bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Model Based Control of Aircraft Propulsion Systems: Status and Outlook for Naval Aviation Applications
Authors: Fuller James W. , Kumar Aditya , Millar Richard C.
Published: September 2008

The control of military aircraft propulsion and associated aircraft systems continue to become more demanding, in response to the operational needs of new and existing aircraft and missions. High performance aircraft operate in multiple modes. They are complex and require complex propulsion systems that provide precise and repeatable performance: safely, dependably, and cost effectively. To support these requirements, propulsion control systems must manage multiple effectors based on multiple operating parameters through interactive processes. The scopes of control extends beyond the gas turbine engine to the inlet, exhaust, power and bleed extraction, electrical power systems, thermal & environmental management, fuel systems, starting, accessories, and often propellers, rotors or lift fans. Modern propulsion control systems are increasingly integrated with the aircraft flight controls and the distinction is becoming less & less meaningful. Within the gas turbine, variable geometry and active control of turbo-machinery and auxiliary systems proliferate to relax mechanical design constraints and enable designs with increased thrust to weight ratios, reduced fuel burn and increased durability. Digital controls provide crisp and repeatable responses and improve aircraft reliability and availability, but further enhancements are needed as military aircraft become more capable and versatile (e.g., V-22 and F35). The control system must be aware and appropriately respond to component degradation and damage, optimally managing conflicting constraints and goals. Modern propulsion systems are becoming more profoundly multivariable and include multiple effectors to meet multiple goals. They are multivariable because they are cross-coupled, where each effector can affect multiple goals. In addition, these multiple goals, (e.g., performance, life, operating margin) may be conflicting and need to be traded off, and the best trade off will vary with mission. With predictable and rapid increases in computational capability in Full Authority Digital Electronic Controls, the industry is moving forward to address these needs through model based control, control that manages propulsion and aircraft systems with optimal control responses derived from detailed real time models of component behavior. Since the component characteristics change significantly during a service interval, and yet longer time on wing is necessary, these control systems must sense degradation and damage to multiple components and adapt to it. This paper describes current approaches and NAVAIR plans to develop, mature and deploy this technology, while touching on other potential applications.
Turbine Off-Line Water Wash Optimization Approach for Power Generation
Authors: Basendwah Ahmed A. , Pilidis P. , Li Y. G.
Published: September 2008

Utility Gas turbine users are keen to use crude and heavy fuel oil as their prime operating fuels if they meet environmental regulations and are economically feasible. Fouling, or ash deposition, is one of the associated technical problems with burning such fuels. This paper intended to present new off-line water washing optimization approach for simple cycle gas turbines. In this approach, increased costs due to power loss and increased fuel consumption due to turbine fouling are analyzed. Gains and losses resulting from shutdown due to turbine washing and the cost of cleaning materials are estimated. These losses are compared with that of a clean engine to find the optimal turbine off-line water washing interval. A model gas turbine similar to the GE MS7001 EA has been built for the current study. Turbine fouling simulation and fouling detection have been determined by Cranfield University TURBOMATCH/PYTHIA software. The optimum washing interval for the datum engine is found to be once every fifteen continuous operating days. The effect of changing the washing frequency is shown on financial terms.
Automatic Optimisation of Pre-Swirl Nozzle Design
Authors: Ciampoli Fabio , Chew John W. , Shahpar Shahrokh , Willocq Elisabeth
Published: September 2008

The objective of the research described here is to develop and demonstrate use of automatic design methods for pre-swirl nozzles. Performance of pre-swirled cooling air delivery systems depends critically on the design of these nozzles which is subject to manufacturing and stress constraints. The best solution may be a compromise between cost and performance. Here it is shown that automatic optimisation using computational fluid dynamics (CFD) to evaluate nozzle performance can be useful in design. A parametric geometric model of a nozzle with appropriate constraints is first defined and the CFD meshing and solution are then automated. The mesh generation is found to be the most delicate task in the whole process. Direct hill climbing (DHC) and response surface model (RSM) optimisation methods have been evaluated. For the test case considered, significant nozzle performance improvements were obtained using both methods, but the RSM model was preferred.
LES and RANS Investigations Into Buoyancy-Affected Convection in a Rotating Cavity With a Central Axial Throughflow
Authors: Sun Zixiang , Lindblad Klas , Chew John W. , Young Colin
Published: September 2008

