bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerothermodynamics of a High-Pressure Turbine Blade With Very High Loading and Vortex Generators
Authors: Gomes Reinaldo A. , Niehuis Reinhard
Published: January 2011

AITEB-2 is a project where aerothermal challenges of modern high pressure turbine designs are analysed. One of the scopes of the project is to allow for new gas turbine designs with less parts and lighter jet engines by increasing the blade pitch and therefore the aerodynamic blade loading. For transonic profiles this leads to very high velocities on the suction side and shock induced separation is likely to occur. The total pressure loss increase due to flow separation and strong shocks as well as the under-turning of the flow limits the increase of the blade pitch. In this paper experiments using a linear turbine blade cascade with high aerodynamic loading are presented. The blade pitch is increased such that at design conditions a strong separation occurs on the suction side. The experiments were run at high subsonic exit Mach numbers and at Reynolds numbers of 390,000 and 800,000. In order to reduce the flow separation and the aerodynamic losses, air jet vortex generators are used which create streamwise vortices prior to the separation start. Since in high pressure turbine blades film cooling is widely used, also the influence of film cooling both with and without using vortex generators is analysed. Film cooling is provided on the suction side by two rows of cylindrical holes. The paper provides an analysis of the influence of different main flow conditions, film cooling and vortex generators on total pressure loss, heat transfer and film cooling effectiveness. The experiments show that the vortex generators as well as the film cooling reduce flow separation and total pressure losses. Effects are also seen in the local heat transfer, especially with enhanced heat transport in the region with flow separation. The cases presented in this paper deal with complex flow phenomena which are challenging to be predicted with modern numerical tools correctly. Therefore the experimental data serve as a comprehensive data base for CFD validation in the AITEB-2 project.
Expanding Fuel Flexibility Capability in GE’s Aeroderivative Engines
Authors: Wisniewski Karl J. , Handelsman Steve
Published: January 2011

GE Aviation, through its network of gas turbine OEM’s, has received an increasing number of inquiries and request for quotes for the use of non-standard gas fuels in aero-derivative gas turbine applications. Factors influencing this trend include: increased development of LNG production facilities, increased availability of bio-fuels, lack of availability of standard fuels, reduced acceptance of flaring process gases, and more stringent policies on exhaust emissions. These inquiries and requests propose the use of gas fuels with higher levels of C2+ constituents, or concentrations of hydrogen greater than 5%, or fuels with ever increasing concentrations of high inert gases. Responding to this interest, GE has launched several programs to expand the capability of both SAC (Single Annular Combustor) and Dry Low Emission (DLE) combustion systems. Recent SAC fuel system design enhancements have enabled the LM2500 gas turbine family to operate with either of two, high hydrogen content gases: COG (Coke Oven Gas), a medium BTU fuel (25–35 MWI (Modified Wobbe Index)); or with SYNGAS, a bio-derived, low BTU fuel, (12–14 MWI). To support expanding the DLE capabilities, a series of combustion rig tests and full-scale engine tests have been conducted. Combustion rig testing at one of GE’s Global Research Centers (GRC) has focused on non-standard gas fuels with high concentrations of C2+ constituents. The higher flame speeds of these fuels increase the potential for flashback, and the resulting potential for premature combustor and/or fuel nozzle distress. These tests have allowed GE to more than double the allowable amount of C2+ concentrations in fuel. An LM2500Plus DLE engine recently completed a series of high inert gas fuel testing designed to assess combustor operability and exhaust emissions. This paper intends to summarize the advances GE has made in expanding the range of gas fuels that can be accommodated in the LM2500 and LM6000 product lines.
Cobalt Based Antifretting Coatings
Authors: Fiala Petr , Hajmrle Karel
Published: January 2011

Some cobalt based coatings have excellent antifretting properties when rubbed against titanium alloy hardware. The coatings are presently used in the gas turbine industry for specific antifretting applications. Their superior performance compared to the current art CuNiIn coatings has been demonstrated. This paper discusses the influence of coating structure on its mechanical properties and antifretting performance. The coating structure can be greatly modified by changing the coating application method (HVOF or plasma spraying). HVOF (High Velocity Oxygen-Fuel) and plasma spray equipment together with TriplexPro™ 200 gun configured to spray HVOF and plasma type coatings were used. The resulting coating properties can be tailored to specific application requirements encountered in aircraft engines and other industrial applications.
Combined Blowing and Suction to Control Both Midspan and Endwall Losses in a Turbomachinery Passage
Authors: Bloxham Matthew J. , Bons Jeffrey P.
Published: January 2011

