bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Design of a High Bypass Ratio Turbofan Engine
Authors: Muhammad Hassan Rizvi Syed , Ramsden Kenneth W. , Pachidis Vasslios
Published: February 2010

This paper presents a preliminary design of a high bypass ratio turbofan engine which has been developed through a Masters Degree project at Cranfield University in the UK. It is well known that the design process for a new gas turbine engine requires an understanding of the interrelated requirements of aerodynamics, thermodynamics, heat transfer, materials choice and engine control. Accordingly, the designer’s solution is inevitably the result of compromises involving a large number of mostly conflicting parameters. The preliminary design study in this paper relates to assessment of a suitable engine to satisfy the specification needs of a small airliner. The particular aircraft chosen for the design is one designed by a group of master’s degree students in the College of Aeronautics at Cranfield University. The paper includes a description of that aircraft specification for which the cruise phase is chosen as a design point for the engine. The overall objective of the design is to achieve the least (practical) specific fuel consumption so as to maximize aircraft range. The paper presents the results of the iterative design study and includes the effects of turbine entry temperature, bypass ratio, overall pressure ratio and fan pressure ratio. Subsequently, a procedure for the selection of the annulus geometry for each of the turbomachinery components and the combustor is illustrated which can deliver an acceptable gas path for the entire engine. Finally, using well established compressor cascade data, an approximate method is illustrated for the prediction of the performance characteristic of the high pressure compressor of the core engine.
Combustion Stability and Emissions in a Lean Premixed Industrial Gas Turbine Burner Due to Changes in the Fuel Profile
Authors: Lindholm A. , Lo¨rstad D. , Magnusson P. , Andersson P. , Larsson T.
Published: February 2010

This paper deals with an experimental investigation of dry low emission (DLE) burners for industrial gas turbines. Changes in the fuel profile, pressure drop over the burner and external pilot flame stabilization have been investigated regarding combustion stability and emissions. This has been achieved by parallel experimental work in a water rig and a newly commissioned atmospheric combustion test rig. Some verifying tests in a high pressure rig were also conducted. The work in the water rig has been directed towards evaluating different fuel profiles at the burner exit due to changes in the fuel outlet geometry. Variations of the fuel outlet geometry were achieved by altering the effective area of the hardware configuration of the fuel outlet ports or by moving or adding fuel outlet ports. A few of the tested configurations in the water rig was chosen for further evaluation by atmospheric combustion tests with respect to combustion stability and emissions. A more general study on combustion stability and emissions was also performed for different burners, burner configurations and variations in pressure drop over the burner. The pressure drop over the burner in the test corresponds very well to the pressure drop measured over a single burner in an annular combustion chamber of an industrial gas turbine at different loads. The combustion was monitored by a high speed video camera equipped with an image intensifier. Simultaneously the dynamic pressure was measured by a piezoelectric pressure transducer, making it possible to know when each image was taken relative to the pressure. Results for different hardware configurations will be shown considering the frequency response from the flame and the dynamic pressure as well as the characteristic combustion instability close to lean blowout.
Aerodynamic and End-Wall Film Cooling Investigations of a Gas Turbine Nozzle Guide Vane Applying Temperature-Sensitive Paint
Authors: Kunze Martin , Vogeler Konrad , Brown Glenn , Prakash Chander , Landis Kenneth
Published: February 2010

This paper presents endwall film cooling investigations with a single row of fanshaped holes in a low-speed, six-bladed linear cascade. The variation of the cascade loading was achieved by changing the incidence. The investigated profile is based on a nozzle guide vane of a highly loaded gas turbine. The aerodynamic performance was investigated using pneumatic probes. The film-cooling effectiveness distribution is determined using the temperature-sensitive paint technique (TSP). Carbon dioxide was used as coolant to provide elevated density ratios of about 1.4. Although low thermal conductivity material is used for the endwall test plate, the measured temperature fields show influences of 3D heat conduction inside the test plate. To measure film effectiveness and the heat transfer separately, an adiabatic test surface is needed. Therefore the effects of heat conduction are modeled using the FE-method. With the resulting convective heat flux pattern derived from the computations, the endwall film cooling measurements are corrected. Furthermore this approach is applied to evaluate the heat loss inside the holes and the film discharge temperature at the hole exit.
Verification of RANS for Analyzing Convective Cooling System With and Without Ribs
Authors: Chen Wei , Ren Jing , Jiang Hongde
Published: February 2010