The buoyancy-affected flow in rotating disc cavities, such as occurs in compressor disc stacks, is known to be complex and difficult to predict. In the present work large eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS) solutions are compared with other workers’ measurements from an engine representative test rig. The Smagorinsky-Lilly model was employed in the LES simulations, and the RNG k-ε turbulence model was used in the RANS modelling. Three test cases were investigated in a range of Grashof number Gr = 1.87 to 7.41×108 and buoyancy number Bo = 1.65 to 11.5. Consistent with experimental observation, strong unsteadiness was clearly observed in the results of both models, however the LES results exhibited a finer flow structure than the RANS solution. The LES model also achieved significantly better agreement with velocity and heat transfer measurements than the RANS model. Also, temperature contours obtained from the LES results have a finer structure than the tangential velocity contours. Based on the results obtained in this work, further application of LES to flows of industrial complexity is recommended.
Assessment of the Impact of Laminar-Turbulent Transition on the Accuracy of Heat Transfer Coefficient Prediction in High Pressure Turbines
Authors: Mansour Mahmoud L. , Molla Hosseini Khosro , Liu Jong S. , Goswami Shraman
Published: September 2008

This paper presents a thorough assessment for two of the contemporary CFD programs available for modeling and predicting nonfilm-cooled surface heat transfer distributions on turbine airfoil surfaces. The CFD programs are capable of predicting laminar-turbulent transition and have been evaluated and validated against five test cases with experimental data. The suite of test cases considered for this study consists of two flat plat cases at zero and non-zero pressure gradient and three linear-turbine-cascade test cases that are representative of modern high pressure turbine designs. The flat plate test cases are the ERCOFTAC T3A and T3C2, while the linear turbine cascade cases are the MARKII, the Virginia Polytechnic Institute (VPI), and the Von Karman Institute (VKI) turbine cascades. The numerical tools assessed in this study are 3D viscous Reynolds Averaged-Navier-Stokes (RANS) equations programs that employ a variety of one-equation and two-equation models for turbulence closure. The assessment study focuses on the one-equation Spalart and Allmaras and the two-equation shear stress transport K-ω turbulence models with the ability of modeling and predicting laminar-turbulent transition. The RANS 3D viscous codes are Numeca’s Fine Turbo and ANSYS-CFX’ CFX5. Numerical results for skin friction, surface temperature distribution and heat transfer coefficient from the CFD programs are compared to measured experimental data. Sensitivity of the predictions to free stream turbulence and to inlet turbulence boundary conditions is also presented. The results of the study clearly illustrate the superiority of using the laminar-turbulent transition prediction in improving the accuracy of predicting the heat transfer coefficient on the surfaces of high pressure turbine airfoils.
Numerical Insight Into Flow and Thermal Patterns Within an Inlet Profile Generator Comparing to Experimental Results
Authors: Kunze V. R. , Wolff M. , Barringer M. D. , Thole K. A. , Polanka M. D.
Published: September 2008

Historically the design of gas turbine engines have not considered the interaction between the combustor and turbine stages. High pressure turbine vane stages have been designed assuming inlet conditions consistent with a standard turbulent boundary layer profile. However, combustor exit flow entering the vane is known to be highly non-uniform in both the primary and secondary flow regimes. In order to develop higher performance, more efficient, longer life stages, turbine design must take into account combustor exit non-uniformities. The Turbine Research Facility (TRF) at Wright-Patterson Air Force Base has installed a non-reactive full scale annular combustor simulator or more accurately a turbine inlet profile generator to study combustor-vane interaction. Several benchmark tests have been performed on the profile generator consisting of a Taguchi type matrix wherein nine independent variables were adjusted. Supplementing the experimental research at the TRF, a steady state, unstructured, fully three-dimensional CFD analysis was performed. This paper will make comparisons between the CFD and experimental profiles generated by the simulator. Furthermore, the computational study will help to give an understanding of the aerodynamic and aerothermal environment within the generator that experimental instrumentation alone cannot.
Catalytic Detection of Fuel Leaks in Gas Turbine Units: 2 — Gas Fuels Containing Hydrogen, Carbon Monoxide and Inert
Authors: Molie`re Michel , Cozzarin Philippe , Bouchet Se´bastien , Rech Philippe
Published: September 2008

