bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation of Steady and Dynamic Performance of a Small Turbojet Engine
Authors: Chiang Hsiao-Wei D. , Hsu Chih-Neng , Lai Aling , Lin Royce
Published: February 2009

An investigation was conducted to perform study of small turbojet engine testing and analysis. This program was mainly to investigate the current steady and dynamic performance of a 12-pound thrust turbojet engine. As a result, we can establish the basis for future small turbojet engine design guidelines. This program involved the bench testing of the small turbojet engine at both design and off-design conditions, in order to establish the baseline performance of the engine. Using the PC based data acquisition system, we will be able to test the engine for both steady and dynamic performance and record data for different operating conditions, especially, during very rapid acceleration and deceleration of the engine at different rates. Also, a compressor map testing was conducted to provide the compressor map data to be used by the performance analysis. With the above testing, this program will establish a useful database for the 12-pound thrust turbojet engine. A performance analysis using GASTURB cycle analysis software was performed for performance prediction of the small turbojet engine for both steady state conditions and dynamic transient conditions. Both performance predictions agreed reasonably well with actual performance of the engine.
The Role of High Performance Foil Bearings in an Advanced, Oil-Free, Integral Permanent Magnet Motor Driven, High-Speed Turbo-Compressor Operating Above the First Bending Critical Speed
Authors: Swanson E. E. , Heshmat H. , Shin J. S.
Published: February 2009

The demand for high power density, reliable, low maintenance, oil-free turbomachinery imposes significant demands on the bearing system. The full benefits of high speed, permanent magnet driven machines, for example are realized at speeds exceeding the capabilities of rolling element bearings. The high speeds, and a desire for oil-free operation also make conventional liquid lubricated bearings an undesirable alternative. The modern, oil-free foil bearing provides an excellent alternative, providing low power loss, adequate damping for supercritical operation, tolerance of elevated temperatures and long life. In this paper, the application of modern foil bearings to a high speed, oil-free turbo-compressor is discussed. In this demanding application, foil bearings support a 24 pound, multi-component rotor operating at 70,000 RPM with a bending critical speed of approximately 43,000 RPM. Stable and reliable operation over the full speed range has been demonstrated. This application also required low bearing start-up torque for compatibility with the constant torque characteristic of the integral permanent magnet motor. This work discusses the rotor bearing system design, the development program approach, and the results of testing to date. Data for both a turbine driven configuration, as well as a high speed integral motor driven configuration are presented.
Effects of Flow Injection From Outer Casing Upon Turbine Nozzle Vane Flow Field
Authors: Funazaki K. , Favaretto C. F. F. , Tanuma T.
Published: February 2009

In the present paper steady three-dimensional numerical calculations were performed in order to investigate the effects of flow injection from the outer casing upon turbine nozzle vane flow field. Several test cases were analyzed by applying different nozzle vane configurations such as the blade lean, injection slot width and distance from the leading edge. Numerical simulations were conducted considering the no injection case, 5% and 10% main stream flow injection from the outer casing. The impact of the flow injection design variables and the blade lean angle on the aerodynamic loss in terms of the energy loss coefficient and the outlet flow angle were analyzed through a parametric study.
Simulation of Rotor/Stator Interaction With a 4D Finite Volume Method
Authors: Laumert Bjo¨rn , Ma˚rtensson Hans , Fransson Torsten H.
Published: February 2009

A finite volume method for the computation of rotor/stator interaction for stages with arbitrary rotor/stator pitch ratios is presented and partly validated in this paper. The method which solves the unsteady three-dimensional Euler equations is formulated in the four-dimensional time-space domain. The method of time inclination is utilized to account for unequal pitchwise periodicity by distributing time co-ordinates at the grid nodes such that phase lagged boundary conditions can be employed. Calculated results show excellent agreement with the results of a reference solver for the validation test case. Furthermore the method was applied to the simulation of the unsteady flow field in a transonic test turbine stage with a stator/rotor pitch ratio of 1.875. The results were compared with measurements of the unsteady rotor blade pressure and a reference solver calculation where an approximate pitch ratio of 2.0 with a 6.7% scaled rotor geometry was employed. Both computational cases show satisfactory agreement with the experiments for both time averaged pressure distributions and pressure perturbation amplitudes.
CFD-Analysis of the Combustion in the Primary Stage of a Two-Stage Combustion Chamber
Authors: Hoerzer Klaus , Haselbacher Hermann , Griffiths Anthony J. , Syred Nick , Fraser Thomas A.
Published: February 2009

