bluuebunny/crossref_metadata_2025 huggingface dataset:
Danish Navy Experience With the KV-72 LM2500 CODOG Propulsion Plant
Authors: Hansen Bent , Larsen Sloth , Tenhundfeld John W.
Published: April 2015

For more than twenty years the Royal Danish Navy (RDN) has been using gas turbine engines for propulsion of fast patrol vessels as well as frigates. This paper, which is the result of a joint effort by the Royal Danish Navy, Aalborg Vaerft Shipyard, and General Electric Company USA, describes how the propulsion system design was developed using previous RDN gas turbine system experience. A detailed description of the ship, the selection of machinery, and design of the propulsion configuration, including the LM2500 gas turbine module, is included.

The three Royal Danish “KV-72” corvettes of the NIELS JUEL class have now been in operation for almost three years. Since the start-up of the NIELS JUEL machinery in November 1978 the CODOG propulsion plants aboard this class have accumulated more than 8,000 running hours, of which over 1,500 hours have been in the gas turbine or “sprint” drive mode. Operational experience with the GE LM2500 gas turbines is also described.
In Situ Balancing of Flexible Rotors Using Influence Coefficient Balancing and the Unified Balancing Approach
Authors: Darlow Mark S.
Published: April 2015

A number of sophisticated procedures for balancing flexible rotors have been developed during the past two decades. For a variety of reasons, none of these methods has gained general acceptance by practicing balancing engineers. Several of these balancing techniques require a great deal of operator insight and expertise. This has tended to discourage many potential users where this expertise was not already available in-house, particularly where balancing is required as a production operation. In other cases (for example large steam turbines), the machinery owner has had to rely on the manufacturer to provide this balancing expertise when it is needed often resulting in excessive downtime and maintenance costs.

Other balancing methods have been developed which are more systematic so as to reduce the level of expertise required of the user. Unfortunately, these methods have invariably required the collection of large quantities of data and very complex computations. Thus, originally, this data was taken by hand and transcribed for input to a large computer. The results of the balancing calculations were returned some time later for use by the balancing engineer. Such an operation was clearly not conducive to effective commercial application. With the development of minicomputers, the situation was alleviated to a certain extent through the use of more accessible, and even on-line computers to perform these calculations. However even with these minicomputers, in-place flexible rotor balancing facilities were expensive and inconvenient to assemble, and in situ balancing of flexible rotors was impractical if not impossible.

The subsequent development of the microcomputer has made in situ balancing of flexible rotors a possibility. This paper describes a completely portable, microcomputer-based flexible rotor balancing system that uses influence coefficient balancing and the Unified Balancing Approach two of the systematic methods which have been shown to be very effective for balancing flexible rotors. The results of a series of verification tests are also presented.
Initial Evaluation of a Coal Burning Turbine Powered Vehicle System
Authors: Stettler Richard J. , Bell Albert H. , Shows Everett W.
Published: April 2015

The conversion of coal to a useful transportation fuel results in low energy conversions if processed to liquid fuels. The approach to improve the energy conversion of coal to a transportation fuel by using it in its solid state was explored. An Eldorado vehicle with a gas turbine installed was used to demonstrate the feasibility of using coal in its solid state if cleaned and micronized. The mobile unit required storage on board the vehicle for micronized coal, a pumping system to deliver the coal to the engine, a modified fuel injector and a modified combustor to efficiently burn the solid fuel.
Built-In Test Equipment (BITE) on the Garrett Model GTCP331 APU Digital Electronic Control Unit
Authors: LaCroix Stephen R. , Stokes Richard F.
Published: April 2015

The advent of digital microprocessor electronic controls with decision making capabilities and airline interest in improved maintenance has resulted in the incorporation of powerful Built-In-Test-Equipment (BITE) in the latest Garrett gas turbine auxiliary power unit electronic control. BITE has been designed into the control to help isolate defective components and display this information. Garrett historical background and troubleshooting experience was combined with that of the Boeing Company, Messerschimitt-Bolkow-Blohm (MMB), and United Airlines (UAL) to obtain an effective system. Discussion includes BITE design philosophy, how the system functions, and how the information is displayed.
The Impact of Computers on the Test Cell of Tomorrow
Authors: Ash Clifford F.
Published: April 2015

Rapidly increasing fuel costs, the increasing complexity of the new engines now available, along with the inaccuracies, inefficiencies and long test cycles inherent in manual testing push the cost of engine testing to unnecessary levels. One promising avenue of relief is the automation of gas turbine testing through the use of real-time computer data acquisition and processing systems.

