The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Peter R. Bushnell - One of the best experts on this subject based on the ideXlab platform.
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Aerodynamics of cross-Flow fans and their application to aircraft propulsion and Flow control
Progress in Aerospace Sciences, 2009Co-Authors: Thong Q. Dang, Peter R. BushnellAbstract:Cross-Flow fans offer unique opportunities for distributed propulsion and Flow control due to their potential for spanwise integration in aircraft wings. The fan may be fully or partially embedded within the wing using a variety of possible configurations. Its inlet may be used to ingest the boundary-layer Flow, and its high-energy Exhaust Flow may be injected into the wake at the wing trailing edge for drag reduction or vectored thrust. Cross-Flow fans are high-pressure coefficient machines, so they can be diametrically compact. However, their efficiency is fundamentally limited by unavoidable recirculation Flows within the impeller at all flight speeds, and by additional compressibility losses at high speeds. This article reviews the fundamental aerodynamics and Flow regions of cross-Flow fans using a simple mean-line analysis to examine the basic energy transfer and loss processes. Experimental data for fans intended for aircraft application are then reviewed and compared to calculations using unsteady Navier-Stokes methods, showing the state-of-the art in Flow field and performance prediction capability. Alternative prediction methods where blade action is modeled in terms of body-force or vortex elements are discussed, including challenges in handling arbitrary non-uniform, unsteady blade Flows for various design configurations. The article concludes with a review of cross-Flow fan propulsion and Flow control concepts that have been investigated by various researchers, and with discussions on future challenges in their application. © 2008 Elsevier Ltd. All rights reserved.
Laszlo Fuchs - One of the best experts on this subject based on the ideXlab platform.
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Exhaust Flow Pulsation Effect on Radial Turbine Performance
2015Co-Authors: Johan Fjällman, Mihai Mihaescu, Laszlo FuchsAbstract:In the current vehicle manufacturing world the chase for a better fuel economy and better driveability is in high gear. One way of doing so is to investigate and optimize the turbocharger. In this paper the Flow in a radial turbine of a passenger car turbocharger has been analysed by Large Eddy Simulations. The current simulations have investigated the effects of changing the inlet pulse frequency and inlet pulse shape on turbines performance parameters (e.g. ef- ficiency, shaft power, pressure distributions). Three different engine speeds and two different pulse shapes were chosen to be compared and analysed. With the total mass Flow per pulse being constant for all cases there is a clear dependence of both pulse shape and frequency when it comes to e.g. wheel momentum. Higher frequency increases the peak momentum more than the minimum level. A reduction in pulse duration also increases peak momentum more than the minimum.
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LES of the Exhaust Flow in a Heavy-Duty Engine
Oil & Gas Science and Technology-revue De L Institut Francais Du Petrole, 2013Co-Authors: Olle Bodin, Mihai Mihaescu, Yue Wang, Laszlo FuchsAbstract:The Flow in the Exhaust port and the Exhaust manifold of a heavy-duty Diesel engine has been studied using the Large Eddy Simulation approach. Some of the Flow characteristics in these components a ...
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Assessment of Heat Transfer Effects on the Performance of a Radial Turbine using Large Eddy Simulation
2010Co-Authors: Fredrik Hellström, Laszlo FuchsAbstract:One way to reduce fuel consumption and emissions is to downsize the engine in combination with turbo-charging. The turbine works under highly unsteady Flow conditions, since the Exhaust Flow is pul ...
John Hoke - One of the best experts on this subject based on the ideXlab platform.
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T63 TURBINE RESPONSE TO ROTATING DETONATION COMBUSTOR Exhaust Flow
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2018Co-Authors: Andrew Naples, John Hoke, Ryan Battelle, Frederick R. SchauerAbstract:This paper describes testing an axial turbine response when driven by a rotating detonation combustor (RDC). A T63 (C20-250) gas turbine is modified by replacing the combustor with a RDC. The stator vanes of the T63 are heavily instrumented for the measurement of Flow enthalpy and pressure. The engine is run at multiple power levels with the stock combustor using JetA and hydrogen fuel. The engine is then modified to have an open loop configuration and is run with both the RDC and the stock combustor hardware with hydrogen fuel. Temperature pattern factor, Flow unsteadiness, and turbine component efficiency are measured for all setups. High-speed pressure transducers show substantially higher unsteadiness generated by the RDC than the conventional combustor. RDC turbine component efficiencies are compared to the conventional combustor. Results suggest that RDC unsteadiness does not significantly impact turbine efficiency.