Combustion of wood powder may be applied in a two-stage multi-inlet combustion chamber. The primary stage of the combustion chamber has tangential air inlets to provide high swirl flow. The wood powder and its conveying air enter the gasification chamber axially through a center inlet in the bottom. The aim of the investigation was the analysis of the combustion flow of the primary stage of the combustion chamber. The calculation grid was three-dimensional and unstructured. Turbulence was modelled with the Reynolds-Stress-Model, species with mixture fraction/pdf-approach, radiation with the P1-model. Postprocessing has been done for particle tracks, the temperature distribution and tangential velocity distribution and for the species distributions of solid carbon, carbon monoxide, carbon dioxide and oxygen as well.
Film Cooling on a Modern HP Turbine Blade: Part II — Compound-Angle Round Holes
Authors: Walters D. Keith , Leylek James H. , Buck Frederick A.
Published: February 2009

A well-tested computational methodology and a companion experimental study are used to analyze the physics of compound-angle, cylindrical-hole film cooling on the pressure and suction surfaces of a modern high-pressure turbine airfoil. A single-passage cascade (SPC) is used to model the blade passage flow experimentally and computationally. Realistic engine conditions, including transonic flow, high turbulence levels, and a nominal density ratio of 1.52, are used to examine blowing ratios of 1.0, 1.5, and 2.0 on the suction surface (SS) and 1.5, 3.0, and 4.5 on the pressure surface (PS). The predicted results agree with experimental trends, and differences are explained in terms of known deficiencies in the turbulence treatment. The mean-flow physics downstream of coolant injection are influenced primarily by a single dominant vortex that entrains coolant and mainstream fluid, and by the effect of convex (SS) or concave (PS) curvature on the coolant jet.
Improving a Vaned Diffuser for a Given Centrifugal Impeller by 3D Inverse Design
Authors: Zangeneh Mehrdad , Vogt Damian , Roduner Christian
Published: February 2009

In this paper the application of 3D inverse design code TURBOdesign−1 to the design of the vane geometry of a centrifugal compressor vaned diffuser is presented. For this study the new diffuser is designed to match the flow leaving the conventional impeller, which is highly non-uniform. The inverse method designs the blade geometry for a given specification of thickness and blade loading distribution. The paper describes the choice of loading distribution used in the design as well as the influence of the diffuser inlet flow distribution on the vane geometry and flow field. The flow field in the new diffuser is analysed by a 3D viscous flow code and the result is compared to that of the conventional diffuser. Finally the results of testing the stage performance of the new diffuser is compared with that of the conventional stage.
Siemens Westinghouse Advanced Turbine Systems Program Final Summary
Authors: Diakunchak Ihor S. , Gaul Greg R. , McQuiggan Gerry , Southall Leslie R.
Published: February 2009

This paper summarises achievements in the Siemens Westinghouse Advanced Turbine Systems (ATS) Program. The ATS Program, co-funded by the U.S. Department of Energy, Office of Fossil Energy, was a very successful multi-year (from 1992 to 2001) collaborative effort between government, industry and participating universities. The program goals were to develop technologies necessary for achieving significant gains in natural gas-fired power generation plant efficiency, a reduction in emissions, and a decrease in cost of electricity, while maintaining current state-of-the-art electricity generation systems’ reliability, availability, and maintainability levels. Siemens Westinghouse technology development concentrated on the following areas: aerodynamic design, combustion, heat transfer/cooling design, engine mechanical design, advanced alloys, advanced coating systems, and single crystal (SC) alloy casting development. Success was achieved in designing and full scale verification testing of a high pressure high efficiency compressor, airfoil clocking concept verification on a two stage turbine rig test, high temperature bond coat/TBC system development, and demonstrating feasibility of large SC turbine airfoil castings. The ATS program included successful completion of W501G engine development testing. This engine is the first step in the W501ATS engine introduction and incorporates many ATS technologies, such as closed-loop steam cooling, advanced compressor design, advanced sealing and high temperature materials and coatings.
Assessment of Aqua-Ammonia Refrigeration for Pre-Cooling Gas Turbine Inlet Air
Authors: Al-Bortmany Jamal N.
Published: February 2009

Power providers in Oman encounter the greatest demand for electricity during the summer months. More than 70% of Oman electric power originate from gas turbines. Unfortunately, the power output of gas turbines decreases with increasing ambient temperature. The growth in electricity generation to the summer peak load has been achieved at a very high cost of installing new generators. This paper presents an assessment of using the exhaust heat to run an aqua-ammonia refrigeration system to cool the inlet air. The performance of two General Electric aeroderivative gas turbines, the LM2500+ and the LM1600, with and without absorption refrigeration was investigated. Climate data series from Fahud, central Oman, was used for modeling the variations in ambient temperature during the year to account for the effects of climate condition in the gas turbine performance simulation. Most of the gas turbines in Oman operate on a simple cycle with exhaust heat discharged to the atmosphere. Vapor absorption refrigeration system uses heat from gas turbine exhaust as its source of energy to cool the inlet ambient air to 7°C. It was observed that the available exhaust heat from the gas turbine exceeded the heat required to run the aqua-ammonia absorption refrigeration system. For meteorological conditions existing in the particular site considered in Oman, pre-cooling gas turbine inlet air to 7°C augments power, on a yearly basis, of LM2500+ and LM1600 by 20% and 14% respectively. During the peak hours in summer months, when power is mostly needed, the percentage of power augmented climbed to 39% and 33% for the two gas turbines. It has been concluded that chilling the inlet air of the gas turbine with aqua-ammonia absorption refrigeration is technically feasible and economically appealing.
A Universal Mathematical Model for a New Combined-Cycle, Fossil-Fuel Power System (LAJ Cycle): Part 2 — Dynamic Model
Authors: Judkins Roddie R. , Armstrong Timothy R. , Labinov Solomon D.
Published: February 2009