The detection of explosive gas and vapors is a critical safety function in Gas Turbines (GT) units. On one hand, this subject is being revisited by the GT community and safety organizations with a main focus on conventional gas fired power units. On the other hand one sees currently an increasing use of alternative primary energies for GT units including both gaseous and liquid fuels such as LPG, naphtha, syngas and a wide series of low and medium BTU gas fuels. This has prompted GE Energy to undertake a comprehensive evaluation of commercial catalytic detectors that are of common use in the detection of gas leaks. In particular, the multiple announcements of coal-based project (IGCC) represented a strong motivation to launch this program that ambitioned to cover both hydrocarbon and non-hydrocarbon fuels, i.e. the largest CnHm/ CO/ H2/ N2(CO2) spectrum. This evaluation program has been jointly devised with and performed by the laboratory of INERIS, a French Institute devoted to safety and environment. Particular emphasis has been placed on the capability to detect combustible species at levels as low as 5% LEL (Lower Explosion Limit) that result from recent safety codes. The overall program has been break down into two parts. The response of catalytic detectors to hydrocarbon gas leaks (natural gases and naphtha vapors) has been addressed in 2004 and the corresponding results have been already published (ASME paper 2005GT68875). This first work phase has shown a satisfactory response of selected catalytic bead sensors towards the hydrocarbon paraffin series up to C8. The second phase (2005) tackled the detection of CH4/ CO/ H2/ N2(CO2) mixtures. In the authors’ knowledge, there was a lack of data in the current literature as to the performances of catalytic detection for this specific class of fuels. A wide range of mixtures was tested to cover the extensive spectrum of medium and low BTU gas fuels, including: “weak natural gas”, coal derived process gas (coke oven, blast furnace gas; COREX gas; etc.) and syngas. CO2 and N2 were used as inert components in concentrations from 20 to 80% vol. This paper summarizes the results of this second evaluation phase. A satisfactory response to the different CH4/ CO/ H2/ N2(CO2) mixtures has been obtained in terms of sensitivity, accuracy and detection limits which satisfies the requirements of current codes and standards. The overall program confirms the possibility to use catalytic bead sensors as a single detection technology for covering virtually all the gas turbine applications, This includes, apart from natural gas: LPG, light distillates (naphtha; gas condensates and NGL), “weak” natural gas, Medium & Low BTU fuels (Coke Oven; Blast Furnace), hydrogen-rich fuels (refinery) and the syngas segments with however the notable exclusion of middle distillates (gasoil, kerosene).
Modeling of Rough Wall Boundary Layer Transition and Heat Transfer on Turbine Airfoils
Authors: Stripf M. , Schulz A. , Bauer H.-J.
Published: September 2008

A new model for predicting heat transfer in the transitional boundary layer of rough turbine airfoils is presented. The new model makes use of extensive experimental work recently published by the current authors. For the computation of the turbulent boundary layer a discrete element roughness model is combined with a two-layer model of turbulence. The transition region is modeled using an intermittency equation that blends between the laminar and turbulent boundary layer. Several intermittency functions are evaluated in respect of their applicability to rough-wall transition. To predict the onset of transition a new correlation is presented, accounting for the influence of free-stream turbulence and surface roughness. Finally the new model is tested against transitional rough-wall boundary layer flows on high-pressure and low-pressure turbine airfoils.
A Novel Approach to Predicting NOx Emissions From Dry Low Emissions Gas Turbines
Authors: Syed Khawar J. , Roden Kirsten , Martin Peter
Published: September 2008

An empirical modelling concept for the prediction of NOx emissions from Dry Low Emissions (DLE) gas turbines is presented. The approach is more suited to low emissions operation than are traditional approaches. The latter, though addressing key operating parameters, such as temperature and pressure drop, do not address issues such as variation in fuel/air distribution through the use of multi fuel stream systems, which are commonly applied in DLE combustors to enable flame stability over the full operating range. Additionally the pressure drop dependence of NOx in such systems is complex and the exponent of a simple pressure drop term can vary substantially. The present approach derives the NOx model from the equations that govern the NOx chemistry, the fuel/air distribution and the dependence of the main reaction zone upon its controlling parameters. The approach is evaluated through comparing its characteristics with data obtained from high pressure testing of a DLE combustor fuelled with natural gas. The data were acquired at a constant pressure and preheat temperature (14 Bara and 400°C) and a range of flame temperatures and flow rates. Though the model is configured to address both relatively fast and slow NOx formation routes, the present validation is conducted under conditions where the latter is negligible. The model is seen to reproduce key features apparent in the data, in particular the variable pressure drop dependence without any ad-hoc manipulation of a pressure drop exponent.
Implementation and Operation of a CCGT Power Plant for a Chemical Plant: How to Cover Special Steam Conditions
Authors: Bercsi Gabor , Czibere Zsolt , Varga Viktor
Published: September 2008

