bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulations of the Effects of Changing Fuel for Turbines Fired by Natural Gas and Syngas
Authors: Sabau Adrian S. , Wright Ian G.
Published: March 2009

Gas turbines in integrated gasification combined cycle (IGCC) power plants burn a fuel gas (syngas) in which the proportions of hydrocarbons, H2, CO, water vapor, and minor impurity levels may vary significantly from those in natural gas, depending on the input feed to the gasifier and the gasification process. A data structure and computational methodology is presented for the numerical simulation of a turbine thermodynamic cycle for various fuel types, air/fuel ratios, and coolant flow rates. The approach used allowed efficient handling of turbine components and different variable constraints due to fuel changes. Examples are presented for a turbine with four stages and cooled blades. The blades were considered to be cooled in an open circuit, with air provided from appropriate compressor stages. Results are presented for the temperatures of the hot gas, alloy surface (coating-superalloy interface), and coolant, as well as for cooling flow rates. Based on the results of the numerical simulations, values were calculated for the fuel flow rates, airflow ratios, and coolant flow rates required to maintain the superalloy in the first stage blade at the desired temperature when the fuel was changed from natural gas (NG) to syngas (SG). One NG case was conducted to assess the effect of coolant pressure matching between the compressor extraction points and corresponding turbine injection points. It was found that pressure matching is a feature that must be considered for high combustion temperatures. The first series of SG simulations was conducted using the same inlet mass flow and pressure ratios as those for the NG case. The results showed that higher coolant flow rates and a larger number of cooled turbine rows were needed for the SG case. Thus, for this first case, the turbine size would be different for SG than for NG. In order to maintain the original turbine configuration (i.e., geometry, diameters, blade heights, angles, and cooling circuit characteristics) for the SG simulations, a second series of simulations was carried out by varying the inlet mass flow while keeping constant the pressure ratios and the amount of hot gas passing the first vane of the turbine. The effect of turbine matching between the NG and SG cases was approximately 10°C, and 8 to 14% for rotor inlet temperature and total cooling flows, respectively. These results indicate that turbine-compressor matching, before and after fuel change, must be included in turbine models. The last stage of the turbine, for the SG case, experienced higher inner wall temperatures than the corresponding case for NG, with the temperature of the vane approaching the maximum allowable limit.
Comparative Investigation of Three Highly Loaded LP Turbine Airfoils: Part I — Measured Profile and Secondary Losses at Design Incidence
Authors: Zoric T. , Popovic I. , Sjolander S. A. , Praisner T. , Grover E.
Published: March 2009

At the 2006 ASME-IGTI Turbo-Expo, low-speed cascade results were presented for the midspan aerodynamic behaviour of a family of three highly loaded low-pressure (LP) turbine airfoils operating over a wide range of Reynolds numbers (25,000 to 150,000 based on the axial chord and inlet velocity), and for values of freestream turbulence intensity of 1.5% and 4%. All three airfoils have the same design inlet and outlet flow angles. The baseline cascade has a Zweifel coefficient of 1.08 and the two additional blade rows have values of 1.37. The new, more highly-loaded blade rows differ mainly in their loading distributions: one is front-loaded while the other is aft-loaded. The new front-loaded airfoil was found to have particularly attractive profile performance. Despite its exceptionally high value of Zweifel coefficient, it was found to be free of a separation bubble on its suction side at Reynolds numbers as low as 50,000, and this was reflected in very good profile loss behaviour. However, it was also noted in the earlier paper that the choice of a particular loading level and loading distribution would be influenced by more than its profile performance at design incidence. The present two-part paper extends the midspan aerodynamic comparison of the three airfoils to the secondary flow performance. The first part of the paper discusses both the profile and secondary flow performance of the three cascades at their design Reynolds number of 80,000 (or ∼ 125,000 based on exit velocity) for two freestream turbulence intensities of 1.5% and 4%. The secondary flow behaviour was determined from detailed flowfield measurements made at 40% axial chord downstream of the trailing edge using a seven-hole pressure probe. In addition to providing total pressure losses, the seven-hole probe measurements were also processed to give the downstream vorticity distributions. As has been found in other secondary flow investigations in turbine cascades, the present front-loaded airfoil showed higher secondary losses than the aft-loaded airfoil with the same value of Zweifel coefficient.
Clearance Effects on Centrifugal Compressor Characteristic and Stability
Authors: Yoon Yong Sang , Kang Shin Hyung , Song Seung Jin
Published: March 2009