A Universal Mathematical Model (UMM) has been developed and applied to a combined-cycle, fossil-fuel power system. The UMM includes static and dynamic models of the system. The static model allows for thermodynamic and thermochemical analyses of the basic system components (reformer, turbine, membrane separator, fuel cell, air compressor, heat exchanger, and other components) and the entire system. The dynamic model provides for mode-to-mode (a partial load to a full or nominal load) time determination for the individual system components and for the entire system. System transient modes were studied, and it was determined that the reforming reactor transition time should be no less than 200 sec, which results in a system mode-to-mode transition time of three to four minutes.
Study of Medium-Btu Fueled Gas Turbine Combustion Technology for Reducing Both Fuel-NOx and Thermal-NOx Emissions in Oxygen-Blown IGCC
Authors: Hasegawa Takeharu , Sato Mikio , Katsuki Yasunari , Hisamatsu Tohru
Published: February 2009

In order to improve the thermal efficiency of the oxygen-blown IGCC (Integrated Gasification Combined Cycle) for stricter environmental standards and cost-effective option, it is necessary to adopt the hot/dry gas cleaning system. In this system, the flame temperature of medium-btu gasified fuel is higher and so NOx production from nitrogen fixation is expected to increase significantly. Also the gasified fuel contains fuel nitrogen, such as ammonia, in the case of employing the hot/dry gas cleaning system. This ammonia is easily oxidized into fuel-NOx in the combustor. For contribution to the protection of the environment and low cost operations of all kinds of oxygen-blown IGCC, low NOx combustion technology for reducing both the fuel-NOx and thermal-NOx emission has to be developed. In this paper, we clarified effectiveness of applying both the two-stage combustion and the nitrogen injection, and the useful engineering guidelines for the low-NOx combustor design of oxygen-blown gasified, medium-btu fuels. Main results obtained are as follows: (1) Based on the fundamental combustion tests using the small diffusion burner, we clarified that equivalence ratio at the primary combustion zone has to be adjusted due to the fuel conditions, such as methane concentration, CO/H2 molar ratio, and calorific values of gasified fuels in the case of the two-stage combustion method for reducing fuel-NOx emission. (2) From the combustion tests of the medium-btu fueled combustor the two-stage combustion with nitrogen direct injection into the combustor results in reduction of NOx emission to 80ppm (corrected at 16% O2) or less, the conversion rate of ammonia to NOx was 35% under the gas turbine operational conditions for IGCC in the case where fuel contains 3% of methane and 2135ppm of ammonia. By means of nitrogen direct injection, the thermal efficiency of the plant improved by approximately 0.3 percent (absolute), compared with a case where nitrogen is premixed with gasified fuel. The CO emission concentration decreased drastically, as low as 20ppm, or combustion efficiency was kept higher than 99.9%. Furthermore, based on the fundamental combustion tests’ results, the ammonia conversion rate is expected to decrease to 16% and NOx emission to 26ppm in the case of gasified fuel that contains 0.1% methane and 500ppm of ammonia. From the above results, it is clarified that two-stage combustion method with nitrogen injection is very effective for reducing both the fuel-NOx and thermal-NOx emissions at once in IGCC and it shows the bright prospects for low NOx and stable combustion technology of the medium-btu fuel.
The National Energy Technology Laboratory’s Hybrid Power Systems Program
Authors: Dennis Richard , Samuelsen Scott , Williams Mark , Holcombe Norm , Layne Abbie
Published: February 2009

The United States Department of Energy’s National Energy Technology Laboratory (US DOE NETL) through the Strategic Center for Natural Gas (SCNG) recognizes the potential and benefits offered by the hybrid power system. In order to pursue this opportunity NETL manages a fuel cell turbine hybrid program. This program is designed to address the reduction of system costs through the resolution of technical issues and technology demonstrations. This paper reports on the status of the NETL fuel cell turbine hybrid program and the market opportunities for these systems.
Status of Pressurized SOFC/Gas Turbine Power System Development at Siemens Westinghouse
Authors: Veyo Stephen E. , Vora Shailesh D. , Litzinger Kavin P. , Lundberg Wayne L.
Published: February 2009

