bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials and Structures Research for Gas Turbine Applications Within the NASA Subsonic Fixed Wing Project
Authors: Hurst Janet B.
Published: January 2011

In an era of both declining NASA budgets and demanding space goals, the NASA Aeronautics Research Mission Directorate has elected to address foundational research problems for aeronautics. To this end, the Subsonic Fixed Wing (SFW) Project, within the Fundamental Aeronautics Program, has selected challenging goals which anticipate an increasing emphasis on aviation’s impact upon the global issue of environmental responsibility. These SFW project goals are greatly reduced noise, reduced emissions and reduced fuel consumption. Specific goals, selected by a combination of systems analysis, experience and industry input, are generational in approach, addressing 25 to 30 years of technology development. Successful implementation of these demanding goals will require development of new materials and structural approaches within gas turbine propulsion technology. The Materials and Structures discipline, within the SFW project, comprise cross-cutting technologies ranging from basic investigations to component validation in laboratory environments. Material advances are teamed with innovative designs in a multidisciplinary approach with the resulting technology advances directed to promote the goals of reduced noise and emissions along with improved performance. For propulsion needs, these technologies have been grouped into three basic categories. The first is improved hot section materials for hotter engines with minimal cooling requirements to promote reduced NOx and fuel burn. Among the technologies of interest have been new alloy compositions and improved thermal barrier coatings systems with improved capabilities. The second category being investigated for propulsion applications is lightweight and multifunctional systems which will permit reduced fuel burn via weight reduction in the engine and its surrounding structure. An example of this technology is High Temperature Shape Memory Alloys (HTSMA) for actuation applications requiring large displacements and low frequencies such as chevrons and variable area nozzles for high bypass ratio engines. The final area under investigation is the concept of the more electric aircraft, which at this time is focused primarily on turboelectric technology as a available to make reasonable progress. Technologies from very basic fundamental research to nearer term concepts are included. Additionally, vigorous supplementation of in-house capabilities is revolutionary approach to the entire SFW design space. Major challenges to be addressed in this field include improved cryocoolers and superconducting materials. A brief overview is presented of the current materials and structures research focused upon propulsion applications within the NASA Subsonic Fixed Wing Project. As such, it does not comprise the entirety of materials and structures research for gas turbine engines at NASA. Several other projects also include research of this type to address their specific project goals.
A Historical and Current Perspective of the Availability and Reliability Performance of Heavy Duty Gas Turbines: Benchmarks and Expectations
Authors: Della Villa Salvatore A. , Koeneke Carlos
Published: January 2011

Since its inception the gas turbine market has been driven by an emphasis on improved operating efficiency, greater megawatt output, with reduced environmental impact through technology advancement. The technology advances that have taken place include; higher firing temperatures and pressure ratios, improved cooling schemes with advanced metallurgy and coatings for hot gas path parts, consideration for tighter clearances, low emissions combustion systems, and fuels flexibility. Contemporaneously, there has been a commensurate focus on ensuring that the achievable levels of availability and reliability of these evolving product offerings would be optimized for various duty cycles, applications, and plant arrangements. In fact, as product evolution and advancement has taken place, there has been an expectation that availability and reliability performance would be consistent with the best achievable levels experienced by existing and more mature technologies. The purpose of this paper is to address the industry focus on availability and reliability (from EPRI to DOE), and to discuss the current and historical availability and reliability performance of gas turbines based on class; specifically “E” and “F” class. Additionally, this paper will also address the positive impact that “remote monitoring” has had; through the automation and computation of availability and reliability metrics. “Remote monitoring” has been introduced to provide an extra level of protection and diagnostic capability; providing an emphasis on performance, operability, and availability of the power generation equipment. The fact that “remote monitoring” has facilitated rapid data acquisition has had a positive impact on the calculation of availability and reliability metrics, making them more timely and accurate. This important point will also be discussed. With the permission of Mitsubishi Power Systems America (MPSA), specific data for the M501F fleet is presented. These comparisons will assist in establishing benchmarks for equipment performance based on duty cycle and other meaningful segmentations. Data available from SPS’s ORAP® (Operational Reliability Analysis Program) and other industry sources will be used to provide valid references for consideration.
CFD Predictions of CO Emission Trends in an Industrial Gas Turbine Combustor
Authors: Jella Sandeep , Gauthier Pierre , Paraschivoiu Marius
Published: January 2011