TVK, as one of the leader companies of chemical industry in Central-Europe, in 2000 decided to place their heat and electricity supply on new bases. The long term steam supply from Power Plant Tiszapalkonya seemed to be not secured due to restricted environmental regulation. TVK intended to extend its polyolefin production facility which has increased the steam demand. TVK decided to construct a boiler plant/power plant with the following requirements: • long-term, secure and economical steam supply meeting the entire steam demand of TVK supplied from a source other than its own, • an acceptable time frame for the implementation and the development of the project, • the lowest possible capital requirement (involvement of a professional investor), • in the case of electricity generation, it may only be carried out through cogeneration with heat, with the minimization of condensing electricity generation, with regard to the process of the opening of the electricity market. The power plant project has been realized through a project company established by TVK and North Hungarian Electricity Distribution Co. where the chemical company has 26%, the professional investor has 74% ownership. The construction of the power plant started at the beginning of 2002 and finished in 2004. The installed steam capacity of the project is 250 t/h the power output is 35 MW. The plant has been delivered by Siemens-Transelektro consortia based on turn-key EPC Contract. The plant consists of a Siemens SGT 600 (former GT10B) gas turbine with supplementary fired HRSG and a Siemens ST-6 steam turbine and three auxiliary boilers with 65 t/h steam capacity each. The paper to be presented shows the decision making process concerning the power plant investment. It describes the technical scheme of the project and outlines the special technical features of the steam supply arising from the unusual steam load of TVK especially during start-up, shut-down and forced outages of the olefin plants which requires high additional steam supply in short time. It shows the experiences of the first year of operation too, how the plant has been able to fulfill its design criteria.
Influence of Air Humidity on the Oxidation of CO in Syngas Diffusion Flames
Authors: Zhang Zhedian , Xiao Yunhan , Wang Yue , Nie Chaoqun
Published: September 2008

Combustion of syngas with humid air is important for integrated coal gasification humid air turbine cycle for power generation. In contrast to hydrocarbon fuels, CO exists in bulky content in syngas. Thus the influence of air humidity on the oxidation of CO in syngas flames should be well understood. In the present study, the influence of air humidity on CO oxidation in syngas diffusion flames was investigated both experimentally and numerically. In the experiment, CO, CO2, O2 and temperature profiles in a model combustor of a syngas turbulent jet diffusion flame were measured. It was found that as the mass flow rate of dry air and the exhaust temperature kept constant, the profile of CO was influenced by air humidity, but CO exhaust did not exhibit a monotone increase over humidity. There exist an inflexion at the case of absolute humidity of the air X = 6.0. In addition, CO emission decreases with the increase of the thermal load. And the influence of the humidity on CO oxidation was not obviously when the thermal load is high. In the numerical simulation, flow field in the combustor was calculated by applying the composition PDF transport model and Flamelet model respectively. The numerical results were compared with the experiment and the PDF model was verified that it is more suited to simulate the CO oxidation. From the numerical analysis, it was found that the concentration of OH wasn’t monotonously increased with the added H2O and this directly affect the oxidation of CO via CO + OH → CO2 + H. In general, the influence of air humidity on the oxidation of CO in syngas diffusion flames depends on the coupling and competition of chemistry and fluid mechanics aspects. This helps to interpret the discrepancy of the results of gas turbine combustor test.
Sector Rig Test of a Ceramic Matrix Composite (CMC) Combustor Liner
Authors: Vedula Venkat , Shi Jun , Liu Shiling , Jarmon David
Published: September 2008

Ceramic Matrix Composite (CMC) combustor liners, due to their high temperature capability, enable the elimination of film cooling present in current metallic liners without increasing the pressure drop in the combustor section of a gas turbine engine. The absence of film cooling and the higher temperature capability of the CMC liner leads to complete combustion of carbon monoxide (CO) close to the combustor walls, resulting in a lower emissions combustor. The benefit of lower CO emissions was predicted through the use of stirred reactor network models in which a series/parallel set of individual perfectly stirred reactors (PSRs) is coupled to simulate a combustor. The paper describes the component design and analysis, emissions modeling, fabrication, and sector rig testing of silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) combustor liners.
Application of a Computational Code to Simulate Interstage Injection Effects on GE Frame 7EA Gas Turbine
Authors: Bagnoli M. , Bianchi M. , Melino F. , Peretto A. , Spina P. R. , Ingistov S. , Bhargava R. K.
Published: September 2008