The effects of impeller inlet tip clearance and diffuser width on centrifugal compressor characteristic and stability have been experimentally investigated in a centrifugal compressor with a vaneless diffuser. An increase in the impeller inlet tip clearance decreases the overall pressure rise across the compressor, mainly due to the tip clearance loss in the impeller. However, the effect of inlet tip clearance on diffuser pressure rise or compressor stability is weak. A decrease in the diffuser width significantly lowers the compressor pressure rise, especially at hight flow rates. At the component level, the impeller is insensitive to the diffuser width variation, and the pressure rise across the diffuser actually increases as diffuser width is decreased. Upon further investigation, it has been found that the overall compressor characteristic is strongly influenced by the region between the impeller exit and the diffuser inlet. Also, a decrease in the diffuser width delays stall inception by increasing the radial velocity of the flow in the diffuser. Thus, the stalling flow coefficient is more sensitive to the variation in the diffuser than the inlet tip clearance. In all cases, rotating stall consists of two or three cells rotating at about approximately one tenth of the compressor rotational speed. When the number of cells changes from three to two, the rotational speed drops. However, when the number of cells remains constant, the cells’ rotational speed increases as flow coefficient is lowered. All of these trends agree well with predictions from a new stability model developed by the first author.
Flow Field Analysis of Inlet Distortion in a Transonic Fan With Straight and Bowed Stator Blade
Authors: Sun Peng , Zhong Jingjun , Feng Guotai
Published: March 2009

The performance and stability of a fan in clean and distorted inlet flow can be improved through the use of bowed stator blades. Measurements between the blade rows in transonic and supersonic flow are too complex to provide any useful insights, so 3D flow simulations are required. In this paper, a time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan is carried out using “Fluent-parallel” in a parallel supercomputer. Two sets of simulations are performed. The first simulation focuses on a better understanding of inlet total pressure distortion effects on a transonic fan. The second set of numerical simulation aims at studying the improvements of fan performance made by bowed stator blades. Three aspects are contained in this paper. The first is about the distortion effects on characteristics of the fan stage with straight stator. The effects of bowed stator on fan performance with inlet distortion are demonstrated secondly. One hand bowed stator increases the loss in rotor. On the other hand, it reduces the flow loss in stator. Finally, the patterns of flow loss caused by total pressure distortion with straight/bowed stator are compared. The scale of vortex in stator induced by inlet total pressure distortion is weakened by bowed blades, which decreases the stator loss.
Identification of Rotordynamic Forces in a Flexible Rotor System Using Magnetic Bearings
Authors: Zutavern Zachary S. , Childs Dara W.
Published: March 2009

A method is presented for parameter identification of an annular gas seal on a flexible-rotor test rig. Dynamic loads are applied by magnetic bearings (MBs) that support the rotor. MB forces are measured using fiber-optic strain gauges (FOSGs) that are bonded to the poles of the MBs. In addition to force and position measurements, a finite element rotor model is required for the identification algorithm. The FE rotor model matches free-free characteristics of the test rotor. The addition of smooth air seals to the system introduces stiffness and damping terms for identification that are representative of reaction forces in turbomachines. Tests are performed to experimentally determine seal stiffness and damping coefficients for different running speeds and preswirl conditions. Stiffness and damping coefficients are determined using a frequency domain identification method. This method uses an iterative approach to minimize error between theoretical and experimental transfer functions. Test results produce seal coefficients with low uncertainties.
A New Approach Integrating CO2 Capture Into a Coal-Based Polygeneration System of Power and Liquid Fuel
Authors: Jin Hongguang , Gao Lin , Han Wei , Yan Jinyue
Published: March 2009

Reducing the energy penalty for CO2 Capture and Storage (CCS) is a challenge. Most of previous studies for CCS have been focused on power generation system. When CCS is included in the polygeneration system, a new methodology that jointly considering CCS and liquid fuel production should be introduced. In this paper, we proposed a new approach integrating CCS into a coal-based polygeneration system for power generation and methanol production: the syngas produced from the coal gasifier, without adjusting the composition (CO/H2 ratio) by shift reaction, is used to synthesis methanol directly. Moreover, the partial-recycle scheme, in which a part of unreacted gas is recycled back to the synthesis reactor, is adopted in the synthesis unit. Another part of unreacted gas is treated to remove CO2, and then is used as clean fuel for the power generation subsystem. Compared to the conventional CCS approaches adopted by the power generation systems, the new approach is mainly characterized by two features: firstly, the combination of the removal of the composition adjustment process and a partial-recycle scheme can not only reduces the energy consumption for methanol production, but also obtains a high concentration of COX (CO and CO2) in the unreacted gas; secondly, the CO2 is captured from the unreacted gas, instead of from syngas generated by the gasifier. Due to increment of COX concentration, the new approach can reduce the energy consumption for CO2 capture compared to conventional pre-combustion CO2 capture. In the conventional coal based IGCC systems, the thermal efficiency is around 34-36% for a case with CO2 capture and around 44% for a case without CO2 capture. However, with the innovative approach integrating CCS, the polygeneration system in this paper can achieve the equivalent thermal efficiency as high as 47% when 72% of CO2 is recovered, which provides a significant improvement for CO2 capture. It’s clearly that the new approach can increase the thermal efficiency, instead of incurring an energy penalty for CO2 capture. The results achieved in this study have provided a new methodology integrating CO2 capture into the polygeneration system, which reveals the different characteristics compared to power-generation system that has been overlooked by the previous studies.
Low-Cost Wound and Woven Composite Turbomachinery Design
Authors: Mu¨ller N. , Lindberg B. , Mouland M. , Holden N. , Lahiri A. , Wagenknecht B.
Published: March 2009

