bluuebunny/crossref_metadata_2025 huggingface dataset:
A Generic Approach for Gas Turbine Adaptive Modeling
Authors: Visser W. P. J. , Kogenhop O. , Oostveen M.
Published: November 2008

For gas turbine engine performance analysis, a variety of simulation tools is available. In order to minimize model development and software maintenance costs, generic gas turbine system simulation tools are required for new modeling tasks. Many modeling aspects remain engine specific however and still require large implementation efforts. One of those aspects is adaptive modeling. Therefore, an adaptive modeling functionality has been developed that can be implemented in a generic component based gas turbine environment. A single component in a system modeling environment is able to turn any new or existing model into an adaptive model without extra coding. The concept has been demonstrated in the GSP gas turbine modeling environment. An object-oriented architecture allows automatic addition of the necessary equations for the adaptation to measurement values. Using the adaptive modeling component, the user can pre-configure the adaptive model and quickly optimize gas path diagnostics capability using experimentation with field data. The resulting adaptive model can be used by maintenance engineers for diagnostics. In this paper the integration of the adaptive modeling function into a system modeling environment is described. Results of a case study on a large turbofan engine application are presented.
Component Map Generation of a Gas Turbine Using Genetic Algorithms
Authors: Kong Changduk , Kho Seonghee , Ki Jayoung
Published: November 2008

In order to estimate the precise performance of the existing gas turbine engine, the component maps with more realistic performance characteristics are needed. Because the components maps are engine manufacturer’s propriety obtained from very expensive experimental tests, they are not provided to the customers, generally. Therefore, because the engineers, who are working the performance simulation, have been mostly relying on component maps scaled from the similar existing maps, the accuracy of the performance analysis using the scaled maps may be relatively lower than that using the real component maps. Therefore, a component map generation method using experimental data and the genetic algorithms are newly proposed in this study. The engine test unit to be used for map generation has a free power turbine type small turboshaft engine. In order to generate the performance map for components of this engine, after obtaining engine performance data through many experimental tests, and then the third order equations, which have relationships the mass flow function, the pressure ratio and the isentropic efficiency as to the engine rotational speed were derived by using the genetic algorithm. A steady-state performance analysis was performed with the generated maps of the compressor by the commercial gas turbine performance analysis program GASTURB (Kruzke, 2001). In order to verify predominance of the proposed scheme, the performance analysis results using the maps obtained by this study were compared with those using the compressor map provided by the engine manufacturer and the scaled turbine maps obtained from the GASTURB, as well as experimental results. In comparison, it was found that the component maps can be generated from the experimental test data by using the genetic algorithms, and it was confirmed that the analysis results using the generated maps were very similar to those using the scaled maps from the GASTURB.
Optimization of the Managing Strategy of a Cogenerative Power Park in a Liberalized Market
Authors: Silva Paolo , Campanari Stefano , Macchi Ennio , Delfino Stefano
Published: November 2008

The paper addresses the optimization of the managing strategy of a cogenerative power park in a liberalized market characterized by great time variability of the electricity sale price. Besides electric tariffs and marginal costs, a variety of other factors affects the selection of operating mode of the prime movers, such as environmental conditions, O&M costs, range of plant output regulation capability and performance deterioration of the components. The optimum plant operating schedule is found with reference to a tariff scenario where the base-load, mid-term and peak-load electricity costs are set by economical competition among a variety of power stations. The first part of the paper focuses on the case of a single cogenerative combined cycle, generating heat and electricity for an industrial load. The paper then deals with the extension of the optimization strategy to the more complex case of a combination of various prime movers (including combined cycle, combustion turbines and reciprocating gensets), all feeding the same district heating network. The results indicate the utmost importance of a correct management of the power stations for the achievement of best energy ad economic results.
Unsteady Three-Dimensional Flow Phenomena Due to Breakdown of Tip Leakage Vortex in a Transonic Axial Compressor Rotor
Authors: Yamada K. , Furukawa M. , Nakano T. , Inoue M. , Funazaki K.
Published: November 2008

Unsteady three-dimensional flow fields in a transonic axial compressor rotor (NASA Rotor 37) have been investigated by unsteady Reynolds-averaged Navier-Stokes simulations. The simulations show that the breakdown of the tip leakage vortex occurs in the compressor rotor because of the interaction of the vortex with the shock wave. At near-peak efficiency condition small bubble-type breakdown of the tip leakage vortex happens periodically and causes the loading of the adjacent blade to fluctuate periodically near the leading edge. Since the blade loading near the leading edge is closely linked to the swirl intensity of the tip leakage vortex, the periodic fluctuation of the blade loading leads to the periodic breakdown of the tip leakage vortex, resulting in self-sustained flow oscillation in the tip leakage flow field. However, the tip leakage vortex breakdown is so weak and small that it is not observed in the time-averaged flow field at near-peak efficiency condition. On the other hand, spiral-type breakdown of the tip leakage vortex is caused by the interaction between the vortex and the shock wave at near-stall operating condition. The vortex breakdown is found continuously since the swirl intensity of tip leakage vortex keeps strong at near-stall condition. The spiral-type vortex breakdown has the nature of self-sustained flow oscillation and gives rise to the large fluctuation of the tip leakage flow field, in terms of shock wave location, blockage near the rotor tip and three-dimensional separation structure on the suction surface. It is found that the breakdown of the tip leakage vortex leads to the unsteady flow phenomena near the rotor tip, accompanying large blockage effect in the transonic compressor rotor at the near-stall condition.
FRAME: A Tool for Predicting Gas Turbine Condition as Well as Reliability, Availability Performance
Authors: Veer Timot , Ulvestad Andreas , Bolland Olav
Published: November 2008

