bluuebunny/crossref_metadata_2025 huggingface dataset:
Implanted Component Faults and Their Effects on Gas Turbine Engine Performance
Authors: MacLeod J. D. , Taylor V. , Laflamme J. C. G.
Published: March 2015

Under the sponsorship of the Canadian Department of National Defence, the Engine Laboratory of the National Research Council of Canada (NRCC) has established a program for the evaluation of component deterioration on gas turbine engine performance. The effort is aimed at investigating the effects of typical in-service faults on the performance characteristics of each individual engine component. The objective of the program is the development of a generalized fault library which will be used with fault identification techniques in the field, to reduce unscheduled maintenance.

To evaluate the effects of implanted faults on the performance of a single spool engine, such as an Allison T56 turboprop engine, a series of faulted parts were installed. For this paper the following faults were analyzed:

a) 1st stage turbine nozzle erosion damage,

b) 1st stage turbine rotor blade untwist,

c) compressor seal wear,

d) 1st and 2nd stage compressor blade tip clearance increase.

This paper describes the project objectives, the experimental installation, and the results of the fault implantation on engine performance. Discussed are performance variations on both engine and component characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.
Spray Drop Size and Velocity Measurements in a Swirl-Stabilized Combustor
Authors: Chehroudi B. , Ghaffarpour M.
Published: March 2015

A pressure-swirl fuel nozzle generating a hollow-cone spray with nominal cone angle of 30 degrees is used in a swirl-stabilized combustor. The combustor is circular in cross section with swirl plate and fuel nozzle axes aligned and coinciding with the axis of the chamber. Kerosene is injected upward inside the chamber from the fuel nozzle. Separate swirl and dilution air flows are uniformly distributed into the chamber that pass through the honey comb flow straighteners and screens. Calculated swirl number of 1.5 is generated with the design swirl plate exit air velocity of 30 degrees with respect to the chamber axis. Effects of swirl and dilution air flow rates on the shape and stability of the flame are investigated. Stable and classical liquid fuel sheet disintegration zone exists close to the nozzle with no visible light followed by a luminous blue region and a mixed blue/yellow region that subsequently turns into yellow for most of the part in the flame. A Phase Doppler Particle Analyzer (PDPA) is used to measure drop size, mean and rms axial velocity for two cases of with and without combustion at six different axial locations from the nozzle. For the no-combustion case all air and fuel flow rates were kept at the same values as the combusting spray condition. Results for mean axial drop velocity profiles indicate widening of the spray due to combustion while the magnitudes of the peak velocities are slightly increased. No measurements inside the hollow-cone spray are possible due to burning of fuel droplets. Drop turbulence decreases due to combination of increase in gas kinematic viscosity and elimination of small drops at high temperatures. Sauter Mean Diameter (SMD) radial profiles at all axial locations increase with combustion due to preferential burning of small drops.
The Use of Gaseous Fuels on Aero-Derivative Gas Turbine Engines
Authors: Mathieu Philippe , Pilidis Pericles
Published: March 2015

In this paper, the use of various gaseous fuels in aero-derivative gas turbine engines is analysed. The gases investigated are natural gas and three coal synthetic gases of calorific values which are significantly lower than that of natural gas.

The analysis is carried out employing natural gas fuel as a yardstick for comparison. Due to the lower calorific values of synthetic gases, the mass flow balance between compressors and turbines is altered. This in turn affects the matching of the components and the overall performance of a gas turbine engine. The engines examined are a single spool gas generator with a free power turbine and the double engine described in a previous paper.

The main conclusion drawn from this analysis is that, for a given power output, the use of synthetic gases will result in an erosion of surge margins and in a reduction of the overall efficiency of the power plant.
Cyclo-Symmetric Modal Synthesis of Rotating Bladed Disc System
Authors: Zhang Jin , Wang W. L. , Chen X. J.
Published: March 2015

The natural mode analysis of bladed disc system at an arbitrary constant rotational speed is investigated in this paper and the large deformation effect caused by the pretorsion of the blades is also considered. The computational method of group theory is employed in substructure technique and equilibrium position and stress distribution of the bladed disc system in centrifugal field are obtained through simultaneous iteration, further more, the initial stress stiffness matrix, the large deformation stiffness matrix and the corresponding rotating natural frequencies and modal shapes are determined. Because the large deformation effect of the blades is considered and all the interface degrees of freedom between the substructures can be eliminated in the present method, the computation work can be cut down remarkably under the precondition that the computational accuracy is ensured. It shows practically that the substructure simultaneous iteration method presented in this paper has a good convergency and greatly reduces the computation work.
Two-Phase Flow Correlations in Air/Oil Systems of Aero Engines
Authors: Zimmermann H. , Kammerer A. , Fischer R. , Rebhan D.
Published: March 2015

A strategy is outlined on how to introduce two-phase flow correlations into air/oil system calculations for aero engines.

The importance of two-phase flow effects is highlighted by demonstrating their particular significance for the high altitude performance of a vent system.