CFD predictions of emissions such as NOx and CO in industrial lean-premixed gas turbine combustors depend heavily on the degree to which the complexity of turbulent mixing and turbulence-chemistry interaction in the flow-field is modeled. While there is much difficulty in obtaining detailed and accurate internal data from high pressure combustors, there is a definite need for accurately understanding the flow physics towards the improvement of design. This work summarizes some experience with using the RANS and LES approaches in a commercial code, Fluent 6.3, to predict CO emissions and temperature trends in the two-stage Rolls-Royce RB211-DLE combustor. The predictions are validated against exit emissions (obtained from exhaust gas analysis) and some thermal paint tests for qualitative agreement on flame-stabilization. The upstream geometry (plenum and counter-swirlers) was included in order to minimize the effect of boundary conditions on the combustion zone. The presumed pdf approach as well as finite-rate chemistry models using the eddy dissipation concept were used to compare the predictions. It was found that there was a very significant benefit in moving to more advanced turbulence modeling methods to obtain realistic predictions in a confined, swirling burner. Thermal paint tests indicated that flame stabilization and temperatures (and therefore CO) was incorrectly predicted in the RANS context. LES results, on the other hand, more accurately predicted flame stabilization with corresponding improvements in the exit CO predictions. Ongoing work focuses on the variations that can be expected by varying discretization schemes, combustion models and sub-grid turbulence models as well as obtaining detailed internal data suitable for LES comparisons.
A Gas Turbine Performance Simulation Program and Its Application to an IGCC Gas Turbine
Authors: Lee Jong Jun , Kim Young Sik , Kim Tong Seop , Sohn Jeong Lak , Joo Yong Jin
Published: January 2011

This paper explains a performance simulation program for power generation gas turbines and its application to an IGCC gas turbine. The program has a modular structure and both the stage-level and entire component-level models were adopted. Stage-by-stage calculations were used in the compressor and the turbine. In particular, the compressor module is based on a stage-stacking method and is capable of simulating the effect of variable stator vanes. The combustor model has the capability of dealing with various fuels including syngas. The turbine module is capable of estimating blade cooling performance. The program can be easily extended to other applied cycles such as recuperated and reheated cycles because the program structure is fully modular. The program was verified for simple cycle commercial engines. In addition, the program was applied to the gas turbine in an IGCC plant. Influences of major system integration parameters on the operating conditions of the compressor and turbine as well as on engine performance were analyzed.
Comparative Study on Electric Turbo-Compounding Systems for Gasoline Engine Exhaust Energy Recovery
Authors: Wei Wei , Zhuge Weilin , Zhang Yangjun , He Yongsheng
Published: January 2011

Electric turbo-compounding system attracts more attention in recent years with the advance of electronic control devices. There are mainly three kinds of electric turbo-compounding systems for internal combustion engines: System A has an electric-assisted turbocharger, System B has a turbo-generator that is in series with the turbocharger, and System C has a turbo-generator that is in parallel with the turbocharger. A comparative study on the performance of these three kinds of systems for a 1.8L turbocharged gasoline engine is presented. The comparative study has been carried out using 1D simulation methods. The gasoline engine is modeled with the GT-POWER software and the turbochargers and turbo-generators are modeled with turbo through-flow models. The GT-DRIVE software is used to evaluate the system performance under driving cycles. The performance comparisons of different systems have been carried out under US06 and FTP75 driving cycles. Results show that the performance of System C is better than those of the other two kinds of systems. The fuel economy improvement of System C is 4.0% under US06 driving cycle and 1.6% under FTP75 driving cycle, compared with the original prototype engine.
Transition in Gas Turbine Control System Architecture: Modular, Distributed, and Embedded
Authors: Culley Dennis
Published: January 2011

Controls systems are an increasingly important component of turbine-engine system technology. However, as engines become more capable, the control system itself becomes ever more constrained by the inherent environmental conditions of the engine; a relationship forced by the continued reliance on commercial electronics technology. A revolutionary change in the architecture of turbine-engine control systems will change this paradigm and result in fully distributed engine control systems. Initially, the revolution will begin with the physical decoupling of the control law processor from the hostile engine environment using a digital communications network and engine-mounted high temperature electronics requiring little or no thermal control. The vision for the evolution of distributed control capability from this initial implementation to fully distributed and embedded control is described in a roadmap and implementation plan. The development of this plan is the result of discussions with government and industry stakeholders.
Prediction of Gas Turbine Trip Due to Electro Hydraulic Control Valve System Failures
Authors: Ravi Y. B. , Pandey Achalesh , Jammu Vinay
Published: January 2011

Gas turbines are the main power producing components in combined cycle and simple cycle power plants. A gas turbine trip is a rapid uncontrolled shutdown of the turbine that is initiated by the turbine controller to protect it from failures. The turbine loses significant amount of life due to strong thermal transients during a trip and the utility company loses revenue because of lost power generation. Therefore, prediction of trips has significant financial impact. This paper presents a method to predict gas turbine trips due to electro hydraulic control valve system failures. This paper also provides methods to detect gas control valve system failures in their incipient phase and methods to identify various failure signatures for diagnostics. The methodology presented here could be extended beyond the current application to other causes of trips in the gas turbine, thereby impacting availability and reliability of the turbine.
Conjugate Heat Transfer Analysis of a High Pressure Air-Cooled Gas Turbine Vane
Authors: Wang Zhenfeng , Yan Peigang , Huang Hongyan , Han Wanjin
Published: January 2011