Accurate prediction of pressure drop and heat transfer in convective cooling system is of importance to gas turbine industry. In the present paper, a detailed study and assessment of RANS method based on SST reattach turbulence model is performed on a convective cooling system in three kinds of U-duct: smooth, with 45 degree or 90 degree angled parallel ribs. Heat transfer and pressure drop distributions in the ducts are analyzed spatially at the Reynolds numbers of 15000, 30000 and 60000. The numerical results are compared with the experimental data and the empirical correlation from Han et al. It is found that the obtained pressure drop distribution based on RANS with SST reattach turbulence model matches the experimental data for all the U-ducts adequately. Meanwhile, the heat transfer is well predicted by the RANS method in the cases of smooth duct and 45 degree ribbed duct. A good agreement is obtained in the turn region of 45 degree ribbed duct, it owes to the strong secondary flow induced by ribs, which restrain the mainstream to separate and accelerate in the turn. But, the heat transfer is significantly under-predicted for 90 degree ribbed duct since the flow reattachment point between the ribs is predicted farther away from the upstream rib than that in the experiment. Therefore, it is suggested that the RANS method with a suitable turbulence model is valuable for the smooth and 45 degree ribbed U-duct with the acceptable engineering accuracy. But the prediction of heat transfer in 90 degree ribbed U-duct is still a challenge for the RANS to solve.
ISO 21789: A New Gas Turbine Safety Standard
Authors: Santon Roger C.
Published: February 2010

The new International Standard on gas turbine safety, ISO 21789 [1], has been under development for over seven years. This paper describes its origins, development and content. The standard grew from concerns over a perceived risk of incidents, and the need for a uniform approach to safety. Desire for the provision of recognised means of compliance with relevant European Directives was also a strong factor. Details of the logistics of the development of a standard of this complexity have been included in this paper to demonstrate the very substantial resources required and the enormous level of support given by manufacturers, users, regulators and others. Also included are some of the problems and pitfalls that can arise during a project of this type. The paper provides some broad details of the scope and content of the standard, with particular reference to earlier relevant ASME IGTI papers. The standard deals comprehensively with all the hazards associated with gas turbines used for power generation and similar duties, including mechanical, electrical, fire and explosion. Whilst primarily a procurement standard for new equipment, it covers safety in design affecting commissioning, operation, maintenance and disposal, compliance verification, and information for use.
The Effect of Turning Vanes on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel
Authors: Zehnder Frank , Schu¨ler Marco , Weigand Bernhard , von Wolfersdorf Jens , Neumann Sven Olaf
Published: February 2010

Gas turbine blades are usually cooled by using ribbed serpentine internal cooling passages which are fed by extracted compressor air. The individual straight ducts are connected by sharp 180° bends. The integration of turning vanes in the bend region lets one expect a significant reduction in pressure loss while keeping heat transfer levels high. Therefore, the objective of the present study was to investigate the influence of different turning vane configurations on pressure loss and local heat transfer distribution. The investigations were conducted in a rectangular two-pass channel connected by a 180° sharp turn with a channel height-to-width ratio of H/W = 2. The channel was equipped with 45° skewed ribs in a parallel arrangement with e/dh = 0.1 and P/e = 10. The tip-to-web distance was kept constant at Wel/W = 1. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Furthermore static pressure measurements were conducted in order to determine the influence of turning vane configurations on pressure loss. Additionally, the configurations were investigated numerically by solving the Reynolds-Averaged Navier-Stokes equations (RANS method) using the Finite-Volume solver FLUENT. The numerical grids were generated by the hybrid grid generator CENTAUR. Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f turbulence model. The results showed a significant influence of the turning vane configuration on pressure loss and heat transfer in the bend region and the outlet pass. While using an appropriate turning vane configuration pressure loss was reduced by about 25% keeping the heat transfer at nearly the same level in the bend region. An inappropriate configuration led to an increase in pressure loss while heat transfer was reduced in the bend region and outlet pass.
Thermal Property Measurements of YSZ-Al2O3 Ceramic Composites
Authors: Silva Monica B. , Guo S. M. , Uppu Nalini , Diwan Ravinder , Mensah Patrick F.
Published: February 2010

Thermal barrier coatings (TBCs) are used in gas turbine engines to achieve a higher working temperature, and thus lead to a better efficiency. Yttria-stabilized-zirconia (YSZ), a material with low thermal conductivity, is commonly used as the top coat layer to provide the thermal barrier effect. Recent studies demonstrated that YSZ-Al2O3 composite layer could reduce the oxygen diffusion through the TBC, thus YSZ-Al2O3 composite layer potentially could be used to mitigate the spalling induced failure of a TBC coating. The goal of this study is to investigate the effect of the addition of Al2O3 on the thermal properties of YSZ based TBCs. In this study, a stainless steel die was used to make disk shaped samples with 0, 1, 2, 3, 4 and 5 wt% Al2O3 /YSZ powder ratios under uniaxial pressure. A laser flash system was used to measure the thermal diffusivity for all samples and the porosity of the samples is measured using mercury porosimetry. It is found that adding Al2O3 to YSZ decreases the thermal conductivity and increases the porosity of the ceramic composites.
Numerical Simulation of Complex Air Flow in an Aeroengine Gear Box
Authors: Sun Zixiang , Chew John W. , Fomison Neil
Published: February 2010

