bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Design of Gas Turbine Cogeneration Plants in Consideration of Discreteness of Equipment Capacities
Authors: Yokoyama Ryohei , Ito Koichi
Published: November 2008

To attain the highest economic and energy saving characteristics of gas turbine cogeneration plants, it is necessary to rationally determine capacities and numbers of gas turbines and auxiliary equipment in consideration of their operational strategies corresponding to seasonal and hourly variations in energy demands. Some optimization approaches based on the mixed-integer linear programming have been proposed to this design problem. However, equipment capacities have been treated as continuous variables, and correspondingly performance characteristics and capital costs of equipment have been assumed to be continuous functions with respect to their capacities. This is because if equipment capacities are treated discretely, the number of integer variables increases drastically, and the problem becomes too difficult to solve. As a result, the treatment of equipment capacities as continuous variables causes discrepancies between existing and optimized values of capacities, and expresses the dependence of performance characteristics and capital costs on capacities with worse approximations. In this paper, an optimal design method is proposed in consideration of discreteness of equipment capacities. A formulation for keeping the number of integer variables as small as possible is presented to solve the optimal design problem easily. This method is applied to the design of a gas turbine cogeneration plant, and its validity and effectiveness are clarified.
Conjugate Simulation of Flow and Heat Conduction With a New Method for Faster Calculation
Authors: Yamane Takashi , Yoshida Toyoaki , Enomoto Shunji , Takaki Ryoji , Yamamoto Kazuomi
Published: November 2008

A new conjugate simulation program for flow and heat conduction has been developed based upon a common CFD platform UPACS. It connects flow calculation blocks and solid blocks without using surface temperature values explicitly. The time-lag between flow simulation and heat conduction calculation which is a severe problem in conjugate heat transfer has been improved by introducing a heat conduction sub-step method. The developed program has been applied to simulations of new turbine cooling structures which are the integration of impingement and pin cooling device and revealed that the pin configuration changes the cooling efficiency.
Optimal Operational Planning of Cogeneration Systems With Microturbine and Desiccant Air-Conditioning Units
Authors: Gamou Satoshi , Ito Koichi , Yokoyama Ryohei
Published: November 2008

Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant air-conditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning.
Effect of Hole Arrangements on Local Heat/Mass Transfer for Impingement/Effusion Cooling With Small Hole Spacing
Authors: Cho Hyung-Hee , Rhee Dong Ho , Goldstein R. J.
Published: November 2008

The present study investigates the local heat (mass) transfer characteristics of flow through perforated plates. Two parallel perforated plates placed, relative to each other, in either staggered, in-line or shifted in one direction. Hole length to diameter ratio of 1.5, hole pitch to diameter ratio of 3.0, and distance between the perforated plates of 1 to 3 hole diameters are used at hole Reynolds numbers of 3,000 to 14,000. For flows through the staggered layers and the layers shifted in one direction, the mass transfer rates on the windward surface of the second wall increase approximately 50% from impingement cooling alone and are about three to four times that with effusion cooling alone (single perforated plate). The high transfer rate is induced by strong secondary vortices formed between two adjacent impinging jets that are accelerated by the effusion flow. The overall transfer rate is dominated by the target (second) surface (approximately 50%) instead of the inside hole surface that is dominant with a single plate case. The transfer coefficient for the in-line layers is approximately 100% higher on the windward surface of the second wall than that of the single plate case. The transfer coefficient on the leeward surface for the second plate is affected little by upstream flow conditions.
Local Heat/Mass Transfer With Various Rib Arrangements in Impingement/Effusion Cooling System With Crossflow
Authors: Rhee Dong Ho , Nam Yong Woo , Cho Hyung Hee
Published: November 2008

The present study has been conducted to investigate the effect of rib arrangements on flow and heat/mass transfer characteristics for an impingement/effusion cooling system with initial crossflow. Two perforated plates of square hole array are placed in parallel and staggered arrangements with a gap distance of 2d and the crossflow passes between the injection and effusion plates. Both the injection and effusion hole diameters (d) are 10 mm and Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6d, respectively. Square ribs of various rib arrangements and attack angles are installed on the effusion plate. With the initial crossflow, locally low transfer regions are formed and the level of heat transfer rate become lower as flow rate of the crossflow increases because wall jets are swept and the stagnation regions are affected by crossflow. With rib turbulators, the flow and heat transfer patterns are changed because the ribs protect near-wall flows including wall jets and generate secondary flow in a duct. For M ≥ 1.0, the overall heat transfer is promoted when ribs are installed on the effusion surface, and higher values are obtained with smaller pitch of ribs. But, the attack angle of the rib has little influence on the average heat/mass transfer. For low blowing ratio of M = 0.5, the ribs have adverse effects on heat/mass transfer. Pressure drop between the inlet and exit of the channel increases up to 20% of total loss when ribs are installed while it is only 5% of total pressure loss across the perforated plates without ribs.
A Numerical Model for Oil Film Flow in an Aero-Engine Bearing Chamber and Comparison With Experimental Data
Authors: Farrall Mark , Simmons Kathy , Hibberd Stephen , Gorse Philippe
Published: November 2008