Remarkable progress has been made in the area of closed-loop or fully automatic operation of the test process from start-up using various programmable steps, recording results as dictated by the test procedure, controlling operation and a safe engine shut down. This paper discusses the successful application of a real-time computer system with both closed and open-loop capabilities. This particular system called “ADAPS™” (Automatic Data Acquisition and Processing System) handled its first 3,000 hours of engine operation without a single hardware or software interruption. Savings in manpower alone in that period was nearly 18,000 man-hours.
Development and Field Experience of a 27,400 HP Aeroderivative Gas Turbine
Authors: Hubbard J. K. , Tillinger R.
Published: April 2015

The paper describes the development and field experience of the model DJ270G Gas Turbine, the second of the manufacturer’s “second generation” gas turbines. By combining the merits of a proven aero-derivative gas generator with an advanced power turbine, the DJ270G has been developed to provide a reliable and efficient dual shaft gas turbine. Previously established power turbine design concepts were uniquely modified to maximize the overall efficiency of the unit. The introduction rate was advanced by running the development and manufacturing programs simultaneously. Field development was minimized by completing a full load performance test program in the factory prior to start-up of the first field unit. The completed machine has achieved an output of 27,400 horsepower with a thermal efficiency of 36.3%. Four units are now in operation and have logged over 33,000 hours of successful operation.
Integrated Flight and Propulsion Operating Modes for Advanced Fighter Engines
Authors: Brown Harold , Fisk William S.
Published: April 2015

This paper presents the results of preliminary studies of advanced propulsion system requirements and capabilities for the next generation of fighter aircraft. It represents an examination of current and advanced concepts of internal variable engine geometry and advanced exhaust system concepts for use in expanding the role of the propulsion system in the flight process. Special engine operating modes are defined and their potential capabilities are described. In-flight thrust vectoring and reversing concepts are described and their use in providing propulsive pitch and yaw forces for flight control assist are discussed. Potential control concepts and requirements for implementing the advanced engine operating modes are also described.
Development of a High Temperature Closed Cycle for Energy Saving in LNG Terminals
Authors: Bellofatto Oreste , Galli Augusto , Casmirri Carlo
Published: April 2015

Several systems for cold energy saving in LNG regasification terminals through electric energy production have been studied and developed up to now based on closed cycles.

This paper schematically compares the main features of a nitrogen high temperature closed cycle with those of a Rankine cycle.

The actual technical possibility of achieving modular plants for 2×109 Nm3/y gasified LNG and for 61 MWh/h electric production with a 993 K max. temperature nitrogen closed cycle is examined.

The Authors illustrate the efficiency trend versus temperature and report the future development of the above cycle with temperatures up to 1093 K.
A Design Study of a Reaction Control System for a V/STOL Fighter/Attack Aircraft
Authors: Beard B. B. , Foley W. H.
Published: April 2015

For all V/STOL aircraft, some type of attitude control is required in the hovering mode. In the past, this requirement has usually been met with a Reaction Control System (RCS) — a so-called “Puffer-Pipe” system which consists of high pressure gas ducted about the airframe and exhausted through nozzles at the wing tips, nose and tail.

This paper discusses a preliminary design study of an RCS for a STOVL aircraft conceptual configuration presently being developed by General Dynamics’ Fort Worth Division. The study highlights critical limitations and considerations relevant to the choice of an RCS concept. Physical requirements for RCS performance are detailed. Basic physical tradeoffs are elucidated. Various RCS candidate concepts are presented, and judged for their respective merits and drawbacks. The candidate system judged best suited for the particular application proposed is presented and discussed.
Simplified Inverse Design of a Straight Vaneless Diffuser of Radial Stage
Authors: Horn S. V.
Published: April 2015

Two inverse design methods of a vaneless diffuser, with the inviscid core symmetry along radial mid-streamline, are presented. Inverse design models consist of an inviscid core and attached skewed turbulent boundary layers computed by Cebeci’s method. The displacement model was used for inverse design studies and compared with the entrainment model. Both inverse design models were corroborated with the published vaneless diffuser design featuring convergent contours. For the same inlet conditions the inverse design would provide attached flow while the tested diffuser had backflow region. Inverse design studies clarify the effect of the inlet swirl angle, Laval number, specific heat ratio, boundary layer blockage, skew angle, Reynolds number and skin friction coefficient on the diffuser contour generation for a radial pump or compressor stage. The inlet swirl angle was chosen to vary from 15–30°, the inlet Laval number from 0–1.1 and the inlet boundary layer blockage from 0.2% to 5% of inlet diffuser width.
Experimental Cascade Analysis of a Transonic Compressor Rotor Blade Section
Authors: Schreiber H. A. , Starken H.
Published: April 2015

A transonic compressor rotor blade cascade was tested in order to elucidate the flow behaviour in the transonic regime and to determine the performance characteristic in the whole operating range of a rotor blade section. The experiments have been conducted in a transonic cascade wind tunnel, which enables tests even at sonic inlet velocities.

The influence of the upstream Mach number between 0.8 and 1.1 and the inlet flow angle between choking and stalling of the blade row was investigated. The effect of the axial velocity density ratio (AVDR) could be studied by applying an endwall suction device. Furthermore the level of the shock losses was determined from a wake analysis.

A final comparison of cascade losses and those of the corresponding rotor blade element shows good agreement which underlines the applicability of the cascade model in the design of axial flow turbomachines.
Problems Experienced During and After Installation of Gas Compression in UK Southern North Sea
Authors: Simnett A. D.
Published: April 2015

This paper relates the problems encountered with the operation of series configuration gas compression since its introduction in 1976 to the Leman Gas Field in the UK Southern North Sea gas transmission system.

