bluuebunny/crossref_metadata_2025 huggingface dataset:
Coal-Based Power Plant System Configurations for the 21st Century
Authors: Rao A. D. , Samuelsen G. Scott , Robson F. L. , Geisbrecht R. A.
Published: November 2008

Under the sponsorship of the U.S. Department of Energy/National Energy Technology Laboratory, a multi-disciplinary team led by the Advanced Power and Energy Program of the University of California at Irvine is defining the system engineering issues associated with the integration of key components and subsystems into power plant systems that meet performance and emission goals of the Vision 21 program. Earlier tasks of the program have narrowed down the myriad of fuel processing, power generation, and emission control technologies to selected scenarios that identify those combinations having the potential to achieve the Vision 21 program goals of high efficiency and minimized environmental impact while using fossil fuels. These analyses have been extended to consider coal gasification processes combined with the advanced power cycles previously identified. The technology levels considered are based on projected technical and manufacturing advances being made in industry and on advances identified in current and future government supported research. Examples of systems included in these advanced cycles are solid oxide fuel cells, advanced cycle gas turbines, and membrane separation of gases.
Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane
Authors: Stripf M. , Schulz A. , Wittig S.
Published: November 2008

External heat transfer measurements on a highly loaded turbine vane with varying surface roughness are presented. The investigation comprises nine different roughness configurations and a smooth reference surface. The rough surfaces consist of evenly spaced truncated cones with varying height, diameter and distance, thus covering the full range of roughness Reynolds numbers in the transitionally and fully rough regimes. Measurements for each type of roughness are conducted at several freestream turbulence levels (Tul = 4% to 8.8%) and Reynolds numbers, hereby quantifying their combined effect on heat transfer and laminar-turbulent transition. In complementary studies a trip wire is used on the suction side in order to fix the transition location close to the stagnation point, thereby allowing a deeper insight into the effect of roughness on the turbulent boundary layer. The results presented show a strong influence of roughness on the onset of transition even for the smallest roughness Reynolds numbers. Heat transfer coefficients in the turbulent boundary layer are increased by up to 50% when compared to the smooth reference surface.
Research on Advanced Technologies for CO2 Reduction Using High Temperature Demonstrator Engine
Authors: Shinozaki Masaharu , Natsumura Tadashi , Kobayashi Kenji , Arai Mikiya , Nakajima Takurou
Published: November 2008

Research and Development of Environmentally Compatible Propulsion System for Next-Generation Supersonic Transport (ESPR Project), commenced in 1999, has its key objective for the reduction in CO2 emissions. To achieve this objective, fewer fuel consumption must be realized by increasing turbine inlet temperature and reducing cooling air flow, along with engine weight reduction. The use of new heat resistant materials may be of benefit in solving these issues. In addition, highly sophisticated temperature monitoring techniques capable of accurately measuring high temperature regions can reduce the cooling air consumption to the minimum levels. In this study, components were developed to evaluate for the possible application of new heat resistant materials — ceramics matrix composites, single crystal super-alloy, and powder metallurgy super-alloy — to hot parts of an engine. In addition, a smart sensor was developed, which can accurately measure the surface temperature distributions for all the turbine rotor blades. Finally, these components were assembled in a high-temperature demonstrator engine. And the engine was run at turbine inlet temperature of 1,923K to demonstrate the satisfactory function of these components. This paper reports about the developments, and discusses the results of the running test on the high-temperature demonstrator engine.
The Pulsating Flow Field in a Mixed Flow Turbocharger Turbine: An Experimental and Computational Study
Authors: Palfreyman D. , Martinez-Botas R. F.
Published: November 2008

The turbine stage of an automotive pulse system turbocharger is subjected to an unsteady pulsating flow field due to the rapid opening and closing of the reciprocating engine exhaust valves. This leads to a complex and highly disturbed flow field within the delivery volute and turbine passages, which results in an unusual ‘hysteresis’ type performance characteristic. The aim of this paper is to investigate the flow field within the turbine stage under these representative conditions, using a computational method validated against experimental data. This paper is separated into two sections. The first deals with the validation of the numerical code and modeling approach. A mesh dependency study is undertaken with cell discretization ranging 200,000, 850,000 and 1,750,000 cells, where the accuracy is assessed through comparison with experimental performance and flow field measurements. The second part presents an investigation of the flow field under pulse conditions. Time accurate spectra of turbine performance and flow properties at various locations in the turbine stage are presented, as well as contour plots of velocity within a turbine passage at two critical positions during the pulse period.
Pedestal and Endwall Contribution in Heat Transfer in Thin Wedge Shaped Trailing Edge
Authors: Facchini Bruno , Innocenti Luca , Tarchi Lorenzo
Published: November 2008

