexible Bearing Supportsin Rotating Machinery
Authors: Vázquez José A. , Barrett Lloyd E. , Flack Ronald D.
Published: March 2007

Unbalance response and stability analyses of a flexible rotor on three lobe journal
bearings on flexible supports are presented. The influence of the support structure was
included in the analyses using polynomial transfer functions. These transfer functions
were extracted from measured dynamic compliance data of the support structure,
measured at the bearing locations. Numerical predictions using polynomial transfer
functions and single mass supports are compared to the experimental data. Predictions
using the transfer function representation of the support structure show a clear improvement
over the predictions using single mass supports without over‐complicating
the problem. The predicted critical speeds are within 2.9% of the measured critical
speeds. The predicted stability threshold agrees with the measured stability threshold
within 1%. The effects of cross talk between supports and cross coupling between
horizontal and vertical directions are investigated. The cross talk between supports was
found to have a strong influence in the results while the influence of cross coupling
between the vertical and horizontal directions is negligible.
Stability Analysis of Symmetrical Rotors PartiallyFilled with a Viscous Incompressible Fluid
Authors: Changsheng Zhu
Published: March 2007

On the basis of the linearized fluid forces acting on the rotor obtained directly by using the two‐dimensional Navier‐Stokes equations, the stability of symmetrical rotors with
a cylindrical chamber partially filled with a viscous incompressible fluid is investigated
in this paper. The effects of the parameters of rotor system, such as external damping
ratio, fluid fill ratio, Reynolds number and mass ratio, on the unstable regions are
analyzed. It is shown that for the stability analysis of fluid filled rotor systems with
external damping, the effect of the fluid viscosity on the stability should be considered.
When the fluid viscosity is included, the adding external damping will make the system
more stable and two unstable regions may exist even if rotors are isotropic in some
casIs.
Influence of Inter‐row Gap Value on Turbine Losses
Authors: Cizmas Paul G. A. , Hoenninger Corbett R. , Chen Shun , Martin Harry F.
Published: March 2007

This paper presents the results of a numerical investigation of the gap influence on the turbine efficiency. The rotor‐stator interaction in a (1/2)‐stage turbine is simulated by
solving the quasi‐three‐dimensional unsteady Euler/Navier‐Stokes equations using a
parallelized numerical algorithm. The reduced turnaround time and cost/MFLOP of
the parallel code was crucial to complete the numerous run cases presented in this
paper. The inter‐row gap effect is evaluated for 4 gaps, 3 radial positions and 3 angular
velocities. As expected, the results presented in this paper show that the efficiency
increases and losses decrease while the gap size increases. The maximum efficiency
location, however, corresponds to values of the gap size which may be too large for
practical use (approximately inch). Fortunately, a local maximum efficiency and
minimum losses location has been found at approximately 0.5 inches gap size. The
efficiency variation near the local optimum is large, in some configurations being as high
as 1.4 points for a gap size variation of only 0.076 inches. Data produced by the
numerical simulations can be used to develop a design rule based on the inter‐row gap
size.
Effects of Gaps Between Side‐Walls and 60∘ Ribs on the Heat Transfer and Rib Induced Secondary FlowInside a Stationary and Rotating Cooling Channel
Authors: Kiml Robert , Mochizuki Sadanari , Murata Akira
Published: March 2007

The present study investigates the effects of gaps between the side‐walls and 60∘ ribs on the local heat transfer distribution between two consecutive ribs. The heat transfer and flow visualization experiments were carried out inside a straight rib‐roughened duct with the ribs mounted on two opposite side walls with and without the gaps. The results showed that the existence of the gaps appreciably enhances the Nu in the area between two consecutive ribs. It is caused by (1) the introduction of the fresh air through the gaps into this region, and (2) the improvement of the three‐dimensional flow structure in the area between the two ribs.
Abnormally High Power Output of Wind Turbine in Cold Weather: A Preliminary Study
Authors: Leclerc Christophe , Masson Christian
Published: March 2007

According to popular belief, air temperature effects on wind turbine power output are produced solely by air density variations, and power is proportional to air density. However, some cases have been reported, all involving stall‐controlled wind turbines, in which unexpected high power output was observed at very low temperatures.