Pressurized solid oxide fuel cell (PSOFC)/micro gas turbine generator (MTG) hybrid power systems have the potential to generate electric power at high efficiency [circa 60% (net AC/LHV)] at multi-hundred kWe and multi-MWe capacities. Thus, good fuel economy and low CO2 emissions are positive system attributes, as are low NOx and SOx emissions due to the propensity of the SOFC for low NOx generation, the need for no firing of the gas turbine combustor during normal hybrid system power operations, and the use of desulfurized fuel. Exhaust temperatures are sufficiently high to enable the recovery of heat for steam/hot-water production, and system energy efficiencies of at least 80% are feasible. Work is ongoing at Siemens Westinghouse on three PSOFC/MTG power systems. Two, with 220 kWe and 300 kWe capacities, are proof-of-concept demonstration units. The 220 kWe PSOFC/MTG power system is in test at the National Fuel Cell Research Center, University of California-Irvine, and the 300 kWe system, which is currently being designed, will be demonstrated in two tests to be performed in Europe. The status of work on the 220 kWe and 300 kWe power systems is reviewed. The third system is to have capacity of at least 500 kWe. This system, which will be demonstrated also, is viewed as a prototype commercial product. The 500 kWe-class PSOFC/MTG concept is described and performance estimates are presented.
Integrated Testing of the Full Authority Digital Control (FADC) for the U.S. Navy’s CG-47 Class Ship Service Gas Turbine Generator (SSGTG) Sets
Authors: Connery Brian J. , Russom Dennis M. , Pineiro Ivan
Published: February 2009

Naval Surface Warfare Center, Carderock Division - Ship Systems Engineering Station (NSWCCD-SSES) successfully completed testing of a new Full Authority Digital Control (FADC) system for gas turbine control. This system will be back-fit onto Model 139 Ship Service Gas Turbine Generator Sets (SSGTGs) on the U.S. Navy’s Ticonderoga (CG-47) class cruisers. The FADC will be a direct replacement of the original Model 139 Local Operating Panel (LOCOP) and will control the Allison 501-K17 gas turbine. The new control system provides for standardized installation across a wide variety of existing configurations. The development program leveraged off of the design work done for the AG9140 FADC currently being installed on DDG 51 Class ships. The result was a state-of-the-art system ready for shipboard installation in a short period of time, providing commonality of look and feel across platforms. This paper describes the CG-47 FADC and details the development and testing conducted on a Model 139 SSGTG at the NSWCCD-SSES DDG 51 Gas Turbine Land Based Engineering Test Site (LBES). The test program included all modes of SSGTG operation, including starts, shutdowns, and generator operations under varying load conditions.
An Improved Turbulence Closure Model Using Cabot’s Near-Wall Function
Authors: Tan H. Y. , Ng E. Y. K. , Lim H. N. , Choi D.
Published: February 2009

The Wall Function for large eddy simulation (LES) proposed by Cabot is extended to the turbulence closure models. Predicted results are discussed and compared with well-documented experimental results. Although complete agreement with experiment is not yet achieved for some cases, it shows that the model with Cabot’s Wall Function significantly reduces the computing resources (CPU & storage) required where the first off-wall velocity nodes are located at 60 < y+ < 180; and in most cases improves predicted results.
Tubular Regenerator Development and Incorporation Experience
Authors: Vinogradov V. , Orberg A. , Soudarev V. , Shevchenko E.
Published: February 2009

A review of regenerative gas turbines operating at natural gas pipeline compressor stations across the Russia has been performed. Main performance characteristics, first of all, the power and efficiency of the recuperated gas turbines, many of those have been used up a design service life, can be recovered. Since a large negative effect on the performances is contributed by defective plate-type regenerators, their change seems to be essential when updating gas-pumping units. A tubular regenerator is developed and incorporated into the gas turbines for driving natural gas blowers. The regenerator being installed in place of the plate-type heat exchanger joints a rather simple fabrication process and high durability. Its design features are presented and discussed. Ways to enhance efficiency and decrease the weight of the regenerator are considered.
Design of Industrial Axial Compressor Blade Sections for Optimal Range and Performance
Authors: Sieverding Frank , Ribi Beat , Casey Michael , Meyer Michael
Published: February 2009

A design system for the blade sections of industrial axial compressors has been developed. The method combines a parametric geometry definition method, a powerful blade-to-blade flow solver (MISES) and an optimization technique (breeder genetic algorithm) with an appropriate fitness function. Particular effort has been devoted to the design of the fitness function for this application which includes non-dimensional terms related to the required performance at design and off-design operating points. It has been found that essential aspects of the design (such as the required flow turning, or mechanical constraints) should not be part of the fitness function, but need to be treated as so-called “killer” criteria in the genetic algorithm. Finally, it has been found worthwhile to examine the effect of the weighting factors of the fitness function to identify how these affect the performance of the sections. The system has been tested on the design of a repeating stage for the middle stages of an industrial axial compressor. The resulting profiles show an increased operating range compared to an earlier design using NACA65 profiles.
Investigation of Flow Pattern and Losses in Transonic Turbine Vane and Blade Cascades by Means of Laser Anemometer Measurements and Navier-Stokes Analysis
Authors: Granovski Andrei V. , Kolesov Alexei N.
Published: February 2009