A novel design and manufacturing of light-weight high-strength composite impellers with integrated motor and bearing is introduced. It is based on winding or weaving endless fiber material on a commercially available winder. This concept may be applied for compressors, pumps, turbines, propellers, or jet propulsion devices (Fig. 1). By interweaving electrical motor components, constructions without a shaft, or shaft sealing are possible. Also, the active motor elements can be positioned outside of the fluid stream. Besides the low cost of construction, one of the main advantages to this design is the integration of electrical motors in the turbo-wheels. This allows for the easy implementation of multiple counter-rotating turbomachinery stages in not only axial configurations, but also mixed flow configurations as well. The integrated motors are typically variable speed motors.
Predicting the Performance of System for the Co-Production of Fischer-Tropsch Synthetic Liquid and Power From Coal
Authors: Wang Xun , Xiao Yunhan
Published: March 2009

A co-production system based on FT synthesis reactor and gas turbine was simulated and analyzed. Syngas from entrained bed coal gasification was used as feedstock of low temperature slurry phase Fischer-Tropsch reactor. Raw synthetic liquid produced was fractioned and upgraded to diesel, gasoline and LPG. Tail gas composed of unconverted syngas and F-T light component was fed to gas turbine. Supplemental fuel (NG, or refinery mine gas) might be necessary, which was dependent on gas turbine capacity, expander through flow capacity, etc. FT yield information was important to the simulation of this co-production system. A correlation model based on Mobil’s two step pilot plant was applied. This model proposed triple chain-length-dependent chain growth factors and set up correlations among reaction temperature with wax yield, methane yield, and C2-C22 paraffin and olefin yields. Oxygenates in hydrocarbon phase, water phase and vapor phase were also correlated with methane yield. It was suitable for syngas, iron catalyst and slurry bed. It can show the effect of temperature on products’ selectivity and distribution. Deviations of C5+ components yields and distributions with reference data were less than 3%. To light gas components were less than 2%. User models available to predict product yields, distributions, cooperate with other units and do sensitive studies were embedded into Aspen plus simulation. Performance prediction of syngas fired gas turbine was the other key of this system. The increase in mass flow through the turbine affects the match between compressor and turbine operating conditions. The calculation was carried out by GS software developed by Politecnico Di Milano and Princeton University. The simulated performance assumed that the expander operates under choked conditions and turbine inlet temperature equals to NG fired gas turbine. A “F” technology gas turbine was selected to generate power. Various cases were investigated so as to match FT synthesis island, power island and gasification island in co-production systems. Effects of CO2 removal/LPG recovery, co-firing, CH4 content variation were studied. Simulation results indicated that more than 50% of input energy was converted to electricity and FT products. Total yield of gasoline, diesel and LPG was 136g-155g/NM3(CO+H2). At coal feed 21.9kg/s, net electricity exported to grid was higher than 100MW. Total production of diesel and gasoline (and LPG) was 118,000 tons(134,000tons)/Year. Under economic analysis conditions assumed in this paper, co-production system was economic feasible. The after tax profits can research 17 million EURO. Payback times were ranged from 6-7 years.
Numerical Validations of Secondary Flows and Loss Development Downstream of a Highly Loaded Low Pressure Turbine Outlet Guide Vane Cascade
Authors: Hja¨rne Johan , Chernoray Valery , Larsson Jonas , Lo¨fdahl Lennart
Published: March 2009

In this paper 3D numerical simulations of turbulent incompressible flows are validated against experimental data from the linear low pressure turbine/outlet guide vane (LPT/OGV) cascade at Chalmers in Sweden. The validation focuses on the secondary flow-fields and loss developments downstream of a highly loaded OGV. The numerical simulations are performed for the same inlet conditions as in the test-facility with engine-like properties in terms of Reynolds number, boundary-layer thickness and inlet flow angles with the goal to validate how accurately and reliably the secondary flow fields and losses for both on- and off-design conditions can be predicted for OGV’s. Results from three different turbulence models as implemented in FLUENT, k-ε Realizable, kω-SST and the RSM are validated against detailed measurements. From these results it can be concluded that the RSM model predicts both the secondary flow field and the losses most accurately.
Thermodynamic Analysis and Possible Applications of the Integrated Pyrolysis Fuel Cell Plant (IPFCP)
Authors: Colantoni Simone , Corradetti Alessandro , Desideri Umberto , Fantozzi Francesco
Published: March 2009