Short pin fins (pedestals) and long ribs (enlarged pedestals) are usually used in trailing edge cooling of turbine airfoils. To better reproduce the geometry of such cooling systems, test section of this experimental study is a wedge duct with inserts, to take into account effects of accelerating flow. A complete investigation of the system needs a separate evaluation of the heat transfer coefficients (HTC) for the pedestal surface and for the free endwall surface. In the present work an innovative technique made of different methods for these two different regions is presented, so cooling performances of each are evaluated. Thermochromic liquid crystal (TLC) transient technique is used to measure detailed heat transfer coefficients only on the endwall surface: a typical transparent (Plexiglas®) test article is used. Aluminum pedestals, employing a procedure based on a finite elements code, allow to measure the average heat transfer coefficient on the insert surface. To investigate the effects on transient technique of high conductive components, a comparison with Plexiglas inserts has been performed. Results show an underestimation of HTC with TLC transient technique only for aluminum long ribs at low Reynolds number values. Nevertheless the results seem to agree with other authors both for the endwall surface and for the entire cooling system.
Influence of Fluid-Dynamics on Heat Transfer in a Pre-Swirl Rotating-Disc System
Authors: Lock Gary D. , Wilson Michael , Owen J. Michael
Published: November 2008

Modern gas turbines are cooled using air diverted from the compressor. In a “direct-transfer” pre-swirl system, this cooling air flows axially across the wheel-space from stationary pre-swirl nozzles to receiver holes located in the rotating turbine disc. The distribution of the local Nusselt number, Nu, on the rotating disc is governed by three non-dimensional fluid-dynamic parameters: pre-swirl ratio, βp, rotational Reynolds number, Reφ, and turbulent flow parameter, λT. This paper describes heat transfer measurements obtained from a scaled model of a gas turbine rotor-stator cavity, where the flow structure is representative of that found in the engine. The experiments reveal that Nu on the rotating disc is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the pre-swirl nozzles, associated with the impinging jets from the pre-swirl nozzles. At lower coolant flow rates, the heat transfer is dominated by viscous effects. The Nusselt number is observed to increase as either Reφ or λT increases.
Advances in Power Plant Steam Blow Cleaning Analyses
Authors: Jarvis Julie M. , Babel Paul J. , Vieira Allen T.
Published: November 2008

Steam blows are used prior to initial turbine powering for steam power plants to clear debris and surface scale that could potentially damage turbine blades during plant operation. Based on experience from steam blows for several dozen plants, enhancements have been made to the techniques in the detailed engineering analysis used by plant startup to perform steam blows. This paper discusses these improvements as applied to combined cycle gas and coal power plants. The basis for steam blows is that the piping is blown, bypassing the turbine, with sufficient boiler pressure to ensure that the piping will experience a dynamic pressure to assure adequate cleaning. Typically, the boiler pressures during steam blow provide a dynamic pressure throughout the piping, which is at least 20% higher than would be experienced for all plant operating conditions. Therefore, any potentially damaging particles will be blown out of the piping prior to the turbine operation. The following improvements and enhancements, which are detailed in this paper, have recently been implemented in the analyses used to establish adequate steam blows: 1. Advanced Modeling Techniques. 2. Design Coordination with Fast Track Engineering. 3. Consideration of Multiple HRSG Plants. 4. Analysis Support During Actual Steam Blows (for site engineering and startup).
Conjugate Heat Transfer Modelling in Film Cooled Blades
Authors: Montomoli F. , Adami P. , Della Gatta S. , Martelli F.
Published: November 2008

A reliable and accurate prediction of temperature field in hot components plays a key role in design process of modern gas turbines. The first stages of turbine and the combustor basket are usually subjected to high heat transfer rates and hot gas temperatures exceed the melting point of the employed alloys. The accurate knowledge of temperature distribution could extend the life of critical components through an accurate design of coolant systems. The present work concerns the upgrade of the finite volume CFD (Computational Fluid Dynamic) solver HybFlow, (see Adami et al.[1]) to simulate heat transfer in gas turbine cooling devices. In particular, the conjugate simulation of flow field heat transfer and metal heat conduction has been considered. To this aim, the original solver has been coupled to a routine solving the Fourier equation in solid domain. This modification allows the “conjugate heat transfer” investigation of heat transfer in fluid flow and solid domain simultaneously. The code has been validated through two different test-case applications. The first is a laminar flow over a flat plate, while the second is a film-cooled plate. Finally, a complete 3D film cooled NGV (Nozzle Guide Vane) has been investigated as an example for a more complex application. The simulation couples the thermal field inside the metal and the flow field in the vane, in the two plenum channels and in the six rows of cooling channels as well.
Interaction Between Wake and Film Cooling Jets: Numerical Analysis
Authors: Adami P. , Montomoli F. , Belardini E. , Martelli F.
Published: November 2008

The present work presents the results obtained from the numerical investigation of the 3D unsteady flow field in a film-cooled turbine vane. The blade under research is the AGTB-B1 investigated in the cascade of the High Speed Cascade Wind Tunnel of the University of Armed Forces Munich. The unsteady flow consists of a wake which periodically interacts with the shower-head film cooling system of the blade nose. The paper discusses the aerodynamical interaction between the film-cooled blade and the periodic wake produced by a moving row of bars placed in a plane upstream the cascade. The predictive approach is based on a U-RANS CFD solver using a conventional two-equation closure. The unsteady CFD results are discussed against the experimental data available. Special emphasis is devoted to the unsteady interaction of the wake with the shower-head film-cooling system of the blade.
Experimental and Numerical Investigation of Stationary Ribbed Ducts
Authors: Magi A. , Montomoli F. , Adami P. , Carcasci C.
Published: November 2008

