bluuebunny/crossref_metadata_2025 huggingface dataset:
Visualizations of the Unsteady Flow Field Near the Endwall of a Compressor Cascade
Authors: Ma Hongwei , Jiang Haokang , Yang Lin
Published: July 2014

This paper presents flow visualizations of the unsteady flow field near the endwall of a compressor cascade. The experiments were performed in a water tunnel using the hydrogen bubble technique. A Pt wire was positioned parallel to the endwall and ahead of the cascade at 2% span from the endwall. The traces of hydrogen bubbles generated by the wire were visualized within a light sheet arranged at various cross-sections around the cascade. The unsteady flow field was visualized at different incidences without a radial clearance. A periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade, which plays a leading role in the flow field near the endwall. The interaction and the flow mixing among the counter-rotating horseshoe legs, the endwall boundary layer and the main flow, periodically occur in the passage. Breakdown of the horseshoe vortex is clearly observed in the cascade while the unsteady and complex flow field is shown at the corner of the suction surface.
Laser Velocimeter Measurements of Axial Velocity Field in the NASA Supersonic Fan Rotor
Authors: Lepicovsky J. , Braunscheidel E. P. , Bruckner R. J. , Tweedt D. L.
Published: July 2014

An analysis of laser Doppler velocimeter (LDV) data for the axial velocity flowfield in the rotor of the Mach 2 inlet flow supersonic throughflow fan (SSTF) is presented in this paper. The paper starts with a short description of the SSTF test package to highlight the specifics of the SSTF operation. It is followed by a detailed description of a dedicated LDV system for measurement in a supersonic throughflow fan and the experience gained. Most of the experimental data presented were acquired in a low supersonic throughflow regime (inlet Mach number of 1.4). The results and conclusions presented are based mainly on the experimental data only. A limited amount of computational fluid dynamics (CFD) predictions were used for comparison with the experimental results. The CFD methods, however, are not discussed in this paper. As shown in this paper, a reasonably good agreement between the LDV data and the CFD predictions was found for the low supersonic throughflow regime. The design point data (inlet Mach number of 2.0) exhibited an unexpectedly high noise in the velocity data in comparison with the data for low supersonic throughflow operating conditions. For the off-design supersonic regime (shock in rotor), substantial differences exist between the experimental and computational data.
Investigation Into Core Compressor Tip Leakage Modelling Techniques Using a 3D Viscous Solver
Authors: Glanville Jonathan P.
Published: July 2014

The leakage flow through the tip clearance gap of an axial compressor has a significant effect on loss production and stall behaviour. Accurate modelling is essential if improved designs are to be developed which control such flows. Studies have been carried out using the DERA TRANSCode 3D Reynolds-Averaged Navier-Stokes code to predict the tip leakage flows in a low speed research compressor. Calculations were carried out using both a simple pinched-tip model and an improved mesh which allowed the true square-tip geometry to be represented. Comparisons between the Baldwin-Lomax algebraic turbulence model and the Spalart-Allmaras one-equation transport model were also made. The results showed that the predictions of both the detailed flows and the loss levels were sensitive to the modelling and that substantial improvements in accuracy were possible.
Short and Long Length-Scale Disturbances Leading to Rotating Stall in an Axial Compressor Stage With Different Stator/Rotor Gaps
Authors: Inoue M. , Kuroumaru M. , Yoshida S. , Furukawa M.
Published: July 2014

The transient processes of rotating stall evolution have been investigated experimentally in a low-speed axial compressor stage with three stator-rotor gaps. The pressure traces at 8 circumferential locations on the casing wall near the rotor leading edge have been analyzed by the wavelet transforms. With the appropriate mother wavelets, the evolution of short and long length-scale disturbances leading to the stall can be captured clearly.

Behavior of these disturbances is different depending on the stator-rotor gap. For the large and middle gap, the stall inception is detected by a spiky short length-scale disturbance, and the number of spiky waves increases to generate the high frequency waves. They becomes the short length-scale part-span stall cells at the mild stall for the large gap, while they turn into a big stall cell with growth of a long length-scale disturbance for the middle gap. In the latter case, therefore, the stalling process was identified with ‘high frequency stall inception’. For the small stator-rotor gap, the stalling process is identified with ‘long wave-length stall inception’, and supported the recent computational model for the short wave-length stall inception by showing that closing the rotor-stator gaps suppressed the growth of short length-scale disturbances.

From the measurement of the pressure field traces on the casing wall, a hypothesis has been built up that the short length-scale disturbance should result from a separation vortex from a blade surface to reduce circulation. The processes of the stall evolution are discussed on this hypothesis.
Computational Analysis of Passive Stall Delay Through Vaned Recess Treatment
Authors: Ghila A. , Tourlidakis A.
Published: July 2014

This paper presents a computational investigation of flows in a single axial flow fan with and without casing treatment. It analyses the effect of the recess casing treatment on stall margin improvement as well as its influence on global performance parameters. The paper seeks to offer a contribution to the understanding of the physical processes occurring when approaching stall and the working mechanism by which casing treatments improve stall margin.