As a preliminary study, this article intends to quantify the influence of air temperature on the power production of the Tacke TW600 wind turbine installed in Tiverton, Ontario, Canada. Increases in power output due to air temperature variation are stratified by wind velocity, showing that these increases are below the theoretical limits of air density variations during operation in low winds and are comparable to and beyond those theoretical limits at higher wind velocities. At – 9°C and 0°C, narrow bands of power at distinct levels are observed in the stall regime of the turbine; they are typical of many stall phenomena observed on stall‐controlled rotors, but these levels have been found to be independent of any parameters recorded.
Thermomechanical Behavior of Rotor with Rubbing
Authors: Sawicki Jerzy T. , Montilla-Bravo Alberto , Gosiewski Zdzislaw
Published: March 2007

This article presents an analytical study of the dynamics and stability of rotors subjected to rubbing due to contact with seals, taking account of associated thermal effects. The seal interaction force acting on the shaft gives rise to a friction force, which is a source of heating and can induce so‐called spiral vibrations. A mathematical model that has been developed couples the heat‐conduction equation with the equations for motion of the rotor. Numerical simulations have been conducted that show the thermomechanical behavior of the rotor at various operating conditions. A procedure for analyzing the stability of multibearing rotors based on the system eigenvalue analysis and the state‐space approach has been proposed. Finally, the experimental data related to full annular rub have been presented.
Investigation of Flow Through Centrifugal Pump Impellers Using Computational Fluid Dynamics
Authors: Zhou Weidong , Zhao Zhimei , Lee T. S. , Winoto S. H.
Published: March 2007

With the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the design of pumps. This article describes the three‐dimensional simulation of internal flow in three different types of centrifugal pumps (one pump has four straight blades and the other two have six twisted blades). A commercial three‐dimensional Navier‐Stokes code called CFX, with a standard k–ε two‐equation turbulence model was used to simulate the problem under examination. In the calculation, the finite‐volume method and an unstructured grid system were used for the solution procedure of the discretized governing equations for this problem.

Comparison of computational results for various types of pumps showed good agreement for the twisted‐blade pumps. However, for the straight‐blade pump, the computational results were somewhat different from widely published experimental results. It was found that the predicted results relating to twisted‐blade pumps were better than those relating to the straight‐blade pump, which suggests that the efficiency of a twisted‐blade pump will be greater than that of a straight‐blade pump. The calculation also predicts reasonable results in both the flow pattern and the pressure distribution.
Expert System Source Identification of Excessive Vibration
Authors: Kirk R. Gordon , Guo Zenglin
Published: March 2007

The importance of vibration data in determining the condition of rotating machinery is well established in both the aircraft and the heavy equipment industries. Installation of noncontact displacement probes for shaft motion and either velocity or acceleration sensors for bearing cap or foundation motion is standard practice for equipment manufacturers. Automation of the diagnostic evaluation of certain simple faults can be easily implemented. The advances in computer languages in recent years have made it diffiucult to keep pace with the graphical capabilities available to the programmers. One major concern is the content of the knowledge base and the method of modifying the knowledge base or the procedure of evaluating the confidence of a given identified possible cause of a problem. This article addresses the application of one such expert system to a recent vibration problem on a 7‐megawatt steam turbine–driven generator located at the power plant of Virginia Polytechnic Institute.
Identification of Rub and Unbalance in 320 MW Turbogenerators
Authors: Bachschmid N. , Pennacchi P. , Vania A. , Zanetta G. A. , Gregori L.
Published: March 2007

This article presents two experiences of applying a model‐based fault‐identification method to real machines. The first case presented is an unbalance identification in a 320 MW turbogenerator unit operating in a fossil power plant. In the second case, concerning a machine of the same size but from a different manufacturer, the turbine has been affected by a rub in the sealings. This time, the fault is modeled by local bows. The identification of the faults is performed by means of a model‐based identification technique in a frequency domain, suitably modified in order to take into account simultaneous faults. The theoretical background of the applied method is briefly illustrated and some considerations are also presented about the best choice of the rotating speed set of the run‐down transient to be used for an effective identification and about the appropriate weighting of vibration measurements at the machine bearings.
Effects of Volute Design and Number of Impeller Blades on Lateral Impeller Forces and Hydraulic Performance
Authors: Baun Daniel O. , Flack Ronald D.
Published: March 2007

