Performance Measurements of Direct Air Injection in a Cavity-based Flameholder for a Supersonic Combustor PDF Download
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Author: Scott G. Edens
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 186
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Author: Scott G. Edens
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 186
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Author: William H. Allen (Jr.)
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 178
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 14
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Book Description
The effect of direct fuel and air injection was experimentally studied in a cavity-based flameholder in a supersonic flow. Cavity- based fuel injection and flameholding offer an obstruction-free flow path in hydrocarbon-fueled supersonic combustion ramjet (scram jet) engines. Additionally, this study included characterization of the operational limits (i.e., sustained combustion limits) over a variety of fuel and air flow rates. The cavity rearward ramp includes 10 spanwise injection ports at each of 3 axial stations configured to inject air, fuel, and air, respectively. Planar laser-induced fluorescence (PLIF) techniques were utilized to collect planar distributions of the OH radical at various axial locations within the cavity under different flow conditions. A high-speed emissions camera was used to evaluate the combustion across the cavity. Direct injection of both fuel and air provided additional capability to tune the cavity such that a more stable decentralized flame results. The addition of air injection provided the most improvement over the baseline case (fuel only) near the upstream portion of the cavity close to the cavity step.
Author: K.-Y. Hsü
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 14
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Book Description
An experimental investigation of cavity-based flameholders with strut injectors in a supersonic flow is reported. In this ongoing research program, emphases are placed on understanding cavity-based flameholders and providing alternative methods for improving overall combustor performance in scramjet engines. Three different struts with fuel injectors are mounted near the cavity leading edge to study flame propagation and ignition of fuel in the core flow region. OH-PLIF (planar laser induced fluorescence) is used to identify the flame zone around the cavity and strut-wake regions over a range of conditions. Shadowgraphy is used to capture the flow features around the strut and cavity. In-stream probing is conducted to characterize the flow features associated with the different strut configurations. Stagnationtemperature profiles are obtained for all struts operating over the same conditions in the combusting-flow study. Two cavity fueling schemes are used to compare flameholder performance. Direct cavity air injection is found to improve combustion significantly. For each strut, upstream and downstream fueling schemes are compared over a range of conditions.--P. i.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Recent results from combustion experiments in a direct-connect supersonic combustor are presented. Successful ignition and sustained combustion of gaseous ethylene have been achieved using an injector/flameholder concept with low-angle, flush-wall fuel injection upstream of a wall cavity. Two interchangeable facility nozzles (Mach 1.8 and 2.2) were used to obtain combustor inlet flow properties that simulate flight conditions between Mach 4 and 6 at a dynamic pressure of 47.9 kPa. Mainstream combustion was achieved at equivalence ratios between 0.25 and 0.75 using only a spark plug and no other external ignition aids. Delta-force levels between 667 and 1779 N were measured, with corresponding combustor pressure ratios between 3.1 and 4.0. Video records of the flame zone show an intensely active combustion zone with rapid flame spreading. One-dimensional performance analysis of the test data indicates a combustion efficiency around 80% with an average combustor skin friction coefficient of 0.0028.
Author: MacKenzie J. Collatz
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 140
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Author: Steven J. Etheridge
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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Typical studies of scramjet combustion employ as uniform a flowpath as possible. These studies are important to isolate the effects of a given combustor configuration. However, such studies tend to ignore the effects of a shock train created by the vehicle installation and that this shock train changes over the flight envelope. Consequently, the performance of a given configuration is measured without considering the considerable effects of this shock train or how it changes with different flight conditions. This thesis includes experimental and computational studies of the effects of an incident shockwave on the flowfield, fuel distribution and combustion within a cavity flameholder with upstream fuel injection. The effect of the shockwave location (on the upstream fuel jet or over the cavity) and shock angle are controlled by adjusting a shock generator mounted in the tunnel test section. The effect of fuel injection momentum ratio is also examined. Shadowgraphy is used to characterize the flowfield while planar laser induced fluorescence of the NO and OH molecules are used to measure the fuel mixing and combustion, respectively. These experimental data are compared with CFD solutions of the Reynolds Averaged Navier-Stokes equations provided in previous CFD work. The effect of the shock on the cavity shear layer is found to control the fuel distribution within the cavity. The shock on jet impingement forces the shear layer deep within the cavity and results in higher concentrations near the cavity centerline, but low mixing uniformity. The shock on cavity case causes the shear layer to separate upstream of the cavity, mixing uniformity is enhanced by the increased breakup of the fuel plume. Combustion is stronger and more uniform in the shock on cavity case, while it is limited to the edges of the cavity with shock impingement on the jet. The greater mixing afforded in the shock on cavity case reduces the fuel concentration near the centerline and permits stronger burning in the center of the cavity. Small changes in the fuel injection momentum ratio (doubling) do not strongly affect the pattern of fuel distribution in any case. Combustion in the shock on cavity case is reduced by increasing fuel injection momentum because the fuel concentration at the centerline is too high. Small increases in the shock angle did not strongly affect the results.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 732
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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Book Description
Cavity-based fuel injection and flame holding, typically found in hydrocarbon-fueled scramjet applications, are of current interest for use in supersonic combustors. The Air Force Research Lab (AFRL) and the Air Force Institute of Technology (AFlT) are investigating the enhancement of fuel-air mixing with small pylons that project into the supersonic flow upstream of a flame holder. The pylons were of three sizes and were shaped as a thin triangular wedge with a 300 inclination angle. Four configurations (pylons plus baseline) were tested at two different fuel injection pressures in a Mach continuous flow wind tunnel housed at AFRL. The goal was to measure the mixing efficiency and shock loss of each pylon setup for comparison to the baseline condition of transverse injection without pylons. Intrusive and non intrusive techniques were used to obtain pitot pressure, total temperature, cone-static pressure, and laser induced Raman spectroscopy to determine species concentration over the cavity downstream of the injection port. Results showed that pylons increase fuel penetration, while not adding significantly to shock losses or overall mixing.
Author: Independently Published
Publisher:
ISBN: 9781723862571
Category :
Languages : en
Pages : 68
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Book Description
The current work has focused on finding the optimum cavity properties to enhance themixing phenomenon and combustion processes in supersonic flow using ComputationalFluid Dynamics (CFD) ANSYS Fluent. Various models has been modeled with differentvalues of offset ratios (OR) and aft ramp angles (ϴ) while keeping the length-to-depth ratioconstant. All cavity flows have taken open type i.e. length-to-depth ratio