Biomass and waste are generally considered as a very promising option for fossil fuel substitution and greenhouse effect reduction in a sustainable energy scenario. This paper examines the possible lay-out and performance of an innovative energy system based on the integration of a high temperature fuel cell with a pyrolysis reactor. The pyrolyzer converts biomass or solid waste into syngas, which is cleaned from impurities and feeds a Solid Oxide Fuel Cell (SOFC), operating at 1000°C. A combustor supplies the energy required for pyrolysis, burning the solid and liquid fraction of the pyrolysis yield, as well as the un-oxidized fuel leaving the cell anode. Literature data have been used for determining pyrolysis yield as a function of reactor temperature and evaluating its effect on the plant thermodynamic efficiency. The coupling of the system to a gas turbine using the fuel cell as its combustion chamber is also evaluated. Results show that very interesting efficiencies are obtainable in the 20%–30% range.
Multidisciplinary Analysis of a Complete Infrared Suppression System
Authors: Bettini Claudio , Cravero Carlo , Cogliandro Santo
Published: March 2009

The article presents the analysis of the fluid-dynamic performance of a complete infrared suppressor system for helicopter engines. Each component, modelled using 3D parametric CAD, has been investigated using both CFD and stress analysis software. The main results have been compared to available experimental data.
Sealing Technology: Rub Test Rig for Abrasive/Abradable Systems
Authors: Rathmann Ulrich , Olmes Sven , Simeon Alex
Published: March 2009

Performance and efficiency optimization is one of the major tasks in the turbo machinery industry. Therefore efforts for scientific and technical improvements focus on optimization and reduction of losses. Secondary losses are of major interest because of their parasitic character related to stage efficiency and power output. One of these losses is over tip leakage of blades. Common practice is a minimization of this clearance with abrasive/abradable combinations. With this technique the blade tip (abrasive material) can rub into its counterpart (heat-shield, abradable material on casings or liners) and therefore minimize the operating tip-clearance. This technology is well established in compressor and turbine engineering since many years [1]. Field experience shows that abrasive/abradable systems do not always work as intended. In some cases rubbing conditions are reversed so that the intended abradable cuts into the abrasive. Any benefit on operating tip-clearance will then be minor at best or even negative. Rubbing behavior is difficult to predict, especially for new materials or geometries where no experience is available. In close cooperation with the University of Applied Sciences Rapperswil (Switzerland), ALSTOM has developed a test rig that allows simulating engine-operating conditions and therefore evaluate abrasive/abradable combinations before actual implementation into an engine. The rig is designed to reproduce circumferential velocities and incursion rates that are typical for gas turbine engines in the compressor as well as in the turbine. Forces and temperatures are measured as quantitative data, visual appearance and metallographic condition of test specimens are recorded as qualitative data that allow a more detailed assessment of material combinations and operating conditions. This paper describes the design of a high-speed wear rig facility to test single blade and fully shrouded rub configurations. In addition the validation of the test rig against real engine experience and knowledge is shown.
Effect of Length on Compressor Inter-Stage Duct Performance
Authors: Ortiz Duen˜as C. , Miller R. J. , Hodson H. P. , Longley J. P.
Published: March 2009

This paper describes the effect of reducing the length of a plain S-shaped compressor inter-stage duct on its performance. The investigation is aimed at understanding the physical mechanisms that determine the flow within these ducts and to assess the effect of these mechanisms in the overall duct performance. An experimental and computational investigation on the development of the boundary layers and loss generation within a datum duct (100% length) was performed. These results were used to design two S-shaped ducts with 74%, and 64% duct length of those currently used as inter-stage ducts. The duct designs were optimised for minimum stagnation pressure loss using a one degree-of-freedom design methodology. Using the duct with lengths 100%, 74% and 64% of current inter-stage ducts, an experimental investigation on the effect of duct length on the development of the boundary layers and loss generated was performed. As the duct length was reduced the loss increases mainly due to boundary layer separation. The size of the separations was found to be strongly dependant on Reynolds number. The results show that at the Reynolds numbers tested relaminarization of the boundary layer may have occurred upstream of separation.
Dynamic Analysis of a Geared Rotor-Bearing System With Viscoelastic Supports Under the Bow Effect
Authors: Shiau T. N. , Lee E. K. , Young T. H. , Hsu W. C.
Published: March 2009

This paper investigates the dynamic behaviors of a geared rotor-bearing system mounted on viscoelastic supports under considerations of the gear eccentricity, excitation of the gear’s transmission error and the residual shaft bow. The finite element method is used to model the system and Lagrangian approach is applied to derive the system equations of motion. The coupling effect of lateral and torsional motions is considered in the system dynamic analysis. The investigated dynamic characteristics include system natural frequencies and steady-state response. The results show that the mass, the stiffness and the loss factor of the viscoelastic support will significantly affect system critical speeds and steady-state response. Larger loss factor and more rigid stiffness of the viscoelastic supports will suppress the systematic amplitude of resonance. Parameters, which include magnitude of the residual bow and phase angle, are also considered in the investigation of their effects on system critical speeds and steady-state response. Results show that they have tremendous influence on first critical speed when the geared system mounted on stiff viscoelastic supports. The transmission error of the gear mesh is assumed to be sinusoidal with tooth passing frequency and it will induce multiple low resonant frequencies in the system response. It is observed that the excited critical speed equals to the original critical speed divided by gear tooth number.
Multi-Objective Optimization of a Microturbine Compact Recuperator
Authors: Micheli Diego , Pediroda Valentino , Pieri Stefano
Published: March 2009