A Reynolds-Averaged Navier-Stokes CFD code was used for the analysis and the numerical investigation of the overall performance, efficiency and work-input characteristics of the fan were found to agree very well with previously reported experimental results. The effect of casing treatment was investigated using two types of configurations, vaneless and vaned casing. The vaneless casing treatment produced a sizeable stall margin improvement with negligible loss of efficiency. The recess was fitted later with vanes and was shown to offer both a further stall margin improvement and an increase in the pressure rise coefficient without any significant drop in efficiency at design conditions.
Turbomachinery Blade Design Using 3-D Inverse Design Method, CFD and Optimization Algorithm
Authors: Ashihara Kosuke , Goto Akira
Published: July 2014

An optimization approach for improving turbomachinery performance was proposed based on a three-dimensional inverse design method, a Computational Fluid Dynamics (CDF) and optimization algorithm. By combining the three-dimensional inverse design method and CFD predictions, the blade loading parameters which is the major inputs for the three-dimensional inverse design method were treated as design variables and the impeller performance predicted by CFD was treated as an objective function of the optimization problem.

Firstly, to clarify the effects of optimization algorithm, mixed-flow pump impellers (Ns400), with a specific speed of 400 (m3/min,m,min−1) or 0.155 (non-dimensional), were optimized to improve the impeller efficiency by using several optimization algorithm. From these results, it was confirmed that turbomachinery optimization using the three-dimensional inverse design method is a multi-peak problem and it is essential to use exploratory techniques such as Simulated Annealing. Then, a mixed-flow pump impeller (Ns1350), with a specific speed of 1350 (m3/min,m,min−1) or 0.523 (non-dimensional), was optimized to improve the impeller efficiency with constraints for suction performance by Simulated Annealing. Reasonably high efficiency and high suction performance were confirmed by comparing the CFD results with those for the previous design which employed manual optimization.
The Oxidation of Austenitic Stainless Steel Foils in Humidified Air
Authors: Rakowski James M.
Published: July 2014

Austenitic stainless steels form a protective external chromium oxide scale when exposed to elevated temperatures in air. Laboratory testing of thin stainless steel foil specimens demonstrates that the presence of water vapor decreases the time required for breakaway oxidation to occur. Accelerated oxidation begins after the end of an incubation period, the length of which is affected by the amount of water vapor present. Significant changes in scale microstructure accompany the transition from parabolic to accelerated oxidation.
Real Time Engine Model Implementation for Adaptive Control and Performance Monitoring of Large Civil Turbofans
Authors: Stamatis A. , Mathioudakis K. , Ruiz J. , Curnock B.
Published: July 2014

A real time engine model to be used as an onboard observer in Large Civil Turbofans has been developed. The main features of this Real Time Model are its non-linear physical structure (identical with a detailed transient model, which may represent the real engine) as well as its ability to adapt itself to the engine condition. General and specific requirements for the targeted model have been set, evolution of the model is presented and various investigations concerning the ability of the model to satisfy these requirements are discussed. The conclusion is that the model is faster than real time in terms of a realistic time step for current turbofan engines controllers using a processor with computing power about ten times less than the current existing processors. It is also worth mentioned that this speed is achieved without sacrificing model accuracy. In general maximum errors less than 1% can be obtained using no more than five fixed iterations in the model in order to achieve this speed.
Performance of Zero Emissions Integrated Gasification Hydrogen Combustion (ZE-IGHC) Power Plants With CO2 Removal
Authors: Cau Giorgio , Cocco Daniele , Montisci Augusto
Published: July 2014

This paper concerns a performance evaluation of advanced zero emissions (NOx, SOx, CO and particulate, but also CO2), coal gasification integrated power plants with hydrogen combustion (ZE-IGHC). In ZE-IGHC power plants the hydrogen is produced through CO shift conversion and subsequent CO2 separation. The hydrogen is burned using pure oxygen in an internal combustion steam power plant with double combustion and thermodynamic regeneration. As a result of raw gas cleaning, CO2 separation and hydrogen combustion with oxygen, the ZE-IGHC power plant eliminates pollutant and greenhouse gas emissions.

A comparative study of ZE-IGHC plant configurations based on different gasifiers and raw gas cooling options indicated that net efficiencies of up to about 50% can be achieved by resorting to configurations based on dry-feed gasifiers and raw gas cooling heat recovery with steam production. The simpler and cheaper plant configurations based on wet-feed gasifiers and raw gas quench systems give an efficiency penalty of about 3-4 % points.