A flow control scheme was implemented in a low pressure turbine cascade that simultaneously mitigated profile and endwall losses using midspan vortex generator jets (VGJs) and endwall suction. The combined system had an approximate zero-net mass flux. During the design, a theoretical model was used that effectively predicted the trajectory of the passage vortex using inviscid results obtained from two-dimensional CFD. The model was used in the design of two flow control approaches, the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control along the passage vortex (PV) trajectory. The redirection approach attempted to alter the trajectory of the PV with the judicious placement of suction holes. A potential flow model was created to aid in the design of the redirection approach. The model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade. Detailed total pressure loss wake surveys were measured while matching the suction and VGJ mass flow rates, for the removal and redirection approaches at ReCx = 25000 and blowing ratio, B, of 2. When compared with the no control results, the addition of VGJs and endwall suction reduced the wake losses by 69% (removal) and 68% (redirection). The majority of the total pressure loss reduction resulted from the spanwise VGJs while the suction schemes provided modest additional reductions (<2%). At ReCx = 50000 the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-averaged total pressure loss reductions of up to 28% were measured in the wake at ReCx = 50000, B = 0, with applied endwall suction (compared to no suction at ReCx = 50000), at which point, the loss core of the PV was almost completely eliminated. A system analysis showed that only 23% of the total power gained was needed to power the flow control scheme.
Application of Squeeze-Film Dampers to a Large Centrifugal Compressor
Authors: Memmott Edmund A.
Published: January 2011

This paper discusses the application of squeeze-film dampers in series with the tilting pad bearings of a large centrifugal compressor. The compressor was first factory tested with non-damper bearings and there was some subsynchronous vibration. Damper bearings were installed and the subsynchronous vibration was gone. The compressor shipped with damper bearings. Analytical and test results will be presented for both rotor dynamic systems. Design considerations in the use of squeeze-film dampers with tilting pad journal bearings will be reviewed.
Hot Streak Migration in a Turbine Stage: Integrated Design to Improve Aero-Thermal Performance
Authors: Basol A. M. , Jenny P. , Ibrahim M. , Kalfas A. , Abhari R. S.
Published: January 2011

Hot streaks can cause localized hot spots on the blade surfaces in a high-pressure turbine, increasing the heat load locally and even leading to material loss in regions such as the rotor blade tip. This study explores numerically the effect of the hot streak’s orientation at the stator inlet on the rotor blade heat load and on the tip in particular. The inlet boundary conditions are taken from the hot streak experiment conducted in the axial turbine facility “LISA” at ETH Zurich. Using a particle tracking tool in conjunction with time-resolved simulations a detailed analysis of the migration pattern of the hot streak is performed and the underlying mechanisms are discussed. The effect of clocking the hot streak from mid-pitch to the stator pressure side and in the opposite direction is examined. By clocking this particular hot streak even 10% of the stator pitch towards the pressure side up to 24 K reduction in the rotor blade tip adiabatic wall temperatures is achieved. The validity of the particle migration pattern is also tested on an elliptical hot streak shape. Changing the orientation of the hot streak at the inlet plane a heat load re-distribution parallel to the migration characteristics is observed. Finally, based on the observations made, the implications for an integrated combustor-turbine design strategy are discussed.
Probabilistic Structural Analysis of Annular Deformation Resistance Welding Process
Authors: Pai Shantaram S. , Bhattacharya N. , Nagpal Vinod K.
Published: January 2011

An effort has been ongoing to integrate manufacturing process simulations with probabilistic structural analyses in order to capture the important impacts of manufacturing uncertainties on component stress levels and life. A physics-based manufacturing process simulation code has been linked to the NESSUS structural analysis code to analyze annular deformation resistance welding manufacturing process. This paper describes the methodology developed to perform this integration, including an example. Although this effort is underway, particularly for fuller integration of a probabilistic analysis, the progress to date has been encouraging and a software interface that implements the methodology has been developed. The purpose of this paper is to report this development.
Operating Experience With the Latest Upgrade of Alstom’s Sequential Combustion GT26 Gas Turbine
Authors: Hiddeman Matthias , Marx Peter
Published: January 2011

The GT26 gas turbine provides an additional degree of flexibility as the engine operates at high efficiencies from part load to full load while still maintaining low NOx emissions. The sequential combustion, with the EV burner as the basis for this flexibility also extends to the ability to handle wide fluctuations in fuel gas compositions. Increased mass flow was the main driver for the latest GT26 upgrade, resulting in substantial performance improvements. In order to ensure high levels of reliability and availability Alstom followed their philosophy of evolutionary steps to continuously develop their gas turbines. A total of 47 engines of this upgrade of the GT26 gas turbine have been ordered worldwide to date (Status: January 2010) enhancing the business case of power generators by delivering superior operational and fuel flexibility and combined cycle efficiencies up to and beyond 59%.
Target Size Effects on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Ceramic Ball Projectiles
Authors: Choi Sung R. , Ra´cz Zsolt
Published: January 2011

Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were determined at ambient temperature using impact velocities ranging from 25 to 150 m/s by 1.59-mm diameter silicon nitride ball projectiles. Targets in flexure bar configuration with two different thicknesses of 1 and 2 mm were impacted under a fully supported condition. The degree of impact damage as well as of post-impact strength degradation increased with increasing impact velocity, increased with decreasing target thickness, and was greater in SN282 than in AS800 silicon nitride regardless of target thickness. The critical impact velocity, in which targets fractured catastrophically, decreased monotonically with decreasing target thickness and was lower in SN282 than in AS800. Backside cracking was dominant in both AS800 and SN282 target specimens with a thickness of 1 mm, occurring from an impact velocity of 50 m/s. A backside cracking analysis based on the elastic foundation approach was made as a function of target thickness. Overall, FOD by ceramic projectiles was significantly greater than that by hardened metallic counterparts.
Highly Loaded Low-Pressure Turbine: Design, Numerical, and Experimental Analysis
Authors: Schmitz J. T. , Morris S. C. , Ma R. , Corke T. C. , Clark J. P. , Koch P. J. , Puterbaugh S. L.
Published: January 2011

The performance and detailed flow physics of a highly loaded, transonic, low-pressure turbine stage has been investigated numerically and experimentally. The mean rotor Zweifel coefficient was 1.35, with dh/U2 = 2.8, and a total pressure ratio of 1.75. The aerodynamic design was based on recent developments in boundary layer transition modeling. Steady and unsteady numerical solutions were used to design the blade geometry as well as to predict the design and off-design performance. Measurements were acquired in a recently developed, high-speed, rotating turbine facility. The nozzle-vane only and full stage characteristics were measured with varied mass flow, Reynolds number, and free-stream turbulence. The efficiency calculated from torque at the design speed and pressure ratio of the turbine was found to be 90.6%. This compared favorably to the mean line target value of 90.5%. This paper will describe the measurements and numerical solutions in detail for both design and off-design conditions.
Numerical Simulation of Sand Erosion in a Transonic Compressor Rotor
Authors: Suzuki Masaya , Yamamoto Makoto
Published: January 2011

Sand erosion is a phenomenon whereby solid particles impinging on a wall cause serious mechanical damage to the wall surface. Aircraft engines operating in a particulate environment are subjected to deterioration of performance and life due to sand erosion. In particular, the compressors of aircraft engines are severely affected. In our previous study, the authors developed code for predicting sand erosion three-dimensionally and subsequently applied it to a subsonic axial compressor. However, design trends for modern compressors continue to increase blade loading and decrease aspect ratios. Additionally, modern compressors are transonic. To aid in the design and deepen understanding, it is important to study sand erosion in such transonic compressors. Herein, Rotor 37 was used in sand erosion simulations. The particle motion, erosion rate were investigated.
Computational Study of Geometric Parameter Influence on Aggressive Inter-Turbine Duct Performance
Authors: Couey Paul T. , McKeever Craig W. , Malak Malak F. , Balamurugan S. , Raju Veeraraghava H. , Dhinagaran R.
Published: January 2011

Modern direct-drive turbofan engines typically have the fan turbine designed at significantly higher diameter than the gas producer turbine. Furthermore, the gas turbine industry is being pushed to shorten engine length with the goal of reducing weight. This results in a need to design very aggressive inter-turbine-ducts (ITD’s) that have high endwall slopes. The gas turbine design cycle typically begins with conceptual design where many engine configuration iterations are made. During conceptual design, there usually is little firm geometric definition or time for detailed CFD studies on aggressive ITD’s. This can cause a large amount of risk to the engine development schedule and cost if the space allocated for the ITD during conceptual design is found to be insufficient later in the design cycle. Therefore, simple analytical tools for accurately assessing the risk of an ITD in conceptual design are important. The gas turbine industry is familiar with the Sovran and Klomp annular diffuser performance chart [1] as a conceptual design tool for assessing ITD’s. However, its applicability to modern gas turbine ducts with high endwall slope is limited. The location of the maximum pressure recovery for a given length, the Cp* line, considers only two geometric parameters: area ratio and normalized length. The chart makes no distinction of risk of flow separation regarding the level of slope or the pitch-wise turning in the duct. However, intuition would suggest that a high slope duct would have more risk of separation than an equivalent area ratio duct with low slope. Similarly, a duct that turns the flow from axial to radial would be expected to be riskier than a pure axial duct. To help assess the interaction of duct slope and pitch-wise turning with area ratio and length, an analytical Design of Experiments (DOE) was run using approximately sixty different duct configurations. The DOE was carried out using 3D, steady CFD analysis. The results of the DOE are presented with insights provided into how the Cp* line may shift as a function of duct slope. Of particular interest is that slope by itself does not work particularly well as a risk indicator. However, a combination of new area ratio-length and slope-length parameters was found to segregate ducts between separated and non-separated cases.
A CFD Study of Circumferential Groove Casing Treatments in a Transonic Axial Compressor
Authors: Chen Haixin , Huang Xudong , Shi Ke , Fu Song , Bennington Matthew A. , Morris Scott C. , Ross Mark , McNulty Scott , Wadia Aspi
Published: January 2011