The internal gear box (IGB) of an aeroengine represents a severe challenge in computational fluid dynamics (CFD). In the present study, an axisymmetric CFD model was assessed to investigate the complex internal air flow in an aeroengine IGB. All the non-axisymmetric components and geometry features inside the gear box, such as bearings, gears, bolts and slots, as well as the radial drive system and vent pipes, were simulated using porous media models. Their flow resistance was estimated either by empirical correlations or by preparatory CFD studies and comparison with measurements. To evaluate the CFD technique adopted in the present investigation, a separate bolt windage study was conducted using a similar axisymmtric CFD model with the porous media approach. Good agreement of the bolt windage with other workers’ rig test data was observed. The present application of the porous media approach into a complex gear box flow represents a first attempt to use state of art CFD to assist an industrial design. Both maximum take-off (MTO) and ground idle (GI) running conditions were investigated. The complex flow patterns in the gear box were obtained. The results show a similar dimensionless performance of intermediate pressure (IP) and high pressure (HP) gears between the two operating conditions. For the present gear box arrangement under investigation, the CFD results suggest that the airflows induced by the HP gear and HP bearing are higher than their IP counterparts. A comparison with power absorption rig test data for the similar HP crownwheel in isolation shows that an assumption of pressure loss coefficient of 10 for the porous media of bevel gears may be appropriate, as the HP gear torque coefficient obtained in the CFD prediction is equal to 0.05, very close to its expected value. In addition, the effects of an assumed stationary IP gear and a large seal clearance on the HP gear performance were also investigated. The numerical results show that their impacts are insignificant, probably due to the strong pumping effects of the HP gear. Further discussion on the possible influence of the airflow on the oil motion within the gearbox and assistance to improve the traditional internal airflow models used for bearing chamber sealing analysis was also made. Three dimensional geometry modeling and inclusion of the oil phase are considered feasible. Such further investigations would aid the understanding of the interaction between the induced airflow due to the rotating components and oil motion, and their impact on oil scavenging behaviour and ‘windage’ contribution to heat oil.
Active Control Turbocharger (ACT): A Method to Improve Energy Extraction From an Engine Exhaust Gas
Authors: Me´rigot Yoann , Rajoo Srithar , Martinez-Botas R. F.
Published: February 2010

Variable geometry turbochargers (VGT) offer boosting solution which overcomes many of the conventional turbo charging problems such as turbolag and engine matching. However, VGT which are dominantly controlled based on engine load and speed, does not completely address the pulsating nature of the exhaust gas. Thus, the current VGT are not fully utilizing the energy available especially at the lower region of the exhaust pulse. An advanced turbo charging technique called Active Control Turbocharger (ACT) is proposed and demonstrated through experiment and simulation; where the turbine geometry will be operated actively to adapt to the pulsating exhaust flow in order to maximize the energy extraction while minimizing the penalty on the overall turbine efficiency.
SOFC-Based Hybrid Cycle Integrated With a Coal Gasification Plant
Authors: Romano Matteo C. , Campanari Stefano , Spallina Vincenzo , Lozza Giovanni
Published: February 2010

Application of large scale high temperature fuel cells on syngas fuel produced from coal would be a turning point in the power generation sector, dramatically improving the efficiency and the environmental performance of coal-fired power plants. The purpose of this study is the assessment of a system constituted by a SOFC-based hybrid cycle integrated with a coal gasification process. In this system, syngas produced in a high efficiency, dry feed, oxygen blown, entrained flow Shell gasifier is cooled, depurated from particulate and sulfur compounds and reheated; the clean syngas feeds a pressurized SOFC together with high pressure air generated by the compressor of a gas turbine. After combustion of unconverted syngas, fuel cell exhausts are expanded and cooled, providing heat to a bottoming steam cycle for an efficient energy recovery. A high integration between gasification and power islands is necessary in order to obtain an elevated efficiency: the heat recovery system from syngas cooling is carefully arranged to provide thermal power for clean syngas reheating, air preheating and steam generation. The paper presents a preliminary analysis of literature results and a discussion of the thermodynamic implications arising from the use of different primary fuels in a fuel cell-gas turbine cycle. Then the work presents a detailed thermodynamic analysis of the proposed IGFC layout, assessing the effect of SOFC operating pressure on power balance and net plant efficiency. A sensitivity analysis on the variation of fuel and air utilization in the fuel cell is also performed. Results show that the present innovative SOFC-based power system may achieve an efficiency gain of 7–11 percentage points, with respect to an advanced IGCC based on state of the art technology.
An Exploratory Study of an Oxyfuel Combustion Turbine Cycle With Vapor Absorption Refrigeration and Water Production
Authors: Shelton Walter , Le Patrick , Lear William E. , Dennis Richard , Wimer John
Published: February 2010

