bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Predictions From Conjugate Heat Transfer Analysis of a Film-Cooled Turbine Vane to Experimental Data
Authors: Ni Ron-Ho , Humber William , Fan George , Clark John P. , Anthony Richard J. , Johnson Jamie J.
Published: November 2013

Conjugate heat transfer analysis was conducted on a 648 hole film cooled turbine vane using Code Leo and compared to experimental results obtained at the Air Force Research Laboratory Turbine Research Facility. An unstructured mesh with fully resolved film holes for both fluid and solid domains was used to conduct the conjugate heat transfer simulation on a desktop PC with eight cores. Initial heat flux and surface metal temperature predictions showed reasonable agreement with heat flux measurements but under prediction of surface metal temperature values. Root cause analysis was performed, leading to two refinements. First, a thermal barrier coating layer was introduced into the analysis to account for the insulating properties of the Kapton layer used for the heat flux gauges. Second, inlet boundary conditions were updated to more accurately reflect rig measurement conditions. The resulting surface metal temperature predictions showed excellent agreement relative to measured results (+/− 5 degrees K).
Development of Nondestructive Testing Method for Examining Thermal Resistance of Thermal Barrier Coatings on Gas Turbine Blades
Authors: Ozeki Takayuki , Fujii Tomoharu , Sakai Eiji , Fukuchi Tetsuo , Fuse Norikazu
Published: November 2013

In order to improve the efficiency of electric power generation with gas turbines, the turbine inlet gas temperature needs to be increased. Hence, it is necessary to apply thermal barrier coatings (TBCs) to various hot gas path components. Although TBCs protect the substrate of hot gas path components from high-temperature gas, their thermal resistance degrades over time because of erosion and sintering of the topcoat. When the thermal resistance of TBCs degrades, the surface temperature of the substrate becomes higher, and this temperature increase affects the durability of the hot gas path components. Therefore, to understand the performance of serviced TBCs, the thermal resistance of TBCs needs to be examined by the nondestructive testing (NDT) method. This method has already been reported for TBCs applied to a combustion liner. However, recently, TBCs have been applied to gas turbine blades that have complex three-dimensional shapes, and therefore, an NDT method for examining the thermal resistance of TBCs on blades was developed. This method is based on active thermography using carbon dioxide laser heating and surface temperature measurement of the topcoat by using an infrared camera. The thermal resistance of TBCs is calculated from the topcoat surface temperature when the laser beam heats the surface. In this study, the developed method was applied to a cylindrical TBC sample that simulated curvature on the suction side of a blade, and the results showed the appropriate laser heating condition for this method. Under the appropriate condition, this method could also examine the thermal resistance of TBCs present at 70% of the height of the blade. With these results, this method could determine the thermal resistance within an error range of 4%, as compared to destructive testing.
Effect of Channel Orientation in a Rotating Smooth Wedge-Shaped Cooling Channel With Lateral Ejection
Authors: Qiu Lu , Deng Hongwu , Tao Zhi
Published: November 2013

The effect of channel orientation on heat transfer in a rotating wedge-shaped cooling channel is experimentally investigated in current work. In order to perform a fundamental research, all turbulators are removed away. The classical copper plate technique is employed to measure the regional averaged heater transfer coefficients. The inlet Reynolds number and rotational speed range from 5100 to 21000 and zero to 1000rpm respectively, which results in the inlet Rotation number varies from zero to 0.68. In order to study the effect of channel orientation, five different angles are selected in current study. Furthermore, details such as local bulk temperature calculation and local mass flow rate determination are discussed in current paper. Interestingly, a two-dimensional bulk temperature distribution is observed.

Due to the experimental results, the most evident rotation effect on heat transfer happens in 90° configuration. Compared to the non-rotating condition, there is about 35% overall heat transfer enhancement under highest rotation number. However, the greatest leading-to-trailing heat transfer difference happens in 135° or 112.5° configuration which depends on Rotation number. The highest difference is up to 40%. Besides, at the realistic 135° channel orientation, a critical Rotation number is observed after which the decreasing trend of heat transfer is traversed. The inlet Rotation is better than local one to describe this critical point. With the inlet parameter, the critical Rotation number is about 0.3 at all the locations in this channel.
Ignition and Flame Stabilization of a Premixed Jet in Hot Cross Flow
Authors: Schmitt Denise , Kolb Michael , Weinzierl Johannes , Hirsch Christoph , Sattelmayer Thomas
Published: November 2013

At the Institute of Thermodynamics, Technical University of Munich a large scale atmospheric combustion test rig has been designed and set up. The experimental setup is comprised of two burning zones: A first zone consists of 16 burners providing vitiated air at 1776K, into which a secondary fuel-air mixture jet is injected and ignited by the hot cross flow. The phenomenon is known in the literature as a reacting jet in hot cross flow. The hot data is compared to the cold case in order to show differences in the flow field due to flame propagation.