The ZE-IGHC power plant presented here can be a very attractive option for a near term, coal-fired power generation system. What is more, its major components are already adopted in conventional power plants and only the hydrogen combustors and the high temperature turbine require technology development.
A Promising Power Option: The FERCO SilvaGas™ Biomass Gasification Process — Operating Experience at the Burlington Gasifier
Authors: Paisley M. A. , Irving J. M. , Overend R. P.
Published: July 2014

The Burlington Vermont gasifier is the first commercial scale demonstration of the FERCO indirectly heated biomass gasification process. The gasification plant is the largest operation of its type in the US and was the first process to integrate a biomass gasifier with a gas turbine during pilot operations at Battelle’s Columbus, OH facilities. The Burlington plant is coupled to the McNeil station of the Burlington Electric Department and is being used to evaluate and demonstrate the gasification technology both as a producer of fuel gas and in a combined cycle with a gas turbine power generation system. This paper discusses operating results at the Burlington site including gas cleanup / conditioning observations. Future Energy Resources, the owner of the gasification technology, is developing projects worldwide.
Flame Transfer Function Calculations for Combustion Oscillations
Authors: Zhu M. , Dowling A. P. , Bray K. N. C.
Published: July 2014

Combustors with fuel-spray atomisers are particularly susceptible to a low-frequency oscillation at idle and sub-idle conditions. For aero-engine combustors, the frequency of this oscillation is typically in the range 50-120Hz and is commonly called ‘rumble’. The mechanism involves interaction between the plenum around the burner and the combustion chamber. Pressure variations in the plenum or the combustor alter the inlet air and fuel spray characteristics, thereby changing the rate of combustion. This in turn leads to local ‘hot spots’ which generate pressure oscillations as they convect through the downstream nozzle.

In order to eliminate the combustion oscillations, it is essential to determine which fuel atomisers are particularly likely to lead to instability by quantifying their sensitivity to flow perturbations. This can be done by identifying the system through understanding the transfer function, which represents the relationship between the unsteadiness of combustion and the inlet fuel and air. In the present work, various types of signals are applied to produce a small change the inlet fuel and air flow rates, the response in the rate of heat release caused downstream was calculated and stored for subsequent analysis. Afterwards, the system transfer function is calculated by determining the coefficients of an IIR filter (Infinite Impulse Response) for which the output signal is the downstream heat release rate and the input signal is the inlet flow rate. The required transfer function then follows from the Fourier transform of this relationship. The resulting transfer functions are compared with those obtained by the forced harmonic oscillations at a fixed given frequency. Suitably chosen input signals accurately recover the results for harmonic forcing at a single frequency, but also give detailed information about the combustor response over a wide frequency range. There are two distinct forms to the low-frequency quasi-steady response. In the primary zone, the rate of combustion is influenced by the turbulence and is enhanced when the inlet air velocity is large. Near the edge of combustion zone, the rate of combustion depends on the mixture fraction and is high when the mixture fraction is close to the stoichiometric value. This generates ‘hot spots’ which convect into the dilution zone. At higher frequencies, the combustion lags this quasi-steady response through simple lag-laws and the relevant time delays have been identified.
The Integration of Atmospheric Molten Carbonate Fuel Cells With Gas Turbine and Steam Cycles
Authors: Campanari Stefano , Macchi Ennio
Published: July 2014

The exploitation of the high-temperature-fuel-cell technology, actually being developed by many companies involved in the gas turbine market, could allow outperforming performance of conventional prime movers based upon fossil fuel combustion.

This paper investigates the integration of molten carbonate fuel cells (MCFCs) working at atmospheric pressure with some representative cycle configurations based either on steam and gas turbine cycles.

Detailed energy balances of the most promising cycle configurations are presented; fuel cell and conventional components working parameters and technological issues are described and discussed.

It is shown that efficiencies well above 60% can be achieved by combining MCFCs either with recuperative gas turbine or steam cycles.
Degradation Effects on Combined Cycle Power Plant Performance: Part 2 — Steam Turbine Cycle Component Degradation Effects
Authors: Zwebek A. , Pilidis P.
Published: July 2014

This is the second paper exploring the effects of the degradation of different components on Combined Cycle Gas Turbine (CCGT) plant performance.

This paper investigates the effects of degraded steam path components of steam turbine (bottoming) cycle have on CCGT power plant performance. Areas looked at were, steam turbine fouling, steam turbine erosion, heat recovery steam generator degradation (scaling and/or ashes deposition), and condenser degradation. The effect of gas turbine back-pressure on plant performance due to HRSG degradation is also discussed.

A general simulation Fortran code was developed for the purpose of this study. This program can calculate the CCGT plant design point performance, off-design plant performance, and plant deterioration performance. The results obtained are presented in a graphical form and discussed.
Computational Design and Experimental Evaluation of Using a Leading Edge Fillet on a Gas Turbine Vane
Authors: Zess G. A. , Thole K. A.
Published: July 2014

With the desire for increased power output for a gas turbine engine comes the continual push to achieve higher turbine inlet temperatures. Higher temperatures result in large thermal and mechanical stresses particularly along the nozzle guide vane. One critical region along a vane is the leading edge-endwall juncture. Based on the assumption that the approaching flow to this juncture is similar to a two-dimensional boundary layer, previous studies have shown that a horseshoe vortex forms. This vortex forms because of a radial total pressure gradient from the approaching boundary layer.