A complex software tool (FRAME) for assessing lifing parameters as well as reliability and availability performance of gas turbines is presented in this paper. The herein described tool is developed by the authors, whereas the implemented know-how originates from field experience gained by condition and health monitoring of gas turbines operating offshore in oil industry. The authors focus on structure, functionality as well as possible benefits of its use. In the second part of the work results of several simulation runs and parameter variations are presented. Although the primary goal is to test the utility and functionality of the presented tool, interesting and relevant results are obtained. Due to space limitations we restrict ourselves to discuss washing/time interdependence when presenting the findings herein.
Validation of Flame Transfer Function Reconstruction for Perfectly Premixed Swirl Flames
Authors: Gentemann A. , Hirsch C. , Kunze K. , Kiesewetter F. , Sattelmayer T. , Polifke W.
Published: November 2008

The introduction of lean premix combustion increases the susceptibility of the combustor to thermoacoustic instabilities. To control these instabilities, information about the dynamic behavior of the combustion process is necessary. The flame transfer function offers one possibility to describe the dynamic behavior of the combustion process. It relates velocity fluctuations through the burner to an overall heat release fluctuation caused by the flame. As the transfer function for turbulent premix swirl flames can not be derived accurately from first principles, an alternative approach is needed. This paper introduces and validates a method, based on computational fluid dynamics (CFD), to reconstruct flame transfer functions. A transient simulation of the turbulent reacting flow is performed with broad band excitation of the flow variables on the boundaries. On the basis of the resulting time series for velocity and heat release, the transfer function of the flame is reconstructed by application of a system identification procedure based on the Wiener-Hopf equation. This method is applied to a lean perfectly premixed swirl burner. The resulting transfer function is validated with experimental data up to frequencies of f = 400 Hz. Good qualitative agreement is observed between the two approaches. Remarkably, the absolute value of the flame transfer function (the ‘gain’ of the flame) is found to be larger than unity over a range of frequencies, even though fluctuations of heat release and velocity are normalized with their mean flow values. To gain insight into this phenomenon, the dynamic behavior of the flame is investigated in detail. This concerns in particular the interaction of velocity, heat release fluctuations, the swirl number, and fluctuations of flame position and shape. Instead of broad band excitation, single frequency excitation is applied on the boundary for these investigations. It is found that swirl number fluctuations are convected into the flame. At the frequency where the wavelength of those fluctuations agrees with the length scale of the flame, unburned gases accumulate in the combustor. The excess heat is released periodically, which causes the overshoot in the absolute value of the flame transfer function.
Investigation of a High Lift LP Turbine Blade Submitted to Passing Wakes: Part 2 — Boundary Layer Transition
Authors: Coton Thomas , Arts Tony
Published: November 2008

A new test case for very high lift LP turbines has been investigated. The interaction with incoming wakes has been experimentally assessed at two Reynolds number values (13 and 30 × 104) and two inlet turbulence levels (0.8 and 3.5%) for an exit Mach number equal to 0.7. The blade performance was discussed in part 1 of the paper. Part 2 investigates the boundary layer transition and its interaction with the incoming wakes. The intermittency factor was computed from fast response wall heat transfer signals. In presence of passing wakes, the modeling was particularly improved by considering the effect of the velocity gradient on the wake impact. The space-time diagrams revealed complex multiple interaction zones. The calming phenomenon appeared weak compared to the influence of the wake negative jet and the re-establishment process of the separation region.
Measurements of Secondary Flows Downstream of a Turbine Cascade at Off-Design Incidence
Authors: Benner M. W. , Sjolander S. A. , Moustapha S. H.
Published: November 2008