Various topics are addressed with the problem described and the adopted solution. Although solutions to these problems can be achieved by different methods, it is hoped that by relating these experiences, future operators embarking on offshore compression can take account during design stages and hence dispel the need of expensive modifications to plant offshore.
Development of Controlled Diffusion Airfoils for Multistage Compressor Application
Authors: Hobbs D. E. , Weingold H. D.
Published: April 2015

A series of Controlled Diffusion Airfoils has been developed for multistage compressor application. These airfoils are designed analytically to be shock free at transonic Mach number and to avoid suction surface boundary layer separation for a range of inlet conditions necessary for stable compressor operation. They have demonstrated, in cascade testing, higher critical Mach number, higher incidence range, and higher loading capability than standard series airfoils designed for equivalent aerodynamic requirements. These airfoils have been shown, in single and multistage rig testing, to provide high efficiency, high loading capability, and ease of stage matching, leading to reduced development costs and improved surge margin. The Controlled Diffusion Airfoil profile shapes tend to have thicker leading and trailing edges than their standard series counterparts, leading to improved compressor durability.
Erosion Pattern of Twisted Blades by Particle Laden Flows
Authors: Hamed A. , Fowler S.
Published: April 2015

This paper presents the results of a study to predict turbomachine blade erosion by particle laden flows. Using statistical methods, this work combines particle trajectory calculations with experimental erosion data to determine the erosion of blades. The results of the calculations are presented to show the different patterns of blade material removal distribution over the surface of twisted stator blades for different particle sizes.
The Relative Eddy in Axial Turbine Rotor Passages
Authors: Dring Robert P. , Joslyn H. David
Published: April 2015

It has been observed that strong radially outward flow can be present on the pressure surface of an axial turbine rotor blade. This paper demonstrates that the relative eddy plays a major role in producing this radial flow. An analysis of the relative eddy indicates that it can explain observed trends both with blade incidence as well as with spanwise location on the blade. Suggestions are offered as to how the turbine designer might exercise some control over this aerodynamic mechanism.
Component Qualification and Initial Build of the AGT 100 Advanced Automotive Gas Turbine
Authors: Johnson Richard A.
Published: April 2015

In advance of initial dynamometer testing of the AGT 100 engine, all prime components and subsystems were bench/rig tested. Included were compressor, combustor, turbines, regenerator, ceramic components, and electronic control system. Results are briefly reviewed. Initial engine buildup was completed and rolled-out for test cell installation in July 1982. Shakedown testing included motoring and sequential firing of the combustor’s three fuel nozzles.
Drop Size Measurements in Evaporating Realistic Sprays of Emulsified and Neat Fuels
Authors: Dodge Lee G. , Moses Clifford A.
Published: April 2015

A comparative study has been performed of the drop-size distribution of sprays of emulsified and neat distillate-type aviation fuels at elevated temperatures (308K to 700K) and pressures (101 kPa to 586 kPa). All drop-size data were obtained with a Malvern Model 2200 Particle Sizer based on the forward angle diffraction pattern produced by the drops when illuminated by a collimated HeNe laser beam. Fuels included a standard multicomponent jet fuel, Jet-A, and a single component fuel, hexadecane, in both neat form and emulsified with 20 percent (by vol.) water and 2 percent (by vol.) surfactant. The initial breakup and atomization of a neat and emulsified fuel were quite similar at all conditions, and the evaporation rates appeared similar at various temperatures for pressures at or below about 300 kPa. At higher pressures with elevated temperatures the emulsified fuels of both types produce drops of significantly smaller Sauter mean diameter than the neat fuels as distance from the nozzle increases. These results are consistent with the microexplosion hypothesis, but there could also be alternative explanations. A detailed computer model which predicts heat up rates, steady state drop temperatures, evaporation rates, and drop trajectories has been used to help interpret the results. An additional point which has been observed is that the initial Sauter mean diameter produced with constant differential nozzle pressure is dependent on the air pressure with an exponent of about −0.4, i.e., SMD ∼ Pair−0.4. Some recent correlations often quoted omit the pressure (density) of air term.
On the Transient Interaction of Centrifugal Compressors and Their Piping Systems
Authors: Sparks Cecil R.
Published: April 2015

The problems of surge and other low frequency pulsation phenomena in centrifugal compressor are described in terms of both machine (head curve) characteristics and the flow impedance characteristics of its attached piping. Flow stability criteria are presented in terms of net modal damping, as the combination of piping acoustic damping and equivalent negative damping of the compressor in the surge region of its performance curve. Surge and instability frequencies are related to acoustic reactance of the piping system. Finally, theoretical concepts are verified both by electrical analog models and by field and laboratory data on real compressors.