For evaluating the flow field several experimental analyses have been applied so far (OH*, High-Speed PIV, Mixture Analysis). The focus of this paper is on the momentum ratios J = 4–10 with Jet Reynolds Numbers between 20,000 and 80,000. For the cold case the flow field is measured and compared with the reacting jet. In the injector the air and the natural gas are perfectly premixed. The equivalence ratio of the jet is varied over a wide range of mixtures (ϕ = 0.05–0.77) resulting in an adiabatic flame temperature of the jet between 800 and 2200K. As the pictures of the chemiluminescence analysis show the jet gas ignites immediately upon entering the hot cross flow. The distinct influence of the equivalence ratio on the flame length and shape can be seen in the data. The trajectory of the flame penetrates further into the channel compared to the trajectory of the cold case caused by the reaction in the flame and its resulting gas expansion. Due to the large diameter of the jet in the experiment the origins of the dominant flow patterns are obtained with high spatial resolution. Following this, flame anchoring mechanisms at different operation points are derived.
Effect of Nanosecond Repetitively Pulsed Discharges on the Dynamics of a Swirl-Stabilized Lean Premixed Flame
Authors: Lacoste D. A. , Moeck J. P. , Durox D. , Laux C. O. , Schuller T.
Published: November 2013

The effects of Nanosecond Repetitively Pulsed (NRP) plasma discharges on the dynamics of a swirl-stabilized lean premixed flame are investigated experimentally. Voltage pulses of 8-kV amplitude and 10-ns duration are applied at a repetition rate of 30 kHz. The average electric power deposited by the plasma is limited to 40 W, corresponding to less than 1 % of the thermal power of 4 kW released by the flame. The investigation is carried out with a dedicated experimental setup that allows for studies of the flame dynamics with applied plasma discharges. A loudspeaker is used to perturb the flame acoustically, and the discharges are generated between a central pin electrode and the rim of the injection tube. Velocity and CH* chemiluminescence signals are used to determine the flame transfer function assuming that plasma discharges do not affect the correlation between CH* emission and heat release rate fluctuations. Phase-locked images of the CH* emission were recorded to assess the effect of the plasma on the oscillation of the flame. The results show a strong influence of the NRP discharges on the flame response to acoustic perturbations, thus opening interesting perspectives for combustion control. An interpretation of the modifications observed in the transfer function of the flame is proposed by taking into account the thermal and chemical effects of the discharges. It is then demonstrated that by applying NRP discharges at unstable conditions, the oscillation amplitudes can be reduced by an order of magnitude, thus effectively stabilizing the system.
A Four Component Skeletal Model for the Analysis of Jet Fuel Surrogate Combustion
Authors: Akih-Kumgeh Ben , Bergthorson Jeffrey M.
Published: November 2013

A skeletal chemical kinetic model for jet fuel combustion, comprising four representative fuel components, is presented. The sub model for the three components, toluene, methyl cyclohexane (MCH) and n-dodecane, is deduced from a detailed model for jet fuel surrogate proposed by Wang et al. [Wang et al., 2010]. The reduction is based on a species sensitivity approach, herein referred to as Alternate Species Elimination (ASE). The sub model for the fourth component, iso-octane, is established through semi-detailed kinetic modeling, considering existing reactions and species of the smaller hydrocarbon systems as well as species and reactions pertinent to the n-dodecane system.

The performance of the resulting model is assessed by comparing predictions of ignition delay times and laminar burning velocities with those of the detailed model. It is shown that the skeletal model retains the predictive ability of the detailed model with respect to the three components, n-dodecane, MCH and toluene. The complementary iso-octane sub model is also found to reasonably predict high-temperature ignition delay times and laminar burning velocities.

The four component skeletal model is tested against shock tube ignition data and laminar burning velocities of jet fuel surrogates. It is observed that high-temperature ignition is fairly well predicted while low-temperature ignition delay times are longer than experimentally observed. While the predictions of laminar burning velocities of atmospheric flames of jet fuels at 400 K are reasonable, slower flames are predicted at higher temperatures. The proposed skeletal model has 192 species and 1291 reactions, compared to the detailed multi-component model, with 348 species and 2163 elementary reactions, albeit without iso-octane. This results in improvement in the associated computational costs for combustion analysis. Further development of the skeletal model is needed to improve its prediction ability over a wider range of combustion properties and thermodynamic conditions.
Study of Fuel Composition, Burner Material and Tip Temperature Effects on Flashback of Enclosed Jet Flame
Authors: Duan Zhixuan , Shaffer Brendan , McDonell Vincent
Published: November 2013