The ANSYS-CFX software is used to simulate NASA-Mark II high pressure air-cooled gas turbine. The work condition is Run 5411 which have transition flow characteristics. The different turbulence models are adopted to solve conjugate heat transfer problem of this three-dimensional turbine blade. Comparing to the experimental results, k-ω-SST-γ-θ turbulence model results are more accurate and can simulate accurately the flow and heat transfer characteristics of turbine with transition flow characteristics. But k-ω-SST-γ-θ turbulence model overestimates the turbulence kinetic energy of blade local region and makes the heat transfer coefficient higher. It causes that local region temperature of suction side is higher. In this paper, the compiled code adopts the B-L algebra model and simulates the same computation model. The results show that the results of B-L model are accurate besides it has 4% temperature error in the suction side transition region. In addition, different turbulence characteristic boundary conditions of turbine inner-cooling passages are given and K-ω-SST-γ-θ turbulence model is adopted in order to obtain the effect of turbulence characteristic boundary conditions for the conjugate heat transfer computation results. The results show that the turbulence characteristic boundary conditions of turbine inner-cooling passages have a great effect on the conjugate heat transfer results of high pressure gas turbine. ANSYS is applied to analysis the thermal stress of Mark II blade which has ten radial cooled passages and the results of Von Mises stress show that the temperature gradient results have a great effect on the results of blade thermal stress.
Performance Benefits of a Portable Hybrid Micro-Gas-Turbine Power System for Automotive Applications
Authors: Christodoulou Fanos , Giannakakis Panagiotis , Kalfas Anestis I.
Published: January 2011

The lower fuel burn and pollutant emissions of hybrid electric vehicles give a strong motivation and encourage further investigations in this field. The know how on hybrid vehicle technology is maturing and the reliability of such power schemes is being tested in the mass production. The current research effort is to investigate novel configurations, which could achieve further performance benefits. This paper presents, an assessment of a novel hybrid configuration comprising a micro gas turbine, a battery bank and a traction motor, focusing on its potential contribution to the reduction of fuel burn and emissions. The power required for the propulsion of the vehicle is provided by the electric motor. The electric power is stored by the batteries, which are charged by a periodic function of the micro gas turbine. The micro gas turbine starts up when the battery depth of discharge exceeds 80% and its function continues until the batteries are full. The performance of the vehicle is investigated using an integrated software platform. The calculated acceleration performance and fuel economy are compared to the ones of conventional vehicles of the same power. The sensitivity of the results to the variation of the vehicle parameters such as mass, kinetic energy recovery and battery type is calculated to identify the conditions under which the application of this hybrid technology offers potential benefits. The results indicate that if no mass penalties are incurred by the installation of additional components the fuel savings can exceed 23%. However, an increase in the vehicle’s weight can shrink this benefit, especially in the case of light vehicles. Lightweight batteries and kinetic energy recovery systems are deemed essential enabling technologies for a realistic application of this hybrid system.
Risk Analysis of Gas Turbines for Natural Gas Liquefaction
Authors: Khan Raja S. R. , Lagana Maria Chiara , Ogaji Steven O. T. , Pilidis Pericles , Bennett Ian
Published: January 2011

Procurement of process plant equipment involves decisions based not only on an economic agenda but also on long term plant capability, which in turn depends on equipment reliability. As the greater global community raises environmental concerns and pushes for economic reform, a tool is evermore required for specific and critical selection of plant equipment. Risk assessments based on NASA’s Technology Readiness Level (TRL) scale have been employed in many previous risk models to map technology in terms of risk and reliability. The authors envisage a scale for quantifying technical risk. The focus of this paper is the technical risk assessment of gas turbines as mechanical drivers for producing Liquefied Natural Gas (LNG). This risk assessment is a cornerstone of the TERA philosophy, a Technoeconomic and Environmental Risk Analysis developed by Cranfield University’s Department of Power and Propulsion in the UK. Monte Carlo simulations are used in order to compare the risks of introducing new plant equipment against existing and established plant equipment. Three scenarios are investigated using an 87MW single spool, typical industrial machine; a baseline engine followed by an engine with increased firing temperature and finally an engine with a zero staged compressor. The results suggest that if the baseline engine was to be upgraded then the zero staging option would be a better solution than increasing firing temperature since zero staging gives the lower rise in Total Time to Repair (TTTR), or downtime. The authors suggest a scaling system based on NASA’s TRL but with modified definition criteria for the separate technology readiness levels in order to better relate the scale to gas turbine technology. The intention is to link the modified TRL to downtime, since downtime has been identified as a quantitative measure of technical risk. Latest developments of the modelling are looking at integrating risk analysis and a maintenance cost and scheduling model to provide a platform for total risk assessment. This, coupled with emissions modelling, is set to provide the overall TERA tool for LNG technology selection.
Validation of Test Rig Measurements and Prediction Tools for Friction Interface Modelling
Authors: Schwingshackl C. W. , Petrov E. P. , Ewins D. J.
Published: January 2011