This paper provides some new and significant findings on the dynamic interaction of centrifugal compressors with piping systems, and describes the basic phenomena underlying these interactions. Good agreement is shown between predicted and measured surge frequencies, and for those termed “piping resonance surge” produced by high flow offsets or flat spots in the head curve.
Compact Heater Concept for Closed Power Cycles
Authors: Green Leon
Published: April 2015

The largest component of the closed-cycle gas turbine system is the heater. Many industrial and all non-stationary applications of the CCGT will require a compact combustor and heat-transfer system. This paper describes a heater concept consisting essentially of a deep, pressurized, fluidized-bed heat exchanger into which the products of partial fuel-air combustion are discharged from multiple pre-burners at the lower periphery of the bed. The combustion system can employ any clean fluid fuel, including a deeply de-ashed coal-water slurry. Tangential injection of the fuel-rich products from the pre-burners and complete combustion with the fluidizing air generate additional gas plus a strong tangential velocity component at the boundary of the final combustion zone, a region of intense mixing. Natural convection due to heat released in this annular zone adds an upward component at the wall. These velocity components, superposed upon the upward velocity of the fluidizing air, produce a helical upward flow at the periphery of the bed, with a net downward axial flow at its core. The additional scrubbing action of this combustion-driven flow enhances the rate of heat transfer to the heat-exchanger surfaces beyond the level (already high) characteristic of conventional fluidized beds. The properties of the ceramic bed particles and the auxiliary flow equipment are discussed briefly.
Squeeze-Film Damper Technology: Part 2 — Experimental Verification Using a Controlled-Orbit Test Rig
Authors: Tecza J. A. , Giordano J. C. , Zorzi E. S. , Drake S. K.
Published: April 2015

This paper is a companion to “Squeeze-Film Damper Technology, Part 1,” which covered an analytic approach and computer program for squeeze-film damper performance prediction. This paper describes a series of damper tests in which a controlled-orbit rig is used to explore squeeze-film damper behavior for representative gas turbine damper geometries and to verify and calibrate the damper analysis program. Test results for both locally end-sealed (hole fed and drained) and globally sealed (groove fed and drained) dampers are presented, along with performance predictions for those test points made using the software analysis. In particular, the effects of feeder hole flow resistance, feed groove geometry, and fluid inertia on damper performance are discussed and illustrated.
Effectiveness Measurements for a Cooling Film Disrupted by a Single Jet
Authors: Button B. L.
Published: April 2015

Experimental measurements of the effectiveness downstream of a slot airflow with the jet airflow normal to the wall have been performed in a wind tunnel. The separate and combined contributions of the slot and jet airflows to the effectiveness are established for a range of airflow conditions relevant to gas turbine combustors. Generally, the jet reduces the effectiveness. The major interactions between the airflows occur just downstream of the jet. Visualisation studies using tufts and velocity and turbulence intensity profiles are reported.
Testing of a Full-Scale Staged Combustor Operating With a Synthetic Liquid Fuel
Authors: McVey J. B. , Kenndy J. B. , Sederquist R. A. , Angello L. A.
Published: April 2015

The staged rich-lean gas turbine engine combustion system has been the subject of numerous investigations directed at substantiating the capability of burning nitrogen bearing fuels without producing high emissions of nitric oxides. Many tests conducted to evaluate the potential of this combustion system when operating with coal-derived liquid fuels have been conducted using subscale burners because of the high cost and limited quantities of fuel available (e.g., (1–3). Questions arise as to the applicability of the subscale test findings when predicting the capabilities of full scale devices. In order to evaluate the efficacy of applying subscale results to large scale devices, a program was undertaken to test a 25-cm dia staged rich-lean combustor having similar characteristics to a previously tested 12.5-cm dia combustor and to identify areas where scale effects prove to be critical.
Heat Transfer Characteristics for Jet Array Impingement With Initial Crossflow
Authors: Florschuetz L. W. , Metzger D. E. , Su C. C.
Published: April 2015

Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. In addition to the crossflow which originates from the jets following impingement, an initial crossflow is present which approaches the array through an upstream extension of the channel. The temperature of the initial crossflow air may differ from the jet air temperature. The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present. Nusselt numbers and dimensionless adiabatic wall temperatures resolved to one streamwise jet hole spacing were experimentally determined for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity. These are presented and discussed relative to the flow and geometric parameters.
Measured and Calculated Wall Temperatures on Air-Cooled Turbine Vanes With Boundary Layer Transition
Authors: Liebert Curt H. , Gaugler Raymond E. , Gladden Herbert J.
Published: April 2015

Convection cooled turbine vane metal wall temperatures experimentally obtained in a hot cascade for a given one-vane design were compared with wall temperatures calculated with TACT1 and STAN5 computer codes which incorporated various models for predicting laminar-to-turbulent boundary layer transition. Favorable comparisons on both vane surfaces were obtained at high Reynolds number with only one of these transition models. When other models were used, temperature differences between calculated and experimental data obtained at the high Reynolds number were as much as 14 percent in the separation bubble region of the pressure surface. On the suction surface and at lower Reynolds number, predictions and data unsatisfactorily differed by as much as 22 percent. Temperature differences of this magnitude can represent orders of magnitude error in blade life prediction.
Metering Cooling Flows in the Water-Cooled Gas Turbine
Authors: Grondahl C. M.
Published: April 2015