Numerical investigations were conducted to predict the performance of a transonic axial compressor rotor with circumferential groove casing treatment. The Notre Dame Transonic Axial Compressor (ND-TAC) was simulated by Tsinghua University with an in-house CFD code (NSAWET) for this work. Experimental data from the ND-TAC were used to define the geometry, boundary conditions and data sampling method for the numerical simulation. These efforts, combined with several unique simulation approaches, such as non-matched grid boundary technology to treat the periodic boundaries and interfaces between groove grids and the passage grid, resulted in good agreement between the numerical and experimental results for overall compressor performance and radial profiles of exit total pressure. Efforts were made to study blade level flow mechanisms to determine how the casing treatment impacts the compressor’s stall margin and performance. The flow structures in the passage, the tip gap and the grooves as well as their mutual interactions were plotted and analyzed. The flow and momentum transport across the tip gap in the smooth wall and the casing treatment configurations were quantitatively compared.
Modal Frequency Response of a Four-Pad Tilting Pad Bearing With Spherical Pivots, Finite Pivot Stiffness and Different Pad Preloads
Authors: Dimond Timothy W. , Younan Amir A. , Allaire Paul E. , Nicholas John C.
Published: January 2011

Tilting pad journal bearings (TPJBs) provide radial support for rotors in high-speed machinery. Since the tilting pads cannot support a moment about the pivot, self-excited cross-coupled forces due to fluid-structure interactions are greatly reduced or eliminated. However, the rotation of the tilting pads about the pivots introduces additional degrees of freedom into the system. When the flexibility of the pivot results in pivot stiffness that is comparable to the equivalent stiffness of the oil film, then pad translations as well as pad rotations have to be considered in the overall bearing frequency response. There is significant disagreement in the literature over the nature of the frequency response of TPJBs due to non-synchronous rotor perturbations. In this paper, a bearing model that explicitly considers pad translations and pad rotations is presented. This model is transformed to modal coordinates using state-space analysis to determine the natural frequencies and damping ratios for a four-pad tilting pad bearing. Experimental static and dynamic results were previously reported in the literature for the subject bearing. The bearing characteristics as tested are considered using a thermoelastohydrodynamic (TEHD) model. The subject bearing was reported as having an elliptical bearing bore and varying pad clearances for loaded and unloaded pads during the test. The TEHD analysis assumes a circular bearing bore, so the average bearing clearance was considered. Because of the ellipticity of the bearing bore, each pad has its own effective preload, which was considered in the analysis. The unloaded top pads have a leading edge taper. The loaded bottom pads have finned backs and secondary cooling oil flow. The bearing pad cooling features are considered by modeling equivalent convective coefficients for each pad back. The calculated bearing full stiffness and damping coefficients are also reduced non-synchronously to the eight stiffness and damping coefficients typically used in rotordynamic analyses and are expressed as bearing complex impedances referenced to shaft motion. Results of the modal analysis are compared to a two degree-of-freedom second-order model obtained via a frequency-domain system identification procedure. Theoretical calculations are compared to previously published experimental results for a four-pad tilting pad bearing. Comparisons to the previously published static and dynamic bearing characteristics are considered for model validation. Differences in natural frequencies and damping ratios resulting from the various models are compared, and the implications for rotordynamic analyses are considered.
Design, Construction and Modeling of a Flexible Rotor Active Magnetic Bearing Test Rig
Authors: Mushi Simon E. , Lin Zongli , Allaire Paul E.
Published: January 2011

The successful industrial application of flexible rotors supported on active magnetic bearings (AMBs) requires careful attention not only to rotordynamic design aspects, but also to electromagnetic and feedback control design aspects. This paper describes the design, construction and modeling process for an AMB test rig which contains a 1.23m long flexible steel rotor, with a mass of 44.9 kg and two gyroscopic disks. The rotor typifies a small industrial centrifugal compressor designed to operate above 12,000 rpm and the first bending natural frequency. There are four AMBs — two AMBs at the shaft ends to support the shaft with a combined load capacity of 2600N and two additional AMBs at the mid and quarter spans to allow for the application of simulated destabilizing fluid or electromagnetic forces to the rotor. Simulated aerodynamic cross coupling stiffness values are to be applied to the rotor through these two internal AMBs with the goal of developing stabilizing robust controllers. The unique design allows multiple support and disturbance locations providing the ability to represent a variety of machine configurations, e.g., between bearing and overhung designs. The shaft transfer function in lateral movement has been developed with finite element model and then verified by experimental frequency response measurements. Models for the power amplifiers, position sensors, signal conditioning and data converter hardware were developed, verified experimentally and included in the overall system model. A PID controller was developed and tuned to levitate the rotor and enable further system characterization.
Assessment of Future Aero Engine Designs With Intercooled and Intercooled Recuperated Cores
Authors: Kyprianidis Konstantinos G. , Gro¨nstedt Tomas , Ogaji S. O. T. , Pilidis P. , Singh R.
Published: January 2011