The modelling of friction contact interfaces in structural dynamics attracts much interest in the gas turbine industry. In order to obtain reliable predictions of typical friction interfaces, such as encountered in under platform dampers or blade roots, accurate characteristics of friction interfaces must be provided to the analysis. It must be ensured that a sufficient number of parameters are provided, characterising all aspects of the friction contact, that the values are measured accurately, and that the contact parameters are interpreted and used correctly in the numerical modelling of the contact interfaces. This investigation demonstrates that measured friction coefficient and tangential contact stiffness are sufficient to reproduce the experimental friction interface behaviour and that these two parameters can be measured reliably in the available test rig. In combination with fine nonlinear interface meshes and accurate contact pressure representations, the measured interface behaviour of stick, micro- and macroslip is reproduced with good accuracy. The capability of modelling the microslip behaviour for the contact interface by a multitude of friction contact elements is explored and the effect of the normal stress distribution over the contact area on the microslip is studied.
Heat Transfer and Film Cooling of Blade Tips and Endwalls
Authors: Naik S. , Georgakis C. , Hofer T. , Lengani D.
Published: January 2011

This paper investigates the flow, heat transfer and film cooling effectiveness of advanced high-pressure turbine blade tips and endwall. Two blade tip configurations have been studied, including a full rim squealer and a partial squealer with a leading edge and trailing edge cut-out. Both blade tip configurations have pressure side film cooling, and cooling air extraction through dust holes which are positioned along the airfoil camber line on the tip cavity floor. The investigated clearance gap and the blade tip geometry are typical of that commonly found in the high pressure turbine blades of heavy-duty gas turbines. Numerical studies and experimental investigations in a linear cascade have been conducted at a blade exit isentropic Mach number of 0.8 and a Reynolds number of 9 × 105. The influence of the coolant flow ejected from the tip dust holes and the tip pressure side film holes has also been investigated. Both the numerical and experimental results showed that there is a complex aero-thermal interaction within the tip cavity and along the endwall. This was evident for both tip configurations. Although, the global heat transfer and film cooling characteristics of both blade tip configurations were similar, there were distinct local differences. The partial squealer exhibited higher local film cooling effectiveness at the trailing edge but also low values at the leading edge. For both tip configurations, the highest heat transfer coefficients were located on the suction side rim within the mid-chord region. However on the endwall, the highest heat transfer rates were located close to the pressure side rim and along most of the blade chord. Additionally, the numerical results also showed that the coolant ejected from the blade tip dust holes partially impinges onto the endwall.
A CFD Study of Low Reynolds Number Flow in High Lift Cascades
Authors: Pacciani Roberto , Marconcini Michele , Arnone Andrea , Bertini Francesco
Published: January 2011

A study of the separated flow in high-lift, low-Reynolds-number cascade, has been carried out using a novel three-equation, transition-sensitive, turbulence model. It is based on the coupling of an additional transport equation for the so-called laminar kinetic energy with the Wilcox k-ω model. Such an approach takes into account the increase of the non-turbulent fluctuations in the pre-transitional and transitional region. Two high-lift cascades (T106C and T108), recently tested at the von Ka´rma´n Institute in the framework of the European project TATMo (Turbulence and Transition Modelling for Special Turbomachinery Applications), were analyzed. The two cascades have different loading distributions and suction side diffusion rates, and therefore also different separation bubble characteristics and loss levels. The analyzed Reynolds number values span the whole range typically encountered in aeroengines low-pressure turbines operations. Several expansion ratios for steady inflow conditions characterized by different freestream turbulence intensities were considered. A detailed comparison between measurements and computations, including bubble structural characteristics, will be presented and discussed. Results with the proposed model show its ability to predict the evolution of the separated flow region, including bubble bursting phenomena, in high-lift cascades operating in LP-turbine conditions.
Evaluation of the Energy Dissipated as Friction/Heat Between Turbines Following Shaft Failure
Authors: Rojo I. , Psarra A. , Pachidis V. , Pilidis P.
Published: January 2011