A comparison is made between the characteristics of the measured lateral impeller forces and the hydraulic performances of a four‐ and a five‐vane impeller, each operating in a spiral volute, a concentric volute, and a double volute. The pump′s rotor was supported in magnetic bearings. In addition to supporting and controlling the rotor motion, the magnetic bearings also served as active load cells and were used to measure the impeller forces acting on the pump′s rotor. The lateral impeller force characteristics, as a function of a normalized flow coefficient, were virtually identical in the four‐ and five‐vane impellers in each respective volute type. The measured impeller forces for each volute type were compared with correlations in the literature. The measured forces from the double volute configurations agreed with the forces from a correlation model over the full flow range. Single volute configurations compared well with the predictions of a published correlation at high flow rates, ϕ/ϕn > 0.5. Concentric volute configurations compared well with a published correlation at low flow rates, ϕ/ϕn < 0.4. The head‐versus‐flow characteristics of the four‐vane impeller in each volute type were stable over a greater flow range than the corresponding characteristics of the five‐vane impeller. At higher flow rates in the stable region of the head′s characteristic curves near the best efficiency point, the five‐vane impeller produced higher head than did the four‐vane impeller in each volute type.
Using the Modal Method in Rotor Dynamic Systems
Authors: Malenovský Eduard
Published: March 2007

This article deals with computational modeling of nonlinear rotor dynamic systems. The theoretical basis of the method of dynamic compliances and the modal method, supplemented by the method of trigonometric collocation, are presented. The main analysis is focused on the solutions of the eigenvalue problem and steady‐state and transient responses. The algorithms for solving this range of problems are presented. The finite element method, the method of dynamic compliances, and the modal method are supplemented by the trigonometric collocation method. The theoretical analysis is supplemented by the solution of a model task, which is focused on the application of the trigonometric collocation method. The solution of a technical application, which is a pump, is presented in this article.
Vibration and Stability of 3000‐hp, Titanium Chemical Process Blower
Authors: Gutzwiller Les , Corbo Mark A.
Published: March 2007

This 74‐in‐diameter blower had an overhung rotor design of titanium construction, operating at 50 pounds per square inch gauge in a critical chemical plant process. The shaft was supported by oil‐film bearings and was directdriven by a 3000‐hp electric motor through a metal disk type of coupling. The operating speed was 1780 rpm. The blower shaft and motor shaft motion was monitored by Bently Nevada proximity probes and a Model 3100 monitoring system.

Although the blowers showed very satisfactory vibration levels during test runs at the manufacturer′s plant, the vibration levels in situ had always been higher than was desirable. After several months of monitoring showed ever increasing vibration levels, one of the blowers was shut down in order to diagnose and resolve the problem.

Several steps were taken to diagnose the problem: (1) The rotor was removed and the shop balance was checked and corrected. (2) The bearing support movement due to thermal expansion was measured. Then the shafts were misaligned in the cold condition in order to achieve near‐perfect shaft alignment during normal operation. (3) The expected shaft vibration at the bearings was determined using lateral rotor dynamics analysis, including critical speed mapping. (4) A heavy sleeve was added to the blower shaft to increase the radial load on the drive‐end bearing. (5) The metal disk type of coupling was replaced by a gear coupling. (6) The finite element and impact of the bearing support pedestal were tested to determine the stiffness of the bearing support. (7) The shaft movement was measured during a coast‐down. (8)Tilting‐pad bearings were evaluated as a possible replacement for the original standard sleeve type of hydrodynamic oil‐film bearings.

The final solution showed the importance of coupling angular stiffness (often rarely considered in machine design), rotor dynamic analysis, and field alignment.
Spatial Dynamics of Tuned and Mistuned Bladed Disks with Cylindrical and Wedge‐Shaped Friction Dampers
Authors: Panning Lars , Sextro Walter , Popp Karl
Published: March 2007

One of the main tasks in the design of turbomachines like turbines, compressors, and fans is to increase the reliability and efficiency of the arrangement. Failures due to blade cracks are still a problem and have to be minimized with respect to costs and safety aspects. To reduce the maximum stresses, the blades can be coupled via friction damping devices such as underplatform dampers that are pressed onto the blade platforms by centrifugal forces. In this work, a method will be presented to optimize two different types of underplatform dampers in bladed disk applications with respect to a maximum damping effect.