This paper presents experimental results of the secondary flows from two large-scale, low-speed, linear turbine cascades for which the incidence was varied. The aerofoils for the two cascades were designed for the same inlet and outlet conditions and differed mainly in their leading-edge geometries. Detailed flow field measurements were made upstream and downstream of the cascades and static pressure distributions were measured on the blade surfaces for three different values of incidence: 0, +10 and +20 degrees. The results from this experiment indicate that the strength of the passage vortex does not continue to increase with incidence, as would be expected from inviscid flow theory. The streamwise acceleration within the aerofoil passage seems to play an important role in influencing the strength of the vortex. The most recent off-design secondary loss correlation (Moustapha et al. [1]) includes leading-edge diameter as an influential correlating parameter. The correlation predicts that the secondary losses for the aerofoil with the larger leading-edge diameter are lower at off-design incidence; however, the opposite is observed experimentally. The loss results at high positive incidence have also high-lighted some serious shortcomings with the conventional method of loss decomposition. An empirical prediction method for secondary losses has been developed and will be presented in a subsequent paper.
Design of Small Centrifugal Compressors Performance Test Facility
Authors: Al-Sulaiman Fahad A. , Al-Qutub Amro M.
Published: November 2008

Actual performance testing is a key element in the design stage, development and troubleshooting of centrifugal compressors. The present work discusses the procedure for designing the experimental setup and the selection of drive unit for variable centrifugal compressors sizes. It starts with setting criteria of selection. A survey over different types of drive units and facility setup was conducted. It was found that the electric drive unit with the aid of transmission for stepping-up the speeds is the most suitable type. This is due mainly to the excellent control property of electric motors allowing for wide range of operational speed and power. A new methodology was developed for selecting operational power and speeds of the drive unit for different sizes of impellers. The code, used for the analysis, was developed by the authors. It calculates the range of input power, input torque, and rotational speeds, as well as, the mass flow rate, total pressure and temperature ratios for different sizes of impellers. This will aid in selecting the proper instrumentation for the experiments. The code used for design methodology is based on one dimensional through flow formulation and validated with experimental results in the literature. It is expected that the present methodology will enhance selection procedure for designing compressor test facility.
Numerical Simulation of the Unsteady Flow Field in an Axial Gas Turbine Rim Seal Configuration
Authors: Jakoby Ralf , Zierer Thomas , Lindblad Klas , Larsson Jonas , deVito Laurent , Bohn Dieter E. , Funcke Joachim , Decker Achim
Published: November 2008

The fluid flow in gas turbine rim seals and the sealing effectiveness are influenced by the interaction of the rotor and the stator disk and by the external flow in the hot gas annulus. The resulting flow structure is fully 3-dimensional and time-dependant. The requirements to a sufficiently accurate numerical prediction for front and back cavity flows are discussed in this paper. The results of different numerical approaches are presented for an axial seal configuration. This covers a full simulation of the time-dependant flow field in a 1.5 stage experimental turbine including the main annulus and both rim cavities. This configuration is simplified in subsequent steps in order to identify a method providing the best compromise between a sufficient level of accuracy and the least computational effort. A comparison of the computed cavity pressures and the sealing effectiveness with rig test data shows the suitability of each numerical method. The numerical resolution of a large scale rotating structure that is found in the front cavity is a special focus of this study. The existence of this flow pattern was detected first by unsteady pressure measurements in test rig. It persists within a certain range of cooling air massflows and significantly affects the sealing behaviour and the cavity pressure distribution. This phenomenon is captured with an unsteady calculation using a 360 deg. computational domain. The description of the flow pattern is given together with a comparison to the measurements.
Infrared Thermography With In-Situ Calibration Using Thermochromic Liquid Crystals Applied to Film Cooling
Authors: Brauckmann Dennis , von Wolfersdorf Jens
Published: November 2008

This paper presents an application of infrared thermography measurements on a film cooled flat surface using a single cylindrical film cooling hole. Infrared thermography (IR) is used to obtain the full field surface distribution of the temperature and therefore the film cooling effectiveness. For accurate results in-situ calibration of the infrared radiation intensity during the experiment needs to be performed, which is usually done using surface mounted thermocouples. For the near hole region thermochromic liquid crystals (TLC) are applied to obtain additional information for the calibration. A mixture of two narrow band TLCs is used, leading to discrete temperature lines on the surface. Using small variations in the test temperature settings, the TLC-lines can be located on the test surface into the regions of interest and the influence on the obtained infrared calibration results can be investigated. Experimental results for the film cooling effectiveness are presented for several blowing rates.
A Method of the Dynamic Analysis of Pipeline Systems Considering the Effects of Casing
Authors: Li Lin , Sheng Jun
Published: November 2008

The paper deals with a new method called ‘mixed interface direct component modal synthesis’ to determine the modal parameters of a large and complex structure, such as outer casing-pipeline systems of aero-engine. In this method, the whole structure is divided into several parts. The interface of the main substructure (large and complex component) is considered as a free-interface, and that of the other branch substructures are considered as fixed-interfaces. The computation of each substructure is entirely independent. Especially this method simplifies the optimization of structural design. For case-pipeline systems for example, the changes of the location of the pipe’s support will have no influence on the casing model. Hence reduplicate computation is no longer needed. The analysis of pipeline systems using fixed-interface is just the same as the usual analysis, which clamps all of the interface DOFs on a rigid surface. Two examples, a cantilever beam and a simulative case-pipeline system, are considered. Both of them also are analyzed as whole systems in ANSYS, a widely used FEM software. The numerical results obtained by this method and by ANSYS are compared, and they are identical.
Corrected Parameter Control for Two Shaft Gas Turbines
Authors: Casoni Andrea , Colitto Nuncio , Elliott Joseph , Groppi Stefano , Russo Alessandro
Published: November 2008