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T63 Turbine Response to Rotating Detonation Combustor Exhaust Flow
Volume 3: Coal Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems, 2018Co-Authors: Andrew Naples, John Hoke, Ryan Battelle, Fred SchauerAbstract:This paper describes testing an axial turbine response when driven by a Rotating Detonation Combustor (RDC). A T63 (C20-250) gas turbine is modified by replacing the combustor with a RDC. The stator vanes of the T63 are heavily instrumented for measurement of Flow enthalpy and pressure. The engine is run at multiple power levels with the stock combustor using JetA and hydrogen fuel. The engine is then modified to have an open loop configuration, and is run with both the RDC and the stock combustor hardware with hydrogen fuel. Temperature pattern factor, Flow unsteadiness, and turbine component efficiency are measured for all setups. High speed pressure transducers show substantially higher unsteadiness generated by the RDC than the conventional combustor. RDC turbine component efficiencies are compared to the conventional combustor. Results suggest that RDC unsteadiness does not significantly impact turbine efficiency.
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Study of the Experimental Performance of a Rotating Detonation Engine with Nozzled Exhaust Flow
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Matthew Fotia, John Hoke, Thomas A. Kaemming, Frederick SchauerAbstract:A rotating detonation engine has been experimentally tested with various nozzle configurations for the purposes of measuring the propulsive performance of these devices in terms of thrust and specific impulse. Particular attention is given to comparing different internal nozzle configurations which include bluff body, aerospike and choked aerospike arrangements. The nozzle throat exit choke present in the rotating detoantion engine Exhaust is analysed to provide insight into the stagnation pressure gain nature of the device. Thrust performance estiamtions are presented in comparison to the observed thrust stand quatities, and potential loss mechanisms are discussed.
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periodic Exhaust Flow through a converging diverging nozzle downstream of a rotating detonation engine
52nd Aerospace Sciences Meeting, 2014Co-Authors: Brent A Rankin, John Hoke, Frederick SchauerAbstract:Periodic Exhaust Flow around a conical centerbody and through a converging-diverging nozzle downstream of a rotating detonation engine (RDE) is studied in this work using experimental and computational methods. Time-dependent and time-averaged static pressure measurements are acquired along the nozzle to provide insights into the unsteadiness of the Flow for a range of RDE operating conditions. Unsteady Flow computations are performed on a three-dimensional domain using an unstructured finitevolume compressible Flow solver and prescribing a time-dependent boundary condition at the inlet of the nozzle. The time-dependent pressure measurements and computations indicate that the periodic Flow at the nozzle inlet remains periodic up to the nozzle throat. The Flow is non-periodic with no characteristic frequency near the nozzle exit. The conclusions regarding the transition from periodic to non-periodic Flow are supported quantitatively by statistical analysis of the time-dependent pressure measurements including temporal autocorrelation coefficients and power spectral density functions. The measurements and computations reported in this work demonstrate that the combination of a conical centerbody and converging-diverging nozzle provides a useful passive Flow control technique for eliminating the periodic nature of the Flow downstream of rotating detonation engines.
Jun Ishimoto - One of the best experts on this subject based on the ideXlab platform.
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Dynamic restriction mechanism for the upper limit of Exhaust Flow rates in the real-time sensing-based forced ventilation control of leaking hydrogen
International Journal of Hydrogen Energy, 2015Co-Authors: Kazuo Matsuura, Masami Nakano, Jun IshimotoAbstract:Abstract We propose a novel control algorithm for hydrogen ventilation, utilizing a dynamic restriction mechanism for the upper limit of Exhaust Flow rates, extending the real-time sensing-based forced ventilation control algorithm of leaking hydrogen we proposed previously for a partially open space. This upper limit is determined using a correlation between hydrogen concentrations sampled near the ceiling, close to a leak source, and the upper boundary of the region of acceptable Exhaust Flow rates for various leak Flow rates. We apply the algorithm to numerical simulations of hydrogen ventilation in a partially open space with low-height openings, varying leak Flow rates and sensor arrangements. Results show that this algorithm works successfully.