The work presented forms part of an on-going investigation, focusing on modelling the motion of a wall oil film present in a bearing chamber and comparison with existing experimental data. The film is generated through the impingement of oil droplets shed from a roller bearing. Momentum resulting from the impact of oil droplets, interfacial shear from the airflow, and gravity cause the film to migrate around the chamber. Oil and air exit the chamber at scavenge and vent ports. A previously reported numerical approach to the simulation of steady-state two-phase flow in a bearing chamber, that includes in-house sub-models for droplet-film interaction and oil film motion, has been extended. This paper includes the addition of boundary conditions for the vent and scavenge together with a comparison to experimental results obtained from ITS, University of Karlsruhe. The solution is found to be sensitive to the choice of boundary conditions applied to the vent and scavenge.
Feasibility of IGCC Technology for Power Generation in India
Authors: Reuben Benjamin
Published: November 2008

The paper evaluates the emerging coal gasification technology now operational in many parts of the world to produce electric power through Combined Cycle mode in the present coal dominated power scenario in India. The initiatives of United States Agency for International Development (USAID)-New Delhi, India together with an Indian utility National Thermal Power Corporation (NTPC) and supported by a consortium of experienced international agencies for feasibility study of commercial application of coal based IGCC technology for producing 100MWe in India are enumerated. India with a population of one billion, a fifth of the world’s population ranks sixth in the world in terms of energy demand. It has only about 0.4 percent of world’s natural gas which contributes only 10 percent to power generation as against 65% by coal in the present total installed capacity of 107000 MW. The estimated coal reserves in India of 211 billion tonnes are likely to last for about 150 years as against oil and gas reserves that will get depleted in less than 50 years. Notwithstanding the ongoing debate in India between LNG versus coal for emergence of a mature and economic future fuel for power generation in India, over 60% of the 100,000 MW power demand required in the next 10 years in India is expected to be provided on coal, USAID-New Delhi has commissioned under its expanded Green House Gas (GHG) Pollution Prevention Project, a feasibility study of the IGCC Power plant in India. Therefore, application of the coal gasification combined cycle process, an emerging technology for clean, efficient and low CO2 emission coal fuelled generation thro GE’s advanced H-system turbine and providing high operating efficiency of 43% would be appropriate to serve as a base technology for greenfield projects and as a repowering option for vintage coal fired plants totaling 25000 MW now operating over 30 years.
Chemical Kinetic Modelling of the Evolution of Gaseous Aerosol Precursors Within a Gas Turbine Engine
Authors: Clague A. R. , Wilson C. W. , Pourkashanian M. , Ma L.
Published: November 2008

A sequence of kinetic models has been developed to simulate the chemical processes occurring throughout the hot section of a modern gas turbine engine. The work was performed as part of the EU funded PARTEMIS programme, which was designed to investigate the effect of both engine condition and fuel sulphur content on the production of gaseous aerosol precursor such as SO3, H2SO4 and HONO. For the PARTEMIS programme, a Hot End Simulator (HES) was designed to recreate the thermodynamic profile through which the hot gases pass after leaving the combustor. Combustion rig tests were performed in which the concentrations of gaseous product species were measured at the exits of both the combustor and the HES. These measurements were used to validate the kinetic models. The combustor was modelled by a sequence of five perfectly stirred reactors, using the Combustor Model Interface (CMI) developed at the University of Leeds. The CMI allows for the addition of dilution air at each stage of the combustor as well as re-circulation between each stage. The results at the combustor exit were then used as initial boundary conditions for the HES model, which followed the evolution of reacting gases through each of the pressure stages of the HES. This combination of the two models allowed the chemistry occurring throughout an engine, from combustor inlet to turbine exit, to be simulated. The principal aim of this modelling programme was to determine the extent of conversion of the sulphur (IV) species, SO2, to the sulphur (VI) species, SO3 and H2SO4. The predicted level of this conversion at the exit of the HES was found to be in very good agreement with the experimentally measured values. These values were lower than had been previously determined by modelling studies and this was found to result from changes made to the thermodynamic properties of the key intermediate, HOSO2, following recent experimental measurements. The results also showed that for these tests, the predominant sulphur conversion process occurred within the combustor itself rather than the turbine or beyond.
Influence of Operating Condition and Geometry on the Oil Film Thickness in Aero-Engine Bearing Chambers
Authors: Gorse P. , Busam S. , Dullenkopf K.
Published: November 2008