Flashback is a key challenge for low NOx premixed combustion of high hydrogen content fuels. Previous work has systematically investigated the impact of fuel composition on flashback propensity, and noted that burner tip temperature played an important role on flashback, yet did not quantify any specific effect. The present work further investigates the coupling of flashback with burner tip temperature and leads to models for flashback propensity as a function of parameters studied. To achieve this, a jet burner configuration with interchangeable burner materials was developed along with automated flashback detection and rim temperature monitoring. An inline heater provides preheated air up to 810 K. Key observations include that for a given condition, tip temperature of a quartz burner at flashback is higher than that of a stainless burner. As a reasult, the flashback propensity of a quartz tube is about double of that of a stainless tube. A polynomial model based on analysis of variance is presented and shows that, if the tip temperature is introduced as a parameter, better correlations result. A physical model is developed and illustates that the critical velocity gradient is proportional to the laminar flame speed computed using the measured tip temperature. Addition of multiple parameters further refined the prediction of the flashback propensity, and the effects of materials are discussed qualitatively using a simple heat transfer analysis.
Influence of Burner Material, Tip Temperature and Geometrical Flame Configuration on Flashback Propensity of H2-Air Jet Flames
Authors: Duan Zhixuan , Shaffer Brendan , McDonell Vincent , Baumgartner Georg , Sattelmayer Thomas
Published: November 2013

Flashback is a key operability issue for low emission premixed combustion systems operated on high hydrogen content fuels. Previous work investigated fuel composition impacts on flashback propensity and found that burner tip temperature was important in correlating flashback data in premixed jet flames. An enclosure around the jet flame was found to enhance the flame-burner rim interaction. The present study further addresses these issues using a jet burner with various geometric configurations and interchangeable materials. Systematic studies addressing the quantitative influence of various parameters such as tip temperature, burner material, enclosure size, and burner diameter on flashback propensity were carried out. A comprehensive overview of the flashback limits for all conditions tested in the current study as well as those published previously is given. The collective results indicate that the burner materials, tip temperature and flame confinement play significant roles for flashback propensity and thus help explain previous scatter in flashback data. Furthermore, the present work indicates that the upstream flame propagation during flashback is affected by the burner material. The material with lower thermal conductivity yields larger flashback propensity but slower flame regression inside the tube. These observations can be potentially exploited to minimize the negative impacts of flashback in practical applications.
Unsteady Flow Effect on Nonequilibrium Condensation in 3-D Low Pressure Steam Turbine Stages
Authors: Miyake Satoshi , Yamamoto Satoru , Sasao Yasuhiro , Momma Kazuhiro , Miyawaki Toshihiro , Ooyama Hiroharu
Published: November 2013

A numerical study simulating unsteady 3-D wet-steam flows through three-stage stator-rotor blade rows in a low-pressure steam turbine model experimentally conducted by Mitsubishi Heavy Industry (MHI) was presented in the last ASME Turbo Expo by our group. In this study, the previous discussion is extended to the discussion how nonequilibrium condensation is influenced by unsteady wakes and corner vortices from prefaced multi-stage blade rows. Unsteady 3-D flows through three-stage stator-rotor blade rows are simulated assuming nonequilibrium condensation. Flows with a different inlet flow condition are calculated and the results are compared with each other. Instantaneous condensate mass fractions are visualized at different spans and cross sections in the three-stage stator and rotor blade rows. Also the time and space dependent values are plotted and the obtained unsteady flow characteristics are explained.
Influence of Fuel Composition, Engine Power and Operation Mode on Exhaust Gas Particulate Size Distribution and Gaseous Emissions From a Gas Turbine Engine
Authors: Li Hu , Altaher Mohamed A. , Wilson Chris , Blakey Simon , Chung Winson
Published: November 2013

The impact of fuel composition, engine power (idle and full power) and operation mode (cold and hot idle) on the gaseous emissions, particle number and mass concentrations and size distributions from an aircraft auxiliary power unit (APU) was investigated. A re-commissioned Artouste MK113 APU engine was used. The engine was run at three operational modes: i.e. approximately 6 minutes at idle (cold idle) after stabilized from start, 6 minutes at full power and then returning to idle again (hot idle) for 6 minutes. All operating parameters of the engine were monitored and recorded. The engine exhaust particle measurements and gaseous emissions were taken at three operating modes.

Five alternative fuels/blending components were tested and compared to neat conventional JetA1 fuel either in pure or blended forms. These fuels varied in their compositions in terms of H/C ratio, density and other properties. A Scanning Mobility Particle Sizer (SMPS) with a Nano-Differential Mobility Analyzer (NDMA) was used to determine the number and mass concentration and size distribution of engine exhaust in the size range from 5 nm to 160 nm. The influence of fuel elemental ratio (H/C), engine power and cold/hot operation on particle number and mass size distribution was investigated. The results show that there was a good correlation between fuels H/C ratio and particle concentrations, particle size and distributions characteristics. The engine at hot idle produced ∼20% less particles compare to the results at cold idle. The alternative fuel blends produced less particles than JetA1 fuel. The testing fuels produced similar levels of NOx, slight reductions in CO and remarkable reductions in UHC compared to JetA1.
Theoretical Study of a Building Cooling Heating Power (BCHP) System Driven by Solar Energy Based on Organic Working Fluid
Authors: Wang Jiangfeng , Wang Man , Yan Zhequan , Dai Yiping
Published: November 2013