Goal of this work is to define the main issues and guidelines for an accurate heat transfer CFD simulation of internal ribbed ducts. To this aim, two different ribbed ducts (AR = 1,3) have been experimentally investigated to obtain a data set useful to validate numerical analyses. Experimental HTC contour maps have been obtained using unsteady TLC technique. CFD activity deals with numerical simulation using both a commercial (Star-CD™) and an “in house” solver (HybFlow). Four different variants of the well-known two-equation turbulence models have been considered. Low cost heat transfer predictions of internal ducts are highly demanded by industry despite the uncommon complexity of modern internal coolant system. Accordingly, the main aim of the work is to provide some indications for the numerical modelling and to evaluate the accuracy level of predicted heat transfer when commercial or research packages are employed along with different grid resolution levels. Overall results are in good agreement with experimental data even if some local discrepancies are present.
The Experiment Research on the Performance of Low Speed Axial-Compressor by External Acoustic Excitation
Authors: Li Zhi-Ping , Gong Zhi-Qiang , Liu Yan , Lu Ya-Jun
Published: November 2008

This paper investigates the control of large-scale separated flows inside a low-speed axial-compressor by using external acoustic excitations. Experiment studies on the characteristics of flow field and the performance of compressors under external unsteady acoustic excitations are carried out in a low speed axial-compressor. The results indicate that the excitation frequency and excitation amplitude are of key importance for controlling large-scale separated flows. When the unsteady excitation is of the most effective frequency with proper amplitude, the large-scale separated flow is controlled effectively and the flow field becomes more regular near the compressor’s stall margin. At the same time, the performances of the compressor are enhanced: the efficiency is increased by about 1∼2%, the pressure ratio is increased by 2∼3% and the stall margin of the compressor is broadened remarkably too.
Unsteady Boundary Layer Development Due to Wake Passing Effects on a Highly Loaded Linear Compressor Cascade
Authors: Hilgenfeld Lothar , Pfitzner Michael
Published: November 2008

The effects of wake passing on boundary layer development on a highly loaded linear compressor cascade were investigated in detail on the suction side of a compressor blade. The experiments were performed in the High Speed Cascade Wind Tunnel of the Institut fuer Strahlantriebe at Mach and Reynolds numbers representative for real turbomachinery conditions. The experimental data were acquired using different measurement techniques, such as fast-response Kulite sensors, hot-film array and hot-wire measurements. The incoming wakes clearly influence the unsteady boundary layer development. Early forced transition in the boundary layer is followed in time by calmed regions. Large pressure fluctuations detectable in the ensemble averaged Kulite data reveal the existence of coherent structures in the boundary layer. Distinct velocity variations inside the boundary layer are amplified when approaching the blade surface. The time-mean momentum thickness values are reduced compared to the steady ones and therefore clarify the potential for a loss reduction due to wake passing effects.
Numerical Study of a Cascade Unsteady Separation Flow
Authors: Hu Zongjun , Zha GeCheng , Lepicovsky J.
Published: November 2008

A CFD solver is developed to solve a 3D, unsteady, compressible Navier-Stokes equations with the Baldwin-Lomax turbulence model to study the unsteady separation flow in a high incidence cascade. The second order accuracy is obtained with the dual time stepping technique. The code is first validated for its unsteady simulation capability by calculating a 2D transonic inlet diffuser flow. Then a 3D steady state calculation is carried out for the cascade at an incidence of 10°. The surface pressure distributions compare reasonably well with the experiment measurement. Finally, the 3D unsteady simulation is carried out with 3 inlet Mach numbers at the incidence of 10°. The separation bubble oscillation and the static pressure oscillation on the leading edge of the blade suction surface exhibit clear periodicity. The details of the leading edge vortex shedding is captured. The inlet Mach number is shown to be an important factor to determine the pattern of the separation flow. In the subsonic inlet flow region, increasing the inlet Mach number enlarges the separation region and the pressure oscillation intensity. The separation flow is weakened when the inlet flow becomes supersonic.
Melt-Infiltrated SiC Composites for Gas Turbine Engine Applications
Authors: Morscher Gregory N. , Pujar Vijay V.
Published: November 2008

SiC-SiC ceramic matrix composites (CMCs) manufactured by the melt-infiltration (MI) process are leading candidates for many hot-section turbine engine components. A collaborative program between Goodrich Corporation and NASA-Glenn Research Center is aimed at determining and optimizing woven SiC/SiC CMC performance and reliability. A variety of composites with different fiber types, interphases and matrix composition have been fabricated and evaluated. Particular focus of this program is on the development of interphase systems that will result in improved intermediate temperature stressed-oxidation properties of this composite system. The effect of the different composite variations on composite properties is discussed and, where appropriate, comparisons made to properties that have been generated under NASA’s Ultra Efficient Engine Technology (UEET) Program.
Numerical Prediction of Film Cooling and Heat Transfer With Different Film-Hole Arrangements on the Plane and Squealer Tip of a Gas Turbine Blade
Authors: Yang Huitao , Chen Hamn-Ching , Han Je-Chin
Published: November 2008