This paper documents the computational design and experimental validation of a fillet placed at the leading edge-endwall juncture of a guide vane to eliminate the horseshoe vortex. The fillet design effectively accelerated the incoming boundary layer thereby mitigating the effect of the total pressure gradient. To verify the CFD studies used to design the leading edge fillet, flow field measurements were performed in a large-scale, linear, vane cascade. The flow field measurements were performed with a laser Doppler velocimeter in four planes orientated orthogonal to the vane. Good agreement between the CFD predictions and the experimental measurements verified the effectiveness of the leading edge fillet at eliminating the horseshoe vortex. The flowfield results showed that the turbulent kinetic energy levels were significantly reduced in the endwall region because of the absence of the unsteady horseshoe vortex.
Conjugate Heat Transfer Analysis of Internally Cooled Configurations
Authors: Rigby David L. , Lepicovsky Jan
Published: July 2014

This paper describes the addition of conjugate capability to an existing Navier-Stokes code. Also, results are presented for an internally cooled configuration. The code is currently referred to as the Glenn-HT code, because of its origin at the NASA Glenn Research center and its proven ability to predict flow and Heat Transfer. In the past, the code had been called traf3d.mb. The addition of the conjugate capability to the code was accomplished with a minimum amount of changes to the code, with the understanding that if more advanced techniques were required they could be added at a later date. In the solid region, the density is constant and the velocities are of course zero which leaves only a simplified form of the energy equation to be solved. This simplified energy equation is solved using the same method as in the gas regions with only minor changes to the numerical parameters. At the interface between the gas and solid the wall temperature is set so as to produce the same heat flux in each region. Results are presented for a pipe flow to validate the implementation. Numerical and experimental results are then presented for flow over a flat plate that is cooled internally. Flat plate Reynolds numbers in the range 180,000 to 950,000, and coolant channel Reynolds numbers in the range 30,000 to 60,000 are presented.
Interstage Injection System for Heavy Duty Industrial Gas Turbine Model 7EA
Authors: Ingistov Steve
Published: July 2014

This paper describes new methods of cleaning large multistage axial compressors that are the part of Gas Turbine Unit (GTU). Existing, standard method of compressor cleaning are on-line and off-line. In both cases of compressor cleaning clean water and appropriate detergents are mixed to remove dirt deposits from the blade surface. The on-line system is attractive because the cleaning is done when GTU is under full load. The on-line compressor cleaning slows down inevitable dirt depositing. Offline cleaning is much more effective than on-line cleaning. The negative side of off-line cleaning is that GTU must be shut down. In case of large GTU the processes of shut down and start up require significant amount of time. This paper also incorporates the efforts required to install Inter-stage Injection System (IIS) in one GTU in Watson Cogeneration Company (WCC).
Gas Turbine Inlet Air Cooling Using Absorption Refrigeration: A Comparison Based on a Combined Cycle Process
Authors: Sigler James , Erickson Don , Perez-Blanco Horacio
Published: July 2014

Gas turbines are used to meet increasing power-generating needs throughout the world. Technologies for augmenting the capacity of new or existing installations are being devised. One common strategy is to employ evaporative cooling of gas turbine inlet air. This method is attractive because of simplicity and relatively modest hardware requirements. Another strategy is to recover exhaust heat in order to activate an absorption-refrigeration machine. The cooling machine output is then used to cool and dehumidify the compressor inlet air. In this paper, we delineate a heat recovery system for steam/power production, and an ammonia-water absorption machine. The ammonia-water technology offers an element of novelty in that it is capable of chilling the air to lower temperatures than the currently used lithium-bromide technology, or than the evaporative cooling approach. Performance calculations based on leading commercial software are offered. In a simple payback analysis based on the numbers obtained from the simulation, we discuss the potential of the technique.
Low-Cycle Fatigue of Nickel-Based Superalloy Hastelloy X at Elevated Temperatures
Authors: Chen Lijia , Liaw Peter K. , McDaniels Robert L. , Blust James W. , Browning Paul F. , Seeley Rodger R. , Klarstrom Dwain L.
Published: July 2014

The fully-reversed total strain-controlled low-cycle fatigue tests with and without hold times, as well as stress-relaxation tests, were conducted at 816°C and 927°C in laboratory air on a nickel-based superalloy, HASTELLOY X. The influence of temperatures and hold times on low-cycle fatigue behavior of the alloy was investigated. At both temperatures of 816°C and 927°C, the alloy exhibited initial cyclic hardening, followed by a saturated cyclic stress response or cyclic softening under low-cycle fatigue without hold times. For low-cycle fatigue tests with hold times, however, the alloy showed either cyclic hardening or cyclic stability, which is closely related to the test temperature and the duration of the hold time. It was also observed that the low-cycle fatigue life of the alloy considerably decreased due to the introduction of strain hold times. Generally, a longer hold time would result in a greater reduction in the fatigue life. However, for the tests without hold times, the test temperature seems to have little influence on the fatigue life of the alloy at the test temperatures used in this investigation. The stress relaxation tests show that at the beginning of strain hold, the stress drops very quickly and then decreases very slowly with prolonging time. In addition, the fracture surfaces of the fatigued specimens were observed using scanning electron microscopy to determine the crack initiation and propagation modes. The fatigue life was predicted by the frequency modified tensile hysteresis energy method. The predicted lives were found to be in good agreement with the experiment results.
Failure Analysis of Inlet Guide Vanes
Authors: McAlpin Ronald L. , Talley Peggy L. , Bernstein Henry L. , Holm Robert E.
Published: July 2014