Metering of coolant flow to bucket cooling passages in the water-cooled gas turbine rotor was experimentally evaluated. Through water flow per cooling passage is approximately one gallon per hour and rotor “g” field is approximately 20,000 g’s, the water-cooled gas turbine depends on uniform water distribution. Measurements indicative of water distribution accuracy to eight buckets and representative cooling passages in each bucket were made in separate tests. Rotor water pressure measurements were made at both metering elements and compared to static differential pressure data. This work is part of the technology development and component verification testing of an advanced water-cooled gas turbine, firing at 2600°F (1427°C) being performed by General Electric under Phase II of the U.S. Department of Energy (DOE) funded High Temperature Turbine Technology (HTTT) Program.
Comparison of Predicted and Experimental External Heat Transfer Around a Film Cooled Cylinder in Crossflow
Authors: Stepka Francis S. , Gaugler Raymond E.
Published: April 2015

Calculations were made of the film cooling provided by rows of holes around the circumference of a cylinder in crossflow and the results were compared to experimental data obtained from a NASA grant to Purdue University. The calculations and experimental data were for conditions that simulate most of those that are typical of air cooled turbine vane leading edges. Injection was from single and multiple rows of holes located at different angular locations from the stagnation line. The holes in the rows were angled normal to the flow direction and at a 25 degree angle to the cylinder wall. The calculations and experimental data were for several constant values of blowing ratios for all rows and for different blowing ratios for each row, representing a simulation of a common coolant plenum supply to multiple rows of holes. The calculations were made using a finite difference boundary layer code, STAN5, developed under NASA contract with Stanford University and modified at the NASA Lewis Research Center. Contrary to initial expectations that injection would trip the boundary layer flow into the turbulent regime, the results indicated that the high free stream acceleration apparently kept the flow laminar for holes in the first 45 degrees past stagnation. The trend in Stanton number reduction due to coolant injection was predicted with generally good agreement at the lower blowing rates, but for multiple rows of holes, agreement was poor beyond the first row.
Mixing and Fuel Atomisation Effects on Premixed Combustion Performance
Authors: Andrews G. E. , Abdul Aziz M. M. , Al-Dabbagh N. A.
Published: April 2015

The main objective was to compare a flame stabiliser at constant pressure loss and identical isothermal aerodynamics with three modes of fuel injection: premixed, direct propane injection and direct kerosene injection. A Jet Mixing type of flame stabiliser was used at simulated gas turbine primary conditions. The influence of gaseous mixing effects was to deteriorate the combustion efficiency solely by increasing the CO emissions and to increase the NOx emissions. The flame stability was increased and low CO emissions were achieved at weaker mixtures. Liquid fuel atomisation effects resulted in a further deterioration in combustion efficiency due solely to un-burnt hydrocarbons. However, the NOx emissions were reduced indicating that local stoichiometric burning around single droplets does not occur.
The Use of Production Hardware for the Development of Control Laws
Authors: Learman I. , Young N. J. B.
Published: April 2015

The advent of large scale integration techniques into electronics has had a dramatic effect on the technology of engine control systems and accompanying this change has been the wider use of digital computational techniques to replace functions previously performed in analogue electronic technology and even by mechanical means. The industry has thereby benefited by smaller and more powerful electronic control systems but at the same time had to deal with costly and potentially difficult to manage technologies associated with the generation of software appropriate for these controllers.
Improved Combustion Turbine Efficiency With Reformed Alcohol Fuels
Authors: Davies Donald G. , Woodley Neil H. , Foster-Pegg Richard W. , Karpuk Michael E.
Published: April 2015

A high-efficiency, alcohol-burning combustion turbine system is described. The system’s high efficiency is the result of an endothermic catalytic reforming of the alcohol fuel using exhaust gas waste heat. A performance analysis of a catalytic reformer for methanol, methanol/water, and ethanol/water mixtures is presented. System performance predictions for a Westinghouse 501D (100 MWe) combustion turbine show significant improvements in efficiency and power over distillate fuel and potential reductions in NOx emissions. An economic comparison with distillate fuel indicates the time when a reformed alcohol combustion turbine could be feasible.
The Interdependence of Spray Characteristics and Evaporation History of Fuel Sprays in Stagnant Air
Authors: Chin J. S. , Durrett R. , Lefebvre A. H.
Published: April 2015

A simple calculation method based on an evaporation analysis proposed previously [1] [2] is used to predict the variation of JP-5 fuel spray characteristics (median drop diameter, Dm, and drop-size distribution parameter, n) with time during evaporation in stagnant hot air. The method takes full account of transient effects occurring during the heat-up period. The results show that Dm increases with time, and so also does n, indicating that the drop-size distribution narrows with passage of time. The time to vaporize any given fraction of the spray mass is found to be proportional to D2mo. The effect of the initial value of n, no, is that a spray having a large value of no will reach its 90% evaporation point faster, but a smaller value of no will give a shorter 20% evaporation time. Based on these calculations, a general method for estimating the time required for any liquid fuel to attain any given percentage of spray mass evaporation in stagnant air is proposed.
Entropy Production Rates From Viscous Flow Calculations: Part I — A Turbulent Boundary Layer Flow
Authors: Moore John , Moore Joan G.
Published: April 2015

A procedure for obtaining entropy production rates from viscous flow calculations is described. The method is based on process thermodynamics; it allows loss production to be calculated in “irreversible equilibrium processes.”