The blade tip is one area that experiences high heat transfer due to the strong tip leakage flow. One of the common methods is to apply film cooling on tip to reduce the heat load. To get a better film cooling, different arrangements of film holes on the plane and squealer tips have been numerically studied with the Reynolds stress turbulence model and non-equilibrium wall function. The present study investigated three types of film-hole arrangements: 1) the camber arrangement: the film cooling holes are located on the mid-camber line of tips, 2) the upstream arrangement: the film holes are located upstream of the tip leakage flow and high heat transfer region, and 3) two rows arrangement: the camber and upstream arrangements are combined under the same amount of coolant. In addition, three different blowing ratios (M = 0.5, 1 and 1.5), are evaluated for film cooling effectiveness and heat transfer coefficient. The predicted heat transfer coefficients are in good agreement with the experimental data, but the film cooling effectiveness is over predicted on the blade tips.
Soft Computing Application for Gas Path Fault Isolation
Authors: Ganguli Ranjan , Verma Rajeev , Roy Niranjan
Published: November 2008

A fuzzy system that automatically develops its rule base from a linearized performance model of the engine by selecting the membership functions and number of fuzzy sets is developed in this study to perform gas turbine fault isolation. The faults modeled are module faults in five modules: fan, low pressure compressor, high pressure compressor, high pressure turbine and low pressure turbine. The measurements used are deviations in exhaust gas temperature, low rotor speed, high rotor speed and fuel flow from a base line ‘good engine’. A genetic algorithm is used to tune the fuzzy sets to maximize fault isolation success rate. A novel scheme is developed which optimizes the fuzzy system using very few design variables and therefore is computationally efficient. Results with simulated data show that genetic fuzzy system isolates faults with accuracy greater than that of a manually developed fuzzy system developed by the authors. Furthermore, the genetic fuzzy system allows rapid development of the rule base if the fault signatures and measurement uncertainties change. In addition, the genetic fuzzy system reduces the human effort needed in the trial and error process used to design the fuzzy system and makes the development of such a system easier and faster. A radial basis neural network is also used to preprocess the measurements before fault isolation. The radial basis network shows significant noise reduction and when combined with the genetic fuzzy system leads to a diagnostic system that is highly robust to the presence of noise in data.
Centenary of the First Gas Turbine to Give Net Power Output: A Tribute to Ægidius Elling
Authors: Bakken Lars E. , Jordal Kristin , Syverud Elisabet , Veer Timot
Published: November 2008

The paper presents the work of the Norwegian engineer Ægidius Elling (ref. Figure 1), from his gas turbine patent in 1884 to the first gas turbine in the world producing net power in 1903. It traces the subsequent patents, until his final experiments in 1932. Focus is placed on an engineer with a clear vision of the potential of the gas turbine engine and the capability to realize his ideas, in spite of the lack of industrial financial support. In 1903, Elling noted in his diary that he thought he had built and operated the first gas turbine that could give net power delivery. The power delivery of this very first gas turbine was extracted as compressed air. The net power delivery was modest, only the equivalent of 11 hp. The reason for producing air was the accelerating use of pneumatic tools. Refinements to the gas turbine design soon followed, such as water injection for compressor cooling and recuperation of exhaust gas heat. In 1904, the power output of Elling’s gas turbine had increased to 44 hp. Elling also abandoned the production of compressed air in favor of electric power generation. In a patent from 1923, Elling described a multi-shaft engine with intercooling and reheat, with an independent power turbine. He improved this gas turbine in the period up to 1932, when the engine reached a power output of approximately 75 hp. In 1933, Elling wrote prophetically, “When I started to work on the gas turbine in 1882 it was for the sake of aeronautics and I firmly believe that aeronautics is still waiting for the gas turbine.” Unfortunately, Elling was never to take part in this development, although he pursued his work on the gas turbine until his death in 1949.
On the Economics of the Use of Biomass Fuels in Gas Turbine Cycles: Gasification vs. Externally Firing
Authors: Ferreira Sandro Barros , Pilidis Pericles
Published: November 2008

The use of biomass as gas turbine combined cycle fuels is broadly seen as one of the alternatives to diminish greenhouse gas emissions, mainly CO2, due to the efficiency delivered by such systems and the renewable characteristic of biomass itself. Integrated gasification cycles, BIGGT, are the current technology available; however the gasification system severely penalizes the power plant in terms of efficiency and demands modifications in the engine to accommodate the large fuel mass flow. This gives an opportunity to improvements in the current technologies and implementation of new ones. This paper intends to analyze new alternatives to the use of solid fuels in gas turbines, from the economical point of view, through the use of external combustion, EFGT, discussing its advantages and limitations over the current technology. The results show that both EFGT and BIGGT technologies are economically competitive with the current natural gas fired gas turbines. However, BIGGT power plants are still in pilot scale and the EFGT plants need further technological development. Thermodynamically speaking, the inherently recuperative characteristic of the EFGT gas turbine engine makes it well suited to the biomass market. The thermal efficiency of this cycle is higher than the BIGGT system. Furthermore, its fuel flexibility and negligible pre-treatmet is another advantage that makes it an interesting option for the Brazilian market.
Optimizing the Architecture of Civil Turbofan Engines to Improve Life Cycle Costs/Value Added
Authors: Foerstemann Marc , Staudacher Stephan
Published: November 2008