For air/oil mixtures very little can be obtained from the literature and correlations derived from air/water test results have to be corrected. For critical flow conditions in restrictors an improved method is developed. Some test data obtained for air/oil mixtures show, that the proposed correlations agree fairly well.

Furthermore, it is shown how numerical methods for this complex field of fluid dynamics can be used in the future by the example of phase demixing by centrifugal forces.
The Effect of Blade Curving on Flow Characteristics in Rectangular Turbine Stator Cascades With Different Incidences
Authors: Wang Zhongqi , Han Wanjin , Xu Wenyuan
Published: March 2015

In a low speed plane cascade tunnel, the outlet flow fields and the static pressure distributions on blade surfaces of the turbine rectangular stator cascades with a small aspect ratio (s=0.68) were measured in detail. The experimental results show that the blade curving can form the negative gradient of static pressure along the blade height in the lower region of the cascade and the positive one in the upper region. This can lead to the reduction of the intensity of the streamwise vortices and the aerodynamic loading on both sides of the blades and the endwalls. Therefore, the end crosswise secondary flow losses are decreased considerably. The use of the curvilinear leaned blades can not only improve the flow characteristics in the stator cascades, but also provide good inlet conditions for rotor cascades.
The Design and Development of an Electrically Operated Fuel Control Valve for Industrial Gas Turbines
Authors: Salsi A. G. , Bhinder F. S.
Published: March 2015

Industrial gas turbines operate over a wide range of combinations of loads and speeds. The fuel control valve must be designed to cover the entire range precisely. The design of an electrically operated fuel control valve is described and comparison between the predicted and measured performance characteristics is shown.
An Analytical Method for the Fault Diagnosis of Axial Multistage Compressors
Authors: Massardo Aristide
Published: March 2015

A deterministic approach for troubleshooting in axial multistage flow compressors, that is to say, the solution of the diagnostic or inverse problem is presented.

The approach utilizes a model which is capable of predicting the compressor performance with and without faults — solution of analysis or direct problems — previously developed and tested in several applications. The diagnostic problem solution, where the actual compressor performance is known, allows the type, level and position of a fault to be determined.

The novel method is presented and described in detail. The possibility to integrate this deterministic approach with heuristic diagnostic procedures, to take into account more complex fault configurations, is also discussed.
Turbulence Measurements in a Centrifugal Pump With a Synchronously Orbiting Impeller
Authors: Flack Ronald D. , Miner Steven M. , Beaudoin Ronald J.
Published: March 2015

Turbulence profiles were measured in a centrifugal pump with an impeller with backswept blades using a two directional laser velocimeter. Data presented includes radial, tangential, and cross product Reynolds stresses. Blade to blade profiles were measured at four circumferential positions and four radii within and one radius outside the four bladed impeller. The pump was tested in two configurations; with the impeller running centered within the volute, and with the impeller orbiting with a synchronous motion (ε/r2 = 0.016). Flow rates ranged from 40% to 106% of the design flow rate. Variation in profiles among the individual passages in the orbiting impeller were found. For several regions the turbulence was isotropic so that the cross product Reynolds stress was low. At low flow rates the highest cross product Reynolds stress was near the exit. At near design conditions the lowest cross product stress was near the exit, where uniform flow was also observed. Also, near the exit of the impeller the highest turbulence levels were seen near the tongue. For the design flow rate, inlet turbulence intensities were typically 9% and exit turbulence intensities were 6%. For 40% flow capacity the values increased to 18% and 19%, respectively. Large local turbulence intensities correlated with separated regions. The synchronous orbit did not increase the random turbulence, but did affect the turbulence in the individual channels in a systematic pattern.
Development of a Set of Equations for Incorporating Disk Flexibility Effects in Rotordynamical Analyses
Authors: Flowers George T. , Ryan Stephen G.
Published: March 2015

Rotordynamical equations that account for disk flexibility are developed. These equations employ free – free rotor modes to model the rotor system. Only transverse vibrations of the disks are considered, with the shaft/disk system considered to be torsionally rigid. Second order elastic foreshortening effects that couple with the rotor speed to produce first order terms in the equations of motion are included. The approach developed in this study is readily adaptable for usage in many of the codes that are current used in rotordynamical simulations. The equations are similar to those used in standard rigid disk analyses but with additional terms that include the effects of disk flexibility. An example case is presented to demonstrate the use of the equations and to show the influence of disk flexibility on the rotordynamical behavior of a sample system.
Quasi-Three-Dimensional Characteristics Method for a Supersonic Compressor Rotor
Authors: Bölcs A. , Tsamourtzis V.
Published: March 2015