Recently, BCHP systems as a kind of distributed energy resource present a great potential in improving energy efficiency and meeting multiple energy demands. Compared with traditional CCHP systems driven by fossil fuel, on-site renewable energy systems have more advantages in reducing carbon emissions. This paper proposes a new Building Cooling Heating Power system driven by solar energy with flat-plate solar collectors and R245fa as the working fluid. A thermal storage system is integrated into the system to store the collected solar energy and to supply heat when solar radiation is insufficient. By establishing the mathematical models of the proposed system we are able to conduct the numerical simulation of the system working in three typical operation modes around a whole year, namely the Combined Heating Power (CHP) mode in winter, the Combined Cooling Power (CCP) mode in summer, and the power production mode in spring or autumn. Results indicate that the system is able to operate continuously over a day, offering uninterrupted heating, cooling and power to building applications.
Designing Turbochargers With an Integrated Design System
Authors: Qiu Xuwen , Fredriksson Carl F. , Baines Nicholas C. , Backlund Markus
Published: November 2013

One of the more visible tasks when designing a turbocharger is the optimized design for a compressor and a turbine. The ultimate measure of a successful turbocharger design, however, is how well it works with a specific engine at various operating conditions. Final design decisions must be based on the engine-turbocharger system as a whole, rather than only on the individual component performance.

This paper describes the effort to develop an integrated design system which allows the user to design and optimize a turbocharger on a system level. With the basic engine parameters specified, along with simple models for other commonly used components, such as the Exhaust Gas Recirculation (EGR), wastegate, and intercooler, the program may be linked to two powerful meanline programs that can handle the fast iterations of the design and analysis of a compressor and a turbine. The output is either a new compressor or turbine that best matches the operation of the engine or the performance of an existing turbocharger at a specific engine operating condition.

A case study is presented where the program is applied in a real-life design situation to fit a new turbocharger for a large locomotive 18-cylinder diesel engine. The tool is extensively used in guiding the selection of the turbocharger and in the simulation of the overall system performance. The test data from the new design show close agreement with the simulation results, as well as an improvement over the original design.
Study on Dynamic Characteristics of Large Ship Rotor-Bearing System Based on an Advanced Water-Lubricated Rubber Bearing Model
Authors: Zhang Min , Zhang Guanghui , Liu Zhansheng
Published: November 2013

The main point of this study is to propose an advanced model for large length-diameter ratio stern water-lubricated rubber bearing and conduct comparisons with the conventional water-lubricated rubber bearing model. The assumption of the advanced model was to divide the whole stern bearing into 4 sections equidistantly along the axial direction. Among each small section, the water film pressure distribution was solved and water film forces were generated. The dynamic model of the rotor-bearing system was built based on Finite Element Method (FEM) and solved by Newmark Method. It indicated that the predicted shaft centerline locus of the nodes located at the propeller and left water-lubricated rubber bearing rise significantly when using the new water-lubricated rubber bearing model.
Turbine Engine Reconfigurable Control Systems for Aircraft Propulsion Performance Improvement
Authors: Zein-Sabatto Saleh , Behbahani Alireza , Mgaya Richard Hans , Bodruzzaman Mohammad
Published: November 2013

Artificial intelligent technologies are being investigated for development of advanced adaptation and reconfiguration algorithms for turbine engine distributed control systems. Adding adaptation and reconfiguration feature to the control systems is expected to improve engine performance and provide more efficient aircraft operations. The benefits of transitioning from the existing centralized supervisory control, the Full Authority Digital Electronic Control (FADEC), of turbine engines to distributed control architecture have been well articulated in the literature. The major benefits are summarized as; weight reduction, cost saving, and damage tolerant turbine engines. However, consideration of advanced intelligent technologies in the design and operation of distributed control systems has been a challenging task and requires further investigation. This paper describes research activities to address the above stated challenge leading to fully reconfigurable distributed control systems for turbine engines of the future aircrafts. The goal of the research work is to accelerate the development and implementation of disturbed control systems in aircrafts propulsion controls and its integration with distributed diagnostics and prognostics algorithms. This will be achieved by means of using artificial intelligent technologies to design adaptation and reconfiguration algorithms and integrate it with a set of engine decentralized controllers. Fuzzy inference concept will be used to develop and implement the proposed adaptation and reconfiguration algorithms. Finally, the integrated reconfiguration algorithms with the control system will be tested and verified on publicly available turbine engine simulation software.
An Energy-Based Method for Predicting the Additive Effect of Multiple Film Cooling Rows
Authors: Kirollos Benjamin , Povey Thomas
Published: November 2013

There have been numerous studies reporting film effectiveness for film rows in isolation, which have led to correlations which are used for preliminary design. Many applications require multiple film cooling rows. Although there is some published data which deals with the combined effect of multiple rows, in most design situations the additive effect is computed using correlations for single rows. The most widely used method is the Sellers superposition method. In many applications the method gives accurate results. Although the method is to some extent physically based, energy is not conserved within the model, and in certain situations this limitation can be shown to lead to an under-prediction of the film effectiveness.