In this paper, an economic calculation model is described, which evaluates the “life cycle value added” of an aircraft and an aircraft engine from the end customers’ — the airlines’ — perspective. The model uses both revenue as well as total costs over the entire product life cycle. It can be used to assess the economic benefit of a certain product (e.g., aircraft or engine), of a defined improvement measure or of different design options. Based on a complex set of parameters, the model can even be used in early design phases, where the potential impact on life cycle cost is the highest. The model is used to show that existing turbofan engines can be improved to deliver extra value for the end customer and as such for the entire value chain. Specific fuel consumption, manufacturing costs, maintenance costs, weight, drag and development costs are the most significant engine parameters for influencing the life cycle value added. An existing modern two-spool high bypass ratio engine was selected as the baseline configuration for applying the model. An analysis of the engine’s architecture identified the engine’s booster as a potential area of improvement. Upgrading the high-pressure compressor to the latest technology would enable the overall pressure ratio to be maintained while omitting the booster and improving engine performance. The results of the calculation show an improvement of life cycle value added, despite significant one-off development, testing and certification costs. The results support the hypothesis that today’s turbofan engines provide room for life cycle costs/value added improvement.
A Review of Gas Turbine Online Washing Systems
Authors: Mund Friederike C. , Pilidis Pericles
Published: November 2008

The power and efficiency of gas turbines heavily depends on the state of the compressor. Being exposed to atmospheric conditions and pollution, fouling degrades the compressor in terms of the airflow passing and efficiency. Modern online compressor washing techniques prevent a large build up of debris by injecting washing fluid upstream of the compressor. For a satisfactory power recovery, washing methods and schemes have to be carefully adapted to the engine geometry, atmospheric and operating conditions. Therefore, the achievement of a universal cleaning procedure seems to be unlikely and only few general requirements and guidelines concerning compressor washing are available. There also is a variety of different washing systems in existence. These are either provided by the gas turbine manufacturer along with the gas turbine itself or designed by system suppliers as a retrofit for gas turbines of all makes. Based on a literature review and a patent search, a historical review of online washing systems was carried out. Different approaches and cleaning philosophies became apparent. The main influencing factors for the design of washing systems were summarized and basic categories of systems were elaborated to characterize the state-of-the-art in compressor washing equipment. A survey of installations and washing procedures used by European power plants and recommendations by major gas turbine manufacturers and system suppliers for retrofits complemented the existing data sets from the literature. The field data supported the introduced categories for online washing systems. In particular, the air/fluid ratio was shown to be a significant parameter to describe a washing system.
Plasma Actuator for Wake Flow Control of High Camber Blades During Part Load Operation
Authors: Van Dyken Robert , Perez-Blanco Horacio , Byerley Aaron , McLaughlin Tom
Published: November 2008

Plasma actuators, composed of two electrodes with a constant or time-varying voltage difference applied between them are known to impart a directed momentum on the gas in the vicinity of one of the electrodes. This work focuses on a plasma actuator installed on one blade of a gas turbine blade cascade. These high-camber angle blades are used for transportation and stationary applications, and at partial load (i.e. low flow speeds) they exhibit flow separation on the suction side. A plasma actuator, optimized in terms of insulation thickness and applied voltage waveform, is placed on the suction-side, near the trailing edge of the blade, and airfoil plasma-off performance compared to plasma-on. Separation is detected via surface pressure measurements, and loss of stagnation pressure via measurements of total pressure with Pitot tubes. Flow directions are measured in a few cases as well. The actuator is found to decrease the stagnation pressure loss at most experimental conditions, and to increase the flow turning angle. Conclusions as to the plasma actuator effectiveness are derived from blade loss coefficients. The plasma actuator can reduce stagnation pressure losses by 50% with the most effective actuator of those investigated thus far in this cascade. An approximate ratio of electrical to dynamic forces is defined and calculated as a means of characterizing the relative magnitude of the plasma force required to avert separation. Since the loss is measured in the wake of the blade, the term “wake filling configuration” seems an appropriate description of this specific actuator location.
Lean Premixed Combustion of Methane and Hydrogen-Enriched Methane Using Porous Inert Media
Authors: Alavandi S. K. , Agrawal A. K.
Published: November 2008