This paper investigates effects of interstage water injection on the performance of a GE Frame 7EA gas turbine using aero-thermodynamic modeling. To accomplish this objective a computational code, written in Fortran 90 language and developed by DIEM – University of Bologna, has been used. The calculation procedure considers effects of evaporation of injected water within the compressor including droplets dynamics which are necessary in order to fully evaluate effects of wet compression on the gas turbine performance. The robustness of the computational code is demonstrated by evaluating stage-by-stage compressor performance and the overall gas turbine performance in presence of inlet evaporative fogging, overspray fogging and interstage water injection. The presented results show that water injection location influences compressor stage loading redistribution differently. The plausible explanations to the observed trends of various performance parameters are presented in the paper.
Investigations of a Syngas-Fired Gas Turbine Model Combustor by Planar Laser Techniques
Authors: Tsurikov Michael , Meier Wolfgang , Geigle Klaus-Peter
Published: September 2008

In order to investigate the combustion behavior of gas turbine flames fired with low-caloric syngases, a model combustor with good optical access for confined, non-premixed swirl flames was developed. The measuring techniques applied were particle image velocimetry, OH* chemiluminescence detection and laser-induced fluorescence of OH. Two different fuel compositions of H2, CO, N2 and CH4, with similar laminar burning velocities, were chosen. Their combustion behavior was studied at two different pressures, two thermal loads and two combustion air temperatures. The overall lean flames (equivalence ratio 0.5) burned very stably and their shapes and combustion behavior were hardly influenced by the fuel composition or by the different operating conditions. The experimental results constitute a data-base that will be used for the validation of numerical combustion models and form a part of a co-operative EC project aiming at the development of highly efficient gas turbines for IGCC (Integrated Gasification Combined Cycle) power plants.
Three Reactors Chemical Looping Combustion for High Efficiency Electricity Generation With CO2 Capture From Natural Gas
Authors: Lozza Giovanni , Chiesa Paolo , Romano Matteo , Savoldelli Paolo
Published: September 2008

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is accomplished by the oxygen carried by a metal oxide, circulating across two reactors: a reduction reactor (reducing the metal oxide by oxidizing the natural gas fuel) and an oxidation reactor (re-oxidizing the metal by reacting with air, a strongly exothermic reaction). The system produces: (i) a stream of oxidation products (CO2 and H2O), ready for carbon sequestration after water separation and CO2 liquefaction; (ii) a stream of hot air (deprived of some oxygen) used as working fluid of a gas turbine cycle. Due to the moderate temperature (∼850°C) of this stream, sensibly lower than those adopted in commercial gas turbines, the combined cycle arranged around this concept suffers from poor conversion efficiency and, therefore, economics. In the present paper, the basic CLC arrangement is modified by inserting a third reactor in the loop. This reactor, by exploiting an intermediate oxidation state of the circulating metal, produces H2 used as decarbonized fuel to raise the temperature of the air coming from the oxidation reactor, up to the highest value allowed by the modern gas turbine technology (∼1350°C), thus achieving elevated efficiency and specific power output. This paper is aimed to assess the potential of power cycles based on the three reactors (CLC3) arrangement. More specifically, we will discuss the plant configuration, the process optimization and the performance prediction. Results show that the CLC3 system is very promising: the net LHV efficiency of the best configuration exceeds 51%, an outstanding figure for a natural gas power cycle producing liquid, disposal-ready CO2 and negligible NOx emissions. Commercial gas turbines can be easily adapted to operate in the specific conditions of the CLC3 arrangement which, apart from the reactors system, does not require the development of novel technologies and/or high-risk components. The paper also reports a final comparison with a rival technology based on natural gas partial oxidation, water-gas shift reaction and CO2 separation by MDEA absorption. This work has been performed within the research on the Italian Electrical System “Ricerca di Sistema”, Ministerial Decrees of January 26 – 2000, and April 17 – 2001.
Measurement of Heat Transfer Coefficient Distributions and Flow Field in a Model of a Turbine Blade Cooling Passage With Tangential Injection
Authors: Ling John P. C. W. , Ireland Peter T. , Harvey Neil W.
Published: September 2008

In certain regions of turbine aerofoils, cooling system designers need to cool the blades with convection systems that provide high heat transfer coefficients. The present research has investigated a circular cooling passage with tangential injection suitable for a blade leading edge. The heat transfer coefficients are measured using the conventional transient heat transfer, liquid crystal technique. The results are compared to the data from steady state experiments performed by Hedlund et al. [1]. The cooling system performance is compared in detail to average data from earlier tangential injection experiments and to local heat transfer coefficient expected from a normal impingement system. The vortex flow field was also studied by numerical prediction and near-wall velocity measurements. The investigation of the flow structure has led to understanding of flow mechanisms responsible for the high heat transfer coefficient. The vortex flow field was also investigated using computational fluid dynamics and with hot wire anemometry. The latter near wall measurements were combined with the law of the wall and Colburn analogy to validate the flow and heat transfer measurements.
Technical Economic Evaluation of a System for Electricity Production With CO2 Capture Using a Membrane Reformer With Permeate Side Combustion
Authors: Manzolini G. , Dijkstra J. W. , Macchi E. , Jansen D.
Published: September 2008