A new quasi-3D characteristics method has been developed to calculate the supersonic flow in a compressor rotor on an axisymmetric stream surface with variable radius and stream tube thickness. The method is valid for supersonic inlet flow with an attached shock wave at the blade leading edge where the inlet Mach number and flow angle are related by the unique incidence condition. On the basis of the quasi-3D characteristics method, a simple quasi-3D method has also been derived that calculates the unique incidence condition and the Mach number distribution on the suction side of the profile for a given stream surface and stream tube thickness. The reliability of the simple method is established by comparing results with those obtained by Denton’s time-marching method as well as those from the quasi-3D characteristics method. Systematic calculations performed using the simple quasi-3D method show the effects of varying the geometrical parameters of the cascade for different stream tube thickness and stream surface radius evolutions through the rotor.
The Role of Tip Clearance in High-Speed Fan Stall
Authors: Adamczyk J. J. , Celestina M. L. , Greitzer E. M.
Published: March 2015

A numerical experiment has been carried out to define the near stall casing endwall flow field of a high-speed fan rotor. The experiment used a simulation code incorporating a simple clearance model, whose calibration is presented. The results of the simulation show that the interaction of the tip leakage vortex and the in-passage shock plays a major role in determining the fan flow range. More specifically, the computations imply that it is the area increase of this vortex as it passes through the in-passage shock, which is the source of the blockage associated with stall. In addition, for fans of this type, it is the clearance over the forward portion of the fan blade which controls the flow processes leading to stall.
The Effect of Tip Leakage Flow on Part-Load Performance of a Mixed-Flow Pump Impeller
Authors: Goto Akira
Published: March 2015

The flow phenomena around the positive slope region of the head-flow characteristic were investigated experimentally on a mixed-flow pump impeller at various tip clearances for both shrouded and unshrouded cases. A positively-sloped head-flow characteristic (abrupt decrease in pressure head) was caused by the onset of extensive flow separation in the impeller at the casing-suction surface corner. The corner separation in unshrouded cases appeared at much lower flow rate than the shrouded case due to the favorable effect of the tip leakage flow which displaced the wake region away from the corner. The interaction between the tip leakage flows and secondary flows and the formation of the wake regions in shrouded and unshrouded cases were explained based on experimental observation and computations by the Dawes’ 3-D Navier-Stokes code. In the shrouded case, the flow rate, at which an abrupt decrease in pressure head appeared, was lowered substantially by introducing a leakage flow through a slit made between the shroud and the blade tip. Inlet recirculation was triggered by the corner separation and developed more gradually for larger tip clearances. Both the increased loss, due to the extensive flow separation, and the decreased Euler’s head, due to the abrupt change in flow pattern caused by the inlet recirculation, were responsible for the generation of positively-sloped head-flow characteristic in the unshrouded case when the tip clearance was small, while the increased loss was the primary factor in the shrouded case.
Influence of Unsteady Effects on the Measurements in a Transonic Axial Compressor
Authors: Paulon Jacques , Zhang Zhifang , Jia Pingfang , Meng Jingfei
Published: March 2015

Interaction phenomena between rotor and stator are unavoidable in advanced compressors and their effects increase with the performances of the turbomachines.

Until now, it was not possible to quantify the interaction effects, but with the development of 3-D unsteady computation codes in a complete stage, it is possible to know, in detail, the flow field through the machine and to make evident and to explain the difficulties encountered in measuring the flow parameters.

A study has been conducted in this way at ONERA, on an axial transonic compressor stage. The computations have been made with a simulation of the losses; in this manner, the overall computed and measured performances of the compressor are the same.

A detailed analysis of the unsteady computation results makes evident, between rotor and stator, large variations of some parameters of the flow as a function of time but also as a function of the axial and tangential relative position of steady probes and stator blades. Unsteady measurements made on another transonic machine confirm the indications given by these computations.
Micromechanical Analysis of the Failure Process in Ceramic Matrix Composites
Authors: Rubinstein Asher A.
Published: March 2015

An analysis of the effectiveness of fiber reinforcement in brittle matrix composites is presented. The analytical method allows consideration of discrete fiber distribution and examination of the development of crack growth parameters on the microscale. The problem associated with bridging zone development is addressed here; therefore, the bridging zone is considered to be smaller than the main preexisting crack, and the small scale approach is used. The mechanics of the reinforcement is accurately accounted for in the process zone of a growing crack. Closed form solutions characterizing the initial failure process are presented for linear and nonlinear force-fiber pullout displacement relationships. The implicit exact solution for the extended bridging zone is presented as well.
Temperature Effects on Fuel Thermal Stability
Authors: Chin J. S. , Lefebvre A. H. , Sun F. T.-Y.
Published: March 2015

The thermal stability characteristics of four kerosine-type fuels are examined using a heated-tube apparatus which allows independent control of fuel pressure, fuel temperature, tube-wall temperature, and fuel flow rate. It is a closed loop system, and fuet flows through the heated tube for periods ranging from 6 to 22 hrs. The deposition rates of carbon on the tube walls are measured by weighing the tube before and after each test.