This paper presents an experimental investigation on lean premixed combustion of methane and hydrogen-enriched methane. The combustion was stabilized on the surface of a porous inert media made of silicon-carbide coated carbon core with 4 pores per centimeter. Experiments were conducted using commercial grade methane (99% purity) and a mixture of 70% methane and 30% hydrogen, by volume. Measurements of NOx and CO emissions were taken for a range of airflow rates and adiabatic flame temperatures. The combustor turndown ratio was varied by a factor of 6. Emission characteristics were compared for a given adiabatic flame temperature, representing energy input to the combustor. Results show lower CO emissions and extended lean blow off limit when hydrogen was added to the methane fuel.
Cooling the Tip of a Turbine Blade Using Pressure Side Holes: Part 1 — Adiabatic Effectiveness Measurements
Authors: Christophel J. R. , Thole K. A. , Cunha F. J.
Published: November 2008

Sealing and durability for turbine blade tips have been challenging problems since the development of gas turbine engines. Blade tip designs are extremely important in terms of sealing and engine performance. In general, overall engine performance can be improved by increasing turbine inlet temperatures. As a result, cooling methods along the blade tip need to be devised and applied effectively. Film-cooling is typically used as a blade tip cooling method, whereby coolant is supplied through holes placed along the pressure side of a blade. Experiments were conducted in a linear cascade with a scaled-up turbine blade whereby the Reynolds number of the engine was matched. A range of blowing ratios was studied whereby coolant was injected from holes placed along the pressure side tip of the blade as well as from dirt purge holes placed on the blade tip. This paper, which is Part 1 of a two part series, compares adiabatic effectiveness levels measured along a blade tip, while Part 2 combines measured heat transfer coefficients with the adiabatic effectiveness levels to assess the overall cooling benefit of pressure side blowing near a blade tip. The results show better cooling can be achieved for a small tip gap compared with a large tip gap with different flow phenomena occurring for each tip gap setting.
Gas Turbine Engine Durability Impacts of High Fuel-Air Ratio Combustors: Near Wall Reaction Effects on Film-Cooled Backward-Facing Step Heat Transfer
Authors: Milanes David W. , Kirk Daniel R. , Fidkowski Krzysztof J. , Waitz Ian A.
Published: November 2008

As commercial and military aircraft engines approach higher total temperatures and increasing overall fuel-to-air ratios, the potential for significant chemical reactions to occur downstream of the combustor is increased. This may take place when partially-reacted species leave the combustor and encounter film-cooled surfaces. One common feature on turbine endwalls is a step between various engine components and seals. Such step features produce recirculating flows which when in the vicinity of film-cooled surfaces may lead to particularly severe reaction zones due to long fluid residence times. The objective of this paper is to study and quantify the surface heat transfer implications of such reacting regions. A shock tube experiment was employed to generate short duration, high temperature (1000–2800K) and pressure (6 atm.) flows over a film-cooled backward-facing step. The test article contained two sets of 35° film cooling holes located downstream of a step. The film-cooling holes could be supplied with different gases, one side using air and the other nitrogen allowing for simultaneous testing of reacting and inert cooling gases. A mixture of ethylene and argon provided a fuel rich freestream that reacted with the air film resulting in near wall reactions. The relative increase in surface heat flux due to near wall reactions was investigated over a range of fuel levels, momentum blowing ratios (0.5–2.0), and Damko¨hler numbers (ratio of characteristic flow time to chemical time) from near zero to 30. The experimental results show that for conditions relevant for future engine technology, adiabatic flame temperatures can be approached along the wall downstream of the step leading to potentially significant increases in surface heat flux. A computational study was also performed to investigate the effects of cooling-jet blowing ratio on chemical reactions behind the film-cooled step. The blowing ratio was found to be an important parameter governing the flow structure behind the backward-facing step, and controlling the characteristics of chemical-reactions by altering the local equivalence ratio.
Heat Transfer in Two-Pass Rotating Rectangular Channels (AR=1:2 and AR=1:4) With 45° Angled Rib Turbulators
Authors: Fu Wen-Lung , Wright Lesley M. , Han Je-Chin
Published: November 2008

This paper reports the heat transfer coefficients in two-pass rotating rectangular channels (AR=1:2 and AR=1:4) with rib roughened walls. Rib turbulators are placed on the leading and trailing walls of the two-pass channel at an angle of 45° to the flow direction. Four Reynolds numbers are considered from 5000 to 40000. The rotation numbers vary from 0.0 to 0.3. The ribs have a 1.59 by 1.59 mm square cross section. The rib height-to-hydraulic diameter ratios (e/Dh) are 0.094 and 0.078 for AR=1:2 and AR=1:4, respectively. The rib pitch-to-height ratio (P/e) is 10 for both cases, and the inlet coolant-to-wall density ratio (Δρ/ρ) is maintained around 0.115. For each channel, two channel orientation are studied, 90° and 45° with respect to the plane of rotation. The results show that the rotation effect increased the heat transfer on trailing wall in the first pass, but reduced the heat transfer on the leading wall. For AR=1:4, the minimum heat transfer coefficient was 25% of the stationary value. However, the rotation effect reduced the heat transfer difference between the leading and trailing walls in the second pass.
Flow Analysis on a Single-Stage Axial Compressor With a Splitter Rotor
Authors: Li Haipeng , Zou Zhengping , Liu Huoxing
Published: November 2008