Increasing the efficiency of modern jet engines do not only imply to the mainstream but also to the secondary air and oil system. Within the oil system the bearing chamber is one of the most challenging component. Oil films on the chamber walls are generated from oil droplets, ligaments, or film fragments, which emerge from bearings, seal plates and shafts, and enter the bearing chamber with an angular momentum. Furthermore, shear forces at its surface, gravity forces, and the design of scavenge and vent ports strongly impact the behavior of the liquid film. The present paper focuses on the experimental determination of the film thickness is various geometries of bearing chambers for a wide range of engine relevant conditions. Therefore, each configuration was equipped with five capacitive probes positioned at different circumferential locations. Two analytical approaches are used for a comprehensive discussion of the complex film flow.
Scaling of Stability Limits in Lean-Premixed Gas Turbine Combustors
Authors: Lohrmann Martin , Bu¨chner Horst
Published: November 2008

The prediction and the systematic suppression of self-sustained combustion instabilities in combustors for gas turbine applications still suffer from incomplete physical understanding of the feedback mechanisms and lack of experimental data of the dynamic flame characteristics of Lean-Premixed swirl flames. Hence, the experimental determination of the flame transfer functions of LP swirl flames was achieved using a mixing unit to generate a time-independent and spatial homogeneous mixture of natural gas and combustion air at the burner exit. The determined LP flame dynamics are strongly affected by the formation and in-phase reaction of coherent vortex structures, well known as drivers of combustion instabilities, that have been visualized with an phase-correlated imaging technique. The results discussed in this paper lead to a basic understanding of the frequency-dependent dynamics of LP swirl flames on periodic disturbances and especially, of the influence of the preheating temperature and the air equivalence ratio on the amplitude responses and phase angle functions. Based on the measurements and theoretical considerations concerning the burning velocity of steady-state premixed flames a physical model and — derived from it — scaling laws for the prediction of unstable operation modes in dependence of main operation parameters of the flame were formulated and validated by measurements.
LES of Swirling Flows in Gas Turbine Combustion Chambers
Authors: Gherman Bogdan , Szasz Robert-Zoltan , Fuchs Laszlo
Published: November 2008

The flow and mixing in a swirl-stabilized gas-turbine burner is studied by Large Eddy Simulations (LES). Each swirler has a different mass flux and swirl angle. The interaction between neighbouring jets is studied, co-rotating and counter rotating jets are considered. Another issue of importance is related to the jet inlet conditions (e.g. axial distribution and levels of turbulence). In addition to the flow field (using LES) we present results related to fuel/air mixing under different conditions. We show that the LES results can resolve several issues related to the burner that cannot be accounted for by the standard RANS computations.
Transient Analysis of Solid Oxide Fuel Cell Hybrids: Part B — Anode Recirculation Model
Authors: Ferrari Mario L. , Traverso Alberto , Massardo Aristide F.
Published: November 2008

The aim of this work is the transient analysis of hybrid systems based on high-temperature Solid Oxide Fuel Cells (SOFC). The cell models were presented and discussed in Part A of this work. In this part attention is focused on the anode recirculation system. In a SOFC hybrid system it is necessary to recirculate part of the exhaust gas in order to maintain a proper value for the Steam-To-Carbon Ratio and to support the reforming reactions. This is carried out with an ejector, which exploits the pressure energy of the fuel to recirculate part of the anodic exhausts to fuel cell anodic side. Initially, a “dynamic” stand-alone ejector model is presented and validated for the analysis of unsteady flows. Particular attention was paid to the effect of time variation in the mixture composition, creating a general model for the unsteady simulation of flows with variable composition. To analyze the whole anodic circuit the “dynamic” model was simplified to the “lumped volume” model, which, even if it cannot properly analyze supersonic flows and shock waves, considerably reduces calculation time. So, it is suitable for transient system simulations, generally longer than a few minutes. The “lumped volume” model has been tested with the “dynamic” model and it has been used for the anodic recirculation system time-dependent simulations.
Thermal-Economic Evaluation of Evaporative Inlet Cooling Methods for Ray Gas Turbine Power Plant
Authors: Sanaye Sepehr , Farhad Abbasali , Ebrahimi Mohsen
Published: November 2008

The ambient conditions (temperature, pressure and humidity) affect the gas turbine power output and thermal efficiency [1–8]. Increasing one Celsius degree of ambient temperature decreases the power output for about 0.5 to 0.9 percent and the thermal efficiency for about 0.25 percent. Evaporating cooling is efficient and cost effective method for gas turbine inlet cooling to improve the power output and efficiency, specially in hot and dry regions. A systematic thermo-economic evaluation of the three evaporative inlet cooling methods applied to existing 25 MW Fiat gas turbine in Ray power plant, is presented in this paper. The three inlet cooling methods considered are: evaporative inlet fogging, media type evaporative cooling and inlet cooling through air washer. The investment and maintenance costs, the income from increasing the power output, the costs of increasing fuel consumption, and power loss due to pressure drops, were estimated and the payback periods for the mentioned evaporative inlet cooling methods were obtained and compared. The suitable evaporative cooling method for various operational conditions is proposed for 25 MW Fiat gas turbines.
Thermodynamic and Economic Investigation of an Improved Graz Cycle Power Plant for CO2 Capture
Authors: Sanz W. , Jericha H. , Moser M. , Heitmeir F.
Published: November 2008