The prevention of primary failure that may lead to a potentially hazardous event has always been a predominant aim in engine design and development. In the event of a shaft failure event, the turbine operates under high power conditions which may lead to blade release or disc burst. A potential mechanism to eliminate quickly the power of the free running turbine involves the dissipation of the kinetic energy as friction/heat due to structural interaction between turbines. In the scope of this paper, a finite element model is developed to study the energy dissipated due to structural interaction. A coupled thermo-mechanical analysis is carried out taking into account the temperature increase in the turbines’ structure following the severe impact. The coupled thermo-mechanical analysis addresses the effects of temperature rise and material softening on the evolution of the shaft failure event. The part of the kinetic energy converted into thermal and the wear rate of the seal segment structure are investigated in order to assess the potential of the contact mechanisms to act towards reducing the power of the free running turbine as quickly as possible due to blade tangling. Finally, the dependency of frictional energy and wear rate on the structural damping and the definition of the thermal material model have been studied highlighting their importance in the impact simulations.
Fan Shaped and Cylindrical Holes Studied in Vane Film Cooling Test Rig
Authors: Kinell Mats , Utriainen Esa , Hyle´n Jonas , Gustavsson Jonas , Bradley Andreas , Karlsson Matts , Wren Joakim
Published: January 2011

In order to optimize the vane film cooling and thereby increase the efficiency of a gas turbine, different film cooling configurations were experimentally investigated. Dynamic similarity was obtained regarding main flow Reynolds number, airfoil pressure coefficient, adiabatic wall temperature and film cooling ejection ratio. The maximum reached Mach number was 0.52. The geometry of the test section, consisting of one vane and two flow paths, was modified in order to meet the dimensionless pressure coefficient distribution around the airfoil experienced by a full stage airfoil. This would ascertain that scaled but engine realistic pressure gradients would be achieved in the rig test. During the test, the cold airfoil was suddenly imposed to a hot main stream and the evaluation of both the film cooling effectiveness and the heat transfer coefficient distribution on the visiable surface could be done at one single test using time-resolved temperature measurements obtained through IR thermography. A high resolution MWIR camera was used together with a silicon viewing window. The post-processing allowed for corrections regarding emissions and determination of the desired parameters on the vane surface. Results, heat transfer coefficients and film cooling effectiveness, for fan shaped and cylindrical film cooling holes configurations are compared. The results show clear benefit of using shaped holes over cylindrical ditto, especially on the suction side where near hole film effectiveness is enhanced by approximately 25%, but the results also show that this benefit diminishes to nothing in the suction side trailing edge region. The local heat transfer coefficients are generally lower for the shaped hole configurations. Contrary to the film effectiveness the shaped holes configurations show lower heat transfer coefficients also at the suction side trailing edge region, making use of the shaped hole configurations superior to cylindrical ones as the heat flux to the surface is reduced. Numerical predictions using a boundary layer code, TEXSTAN, and CFD, for a smooth wall configuration corresponds well with the measured results.
Combination of 1D Code and CFD for Performance Analysis of a Silo Type Gas Turbine Combustor
Authors: Rasooli N. , Besharat Shafiei S. , Khaledi H.
Published: January 2011

Whereas Gas Turbines are the most important producers of Propulsion and Power in the world and with attention to the importance of combustion chamber as one of the three basic components of Gas Turbine, various activities in different levels have been done on this component. Because of the environmental limitations and laws related to the pollutants such as NOx and CO, Lean Premixed Combustion Chambers are specially considered in gas turbine industries. This study is part of a Multi-Layer simulation of the whole gas turbine cycle in MPG Company. In this work, the combination of a general 1D code and CFD is used for deriving appropriate performance curves for a 1D and 0D gas turbine design, off-design and dynamic cycle code. This 1D code is a general code which has been developed for different combustion chambers; annular, can-annular, can type and silo type combustion chambers. The purpose of generating this 1D code is the possibility of fast analysis of combustors in different operating conditions and reaching required outputs. This 1D code is a part of a general simulation 1D code for gas turbine and was used for a silo type combustor performance prediction. This code generates required quantities such as pressure loss, exit temperature, liner temperature and mass distribution through the combustion chamber. Mass distribution and pressure loss are analyzed and determined with an electrical analogy. Results derived from 1D code are validated with empirical data available for different combustors. There is appropriate agreement between these experimental and analytical results. Drag coefficients for liner holes are available from experimental data and for burner are calculated as a curve with CFD simulations. What differs this code from other 1D codes for gas turbine combustors is the advantage of using combustion efficiencies evolved from numerical simulation results in different loads. These efficiencies are determined with CFD simulations and are available as maps and inserted into the gas temperature calculation algorithm of 1D code. In other 1D codes in this field, empirical correlations are used for combustion efficiency determination. Combustion efficiency curves for design and off-design conditions in this study are achieved by 2D and 3D simulation of combustion chamber with application of EBU/Finite Rate model and 8 step reactions of CH4 burning. Diffusion flame in low loads and premixed flame in high loads are considered. Flame stability and Lean Blow Out charts are evolved from CFD simulation and Heat transfer is applied with empirical correlations.
Effect of Blade Inclination Angle on a Darrieus Wind Turbine
Authors: Raciti Castelli Marco , Benini Ernesto
Published: January 2011