The two-dimensional turbulent boundary layer of Samuel and Joubert is considered. Mean rates of entropy production are evaluated from measured data using rates of dissipation and rates of increase of turbulence kinetic energy. Calculations performed with the Moore Cascade Flow Program give good agreement with mean rates of entropy production and reveal details of the distribution of entropy production throughout the boundary layer. This method is used in Part II to reveal loss sources in calculations for a rectangular elbow.
Entropy Production Rates From Viscous Flow Calculations: Part II — Flow in a Rectangular Elbow
Authors: Moore John , Moore Joan G.
Published: April 2015

Entropy creation is studied in a three-dimensional turbulent flow in a rectangular elbow with 90 degrees of turning. In Part I, a method of evaluating entropy production rates in calculations of viscous flow was described. This method is used here to show where the calculated losses arise in the flow field.

The flow develops strong passage vortices as large shear layers at the inlet develop a streamwise component of vorticity. The entropy production in the shear layers is compared with the entropy creation in the wall boundary layers. The influence of the three-dimensional flow on the distributions of entropy production in the bend is discussed.
Investigation of Fixed-Rake Sampling System for the Assessment of Emission Characteristics of Gas Turbine Engines
Authors: Low H. C. , Dowling A. P.
Published: April 2015

The regulations proposed by the US Environmental Protection Agency to limit the quantity of pollutant gases emitted by aircraft engines allow the exhaust of engines submitted for compliance testing to be sampled by a fixed-multipoint rake. However, the onus is placed on the manufacturer to prove the representativeness of the samples taken in this relatively cheap fashion. To illustrate best possible accuracies, the exhaust of an M45H civil turbofan engine has hen extensively sampled and a computer program has been used to select the optimum configuration of a cruciform rake. The program demanded excellent agreement between the sampling methods and this proved to be the case in actual tests. However, the program also indicates that the errors of a simply designed rake giving area-weighted samples would also be less than 10%. Sampling in the FAA diamond pattern would give rise to a 20% error in CO emissions.
Effect of Relative Velocity Distribution on Efficiency and Exit Flow of Centrifugal Impellers
Authors: Mishina H. , Nishida H.
Published: April 2015

The major problem for designing centrifugal compressors is to attain high stage efficiency as well as a wide operating range. High stage efficiency is customarily attained by the optimization of design parameters using a one-dimensional loss analysis including the relationship between the flow behavior and total pressure losses for limited types of compressors.
Solution of Particulate Viscous Flow in a Radial Inflow Turbine
Authors: Vittal B. V. R. , Tabakoff W.
Published: April 2015

The presence of solid particles in turbomachinery flow affects the component performance as well as its life. The subject of particulated flows can be broadly divided into three parts, namely, particle trajectories, the effect of particles on the aerodynamics of flow and material erosion. The first two aspects are investigated in this paper taking into account the viscosity of the carrier fluid.

The Lagrangian formulation is adopted for the particles, whereas the Eulerian approach is used for the continuous phase. The effect of particles is incorporated as interphase force terms in the fully incompressible stream function-vorticity form of the Navier-Stokes equations. The field analysis is based on the numerical integration of this equation over the rotor blade to blade stream channels. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system that suits the most complicated blade geometries. The trajectories of the solid particles are determined including particle impacts with the blades. The particle rebounding velocity and direction after each impact is determined using semi-empirical correlations for the restitution ratios obtained experimentally. The method of analysis is applied to a radial inflow turbine. The effect of particles on the aerodynamics of the flow is studied by analyzing the fluid streamline pattern in the rotor blades with and without solid particles. The analysis is carried out for various particle concentrations.
EAGLE/DTA: A Life Cycle Cost Model for Damage Tolerance Assessment
Authors: Reed Edward J.
Published: April 2015

The U.S. Air Force and Pratt & Whitney Aircraft are currently engaged in developing technology to minimize low-cycle fatigue maintenance requirements in future gas turbine engines. The Life Cycle Cost/Damage Tolerance Assessment (LCC/DTA) program is directed toward furthering technology development in two important areas that relate to the overall life cycle cost of advanced Air Force weapon systems: life cycle cost modeling and analysis, and damage tolerance design (DTD). A major goal of the LCC/DTA program is to establish hot-section disk design criteria specifying acceptable levels for life and maintenance actions based on minimum life cycle cost. This paper discusses the methodology developed to evaluate the weapon system LCC impact of designing to damage tolerance criteria.
Theoretical and Experimental Investigation of KWU’s Most Recent HP/IP Steam Turbine Blade
Authors: Purcaru B.-T. , Giess P.-A.
Published: April 2015