In practice, underplatform dampers with various geometric properties—cylindrical and wedge‐shaped—are commonly used and lead to different contact conditions. A discretization of the contact areas between the blade platforms and the dampers is applied to be able to investigate nearly arbitrary contact geometries and spatial blade vibrations. The functionality of the two mentioned damper types has been studied in detail under different working conditions of the assembly. The advantages and disadvantages of both damper types are pointed out and strategies are presented to improve the damper design. In this context, the influence of mistuning effects is discussed in terms of statistical mistuning of the blades′ natural frequencies due to manufacturing tolerances as well as systematical mistuning due to a deliberate slight variation of the blade masses or geometries.
Panel Discussion on Inducer Design Criteria
Authors: Wegner Marc , Acosta Allan J. , Tsujimoto Yoshinobu
Published: March 2007

This article reports a panel discussion titled Inducer Design Criteria presented at the 9th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC‐9). The presentations of the panelists and the subsequent discussions are summarized. It is shown that cavitation instabilities are major problems in modern turbopumps and that design criteria to eliminate them are needed. Available design methods for inducers and marine propellers are reviewed, and new criteria to enhance stability are proposed. The current status of CFD is reviewed and an example of successful application is shown. Discussions of several specific topics are reported and future research needs are noted.
Reduction of Discrete‐Frequency Fan Noise Using Slitlike Expansion Chambers
Authors: Sadamoto Akira , Murakami Yoshinori
Published: March 2007

As is generally known, discrete‐frequency noises are radiated from fans due to rotor‐stator interaction. Their fundamental frequency is the blade‐passage frequency, which is determined by the number of rotor blades and their rotating speeds. To reduce such noises, several types of silencers have been designed. Among them, the authors noted a slitlike expansion chamber (hereafter referred to as slit, for simplicity) and have studied its performance. A slit is a simple expansion chamber with a very short axial length that is placed in a duct. A slit with a circular cross‐section that is concentric with a circular duct may be studied using the same interpretation as is used for a side‐branch resonator muffler (closed‐end tube connected to a duct); that is, the resonant frequency of a slit depends on its depth (with an open‐end correction). It is expected, hence, that a slit might be applicable as a simple and axially compact silencer that is effective on discrete‐frequency noises. In this article, the properties of a slit are introduced, and the applicability of a slit to actual rotating machinery is described using experimental data.
Numerical Calculation of the Three‐Dimensional Swirling Flow Inside the Centrifugal Pump Volutes
Authors: Nursen E. Cezmi , Ayder Erkan
Published: March 2007

The flow inside the volute of a centrifugal pump is threedimensional and, depending upon the position of the inlet relative to the cross‐section center line, a single or double swirling flow occurs. The purpose of this study was the calculation of the three‐dimensional swirling flow inside the centrifugal pump volute.

The developed flow solver provides detailed pressure and velocity distribution information inside the volute, and the calculated results are verified by means of the experimental results presented in the literature.

Three‐dimensional continuity and momentum equations are solved by means of an artificial compressibility technique. The finite volume approach is applied for space discretization, and an explicit fourth‐order modified Runge‐Kutta scheme is used for time discretizetion.

Calculations are performed at three different mass flows, one of which corresponds to the design′s point mass flow. The calculated volute flow conditions—namely, the variation in static pressure and total pressure and the through‐flow and swirling component of the flow velocity over the cross‐sections, which are located at various circumferential positions—are compared with the experimental data in detail, and they exhibit a good agreement with the measured flow field.
Comparison of Two Diffusers in a Transonic Centrifugal Compressor
Authors: Nakagawa Koji , Hayami Hiroshi , Keimi Yuichi
Published: March 2007