This paper presents a model for the evaluation of energy performance and aerodynamic forces acting on a small helical Darrieus vertical axis wind turbine depending on blade inclination angle. It consists of an analytical code coupled to a solid modeling software, capable of generating the desired blade geometry depending on the desired design geometric parameters, which is linked to a finite volume CFD code for the calculation of rotor performance. After describing and validating the model with experimental data, the results of numerical simulations are proposed on the bases of five machine architectures, which are characterized by an inclination of the blades with respect to the horizontal plane in order to generate a phase shift angle between lower and upper blade sections of 0°, 30°, 60°, 90° and 120° for a rotor having an aspect ratio of 1.5. The effects of blade inclination on tangential and axial forces are first discussed and then the overall rotor torque is considered as a function of azimuthal position of the blades. Finally, the downstream tip recirculation zone due to the finite blade extension is analyzed for each blade inclination angle, achieving a numerical quantification of the influence of induced drag on rotor performance, as a function of both blade element longitudinal and azimuthal positions of the blade itself.
Three-Dimensional Non-Reflecting Boundary Condition for Linearized Flow Solvers
Authors: Petrie-Repar Paul J.
Published: January 2011

A three-dimensional (3D) non-reflecting boundary condition for linearized flow solvers is presented. The unsteady aerodynamic modes at the inlet and outlet (far-field) are numerically determined by solving an eigen problem for the semi-discretized flow equations on a two-dimensional mesh. Unlike previous methods the shape of the far-field can be general and the non-uniformity of the steady flow across the far-field is considered. The calculated unsteady modes are used to decompose the unsteady flow at the far-field into modes. The direction of each mode is determined, and incoming modes are prescribed and outgoing modes are extrapolated. The results of 2D and 3D inviscid linearised flow simulations using the new boundary condition are presented.
Development and Experimental Validation of a Modelling Tool for Humid Air Turbine Saturators
Authors: Caratozzolo Francesco , Traverso Alberto , Massardo Aristide F.
Published: January 2011

This work presents the re-engineering of the TRANSAT 1.0 code which was developed to perform off-design and transient condition analysis of Saturators and Direct Contact Heat Exchangers. This model, now available in the 2.0 release, was originally implemented in FORTRAN language, has been updated to C language, fully coded into MATLAB/Simulink® environment and validated using the extensive set of data available from the MOSAT project, carried out by the Thermochemical Power Group of the University of Genoa. The rig consists of a fully instrumented modular vertical saturator, which is controlled and monitored with a LABVIEW® computer interface. The simulation software showed fair stability in computation and in response to step variation of the main parameters driving the thermodynamic evolution of the air and water flows. Considering the actual mass flow rates, a geometric similitude was used to avoid calculation instability due to flows under 100 g/s. Overall the model proved to be reliable and accurate enough for energy system simulations.
Prediction of Ingress Through Turbine Rim Seals: Part 1—Externally-Induced Ingress
Authors: Owen J. Michael , Zhou Kunyuan , Pountney Oliver , Wilson Mike , Lock Gary
Published: January 2011

Rotationally-induced (RI) ingress is caused by the negative pressure (relative to the external air) inside the wheel-space of a gas turbine; this negative pressure, which is created by the rotating flow in the wheel-space, drives the ingestion of hot gas through the rim seals. Externally-induced (EI) ingress is caused by the circumferential distribution of pressure created by the blades and vanes in the turbine annulus: ingress occurs in those regions where the external pressure is higher than that in the wheel-space, and egress occurs where it is lower. Although EI ingress is the dominant mechanism for hotgas ingestion in engines, there are some conditions in which RI ingress has an influence: this is referred to as combined ingress (CI). In Part 1 of this two-part paper, values of the sealing effectiveness (obtained using the incompressible orifice equations developed for EI ingress in an earlier paper) are compared with published experimental data and with results obtained using 3D steady compressible CFD (Computational Fluid Dynamics). Acceptable limits of the incompressible-flow assumption are quantified for the orifice model; for the CFD, even though the Mach number in the annulus reaches approximately 0.65, it is shown that the incompressible orifice equations are still valid. The results confirm that EI ingress is caused predominantly by the magnitude of the peak-to-trough circumferential difference of pressure in the annulus; the shape of the pressure distribution is of secondary importance for the prediction of ingress. A simple equation, derived from the orifice model, provides a very good correlation of the computed values of effectiveness. Using this correlation, it is possible to estimate the minimum sealing flow rate to prevent ingress without the need to know anything about the pressure distribution in the annulus; this makes the orifice model a powerful tool for rim-seal design.
Experimental and Numerical Investigation of Fretting Wear at High Temperature for Aeronautical Alloys
Authors: Botto D. , Campagna A. , Lavella M. , Gola M. M.
Published: January 2011

