The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform
Cesare A. Hall - One of the best experts on this subject based on the ideXlab platform.
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Boundary-Layer Suction System Design for Laminar-Flying-Wing Aircraft
Journal of Aircraft, 2011Co-Authors: Tariq Saeed, W R Graham, Cesare A. HallAbstract:DOI: 10.2514/1.C031283 The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with Aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient;hence,toagoodapproximation,thepowerpenaltyisgivenbytheproductoftheoptimalsuction flowrate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, if there are fewer pumps than chambers, the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers,determinesthepowerpenalty.Fortherepresentativelaminar-flying-wingaircraftparametersconsidered here, the minimum power associated with boundary-layer losses alone contributes some 80–90% of the total power requirement.
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Boundary-Layer Suction System Design for Application to a Laminar Flying Wing Aircraft
28th AIAA Applied Aerodynamics Conference, 2010Co-Authors: Tariq Saeed, W R Graham, Holger Babinsky, Cesare A. HallAbstract:Growing air travel, with its associated environmental impact, is increasingly becoming a public concern. The laminar-flying-wing aircraft, which utilises boundary-layer suction as a means of laminar-flow control, has been proposed by Greener by Design as a potential solution, with preliminary estimates suggesting a significant reduction in fuel-burn per passenger of up to 70%. The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss of an ‘optimal’ suction distribution which maintains a neutrally stable laminar boundarylayer. Variation from the optimal suction distribution due to a practical, chamber-based, architecture is found to have very little effect on the overall suction coefficient; hence, to a good approximation, the power penalty is given by the product of the optimal suction flow-rate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the effect of the chamber pressure drop due to frictional and inertial effects may be taken as negligible. Finally, if there are fewer pumps than chambers, it is the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers, that determines the power penalty. For the representative laminar-flying-wing aircraft parameters considered here, the minimum power associated with boundary-layer losses alone contributes around 80% to the total power requirement.
W R Graham - One of the best experts on this subject based on the ideXlab platform.
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research data supporting design study for a laminar flying wing aircraft Surface pressures lfw Aerofoil Surface pressure coefficients in the form used for the suction calculation
2015Co-Authors: T I Saeed, W R GrahamAbstract:These files provide the LFW Aerofoil Surface pressure coefficients in the form used for the suction calculation. 'Geom' files give the section geometry (standard, chord-normalised, coordinates) in two alternative orderings; 'LoCp' and 'UpCp' give pressure coefficient as function of (normalised) chordwise distance for pressure and suction Surfaces respectively. For case listing, see 'nameConvention.txt'.
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Boundary-Layer Suction System Design for Laminar-Flying-Wing Aircraft
Journal of Aircraft, 2011Co-Authors: Tariq Saeed, W R Graham, Cesare A. HallAbstract:DOI: 10.2514/1.C031283 The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with Aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient;hence,toagoodapproximation,thepowerpenaltyisgivenbytheproductoftheoptimalsuction flowrate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, if there are fewer pumps than chambers, the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers,determinesthepowerpenalty.Fortherepresentativelaminar-flying-wingaircraftparametersconsidered here, the minimum power associated with boundary-layer losses alone contributes some 80–90% of the total power requirement.
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Boundary-Layer Suction System Design for Application to a Laminar Flying Wing Aircraft
28th AIAA Applied Aerodynamics Conference, 2010Co-Authors: Tariq Saeed, W R Graham, Holger Babinsky, Cesare A. HallAbstract:Growing air travel, with its associated environmental impact, is increasingly becoming a public concern. The laminar-flying-wing aircraft, which utilises boundary-layer suction as a means of laminar-flow control, has been proposed by Greener by Design as a potential solution, with preliminary estimates suggesting a significant reduction in fuel-burn per passenger of up to 70%. The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss of an ‘optimal’ suction distribution which maintains a neutrally stable laminar boundarylayer. Variation from the optimal suction distribution due to a practical, chamber-based, architecture is found to have very little effect on the overall suction coefficient; hence, to a good approximation, the power penalty is given by the product of the optimal suction flow-rate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the effect of the chamber pressure drop due to frictional and inertial effects may be taken as negligible. Finally, if there are fewer pumps than chambers, it is the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers, that determines the power penalty. For the representative laminar-flying-wing aircraft parameters considered here, the minimum power associated with boundary-layer losses alone contributes around 80% to the total power requirement.