Introduction of closed cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore research and development at Graz University of Technology since the 90’s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than 60%. In this work a further development, the S-Graz Cycle is presented, which works with a cycle fluid of high steam content. Thermodynamic investigations show efficiencies up to 70% and a net efficiency of 60% including the oxygen supply. For a 100 MW prototype plant the layout of the main turbo-machinery is performed to show the feasibility of all components. Finally, an economic analysis of a S-Graz Cycle power plant is performed showing very low CO2 mitigation costs in the range of 10 $/ton CO2 captured, making this zero emission power plant a promising technology in the case of a future CO2 tax.
IGCC System With Integration of CO2 Recovery and the Cryogenic Energy in Air Separation Unit
Authors: Wang Baoqun , Jin Hongguang , Han Wei , Zheng Danxing
Published: November 2008

In this paper, we proposed a new type of IGCC system with CO2 recovery, which employed the cryogenic energy of the air separation unit. The idea of integration of CO2 separation is introduced and the theoretical separation work was compared between the integration CO2 separation process and the traditional CO2 separation process. Different from the two-step (separation and compression) CO2 recovery processes commonly used, the new system can separate and liquefy CO2 simultaneously by means of integration of the cryogenic energy of air separation unit and CO2 recovery unit. In this way, a large amount of compression work can be reduced, compared with wet scrubbing processes to sequestrate the recovered CO2. The new integration system was compared with the amine absorption process. The result indicated that through energy integration between air separation and CO2 recovery, the energy consumption of CO2 separation is expected to be reduced by 28.4%, compared to the traditional amine absorption process. Based on the investigation, the paper make a contribution to provide a concept of integration of cold energy with CO2 separation for the purpose of increase in efficiency and mitigation of greenhouse gas impact.
A New Method to Calculate the Coolant Requirements of a High Temperature Gas Turbine Blade
Authors: Torbidoni Leonardo , Horlock J. H.
Published: November 2008

Earlier papers by the first author have described a computational method of estimating the cooling flow requirements of blade rows in a high temperature gas turbine, for convective cooling alone and for convective plus film cooling; this method of analysis and computation, when applied to the whole blade chord was compared with a well known semi-empirical method. In the current paper, a more sophisticated method is developed from the earlier work and is used to calculate the cooling flow required for a nozzle guide vane [the first blade row] of a high temperature gas turbine, with given inlet gas temperature and coolant inlet temperature. Now the heat flux through an elementary cross-sectional area of the blade, at given spanwise [y] and chordwise [s] locations, is considered, with a guessed value of the elementary coolant flow [as a fraction dΨ(s) of the external gas flow]. At the given s, integration along the blade length gives the blade metal temperatures at the outer and inner walls, Tbg[y] and Tbcl[y]. If the value of Tbg at the blade tip [y = H] is assumed to be limited by material considerations to Tbg,max then the elementary coolant flow rate may be obtained by iteration. Summation along the chord then gives the total coolant flow, for the whole blade. Results using the method are then compared with a simpler calculation applied to the whole blade, which assumes chordwise constant temperatures and constant selected values of cooling efficiency and film cooling effectiveness.
Surge Margin Tracking for Active Control of Quick Windmill Relighting
Authors: Kim Sog-Kyun , Griffin Ian A. , Thompson Haydn A. , Fleming Peter J.
Published: November 2008

Surge margin tracking logic is developed for use in the control of quick windmill relighting (QWR) at sub-idle. Using existing high pressure compressor (HPC) characteristics (but without any gas turbine engine model), the surge margin can be calculated and used to approximate the air flow which is currently not measured in flight. During the QWR flight test, only limited measurements excluding the airflow measurement are available. Based on the fact that a beta value is equivalent to the position of the throttle valve in a compressor test rig, the role of the beta value is here to interrelate between the PRC (pressure ratio of compressor) and NDMF (non-dimensional mass flow) values for the measured CNH (corrected high pressure spool speed) and PRC values. Using the proposed scaling factors (SFs), the HPC map in terms of PRC is adaptively scaled with the engine parameters to cover the operating pressure ratio of the HPC. These account qualitatively for the effects of heat soakage and stability aids such as bleed and VSV (variable stator vane) on the compressor map. The simulation results show that the variable SF approach is more realistic in estimation of the surge margin, compared to the fixed SF approach. As a result of this proposed surge margin tracking logic, an active control for QWR may be possible using an estimated surge margin to adjust the fuel flow. This improves the pull-away time to reach idle power without danger of stall or surge during QWR.
Improving Turbine Performance by Use of CFD
Authors: Sieros Giorgos , Kefalakis Michail , Papailiou Kyriacos D.
Published: November 2008