The results obtained show that tube-wall and fuel temperatures both have a marked influence on deposition rates, the impact of fuel temperature being stronger than that of wall temperature. It is also found that deposition rates increase continuously with increases in tube-wall temperature. This finding contradicts the results of previous studies which had led to the conclusion that deposition rates increase with increase in wall temperature up to a certain value beyond which any further increase in wall temperature causes the deposition rate to decline.
The Transfer Number of Hydrocarbon Liquids
Authors: Odgers J. , Kretschmer D.
Published: March 2015

The Transfer Number (B) assumes considerable importance in the evaporation and diffusion of fuels prior to their combustion. Quite often the Transfer Number is assumed to be a constant for a given fuel. These notes examine the feasibility of this assumption New correlations have been derived for the specific heats of the liquid fuels and their latent heats, over a wide range of temperatures and pressures, as also the effects of pressure upon the boiling characteristics. New prediction techniques are also proposed for critical temperatures and pressures.

Taking note of the above correlations, it becomes possible to assess the values of B for a wide range of combustor operating conditions for any given fuel. The significance of these variations upon the probable combustion behaviour of the fuels is then commented upon. The results show that the assumption of a constant value for B could lead to a significant mis-interpretation of combustion behaviour due to operating conditions and/or the use of different fuels.
Numerical Simulation of Stall Transients of Axial Compression Systems With Inlet Distortion
Authors: Jun Hu , Cai Tang Guo , Min Zhang Hui
Published: March 2015

In this paper, a theory is provided to predict how rotating stall will develop in axial compression systems both with uniform and nonuniform inlet flow, which simulates rotating stall using a time step integration procedure of the two dimensional, compressible and unsteady Euler equation, and also adopts the “actuator disk” to replace the compressor. Using this theory, the effect of various kind of inflow nonuniformity on both rotating stall and recovery transients, and the problem of active control/suppression of rotating stall can be numerically analysed. Rotating stall transients and its growth process both with uniform and with circumferential total pressure distorted inlet flow are investigated in detail. It has been found that rotating stall was preceded by a period in which small amplitude waves travel around the circumference and evolved smothly into rotating satll without sharp change in phase or amplitude both with uniform and with distorted inflow. The throttle ramping and the inlet distortion have crucial effect on the period and stall transients.
Current Status of Industrial and Automotive Ceramic Gas Turbine R&D in Japan
Authors: Nagamatsu Soichi , Mizuhara Kazuyuki , Matsuda Yukio , Iwanaga Akio , Ishiwata Shoji
Published: March 2015

The current status of Japan’s national Ceramic Gas Turbines (CGTs) projects is overviewed.

The Japanese Ministry of International Trade and Industry (MITI) is conducting two national R&D projects on CGT. These include a project on 300kW industrial CGTs for co-generation and mobile power generation use and a project on 100kW CGT for automotive use.

The 300kW project was started in 1988, and is scheduled to develop three kinds of CGTs over nine years. The New Energy and Industrial Technology Development Organization (NEDO) is the main contractor, and three groups of private industries are sub contractors. Three national research institutes are involved in the project to conduct supportive research of ceramic materials and engine components.

The 100kW project has started in 1990, and is scheduled to develop a single shaft automotive CGT over seven years. Petroleum Energy Center (PEC) and JARI are the main contractors with the cooperation of several petroleum and automotive companies.

The goals for the two projects are 42% and higher for thermal efficiency at a turbine inlet temperature of 1350C. Such targets could not be achieved without applying high temperature ceramics to the engine components. Therefore many R&D objectives are directed towards developing the ceramic components which have a higher flexure strength and fracture toughness.

Currently, 300kW base metal gas turbine engines are being developed to prove the design concepts. Blade shapes suitable to ceramics are being studied by the FEM method. Forming and manufacturing large components are also being studied, and some ceramics components have been successfully made.
On the Structure of Turbulent Combusting Unconfined Sprays
Authors: Aggarwal S. K. , Chitre S.
Published: March 2015

Computations are reported on the detailed structures of unconfined turbulent combusting sprays. Favre-averaged gas-phase equations are used and a k-ε-g turbulence closure model is utilized. Using a conserved scalar approach and assuming the form of probability density function to be a clipped Gaussian, the thermodynamic scalar variables are calculated from a partial equilibrium model. The major features of the liquid-phase model are that a stochastic random-walk approach is used to represent the effect of gas-phase turbulence on droplet trajectory and vaporization, the variable-property effects are considered in a comprehensive manner, and a conduction-limit mode is employed to represent the transient liquid-phase processes. This two-phase model is used to study the structure of an unconfined methanol spray flame. Important observation is that the turbulent spray flame structure is significantly different, both quantitatively and qualitatively, from that of the corresponding gaseous diffusion flame. In addition, the spray flame exhibits a strong sensitively to the transient liquid-phase processes. The latter result is interesting since, in an earlier computational study for an evaporating spray, the vaporization behavior for the same liquid fuel indicated only a weak sensitivity to these processes.
Design and Test of a Candidate Topping Combustor for Second Generation PFB Applications
Authors: Garland R. V. , Pillsbury P. W. , Dowdy T. E.
Published: March 2015

Second Generation Pressurized Fluidized Bed Combustion Combined Cycles utilize topping combustion to raise the combustion turbine inlet temperature to the state of the art. Principally for this reason, cycle efficiency is improved over first generation PFB systems. Topping combustor design requirements differ from conventional gas turbine combustors since hot, vitiated air from the PFB is used for both cooling and combustion. In addition, the topping combustor fuel, a hot, low-heating value gas produced from coal pyrolysis, contains ammonia. This NOx-forming constituent adds to the combustor’s unique design challenges.