The common failure modes of Variable Inlet Guide Vanes (VIGV’s or IGV’s) on industrial gas turbines are reviewed. These mechanisms include corrosion, cracking, and wear of the IGV’s, their bushings and thrust washers. A new mechanism for IGV failure is described through a case history and metallurgical examination. High cycle fatigue cracking in multiple IGV’s was found at a location different from the expected cracking location. The failure is caused by a combination of wear loss and galling of the IGV metal shafts against the polymer bushings, combined with deterioration of the polymer matrix. Finite element analysis (FEA) is used to verify the loading mode, maximum stress location, and crack propagation direction.
Component Management Programs for Reliable Life Extension
Authors: Cooke Lloyd A.
Published: July 2014

Conventional maintenance schedules and scheduling techniques are typically based on the manufacturer’s guidelines and applied to all engines of a certain make and model. This approach does not always address the specific operating environment and requirements for each operator.

An alternative to this conventional “one schedule suits all” approach is the Component Management Program described in the paper. This type of program is designed to tailor maintenance requirements to suit the specific operating environment of the operator’s engine or fleet of engines. The program is intended to extend and optimize maintenance intervals and at the same time ensure reliability of the components. The paper outlines the metallurgical analysis and other techniques that are incorporated into a Component Management Program, the tracking systems used to schedule maintenance, and some case studies where these programs have been used to extend component life and reliability.
Aerodynamic Design of a New Five Stage Low Pressure Turbine for the Rolls Royce Trent 500 Turbofan
Authors: Ulizar I. , González P.
Published: July 2014

Almost a decade ago, ITP (Industria de Turbo Propulsores, S.A.) started to participate in Low Pressure turbine design supported by Rolls-Royce. The Trent 500 LP turbine aerodynamic design is the most challenging and extensive design work carried out to the moment.

The Trent 500 is part of the Rolls Royce Trent family. It has been designed to enter in service in the Airbus 340-600. This engine has very aggressive targets in terms of cost, performance, weight and noise. An optimization process was carried out during the preliminary and detailed design phases to accomplish these targets.

This paper describes the most outstanding characteristics of the LP turbine, how the previous experience and Research and Technology results have been employed in this design and also some of the new advanced features, e.g. the introduction of spoon aerofoils.
Boundary Layer Development in the BR710 and BR715 LP Turbines: The Implementation of High Lift and Ultra High Lift Concepts
Authors: Howell R. J. , Hodson H. P. , Schulte V. , Schiffer Heinz-Peter , Haselbach F. , Harvey N. W.
Published: July 2014

This paper describes a detailed study into the unsteady boundary layer behaviour in two high lift and one ultra high lift Rolls-Royce Deutschland LP turbines. The objectives of the paper are to show that high lift and ultra high-lift concepts have been successfully incorporated into the design of these new LP turbine profiles.

Measurements from surface mounted hot film sensors were made in full size, cold flow test rigs at the altitude test facility at Stuttgart University. The LP turbine blade profiles are thought to be state of the art in terms of their lift and design philosophy. The two high lift profiles represent slightly different styles of velocity distribution. The first high-lift profile comes from a two stage LP turbine (the BR710 cold-flow, high-lift demonstrator rig). The second high-lift profile tested is from a three-stage machine (the BR715 LPT rig). The ultra-high lift profile measurements come from a redesign of the BR715 LP turbine: this is designated the BR715UHL LP turbine. This ultra high-lift profile represents a 12% reduction in blade numbers compared to the original BR715 turbine.

The results from NGV2 on all of the turbines show “classical” unsteady boundary layer behaviour. The measurements from NGV3 (of both the BR715 and BR715UHL turbines) are more complicated, but can still be broken down into classical regions of wake-induced transition, natural transition and calming. The wakes from both upstream rotors and NGVs interact in a complicated manner, affecting the suction surface boundary layer of NGV3. This has important implications for the prediction of the flows on blade rows in multistage environments.
Materials Selection for High Temperature (750°–1000°C) Metallic Recuperators for Improved Efficiency Microturbines
Authors: Pint Bruce A. , Swindeman Robert W. , More Karren L. , Tortorelli Peter F.
Published: July 2014

The incorporation of a primary surface recuperator is one method for significantly improving the energy efficiency of a microturbine. The goal of this work is to employ laboratory testing of foil material (≈ 75-125μm or 3-5 mil thickness) to select alloys for higher temperature (750°−1000°C, 1400-1800°F) recuperator performance based on creep strength and corrosion resistance. Alloys of interest are high-Cr, Ni-base superalloys such as alloy 625 and aluminum-containing alloys such as Haynes alloy 214 and Plansee alloy PM2000, which is an oxide-dispersed FeCrAl. The interest in the latter two alloys is based on their corrosion resistance. Particularly in exhaust gas environments, chromia surface oxides are not sufficiently protective at high temperatures to achieve desired lifetimes. The formation of a slow-growing external alumina scale confers exceptional corrosion resistance for this application.
Design Development of Unitized Titanium Structure
Authors: Groneck Daniel , Harmon Dave
Published: July 2014