Gary D. Lock - One of the best experts on this subject based on the ideXlab platform.
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Experimentally aided development of a turbine heat transfer prediction method
International Journal of Heat and Fluid Flow, 2004Co-Authors: A. E. Forest, M. L. G. Oldfield, A.j. White, Gary D. LockAbstract:Abstract In the design of cooled turbomachinery blading a central role is played by the computer methods used to optimise the aerodynamic and thermal performance of the turbine Aerofoils. Estimates of the heat load on the turbine blading should be as accurate as possible, in order that adequate life may be obtained with the minimum cooling air requirement. Computer methods are required which are able to model transonic flows, which are a mixture of high temperature combustion gases and relatively cool air injected through holes in the Aerofoil Surface. These holes may be of complex geometry, devised after empirical studies of the optimum shape and the most cost effective manufacturing technology. The method used here is a further development of the heat transfer design code (HTDC), originally written by Rolls-Royce plc under subcontract to Rolls-Royce Inc for the United States Air Force. The physical principles of the modelling employed in the code are explained without extensive mathematical details. The paper describes the calibration of the code in conjunction with a series of experimental measurements on a scale model of a high-pressure nozzle guide vane at non-dimensionally correct engine conditions. The results are encouraging, although indicating that some further work is required in modelling highly accelerated pressure Surface flow.
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Experimentally Aided Development of a Turbine Heat Transfer Prediction Method
Volume 3: Turbo Expo 2002 Parts A and B, 2002Co-Authors: A. E. Forest, A. J. Rawlinson, M. L. G. Oldfield, Gary D. LockAbstract:In the design of cooled turbomachinery blading a central role is played by the computer methods used to optimize the aerodynamic and thermal performance of the turbine Aerofoils. It is particularly important that estimates of the heat load on the turbine blading should be as accurate as possible, in order that adequate life may be obtained with the minimum cooling air requirement. Computer methods are required which are able to model transonic flows, which are a mixture of high temperature combustion gases and relatively low temperature cooling air injected through holes in the Aerofoil Surface. These holes may be of complex geometry, devised after empirical studies of the optimum shape and the most cost effective manufacturing technology. The method used here is a further development of the Heat Transfer Design Code (HTDC), originally written by Rolls-Royce plc under subcontract to Rolls-Royce Inc for the United States Air Force. The physical principles of the modeling employed in the code are explained without extensive mathematical details. The paper describes the calibration and development of the code in conjunction with a series of experimental measurements on a scale model of a high-pressure nozzle guide vane at non-dimensionally correct engine conditions.Copyright © 2002 by ASME
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The Influence of Film Cooling on the Efficiency of an Annular Nozzle Guide Vane Cascade
Journal of Turbomachinery-transactions of The Asme, 1999Co-Authors: M. L. G. Oldfield, Gary D. LockAbstract:This paper examines the effect of Aerofoil Surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF{sub 6}/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility that correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity. The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. First, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented that eliminates the need to measure concentration in order to determine loss. Second, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parameterization of film cooling studies with varying coolant densities. Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference betweenmore » cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data have been obtained both for purposes of design and for CFD code validation.« less
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The Influence of Film Cooling on the Efficiency of an Annular Nozzle Guide Vane Cascade
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 1997Co-Authors: M. L. G. Oldfield, Gary D. LockAbstract:This paper examines the effect of Aerofoil Surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility which correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity.The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. Firstly, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented which eliminates the need to measure concentration in order to determine loss. Secondly, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parametrisation of film cooling studies with varying coolant densities.Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference between cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data has been obtained both for purposes of design and for CFD code validation.© 1997 ASME
Tariq Saeed - One of the best experts on this subject based on the ideXlab platform.