The preliminary findings of an exploratory study conducted on a novel Oxyfuel Combustion Turbine Cycle (OCTC) using ASPEN PLUS for a range of 40% to 90% CO2 capture are presented. Starting from a GE Energy IGCC, the OCTC retains the Gasifier with a Radiant Cooler-only section and the Warm-Gas-Clean Up (WGCU) section with the desulfurization process eliminated for a combined carbon and sulfur co-sequestration approach. The conventional gas turbine combined cycle is also removed. With no integration between the Air Separation Unit (ASU) and the modified oxyfuel combustion turbine, the High Pressure (HP) ASU is replaced by a Low pressure (LP) ASU. The added attributes of this novel coal-based power system configuration are (1) the Vapor Absorption Refrigeration System (VARS), (2) the associated water production in the VARS evaporator, (3) the recirculation of combustor flue gas for lower NOx emissions and additional power production, as well as (4) an original concept of carbon dioxide compression as proposed by SouthWest Research Institute (SwRI) and Dresser Rand (D-R). Assuming a reasonable Coefficient of Performance (COP) for the VARS, the overall process efficiency results (about 35% HHV) were equivalent or even better when compared with studies of current simulated IGCC systems with CO2 capture. Once an optimum scheme has been finalized in future activities, an economic analysis would be conducted. The combined performance and economic results could then be compared with alternate advanced coal based power systems.
TiAl Intermetallics for Aerospace Applications: Fracture Resistance and Cracking Mechanisms
Authors: Kumar Amar N. , Nayak Amiya , Srivastava Alka , Roy Udit K. , Patnaik Prakash C.
Published: February 2010

Research on TiAl aluminides has been undertaken to further advance the understanding of deformation and fracture mechanisms, vis-a`-vis the heat treatment effects on microstructure, fracture resistance and cracking mechanisms. Two TiAl grades considered comprise of Al-Nb-Mn-Cr-Bal Ti with two different microstructures, namely duplex and lamellar types. The size of colonies in fully lamellar structure also varied widely from 50 micron to 700 microns. Fracture toughness and crack growth resistance are studied under three point bend loading of SEN specimens at room temperature and at higher temperatures (700 °C and 900°C). The fracture resistance behavior for the intermetallics is studied following two methods, namely fracture toughness and crack growth resistance curves (KI vs. Δa). An appreciable improvement (around 50 percent) at 700°C is observed as compared to room temperature data. The crack size analysis is done by elastic compliance method and a normalized compliance curve (NCC) with a power law function for the aluminides is obtained irrespective of temperature. The mechanism of crack initiation as well as crack growth in different microstructures of the alloy is looked into to get an insight of the deformation and cracking process. In lamellar microstructure, colony boundaries appear to be the most preferred path for the crack growth, while multiple cracking mechanisms is observed in duplex structure.
Film Cooling Effectiveness and Heat Transfer Near Deposit-Laden Film Holes
Authors: Lewis Scott , Barker Brett , Bons Jeffrey P. , Ai Weiguo , Fletcher Thomas H.
Published: February 2010

Experiments were conducted to determine the impact of synfuel deposits on film cooling effectiveness and heat transfer. Scaled up models were made of synfuel deposits formed on film-cooled turbine blade coupons exposed to accelerated deposition. Three distinct deposition patterns were modeled: a large deposition pattern (max deposit peak ≅ 2 hole diameters) located exclusively upstream of the holes, a large deposition pattern (max deposit peak ≅ 1.25 hole diameters) extending downstream between the cooling holes, and a small deposition pattern (max deposit peak ≅ 0.75 hole diameter) also extending downstream between the cooling holes. The models featured cylindrical holes inclined at 30 degrees to the surface and aligned with the primary flow direction. The spacing of the holes were 3, 3.35, and 4.5 hole diameters respectively. Flat models with the same film cooling hole geometry and spacing were used for comparison. The models were tested using blowing ratios of 0.5–2 with a turbulent approach boundary layer and 0.5% freestream turbulence. The density ratio was approximately 1.1 and the primary flow Reynolds number at the film cooling row location was 300,000. An infrared camera was used to obtain the film cooling effectiveness from steady state tests and surface convective heat transfer coefficients using transient tests. The model with upstream deposition caused the primary flow to lift off the surface over the roughness peaks and allowed the coolant to stay attached to the model. Increasing the blowing ratio from 0.5 to 2 only expanded the region that the coolant could reach and improved the cooling effectiveness. Though the heat transfer coefficient also increased at high blowing ratios, the net heat flux ratio was still less than unity, indicating film cooling benefit. For the two models with deposition between the cooling holes, the free stream air was forced into the valleys in line with the coolant holes and degraded area-averaged coolant performance at lower blowing ratios. It is concluded that the film cooling effectiveness is highest when deposition is limited to upstream of the cooling holes. When accounting for the insulating effect of the deposits between the film holes, even the panels with deposits downstream of the film holes can yield a net decrease in heat flux for some cases.
Particulate Mass Emissions From Aircraft: A First Order Approximation Method Based on Experience From Diesel Particulate Mass Emissions Measurement
Authors: Andrews Gordon E. , Li Hu , Wright Stephen
Published: February 2010