An automatic approach for the multi-objective shape optimization of micro gas turbine heat exchangers is presented. According to the concept of Multi Disciplinary Optimization (MDO), the methodology integrates a CAD parametric model of the heat transfer surfaces, a three dimensional meshing tool and a CFD solver, all managed by a design optimization platform. The repetitive pattern of the surface geometry has been exploited to reduce the computational domain size, and constant flux boundary conditions have been imposed to better suit the real operative conditions. A new approach that couples cold and warm fluids in a periodic unitary cell is introduced. The effectiveness of the numerical procedure was verified comparing the numerical results with available literature data. The optimization objectives are maximizing the heat transfer rate and minimizing both friction factor and heat transfer surface. The paper presents the results of the optimization of a 50 kW MGT recuperator. The design procedure can be effectively extended and applied to any industrial heat exchanger application.
Design of the High Pressure Ratio Transonic 1-1/2 Stage Fan Demonstrator Hulda
Authors: Ma˚rtensson Hans , Burman Jo¨rgen , Johansson Ulf
Published: March 2009

As the first design in a demonstration program for future fighter engine fans a 400 mm 1-1/2 stage fan has been designed and built. A new method including mechanical constraints for designing the blades and gas path is used for the first time on a new design. The approach closely integrates CFD for performance and FE methods for the structure. By this, advanced computational analyses affect the design from the early stages. A design that is successful in achieving good efficiency based on CFD as well as reasonable aeromechanical properties based on FE is derived. The fan incorporates a front frame (FF), variable inlet guide vane (VIGV), rotor 1 (R1) and stator 1 (S1).
Impedance Tuning of a Premixed Combustor Using Active Control
Authors: Bothien Mirko R. , Moeck Jonas P. , Paschereit Christian Oliver
Published: March 2009

In early design phases new burner concepts are mostly tested in single or multi burner test rigs. These test rigs generally exhibit a different acoustic behavior than the full scale engine. The acoustic behavior, however, is crucial to predict whether thermoacoustic instabilities are likely to occur. Tuning the test rig’s acoustic boundary conditions to that of the engine could overcome this issue. Through this, an effective assessment of new burners is possible even in early design phases. In this work a method is proposed, which uses an active control scheme to manipulate the acoustic boundary conditions. It is applied to an atmospheric combustor test rig with a swirl-stabilized burner. In a first step it is shown that the acoustic boundary conditions can be controlled in the cold flow case. Almost arbitrary frequency dependent impedances can be prescribed ranging from fully reflecting (both pressure and velocity node) to anechoic. In particular, an additional virtual length can be added to the combustor outlet by manipulation of the reflection coefficient’s phase. This introduces resonance frequencies different from those of the uncontrolled case. In a second step the impedance tuning concept is applied to the reacting flow. It is demonstrated that the concept is feasible despite the harsh environmental conditions in a combustion chamber. The effect of different levels of reflection at the combustion chamber outlet on the combustion process is investigated. In addition to that, a study of the influence of the simulated combustor length on the system’s resonance frequencies is conducted.
3D Inverse Design of Transonic Fan Rotors Efficient for a Wide Range of RPM
Authors: Mileshin Victor I. , Orekhov Igor K. , Shchipin Sergey K. , Startsev Andrew N.
Published: March 2009

Present paper contains application of inverse problem for 3D Navier-Stokes equations to design turbomachinery bladed rows. In-house software package used to solve 3D inverse problem is named 3D-INVERSE.EXBL. Inverse problem is based on desired static pressure distribution on suction side of blade, given blade thickness and pressure difference (named loading) in corresponding points of suction and pressure sides of blade. Inlet and outlet gas-dynamic parameters (pressure, density and flow velocity vector) are taken from direct solution of flow within multistage compressor and remains unchanged during inverse problem solution. Solution of inverse problem is determined using moving grid. Normal speed of face of grid cell adjacent to blade surface is determined using given static pressure (inverse mode) with the aid of relationships which are the elements of Godunov scheme applied for integration of flow equations. In the paper inverse solution provides effectiveness and operability of first rotor of multistage low pressure compressor (LPC) for a wide range of rpm (70 ± 100%) in case of absence of inlet guide vane (IGV).
Design and Test Program in the Development of a 100 HP Oil-Free, High-Speed Blower
Authors: Walton James F. , Heshmat Hooshang , Tomaszewski Michael J.
Published: March 2009