Fretting wear is a complex phenomenon that occurs at component interfaces that undergo low amplitude oscillation under high contact pressure. The aim of this paper is to investigate the fretting behavior of contact interfaces both with experiments and numerical code. The hysteresis cycles have been measured through the experiment and, at the end of the test, the worn volume has been determined. A numerical code has been developed to predict worn volume. The three-dimensional elastic contact problem has been solved by using a semi-analytical half space model. The numerical code uses a wear law for which the worn volume is proportional to the dissipated energy during the hysteresis cycle. The wear coefficient has been iteratively determined by comparing the theoretical results with the experimental tests. The main results of this work is the set up of a wear model for the given geometry and materials.
An Analytical Model of a Gas Turbine Components Performance and Its Experimental Validation
Authors: Pourfarzaneh H. , Hajilouy-Benisi A. , Farshchi M.
Published: January 2011

Gas turbine has broad applications in variety of industries. The developing gas turbine efficiency is of great engineering concern. This appeals to more precise modeling as somewhat inevitable. Modeling plays a decisive and essential role not only in all design phases, but also in development and manufacturing process to investigate performance of an engine. In this research, components of a gas turbine including air intake, axial and centrifugal compressors, combustion chamber and axial turbine are investigated. A novel dimensionless modeling approach is introduced and then, the engine performance parameters are predicted. Setting up a systematic series of experiments on the existing engine in Gas Turbine Laboratory at Sharif University of Technology, functional parameters of the components are obtained. The comparison of theoretical results with experimental results shows very good compliance.
Results of an Advanced Fan Stage Over a Wide Operating Range of Speed and Bypass Ratio: Part II—Comparison of CFD and Experimental Results
Authors: Celestina Mark L. , Suder Kenneth L. , Kulkarni Sameer
Published: January 2011

NASA and GE teamed to design and build a 57% engine scaled fan stage for a Mach 4 variable cycle turbofan/ramjet engine for access to space with multipoint operations. This fan stage was tested in NASA’s transonic compressor facility. The objectives of this test were to assess the aerodynamic and aero mechanic performance and operability characteristics of the fan stage over the entire range of engine operation including: 1) sea level static take-off; 2) transition over large swings in fan bypass ratio; 3) transition from turbofan to ramjet; and 4) fan wind-milling operation at high Mach flight conditions. This paper will focus on an assessment of APNASA, a multistage turbomachinery analysis code developed by NASA, to predict the fan stage performance and operability over a wide range of speeds (37% to 100%) and bypass ratios.
Impacts of Engine Secondary Air System Uncertainties on Gas Turbine Compressor Heat Transfer
Authors: Alizadeh Sohail , Gopinathrao Naveen
Published: January 2011

The compressor is a particularly sensitive component in a gas turbine engine. Variations from design geometry or operating conditions can have detrimental effects on performance, efficiency and compressor life. In this work the propagation of secondary air system operational uncertainty sources on a rotor-stator cavity at the front of a large turbofan IPC are assessed. The calculations are carried through from appropriate Computational Fluid Dynamics (CFD) analyses, characterising the flow and heat transfer in the cavity adjacent to an IP1 disc, to the FE Thermo-mechanical calculations. The application provides an example demonstration how uncertainty quantification may be undertaken for compressor analysis involving intensive CFD computations. The non-deterministic solution provides probabilistic definitions for disc temperatures and blade tip clearances, as key parameters in the design of the component. Whilst CFD has found increasing use in gas turbine air system R&D and design applications, resource requirement has almost always limited its use to deterministic single-input single-output cases. Here, by employing efficient uncertainty quantification based on Polynomial Chaos Methodologies to CFD, the air mass flow and temperature feed to the cavity are treated as operational uncertainty sources. Both single variable and multi-variable sources are considered. The CFD-FE link is established through a Temperature Influence Coefficient methodology and in propagating and managing the uncertainties through both analyses, means and standard deviations in the key design parameters are derived. The value of such a methodology in contrast to deterministic calculations is discussed from the view point of the designer with reference to component temperatures and thermal growths.
Chemical Looping Combustion Using the Direct Combustion of Liquid Metal in a Gas Turbine Based Cycle
Authors: McGlashan Niall R. , Childs Peter R. N. , Heyes Andrew L.
Published: January 2011