Flow mechanisms suppressing the flow separation in two diffusers, a low‐solidity cascade diffuser and a vaned diffuser with additional small vanes near the inlet, were compared mainly by numerical simulation. As the superiority of the low‐solidity cascade diffuser was expected, a series of experiments was conducted using a transonic centrifugal compressor with a maximum pressure ratio of 7. The performance of the compressor with the vaned diffuser was comparable to that of the low‐solidity cascade diffuser only between the surge point and the design flowrate at a pressure ratio of 3.5. The maximum flowrate of the vaned diffuser was lower than that of the low‐solidity cascade diffuser. At higher rotational speeds, the pressure ratio at the surge point, the efficiency, and the flow range of the low‐solidity cascade diffuser exceded those of a vaned diffuser at a pressure ratio of 3.5.
Pressure Fluctuation in a Vaned Diffuser Downstream from a Centrifugal Pump Impeller
Authors: Furukawa Akinori , Takahara Hisasada , Nakagawa Takahiro , Ono Yusuke
Published: March 2007

Periodic flows downstream from a centrifugal pump impeller in vaneless and vaned diffusers were measured by using a single hole yawmeter and a phase‐locked sampling method. The flows were also calculated by an inviscid flow analysis using the blade‐surface singularity method. The periodic variations in calculated static pressure with the impeller rotating quantitatively agree well with the measured ones. The flow behaviors in the vaned diffuser are discussed, citing measured and calculated results. The potential interaction between the impeller and the diffuser blades appears more strongly than the impeller‐wake interaction. The appearance of static pressure fluctuations due to the impeller′s rotating in the fully vaned zone is different from that in the semivaned zone of the diffuser. The existence of the peripheral blade surface of the impeller outlet with an outlet edge of the pressure surface causes violent pressure fluctuations in the vaned diffuser.
Numerical Simulation of Combustion and Rotor‐Stator Interaction in a Turbine Combustor
Authors: Isvoranu Dragos D. , Cizmas Paul G. A.
Published: March 2007

This article presents the development of a numerical algorithm for the computation of flow and combustion in a turbine combustor. The flow and combustion are modeled by the Reynolds‐averaged Navier‐Stokes equations coupled with the species‐conservation equations. The chemistry model used herein is a two‐step, global, finite‐rate combustion model for methane and combustion gases. The governing equations are written in the strong conservation form and solved using a fully implicit, finite‐difference approximation. The gas dynamics and chemistry equations are fully decoupled. A correction technique has been developed to enforce the conservation of mass fractions. The numerical algorithm developed herein has been used to investigate the flow and combustion in a one‐stage turbine combustor.
Experimental Investigation of Cavitation Signatures in an Automotive Torque Converter Using a Microwave Telemetry Technique
Authors: Anderson C. L. , Zeng L. , Sweger P. O. , Narain A. , Blough J. R.
Published: March 2007

A unique experimental investigation of cavitation signatures in an automotive torque converter under stall conditions is reported. A quantitative criterion is proposed for predicting early and advanced cavitation in terms of suitable nondimensional pump speeds. The dimensionless pump speed that marks early cavitation is obtained by relating this parameter to the appearance of charge‐pressure–dependent pressure fluctuations in the differential pressure transducer readings. The differential pressure transducers were mounted at well‐defined locations in the pump passage of a torque converter. The data were transmitted by a wireless telemetry system mounted on the pump housing. Data were received and processed by a ground‐based data acquisition system. Automatic transmission fluid exhibited cavitation for charge pressures of 70–130 psi and pump speeds of 1000– 2250 rpm. Advanced cavitation was marked by operating conditions that exhibited a 2% or more torque degradation from the converter′s noncavitating performance.

For a given family of torque‐converter designs and a given transmission fluid, the proposed nondimensional pumpspeed criteria are capable of marking early and advanced stages of cavitation for a range of torque‐converter sizes and a range of charge pressures in the torque converter.
Flow Characteristics at the Pump‐Turbine Interface of a Torque Converter at Extreme Speed Ratios
Authors: Habsieger A. , Flack R. D.
Published: March 2007