Estimates of aero engine particulate composition and mass emissions are made over the LTO cycle using the smoke number measurement for carbon, hydrocarbon measurements for unburned fuel, lubricating oil consumption for the particulate lube oil fraction and fuel sulphur level for sulphate and associated water. The method is applied to six aircraft with different engine technologies. Comparison is made with the ICAO FOA method for particle mass and it is argued that the present proposals are an improved approach and are founded in experience in the measurement of diesel particulate mass emissions.
Effective Utilization of Operating Data in Asset Management
Authors: Christiansen Thomas M. , Giles Kate M.
Published: February 2010

An effective asset management system allows a business to define and measure plant performance relative to corporate & market expectations, as well as identifying potential issues that, if corrected, will improve plant profitability. Operational information is one critical element in any asset management system. Capturing, interpreting, storing and reporting this information requires a systematic approach that results in an infrastructure that is flexible, easy to use, and comprehensive. The development of an effective information system infrastructure must account for current & future reporting requirements, the varied sources of available data and the processes behind data capture, transformation & storage. The approach to developing this infrastructure also needs to consider the requirements of; the plant, its customers, its corporate entity as well as any applicable regulatory agencies. The objective of this paper will be to define the elements of an effective information infrastructure and to highlight approaches used by various power plants in creating their asset management information infrastructure.
Overspray Fog Cooling in Compressor Using Stage-Stacking Scheme With Non-Equilibrium Heat Transfer Model for Droplet Evaporation
Authors: Khan Jobaidur R. , Wang Ting
Published: February 2010

The inlet fog cooling scheme has been proven as an economic and effective means to augment gas turbine output power on hot or dry days. A previous paper developed a stage-by-stage wet-compression theory for overspray and interstage fogging using the equilibrium droplet evaporation model with given compressor and blade configurations. This paper extends the previous work by including the non-equilibrium droplet heat transfer model. An 8-stage, 2-D compressor airfoil geometry and stage settings at the mean radii are employed. Eight different cases including saturated fogging, overspray with different droplet sizes with both equilibrium and non-equilibrium heat transfer models have been investigated and compared. The results show saturated fogging increases the pressure ratio and reduces the compressor power consumption; however, overspray actually increases both the specific and total compressor power consumption. Non-equilibrium method differs from the equilibrium method due to the change of evaporation rate. Droplet size doesn’t play a role in equilibrium approach, but plays a major role in affecting the result in the non-equilibrium case. For small droplet size of 10 μm, the droplet evaporation rate is fast, so the non-equilibrium method predicts close results as the equilibrium method. Larger droplets lead to slower evaporation, reduction of pressure ratio, and less effective compressor performance than the smaller droplets. Equilibrium method predicts that wet compression increases axial velocity, blade inlet velocity, incidence angle, and tangential component of velocity. Non-equilibrium methods predict a similar trend except with lesser increments as the droplet size increases. In the present study, the equilibrium method predicts that all the water droplets evaporate completely at the end of stage 3, while the non-equilibrium approach predicts that the completion of evaporation delays, but all droplets completely evaporate in the compressor except the biggest droplets (30μm). Saturated fogging increases air density; however, both equilibrium and non-equilibrium methods predict that overspray wet compression actually reduces air density in the earlier 70% of the compressor. Non-equilibrium predicts small droplets relax the load in the earlier stages but increases the load in the later stages. Larger droplets show less load changes. Detailed stage-to-stage performance and property value changes are analyzed and discussed in this study.
Computer-Aided Dimensioning and Validation of a Versatile Test Facility for Combustion Chambers and Turbines
Authors: Leitgeb Thomas , Giuliani Fabrice , Niederhammer Andreas , Pirker Hermann-Peter
Published: February 2010