A new profile has recently been developed at Kraftwerk-Union (KWU), West Germany, to increase the efficiency of todays high pressure (HP) and intermediate pressure (IP) steam turbines. The profile was described using analytical functions. Therefore, the contour could be easily modified until the surface pressure distributions, which were calculated using a singularity method, fit a desired distribution. The experiments for the aerodynamic cascade data and blade surface pressure distributions were performed at the German Aerospace Research Establishment (DFVLR), Institute for Experimental Fluid Dynamics in Goettingen. Computer codes developed at the Institute enabled additional theoretical studies. The codes used in the study included a time-marching method for calculating the 2D-flow field and an integral method for calculating the boundary layer. Both theoretical and experimental results are discussed and compared with efficiency measurements derived from a multistage testrig at KWU.
Use of Pyrolysis-Derived Fuel in a Gas Turbine Engine
Authors: Kasper J. M. , Jasas G. B. , Trauth R. L.
Published: April 2015

Combustion of a pyrolytically derived oil has been demonstrated in a J69-T-29 gas turbine combustor rig. The fuel was derived from agricultural and forest products/wastes through a pyrolysis conversion process which yields the oil and a residual char. The char was ground to a mean size of 25 microns and mixed with the oil and JP-4 in additional combustor rig tests. Analysis of the oil and char showed that both have hydrogen/carbon ratios less than 1.0 for the combustible components. The oil has a water content of 29%, a room temperature viscosity of 250 cS, and a pH of 2.9. The combustion system of the J69 consists of an annular combustor and a centrifugal fuel injector rotating at shaft speed. The centrifugal fuel injector can use slurry fuels without clogging and provides good atomization with viscous fuels. The combustor rig was operated at pressures and temperatures lower than those of the engine, and JP-4 was used as a baseline fuel. Test results indicate that use of pyrolytic oil will result in engine combustion efficiencies of over 99%. The pyrolytic oil may also be used as a supplement to JP-4. Additional development will be necessary to use the pyrolytic char as a gas turbine fuel.
Titanium alloy as a potential low radioactivation vacuum material
Authors: Kamiya Junichiro , Hikichi Yusuke , Kinsho Michikazu , Ogiwara Norio , Fukuda Mitsuhiro , Hamatani Noriaki , Hatanaka Kichiji , Kamakura Keita , Takahisa Keiji
Published: April 2015

For the vacuum systems of high-intensity beam accelerators, low radioactivation materials with good vacuum characteristics and high mechanical strength are required. The titanium alloy Ti-6Al-4V was investigated as a potential low activation vacuum material with high mechanical strength for the fabrication of vacuum components, particularly the flanges of beam pipes, in the J-PARC 3 GeV synchrotron. The dose rate of Ti-6Al-4V when irradiated by a 400 MeV proton was observed to decrease more rapidly than that of stainless steel. Furthermore, the generated radioactive isotopes were nuclides with relatively short half-lives. The outgassing rate per unit area of Ti-6Al-4V was approximately 10−8 Pa m3/s m2 after pumping for 100 h, which is the same as the typical value for stainless steel. Additionally, the hydrogen concentration in bulk Ti-6Al-4V was reduced to approximately 1 ppm by vacuum firing at 700 °C for 9 h; the mechanical strength was not reduced by this process. These results indicate that Ti-6Al-4V is a good candidate for use as a low activation vacuum material with high mechanical strength.
Quantitative rheological model selection: Good fits versus credible models using Bayesian inference
Authors: Freund Jonathan B. , Ewoldt Randy H.
Published: April 2015

The more parameters in a rheological constitutive model, the better it tends to reproduce available data, though this does not mean that it is necessarily better justified. Good fits to data are only part of model selection. We develop a Bayesian inference approach that rigorously balances closeness to data against both the number of model parameters and their a priori uncertainty. The analysis reflects a basic principle: Models grounded in physics will enjoy greater generality and perform better away from where they are calibrated. In contrast, relatively empirical models can provide comparable fits, but their a priori uncertainty is penalized. We demonstrate the approach by computing the best-justified number of modes for a multimode Maxwell model (MMM) to describe the dynamic shear moduli G′(ω), G″(ω) of a synthetic polymer network with transient crosslinks (polyvinyl alcohol with sodium tetra-borate). It is shown that a corresponding array of spring-pots, arranged as a parallel array of fractional-Maxwell model elements, is less credible. In contrast, for a biopolymer gluten dough we show that the MMM, irrespective of number of modes, is far less credible than a critical-gel/Rouse model (CGRM), which with its firmer physical basis provides a more credible model. This is true even though the MMM provides a closer fit to the data than the CGRM for the gluten system. Though quantitative, this formulation does not fully supplant user judgment. However, unlike most model fitting/selection approaches, it requires specific, quantifiable, and potentially debatable quantification of this judgment, and thus it provides a rigorous, repeatable assessment of model viability. Models are supported (or not) given numerical input, not vague assertions.
Modeling the rheological behavior of waxy crude oils as a function of flow and temperature history
Authors: Mendes Rafael , Vinay Guillaume , Ovarlez Guillaume , Coussot Philippe
Published: April 2015