The candidate combustor is the multi-annular swirl burner (MASB) based on the design described by J.M. Beér. This concept embodies rich-burn, quick quench, and lean-burn zones formed aerodynamically. The initial test sponsored by the Department of Energy, Morgantown, West Virginia, has been completed and the results of that test are presented.
Hitcan for Actively Cooled Hot-Composite Thermostructural Analysis
Authors: Chamis C. C. , Murthy P. L. N. , Singhal S. N. , Lackney J. J.
Published: March 2015

A computer code, HITCAN (HIgh Temperature Composite ANalyzer) has been developed to analyze/design hot metal matrix composite structures. HITCAN is a general purpose code for predicting the global structural and local stress-strain response of multilayered (arbitrarily oriented) metal matrix structures both at the constituent (fiber, matrix, and interphase) and the structure level and including the fabrication process effects. The thermomechanical properties of the constituents are considered to be nonlinearly dependent on several parameters including temperature, stress, and stress rate. The computational procedure employs an incremental iterative nonlinear approach utilizing a multifactor-interaction material behavior model, i.e., the material properties are expressed in terms of a product of several factors that affect the properties. HITCAN structural analysis capabilities (static, load stepping - a multistep static analysis with material properties updated at each step-modal, and buckling) for cooled hot structures are demonstrated through a specific example problem.
Multiobjective Optimization of Rotor-Bearing System With Critical Speeds Constraints
Authors: Shiau Ting Nung , Chang Jer Rong
Published: March 2015

An efficient optimal design algorithm is developed to individually or simultaneously minimize the total weight of shaft and the transsmitted forces at the bearings which play very important roles in designing a rotor-bearing system under the constraints of critical speeds. The cross sectional area of shaft, the bearing stiffness, and the positions of bearings and disks are chosen as the design variables. The dynamic characteristics are determined by applying the generalized polynomial expansion method and the sensitivity analysis is also investigated. For multiobjective optimization, the weighting method (WM), the goal programming method (GPM), and the fuzzy method (FM) are applied. The results show that the present multiobjective optimization algorithm can greatly reduce both the weight of shaft and the forces at the bearings with critical speeds constraints.
Stability and Instability of a Two-Mode Rotor Supported by Two Fluid-Lubricated Bearings
Authors: Muszynska Agnes , Grant John W.
Published: March 2015

This paper is a continuation of the series of papers on application of the improved fluid force model for lightly loaded shafts rotating in a fluid environment. The fluid force model is based on the strength of the circumferential flow. The considered two–mode rotor is supported in two fluid–lubricated bearings, thus it contains two potential sources of instability. The eigenvalue solution predicts thresholds of stability and provide natural frequencies and modes of the system, including the flow–induced modes The nonlinear model of the rotor/bearing system allows for evaluation of parameters of after instability onset self–excited vibrations (whirl and whip). Experimental data illustrate the dynamic phenomena predicted by the model. In particular, they show an undocumented new phenomenon, the simultaneous existence of two whip vibrations with frequencies corresponding to two modes of the rotor. A radial preload of the rotor results in specific changes of the fluid forces (an increase of radial stiffness and reduction of circumferential velocity) providing better stability of the rotor. This effect predicted by the model is illustrated by the experimental data.
Ceramic Component Processing Development for Advanced Gas-Turbine Engines
Authors: McEntire B. J. , Hengst R. R. , Collins W. T. , Taglialavore A. P. , Yeckley R. L. , Bright E. , Bingham M. G.
Published: March 2015

Norton/TRW Ceramics (NTC) is performing ceramic component development as part of the DOE-sponsored Advanced Turbine Technology Applications Project (ATTAP). NTC’s work is directed at developing manufacturing technologies for rotors, stators, vane-seat platforms and scrolls. The first three components are being produced from a HIPed Si3N4, designated NT154. Scrolls were prepared from a series of siliconized silicon-carbide (Si-SiC) materials designated NT235 and NT230. Efforts during the first three years of this five-year program are reported. Developmental work has been conducted on all aspects of the fabrication process using Taguchi experimental design techniques. Appropriate materials and processing conditions were selected for powder beneficiation, densification and heat-treatment operations. Component forming has been conducted using thermal-plastic-based injection molding (IM), pressure slip-casting (PSC), and Quick-Set™ injection molding. An assessment of material properties for various components from each material and process were made. For NT154, characteristic room-temperature strengths and Weibull Moduli were found to be range between ≈920 MPa to ≈1 GPa and ≈10 to ≈19, respectively. Process-induced inclusions proved to be the dominant strength limiting defect regardless of the chosen forming method. Correction of the lower observed values is being addressed through equipment changes and upgrades. For the NT230 and NT235 Si-SiC, characteristic room-temperature strengths and Weibull Moduli ranged from ≈240 to ≈420 MPa, and 8 to 10, respectively. At 1370°C, strength values for both the HIPed Si3N4 and the Si-SiC materials ranged from ≈480 MPa to ≈620 MPa. The durability of these materials as engine components is currently being evaluated.
A New Hue Capturing Technique for the Quantitative Interpretation of Liquid Crystal Images Used in Convective Heat Transfer Studies
Authors: Camci Cengiz , Kim Kuisoon , Hippensteele S. A.
Published: March 2015