The continuous flow test facility at Graz University of Technology was originally designed for cold sub- and transonic experimental research on different turbine stages (2001-GT-0489). The operation range of the facility was recently extended to hot flows for investigations on the behavior of high-temperature resistant sensors embedded in gas-turbines and analysis of cooling systems of turbine blades or multiple-burner combustors, where each air supply is driven separately. Therefore, a 5 MW thermal air heater has been connected to the institute’s 3 MW compressor station. The dimensioning of the air system was done with IPSE-pro which is a commercial software package for simulation of basic thermodynamic processes. The standard modules of IPSE-pro were modified for calculating the mass flow distributions with respect to the prevailing pressure drops. As the air system is complex and relies on control valves to maintain specific mass flow rates, IPSEpro allows analysis of the behaviour of the test facility at several compressor station configurations. The main test facility dimensions and characteristics, as well as the most important equations describing the component models of IPSEpro are shown. Simulation results of several operation points are compared to measured data to validate the methodology. This work was done in the frame of the European research program New Aero Engine Core Concepts (NEWAC) at Graz University of Technology.
Parametric Study on Topping Cycle SOFC-MGT Hybrid Power System
Authors: Duan Liqiang , Tao De’an , Yang Yongping , He Binbin
Published: February 2010

In order to further improve the power generation efficiency, the hybrid power generation system integrated with high temperature fuel cell system has become the research focus in recent years. From the viewpoint of intercrossing of thermodynamics and electrochemistry, this paper studies the Solid Oxide Fuel Cell-Micro Gas Turbine (SOFC-MGT) hybrid combined cycle system. Firstly, based on the electrochemical analysis, SOFC system model is built and the effects of main parameters (current density, operating temperature and pressure, fuel utilization ratio, et al) on the overall SOFC system are analyzed; then, on the base of integration idea of total energy system, the topping cycle SOFC-MGT hybrid power system has been studied. The key parameters (such as current density, fuel utilization ratio, operating pressure and temperature) that greatly influence the hybrid system performance have been studied and optimized. The research results show both the thermodynamic parameters and electrochemical parameters have an important effect on the overall system performance; the topping cycle SOFC-MGT hybrid system will have a higher efficiency by increasing the operating temperature, operating pressure and fuel utilization ratio; when the operating temperature is 1173K and the current density is 3000A/m2, the hybrid system efficiency is up to 67.39%, which is even higher than that of the current advanced large-scale gas-steam combined cycle system. The achievements obtained from this paper will provide some valuable information for further study on SOFC-GT hybrid system with high efficiency.
Analysis and Simulation of Combustion Oscillations in a Laboratory Spray Combustor
Authors: Yao Z. P. , Zhu M. , Dowling A. P.
Published: February 2010

The unstable combustion that can occur in combustion chambers is a major problem for aeroengines and ground-based industrial gas turbines. Nowadays, CFD provides a flexible, low cost tool to supplement direct measurement. This paper presents simulations of combustion oscillations in a liquid-fuelled experimental rig at the University of Cambridge. Linear acoustic theory was used to describe the acoustic waves propagating upstream and downstream of the combustion zone and to develop inlet and outlet boundary conditions just upstream and downstream of the combustion region enabling the CFD calculation to be efficiently concentrated on the combustion zone. A combustion oscillation was found to occur with its predicted frequency in good agreement with experimental measurements. More details about the unstable combustion can be obtained from the simulation results. The approach developed here is expected to provide a powerful tool for the design and operation of stable combustion systems.
Flowfield Investigation of a Compressor Cascade at High Incidence—Part 2: Numerical Analysis
Authors: Zachos Pavlos K. , Pengue Fabio , Pachidis Vassilios , Pilidis Pericles
Published: February 2010

The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade performance remains unexplored at very far off-design conditions characterised by operation under extremely low mass flows and rotational speeds which imply highly negative incidence angle values. In this work the development and validation against experimental data of a CFD model for predicting the flowfield in a compressor cascade at a highly negative incidence angle is presented. The CFD model has been tested for quite a wide range of Mach numbers, and an extensive analysis of the tools provided by the CFD code has been carried out. Several turbulence models have been tested, different meshes have been compared and various boundary condition sets have been applied to the model in order to achieve results as close as possible to the experimental data. The model is validated against the experimental results and the maximum observed deviation was found to be within reasonable order of magnitude. In addition, most trends of the properties of interest have been captured sufficiently, therefore the physical phenomena can be considered quite well predicted allowing the numerical tool to be used for further studies on similar test cases.
Polygeneration System for Power and Liquid Fuel With Sequential Connection and Partial Conversion Scheme
Authors: Jin Hongguang , Gao Lin
Published: February 2010