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Boundary-Layer Suction System Design for Laminar-Flying-Wing Aircraft
Journal of Aircraft, 2011Co-Authors: Tariq Saeed, W R Graham, Cesare A. HallAbstract:DOI: 10.2514/1.C031283 The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with Aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient;hence,toagoodapproximation,thepowerpenaltyisgivenbytheproductoftheoptimalsuction flowrate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, if there are fewer pumps than chambers, the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers,determinesthepowerpenalty.Fortherepresentativelaminar-flying-wingaircraftparametersconsidered here, the minimum power associated with boundary-layer losses alone contributes some 80–90% of the total power requirement.
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Boundary-Layer Suction System Design for Application to a Laminar Flying Wing Aircraft
28th AIAA Applied Aerodynamics Conference, 2010Co-Authors: Tariq Saeed, W R Graham, Holger Babinsky, Cesare A. HallAbstract:Growing air travel, with its associated environmental impact, is increasingly becoming a public concern. The laminar-flying-wing aircraft, which utilises boundary-layer suction as a means of laminar-flow control, has been proposed by Greener by Design as a potential solution, with preliminary estimates suggesting a significant reduction in fuel-burn per passenger of up to 70%. The present study aims to provide insight into the parameters affecting practical laminar-flow-control suction power requirements for a commercial laminar-flying-wing transport aircraft. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss of an ‘optimal’ suction distribution which maintains a neutrally stable laminar boundarylayer. Variation from the optimal suction distribution due to a practical, chamber-based, architecture is found to have very little effect on the overall suction coefficient; hence, to a good approximation, the power penalty is given by the product of the optimal suction flow-rate coefficient and the average skin pressure drop. In the spanwise direction, through suitable choice of chamber depth, the effect of the chamber pressure drop due to frictional and inertial effects may be taken as negligible. Finally, if there are fewer pumps than chambers, it is the average pressure drop from the Aerofoil Surface to the pump collector ducts, rather than to the chambers, that determines the power penalty. For the representative laminar-flying-wing aircraft parameters considered here, the minimum power associated with boundary-layer losses alone contributes around 80% to the total power requirement.
M. L. G. Oldfield - One of the best experts on this subject based on the ideXlab platform.
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Experimentally aided development of a turbine heat transfer prediction method
International Journal of Heat and Fluid Flow, 2004Co-Authors: A. E. Forest, M. L. G. Oldfield, A.j. White, Gary D. LockAbstract:Abstract In the design of cooled turbomachinery blading a central role is played by the computer methods used to optimise the aerodynamic and thermal performance of the turbine Aerofoils. Estimates of the heat load on the turbine blading should be as accurate as possible, in order that adequate life may be obtained with the minimum cooling air requirement. Computer methods are required which are able to model transonic flows, which are a mixture of high temperature combustion gases and relatively cool air injected through holes in the Aerofoil Surface. These holes may be of complex geometry, devised after empirical studies of the optimum shape and the most cost effective manufacturing technology. The method used here is a further development of the heat transfer design code (HTDC), originally written by Rolls-Royce plc under subcontract to Rolls-Royce Inc for the United States Air Force. The physical principles of the modelling employed in the code are explained without extensive mathematical details. The paper describes the calibration of the code in conjunction with a series of experimental measurements on a scale model of a high-pressure nozzle guide vane at non-dimensionally correct engine conditions. The results are encouraging, although indicating that some further work is required in modelling highly accelerated pressure Surface flow.