The design and testing of a small mixed flow turbine, which is part of the air-conditioning system of an aircraft, are described. The turbine has an expansion ratio of approximately 3:1 at a reduced mass flow rate of 0.5kg/s and a total-to-total isentropic efficiency very close to 90%, including the inlet scroll. The design methodology that was used is described and discussed. The experimental set up and the experimental results are also presented and the latter are compared to the theoretical calculations. Explanations are provided for the efficiency improvement that was achieved.
Steady-State/Transient Performance Simulation of the Propulsion System for the Canard Rotor Wing UAV During Flight Mode Transition
Authors: Kong Changduk , Kang Myoungcheol , Ki Jayoung , Park Jongha , Yang Sooseok
Published: November 2008

A steady-state/transient performance simulation model was newly proposed for the propulsion system of the CRW (Canard Rotor Wing) type UAV (Unmanned Aerial Vehicle) in various flight modes. The studying CRW type UAV has a new concept RPV (Remotely Piloted Vehicle) which can fly at two flight modes such as the take-off/landing and low speed forward flight mode using the rotary wing driven by the engine bypass exhaust gas and the high speed forward flight mode using the fixed wing and main engine thrust. The proposed propulsion system is consisted of the main engine system and the duct system. A flight vehicle may generally select the engine with a proper type and a specific model with acceptable thrust level to meet the flight mission in the propulsion system design phase. In this study, a turbojet engine with one spool was selected by decision of the vehicle system designer, and the duct system is composed of main duct, rotor duct, master valve, rotor tip nozzles, and variable main nozzle. In order to establish the safe operation of the propulsion system, performance simulation should be needed. In this study, a performance model of the Smart UAV propulsion system with ducts, tip jets and variable main nozzle, which has flight capability of the rotary wing mode for the take-off/landing and low speed forward flight as well as the fixed wing mode for high speed forward flight, has been newly developed. With the proposed model, steady-state performance analysis was performed at various flight modes and conditions, such as rotary wing mode, fixed wing mode, compound wing mode, altitude and flight speed. Through this analysis, it was confirmed that the engine performance simulation results without the duct system were well agreed with the engine manufacturer’s data, and the safe operation range of the proposed propulsion system was investigated at three flight modes. And the dynamic behavior of the system was modeled and simulated using the SIMULINK®.
Customized Profiles — The Beginning of an Era: A Short History of Blade Design
Authors: Lichtfuss Hanns-Juergen
Published: November 2008

The paper presents the evolutionary progress made in the design process of turbo machines from using standardized profiles — for turbine and compressor blades — towards individual profile designs. The emerging new power of numerical methods on continuously faster running electronic computers has made this progress possible. In addition there were regularly experimental verifications in cascade wind tunnels and turbo machinery test beds as well as applications of new design strategies. These strategies, i.e. naturally laminar flow in turbines and supercritical flow in compressors, also made use of reinvented inverse methods, as one tool to optimise problematic areas.
Secondary Flows and Loss Caused by Blade Row Interaction in a Turbine Stage
Authors: Pullan Graham
Published: November 2008

A study of the three-dimensional stator-rotor interaction in a turbine stage is presented. Experimental data reveal vortices downstream of the rotor which are stationary in the absolute frame — indicating that they are caused by the stator exit flowfield. Evidence of the rotor hub passage vortices is seen, but additional vortical structures away from the endwalls, which would not be present if the rotor were tested in isolation, are also identified. An unsteady computation of the rotor row is performed using the measured stator exit flowfield as the inlet boundary condition. The strength and location of the vortices at rotor exit are predicted. A formation mechanism is proposed whereby stator wake fluid with steep spanwise gradients of absolute total pressure is responsible for all but one of the rotor exit vortices. This mechanism is then verified computationally using a passive-scalar tracking technique. The predicted loss generation through the rotor row is then presented and a comparison made with a steady calculation where the inlet flow has been mixed out to pitchwise uniformity. The loss produced in the steady simulation, even allowing for the mixing loss at inlet, is 10% less than that produced in the unsteady simulation. This difference highlights the importance of the time-accurate calculation as a tool of the turbomachine designer.
Numerical Study of Roughness Effects on a Turbine Stage Performance
Authors: Kang Young-Seok , Yoo Jae-Chun , Kang Shin-Hyoung
Published: November 2008