A combined cycle gas turbine generating power and hydrogen is proposed and evaluated. The cycle embodies chemical looping combustion (CLC) and uses a Na based oxygen carrier. In operation, a stoichiometric excess of liquid Na is injected directly into the combustion chamber of a gas turbine cycle, where it is burnt in compressed O2 produced in an external air separation unit (ASU). The resulting combustion chamber exit stream consists of hot Na vapour, and this is expanded in a turbine. Liquid Na2O oxide is also generated in the combustion process, but this can be separated, readily, from the Na vapour and collects in a pool at the bottom of the reactor. To regenerate liquid Na from Na2O, and hence complete the chemical loop, a reduction reactor (the reducer) is fed with three streams: the hot Na2O from the oxidiser; the Na vapour (plus some entrained wetness) exiting a Na-turbine; and a stream of solid fuel, which is assumed to be pure carbon for simplicity. The sensible heat content of the liquid Na2O and latent and sensible heat of the Na vapour provide the heat necessary to drive the endothermic reduction reaction and ensure the reducer is externally adiabatic. The exit gas from the reducer consists of almost pure CO which can be used to generate by-product H2 using the water-gas shift reaction. A mass and energy balance of the system is conducted assuming reactions reach equilibrium. The analysis allows for losses associated with turbomachinery; heat exchangers are assumed to operate with a finite approach temperature; however, pressure losses in equipment and pipework are assumed negligible — a reasonable assumption for this type of analysis that will still yield meaningful data. The analysis confirms that the combustion chamber exit temperature is limited by both first and second law considerations to a value suitable for a practical gas turbine. The analysis also shows that the overall efficiency of the cycle, under optimum conditions and taking into account the work necessary to drive the ASU, can exceed 75%.
Aero-Structural Optimization of an Axial Turbine Stage in Three-Dimensional Flow
Authors: Sivashanmugam Vadivel K. , Arabnia Mohammad , Ghaly Wahid
Published: January 2011

This paper presents a simple, effective and practical shape optimization approach for axial turbine stages so as to minimize the three-dimensional flow losses and simultaneously improve the turbine structural properties. The main objectives of the optimization are to maximize the stage efficiency and simultaneously minimize the von Mises stress while constraining the design mass flow rate and the blade first natural frequency. The stacking curve, which controls three-dimensional flow effects and the spanwise stress distribution is parametrically represented by a quadratic rational Bezier curve (QRBC). The parameters of this QRBC are related to the design variables namely the blade lean, sweep and bow. The optimization method combines a Multi-Objective Genetic Algorithm (MOGA), with a Response Surface Approximation (RSA) of the Artificial Neural Network (ANN) type. During the optimization process, each objective function and constraint is approximated by an individual ANN, which is trained and tested using an aerodynamic as well as a structure database composed of a few high fidelity flow simulations (CFD) and structure analysis (CSD) that are obtained using AN-SYS Workbench 2.0. This methodology was then applied to the aero-structural optimization of the E/TU-3 turbine stage at design conditions and proved quite successful, flexible and practical, and resulted in an 0.8% improvement in stage efficiency and about 50% reduction in the maximum von Mises stresses. This improvement was accomplished with as low as five design variables, which is remarkable considering the problem complexity.
Technical and Economic Analysis of Biomass Integrated Gasification Combined Cycle
Authors: Lepszy Sebastian , Chmielniak Tadeusz
Published: January 2011

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relatively high energy efficiency. This article presents models and results of simulations of the gas steam cycles integrated with pressurized gasification using biomass as a feedstock. The model and simulations are preformed with Aspen Plus® computer program. The gas generator model consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. The systems used for study include high-temperature gas cleaning system and a simple gas turbine. The steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency for a system with different pressure ratio in a gas turbine, sensitive analysis of the impact of steam temperature and pressure in HRSG on energy efficiency. The economic analysis includes determination of the electricity price in Polish economic conditions.
Optimal Combined Cycle for CO2 Capture With EGR
Authors: Jonshagen Klas , Sipo¨cz Nikolett , Genrup Magnus
Published: January 2011

Most state-of-the-art natural gas fired combined cycle (NGCC) plants are triple-pressure reheat cycles with efficiencies close to 60 percent. However, with carbon capture and storage, the efficiency will be penalized by almost 10 percent units. To limit the energy consumption for a carbon capture NGCC plant, exhaust gas recirculation (EGR) is necessary. Utilizing EGR increases the CO2 content in the gas turbine exhaust while it reduces the flue gas flow to be treated in the capture plant. Nevertheless, due to EGR, the gas turbine will experience a different media with different properties compared to the design case. This study looks into how the turbo machinery reacts to EGR. The work also discusses the potential of further improvements by utilizing pressurized water rather than extraction steam as the heat source for the CO2 stripper. The results show that the required low-pressure level should be elevated to a point close to the intermediate-pressure to achieve optimum efficiency; hence one pressure level can be omitted. The main tool used for this study is an in-house off-design model based on fully dimensionless groups programmed in the commercially-available heat and mass balance program IPSEpro. The model is based on a GE 109FB machine with a triple-pressure reheat steam cycle.