Unsteady and time-averaged flow fields of a single-stage axial compressor with a splitter rotor working in design conditions are simulated and analyzed with 3-D unsteady CFD code. The results show that strong unsteady flow exists in the rotor passage. Splitter reconstructs the pressure distribution in the rotor passage, changes load distribution of the rotor, and controls the flow near the rotor-blade. Splitter affects the unsteady static pressure distribution and fluctuation on principle blade, splitter and stator.
Innovative Manufacturing Process of MGC Components for Ultra-High Efficiency Gas Turbine Systems
Authors: Waku Yoshiharu , Nakagawa Narihito , Kobayashi Kenji , Kinoshita Yasuhiro , Yokoi Shinya
Published: November 2008

Much attention has been paid to unidirectionally solidified ceramic composites as candidates for high-temperature structural materials. Eutectic composites, known as Melt Growth Composites (MGCs), have recently been developed. The binary MGCs (Al2O3/YAG and Al2O3/GAP binary systems) have a novel microstructure, in which continuous networks of single-crystal Al2O3 phases and single crystal oxide compounds (YAG or GAP) interpenetrate without grain boundaries. Therefore, the MGCs have excellent high temperature strength characteristics, creep resistance, superior oxidation resistance and thermal stability in the air atmosphere at very high temperatures. Manufacturing processes for the MGCs are being examined under a Japanese national project, scheduled from 2001–2005. To achieve higher thermal efficiency for gas turbine systems, uncooled turbine nozzle vanes have been fabricated on an experimental basis. Novel manufacturing processes for MGC gas turbine components are proposed.
Flow With Shock Waves in a Transonic Centrifugal Compressor With a Low-Solidity Cascade Diffuser Using PIV
Authors: Hayami Hiroshi , Hojo Masahiro , Hirata Norifumi , Aramaki Shinichiro
Published: November 2008

A single-stage transonic centrifugal compressor with a pressure ratio greater than six was tested in a closed loop with HFC134a gas. Flow at the inducer of a rotating impeller as well as flow in a stationary low-solidity cascade diffuser was measured using a double-pulse and double-frame particle image velocimetry (PIV). Shock waves in both flows were clearly observed. The effect of flow rate on a 3D configuration of shock wave at the inducer and a so-called rotor-stator interaction between a rotating impeller and a stationary cascade were discussed based on a phase-averaged measurement technique. Furthermore, the unsteadiness of inducer shock wave and the flow in a cascade diffuser during surge were discussed based on instantaneous velocity vector maps.
Gas Turbine Combustor With Integrated Ash Removal for Fine Particulates
Authors: Syred Caroline , Griffiths Anthony , Syred Nick
Published: November 2008

This paper examines the performance of a novel design of combustor for utilising variable calorific value fuel gases as produced by many biomass gasification processes. An integral ash removal system is incorporated into the combustor to reduce the need for subsequent hot gas or other cleanup systems. The combustor is of cyclonic design with tangential inlets for air, start-up fuel and gasification products. Flame stability for low calorific value gases can be enhanced via the use of ceramic/refractory lined sections if required, with the system operating under lean combustion at all times to minimise NOx. Pressure drop of the cyclonic system is minimised by the use of a tangential outlet, as are combustion instabilities, as large central recirculation zones are avoided and associated instabilities like the precessing vortex core. Ash removal from the system is important to minimise damage to turbine components. Two regions are used for particle removal. The first is the base of the unit of a conventional hopper design, and the other, a unique vortex collector pocket (VCP) carefully positioned by the tangential off-take to take advantage of the accelerating tangential flow into the off-take. This paper focuses on the use of CFD to optimise the combustion performance of the combustor run under different operating conditions as well as the removal of coarse and fine material from the flow.
Unsteady Flow Around Suction Elbow and Inlet Guide Vanes in a Centrifugal Compressor
Authors: Cui Michael M.
Published: November 2008

A suction elbow and inlet guide vanes (IGVs) are typical upstream components in the front of the first-stage impeller in a centrifugal compressor. Since the flow field in the front of the impeller is subsonic, the flow motion induced by the rotating impeller interacts with the elbow and IGVs. These interactions induce turbulent unsteady flows inside compressors. The resulted unsteadiness affects efficiency, vibration, and noise generation of the compressor. To understand the mechanism controlling the interactions between up-steam components and to optimize the compressor design for better efficiency and reliability, the turbulent unsteady flow inside the first-stage of the compressor was simulated. The model includes the suction elbow, inlet guide vane housing, and first-stage impeller. HFC 134a was used as the working fluid. The thermodynamic and transport properties of the refrigerant gas were modeled by the Martin-Hou equation of state and power laws, respectively. The three-dimensional unsteady flow field was numerically simulated. The overall performance parameters were obtained by integrating the field quantities. The force, torque, and the arm of moments acting on the IGVs are then calculated. The results can be used to improve centrifugal compressor design to achieve higher efficiency and improve reliability.
Study of a Gas Turbine Combustion Chamber: Influence of the Mixing on the Flame Dynamics
Authors: Duwig Christophe , Fuchs Laszlo
Published: November 2008