Turbine performance deteriorations due to blade surface roughness were numerically estimated. Numerical calculations were carried out for a low speed, single-stage axial turbine with a commercial CFD code, CFX-Tascflow, using a modified wall function boundary condition for rough surfaces. Two equivalent sand-grain roughness heights of 106μm (transitionally rough regime) and 400μm (fully rough regime) were considered. Two performance variables, stage work coefficient and efficiency were compared with the measured data. The calculated results showed qualitatively good agreement with the measured data. The calculated and measured performance variables deteriorated as the roughness height increased. High roughness induced small changes in deviation angles of the stator and rotor. These changes in the deviation angles result in a noticeable reduction in the work coefficient. One dimensional analysis shows that the stator deviation angle is more sensitive to the work coefficient reduction. On the other hand, the stage efficiency reduction due to the roughness was accountable with an additional profile loss due to the roughness. Loss generation in the stator stage was approximately 10% higher than that of the rotor due to very high profile loss occurred on the suction surface trailing edge of the stator.
Experimental Analysis and Prediction of Wake-Induced Transition in Turbomachinery
Authors: Elsner Witold , Vilmin Stephane , Drobniak Stanislaw , Piotrowski Wladyslaw
Published: November 2008

The paper presents an experimental and numerical analysis of the interaction between wakes and boundary layers on aerodynamic blade profiles. The experiment revealed that incoming wakes interact with boundary layers and cause the significant increase of velocity fluctuations in the boundary layer and in consequence shift the transition zone towards the leading edge. The full time evolution of periodic wake induced transition was reproduced from measurements. The numerical simulation of the flow around the blade profile has been performed with the use of the adaptive grid viscous flow unNEWT PUIM solver with a prescribed unsteady intermittency method (PUIM) developed at Cambridge University, UK. The results obtained give evidence that the turbulence transported within the wake is mainly responsible for the transition process. The applied CFD solver was able to reproduce some essential flow features related to the bypass and wake-induced transitions and the simulations reveal good agreement with the experimental results in terms of localisation and extent of wake-induced transition.
Boundary Layer Suction via a Slot in a Transonic Compressor: Numerical Parameter Study and First Experiments
Authors: Hubrich K. , Bo¨lcs A. , Ott P.
Published: November 2008

In the present paper a numerical and experimental study aiming at the enhancement of the working range of a transonic compressor via boundary layer suction (BLS) is presented. The main objective of the investigation is to study the influence of BLS on the interference between shock wave and boundary layer and to identify the possible benefit of BLS on the compressor working characteristics. An extensive numerical study has been carried out for the DATUM blade and for 2 different suction location configurations for one speed line and varying back-pressure levels, ranging from choked conditions to stall. It was found that the working range of the transonic compressor with a nominal inlet Mach number of 1.2 and a nominal pre-shock Mach number of 1.35 could be increased by sucking 2% of flow on the SS away, in such a way that the maximum pressure ratio and maximum diffusion could both be increased by 10%, when compared to the DATUM case. For smaller pressure ratios with respect to the design pressure ratio, the BLS is located in a supersonic flow region and thus creates additional losses due to a more divergent flow channel, which additionally accelerates the flow and results in a higher pre-shock Mach number creating higher losses. First measurements carried out in LTTs annular cascade, do show reasonable agreement with the computations in terms of inlet Mach number, flow angle, main shock location and stall limit. The most pronounced difference between measurements and computations is the occurrence of a terminal normal channel shock behind a bowed detached shock wave and a separation on the SS of the blade, which were both not predicted by the CFD.
Measured Data Correction for Improved Fouling and Degradation Analysis of Offshore Gas Turbines
Authors: Veer Timot , Haglero̸d Klaus K. , Bolland Olav
Published: November 2008

The authors suggest a straightforward methodology to correct measurement data in order to facilitate condition assessment of gas turbines. After data being prepared as such, a considerable improvement in accuracy is obtained in regard to condition evaluation of the machine. Such methodology brings proven benefits when regarding the fouling problem as well as washing scheduling at sites where the fouling process is relatively slow, e.g. offshore applications. Analyses of other relatively slow performance loss processes, like degradation, are also targeted. The usefulness of the methodology is validated against field data by employing advanced software tools and reliability and availability as well as condition and lifing prediction.
An Application Oriented Gas Turbine Laboratory Experience
Authors: Van Treuren Kenneth W.
Published: November 2008