In order to make gas turbines insensitive to the wide range of ambient and load conditions where they find application, and to run them always at their optimal capability, a new control logic has been developed. The new logic is called ‘Corrected Parameter Control’ (CPC) as it is able to ‘correct’ itself on the basis of the present working conditions. CPC logic allows the engine controller to properly account for: ambient pressure and temperature, humidity, inlet and exhaust pressure losses and, for mechanical drive engines, power turbine speed. This guarantees: - that the engine truly reaches its operating limit when maximum power output is required (i.e. to run at design firing temperature); - the correct fuel/air ratio in the combustion chamber to achieve the target emissions throughtout the load range and at every ambient condition. Full CPC logic has been applied for the first time on the prototype of the new MS5002E gas turbine (currently on-test); while a simplified version that only accounts for the power turbine speed has already been successfully tested in-field on the GE10-2. In this application, the introduction of the CPC logic increased the maximum power by over 5% at 80% of power turbine design speed.
The Ethanol-Water Humidification Process in EvGT Cycles
Authors: Thern Marcus , Lindquist Torbjo¨rn , Torisson Tord
Published: November 2008

Ethanol from bio-products has become an important fuel for future power production. However, the present production technology is rather expensive. This paper focuses on how to lower the production cost of ethanol extraction from mash, and to use the ethanol as a primary fuel in gas turbines for heat and power production. Today, ethanol is produced during distillation by supplying energy to extract the ethanol from the mash. Using the evaporation process in the evaporative gas turbine to extract the ethanol from the mash before the distillation step, a lot of energy can be saved. In the evaporation process, the ethanol is extracted directly from the mash using energy from low-level energy sources. The evaporation technology is therefore expected to reduce the cost for the ethanol production. Simultaneous heat and mass transfer inside the ethanol humidification tower drives a mixture of ethanol and water into the compressor discharge air. To investigate the evaporation of a binary mixture into air at elevated pressures and temperatures, a test facility was constructed and integrated into the evaporative gas turbine pilot-plant. The concentration of ethanol in the mash is not constant but depends on the sugar content in the feedstock used in the fermentation process. Tests were therefore conducted at different concentrations of ethanol in the ethanol-water mixture. Tests were also performed at different temperature and flow conditions to establish the influence of these parameters on the lower heating value of the produced low calorific gas. It has been shown that this technology extracts about 80% of the ethanol from the mash. It has also been shown that the composition of the resulting gas depends on the temperatures, flow rates and composition of the incoming streams. The tests have shown that the produced gas has a lower heating value between of 1.8 to 3.8 MJ/kg. The produced gas with heating values in the upper range is possible to use as fuel in the gas turbine without any pilot flame. Initial models of the ethanol humidification process have been established and the initial test results have been used for validating developed models.
On a Novel Annular Sector Cascade Technique
Authors: Povey T. , Jones T. V. , Oldfield M. L. G.
Published: November 2008

An advanced technique for establishing pressure boundary conditions in annular sector cascade experiments has been developed. This novel technique represents an improvement over previous methods, and provides the first means by which annular sector boundary conditions that are representative of those which develop in an annular cascade can be established with a high degree of satisfaction. The technique will enable cascade designers to exploit the obvious advantages of annular sector cascade testing: the reduced cost of both facility manufacture and facility operation, and the use of engine parts in place of two-dimensional counterparts. By employing an annular sector of deswirl vanes downstream of the annular sector of test vanes, the radial pressure gradient established in the swirling flow downstream of the test vanes is not disturbed. The deswirl vane exit-flow — which has zero swirl velocity — can be exhausted without unsteadiness, and without the risk of separation, into a plenum at constant pressure. The pressure ratio across the annular sector of test vanes can be tuned by adjusting the throat area at the deswirl vane exit plane. Flow conditioning systems which utilise the Oxford deswirl vane technology have previouly been used to set pressure boundary conditions downstream of fully annular cascades in both model and engine-scale (the Isentropic Light Piston Facility at Farnborough) experimental research facilities (Povey et al. [1, 2]). The deswirl vane is particularly suited to the control of highly whirling transonic flows. It has been demonstrated by direct comparison of aerodynamic measurements from fully annualr and annular sector experiments that the use of a deswirl vane sector for flow conditioning at the exit of an annular sector cascade represents an attractive novel solution to the boundary condition problem. The annular sector technique is now described.
Numerical Simulation of the Low Plasticity Burnishing Process for Fatigue Property Enhancement
Authors: Beres W. , Li J. , Patnaik P. C.
Published: November 2008