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. Conventional turbofan designs however that reduce CO2 emissions — such as increased OPR designs — can increase the production of NOx emissions. In the present work, funded by the European Framework 6 collaborative project NEWAC, an aero engine multidisciplinary design tool, TERA2020, has been utilised to study the potential benefits from introducing heat-exchanged cores in future turbofan engine designs. The tool comprises of various modules covering a wide range of disciplines: engine performance, engine aerodynamic and mechanical design, aircraft design and performance, emissions prediction and environmental impact, engine and airframe noise, as well as production, maintenance and direct operating costs. Fundamental performance differences between heat-exchanged cores and a conventional core are discussed and quantified. Cycle limitations imposed by mechanical considerations, operational limitations and emissions legislation are also discussed. The research work presented in this paper concludes with a full assessment at aircraft system level that reveals the significant potential performance benefits for the inter-cooled and intercooled recuperated cycles. An intercooled core can be designed for a significantly higher OPR and with reduced cooling air requirements, providing a higher thermal efficiency than could otherwise be practically achieved with a conventional core. Variable geometry can be implemented to optimise the use of the intercooler for a given flight mission. An intercooled recuperated core can provide high thermal efficiency at low OPR values and also benefit significantly from the introduction of a variable geometry low pressure turbine. The necessity of introducing novel lean-burn combustion technology, to reduce NOx emissions, at cruise as well as for the landing and take-off cycle, is demonstrated for both heat-exchanged cores and conventional designs. Significant benefits in terms of NOx reduction are predicted from the introduction of a variable geometry low pressure turbine in an intercooled core with lean-burn combustion technology.
Flashback Limits of Premixed H2/CH4 Flames in a Swirl-Stabilized Combustor
Authors: Shelil Nasser , Griffiths Anthony , Bagdanavicius Audrius , Syred Nick
Published: January 2011

CFD modeling is used to simulate the combustion and flashback behavior of H2/CH4 fuel blends with air in a premixed swirl burner using a three dimensional–finite volume model. Preliminary work was performed to calculate the laminar flame speed for H2/CH4 blends from pure methane up to pure hydrogen at various pressures, temperatures and equivalence ratios by using CHEMKIN, for pure fuels, and a new approximation based on the gravimetric mixture ratio, for the fuel blends. Then, the numerical values for laminar flame speed were fed to a FLUENT CFD model to create a PDF table for turbulent premixed combustion calculations and flashback studies. Flashback limits were defined and determined for H2/CH4 blends ranging from 0% (pure methane) up to 100% (pure hydrogen) based on the volumetric composition at atmospheric pressure and 300K for various equivalence ratios. The simulations were compared with experimental measurements at atmospheric pressure for two fuel blends with γ of 0.15 and 0.3 and showed best fit for equivalence ratios less than 0.75 to 0.8. The work was then extended to include simulation studies to investigate the effect of operating pressure and raw gases temperature on flame stability and showed a high dependence on both operating pressure and raw gases temperature.
Film Riding Leaf Seals for Improved Shaft Sealing
Authors: Grondahl Clayton M. , Dudley James C.
Published: January 2011

Turbine shaft seals are vulnerable to rubs caused by thermal distortion, mis-alignment and rotor dynamic vibration that are often not well understood. When seals rub as a machine is brought up to operating conditions performance is compromised due to increased seal leakage. Much effort has been extended in recent years to develop seals that mitigate those losses. This paper presents a seal design with segmented film riding runners capable of non-contacting seal operation during rotor transients. Operating differential seal pressure displaces seal leaves and attached runners toward the rotor surface until balanced by hydrostatic and hydrodynamic lift. Sufficient radial range of operation is provided to follow the rotor seal surface during transients while maintaining a small seal clearance. Seal design features and function will be described and illustrated along with analysis of forces and motions for a sample application. Planned modeling and testing will also be presented. This concept promises enhanced shaft sealing by combining a leaf seal structure that provides a large range of motion to avoid rubs during startup and shutdown with runner elements capable of generating hydrostatic and hydrodynamic lift forces to maintain shaft–seal separation during all rotor displacement transients. Improved turbine performance from small operating seal clearance and extended seal life without rubs are expected benefits of the Film Riding Pressure Actuated Leaf Seal (FRPALS).
First Unsteady Pressure Measurements With a Fast Response Cooled Total Pressure Probe in High Temperature Gas Turbine Environments
Authors: Mersinligil Mehmet , Brouckaert Jean-Franc¸ois , Desset Julien
Published: January 2011