This paper presents results of a complex numerical and experimental investigation of the flow structure and losses in the Vane (Ma2is = 1.0, Re = 9.8*105) and Blade (Ma2is = 1.12, Re = 7.8*105) straight cascades on transonic modes. The measurements of turbulence pulsation and mean flow velocity upstream, within and downstream of the cascades were made by means of laser anemometer (LA). The static and total pressure fields were measured upstream and downstream of the cascades to determine profile losses. The static pressure distribution on the suction and pressure surfaces was measured as well. Comparisons were made with predictions using 2D Navier–Stokes analysis. The use of the both experimental and numerical approaches allowed to eliminate separated zones more accurately, to define how these zones affected on flow structure and losses.
The Effects of Wet Compression on Gas Turbine Engine Operating Performance
Authors: Sexton Wayne R. , Sexton Michael R.
Published: February 2009

Water, in the liquid or vapor phase, injected at various locations into the gas turbine cycle has frequently been employed to improve engine performance. One such way to improve engine performance is by steam injection, of varied quantity, into the combustor section of the engine. Combustor steam injection increases turbine mass flow rate without increasing airflow rate and consequently increasing the specific power (power/lbm of air). Another approach, receiving widespread acceptance in recent years, is to inject water droplets into the inlet duct upstream of the engine compressor inlet. As the droplets evaporate, prior to entering the compressor, the inlet air is cooled subsequently decreasing compressor power and thus increasing engine power output. The present paper examines the concept of injecting water droplets, termed fogging, in excess of the amount that can be evaporated before entering the engine compressor. This excess water, termed over-spray, is carried directly into the engine compressor. The computer simulated performance of a simple cycle gas turbine engine using evaporative cooling upstream of the compressor with over-spray is reported. The paper describes an improved simulation model developed to predict compressor performance as water is evaporated while passing through the stages of an axial flow compressor. The effects are similar to those of an intercooled compressor without the complications of additional piping, heat exchangers, and the requirement for a dual spool compressor. The results of a parametric study of the effects of evaporative cooling on engine operating characteristics are presented. These results include compressor performance characteristics modified for various inlet conditions (temperature, pressure, and humidity) and fogging conditions (flow rate, over-spray, and water temperature) as well as estimates of the reduced compression work and lowered compressor discharge temperatures. These modified compressor performance characteristics are used in the engine simulation to predict how an over-sprayed engine would perform under various operating conditions. Estimates of increased output power and increased specific power are presented.
Heat Transfer and Friction Factors for Flows Inside Circular Tubes With Concavity Surfaces
Authors: Bunker Ronald S. , Donnellan Katherine F.
Published: February 2009

Heat transfer and friction coefficients measurements have been obtained for fully developed, turbulent internal flows in circular tubes with six different concavity (dimple) surface array geometries. Two different concavity depths and three different concavity array densities were tested using tube bulk flow Reynolds numbers from 20,000 to 90,000. Liquid Crystal Thermography was used to measure the temperature distributions on the outside of the concavity tubes. Using the average heat transfer coefficient for the fully developed region, the overall heat transfer enhancements are compared to baseline smooth tube results. Friction coefficients are also compared to values for a smooth tube. Dimple depths of 0.2 to 0.4 relative to the dimple surface diameter were used, with surface area densities ranging from 0.3 to 0.7. Dimple arrays were all in-line geometries. The results showed that heat transfer enhancements for dimpled internal surfaces of circular passages can reach factors of 2 or more when the relative dimple depth is greater than 0.3 and the dimple array density is about 0.5 or higher. The associated friction factor multipliers for such configurations are in the range of 4 to 6. The present study provides a first insight into the heat transfer and friction effects of various concavity arrays for turbulent flows.
Simulation of Non-Steady and Non-Linear Flow Phenomena in Complex Piping Systems of Gas Turbines
Authors: Pfeifer Uwe , Warnack Dieter
Published: February 2009

In order to get information on how pressure fluctuations in the combustion chamber of a gas turbine act on the gas piping system and adapters for measurement of pressure fluctuations, a one-dimensional, compressible, unsteady, anisentropic code is applied. This is done to obtain more detailed information about particular flow phenomena like wave propagation, superposition and the influence of heat transfer and damping. The model used was formed by using the one-dimensional equation laws of mass, momentum and energy to a hyperbolic differential equation system. This system was solved numerically by using the well proven PROMO code originating from the automotive industry as described in detail by Go¨rg [1]. The existing model was extended and adapted to be applicable to the problems described above.
Detailed and Reduced-Chemistry Descriptions for Ignition and Detonation of Propane
Authors: Petrova M. V. , Varatharajan B. , Williams F. A.
Published: February 2009