This paper describes the design procedures and testing program in the development of a 100 HP single shaft permanent magnet motor driven centrifugal compressor/blower using compliant foil bearings. The development program included design tradeoff studies assessing motor rotor and bearing configurations, selection of the compressor/blower, and design of the system thermal management system. This paper also describes the first portion of the test program to assess dynamics, thermal management of the system and testing to assess compressor blower flow and pressure performance up to the 50 HP level. This program demonstrates the successful integration of oil-free foil bearings, 4-pole composite wound permanent magnet motor, thermal management capabilities and a state of the art centrifugal compressor.
RANS Evaluations of Internal Cooling Passage Geometries: Ribbed Passages and a 180 Degree Bend
Authors: Walker David , Zausner Jack
Published: March 2009

A comprehensive study and assessment of RANS based turbulence models is performed on internal cooling duct passages of turbine blades. Conjugate computational heat transfer studies of 90 and 45 degree turbulated ducts are performed and compared to experimental data from the Von Karmon Institute. Spatially resolved Nusselt number distributions are computed using CFX in conjunction with several RANS based turbulence models. In addition, similar computational studies of a 180 degree turnaround bend are performed and compared to experimental data from Arizona State University. In that experiment, area averaged Nusselt numbers are provided at different locations throughout a 180 degree turn around bend. For both analyses, the experimental data sets are carefully chosen as the original authors/experimentalists clearly identified the geometry and boundary conditions such that there was no ambiguity for CFD analysis. For the 90 degree turbulator orientation, it was found that most two equation models largely under predicted heat transfer levels. For the 45 degree turbulator configuration, it was found that a new SST based turbulence formulation, provided by CFX, adequately matched the experimental data. For the 180 degree turnaround bend, Nusselt numbers were well predicted by this new formulation. For all geometries analyzed, resorting to a particular higher moment closure model inside of CFX provided no extra benefit in terms of accuracy.
Novel Solid Fuel Gasification Power Plant for In Situ CO2 Capture
Authors: Kakaras E. , Koumanakos A. K. , Klimantos P. , Doukelis A. , Koukouzas N. , Giannakopoulos D.
Published: March 2009

The work presented in this paper aims to examine and analyse a novel concept dealing with the carbonation-calcination process of lime for CO2 capture from coal-fired power plants. The scheme is based on a novel steam gasification process of low rank coals with calcined limestone where in-situ CO2 capture and steam reforming are performed in a single reactor. CO2 is separated reacting exothermically with CaO based sorbents, providing also the necessary heat for the gasification reactions. The produced gas is a H2-rich gas with low carbon or near zero carbon content, depending on the ratio of lime added to the process. The produced fuel gas can be used in state-of-the-art combined cycles where it is converted to electricity, generating almost no CO2 emissions. After being captured in the gasification process, CO2 is released in a separate reactor where extra energy is provided through the combustion of low rank coal. Regenerated CaO is produced in this reactor and is continuously recycled within the process. The key element of the concept is the high-pressure steam gasification process where CO2 is captured by CaO based sorbents and fuel gas with high hydrogen content is produced, without using additional shift reactors. Two optimised power plant configurations are presented in detail and examined. In the first case, pure oxygen is utilised for the low rank coal combustion in the limestone regeneration process, while in the second case fuel is combusted with air instead. Results from the equilibrium based mass balance of the two reactors as well as the power plant thermodynamic simulations, dealing with the most important features for CO2 reduction are presented concerning the two different options. The energy penalties are quantified and the power plant efficiencies are calculated. The calculated results demonstrate the capability of the power plant to deliver decarbonised electricity while achieving high overall electrical efficiencies, comparable to other technological alternatives for CO2 capture power plants. The Aspen Plus software is used for the equilibrium based mass balance of the gasifier and the regenerator while the combined cycle power plant cycle calculations are performed with the thermodynamic cycle calculation software ENBIPRO (ENergie-BIllanz-PROgram), a powerful tool for heat and mass balance solving of complex thermodynamic circuits, calculation of efficiency, exergetic and exergoeconomic analysis of power plants [1].
Experimental Investigation Into Windage Power Loss From a Shrouded Spiral Bevel Gear
Authors: Johnson Graham , Simmons Kathy , Foord Colin
Published: March 2009

In some aero-engine applications a spiral bevel gear is mounted in a bearing chamber. The windage power losses (WPL) associated with the gear make a significant contribution to the overall heat generation within the bearing chamber and a potential method of WPL reduction and lubrication/cooling oil management is to shroud the gear. At the University of Nottingham Technology Centre in Gas Turbine Transmission Systems experimental and computational techniques are being applied to enhance understanding of shroud performance and design. This paper presents results from the first stage of the investigation in which the windage losses associated with rotating an unmeshed spiral bevel gear in air have been studied. The potential to reduce gear WPL by shrouding is clearly demonstrated with the WPL for the shrouded gear reduced on average by 75% for clockwise rotation and by 70% for anticlockwise rotation. Given the physical similarity between a shrouded gear and a centrifugal fan an attempt was made to characterize the performance of the shrouded gear in a similar manner to that used for a centrifugal fan i.e. as a function of the mass flow rate of air flowing through the shroud. It is demonstrated that in many aspects the gear performance was analogous to centrifugal fan behavior. It is further demonstrated that fan design approaches could be adopted to inform the detail of the shroud design and to translate test rig performance to different operating conditions.
Heat Transfer Around Longitudinal and Parallel Arranged Wedge-Shaped Vortex Generators
Authors: Henze Marc , Dietz Christopher , von Wolfersdorf Jens , Weigand Bernhard
Published: March 2009