This paper presents the first experimental engine and test rig results obtained from a fast response cooled total pressure probe. The first objective of the probe design was to favor continuous immersion of the probe into the engine to obtain time series of pressure with a high bandwidth and therefore statistically representative average fluctuations at the blade passing frequency. The probe is water cooled by a high pressure cooling system and uses a conventional piezo-resistive pressure sensor which yields therefore both time-averaged and time-resolved pressures. The initial design target was to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (1100–1400K) with a bandwidth of at least 40kHz and in the long term at combustor exit (2000K or higher). The probe was first traversed at the turbine exit of a Rolls-Royce Viper turbojet engine, at exhaust temperatures around 750 °C and absolute pressure of 2.1bars. The probe was able to resolve the high blade passing frequency (≈23kHz) and several harmonics up to 100kHz. Besides the average total pressure distributions from the radial traverses, phase-locked averages and random unsteadiness are presented. The probe was also used in a virtual three-hole mode yielding unsteady yaw angle, static pressure and Mach number. The same probe was used for measurements in a Rolls-Royce intermediate pressure burner rig. Traverses were performed inside the flame tube of a kerosene burner at temperatures above 1600 °C. The probe successfully measured the total pressure distribution in the flame tube and typical frequencies of combustion instabilities were identified during rumble conditions. The cooling performance of the probe is compared to estimations at the design stage and found to be in good agreement. The frequency response of the probe is compared to cold shock tube results and a significant increase in the natural frequency of the line-cavity system formed by the conduction cooled screen in front of the miniature pressure sensor were observed.
Comparison Between Two-Shaft Simple and Single-Shaft Recuperated Brayton Cycles Using Different Types of Gaseous Fuels
Authors: Malkogianni A. K. , Tourlidakis A. , Polyzakis A. L.
Published: January 2011

Geopolitical issues give rise to problems in the smooth and continuous flow of oil and natural gas from the production countries to the consumers’ development countries. In addition, severe environmental issues such as greenhouse gas emissions, eventually guide the consumers to fuels more suitable to the present situation. Alternative fuels such as biogas and coal gas have recently become more attractive because of their benefits, especially for electricity generation. On the other hand, the use of relatively low heating value fuels has a significant effect to the performance parameters of gas turbines. In this paper, the impact of using four fuels with different heating value in the gas turbine performance is simulated. Based on the high efficiency and commercialization criteria, two types of engines are chosen to be simulated: two-shaft simple and single-shaft recuperated cycle gas turbines. The heating values of the four gases investigated, correspond to natural gas and to a series of three gases with gradually lower heating values than that of natural gas. The main conclusions drawn from this design point (DP) and off-design (OD) analysis is that, for a given TET, efficiency increases for both engines when gases with low heating value are used. On the contrary, when power output is kept constant, the use of gases with low heating value will result in a decrease of thermal efficiency. A number of parametric studies are carried out and the effect of operating parameters on performance is assessed. The analysis is performed with customized software, which has been developed for this purpose.
Filter Failure During High Humidity Conditions
Authors: Wilcox Melissa , Ransom David , Delgado-Garibay Hector
Published: January 2011

The operation of a gas turbine, by its basic design, requires it to ingest enormous quantities of air. Even in relatively clean environments, a gas turbine may ingest hundreds of pounds of foreign matter each year of various sizes. Also, the more advanced the turbine design, the more sensitive it is to the quality of the air ingested. Filtration is applied to the inlet air to provide protection against the effects of contaminated air. Filters used with gas turbines are designed to remove a specified amount of particular contaminants. One type of filter is the high efficiency filter. These are often installed in order to capture particles less than ten microns. These filters are sometimes susceptible to water penetration. If the filter is not designed to remove water, then water can absorb soluble contaminants and carry them through the filter into the inlet of the gas turbine. In the case where harmful contaminants travel through the filter with the water, this can be potentially damaging to the gas turbine. For example, salt is soluble and can lead to hot corrosion in the turbine section. If water is allowed to reach the high efficiency filters then the water may carry contaminants through the gas turbine. In order to mitigate this phenomenon, many filter systems have mist removal systems. Even with a good mist removal system, humidity can reach the high efficiency filters. As humid air flows past the high efficiency filters, the decrease in air pressure can lead to water condensing on the filters. A procedure is presented in this paper which shows that filters that have been fully or near fully loaded with contaminants may experience condensation in an environment with high humidity. This paper reviews a thermodynamic analysis that is used to determine the conditions that must be met in order to experience this phenomenon. The possible occurrence of condensation further demonstrates the criticality of replacing inlet filters as soon as the filter pressure loss shows an upward trend.
From the JEFF (B) to the SSC and Beyond, TF Marine Gas Turbines: A Development Study
Authors: Scheugenpflug Hermann , Wilcoxson Tony , Luz Michael
Published: January 2011