The paper investigates the application of a novel concept, based on a membrane reactor with permeate side combustion (MRPC), to capture CO2, in a natural gas fuelled power plant. The MRPC combines the steam reforming reaction on the feed side and hydrogen separation through a dense hydrogen selective membrane, with combustion of part of the permeated hydrogen, using a mixture of steam, nitrogen and air as a sweep gas. The remaining hydrogen permeated is used in the gas turbine of the combined cycle. The unconverted fuel in the high pressure CO2 rich stream exiting from the membrane reactor is burned with oxygen to permit carbon dioxide sequestration. The thermodynamic performance and economic prospects of a power plant incorporating MRPC are investigated, with a sensitivity analysis on several parameters involved. The membrane surface area required is calculated using a membrane reactor model. The final results indicate a carbon capture ratio of 100% and a net overall efficiency close to 50%. If compared to a conventional natural gas fuelled combined cycle without CO2 capture, this technology leads to an increase in cost of electricity of about 30% and a CO2 avoidance cost of about 30 €/tCO2.
Migration of Film-Coolant From Slot and Hole Ejection at a Turbine Vane Endwall
Authors: Kost Friedrich , Mullaert Arnold
Published: September 2008

Thermodynamic and aerodynamic measurements at and near the endwall of turbine vanes were carried out in a linear cascade with a transonic flow field. The investigations were performed in the Windtunnel for Straight Cascades at DLR Go¨ttingen at representative dimensionless engine conditions of Mach and Reynolds number, Ma2is = 1.0 and Re2 = 850 000 respectively. The endwall film cooling configuration consisted of a slot in front of the vanes, film cooling holes inside the vane passages and a groove simulating the slit between two adjacent vane platforms, but there was no coolant leakage from the groove. Laser-Two-Focus velocimetry (L2F) was used to determine local velocities in the vicinity of the endwall. At a much larger number of locations compared to the velocity measurements the L2F-device was utilized as a seeding particle counter which enabled the determination of local coolant concentration. With these concentration measurements the migration of coolant from the different origins could be traced through the vane passage. By extrapolating the measured concentration values to the endwall adiabatic film cooling effectiveness could be obtained. The measurements at the present slot configuration were compared with previous ones [1, 2] where the slot position was closer to the vane entrance. Whereas the coolant ejection at the previous slot position produced a much more intense horse shoe vortex than without coolant, the new slot position causes no increase of secondary flow. This result proves the previous statement that positioning a coolant opening flush near the saddle point of the upstream endwall boundary layer stagnation region should be avoided. The new slot position improved film cooling effectiveness compared to the previous ones even with half the amount of coolant. By investigating the migration of film coolant from the holes inside the vane passage, ineffective holes could be identified and suggestions for improving the film coolant configuration could be given. At one location adiabatic film cooling effectiveness from these aerodynamic measurements could be compared with a thermodynamic measurement using infrared imaging.
Turbine Blade Film Cooling Study: The Effects of Showerhead Geometry
Authors: Zhang Luzeng , Moon Hee Koo
Published: September 2008

To optimize turbine blade showerhead film cooling, detailed film effectiveness was measured for four different showerhead geometries in a warm cascade simulating realistic engine operation conditions. Local film effectiveness distributions were obtained on both the pressure and suction surfaces of blade models using the pressure sensitive paint (PSP) technique. The four different geometries that have been investigated include: baseline geometry with a three-row showerhead; reduced injection angle geometry; a two-row geometry and increased diameter geometry. Nitrogen gas was used to simulate cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to have a coherent comparison between the different geometries. Local film effectiveness distributions were measured for each of the cooling mass flows. Then the distributions were spanwise averaged for comparison. Reducing the injection angle or increasing the hole diameter, the film effectiveness improved slightly for a fixed total coolant flow. The two-row injection resulted in poor film effectiveness distribution possibly due to jet lift-off as it had higher momentum compared to the three-row injection.
Effects of Surface Deposition, Hole Blockage, and TBC Spallation on Vane Endwall Film-Cooling
Authors: Sundaram N. , Thole K. A.
Published: September 2008

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film-cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film-cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film-cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.
A Dynamic Bulk SOFC Model Used in a Hybrid Turbine Controls Test Facility
Authors: Liese Eric A. , Gemmen Randall S. , Smith Thomas P. , Haynes Comas L.
Published: September 2008