Traditional airframe primary structure is fabricated from wrought product forms that are transformed by machining, forming, and joining into structural components. These individual parts are assembled together by fasteners to create the structure. Under the program reported herein, and in conjunction with a casting vendor, prototype titanium (Ti-6Al-4V) cast airframe components were designed and fabricated. The typical overall dimensions of each casting are 50 inches × 40 inches × 30 inches (127 cm × 102 cm × 76 cm), and weigh approximately 190 pounds (86 kg) per casting. The castings were modeled on generic aircraft fuselage structure that incorporated smooth inner moldline surface and integral webs and keels, capped by a T-element, web stiffeners, access holes, and other detail features. Multiple castings are joined to create the airframe structure. A rapid prototyping method was utilized to create the pattern, which eliminated the requirement for expensive metal tooling. The prototype castings successfully demonstrated the producibility of this generic airframe structure.
Integrating Subsystem and Engine System Assessments
Authors: Van Griethuysen Valerie J. , Glickstein Marvin R. , Hodge Ernest S.
Published: July 2014

In the past, system and subsystem level assessments for propulsion systems have been a long and drawn out serial process, typically taking several months to a year or more. Data exchange from one subsystem group to the next was a manual process. This was particularly the case when different computer platforms were being utilized to run the models. Each group would optimize their particular subsystem as a separate entity. There were no approaches available to facilitate the evaluation of how a particular subsystem, when combined with the engine, would impact the overall integrated system. The availability of tools to facilitate direct interface of the various subsystem models with engine performance decks was not available. As a result, the lead-times for various iterations were such that not all of the groups were even working on the same configuration. Fortunately, software technology has been evolving, and the ability to integrate models is now becoming available. This paper describes work-in-progress of an innovative methodology for high-level integration of complex flight systems. This new approach will facilitate rapid integration and optimization of propulsion and secondary subsystems in a truly concurrent manner, providing capability for top-level evaluation of complex and highly integrated flight system architectures
Flight Test and Refinement of a Nacelle Ventilation Inlet Partially Submerged in Boundary Layer
Authors: Lundy Brian F. , Sylvester Thomas G. , Catt Jeffrey A.
Published: July 2014

Efforts to develop, test, and refine a nacelle ventilation inlet for the F-16 Fighting Falcon are presented in this work. The nacelle inlet was developed to support retrofit of existing F-16 aircraft with an ejector nozzle.

The F-16 is equipped with a ventilated nacelle that inhibits ignition sources and accumulation of flammable vapors in the engine bay. When integrating the ejector nozzle, Lockheed Martin Aeronautics Company (LM Aero) and GE Aircraft Engines (GEAE) took advantage of this feature to redirect nacelle ventilation air (which is typically dumped overboard) to the exhaust nozzle for cooling. This system dramatically extends nozzle divergent flap and seal life and reduces operational and support (O&S) costs.

GEAE’s ejector nozzle produces higher nacelle ventilation exhaust pressures than the existing system, prompting the need to redesign the nacelle inlet to maintain nacelle ventilation capability. Fire protection and nozzle cooling goals drove the need for higher nacelle pressure, while structural design limited the maximum pressure within the nacelle. The design space was bound by these contrasting requirements. To complicate matters, the nacelle inlet also had to manage the thick boundary layer generated by the aircraft fuselage.

A flight test was performed to manage uncertainties in the system and mitigate the risks of installing a new nacelle inlet on the F-16. The flight test revealed the influence of shock wave / boundary layer interaction (viscous interaction) on inlet pressure recovery. These findings resulted in several recommendations for improving the inlet design, the most significant being the inclusion of a boundary layer diverter. An overview of inlet development and the results obtained from the risk management tasks are presented in this work.
High Response Valve for Active Combustion Control
Authors: Wu Dong N. , Michalski Joseph W. , Jaw Link C. , Semega Kenneth
Published: July 2014

This paper describes the development of a prototype high response fuel valve using piezoelectric actuator for fuel modulation control in gas turbine engines. In flow bench test, this prototype valve demonstrated 5∼11% peak-to-peak modulation strength at flow rates up to approximately 1500 pph and frequencies up to 500 Hz.
Tensile Fatigue and Life Prediction of a SiC/SiC Composite
Authors: Shi Jun
Published: July 2014