This study focuses on a new image processing based color capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies. The present method is highly applicable to the surfaces exposed to convective heating in gas turbine engines. The study shows that, in single crystal mode, many of the colors appearing on the heat transfer surface strongly correlate with the local temperature. A very accurate quantitative approach using an experimentally determined linear hue versus temperature relation is possible. The new hue capturing process is discussed in detail, in terms of the strength of the light source illuminating the heat transfer surface, effect of the orientation of the illuminating source with respect to the surface, crystal layer uniformity and the repeatability of the process. The method uses a 24 bit color image processing system operating in hue-saturation-intensity domain which is an alternative to conventional systems using red-green-blue color definition. The present method is more advantageous than the multiple filter method because of its ability to generate many isotherms simultaneously from a single crystal image at a high resolution, in a very time efficient manner. The current approach is valuable in terms of its direct application to both steady state and transient heat transfer techniques currently used for the hot section heat transfer research in air breathing propulsion systems.
The Simulation of Three-Dimensional Viscous Flow in Turbomachinery Geometries Using a Solution-Adaptive Unstructured Mesh Methodology
Authors: Dawes W. N.
Published: March 2015

This paper presents a numerical method for the simulation of flow in turbomachinery blade rows using a solution-adaptive mesh methodolgy. The fully three dimensional, compressible, Reynolds averaged Navier-Stokes equations with k-ε turbulence modelling (and low Reynolds number damping terms) are solved on an unstructured mesh formed from tetrahedral finite volumes. At stages in the solution, mesh refinement is carried out based on flagging cell faces with either a fractional variation of a chosen variable (like Mach number) greater than a given threshold or with a mean value of the chosen variable within a given range. Several solutions are presented, including that for the highly three-dimensional flow associated with the corner stall and secondary flow in a transonic compressor cascade, to demonstrate the potential of the new method.
Inviscid-Viscous Coupled Solution for Unsteady Flows Through Vibrating Blades: Part 2 — Computational Results
Authors: He L. , Denton J. D.
Published: March 2015

A quasi 3-D inviscid-viscous coupled approach has been developed for unsteady flows around oscillating blades, as described in Part 1. To validate this method, calculations for several steady and unsteady flow cases with strong inviscid-viscous interactions are performed, and the results are compared with the corresponding experiments. Calculated results for unsteady flows around a bi-convex cascade and a fan tip section highlight the necessity of including viscous effects in predictions of turbomachinery blade flutter at transonic flow conditions.
Rotor Blade Unsteady Aerodynamic Gust Response to Inlet Guide Vane Wakes
Authors: Manwaring Steven R. , Fleeter Sanford
Published: March 2015

A series of experiments are performed in an extensively instrumented axial flow research compressor to investigate the fundamental flow physics of wake generated periodic rotor blade row unsteady aerodynamics at realistic values of the reduced frequency. Unique unsteady data are obtained which describe the fundamental unsteady aerodynamic gust interaction phenomena on the first stage rotor blades of a research axial flow compressor generated by the wakes from the Inlet Guide Vanes. In these experiments, the effects of steady blade aerodynamic loading and the aerodynamic forcing function, including both the transverse and chordwise gust components, and the amplitude of the gusts, are investigated and quantified.
An Unsteady Lifting Surface Theory for Ducted Fan Blades
Authors: Chi Ray M.
Published: March 2015

A frequency domain lifting surface theory is developed to predict the unsteady aerodynamic pressure loads on oscillating blades of a ducted subsonic fan. The steady baseline flow as observed in the rotating frame of reference is the helical flow dictated by the forward flight speed and the rotational speed of the fan. The unsteady perturbation flow, which is assumed to be potential, is determined by solving an integral equation that relates the unknown jump in perturbation velocity potential across the lifting surface to the upwash velocity distribution prescribed by the vibratory motion of the blade. Examples of unsteady pressure distributions are given to illustrate the differences between the three dimensional lifting surface analysis and the classical two dimensional strip analysis. The effects of blade axial bending, bowing (i.e., circumferential bending) and sweeping on the unsteady pressure load are also discussed.
Marine Gas Turbine Evaluation and Research at the Admiralty Test House, Rae Pyestock
Authors: Bruce C. J. , Cartwright R. A.
Published: March 2015

The Admiralty Test House (ATH) at the Royal Aerospace Establishment Pyestock has provided test bed facilities for evaluation of marine gas turbines and ancillary equipments for Royal Naval use since 1952.