The paper will describe the dynamic model of a pressurized Solid Oxide Fuel Cell (SOFC). The model is required to run on a digital controller in real-time so that its predicted thermal output may be used to control the fuel valve of an experimental hybrid system that is being used to investigate control methods for fuel cell / gas turbine hybrid systems. The model presented is a bulk model in order to best guarantee real-time operation. The equations and parameters used in the model are presented. The effects of pressure are partially considered and a V-I and P-I curve are plotted in order to show the general fuel cell model behavior. Also presented are dynamic comparisons to a 1-D model. The integration of the model with the experimental system is shown as well.
Computations of Turbulent Flow and Heat Transfer Through a Three-Dimensional Non-Axisymmetric Blade Passage
Authors: Saha Arun K. , Acharya Sumanta
Published: September 2008

The design of a three-dimensional non-axisymmetric end-wall is carried out using three-dimensional numerical simulations. The computations have been conducted both for the flat and contoured end-walls. The performance of the end-wall is evaluated by comparing the heat transfer and total pressure loss reduction. The contouring is done in such a way to have convex curvature in the pressure side and concave surface in the suction side. The convex surface increases the velocity by reducing the local static pressure while concave surface decreases the velocity by increasing the local pressure. The profiling of the end-wall is done by combining two curves, one that varies in the streamwise direction while the other varies in the pitchwise direction. Several contoured end-walls are created by varying the streamwise variation keeping the pitchwise curve constant. The flow near the contoured end-wall is seen to be significantly different than that of flat end-wall. The contoured end-wall is found to reduce the secondary flow by decreasing radial pressure gradient. The total pressure loss is also lower and the average heat transfer reduces by about 8% compared to the flat end-wall. Local reductions in heat transfer are significant (factor of 3). This study demonstrates the potential of three-dimensional end-wall contouring for reducing the thermal loading on the end wall.
Continuing Improvements of 20MW-Class GT Kawasaki L20A
Authors: Tanaka Ryozo , Sugimoto Takao , Ryu Masanori , Kinugawa Masayoshi , Tsuji Koichiro
Published: September 2008

Kawasaki Heavy Industries launched the first model of L20A gas turbine, rated at 18MW, in 2001 [1]. After the first model was launched, continuing improvements in both performance and durability have been made [2]. This paper describes the latest improvement activities, including cooling improvement of the 1st stage turbine blades using the results from an optical pyrometer thermal mapping system (Rotamap II) and performance improvements achieved by reducing the secondary air flow. In addition, by applying the non-cooled 2nd stage turbine blades made of single crystal material, plus improved rim sealing structure, cavity temperature was kept below the desired limit with a reduced amount of cooling air being required. KHI also developed a L20A “STEAM INJECTION” version. This system enables the utilization of the variable surplus steam of a cogeneration plant to increase the electric output. This paper describes the test result of L20A model gas turbine with steam injection capabilities. In the test, performance and emissions were measured as usual, but in addition, metal temperature of 1st stage blade was measured using the pyrometer system in order to confirm the propriety of the TIT de-rate schedule which keeps the metal temperature at the same level as the L20A “NORMAL” version under the steam injected condition.
Fog and Overspray Cooling for Gas Turbine Systems With Low Calorific Value Fuels
Authors: Khan Jobaidur Rahman , Wang Ting
Published: September 2008

During the summer, power output and the efficiency of gas turbines deteriorate significantly. Gas turbine inlet air fog cooling is considered a simple and cost-effective method to increase power output as well as, sometimes, thermal efficiency. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. With continued increase of volatility of natural gas prices and concerns regarding national energy security, alternative fuels such as low calorific value (LCV) synthetic gases (syngas) derived from gasification of coal, petroleum coke, or biomass are considered as important common fuels in the future. The effect of fogging/overspray on LCV fuel fired gas turbine systems is not clear. This paper specifically investigates this issue by developing a wet compression thermodynamic model that considers additional water and LCV fuel mass flows, non-stoichiometric combustion, and the auxiliary fuel compressor power. An in-house computational program, FogGT, has been developed to study the theoretical gas turbine performance by fixing the pressure ratio and turbine inlet temperature (TIT) assuming the gas turbine has been designed or modified to take in the additional mass flow rates from overspray and LCV fuels. Two LCV fuels of approximately 8% and 15% of the NG heating values, are considered respectively. Parametric studies have been performed to consider different ambient conditions and various overspray ratios with fuels of different low heating values. The results show, when LCV fuels are burned, the fuel compressor consumes about 10–18% of the turbine output power in comparison with 2% when NG is burned. LCV fueled GT is about 10–16% less efficient than NG fueled GT and produces 10–24% of net output power even though LCV fuels significantly increase fuel compressor power. When LCV fuels are burned, saturated fogging can achieve a net output power increases approximately 1–2%, while 2% overspray can achieve 20% net output enhancement. As the ambient temperature or relative humidity increases, the net output power decreases. Fog/overspray could either slightly increase or decrease the thermal efficiency depending on the ambient conditions.
Experimental Evaluation of an Inlet Profile Generator for High Pressure Turbine Tests
Authors: Barringer M. D. , Thole K. A. , Polanka M. D.
Published: September 2008