The gas turbine industry is experiencing growth in many sectors. An important part of teaching a gas turbine course is exposing students to the practical applications of the gas turbine. This laboratory proposes an opportunity for students to view an operating gas turbine engine in an aircraft propulsion application and to model the engine performance. A Pratt and Whitney PT6A-20 turboprop was run at a local airfield and engine parameters typical of cockpit instrumentation were taken. The students, in teams of two, then modeled the system using the software PARA and PERF in an attempt to match the manufacturer’s specifications. This laboratory required students to research the parameters necessary to model this engine that were not part of the data set provided by the manufacturer. The research and modeling encompassed areas such as technology level, efficiencies, fuel consumption, and performance. The end result was a two-page report containing the students’ calculations comparing the actual performance of the engine with the manufacturer’s specifications. Supporting graphs and figures were included as appendices. The same type laboratory could be adapted for co-generation gas turbines. Over 121 colleges and universities have co-generation facilities on campus and that presents a unique opportunity for the students to observe the operation of a land-based gas turbine used for power generation. A 5 MW TB5000 manufactured by Ruston (Alstom) Gas Engines is available on the Baylor University campus and is highlighted as an example. Potential problems encountered with using the Baylor University gas turbine are discussed which include lack of appropriate engine instrumentation.
LES of the Flow and Particle Ingestion Into an Air Intake of a Jet Engine Running on the Ground
Authors: Moroianu Dragos , Karsllon Arne , Fuchs Laszlo
Published: November 2008

The flow field generated by the flow into a jet engine air-intake, with near ground effects, is considered. The axial inflow in the neighborhood of the ground generates a system of unsteady vortices. Some of these vortices extend from the air-intake towards the ground. Some of these vortices are strong enough to dislocate and even lift small objects from the ground up to the air-intake. The dynamics of the vortex system makes it difficult to study the problem by standard numerical and experimental methods. The dynamics of the vortices can be captured by using Large Eddy Simulations (LES), which is used here to enhance the understanding of the dynamics of the flow field. The computed flow field is used also to assess the ingestion of particles into the air-intake. It is shown that particles of several mm sizes can be ingested into the jet engine. This in turn may result in enhanced erosion of the compressor blades. The results of the computations in terms of mean velocity field have been compared to experimental data. These results are in good agreement with the experiments.
Experimental Investigation of the Rotor-Stator Interactions Within a High Speed, Multi-Stage, Axial Compressor: Part 1 — Experimental Facilities and Results
Authors: Arnaud David , Ottavy Xavier , Vouillarmet Andre´
Published: November 2008

This paper relates to laser anemometry measurements (LDA) conducted in a high speed, three-stage, axial compressor. Particular attention has been paid to the estimation of the measurement accuracy. Three different synchronization procedures have been implemented in order to enhance the exactness of the location in the rotating frame for each situation. Small flat windows mainly provide the optical accesses. But, large curved glasses could also be used, the optical distortions resulting from the surface curvature being corrected with the help of an optical assembly developed for the L2F technique and extended to the LDA technique. Furthermore, in order to avoid interpolation processes when changing the frame of reference, the spatial and time discretizations have been defined in accordance with the numbers of rotor and stator blades. The presented measurements have been performed, at 50% blade height, in the first three inter row sections, the azimuthal exploration covering machine periodicity.
An Experimental Study on Partial Admission in a Two-Stage Axial Air Test Turbine With Numerical Comparisons
Authors: Fridh Jens E. , Bunkute Birute , Fakhrai Reza , Fransson Torsten H.
Published: November 2008

This paper presents ongoing experimental aerodynamic and efficiency measurements on a cold flow two-stage axial air test turbine with low reaction steam turbine blades at different degrees of partial admission. The overall objectives of the work are to experimentally investigate and quantify the steady and unsteady aerodynamic losses induced by partial admission. The first results show that both the total-to-static turbine efficiency drops and that the efficiency peak appears at lower isentropic velocity ratios with lower degrees of admission. Detailed steady traverse measurements of the static wall pressures downstream of sector-ends show strong local variations. The pressure wake from the partial admission blockage moves almost axially through the turbine while the temperature wake is located in a tangential position that represents the position of a particle trace based on velocity triangles, in the direction of the rotor rotation. Comparisons with 2D compressible flow computations around the circumference demonstrate the importance of the radial flow component in these experiments.
Influence of High Fogging Systems on Gas Turbine Engine Operation and Performance
Authors: Cataldi Giovanni , Gu¨ntner Harald , Matz Charles , McKay Tom , Hoffmann Ju¨rgen , Nemet Anton , Lecheler Stefan , Braun Jost
Published: November 2008

High fogging is a power augmentation device where water is sprayed upstream of the compressor inlet with higher mass flow than that which would be needed to saturate the intake air. The main focus of this paper is on applications of high fogging on the ALSTOM gas turbine engines of the family GT24/GT26. Engine operation and performance are illustrated based on test results obtained from four different engines that have meanwhile accumulated more than 12’000 operating hours (OH) in commercial operation with ALSTOM’s ALFog® high fogging system. The effect of internal cooling (water evaporation inside the compressor) is investigated considering actual compressor boundaries matched within the complete engine. Changes in the secondary air system (SAS) and corresponding movement of the engine operating line have been taken into account. Power output gain as high as 7.1% was experimentally demonstrated for injected water mass fraction (f = mH2O/mair) equal to 1% and considering internal cooling effects only. Higher figures can be obtained for operation at low ambient relative humidity and partial evaporation upstream of the compressor inlet.
On the Stability Range of a Cylindrical Combustor for Operation in the FLOX Regime
Authors: Vaz Daniel C. , Borges Anto´nio R. J. , van Buijtenen Jos P. , Spliethoff Hartmut
Published: November 2008