The chemistry of autoignition of propane is studied with the objective of developing reduced chemistry descriptions. A detailed mechanism of 165 reaction steps among 38 chemical species is identified. This mechanism is reduced to a short mechanism of 34 steps, by deleting steps that are unnecessary. In the short mechanism, steady-state species are identified for deriving a systematically reduced mechanism. Good agreement with measured shock-tube ignition times is found.
Measurement and Analysis of Flow in a Pre-Swirled Cooling Air Delivery System
Authors: Chew J. W. , Hills N. J. , Khalatov S. , Scanlon T. , Turner A. B.
Published: February 2009

Measurements and analysis for a pre-swirl cooling air delivery system are reported here. The experimental rig used is representative of aero-engine conditions, having 18 pre-swirl nozzles, 72 receiver holes, capable of speeds up to 11 000 rpm, and giving differences between total temperature upstream of the pre-swirl nozzles and relative total temperature measured in the receiver holes of up to 26K. Pressure and temperature measurements are reported. An elementary model is developed for calculation of the cooling air delivery temperature. This accounts for the pre-swirl nozzle velocity coefficient, moments on the stationary and rotating surfaces in the pre-swirl chamber, and flows through the inner and outer seals to the chamber. The model is shown to correlate the measurements well for a range of disc speeds and pre-swirl velocity to disc speed ratios.
Modeling the Response of Premixed Flames to Mixture Ratio Perturbations
Authors: Cho Ju Hyeong , Lieuwen Tim C.
Published: February 2009

Combustion instabilities continue to cause significant reliability and availability problems in low emissions gas turbine combustors. It is known that these instabilities are often caused by a self-exciting feedback loop between unsteady heat release rate and reactive mixture equivalence ratio perturbations. We present an analysis of the flame’s response to equivalence ratio perturbations by considering the kinematic equations for the flame front. This response is controlled by three processes: heat of reaction, flame speed, and flame area. The first two are directly generated by equivalence ratio oscillations. The third is indirect, as it is generated by the flame speed fluctuations. The first process dominates the response of the flame at low Strouhal numbers, roughly defined as frequency times flame length divided by mean flow velocity. All three processes play equal roles at Strouhal numbers of O(1). The mean equivalence ratio exerts little effect upon this transfer function at low Strouhal numbers. At O(1) Strouhal numbers, the flame response increases with decreasing values of the mean equivalence ratio. Thus, these results are in partial agreement with heuristic arguments made in prior studies that the flame response to equivalence ratio oscillations increases as the fuel/air ratio becomes leaner. In addition, a result is derived for the sensitivity of this transfer function to uncertainties in mean flame position. For example, a sensitivity of 10 means that a 5% uncertainty in flame position translates into a 50% uncertainty in transfer function. This sensitivity is of O(1) for St<<1, but has very high values for St∼O(1).
Coatings for Advanced Large Frame Combustion Turbines for Power Generation
Authors: Viswanathan R. , Cheruvu N. S. , Chan K. S.
Published: February 2009

Use of metallic coatings for protecting hot section blades and vanes of combustion turbines for power generation has been a common practice for the last three decades. Since these coatings have to be optimized both with respect to different forms of corrosion and operation (base load vs. peak load) their performance can be machine specific. Power company users generally do not have sufficient knowledge of the failure mechanisms of the coatings and the basis for selecting coatings to suit their specific requirements. This paper describes the evolution of metallic coatings, discusses failure mechanisms, and describes a methodology for comparing and selecting machine-specific coatings. The methodology, which can be used to rank and predict the remaining life of coatings and for optimizing operation, forms the basis of a computer code known as COATLIFE. The ingredients of this methodology, i.e., degradation modeling and thermomechanical fatigue life (TMF) prediction, are reviewed in the paper.
Model Analysis of High-Fogging Effects on the Work of Compression
Authors: Ha¨rtel Carlos , Pfeiffer Peter
Published: February 2009

In recent years, high fogging has received increasing attention as a comparatively simple and cost-efficient means of gas turbine power augmentation. The effects of high fogging on the work of compression are studied in this paper from a fundamental perspective. Considered is a prototype configuration, namely the evaporation of droplets in an initially saturated mixture of air and water, which is exposed to a prescribed pressure rise. Two different approaches are applied: The first approach (‘ideal model’) assumes that thermodynamic equilibrium prevails. In the second approach (‘droplet model’) the finite time of evaporation is taken into account by introducing discrete droplets and modeling explicitly the heat and mass transfer between liquid and gaseous phase. For compression speeds representative of modern gas turbines, it is found that droplets of 1μm in diameter are small enough to allow for approximate equilibrium during compression. The influence of polytropic efficiency on the gains of high fogging is addressed, and it is shown that high fogging is more effective for compressors of lower efficiency.
Impact of Geometric Variability on Axial Compressor Performance
Authors: Garzon Victor E. , Darmofal David L.
Published: February 2009