In this paper, a new energy-based method for predicting the additive effect of multiple film cooling rows is outlined. The physical basis and limitations of the model are discussed. Predictions conducted using the new method are compared with CFD data and contrasted with the Sellers method. In situations where energy conservation is required to avoid under-prediction of effectiveness the method is shown to be advantageous.
Numerical Analysis of the Conceptual Design of Arrayed-Vanes Premixer for Gas Turbine Combustors Burning High-Hydrogen Fuels
Authors: Yu Zongming , Wu Xinnan , Wu Feifan , Wang Yue , Kong Wenjun , Feng Yongzhi , Wang Hui
Published: November 2013

Using high-hydrogen fuels in industrial gas turbines is an effective way to achieve near-zero carbon emission power generation. Lean premixed combustion can effectively reduce NOx emission. However, due to the strong flashback and auto-ignition tendencies during fuel-air mixing, it is a challenge to use lean premix combustion mode of high hydrogen fuels under gas turbine operation conditions.

An innovative conceptual design of arrayed-vanes premixer was proposed to achieve safe and uniform mixing of fuel and air. Inside the arrayed-vanes premixer, a cascade of mixing vanes is arranged in the axial annular air flow passage. Fuel-air mixing and flow field stretch are improved and well controlled by the arrayed vanes. The conditions of auto-ignition and flame stabilization inside the vanes are unsatisfied. Meanwhile the upstream flow disturbance will be inhibited by the arrayed vanes, which benefits combustion stability.

The arrayed-vanes premixer was designed and its flow field was numerically simulated under the operation condition of F class gas turbine combustors. The flow and fuel-air mixing behavior was analyzed and compared with a typical swirl-based premixer now widely used in DLN combustors of F class gas turbines. The results show that the non-uniformity index of fuel concentration distribution at the exit plane of the arrayed-vanes premixer is 50% lower than that of the swirl-based premixer.

The responses of flow field at the exit plane to the inlet flow disturbance was calculated and compared for the two types of permixer. The inlet flow disturbance includes the velocity distortion and the oscillation of the pressure. The results show that the arrayed-vanes premixer absorbs and damps the inlet flow disturbance better than the swirl-based premixer. And it exhibits highly monochromatic characteristic through the acoustic signature analysis.

Furthermore, the tendencies of auto-ignition and flashback were investigated by examining the flow field and the flammability of hydrogen. The results show that there is a low risk of auto-ignition or flashback due to the short residence time and the high discharge velocity.

The present study indicates that the arrayed-vanes premixer achieves ultra uniform fuel-air mixing, good adaptability to inlet flow disturbance and anti auto-ignition and flash back, which is benefit to DLN combustor designed for high-hydrogen fuels. This design will be possibly used in DLN combustors after future developments.
Preliminary Calculations on Post Combustion Carbon Capture From Gas Turbines With Flue Gas Recycle
Authors: Akram Muhammad , Khandelwal Bhupendra , Blakey Simon , Wilson Christopher W.
Published: November 2013

Carbon capture is getting increased attention recently due to the fact that it seems to be the only answer to decrease emissions. Gas turbines exhaust have 3–5 % concentration of CO2 which is very low to be captured by an amine carbon capture plant effectively. The amine based plants are most effective at around 10 – 15% CO2 in the flue gas. In order to increase the concentration of CO2 in the exhaust of the gas turbine, part of the exhaust gas needs to be recycled back to the air inlet. On reaching the concentration of CO2 around 10% it can be fed to the amine capture plant for effective carbon capture.

A 100 kWe (plus 150 kW hot water) CHP gas turbine Turbec T100 is installed at the Low Carbon Combustion Centre of the University of Sheffield. The turbine set up will be modified to make it CO2 capture ready. The exhaust gases obtained will be piped to amine capture plant for testing capture efficiency. Preliminary calculations have been done and presented in this paper. The thermodynamic properties of CO2 are different from nitrogen and will have an effect on compressor, combustor and turbine performance. Preliminary calculations of recycle ratios and other performance based parameters have been presented in this paper. This paper also covers the aspects of turbine set up machinery which needs to be modified and what kind of modifications may be needed.
Using a Lubrication Test Bench for Testing New Oil Quality Sensors
Authors: Berten Olivier , Hendrick Patrick , Villar Alberto , Seveno David
Published: November 2013

The Université Libre de Bruxelles/ Aero-Thermo-Mechanics Department (ULB/ATM) has developed a flow bench used to mimic the complete behaviour of an aircraft gas turbine engine lubrication system.

This test bench has been improved to be fully instrumented and is really multi-purposes in order to test different lubrication devices in the supply circuit (pure oil) or in the scavenge part (two-phase flow) simulating real flight conditions (oil flow rate, oil temperature and pressure…).

The paper will first present the characteristics of the lubrication test bench and its capabilities.