The implementation of flameless combustion in gas turbines is a recent research topic motivated by the potential for ultra-low NOx emissions and improvement of the combustion acoustics. This paper presents preliminary results of the implementation of flameless oxidation in a laboratory model of a cylindrical combustor (in view of stationary and micro gas turbines). Guidelines are given for the start-up of this combustion system. The experimental study then assesses, for atmospheric conditions, the combined effect of the air-to-fuel ratio, wall temperature and jet velocity on combustion stability. Global volumetric heat releases up to 16 MW/m3, and air pre-heat up to 265°C are attained. The numerical simulations give insight into the recirculating pattern of the flow and the state of mixing of reactants and products in the near-nozzle region. The turbulence-chemistry interaction is accounted for by means of the non-premixed flamelet-PDF approach (including finite rate chemistry and scalar dissipation rates up to the extinction limit).
A Nuclear Gas Turbine as Propulsion Unit for a Merchantman
Authors: Crommelin Gulian A. K. , Crommelin Walter F.
Published: November 2008

The paper will discuss a study reflecting the changes in design and exploitation of an existing standard merchantman when the existing diesel propulsion plant is replaced by a gas turbine using a well-proven and inherently safe nuclear heat source. Subjects which will be discussed are: 1. why this study was done, 2. the NEREUS propulsion installation which is considered for this “replacement”, 3. the nuclear part and the non-nuclear part of the NEREUS installation, 4a. safety matters regarding the small-scale nuclear plant, 4b. safety matters regarding the nuclear propulsion plant (the maritime version), 5. fuel availability, 6. place of the nuclear propulsion plant in the ship in view of the weight, 7. required and no longer required auxiliary installations for the nuclear energy plant, 8. restrictions for ship operations, 9. manoeuvring, exploitation and manning of the ship, 10. logistic support of the installation.
Large Eddy Simulation of Flow and Heat Transfer in a 90° Ribbed Duct With Rotation: Effect of Coriolis Forces
Authors: Abdel-Wahab Samer , Tafti Danesh K.
Published: November 2008

This paper presents results from large eddy simulation (LES) of fully developed flow in a 90° ribbed duct with rib pitch-to-height ratio P/e = 10 and a rib height to hydraulic diameter ratio e/Dh = 0.1. Three rotation numbers Ro = 0.18, 0.35 and 0.67 are studied at a nominal Reynolds number based on bulk velocity of 20,000. Mean flow and turbulent quantities, together with heat transfer and friction augmentation data are presented. Turbulence and heat transfer are augmented on the trailing surface and reduced at the leading surface. The heat transfer augmentation ratio on the trailing surface asymptotes to a value of 3.7 ± 5% and does not show any further increasing trend as the rotation number increases beyond 0.2. On the other hand, augmentation ratios on the leading surface keep decreasing with an increase in rotation number with values ranging from 1.7 at Ro = 0.18 to 1.2 at Ro = 0.67. Secondary flow cells augment the heat transfer coefficient on the smooth walls by 20% to 30% over a stationary duct. An increase in rotation number from 0.35 to 0.67 decreases the frictional losses from an augmentation ratio of 9.6 to 8.75 and is a consequence of decrease in form drag and wall shear. Overall augmentation compared with a non-rotating duct ranges from +15% to +20% for heat transfer, and +10% to +15% for friction over the range of rotation numbers studied. Comparison of heat transfer augmentation with previous experimental results in the literature shows very good agreement.
Bayesian Network Approach for Gas Path Fault Diagnosis
Authors: Romessis C. , Mathioudakis K.
Published: November 2008

A method for solving the gas path analysis problem of jet engine diagnostics based on a probabilistic approach is presented. The method is materialized through the use of a Bayesian Belief Network (BBN). Building a BBN for gas turbine performance fault diagnosis requires information of a stochastic nature expressing the probability of whether a series of events occurred or not. This information can be extracted by a deterministic model and does not depend on hard to find flight data of different faulty operations of the engine. The diagnostic problem and the overall diagnostic procedure are first described. A detailed description of the way the diagnostic procedure is set-up, with focus on building the BBN from an engine performance model, follows. The case of a turbofan engine is used to evaluate the effectiveness of the method. Several simulated and benchmark fault case scenarios have been considered for this reason. The examined cases demonstrate that the proposed BBN-based diagnostic method composes a powerful tool. This work also shows that building a diagnostic tool, based on information provided by an engine performance model, is feasible and can be efficient as well.