The solidification of waxy components during the cool down of waxy crude oils in pipelines may provide complex yield stress fluid behavior with time-dependent characteristics, which has a critical impact for predicting flow restart after pipeline shut-in. Here, from a previous set of data at a local scale with the help of Magnetic Resonance Imaging and a new full set of data for various flow and temperature histories, we give a general picture of the rheological behavior of waxy crude oils. The tests include start flow tests at different velocities or creep tests at different stress levels, abrupt changes of velocity level, steady flow, after cooling under static or flowing conditions. We show that when the fluid has been cooled at rest it forms a structure that irreversibly collapses during the startup flow. Under these conditions, the evolution of the apparent viscosity mainly depends on the deformation undergone by the fluid for low or moderate deformation and starts to significantly depend on the shear rate for larger values. Even the (apparent) flow curve of statically cooled waxy crude oils was observed to be dependent on the flow history, more specifically on the maximum shear rate experienced by the material. After being sufficiently sheared, i.e., achieving an equilibrium state, the rheological behavior is that of a simple liquid for shear rates lower than the maximum historical one. A model is proposed to represent those trends experimentally observed. In contrast with most previous works in that field, the model is built without any a priori assumption based on classical behavior of a class of fluids. Finally, it is shown that this model predicts the flow characteristics of these materials under more complex flow histories (sweep tests, sudden shear rate decrease) much better than the so far most often used (Houska) model.
Validity of a Trunk-Mounted Accelerometer to Measure Physical Collisions in Contact Sports
Authors: Wundersitz Daniel W.T. , Gastin Paul B. , Robertson Samuel J. , Netto Kevin J.
Published: April 2015

Context:

Accelerometer peak impact accelerations are being used to measure player physical demands in contact sports. However, their accuracy to do so has not been ascertained.

Purpose:

To compare peak-impact-acceleration data from an accelerometer contained in a wearable tracking device with a 3-dimensional motion-analysis (MA) system during tackling and bumping.

Methods:

Twenty-five semielite rugby athletes wore a tracking device containing a 100-Hz triaxial accelerometer (MinimaxX S4, Catapult Innovations, Australia). A single retroreflective marker was attached to the device, with its position recorded by a 12-camera MA system during 3 physical-collision tasks (tackle bag, bump pad, and tackle drill; N = 625). The accuracy, effect size, agreement, precision, and relative errors for each comparison were obtained as measures of accelerometer validity.

Results:

Physical-collision peak impact accelerations recorded by the accelerometer overestimated (mean bias 0.60 g) those recorded by the MA system (P < .01). Filtering the raw data at a 20-Hz cutoff improved the accelerometer’s relationship with MA data (mean bias 0.01 g; P > .05). When considering the data in 9 magnitude bands, the strongest relationship with the MA system was found in the 3.0-g or less band, and the precision of the accelerometer tended to reduce as the magnitude of impact acceleration increased. Of the 3 movements performed, the tackle-bag task displayed the greatest validity with MA.

Conclusions:

The findings indicate that the MinimaxX S4 accelerometer can accurately measure physical-collision peak impact accelerations when data are filtered at a 20-Hz cutoff frequency. As a result, accelerometers may be useful to measure physical collisions in contact sports.
Jump-Squat Performance and Its Relationship With Relative Training Intensity in High-Level Athletes
Authors: Jiménez-Reyes Pedro , Pareja-Blanco Fernando , Balsalobre-Fernández Carlos , Cuadrado-Peñafiel Víctor , Ortega-Becerra Manuel A. , González-Badillo Juan J.
Published: April 2015

Purpose:

To examine the relationship between the relative load in full squats and the height achieved in jump-squat (JS) exercises and to determine the load that maximizes the power output of high-level athletes.

Method:

Fifty-one male high-level track-and-field athletes (age 25.2 ± 4.4 y, weight 77. ± 6.2 kg, height 179.9 ± 5.6 cm) who competed in sprinting and jumping events took part in the study. Full-squat 1-repetition-maximum (1-RM) and JS height (JH) with loads from 17 to 97 kg were measured in 2 sessions separated by 48 h.

Results:

Individual regression analyses showed that JH (R2 = .992 ± .005) and the jump decrease (JD) that each load produced with respect to the unloaded countermovement jump (CMJ) (R2 = .992 ± 0.007) are highly correlated with the full-squat %1-RM, which means that training intensities can be prescribed using JH and JD values. The authors also found that the load that maximizes JS’s power output was 0%RM (ie, unloaded CMJ).

Conclusions:

These results highlight the close relationship between JS performance and relative training intensity in terms of %1-RM. The authors also observed that the load that maximizes power output was 0%1-RM. Monitoring jump height during JS training could help coaches and athletes determine and optimize their training loads.