In a second part, it will be presented the integration and the test results of two different types of sensors into the lubrication test bench. One sensor is based on measuring the change in frequency of a quartz crystal resonator. The other one is composed of two optical sensors, which are able to monitor different properties of the oil and also to detect particles in the oil.
A Chemical-Kinetic Investigation of Combustion Properties of Alternative Fuels: A Step Towards More Efficient Power Generation
Authors: Methling Torsten , Braun-Unkhoff Marina , Riedel Uwe
Published: November 2013

Biomass is a clean, renewable energy source with a large potential to contribute significantly to power generation, promising a more environmentally friendly production of electricity in future, with lower greenhouse gas emissions.

A large variety of biomass feedstock exists, including agricultural and biomass residues and by-products, with wood, sludge, and waste among them. Biomass can be used directly to generate electricity if converted to more user-friendly sources of energy, e.g. by fermentation producing mainly methane (biogas) and by gasification leading mostly to hydrogen and carbon monoxide (syngas), allowing a more efficient use of the product gases compared to direct combustion, besides further advantages, with less amounts of ash and corrosive species.

The resulting product gases can be burned in small to large scale gas turbines, stand alone, process integrated or in combined cycles. In a hybrid power plant, an increase of the electrical efficiency of small gas turbines to more than 50 % can be reached, by coupling a gasifier or biogas reactor with a fuel cell (FC) and a micro gas turbine.

To widen the acceptable range in the variation of fuel composition and conditions and to ensure a reliable and more efficient operation, it is of outmost importance to expand our knowledge on biogenic gas mixtures with respect to modeling capabilities e.g. of major combustion properties, thus enabling predictive calculations.

The present work is dealing with the use of representative biogenic gas mixtures for decentralized power production. The concept of coupling a gasifier or biogas reactor with a fuel cell and a micro gas turbine (hybrid power plant) is followed.

The product gases are stemming from the fermentation of sludge and algae as well as from the gasification of their residues and wood, in addition. Their combustion behavior — lower heating value (LHV), Wobbe index, adiabatic flame temperature, laminar flame speed, and ignition delay time — is calculated for the relevant parameters — fuel-air ratio, pressure — and discussed with respect to the intended use.
The Effect of Inlet Guide Vanes on Inlet Flow Distortion Transfer and Transonic Fan Stability
Authors: Shaw M. J. , Hield P. , Tucker P. G.
Published: November 2013

An investigation has been carried out into the effects of variable inlet guide vanes (VIGVs) on the performance and stability margin of a transonic fan in the presence of inlet flow distortion. The study was carried out using computational fluid dynamics (CFD) and validated with experimental data. The capability of CFD to predict the changes in performance with or without VIGVs in the presence of an inlet flow distortion is assessed. Results show that the VIGVs improve the performance and stability margin and do so by reducing the amount of swirl at inlet to the rotor component of the fan.
Endwall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring: Part I — Airfoil Design
Authors: Lyall M. Eric , King Paul I. , Clark John P. , Sondergaard Rolf
Published: November 2013

This paper presents the reasoning for and the design process of contouring a high lift front-loaded low pressure turbine (LPT) airfoil near the endwall to reduce the endwall loss. The test airfoil, L2F, was designed to the approximate gas angles with 38% larger pitchwise spacing than the widely studied Pack B airfoil. Being more front-loaded with a higher stagger angle, L2F is shown to produce more endwall losses than Pack B. It is suggested that the high endwall loss of L2F is due to the high stagger angle, not front-loading as usually suggested in the literature. A procedure is presented to approximate the front-loading and stall resistance of L2F and obtain a low stagger version of that airfoil, designated L2F-LS. A contoured airfoil is then designed by transitioning L2F into L2F-LS at the endwall to obtain a benefit from the reduced stagger angle at the endwall. The contouring process generates a fillet, so the contoured airfoil is referred to as L2F-EF (“Endwall Fillet”). Predictions in this paper suggest endwall loss reductions between 17% and 24% at Re = 100,000. Linear cascade experiments in Part II [1] of this paper indicate that L2F-EF reduces endwall losses more than 20% compared to L2F. The overall conclusion is that the stagger angle has a significant effect on endwall loss and should be considered for designing high lift LPT airfoils at the endwall.
Endwall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring: Part II — Validation
Authors: Sangston Keith , Little Jesse , Lyall M. Eric , Sondergaard Rolf
Published: November 2013