As one important direction of clean coal technology with promising prospect, polygeneration system has an attractive performance both in coal liquefaction (or chemical production) and power generation. On the basis of the integration principle of chemical energy cascade utilization, a novel polygeneration system for power and liquid fuel (methanol) production, which innovatively integrates the fresh gas production subsystem without water-gas shift unit and the methanol synthesis subsystem adopting partial-recycle scheme, has been proposed in this paper. Taking another polygeneration system adopting the water-gas shift unit and Once Through Methanol (OTM) scheme as the reference, the new system has been investigated and assessed. The primary energy saving of new system is as high as 15%, which is significantly superior to 5∼8% in the reference system. With special attention on the interactions between the chemical production process and the thermal cycle, the integration features of the new system and the internal reason for its superior performance have been revealed, and the role of chemical energy utilization in system integration has been identified.
Performance Improvement of an Aero Gas Turbine Combustor
Authors: Srinivasa Rao M. , Sivaramakrishna G.
Published: February 2010

The HETD (Hot End Technologies Directorate) of GTRE (Gas Turbine Research Establishment) has the mandate of design, development and delivery of airworthy combustor and afterburner modules for a military aero gas turbine engine. In order to meet the mandate, the directorate takes the overall responsibility of design to manufacture of the combustion systems. Three-dimensional CFD (Computational Fluid Dynamics) analyses played a vital role in arriving at the final configuration meeting the specific design targets. This paper focuses on the utilization of the CFD code ‘Fluent’ in the successful realization of the main combustor of an aero gas turbine engine.
Optimization of Condition-Based Maintenance for Industrial Gas Turbines: Requirements and Results
Authors: Bohlin Markus , Wa¨rja Mathias , Holst Anders , Slottner Pontus , Doganay Kivanc
Published: February 2010

In oil and gas applications, the careful planning and execution of preventive maintenance is important due to the high costs associated with shutdown of critical equipment. Optimization and lifetime management for equipment such as gas turbines is therefore crucial in order to achieve high availability and reliability. In this paper, a novel condition-based gas turbine maintenance strategy is described and evaluated. Using custom-made gas turbine maintenance planning software, maintenance is repeatedly reoptimized to fit into the time intervals where production losses are least costly and result in the lowest possible impact. The strategy focuses on accurate online lifetime estimates for gas turbine components, where algorithms predicting future maintenance requirements are used to produce maintenance deadlines. This ensures that the gas turbines are maintained in accordance with the conditions on site. To show the feasibility and economic effects of a customer-adapted maintenance planning process, the maintenance plan for a gas turbine used in a real-world scenario is optimized using a combinatorial optimization algorithm and input from gas turbine operation data, maintenance schedules and operator requirements. The approach was validated through the inspection of a reference gas turbine after a predetermined time interval. It is shown that savings may be substantial compared to a traditional preventive maintenance plan. In the evaluation, typical cost reductions range from 25 to 65%. The calculated availability increase in practice is estimated to range from 0.5 to 1%. In addition, downtime reductions of approximately 12% are expected, due solely to improved planning. This indicates significant improvements.
Repair and Rejuvenation of a Severely Damaged 16-Stage Steam Turbine Rotor
Authors: Ingistov S. , Bhargava R. K. , Doerksen G.
Published: February 2010

This paper describes the recent experience with the extensive overhaul and repairs of a long and flexible 16-stage steam turbine rotor of an integral design. An integral design steam turbine rotor is one where the shaft and disks are machined from a single forging. The steam turbine had sustained a crack at the base of the 11th stage disk as well as moderate to extensive corrosion pitting throughout the center section (stages 5 to 8) of the rotor. The rim of the 6th stage disk also required rebuilding because of the excessive damage due to corrosion and pitting. The steps required to optimize the repair process and minimize repair time as well as precautions taken during the repairs are discussed in this paper. To ensure reliability of the rebuild work, including newly manufactured blades for the 6th stage disk, stress analysis using Finite Element Method (FEM) was used to verify that stress levels are within acceptable limits in the blade’s root-to-dovetail groove, the results of such an analysis are included here. Finally, results of high speed balancing, critical for such a large flexible rotor are presented and discussed. This repair and rejuvenation work allowed salvaging the severely damaged rotor in approximately 5 months (compared to up to 2 years delivery for a new rotor) and at about one-fourth the rotor replacement cost.
A Novel Technique for Assessing Turbine Cooling System Performance
Authors: Luque S. , Povey T.
Published: February 2010