While the ATH is presently undergoing an extensive refurbishment programme in preparation for trials of the Rolls-Royce 20MW Spey SM1C, research continues on a number of innovative gas turbine condition monitoring techniques.

This paper presents a brief history of the Marine Gas Turbine Section and describes the facilities of the ATH following major refurbishment. The capabilities of the steady state and transient data gathering facilities are outlined, together with the automated engine and test control systems which provide cost effective engine evaluation in both endurance and minor equipment trials.
An Experimental Study of Fluid Flow in Disk Cavities
Authors: Bhavnani S. H. , Khodadadi J. M. , Goodling J. S. , Waggott J.
Published: March 2015

Results are presented for an experimental study of fluid flow in models of gas turbine disk cavities. Experiments were performed on 70 cm diameter disks for rotational Reynolds numbers up to 2.29 × 106. Velocity and pressure distributions are presented and compared to previous theoretical and experimental studies for a free disk, and an unshrouded and shrouded plane rotor-stator disk system. Minimum coolant flow rates for the prevention of ingress, determined for the case of a simple axial rim seal, compare well with previously published data.
Fabrication and Testing of Ceramic Turbine Wheels
Authors: Takatori K. , Honma T. , Kamiya N. , Masaki H. , Sasaki S. , Wada S.
Published: March 2015

Silicon nitride (Si3N4) radial inflow turbine wheels were fabricated by injection molding at Toyota Central R & D Labs. The wheel was 142mm in outer diameter and had 14 blades. The radial wheel was too bulky to manufacture as a homogeneous and defect-free body in one piece. It was divided into two pieces for injection molding and put together into one body by a cold isostatic pressing step after binder removal. Spin testing was executed at room temperature and the resulting photographs taken from three directions provided useful information about the fracture mode of the wheels. The maximum burst speed of the wheels at room temperature was 98,900 rpm, which corresponded to 145% of the design speed. In a hot rig test, one of the wheels survived 75,000rpm for ten minutes at a turbine inlet temperature of 1,050°C.
Fatigue due to Noise-Induced Pressure
Authors: Wu T. W. , Wang J. J. , Seybert A. F.
Published: March 2015

The paper presents results of a preliminary study of the acoustic fatigue of an airframe structure as a result of turbojet engine noise. The acoustic pressure distribution, induced by jet-noise, is determined by a coupled FEM/BEM approach. A model of an airframe structure with no defects or microcracks is assumed to be subjected to loadings induced by a time-harmonic noise source. Solution techniques are summarized. A method is presented to analyze the acoustic stresses, additional to mechanical loading induced stresses, for the potential to initiate fatigue cracks and propagation of these cracks. Applications to similar structural systems are suggested.
Statistical and Mathematical Approach for Distribution Function Model for Low Probability of Failures
Authors: Bhonsle S. R. , VanKarsen C. V. , Michler J. R.
Published: March 2015

In probabilistic design it is common practice to use statistical models such as normal, lognormal, and Weibull to describe random design factors. However these distribution function models deviate in the lower tail, i.e. percentiles below 1%. The deviation is nonconservative in that since it predicts life longer than observed.

A Statistical Distribution Function called Adaptive Distribution Function Model similar to Abelkis model was developed. It is compatible with the collected data, and it produces conservative designs at low tail ends. It is also relatively easy to use.
Reliability Analysis of a Structural Ceramic Combustion Chamber
Authors: Salem Jonathan A. , Manderscheid Jane M. , Freedman Marc R. , Gyekenyesi John P.
Published: March 2015

The Weibull modulus, fracture toughness, and thermal properties of a silicon nitride material used to make a gas turbine combustor were experimentally measured. The location and nature of failure origins resulting from bend tests were determined with fractographic analysis. The measured Weibull parameters were used along with thermal and stress analysis to determine failure probabilities of the combustor with the CARES design code. The effects of data censoring, FEM mesh refinement, and fracture criterion were considered in the analysis.
Experimental Investigation of Vortex Structure in Corner Region of a Linear Compressor Cascade
Authors: Tang Y. P. , Chen F. , Chen M. Z.
Published: March 2015

A detailed experimental investigation was carried out to examine the vortex structure in the corner region (between the end wall and the suction surface of blades) of a linear compressor cascade. A corner vortex was identified in the corner flow in the experiment. The corner vortex sheds from the pressure-driven boundary layer on the end wall in a process of three-dimensional separation. It dominates the corner flow by the strong interaction with the main flow and the boundary layer on the suction surface of blade. The difference between the corner vortex and the well-known passage vortex is discussed. A topology of the vortex structure is proposed. Furthermore, the dynamic effects of the vortex structure has been investigated, which leads to a explanation for the mechanism of corner stall in compressor cascades.
Optimization of the Fatigue Properties of INCONEL Alloy 617
Authors: Smith G. D. , Yates D. H.
Published: March 2015