This paper will trace the history and development of the TF series marine gas turbines over the last 40 years leading up to today’s candidate for the US Navy Ship-to-Shore Connector (SSC) program, the model TF60B, and its planned successor the TF70. The TF60B engine traces its ancestry to helicopter engines designed by Avco-Lycoming in the early 1960s. This paper will review the extensive experience-based development of the original T55-L-5 into the first of the marine engines (the TF20) and then through the TF25, TF35, TF40, to today’s ETF40B, TF50A and TF60B. Specific improvements and power increases will be described with each significant model revision along with the unique requirements of the air cushion vehicle and similar platforms that were powered by these engines. The specific characteristics that define the TF series engine as proven marine propulsion units will be discussed in each of the subsequent engine models. The paper will show the steady progression of advancement in aerodynamics, materials, temperatures, controls and structures leading to today’s next generation engine, the TF60B, with the path to yet higher levels of power for the future. The current evolutionary TF60B engine will be described in terms of architecture and development philosophy highlighting the foresight of the original design to accommodate the increments of growth without significantly increasing the frame size of the gas turbine.
Evaluation of Turbine Airfoil Cooling Holes by Transient Infrared Methods
Authors: Allen Jason R. , Crosby Jared M. , Uhl Christopher J. , McCartt Bianca M.
Published: January 2011

Design margins in film-cooled turbine airfoils continue to shrink as specific fuel consumption and performance requirements drive new cooling technology. As a consequence, today’s airfoil heat transfer designs are more sensitive to engine aerodynamic and thermal loads, hot gas path profiles, and manufacturing variability than previous designs. Compounding the challenges of airfoil heat transfer design has been the continued use of inspection practices developed for legacy designs. Advancement of thermal inspection techniques for today’s advanced thermally sensitive airfoils needs to be addressed and advanced in conjunction with advanced cooling designs. Infrared non-destructive evaluation (NDE) techniques offer a number of solutions to inspect turbine airfoils for proper thermal performance before entry into service and during inservice repair. A prototype infrared inspection system demonstrated detection of blocked film cooling holes in turbine airfoils. The system implements IR thermal transient techniques to identify flawed film holes based on the IR thermal signature obtained for each film hole. Furthermore, the approach utilizes robotics, system automation, image processing, and a simple algorithm to discern flawed holes reliably. Traditionally, identifying blocked and undersized holes is manually performed with undersized pin gauges and water flow visualization. These manual processes are qualitative and subject to operator interpretation. Conversely, the IR approach eliminates operator subjectivity by using quantitative metrics. This approach resulted in a 35% reduction in inspection cycle time permitting reallocation of operators to value added tasks; thereby reducing manufacturing and inspection costs. Beyond these initial benefits, the approach used provides a basis for continued developments in turbine airfoil NDE inspection and heat transfer technology development.
Emissions and Noise Pollution Diagnosis of a Turbogas Power Plant During Commissioning Service
Authors: Rodri´guez Norberto Pe´rez , Tamariz Erik Rosado , Illescas Rafael Garci´a
Published: January 2011

This work is focused on the diagnosis of behavior, from the point of view of control emissions and noise level, of a power Turbogas plant during the process of commissioning, to guarantee that its operation complies with national and international standards. The environmental diagnosis of the power plant was developed as part of the performance evaluation of the unit. The conditions of the unit evaluation include operation at base load and partial load, as well as time periods for load changes. The evaluated power plant consists of an aeroderivative gas turbine installed in a simple cycle, operating with a cooling system (chiller) installed in the urban zone of Mexico City. Therefore, it should comply with the legislation and regulations of the city concerning air pollution and allowed noise, besides the international standards established by the manufacturer. The study includes emissions measurements using a Continuous Emissions Monitoring System installed in-situ, previously calibrated and checked during and after the test which was found inside the permissible deviation of 3%. Measurements were recorded at intervals of 5 minutes during test periods of 110 minutes for each load and 45 minutes for load changes. On the other hand, noise pressure evaluation was carried out in near field as well as far field produced by the power plant during operation. Measurements were carried out by using precision instruments installed specifically for it. A temporary system for obtaining data was used to monitoring the environmental conditions every 30 seconds. It was possible to verify that the turbogenerator complies with all noise levels and contaminant emissions requirements and regulations according to the limits established by the manufacturer and national and international standards.
Analysis of Unsteady Tip and Endwall Heat Transfer in a Highly Loaded Transonic Turbine Stage
Authors: Shyam Vikram , Ameri Ali , Chen Jen-Ping
Published: January 2011