A new experimental technique for the accurate measurement of steady-state metal temperature surface distributions of modern heavily film-cooled turbine vanes has been developed and is described in this paper. The technique is analogous to the thermal paint test, but has been designed for fundamental research. The experimental facility consists of an annular sector cascade of HP turbine vanes from a current production engine. Flow conditioning is achieved by using an annular sector of deswirl vanes downstream of the test section, being both connected by a three-dimensionally contoured duct. As a result, a transonic and periodic flow, highly representative of the engine aerodynamic field, is established: inlet turbulence levels, mainstream Mach and Reynolds numbers, and coolant-to-mainstream total pressure ratio are matched. Since the fully three-dimensional NGV geometry is used, the correct radial pressure gradient and secondary flow development are simulated and the cooling flow redistribution is engine-realistic. To allow heat transfer measurements to be performed, a mainstream-to-coolant temperature difference (up to 33.5 °C) is generated by using two steel-wire mesh heaters, operated in series. NGV surface metal temperatures are measured (between 20 and 40 °C) by wide-band thermochromic liquid crystals. These are calibrated in situ and on a per-pixel basis against vane surface thermocouples, in a heating process that spans the entire colour play and during which the turbine vanes can be assumed to slowly follow a succession of isothermal states. Experimental surface distributions of metal effectiveness are presented in this paper. By employing resin vanes of the same geometry and cooling configuration (to implement adiabatic wall thermal boundary conditions) and the transient liquid crystal technique, surface distributions of external heat transfer coefficient and film cooling effectiveness will be acquired. By combining these measurements with those from the metal vanes, the results can be scaled to engine conditions with a good level of accuracy.
CFD Simulation of a Microturbine Annular Combustion Chamber Fuelled With Methane and Biomass Pyrolysis Syngas: Preliminary Results
Authors: Fantozzi Francesco , Laranci Paolo , Bianchi Michele , De Pascale Andrea , Pinelli Michele , Cadorin Margherita
Published: February 2010

Micro gas turbines could be profitably used, for distributed energy production, also exploiting low calorific value biomass-derived fuels, obtained by means of integrated pyrolysis and/or gasification processes. These synthesis gases show significant differences with respect to natural gas (in terms of composition, low calorific value, hydrogen content, tar and particulate matter content) that may turn into ignition problems, combustion instabilities, difficulties in emission control and fouling. CFD simulation of the combustion chamber is a key instrument to identify main criticalities arising when using these gases, in order to modify existing geometries and to develop new generation combustion chambers for use with low calorific value gases. This paper describes the numerical activity carried out to analyze the combustion process occurring inside an existing microturbine annular combustor. A CFD study of the combustion process performed with different computational codes is introduced and some preliminary results are reported in the paper. A comparison of results obtained with the different codes is provided, for the reference case of methane combustion. A first evaluation of the pollutant emissions and a comparison with the available experimental data is also provided in the paper, showing in particular a good matching of experimental data on NOx emissions at different load conditions. Moreover, the carried out investigation concerns the case of operation with a syngas fuel derived from pyrolysis of biomass and finally the case of syngas and natural gas co-firing. This combustion condition is simulated with a simple reduced chemical kinetic scheme, in order to assess only the key issues rising with this fuel in comparison with the case of methane combustion. The analysis shows that in case of syngas operation the combustor internal temperature hot spots are reduced and the primary zone flame tends to stabilize closer to the injector, with possible implications on the emission release.
Lube Oil and Bearing Thermal Management System
Authors: Justice Karleine M. , Dalton Jeffrey S. , Halliwell Ian , Williamson Stephen
Published: February 2010

Recent improvements in technology have enabled the development of models capable of capturing performance interactions in the thermal management of air vehicle systems. Such system level models are required for better understanding of integration constraints and interactions, and are becoming increasingly important because of the need for tighter coupling between the components of thermal management systems. The study described here integrates current engine modeling capabilities with an improved, more comprehensive thermal management simulation. More specifically, the current effort evaluates the heat loads associated with the lubrication system of a gas turbine engine. The underlying engine model represents a mid-size, two-spool, subsonic transport engine. The architecture of the model is adaptable to other two-spool turbine engines and missions. Mobil Avrex S Turbo 256 engine oil is used as the lubrication medium. The model consists of five bearing heat loads. Within the engine flowpath, local temperatures and the appropriate rotational speeds are the only parameters pertinent to the heat load calculations. General assumptions have been made to simplify the representation of the lubrication system. Fuel properties into the heat exchanger are assumed. A gear box attached to the high-speed shaft operates both supply pump and scavenge pump and sends compressed air to the oil reservoir. Once the oil is distributed to the bearings, the scavenge pump collects and sends it through a filter and a fuel/oil heat exchanger before it is remixed with the contents of the reservoir. A MATLAB/Simulink modeling environment provides a general approach that may be applied to the thermal management of any engine. As a result of this approach, the new model serves as a starting point for a flexible architecture that can be modified as more detailed specifications or data are made available. In this paper, results from the simple model are compared to a more comprehensive tribology-based analysis. The results demonstrate its successful application to a typical mission, based on very limited data. In general, these results will allow system designers to conduct preliminary analyses and trade studies of gas turbine engine thermal management systems.