The hypothesis, posed in Part I [1], that excessive endwall loss of high lift low pressure turbine (LPT) airfoils is due to the influence of high stagger angles on the endwall pressure distribution and not front-loading is evaluated in a linear cascade at Re = 100,000 using both experimental and computational studies. A nominally high lift and high stagger angle front-loaded profile (L2F) with aspect ratio 3.5 is contoured at the endwall to reduce the stagger angle while maintaining the front loading. The contouring process effectively generates a fillet at the endwall, so the resulting airfoil is referred to as L2F-EF (Endwall Fillet). Although referred to as a fillet, this profile contouring process is novel in that it is designed to isolate the effect of stagger angle on endwall loss. Total pressure loss measurements downstream of the blade row indicate that the use of the lower stagger angle at the endwall reduces mixed out mass averaged endwall and passage losses approximately 23% and 10% respectively. This is in good agreement with computational results used to design the contour which predict 18% and 7% loss reductions. The endwall flow field of the L2F and L2F-EF models is measured using stereoscopic particle image velocimetry (PIV) in the passage. These data are used to quantify changes in the endwall flow field due to the contouring. PIV results show that this loss reduction is characterized by reduced inlet boundary layer separation as well as a change in strength and location of the suction side horseshoe vortex (SHV) and passage vortex (PV). The endwall profile contouring also produces a reduction in all terms of the Reynolds stress tensor consistent with a decrease in deformation work and overall flow unsteadiness. These results confirm that the stagger angle has a significant effect on high-lift front-loaded LPT endwall loss. Low stagger profiling is successful in reducing endwall loss by limiting the development and migration of the low momentum fluid associated with the SHV and PV interaction.
Time-Resolved Film-Cooling Flows at Low and High Density Ratios
Authors: Eberly Molly K. , Thole Karen A.
Published: November 2013

Film-cooling is one of the most prevalent cooling technologies that is used for gas turbine airfoil surfaces. Numerous studies have been conducted to give the cooling effectiveness over ranges of velocity, density, mass flux, and momentum flux ratios. Few studies have reported flowfield measurements with even fewer of those providing time-resolved flowfields. This paper provides time-averaged and time-resolved particle image velocimetry data for a film-cooling flow at low and high density ratios. A generic film-cooling hole geometry with wide lateral spacing was used for this study, which was a 30° inclined round hole injecting along a flat plate with lateral spacing P/D = 6.7. The jet Reynolds number for flowfield testing varied from 2500 to 7000. The data indicate differences in the flowfield and turbulence characteristics for the same momentum flux ratios at the two density ratios. The time-resolved data indicate Kelvin-Helmholtz breakdown in the jet-to-freestream shear layer.
The Development of a Closed Loop High Speed Cascade Wind Tunnel for Aerodynamic and Heat Transfer Testing at Moderate to Low Reynolds Numbers
Authors: Mihelish M. P. , Ames F. E.
Published: November 2013

Engine companies typically emphasize research which has been conducted at conditions as close to engine conditions as possible. This focus on engine relevant conditions often causes difficulties in University research laboratories. One particularly difficult testing regime is high speed but low Reynolds number flows. High speed low Reynolds number flows can occur in both low pressure turbines under a normal range of engine operating conditions and in high pressure turbines run at very high altitudes. This paper documents a new steady state closed loop wind tunnel facility which has been developed to study high speed cascade flows at low Reynolds numbers. The initial test configuration has been representative of a first stage vane configuration for a UAV turbofan which flies at a very high altitude. The initial test section was configured in a three full passage four-vane linear cascade arrangement with upper and lower bleed flows. Both heat transfer and aerodynamics loss measurements were acquired and are presented in this paper. Heat transfer measurements were taken at a Reynolds number of 720,000 based on true chord and exit conditions at Mach numbers of 0.7, 0.8, and 0.9. Exit survey measurements were conducted at a chord exit Reynolds number of 720,000 over a similar range in Mach numbers. However, this facility has the capability to run at chord Reynolds numbers of 90,000 or below in the present configuration which uses an approximately three times scale test vane.
Coupled Fluid-Thermal-Solid Simulation of Axial Through-Flow Rotating Cavities
Authors: Yi Wei-lin , Zhang Xiao-hang , Ji Lu-cheng , Chen Jiang
Published: November 2013

The rotating cavities of aero-engine compressors are the main part of secondary air flow system. It is known that there are typical multidisciplinary fluid-thermal-solid coupling characteristics in them. The high precision prediction of disc surface temperature is very important for structure designer to select materials, control blade clearances et al. The aim of this paper is to investigate the aerodynamic-thermal simulation model to obtain the method and tool for reliable temperature prediction.

The paper firstly selected publicly available experimental data of two rotating cavity geometries with twin-discs to validate the precision of established fluid-thermal simulation model with the different grids, difference schemes and turbulence models. The results showed that the RNG-KE turbulence model with QUICK scheme has the better simulation precision for flow structure and Nusselt number distribution.

Based on the above research, a fluid-thermal-solid coupling simulation of a twin-cavities model which is approaching to the real conditions of aero-engine has been carried out. The wall temperature distribution on inner surface has been obtained and its maximum error comparing with the experimental value is 8°C. Also the results further validated the reliabilities of the flow model, heat transfer model and fluid-thermal-solid coupling model. The paper also shows the flow field structure of rotating cavity for further understanding the internal flow characteristics.
Cooling of a Honeycomb Shroud Seal in Order to Reduce Oxidation
Authors: Davis A. W. , Dawson A. , Bunn L. , Bonaldo A. , Hill M. , Favaretto C. F. , Backhouse R.
Published: November 2013