Improving the performance and durability of gas turbine aircraft engines depends highly on achieving a better understanding of the flow interactions between the combustor and turbine sections. The flow exiting the combustor is very complex and it is characterized primarily by elevated turbulence and large variations in temperature and pressure. The heat transfer and aerodynamic losses that occur in the turbine passages are driven primarily by these spatial variations. To better understand these effects, the goal of this work is to benchmark an adjustable turbine inlet profile generator for the Turbine Research Facility (TRF) at the Air Force Research Laboratory (AFRL). The research objective was to experimentally evaluate the performance of the non-reacting simulator that was designed to provide representative combustor exit profiles to the inlet of the TRF turbine test section. This paper discusses the verification testing that was completed to benchmark the performance of the generator. Results are presented in the form of temperature and pressure profiles as well as turbulence intensity and length scale. This study shows how one combustor geometry can produce significantly different flow and thermal field conditions entering the turbine. Engine designers should place emphasis on obtaining accurate knowledge of the flow distribution within the combustion chamber as this can result in significantly different inlet profiles to the turbine that can change local aerodynamics and heat transfer within the turbine.
Design Features and Performance Details of Brush Seals for Turbine Applications
Authors: Neef Matthias , Sulda Erik , Su¨rken Norbert , Walkenhorst Jan
Published: September 2008

Adaptive and contacting seals such as brush seals have been successfully applied to turbomachinery for several years. In large steam turbine applications, however, various challenges still persist. Special focus is directed at the long-term performance and longevity of brushes on conventional spring-backed seal segments in steam turbines. This issue is particularly related to wear during startup conditions. This paper discusses the results of wear tests, derived from simulated transient turbine behavior, where the resultant seal leakage under steady state conditions is monitored. It is shown that the brush seal is significantly capable of adapting to varying operating conditions, but exhibits a degree of performance degradation during the initial startups. Together with previously reported mid-term wear data and an experience based long-term phenomenological approach a general model for brush seal performance degradation is developed. This model can be used for performance prediction and exerts influence on brush seal design.
A Way to Deal With Model-Plant Mismatch for a Reliable Diagnosis in Transient Operation
Authors: Borguet S. , Dewallef P. , Le´onard O.
Published: September 2008

Least-squares health parameter identification techniques such as the Kalman filter have been massively used to solve the problem of turbine engine diagnosis. Indeed, such methods give a good estimate provided that the discrepancies between the model prediction and the measurements are zero-mean, white random variables. In turbine engine diagnosis, however, this assumption does not always hold due to the presence of biases in the model. This is especially true for transient operation. As a result, the estimated parameters tend to diverge from their actual values which strongly deteriorates the diagnosis. The purpose of this contribution is to present a Kalman filter diagnosis tool where the model biases are treated as an additional random measurement error. The new methodology is tested on simulated transient data representative of a current turbofan layout. While relatively simple to implement, the newly developed diagnosis tool exhibits a much better accuracy than the original Kalman filter in the presence of model biases.
Laser Vibrometry for Real-Time Combustion Stability Diagnostic
Authors: Giuliani Fabrice , Wagner Bernhard , Woisetschla¨ger Jakob , Heitmeir Franz
Published: September 2008

Laser-based diagnostics for combustion monitoring are promising sensing techniques for the upcoming generation of build-in gas turbines measurement and control devices. Their principles are usually based on direct measurement of line-of-sight transmission, absorption, scattering or re-emission of laser light through the flame. We discuss here how a similar method based this time on interferometry can provide a refined analysis on dynamics of injected reactants and flame stability. Measurements are performed on a resonant premixed air/methane flame using Laser Vibrometry (LV). A method for detection of combustion instability within the primary zone is described, and dual LV measurements performed over the full flame cross section provide a refined analysis of the flow patterns. This technique, originally dedicated to structural dynamics, shows a high potential for low-cost and rapid flow characterisation during the benchmark tests of a gas turbine combustor. The discussion ends on feasibility for embarking Laser Vibrometry as a real-time combustion monitor.