In a previous study, vane-rotor shock interactions and heat transfer on the rotor blade of a highly loaded transonic turbine stage were simulated. The geometry consists of a high pressure turbine vane and downstream rotor blade. This study focuses on the physics of flow and heat transfer in the rotor tip, casing and hub regions. The simulation was performed using the URANS (Unsteady Reynolds-Averaged Navier-Stokes) code MSU-TURBO. A low Reynolds number k-ε model was utilized to model turbulence. The rotor blade in question has a tip gap height of 2.1% of the blade height. The Reynolds number of the flow is approximately 3×106 per meter. Unsteadiness was observed at the tip surface that results in intermittent ‘hot spots’. It is demonstrated that unsteadiness in the tip gap is governed by inviscid effects due to high speed flow and is not strongly dependent on pressure ratio across the tip gap contrary to published observations that have primarily dealt with subsonic tip flows. The high relative Mach numbers in the tip gap lead to a choking of the leakage flow that translates to a relative attenuation of losses at higher loading. The efficacy of new tip geometry is discussed to minimize heat flux at the tip while maintaining choked conditions. In addition, an explanation is provided that shows the mechanism behind the rise in stagnation temperature on the casing to values above the absolute total temperature at the inlet. It is concluded that even in steady mode, work transfer to the near tip fluid occurs due to relative shearing by the casing. This is believed to be the first such explanation of the work transfer phenomenon in the open literature. The difference in pattern between steady and time-averaged heat flux at the hub is also explained.
Overall Effectiveness for a Film Cooled Turbine Blade Leading Edge With Varying Hole Pitch
Authors: Dyson Thomas E. , Bogard Dave G. , Piggush Justin D. , Kohli Atul
Published: January 2011

Overall effectiveness, φ, for a simulated turbine blade leading edge was experimentally measured using a model constructed with a relatively high conductivity material selected so that the Biot number of the model matched engine conditions. The model incorporated three rows of cylindrical holes with the center row positioned on the stagnation line. Internally the model used an impingement cooling configuration. Overall effectiveness was measured for pitch variation from 7.6d to 9.6d for blowing ratios ranging from 0.5 to 3.0, and angle of attack from −7.7° to +7.7°. Performance was evaluated for operation with a constant overall mass flow rate of coolant. Consequently when increasing the pitch, the blowing ratio was increased proportionally. The increased blowing ratio resulted in increased impingement cooling internally and increased convective cooling through the holes. The increased internal and convective cooling compensated, to a degree, for the decreased coolant coverage with increased pitch. Performance was evaluated in terms of laterally averaged φ, but also in terms of the minimum φ. The minimum φ evaluation revealed localized hot spots which are arguably more critical to turbine blade durability than the laterally averaged results. For small increases in pitch there was negligible decrease in performance.
On the Frequency Response of an Axisymmetric Non-Flat Spinning Disk
Authors: Khorasany Ramin M. H. , Hutton Stanley G.
Published: January 2011

For rotating disks, the effect of axisymmetric runout is of interest. This study examines the frequency characteristics of thin rotating discs subjected to axisymmetric non-flatness. The equations of motion used are based on Von Karman’s plate theory. First, the eigenfunctions of the stationary disk problem corresponding to the stress function and transverse displacement are found. These eigenfunctions produce an equation that can be used in the Gelrkin’s method. The initial nonflatness is assumed to be a linear combination of the eigenfunctions of the transverse displacement of the stationary disk problem. Since the initial non-flatness is assumed to be axisymmetric, only eigenfunctions with no nodal diameters are considered to approximate the initial runout. It is supposed that the disk bending deflection is small compared to disk thickness, so we can ignore the second-order terms in the governing equations corresponding to transverse displacement and stress function. After simplifying and discretizing the governing equations of motion, we can obtain a set of coupled equations of motion which takes the effect of initial axisymmetric runout into account. These equations are then used to study the effect of initial runout on the frequency response of the stationary disk. It is found that the initial runout increases the frequencies of the oscillations of a stationary disk. In the next step, we study the effect of initial non-flatness on the critical speed behavior of a spinning disk.
Technical Challenges for Commercial Supersonic Propulsion
Authors: Povinelli Louis A.
Published: January 2011

The NASA Supersonics Project is focused on overcoming the major technical challenges associated with the development of commercial supersonic flight. The NASA Project has identified a number of technical issues that must be overcome in order for this mode of flight to become practical. In particular, the propulsion technologies must meet all of the current subsonic engine noise and emissions regulations at takeoff and landing, as well as acceptable particulate and water emissions at high altitude. High specific thrust will be required, and the effect of shocks associated with the engine inlets, nacelles and exhaust plumes must be minimized in order to achieve a low boom signature. High temperature, light weight materials are vital to achieving acceptable long range durability and efficiency. The main emphasis of this paper will be concerned with the improvements required for the propulsion system in order to achieve the goals established over the 2015 to 2030 time period. The need to successfully integrate the engine with the vehicle remains a critical issue that needs to be accomplished. This presentation presents the ongoing research activities toward achieving these goals.