A probabilistic methodology to quantify the impact of geometric variability on compressor aerodynamic performance is presented. High-fidelity probabilistic models of geometric variability are derived using a Principal-Component-Analysis (PCA) of blade surface measurements. This probabilistic blade geometry model is then combined with a compressible, viscous blade-passage analysis to estimate the impact on the passage loss and turning using a Monte Carlo simulation. Finally, a mean-line multi-stage compressor model, with probabilistic loss and turning models from the blade-passage analysis, is developed to quantify the impact of the blade variability on overall compressor efficiency and pressure ratio. The methodology is applied to a flank-milled Integrally-Bladed Rotor (IBR). Results demonstrate that overall compressor efficiency can be reduced by approximately 1% due to blade-passage effects arising from representative manufacturing variability.
Hybrid Gas Turbine and Hydraulic Air Compressor System
Authors: White David J.
Published: February 2009

Using a hydraulic air compressor (HAC) instead of a mechanical driven compressor in a gas turbine based system can provide significant performance benefits. In particular very high thermal efficiencies can be achieved at modest firing temperatures. Although the HAC based hybrid system has many applications this paper reports on a study and analysis of such a hybrid as it might be integrated into a coal to electricity power plant. In this specific case the HAC is used to provide both compressed oxygen depleted air to a recuperated, fired turbo-expander and low-pressure oxygen enriched air to a coal gasifier. The oxygen enriched air improves the lower heating value of the derived coal gases obtained allowing them to be compressed economically and injected into the combustion system. Run-of-stream applications of the HAC can provide thermal efficiencies on the order of 70% or higher, whilst pumped approaches can achieve efficiencies around 50%. The pumped water HAC combined with a recuperated gas turbine is effectively an intercooled, and recuperated (ICR) cycle. In the non-pumped HAC systems the very high thermal efficiencies can provide coal to electricity conversion efficiencies on the order of 60%. The actual efficiency depends strongly on the type of gasifier employed and on whether or not the gasifier employs waste heat recovery. The overall cost of electricity so generated is very competitive despite the high capital costs associated with coal handling and gasification.
An Improved Preliminary Design Method for Ejectors
Authors: Millsaps Knox T. , Markowicz John C.
Published: February 2009

A preliminary design method is presented for evaluating ejector geometries and predicting variations in aerodynamic performance due to changes in configurations and flow conditions. The method is based on steady, quasi-one dimensional conservation equations for mass, momentum, and energy with corrections to account for losses due to the primary nozzle exit, inlet to the mixing tube, frictional shear forces on the mixing tube walls, and outlet non-uniformity in the velocity profile from the mixing tube. The entrainment ratio, which is defined as the induced secondary flow (cold) rate divided by the primary (hot) flow rate, is first compared to ideal performance, which is obtained without losses. Next the results of the model are compared to experimental data, obtained from several ejector configurations and flow conditions, and agreement within three percent is shown. The usefulness of this method for preliminary design trade-off studies is demonstrated by comparison with a one-fifth scale cold-flow facility. Finally, the factors that contribute to performance degradation are identified and quantified. It is shown that the primary factor limiting performance is the nonuniformity in the exit momentum flux.
Effects of Reynolds Number on the Non-Nulling Calibration of a Cone-Type Five-Hole Probe
Authors: Lee Sang Woo , Jun Sang Bae
Published: February 2009

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from −35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between 6.60 × 103 and 3.17 × 104. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number (Re = 3.17 × 104) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.
Development of a Thermal Barrier Coating Life Model
Authors: Chan K. , Cheruvu S. , Viswanathan R.
Published: February 2009

Thermal barrier coatings (TBCs) are widely used on the first stage turbine buckets and vanes of land-based (F and G class) gas turbine machines. These coatings normally fail by spallation due to delamination of the ceramic layer along the vicinity of the thermally grown oxide (TGO)/TBC interface. The failure processes involve several mechanisms including oxidation of the bond coat, thermomechanical fatigue, sintering, and spallation of the TBC. This paper describes the development of an analytical tool for predicting the useful life of TBCs for land-based gas turbine applications. The analytical model, called TBCLIFE, has been developed to treat bond coat oxidation, sintering and spallation of the TBC, as well as effects of coating thickness and substrate curvature on TBC spallation. In addition, a parallel experimental program has also been initiated to evaluate the durability of a plasma-sprayed TBC under isothermal and thermal cycling exposures. These results will be used to determine the kinetics of TGO scale growth and the material constants for the TBC life model. The TBC life model will be applied to predicting TBC life as a function of cycle time and the results will be presented as coating life diagrams. The utility of a coating life diagram for estimating the remaining life of TBC will be illustrated and discussed.
Optimized Operating Point Selection for Gas Turbine Health State Analysis by Using a Multi-Point Technique
Authors: Pinelli M. , Spina P. R. , Venturini M.
Published: February 2009