Low Plasticity Burnishing (LPB) process introduces a deep layer of high-compression material through an application of a smooth, free-rolling ball moving in a single pass parallel to the material surface. This paper describes modelling the LPB process numerically using two- and three-dimensional finite element method, and reports the results of parametric studies. The residual stress distributions, as well as the total and inplane plastic strains obtained from the numerical calculations, are compared to the published results of residual stress measurements. In addition, the preliminary results of the finite element modelling of residual stress relaxations caused by the elevated temperatures are also reported.
Propagation and Decay of Shock Waves in Turbofan Engine Inlets
Authors: Prasad Dilip , Feng Jinzhang
Published: November 2008

Numerical experiments are carried out to investigate the tone noise radiates from a turbofan engine inlet under conditions at which the relative flow past the rotor tip is supersonic. Under these conditions, the inlet tone noise is generated by the upstream-propagating rotor-locked shock wave field. The spatial evolution of this shock system is studied numerically for flows through two basic hard-walled configurations: a slender nacelle with large throat area and a thick nacelle with reduced throat area. With the flight Mach number set to 0.25, the spatial evolution of the acoustic power through the two inlets reveals that the reduced throat area inlet provides superior attenuation. This is attributed to the greater mean flow acceleration through its throat and is qualitatively in accord with one-dimensional theory, which shows that shock dissipation is enhanced at high Mach numbers. The insertion of a uniform extension upstream of the fan is shown to yield greater attenuation for the inlet with large throat area, while the acoustic performance of the reduced throat area inlet is degraded. This occurs because the interaction of the nacelle and spinner potential fields is weakened, resulting in a lower throat Mach number. The effect of forward flight on the acoustic power radiated from the two inlets is also investigated by examining a simulated static condition. It is shown that the slender nacelle radiated significantly less power at the static condition than in flight, whereas the power levels at the two conditions are comparable for the thick nacelle. The reason for this behavior is revealed to be a drastic overspeed near the leading edge of the slender nacelle, which occurs to a lesser degree in the case of the thick inlet. This has implications for ground acoustic testing of aircraft engines, which are discussed.
Towards Modeling Lean Blow Out in Gas Turbine Flameholder Applications
Authors: Kim Won-Wook , Lienau Jeffrey J. , Van Slooten Paul R. , Colket Meredith B. , Malecki Robert E. , Syed Saadat
Published: November 2008

The objective of this study was to assess the accuracy of the Large-Eddy Simulation (LES) methodology, with a simple combustion closure based on equilibrium chemistry, for simulating turbulent reacting flows behind a bluff body flameholder. Specifically, the variation in recirculation zone length with change in equivalence ratio was calculated and compared to experimental measurements. It was found that the present LES modeling approach can reproduce this variation accurately. However, it understated the recirculation zone length at the stoichiometric condition. The approach was assessed at the lean blow out (LBO) condition to evaluate its behavior at the lean limit and to analyze the physics of combustion instability.
Ceramic Matrix Composite Vane Subelement Testing in a Gas Turbine Environment
Authors: Verrilli Michael , Calomino Anthony , Robinson R. Craig , Thomas David J.
Published: November 2008

Vane subelements were fabricated from a silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composite and were coated with an environmental barrier coating (EBC). A test configuration for the vanes in a gas turbine environment was designed and fabricated. Prior to testing, finite element analyses were performed to predict the temperatures and stress conditions present in vane during rig testing. This paper discusses the test configuration, the finite element analysis predictions, and results of the vane testing.
Comparison of Turbine Tip Leakage Flow for Flat Tip and Squealer Tip Geometries at High-Speed Conditions
Authors: Key Nicole L. , Arts Tony
Published: November 2008

The tip leakage flow characteristics for flat and squealer turbine tip geometries are studied in the von Karman Institute Isentropic Light Piston Compression Tube facility, CT-2, at different Reynolds and Mach number conditions for a fixed value of the tip gap in a non-rotating, linear cascade arrangement. To the best knowledge of the authors, these are among the very few high-speed tip flow data for the flat tip and squealer tip geometries. Oil flow visualizations and static pressure measurements on the blade tip, blade surface, and on the corresponding endwall provide insight to the structure of the two different tip flows. Aerodynamic losses are measured for the different tip arrangements, also. The squealer tip provides a significant decrease in velocity through the tip gap with respect to the flat tip blade. For the flat tip, an increase in Reynolds number causes an increase in tip velocity levels, but the squealer tip is relatively insensitive to change in Reynolds number.
Latticework (Vortex) Cooling Effectiveness: Part 2 — Rotating Channel Experiments
Authors: Acharya S. , Zhou Fuguo , Lagrone Jonathan , Mahmood Gazi , Bunker Ronald S.
Published: November 2008