The new challenge of the Gas Turbine industry is to develop new technologies for meeting electricity demand growth and reducing harmful emissions. Thus a better understanding of the combustion phenomenon and an improvement in simulation capabilities are needed. Large Eddy Simulation tools brought the hope of meeting these two conditions and enabling the design of safe and clean burners. In the present paper, the influence of the unsteady mixing on the flame in a Lean Premixed Pre-vaporized combustor have been investigated. A premixed combustion flamelet model has been extended to non-uniform fuel/air mixtures cases. Extra terms in the equations, their effects and the modeling issues are discussed. Additionally, the effects of mixing on the flow field in an industrial gas turbine combustion chamber have been investigated. The mean flow field has been found to be weakly sensitive to the mixing effects. It is deduced that the modeling of the mixing and the combustion can be decoupled in the RANS framework. Regarding the flame dynamics, all runs show similar characteristic frequencies. However, different details of models lead to differences in the temperature fluctuations. This suggests that a rigorous modeling of the thermo-acoustic sources (e.g. heat-release fluctuations) requires accurate modeling of the mixing/combustion coupling, for handling accurately the dynamics of the flame.
Experimental and Computational Investigation of Heat Transfer Effectiveness and Pressure Distribution of a Shrouded Blade Tip Section
Authors: Nirmalan Nirm V. , Bailey Jeremy C. , Braaten Mark E.
Published: November 2008

An experimental and computational investigation was conducted to study the detailed distribution of heat transfer effectiveness and pressure on an attached tip-shroud of a turbine blade. Temperatures and pressures were measured on the airfoil-side and gap-side surfaces of the shrouded tip in a three-airfoil stationary cascade. The instrumented center airfoil and the two slave airfoils modeled the aerodynamic tip section of a blade and have the capability to vary tip clearance. The experiments were run at gaps varying of 0.25% to 1.67% of blade span and at an airfoil exit Reynolds number of 1.26×106 and Mach number of 0.95. The effect of coolant flow through the radial-cooled airfoil was also studied. The experimental results are compared with a computational model using the commercially available code, CFX. This unique study presents the influence of gap and coolant flow on the pressure distribution and heat transfer effectiveness of an attached tip-shroud surface.
Comparing Different Solutions for the Micro-Gas Turbine Combustor
Authors: Cameretti Maria Cristina , Tuccillo Raffaele
Published: November 2008

This paper compares different types of combustion chambers for a micro-gas turbine which operates with both different fuels and variations in the inlet air conditions. The combustor types examined cover a wide variety of conditions for the primary combustion, whose fuel/air equivalence ratio ranges from typical lean-premixed levels up to dramatically rich values. The latter is attained in a combustion chamber of the RQL type, while the lean mixture burns in a tubular swirled combustor also equipped with a pilot igniter. The comparison is completed by including an annular combustor with a primary diffusive burner. The CFD based analysis highlights the main differences among the three types of combustors, in terms of temperature and pollutant distributions, and by focusing the attention on the self-ignition occurrence.
CO Emission and Combustion Dynamics Near Lean-Blowout in Gas Turbine Engines
Authors: Menon S.
Published: November 2008

Lean-Blowout (LBO) is a phenomenon that occurs in both land-based premixed and propulsion liquid-fuelled gas turbine engines when the effective equivalence ratio is reduced close to the lean flammability limit. Small perturbations in the flame or flow can result in local quenching that can subsequently lead to total extinction (LBO). Prediction of pollutant emission (e.g., CO) and combustion dynamics near LBO is very complicated since physics at many interacting scales have to be resolved. Here, LES studies of both premixed and liquid-fuelled gas turbine engines are reported using a subgrid linear-eddy mixing (LEM) model. In the premixed study, comparison is made with a thin-flame model and it is shown that the flame length can be changed by adjusting the parameters in this model, whereas the flame length is actually predicted in the LEMLES approach. Results of spray combustion in a full-scale liquid-fuelled gas turbine are also discussed for startup and full power operations. It is shown that the LEMLES is able to anchor the flame at the proper location without requiring any model adjustment.
On Fields Synergism and Convective Heat Transfer Enhancement and Control in Centrifugal Force Field
Authors: Ji Honghu
Published: November 2008

In this article the mathematical expression of field synergy theory for three-dimensional flow with centrifugal force was derived by integrating the energy equation in the concerned volume. This expression contains the terms of dot product of velocity vector U and temperature gradient ∇T, and the dot product of U and the pressure gradient ∇P. This means that heat transfer is not only related to the magnitude of U, ∇T and ∇P, but also related to their directions. To augment and control heat transfer, the effort is directed to understand the synergetic relation among the fields of velocity, temperature and pressure. Theoretical analysis shows that the patterns of these fields can be adjusted by means of changing the boundary condition of inlet and outlet of the system. This method was verified by numerically calculation of three disk cavity flows.