The average velocity field at the pump–turbine interface in a scaled version of a truck torque converter was studied. Seven different turbine‐to‐pump rotational‐speed ratios were examined, ranging from near stall (0.065) to overspeed (1.050) so as to determine the effect of the speed ratio on the flow field and on the mass flow rate. Laser velocimetry was used to measure the flow velocity through the pump′s exit and the turbine′s inlet plane. At the pump′s exit, as the speed ratio increases, the high velocities move to the pressure‐shell corner and then to both the core‐suction and the pressureshell corners. Concentrated velocity gradients are largest at the lowest speed ratio, but areas of velocity gradients are largest near the coupling point. Near the coupling point, the flow field is most nonuniform, which yields a highly periodic flow into the turbine inlet. Above the coupling point, the high velocity remains in the pressure‐shell corner but separation is seen to develop at the highest speed ratio. At the turbine′s inlet, reverse flow is seen at low speed ratios and is an indicator of flow leakage through the core. Velocity gradients are very large at low speed ratios. As the speed ratio increases to the coupling point, the high velocities remain on the shell side. Above the coupling point, the high‐velocity flow migrates from the shell side to the core side. The mass flow rate decreases significantly and nonlinearly with the increase of the speed ratio, but for speed ratios greater than 1.000, the negative slope decreases.
Characteristics of Steady and Transient Superfluid Transport for the Cooling of Superconducting Rotating Machines
Authors: Chuang Thomas C.
Published: March 2007

The unique properties of superfluid helium (He II) make it a very efficient cooling agent for superconducting rotating machines. Steady and transient transport characteristics and design formulas for the cooling of superconducting windings are enumerated in this article. Several superfluid transport analytical models and useful design equations are discussed: laminar flow; turbulent flow; and pure superfluid flow under steady‐state and transient conditions. An effort was made to consolidate all analytical models and experimental results into a common framework. Under conditions of steady He II transport, a dimensionless heat flux number Nq, a dimensionless driving force number N∇T, and a characteristic length where used so that a generalized equation could be derived to describe superfluid transport in any geometry. In the case of transient transport of He II, a dimensionless heat flux number Nq∗ and a dimensionless driving time number Nt were used so that a generalized equation could be derived to describe transient superfluid transport in laminar flow and turbulent regimes. Many experimental data were compiled to substantiate the analysis.
The Dynamic Modeling of Multiple Pairs of Spur Gears in Mesh, Including Friction and Geometrical Errors
Authors: Jia Shengxiang , Howard Ian , Wang Jiande
Published: March 2007

This article presents a dynamic model of three shafts and two pair of gears in mesh, with 26 degrees of freedom, including the effects of variable tooth stiffness, pitch and profile errors, friction, and a localized tooth crack on one of the gears. The article also details howgeometrical errors in teeth can be included in a model. The model incorporates the effects of variations in torsional mesh stiffness in gear teeth by using a common formula to describe stiffness that occurs as the gears mesh together. The comparison between the presence and absence of geometrical errors in teeth was made by using Matlab and Simulink models, which were developed from the equations of motion. The effects of pitch and profile errors on the resultant input pinion angular velocity coherent‐signal of the input pinion′s average are discussed by investigating some of the common diagnostic functions and changes to the frequency spectra results.
Effects of Compressibility on the Performance of a Wave‐Energy Conversion Device with an Impulse Turbine Using a Numerical Simulation Technique
Authors: Thakker A. , Dhanasekaran T. S. , Takao M. , Setoguchi T.
Published: March 2007

This article presents work carried out to predict the behavior of a 0.6 m impulse turbine with fixed guide vanes as compared with that of a 0.6 hub‐to‐tip ratio turbine under real sea conditions. In order to predict the true performance of the actual oscillating water column (OWC), the numerical technique was fine‐tuned by incorporating the compressibility effect. Water surface elevation versus time history was used as the input data for this purpose. The effect of compressibility inside the air chamber and the turbine′s performance under unsteady and irregular flow conditions were analyzed numerically. Considering the quasi‐steady assumptions, the unidirectional steady‐flow experimental data was used to simulate the turbines characteristics under irregular unsteady flow conditions. The results showed that the performance of this type of turbine is quite stable and that the efficiency of the air chamber and the mean conversion efficiency are reduced by around 8% and 5%, respectively, as a result of the compressibility inside the air chamber. The mean efficiencies of the OWC device and the impulse turbine were predicted for 1 month, based on the Irish wave climate, and it was found that the total time period of wave data used is one of the important factors in the simulation technique.