The heat transfer and pressure drop characteristics of latticework coolant blade passages have been investigated experimentally under conditions of rotation. Stationary studies with the latticework configuration have shown potential advantages including spatially-uniform streamwise distributions of the heat transfer coefficient, greater blade strength, and enhancement levels comparable to conventional rib turbulators. In the present study, a latticework coolant passage, with orthogonal-ribs, is studied in a rotating heat transfer test-rig for a range of Reynolds numbers (Res), Rotation numbers (Ros), and density ratios. Measurements indicate that for Res≥20,000, the latticework coolant passage provides very uniform streamwise distributions of the Nusselt number (Nus) with enhancement levels (relative to smooth-channel values) in the range of 2.0 to 2.5. No significant dependence of Nus on Ros and density ratio is observed except at lower Res values (≤10,000). Nusselt numbers are highest immediately downstream of a turn indicating that bend-effects play a major role in enhancing heat transfer. Friction factors are relatively insensitive to Ros, and thermal performance factors at higher Res values appear to be comparable to those obtained with conventional rib-turbulators. The present study indicates that latticework cooling geometry can provide comparable heat transfer enhancements and thermal performance factors as conventional rib-turbulators, with potential benefits of streamwise uniformity in the heat transfer coefficients and added blade strength.
Reduced Models for Rotating Component Lifing
Authors: Parthasarathy Girija , Allumallu Satyavaraprasad
Published: November 2008

The most common failure mode for engine rotating components is material fatigue. Low Cycle Fatigue or LCF is caused by stresses and temperatures resulting from start-stop cycles. One current common practice is to assign an LCF life of certain number of start-stop cycles based on a standard flight or mission. This is done during design through detailed calculations of stresses and temperatures for a standard flight, and the use of material property and failure models. The limitation of the design phase stress and temperature calculations is that they cannot take into account actual operating temperatures and stresses. In order to improve significantly the accuracy of the LCF lifing prediction, the component temperatures and stresses need to be computed for the actual operating conditions. However, stress and thermal models are very detailed and complex, and it could take on the order of a few hours to complete a stress and temperature simulation for a flight. The objective of this work is to develop reduced models, that would enable us to compute the stresses and temperatures at critical locations, without the detailed computationally intensive models. This paper describes the development of the reduced model and the results achieved in comparison with the original models for components of Honeywell propulsion engines. Given certain inputs such as engine speed and ambient temperature for the duration of the flight, the reduced models computes the component critical location temperature and thermal stress for the same flight in a very small fraction of time it would take the original finite element model to compute.
The Effect of an Upstream Turbine on a Low-Aspect Ratio Vane
Authors: Miller R. J. , Moss R. W. , Ainsworth R. W. , Harvey N. W.
Published: November 2008

The interaction between a high-pressure rotor and a downstream vane is dominated by vortex-blade interaction. Each rotor blade passing period two co-rotating vortex pairs, the tip-leakage and upper passage vortex and the lower passage and trailing shed vortex, impinge on, and are cut by, the vane leading edge. In addition to the streamwise vortex the tipleakage flow also contains a large velocity deficit. This causes the interaction of the tip-leakage flow with a downstream vane to differ from typical vortex blade interaction. This paper investigates the effect these interaction mechanisms have on a downstream vane. The test geometry considered was a low aspect ratio second stage vane located within a S-shaped diffuser with large radius change mounted downstream of a shroudless high-pressure turbine stage. Experimental measurements were conducted at engine-representative Mach and Reynolds numbers, and data was acquired using a fastresponse aerodynamic probe upstream and downstream of the vane. Time-resolved numerical simulations were undertaken with and without a rotor tip gap in order to investigate the relative magnitude of the interaction mechanisms. The presence of the upstream stage is shown to significantly change the structure of the secondary flow in the vane and to cause a small drop in its performance.
The Effects of the Vane and Mainstream Turbulence Level on Hot Streak Attenuation
Authors: Jenkins Sean C. , Bogard David G.
Published: November 2008

This paper discusses the effects of varying pitch position on the attenuation of a simulated hot streak in a vane cascade under conditions of low and high turbulence. Measurements describe the effect of both small and large changes in pitch away from the stagnation line as evidenced by hot streak variations in the wake and at the trailing edge. Under both turbulence conditions, the vane serves to increase or decrease the attenuation rate depending on the location of the hot streak relative to the vane due to isolating of the hot streak core by the vane wall. Additional attenuation resulted due to the action of the wake on the hot streak.
Web-Based, Interactive Laboratory Experiment in Turbomachine Aerodynamics
Authors: Navarathna Nalin , Fedulov Vitalij , Martin Andrew , Fransson Torsten
Published: November 2008