In order to enhance convective heat transfer, turbulence promoters or vortex generators (VGs) are often used to manipulate the flow field and to benefit from their effect on thermal performance. The current investigation is directed towards a detailed understanding of the generated vortex flows and their impact on heat transfer for wedge shaped full-body VGs in internal flows. The main focus is on longitudinal and parallel arrangements of two or three VGs, where interaction of the induced flow field plays an important role. A single VG introduces a main vortex pair moving longitudinally downstream which is symmetric to the mid-plane of the turbulator itself. By using arrangements of several VGs it is possible to take advantage of the vortex interaction and define or deflect zones of enhanced heat transfer. In certain cases (e.g. due to manufacturing reasons) sharp edges on the elements cannot be realized. The effect of this discrepancy in the designated geometry is also investigated. Data for heat transfer behind a sharp-edged VG is compared with data for VGs manufactured with two different edge radii. In the present experimental setup the VGs are mounted on the bottom wall of a rectangular channel. For Reynolds numbers of 150,000 up to 550,000 the heat transfer coefficient is measured with the transient thermochromic liquid crystal (TLC) thermometry which is based on the measurement of the wall temperature response to a given step change in the fluid temperature. Numerical simulations using a Reynolds-Stress Model describe the flow field around the arrangements and are used for further interpretation of the experimental heat transfer distributions. Effects of vortex interactions on the heat transfer distribution are described for parallel and longitudinal arrangements. In the experimental data for elements with rounded edges a significant reduction in heat transfer can be observed.
Design for Six Sigma: The First 10 Years
Authors: Gardner Martha , Wiggs Gene
Published: March 2009

Six Sigma was launched at GE in 1995 by Jack Welch as a systematic way of improving the quality of delivered products and reducing cost across the entire Corporation. Soon after the first wave of Master Black Belts returned from their initial training, it was obvious that GE needed a “version” of Six Sigma adapted by a Design Engineering community that was focused on achieving specific goals of improved product performance, reliability and producibility while achieving a simultaneous reduction in the design cycle time for new products. The purpose of this paper is to share our lessons learned in adapting Six Sigma to the needs of the Design Engineering Community.
Reliability Prediction of Monolithic Structural Ceramics With Uncertainties
Authors: Luo X. , Srinivasan G. V. , Tredway W. K.
Published: March 2009

Reliability prediction of monolithic structural ceramics involves stress analysis through Finite Element Analysis (FEA) and a probability of failure prediction code such as CARES that considers the strength of ceramics as a statistical (Weibull) distribution. Though the strength is considered as a statistical distribution, stress in a given volume or surface element is discrete in current practice. However, uncertainties in FEA input such as material properties or boundary conditions make the predicted stress uncertain, thereby resulting in predicted reliability being uncertain as well. A probabilistic framework has been developed for reliability prediction to estimate component reliability by treating the uncertainties in loading, boundary conditions, and material properties as random variables. The framework consists of an automated, closed loop process integrating algorithms for assessing failure probability due to general randomness. Efficient and accurate computational methods for reliability analysis have been implemented in the framework for significant savings in computation time. The methodology is demonstrated on a gas turbine component. The analysis shows that reliability is compromised significantly by a design based on mean values of the random parameters, while an overly conservative design based on a worst case scenario will result in rejection of too many components at unnecessarily high proof test loads. This method ultimately leads to the determination of an optimum proof test level to assure component reliability amidst several sources of uncertainties in reliability prediction.
Development of Graded-Architecture Mullite Thermal Barrier Coating on Mo-Si-B Turbine Materials
Authors: Jackson Joshua E. , Lasseigne-Jackson Angelique N. , Koenig Travis , Olson David L. , Mishra Brajendra
Published: March 2009