Rigorous control of the annealing practice and certain alloying elements can directly influence key characteristics which aid in optimizing low cycle fatigue (LCF) properties of INCONEL® alloy 617. These procedures favorably influence grain size, carbide microstructure and mechanical properties. It is shown how an optimum combination of these procedures can greatly improve LCF properties of alloy 617 sheet.
Turbine Blade Tip Clearance Improvement
Authors: Glezer B.
Published: March 2015

A recently developed non-traditional design concept addressing turbine blade tip clearance reduction to provide long-term engine performance improvement and stability is presented. The concept is based on the direct attachment of the diaphragm, which supports Stage 1 integral nozzle and tips shroud segments, to the bearing housing, thus providing a close thermal link between the rotor and the stator. Transient thermal matching between the rotating and stationary structures was based on analytical prediction. Results of the complex turbine hot section study including cooling flow, thermal, stress, and deflection analyses are presented. An advanced tip clearance measurement technique was used in the full scale engine test to verify the analytical predictions. The potential to reduce tip clearance to less than 1% of blade height without blade tip rubs has been demonstrated. Extensive field operating experience with more than 100 Centaur Type ‘H’ engines showed very light or no blade tip rub and corresponding engine performance stability during long-term operation.
A Unified Variable-Domain Variational Approach to Hybrid Problems of Compressible Blade-to-Blade Flow
Authors: Liu Gao-Lian , Yan Shan
Published: March 2015

A unified theory of various hybrid problems for blade-to-blade compressible flow is developed herein via the functional variation with variable domain. Two variational principle (VP) families for three typical hybrid problems are derived, following a systematic approach (Liu, 1990a). Full advantage is taken of the natural boundary condition and suction/blowing along the blade surface are accommodated. This theory is aimed at offering a new theoretical basis for the finite element method (FEM) and various ways for blade design and/or modification, and it also constitutes an important part of optimal cascade theory (Liu,1987b). Based on these VPs, a new FEM with self-adjusting nodes is also suggested, and the numerical tests yield good results.
Analytical Investigation of the Rules of Component Matching in Turbojet Engines
Authors: Liu Dao-Zhi
Published: March 2015

In turbojet engines, phenomena under off–design conditions are related to the variations of incidence angles at different compressor stages. In the present paper, analytical formulae about the off–design incidence variations of inlet and exit compressor stages are derived. Using these fomulae, the detailed rules about engine parameter variations under off–design conditions are obtained; a series of phenomena about engine performance for low and high pressure ratio engines, engines with axial, centrifugal and combined compressors, as well as single–shaft and two–spool engines can then be explained systematically, their physical essence will be revealed clearly; and a variety of new situations and problems about engine off–design behavior can be predicted in advance.
The Torsional Stability of a Compressor Cascade
Authors: Davies M. R. D.
Published: March 2015

This paper includes new experimental data on the torsional stability of a compressor or fan type of blade row. This data is linked in with published material to form a three dimensional figure describing the stability of such rows. The data is then discussed by considering relative values of influence coefficients and some of the trends in the stability figure are explained. New data is also included on the relative magnitudes and phases of the influence coefficients.
An Experiment on Unsteady Flow Over an Oscillating Airfoil
Authors: He L. , Denton J. D.
Published: March 2015

In order to enhance understanding of viscous-dominated blade flutter and to provide experimental data for validating unsteady viscous flow solutions, unsteady flow over a 2-D NACA-65 airfoil oscillating in torsion at an amplitude of 2° and a reduced frequency up to 0.69 has been experimentally investigated in a low-speed wind tunnel under different loading conditions. Unsteady pressure distribution is measured on both suction and pressure surfaces using pressure transducers. On the suction surface hot-film measurements are conducted to indicate the development of the unsteady boundary layer. Unsteady boundary layer behaviour and its effects on the airfoil’s aeroelasticity at the different loading conditions are demonstrated. The results also throw some light on understanding the onset mechanism of “dynamic stall” which involves a persistent convective pressure wave pattern with marked unstable aeroelastic characteristics.
Interactive Engine System Dynamics Analysis
Authors: Storace A. F.
Published: March 2015

A major constraint on the application of new gas turbine structural concepts is the control of engine system vibration and maneuver loads and deflections. Because many iterations are usually needed to arrive at a satisfactory design, and because batch oriented computer calculations require substantial turnaround time between runs, there is often a limitation on the number of analyses that can be made prior to a design decision. The VISA (Vibration Interactive System Analysis) computer program has been developed at General Electric Aircraft Engines (GEAE) to facilitate system vibration and maneuver loads analysis and to improve its quality. The VISA interactive program is based on a unique adaptation of the finite element method that provides an extremely user friendly and efficient general rotordynamics analysis capability, thereby resulting in a cost effective optimum design. The VISA interactive analysis utilizes a combined transfer matrix/finite–element formulation which combines the advantages of both of these methods. In the former case, the dimensionality of the analysis is reduced, and in the latter case, automatic analysis of multibranch, multilevel engine structures, and a generalized approach to modeling various types of boundary and constraint conditions is provided.