Remote laboratory exercises are gaining popularity due to advances in communication technologies along with the need to provide realistic yet flexible educational tools for tomorrow’s engineers. Laboratory exercises in turbomachinery aerodynamics generally involve substantial equipment in both size and power, so the development of remotely controlled facilities has perhaps not occurred as quickly as in other fields. This paper presents an overview of a new interactive laboratory exercise involving aerodynamics in a linear cascade of stator blades. The laboratory facility consists of a high-speed fan that delivers a maximum of 2.5 kg/s of air to the cascade. Traversing pneumatic probes are used to determine pressure profiles at upstream and downstream locations, and loss coefficients are later computed. Newly added equipment includes cameras, stepper motors, and a data acquisition and control system for remote operation. This paper presents the laboratory facility in more detail and includes discussions related to user interface issues, the development of a virtual laboratory exercise as a complement to experiments, and comparative evaluation of Virtual, Remote and Local laboratory exercises.
An Experimental Investigation of a Newly Designed Combustor for LCV Gas With Low NOx Emissions From Fuel Bound Nitrogen
Authors: Adouane Belkacem , Witteveen Guus , de Jong Weibren , van Buijtenen Jos P.
Published: November 2008

Biomass derived LCV gas represents one of the best alternatives for fossil fuels. It is very attractive, because of its neutral aspects concerning CO2 emissions. However, on the other hand, the high content of fuel bound nitrogen results in high NOx emissions. This is one of the major problems related to the application of biomass derived LCV gas in gas turbines or gas engines. Reducing the conversion of fuel bound nitrogen (FBN) to NOx has been one of the main preoccupations for researchers working in the field of LCV gas combustion. At the section Energy Technology of Delft University of Technology, a group of researchers is busy with optimizing a newly designed combustor for LCV gas and low NOx emissions. With the new design, it is expected to end up with a very low conversion of FBN to NOx by optimizing the design and combustion process. The newly designed combustor is investigated experimentally and by CFD modeling. In this paper, the experimental part is presented. In all the experiments described below, natural gas diluted with nitrogen was the simulated LCV gas and ammonia (NH3) is injected into the fuel gas to simulate the FBN. The fuel gas has an HCV (High Calorific Value) of 5MJ/mn3. The combustor shows a very important optimal regime, where a minimum in conversion of FBN to NOx is achieved while maintaining a very low CO emissions. As low as 8% conversion ratio of NH3 to NOx has been achieved at high NH3 concentration in the LCV gas (3.45vol.%), and a minimum of 30% conversion was achieved for low ammonia concentrations (3100 ppmv).
Design of a Gas Turbine Based Air Start Unit for Larger Aircraft Engine
Authors: Hsu Li-Chieh , Ho Wu-Chi , Hsueh Chien-Ching
Published: November 2008

A novel Air Start Unit powered by gas turbine engine is developed. The feature of this unit is that it can start various aircraft engines, including the hundred thousand pound thrust class engine like GE90, with different air flow rate in a compact design. This paper introduces the complete design and development of large centrifugal compressor, digital engine control system, testing of gas turbine system.
Development of Coal Partial Gasification and Combustion System
Authors: Liu Yaoxin , Yang Libin , Fang Mengxiang , Chen Guanyi , Luo Zhongyang , Cen Kefa
Published: November 2008

A new system using combined coal gasification and combustion has been developed for clean and high efficient utilization of coal. Following are the processes. The coal is first partially gasified and the produced fuel gas is then used for industrial purpose or as a fuel for a gas turbine. The char residue from the gasifier is burned in a circulating fluidized bed combustor to generate steam for power generation. For having the experimental investigation, a 1MW pilot plant test facility has been erected. Experiments on coal partial gasification with air, and recycle gas have been made on the 1 MW pilot plant test facility. The results show that, with air as gasification agent, the system can produce 4–5MJ/Nm3 low heating value dry gas and fuel conversion efficiency attains 50–70% in the gasifier, and residue 20–40% converted in the combustor and total conversion efficiency in the system is over 90%. In the gasifier, the carbon conversion efficiency increases with the bed temperature and the air blown temperature. CaCO3 has an effective effect for sulfur removal in the gasifier. The sulfur removal efficiency attains 85% with Ca/S molar ratio 2.5. The system can produce 12–14MJ/Nm3 middle heating value day gas by using high temperature circulation solid as heat carrier and recycle gas or steam as gasification media, but the fuel conversion efficiency only attain 30–40% in the gasifier and most of fuel energy is converted in the combustor. CaCO3 has an obvious effect on tar cracking and H2S removal. The sulfur removal efficiency attains 80% with Ca/S molar ratio 2.5.
Combustion Tuning Guidelines: Understanding and Mitigating Dynamic Instabilities in Modern Gas Turbine Combustors
Authors: Angello Leonard C. , Castaldini Carlo
Published: November 2008