This paper summaries two sets of tension-tension fatigue results. The first set corresponds to low R ratio (0.1) and low frequency (1Hz), whereas the second set covers high R ratio (0.9) and high frequency (10Hz). For the former, detailed analysis of stress strain loops is conducted in connection with the underlying mechanisms that govern fatigue deformation and life. For the latter only stiffness variation with fatigue cycles is discussed. The test results are also examined for their impact on fatigue life prediction.
Research Into Technological and Structural Capabilities of Alumino-Boron-Nitride Ceramic Material for Gas Turbine Engine Applications
Authors: Soudarev A. V. , Grishaev V. V. , Souryaninov A. A. , Soudarev B. V. , Molchanov A. S.
Published: July 2014

Application of alumino-boron-nitride ceramic materials (“SUGRAV” [1] and “SUGRAV-M”) to various components of high temperature paths of gas turbine plants [2–6] is based on the development of such designs which allow for the specific features of the mechanical and thermophysical properties of said ceramic materials.
LES Predictions of Aerodynamic Phenomena in LPP Combustors
Authors: Tang G. , Yang Z. , McGuirk J. J.
Published: July 2014

The unsteady aerodynamic behaviour in lean-premixed-prevapourised combustion geometries is examined in the present paper using Large Eddy Simulation (LES) methods. A typical LPP geometry involving highly swirling flow is studied. Features of the unsteady turbulent flow are well resolved by the LES predictions and phenomena such as swirl precession at a specific low frequency are observed. Shear layer unsteady behaviour and its consequences for the flow in the vicinity of the interface between premix duct and main combustor duct are presented. Some comparison with measured time-mean LDA data in the premix duct is possible, which indicates the benefits of adopting an LES approach rather than the traditional RANS methodology.
The Application of Printed Circuit Heat Exchanger Technology in the Pebble Bed Modular Reactor Demonstration Plant
Authors: McCormack Des
Published: July 2014

The Pebble Bed Modular Reactor (PBMR) Demonstration Plant is a 100 MW(e) gas cooled nuclear reactor being developed by Eskom, the South African state electricity utility. The PBMR uses helium in a closed cycle and operates at pressures up to 7.0 MPa and temperatures up to 900°C. Three heat exchangers are used in the PBMR power generation cycle, a Recuperator, a Pre-cooler and an Intercooler. All three exchangers play an important role in the power generation cycle but the Recuperator represents the most challenging application for heat exchanger technology requiring high performance under demanding operating conditions. Printed Circuit Heat Exchanger (PCHE) technology is being considered for Recuperator for several reasons including its ability to handle high pressures and high temperatures and its compactness. PCHEs are high integrity plate type heat exchangers made by chemically etching fluid flow channels into flat metal plates which are then diffusion bonded. This paper will discuss aspects of the design and construction of PCHEs and look at how this technology is being applied to the PBMR.
Numerical Simulation of the Boundary Layer Transition in Turbomachinery Flows
Authors: Thermann Hans , Müller Michael , Niehuis Reinhard
Published: July 2014

The objective of the presented work is to investigate models which simulate boundary layer transition in turbomachinery flows. This study focuses on separated-flow transition. Computations with different algebraic transition models are performed three-dimensionally using an implicit Navier-Stokes flow solver. Two different test cases have been chosen for this investigation: First, a linear transonic compressor cascade, and second an annular subsonic compressor cascade. Both test cases show three-dimensional flow structures with large separations at the side-walls. Additionally, laminar separation bubbles can be observed on the suction and pressure side of the blades of the annular subsonic cascade whereas a shock-induced separation can be found on the suction side of the blades of the linear transonic cascade. Computational results are compared with experiments and the effect of transition modeling is analyzed. It is shown that the prediction of the boundary layer development can be substantially improved compared to fully turbulent computations when algebraic transition models are applied.
Improvement of the Accuracy in Gas Turbine Health Determination
Authors: Pinelli M. , Venturini M.
Published: July 2014

Health Monitoring Systems (HMS) based on operating state determination techniques that make use of field measurements are subjected to inaccuracies arising from measurements unreliability due to various kinds of uncertainties (such as sensors faults, measurements inaccuracies, etc.).

In this paper, some techniques to improve the accuracy of gas turbine health state determination are presented:

- a measurement conditioning technique based on the expected and trend values of measurements;

- the evaluation of the best measurements/health parameters combination that should be used with respect to the gas turbine operating state determination.
Development of High-Speed Gas Bearings for High-Power-Density Micro-Devices
Authors: Ehrich F. F. , Jacobson S. A.
Published: July 2014

A 4.2 mm diameter silicon rotor has been operated in a controlled and sustained manner at rotational speeds greater then 1.3 million rpm and power levels approaching 5 W. The rotor, supported by hydrostatic journal and thrust gas bearings, is driven by an air turbine. This turbomachinery/bearing test device was fabricated from single crystal silicon wafers using micro-fabrication etching and bonding techniques. We believe this device is the first micro-machine to operate at a circumferential tip speed of over 300 meters per second, comparable to conventional macro-scale turbomachinery, and necessary for achieving high levels of power density in micro-turbomachinery and micro-electrostatic/ electromagnetic devices.