As a result of continuous enhancement of the capability of it’s gas turbines, proposed uprated versions the SGT-100 engine were predicted have pre-mature oxidation of the honey-comb seal material above the CT1 blade. This would lead to an increase in over tip leakage and degradation of engine performance. A project to increase the service life of the honeycomb was started and various options considered. Initially a CFD analysis of the region was carried out in order to understand the flow field in the cavity surrounding the HP blade shroud, and hence the source of the high temperatures. Further CFD studies were carried out to assess the effect of applying cooling air into the cavity, and the optimal position to introduce such flow so it had maximum effect on the honeycomb temperatures. Modifications were then carried out to engine components to replicate cooling proposed by the CFD analysis and a series of engine tests with, and without the cooling were carried out. The Shroud temperatures were measured during engine operation by infra-red Pyrometry, which confirmed the effectiveness of the cooling modification.
Optimizing Lifetime Consumption and Increasing Flexibility Using Enhanced Lifetime Assessment Methods With Automated Stress Calculation From Long-Term Operation Data
Authors: Vogt Jan , Schaaf Thomas , Helbig Klaus
Published: November 2013

In the past most of the steam turbines were designed as base load machines. Due to new market requirements based on the effect of renewable energies, power plant operators are forced to operate with more frequent start-up events and load changes, resulting in a fundamental higher low cycle fatigue (LCF) lifetime consumption.

Traditional methods of lifetime assessment often use representative start-ups, for the calculation of LCF damage, which can provide very conservative results with reasonable safety margins. For a high number of starts these safety margins may result in an overestimation of the LCF damage.

At Alstom, an enhanced method for lifetime assessment has been developed, that evaluates the actual lifetime consumption from real operation data in an automated manner and provides much more realistic results.

The operation data is used to calculate the transient temperature distribution and heat transfer coefficients along the rotor for each start-stop cycle. The corresponding stress distribution in the rotor is evaluated by means of a Finite-Element-method analysis.

Finally the number of remaining cycles is extracted for the most critical locations using material data. In combination with the creep damage the lifetime consumption is evaluated. The entire process is highly automated, but also facilitates easy monitoring through the lifetime engineer by graphic presentation of calculation results.

Using this enhanced method of lifetime assessment, the computed lifetime consumption is closer to the actual value, supporting the planning of overhauls and component replacements and minimizing the risk of failure or forced outages.

The utilization of remaining lifetime can be optimized in favour of a more flexible mode of operation (e.g. low load operation and fast start-up) or extension of operational lifetime for conventional and combined cycle power plants.
Study of Microparticle Rebound Characteristics Under High Temperature Conditions
Authors: Reagle C. J. , Delimont J. M. , Ng W. F. , Ekkad S. V.
Published: November 2013

Large amounts of tiny microparticles are ingested into gas turbines over their operating life, resulting in unexpected wear and tear. Knowledge of such microparticle behavior at gas turbine operating temperatures is limited in published literature. In this study, Arizona Road Dust (ARD) is injected into a hot flow field to measure the effects of high temperature and velocity on particle rebound from a polished 304 Stainless Steel (SS) coupon. The results are compared with baseline (27m/s) measurements at ambient (300°K) temperature made in the Virginia Tech Aerothermal Rig, as well as previously published literature. Mean Coefficient of Restitution (COR) was shown to decrease with the increased temperature/velocity conditions in the VT Aerothermal Rig. The effects of increasing temperature and velocity led to a 12% average reduction in COR at 533°K (47m/s), 15% average reduction in COR at 866°K (77m/s), and 16% average reduction in COR at 1073°K (102m/s) compared with ambient results. The decrease in COR appeared to be almost entirely a result of increased velocity that resulted from heating the flow. Trends show that temperature plays a minor role in energy transfer between particle and impact surface below a critical temperature.
Design Considerations for Ceramic Matrix Composite Vanes for High Pressure Turbine Applications
Authors: Boyle Robert J. , Parikh Ankur H. , Halbig Michael C. , Nagpal Vinod K.
Published: November 2013

Issues associated with replacing conventional metallic vanes with Ceramic Matrix Composite(CMC) vanes in the first stage of the High Pressure Turbine(HPT) are explored. CMC materials have higher temperature capability than conventional HPT vanes, and less vane cooling is required. The benefits of less vane coolant are less NOx production and improved vane efficiency. Comparisons between CMC and metal vanes are made at current rotor inlet temperatures and at an vane inlet pressure of 50 atm.. CMC materials have directionally dependent strength characteristics, and vane designs must accommodate these characteristics. The benefits of reduced NOx and improved cycle efficiency obtainable from using CMC vanes. are quantified Results are given for vane shapes made of a two dimensional CMC weave. Stress components due to thermal and pressure loads are shown for all configurations. The effects on stresses of: (1) a rib connecting vane pressure and suction surfaces; (2) variation in wall thickness; and (3) trailing edge region cooling options are discussed. The approach used to obtain vane temperature distributions is discussed. Film cooling and trailing edge ejection were required to avoid excessive vane material temperature gradients. Stresses due to temperature gradients are sometimes compressive in regions where pressure loads result in high tensile stresses.