DLN combustors used in modern utility Combustion Turbines (CTs) must operate within tight tolerances of equivalence ratio, fuel/air mixing and turbulence in order to deliver single digit NOx emission performance, while maintaining combustion stability and design power output. As lean NOx emissions from large CTs are driven to increasingly lower levels, even small changes in combustion conditions or manufacturing tolerances can lead to the onset of combustion instabilities and acoustic combustion noise. If left unattended, dynamic oscillations in ultra-low NOx premix combustors can produce resonant acoustics that can in turn cause adverse impacts on performance, including the ability to deliver capacity, or the premature failure of critical system components and emergency shut-downs. For example, it is widely accepted that extreme changes in ambient temperature, or minor changes in fuel composition and temperature, or the use of power augmentation techniques under certain conditions, can lead to combustion instabilities. EPRI is leading a multi-task program to map the operating regime for stable combustion in modern DLN combustors; identify key operating conditions that most influence the onset of combustion instabilities; and develop DLN tuning guidelines based on users’ experience and vendors’ monitoring and control systems. The overall objective of these projects is to maximize the operational flexibility of modern CTs based on implementation of active monitoring and control guidelines aimed at anticipating, preventing, and effectively responding to the onset of combustion-induced dynamic instabilities and CT noise. This paper briefly discusses the dynamics of combustion instabilities in premix DLN combustors; presents the preliminary results from detailed parametric analysis of a large database; and our findings on DLN tuning approaches such as modulating fuel flows and changing inlet guide vanes, that can be used effectively to control combustion instabilities.
Development and Evaluation of Environmental Barrier Coatings for Si-Based Ceramics
Authors: Bhatia Tania , Vedula Venkat , Eaton Harry , Sun Ellen , Holowczak John , Linsey Gary
Published: November 2008

Environmental barrier coatings (EBCs) are being developed for silicon carbide (SiC) based composites and monolithic silicon nitride (Si3N4) to protect against the accelerated oxidation and subsequent silica volatilization in high temperature, high-pressure steam environments encountered in gas turbine engines. While EBCs for silicon carbide (EBCSiC) have been demonstrated in combustor liner applications, efforts are ongoing in the development of EBC systems for silicon nitride (EBCSiN). The challenges of adapting EBCSiC to monolithic Si3N4 are discussed in this paper. Progress in the area of EBCSiN including development and performance during field tests and tests simulating engine conditions are reviewed.
Coupled Lateral and Torsional Vibrations of a Cracked Rotor
Authors: Sawicki Jerzy T. , Baaklini George Y. , Gyekenyesi Andrew L.
Published: November 2008

Rotor crack problems present a significant safety and loss hazard in nearly every application of modern turbomachinery, particularly in the power generation industry. However, early crack detection is not easily achieved during the operation of machinery. The difficulty is based on the fact that a crack produces an undetectable change in the overall structural response. This paper analyzes the coupling of torsional and lateral vibrations for an unbalanced cracked rotor. The rotor equations of motion for a system with cracked shaft, obtained using Lagrangian dynamics, show coupling and nonlinear interaction between the torsional and lateral vibrations. To investigate the effect of a transverse surface crack on the dynamic rotor response the breathing crack model was employed. By applying an external torsional excitation together with the excitation due to unbalance, signature responses were observed in the rotor vibration spectrum at sum and difference frequencies. These signature responses were due to the nonlinear effect of the crack. The observed phenomena, analytically defined here, offers a new methodology concerning crack detection and prognosis in rotors.
Thermodynamic Evaluation of Humidified Air Turbine (HAT) Cycles
Authors: Yadav R. , Dwivedi Pawan Krishan , Kumar Pradeep , Saraswati Samir
Published: November 2008

The present work deals with the parametric energy analysis of humidified air turbine (HAT) cycles, identifying the best plant arrangement and predicting the influence of operating parameters on plant performance. In predicting performance plant optimization is to be achieved for an overall pressure ratio. The results presented will be helpful to designers to select the best configurations and optimum operating parameters. The best configuration among the chosen configurations is the one in which there are three intercoolers and two aftercoolers.
Staged Catalytic Combustion Method for the Advanced Zero Emissions Gas Turbine Power Plant
Authors: Griffin Timothy , Winkler Dieter , Wolf Markus , Appel Christoph , Mantzaras John
Published: November 2008

The AZEP (Advanced Zero Emissions Power Plant) project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce CO2 emissions. Preliminary calculations indicate the attractiveness of this concept in comparison to conventional tail-end CO2 capture. Key to achieving the AZEP project targets is the development of a combustion system to burn natural gas with nearly stoichiometric amounts of oxygen and high levels of exhaust gas dilution. Within the first part of this study the fundamental combustion properties of AZEP gas mixtures are quantitatively determined. Significant inhibition results from the high level of exhaust gas dilution. In the second part a staged, rich–lean combustion concept, proposed to improve combustion stability, is investigated. It was shown that significant levels of hydrogen could be produced by a first stage, partial catalytic oxidation (PCO) of methane. Furthermore, it is shown that the addition of this produced hydrogen improves the stability of the downstream, second stage burnout zone. It was demonstrated that the produced syngas could act to reduce the blowout limit by ca. 100 K as compared to homogeneous gas phase combustion.