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Acceleration of hydrogen forced ventilation after leakage ceases in a partially open space
International Journal of Hydrogen Energy, 2012Co-Authors: Kazuo Matsuura, Masami Nakano, Jun IshimotoAbstract:Abstract This paper treats the real-time sensing-based risk-mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation. A hunting-preventive control scheme that we previously proposed (Matsuura et al., Int J Hydrogen Energy , 2012;37(2):1972–84) has parameters such as the monitoring period of hydrogen sensors T p , a unit increment in the Exhaust Flow rate per area from a roof vent α , and a threshold e for the change in the Exhaust Flow rate. Through parametric simulations of the hydrogen Exhaust after leakage ceases, we clarify the effects of the parameters on the rate of Exhaust Flow from the roof vent and the amount of hydrogen accumulating near the roof, which are critical for ventilation performance. With a selected combination of ( T p , α , e ) for which the ventilation system has a quick response and reasonable original performance, we first introduce two acceleration methods separately to the original hunting-preventive scheme to improve the ventilation performance after hydrogen leakage ceases. Ventilation performance employing the two methods is compared with that employing the original scheme. From the results, a hybrid method is finally proposed. The effectiveness of the proposed method is computationally validated for leak Flow rates of 9.44 × 10 −4 , 4.72 × 10 −4 and 2.36 × 10 −4 m 3 /s.
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Forced ventilation for sensing-based risk mitigation of leaking hydrogen in a partially open space
International Journal of Hydrogen Energy, 2010Co-Authors: Kazuo Matsuura, Masami Nakano, Jun IshimotoAbstract:Abstract This study performs the numerical simulation of hydrogen dispersion in a partially open space with a single roof vent. The effects of various roof vent positions, leak positions, leak Flow rates and Exhaust Flow rates on the forced ventilation of leaking hydrogen, are shown and discussed. Based on the results, a proper roof vent position and the disadvantage of ventilation with constant Exhaust Flow rates are established. To overcome the disadvantage, a new control strategy to change Exhaust Flow rates with the roof vent fixed at the proper position is proposed. First a plot is constructed to show acceptable Exhaust Flow rates to various inFlow rates and leak positions. Assuming real-time sensing of hydrogen concentration and height-direction velocity, volume Flow rates of leaking hydrogen are then estimated. Based on the estimated leak Flow rates and hydrogen sensor information near the roof, control is conducted considering the plot of acceptable Exhaust Flow rates to various inFlow rates and leak positions. The proposed method is validated against various leak positions, leak Flow rates and leak modes. This paper proposes an innovative approach to sensing-based risk mitigation control of hydrogen dispersion and accumulation in a partially open space by forced ventilation.
L. I. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Image-based Automated Reconstruction of the Great Buddha of Bamiyan, Afghanistan
IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops, 2003Co-Authors: Armin Gruen, Fabio Remondino, L. I. ZhangAbstract:The coefficient of discharge (CD) is defined as the ratio of actual discharge to ideal discharge. In an engine environment, ideal discharge considers an ideal gas and the process to be free from friction, surface tension, etc. Coefficients of discharge are widely used to monitor the Flow efficiency through various engine components and are quite useful in improving the performance of these components. The Flow through engines it is equally important to have accurate values for coefficients of discharge through the combinations of valves, ports and ducts. In this experiment investigation of air Flow and coefficient of discharge are desirable for inFlow (reverse Flow) through the Exhaust port using SuperFlow Flowbench. The coefficients of discharge the diesel engines can be quite measured under steady Flow conditions for a range of pressures and Flows. This paper presents experimental results for air Flow and coefficient of discharge investigating the intake and Exhaust Flow of four stroke direct injection diesel engines. The CD measurements are shown for various pressures, valve lift per diameters (L/D) ratio conditions at the intake port pipe to cylinder and cylinder to Exhaust port pipe geometries.