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Experimentally Aided Development of a Turbine Heat Transfer Prediction Method
Volume 3: Turbo Expo 2002 Parts A and B, 2002Co-Authors: A. E. Forest, A. J. Rawlinson, M. L. G. Oldfield, Gary D. LockAbstract:In the design of cooled turbomachinery blading a central role is played by the computer methods used to optimize the aerodynamic and thermal performance of the turbine Aerofoils. It is particularly important that estimates of the heat load on the turbine blading should be as accurate as possible, in order that adequate life may be obtained with the minimum cooling air requirement. Computer methods are required which are able to model transonic flows, which are a mixture of high temperature combustion gases and relatively low temperature cooling air injected through holes in the Aerofoil Surface. These holes may be of complex geometry, devised after empirical studies of the optimum shape and the most cost effective manufacturing technology. The method used here is a further development of the Heat Transfer Design Code (HTDC), originally written by Rolls-Royce plc under subcontract to Rolls-Royce Inc for the United States Air Force. The physical principles of the modeling employed in the code are explained without extensive mathematical details. The paper describes the calibration and development of the code in conjunction with a series of experimental measurements on a scale model of a high-pressure nozzle guide vane at non-dimensionally correct engine conditions.Copyright © 2002 by ASME
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Aerodynamic performance of an annular cascade of film cooled nozzle guide vanes under engine representative conditions
Experiments in Fluids, 2000Co-Authors: M. L. G. Oldfield, G. D. LockAbstract:This paper addresses two important issues relevant to efficiency measurements in film-cooled annular cascades: the definition of the ideal flow to be used in loss calculation, and the measurements that are necessary for such loss calculation. The paper also addresses the question of the correct parameterisation of coolant density effects, showing that the momentum flux ratio, rather than the blowing rate, is the most appropriate parameter. Experiments examining the effect of extensive Aerofoil Surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes are reported. A dense foreign gas (SF_6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios, momentum ratios and blowing rates under ambient temperature conditions. Experiments are also conducted with air coolant to study the effect of density ratio on efficiency. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility which correctly models engine Reynolds and Mach numbers. This work compares the measured aerodynamic efficiencies of uncooled vanes with those which employ an extensive amount of cooling. The engine-representative cooling geometry investigated features 14 rows of cylindrical cooling holes, and a second geometry where 8 of these rows are replaced by holes having a fan-shaped exit. The effects of adding trailing edge slot ejection are also presented. By selectively blocking rows of holes, the cumulative effect on the mid-span efficiency of adding rows of cooling holes has also been determined. Experimental results are presented as area traverse maps (total pressure, isentropic Mach number and flow angles), from which the relative changes in efficiency due to film cooling have been calculated. These calculations reveal that the presence of foreign-gas coolant from the cylindrical-hole geometry increases the aerodynamic loss (relative to the uncooled baseline) by 6.7%; and coolant from the fan-shaped holes increases the loss by 15%. The effects of different assumptions for the coolant total pressure are shown to significantly change the measured loss; if the loss measurements are based on the mainstream total pressure, rather than the total pressure in the coolant cavity, the respective increase in loss (relative to the uncooled baseline) of cylindrical and fan-shaped holes is 4.5% and 12.5%. Experimental data is compared with loss predictions using a Hartsel model.
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The Influence of Film Cooling on the Efficiency of an Annular Nozzle Guide Vane Cascade
Journal of Turbomachinery-transactions of The Asme, 1999Co-Authors: M. L. G. Oldfield, Gary D. LockAbstract:This paper examines the effect of Aerofoil Surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF{sub 6}/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility that correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity. The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. First, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented that eliminates the need to measure concentration in order to determine loss. Second, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parameterization of film cooling studies with varying coolant densities. Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference betweenmore » cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data have been obtained both for purposes of design and for CFD code validation.« less
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The Influence of Film Cooling on the Efficiency of an Annular Nozzle Guide Vane Cascade
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 1997Co-Authors: M. L. G. Oldfield, Gary D. LockAbstract:This paper examines the effect of Aerofoil Surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility which correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity.The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. Firstly, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented which eliminates the need to measure concentration in order to determine loss. Secondly, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parametrisation of film cooling studies with varying coolant densities.Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference between cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data has been obtained both for purposes of design and for CFD code validation.© 1997 ASME