Gas turbine operating state determination can be performed using Gas Path Analysis (GPA) techniques, which use measurements taken on the machine to calculate the characteristic parameters that are indices of the machine health state. The number and type of characteristic parameters that can be evaluated depend on the number and type of the available measured variables. Thus, when there are not enough measured variables to determine all the characteristic parameters, some of them have to be estimated independently of the actual gas turbine health state. In this way, variations due to aging or deterioration which, in the actual machine, may occur on these last characteristic parameters, cause estimation errors on the characteristic parameters assumed as problem unknowns. The available instrumentation in field applications is often inadequate to ensure reliable operating state analysis when GPA-based techniques are used. This problem may be partially overcome using a multiple operating point minimization technique. This consists of the determination of the characteristic parameters that minimize the sum of the square differences between measured and computed values of the measurable variables in multiple operating points. In this way the lack of data is overcome by data obtained in different operating points. This paper describes a procedure for gas turbine operating state determination based on a multiple operating point minimization technique and presents a study aimed at selecting the best set and number of operating points that should be used.
Performance Studies of Passive Damping Techniques Used to Suppress Combustion Oscillations in LPP Combustors
Authors: Sims G. J. M. , Copplestone R. W. , Tilston J. R.
Published: February 2009

As part of an EU Framework IV programme, an investigation was undertaken into the design and performance of a variety of passive damping techniques aimed at reducing or eliminating combustion oscillations in an LPP combustor. Earlier in the programme, internal mapping of a 3-sector LPP combustor had to be temporarily suspended when significant structural damage was incurred as a result of high amplitude combustion oscillations. As a direct result, a review was undertaken to investigate damping technologies that were suitable for use within a combustion environment. Acoustic modelling techniques were used to support initial laboratory studies to establish linear absorber design rules. Following these studies, Helmholtz resonators, quarter wave tubes and a bulk absorber were tested in an experimental LPP combustor at atmospheric pressure. Attention was focussed on broadening the attenuation bandwidth whilst maintaining suitable damping performance. The bulk absorber achieved acoustic pressure reductions of up to 50%, whereas an array of combustor head mounted Helmholtz resonators achieved up to 90% pressure reduction.
Validation of a Mixed Flow Turbofan Performance Model in the Sub-Idle Operating Range
Authors: Riegler Claus , Bauer Michael , Schulte Holger
Published: February 2009

During turbofan development programs the evaluation of steady-state and transient engine performance is usually achieved by applying full thermodynamic engine models at least in the operating range between idle and maximum power conditions, but more recently also in the sub-idle operating range, e.g. for steady-state windmilling behavior and for starting, relight and shut down scenarios. The paper describes the setup, and in more detail the validation, of a full thermodynamic engine model for a two-spool mixed flow afterburner turbofan which is capable to run from maximum power down to zero speed and zero flow conditions in steady-state and transient mode. The validation is performed by using the model-based performance analysis procedure called ANSYN even in windmilling operation. Once the steady-state sub-idle model is validated the extension to transient sub-idle capability is achieved by simply adding the effects of rotor moment of inertia of the spools, while heat soakage effects are rather negligible without heat release in the burner. Especially lighting conditions in the burner are produced by such a validated sub-idle model inherently due to reliable data calculated at the burner entry station. The variety of applications of a validated full thermodynamic engine model is large. The performance data delivered is highly reliable and very consistent because the full operating range of the engine is covered with one model, and by appropriate means of speeding up the calculation even real-time capability may be achieved. In the paper synthesized data for an engine dry crank is compared to real engine test data as one typical application.
The Development of a Lean-Premixed Trapped Vortex Combustor
Authors: Bucher Jonathan , Edmonds Ryan G. , Steele Robert C. , Kendrick Donald W. , Chenevert Blake C. , Malte Philip C.
Published: February 2009

A lean-premixed trapped vortex combustor (TVC) has been developed and tested. The TVC was fired on methane and tested at the General Applied Sciences Laboratory (GASL). Additionally, for baseline data, a simple bluff body combustor was tested. All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of power generation gas turbine engines. Both bluff body and TVC data showed competitive oxides of nitrogen (NOx) emissions of <25 ppm (corrected to 15% oxygen dry condition), which served as a basis for future optimization. Combustion efficiency was routinely above 99.5%. An optimized version of the TVC incorporating flame stabilizing features displayed promising emissions: NOx/CO/UHC levels were optimized to as low as 9/9/0ppm (corrected to 15% O2 dry), with corresponding combustion efficiency above 99.9%. Because of this configuration’s robust and straightforward design, it has the potential for successful integration into a prototype engine. This paper describes the combustors, their testing and the evaluation of the test results.