To achieve this level of peripheral speed, micro-fabricated rotors require stable, low friction bearings for support. Due to the small scale of these devices as well as fabrication constraints that limit the bearing aspect ratio, the design regime is well outside that of more conventional devices. This paper focuses on bearing design and test, and rotordynamic issues for high-speed high-power micro-fabricated devices.
Active Aerodynamic Control of Multi-Stage Axial Compressor Instability and Surge by Dynamically Adjusting the Stator Blades
Authors: Schobeiri M. T.
Published: July 2014

A method of active aerodynamic control and prevention of axial compressor instability and surge is presented. The method is based on dynamically adjusting the stator blades to the compressor interstage unsteady aerodynamics. While concentrating on the active aerodynamic control and prevention of stall, it does not deal with control specific procedures and algorithms. Using a row-by-row dynamic prediction procedure, the dynamic state of the compressor is determined by the blade flow deflection, which is represented by a time dependent modified diffusion factor. For the case that an adverse dynamic operation condition causes the diffusion factor to exceed certain thresholds, the stator blades are adjusted by changing their stagger angle, thus shifting the surge limit beyond its design point. As a result, the compressor can operate at much lower mass flow rates than the steady state performance map allows. The active aerodynamic control method is applied to a single-spool, two shaft power generation gas turbine engine with a multistage compressor. Two complete dynamic engine simulation computations are performed. In the course of the first simulation, the stator-row stagger angles are kept at their design point and the compressor is forced into an unstable operating mode. In the second simulation, under the same adverse engine operation conditions, the stator blade rows are dynamically adjusted thus preventing the inception of instability and surge.
Flow Field Measurements in a Cold Flow Annular Sector Turbine Cascade Test Facility and an Annular Sector Cascade Test Facility Operating at Near-Engine Conditions
Authors: Wiers S.-H. , Fransson T. H. , Rådeklint U. , Annerfeldt M.
Published: July 2014

Aerodynamic investigations in a cold flow annular sector high-pressure turbine cascade test facility and an annular sector cascade facility operating at near-engine conditions are presented. The test section of both facilities is a 36° sector cascade of a modern turbine stator consisting of 6 vanes. The two facilities have been designed in order to gain detailed information concerning film cooled gas turbine vanes. Due to the operation conditions of the hot annular sector cascade it takes over the part of detailed investigations of the influence of film cooling on the heat transfer. In the cold annular sector cascade facility investigations on the aerodynamic behavior of the cascade are performed. Both facilities together will lead to a better understanding of the complicate three-dimensional flow in modern gas turbines. A detailed description of both facilities is given in this paper. Aerodynamic investigations in both facilities were performed. The in- and outlet Mach number and profile Mach number distribution is in good agreement in both of them and shows a periodic flow filed. Aerodynamic performance measurements in the cold flow facility have been conducted by means of a five-hole pneumatic pressure probe traverses 106% of cax downstream of the cascade to gain information about the quality of the flow field across flow passages “+1” and “–1” in terms of yaw angle, pitch angle and primary loss distribution. Comparison with a three dimensional Navier Stokes solvers show a very good agreement with the measurements. In order to deduce the external heat transfer coefficient on the vane a transient test procedure was adopted in the high-pressure hot facility. The dependency of the heat transfer coefficients on the Reynolds number is presented in the paper. The experimental results show reasonable agreement with calculations using a two dimensional boundary layer code.
The 2-Stage Axial Turbine Test Facility “LISA”
Authors: Sell M. , Schlienger J. , Pfau A. , Treiber M. , Abhari R. S.
Published: July 2014

This paper describes the design and construction of a new two stage axial turbine test facility, christened “Lisa”. The research objective of the rig is to study the impact (relevance) of unsteady flow phenomena upon the aerodynamic performance, this being achieved through the use of systematic studies of parametric changes in the stage geometry and operating point. Noteworthy in the design of the rig is the use of a twin shaft arrangement to decouple the stages. The inner shaft carries the load from the first stage whilst the outer is used with an integral torque-meter to measure the loading upon the second stage alone. This gives an accurate measurement of the loading upon the aerodynamically representative second stage, which possesses the correct stage inlet conditions in comparison to the full two stage machine which has an unrealistic axial inlet flow at the first stator. A calibrated Venturi nozzle measures the mass flow at an accuracy of below 1%, from which stage efficiencies can be derived.

The rig is arranged in a closed loop system. The turbine has a vertical arrangement and is connected through a gear box to a generator system that works as a brake to maintain the desired operating speed. The turbine exit is open to ambient pressure. The rig runs at a low pressure ratio of 1.5. The maximum Mach number at stator exit is 0.3 at an inlet pressure of 1.5 bar. The maximum mass flow is 14 kg/sec. Nominal rotor design speed is 3000 RPM. The tip to hub blade ratio is 1.29, and the nominal axial chord is 50 mm. The rig is designed to accommodate a broad range of measurement techniques, but with a strong emphasis upon unsteady flow methods, for example fast response aerodynamic pressure probes for time-resolved flow measurements.

The first section of this paper describes the overall test facility hardware. This is followed by a detailed focus on the torque measurement device including stage efficiency measurements at operating conditions in Lisa. Discussion of measurement techniques completes the paper.