A unique organic electrodeposition technique has been developed which allows rapid, smooth, and consistent coating application at low temperatures, low voltages, and with no pollutants. Precursor coatings of Aluminum, Al-Si, and Al-Mullite have been applied to Mo-Si-B turbine materials through immersion deposition and organic electrolytic cathodic deposition in an ionic liquid. These coatings were applied in protective atmosphere boxes and followed by low-temperature annealing to create a graded precursor layer. A graded precursor layer is desirable to minimize thermal shock, improve adhesion and achieve oxidation protection. The reactions across the interface region were characterized to assist in creation of the proper graded precursor layers for mullite formation. The optimal coating deposition method and composition has been assessed. High-temperature oxidation is being performed to form graded corrosion-resistant mullite thermal barrier coatings. The optimum deposition, annealing, and oxidation parameters will be characterized to achieve the proper thickness and compositional gradient of the thermal barrier coating. Coatings with various compositions and compositional gradients in the Mo-Si-B substrate and mullite layer are being assessed in a high-temperature simulated burner environment. Additional protective layers, such as barium-strontium-alumino-silicate (BSAS) are being developed to extend service life.
Generic Airplane and Aero-Engine Simulation Procedures for Exhaust Emission Studies
Authors: Shakariyants Savad A. , van Buijtenen Jos P. , Visser Wilfried P. J. , Tarasov Alexander
Published: March 2009

The paper presents generic simulation procedures for air-planes and aero-engines to support in-flight exhaust emission studies. They take a detailed account of the vehicle aerodynamics and performance as well as engine performance during typical flight missions. The procedures are coupled via lookup tables containing engine data for standard thrust settings. The models and their applicability to emission analysis were tested in a case study for a long-haul airliner with two large turbofans. The Boeing Method 2 fuel flow methodology [1] was selected as a test pollutants model. CO2 and H2O were found by directly linking them to the fuel flow via constant emission indexes. The case study first proved the accuracy of the airplane and engine models by matching available validation data. Secondly, it demonstrated the possibilities of evaluating exhaust emissions at different segments of a flight mission. Both emission profiles and the cumulative environmental footprint of the mission were estimated. The paper concludes by applying the models for the analysis of engine exhaust under varying flight conditions and engine deterioration. This can be used as a tool for optimizing operational procedures for emission reduction and assessing the environmental performance of an aging fleet.
Development of Highly Efficient Nuclear HP Steam Turbines Using Physics Based Moisture Loss Models
Authors: Guo T. , Sumner W. J. , Hofer D. C.
Published: March 2009

Turbines operating under wet steam conditions experience efficiency losses caused by the presence of moisture. A full understanding of these loss mechanisms is required for an accurate prediction of turbine performance. However, due to the extremely complicated nature of the wet steam flow, full numerical simulations are time consuming and expensive and have limited value for the turbine designers. The traditional empirical approach, though simple, generally offers no insight into the moisture loss mechanisms. As a result, little guidance is provided for design improvements. This paper presents a physics-based moisture loss prediction system that has been developed specifically for industrial applications. Three main categories of moisture losses are considered: homogeneous nucleation, thermodynamic (supersaturation) loss and mechanical loss. Two new correlations have been developed that provide a quick means for determining the Wilson Point location, resulting equilibrium moisture deficit and average size and number of the condensed moisture (fog). The thermodynamic losses produced by the non-equilibrium expansion of the wet steam beyond the Wilson Point are modeled using Young’s semi-analytical approach [23]. The mechanical moisture losses are modeled using the myriad of loss models available from the public domain. The combination of this new moisture loss model with existing steam path design tools has greatly improved our understanding of the moisture loss that occurs in wet steam expansions. In particular, it has provided significant insight into flow path design optimization for nuclear high pressure (HP) turbines. As a result, a new design methodology, Nuclear HP Dense Pack™, has been developed for the nuclear HP turbines. Preliminary results have shown this new design methodology has the capability of improving the section efficiency of existing nuclear HP steam turbines by 2-4% points.
Wedge Damper Modeling and Forced Response Prediction of Frictionally Constrained Blades
Authors: Cigeroglu Ender , An Ning , Menq Chia-Hsiang
Published: March 2009

In this paper, an improved wedge damper model is presented, based on which the effects of wedge dampers on the forced response of frictionally constrained blades are investigated. In the analysis, while the blade is modeled as a constrained structure, the damper is considered as an unconstrained structure. The model of the damper includes six rigid body modes and several elastic modes, the number of which depends on the excitation frequency. In other words, the motion of the damper is not artificially constrained. When modeling the contact surfaces of the wedge damper, discrete contact points along with contact stiffness are evenly distributed on the two contact surfaces. At each contact point, contact stiffness is determined and employed in order to take into account the effects of higher frequency modes that are omitted in the dynamic analysis. Depending on the engine rpm, quasi-static contact analysis is initially employed to determine the contact area as well as the initial preload or gap at each contact point due to the centrifugal force. A friction model is employed to determine the three-dimensional nonlinear contact forces and the relationship between the contact forces and the relative motion is utilized by the Harmonic Balance method. As the relative motion is expressed as a modal superposition, the unknown variables, and thus the resulting nonlinear algebraic equations, in the Harmonic Balance method is in proportion to the number of modes employed, and therefore the number of contact points used is irrelevant. The developed method is applied to tuned bladed disk system and the effects of normal load on the rigid body motion of the damper are investigated. It is shown that, the effect of rotational motion is significant, particularly for the in-phase vibration modes.