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You searched for subject:(Flame holder). Showing records 1 – 2 of 2 total matches.

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Clemson University

1. Quinones, Matthew. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.

Degree: MS, Mechanical Engineering, 2018, Clemson University

Various types of air breathing engines are used as propulsion devices in aviation. At high flight velocities, the use of a ramjet or supersonic combustion ramjet (scramjet) may be preferred due to the natural compressibility of air at high speed. A scramjet, while similar to the ramjet, does not slow air to subsonic speeds prior to combustion, allowing it to operate at much higher flight velocities at very high altitude. For this reason, however, the residence time of air inside of the combustor is on the order of milliseconds, requiring rapid mixing and ignition of the fuel to generate adequate thrust. To do this, a flameholder is often used, which generates turbulence, shock waves, and maintains a recirculation region through geometric effects. In this study, four geometry types involving eighteen separate designs were chosen and analyzed using CFD software. Isolator inlet Mach numbers of 2.2, 4, 6, 8, and 10 were selected to model varying flight velocity, and hydrogen fuel was injected sonically at all injector locations with a single step reaction mechanism applied for combustion. An existing square cavity model was chosen and modified to produce slanted cavity, double cavity, and combined strut-cavity designs. The flameholders were analyzed in a non-reacting simulation to observe their effects on the flow field and fuel mixing efficiency. Reacting simulations were performed for each flameholder to investigate flame stabilization capabilities, thermal choking, stagnation pressure losses and drag generated inside of the combustor. Results show that all designs sustain a flame during combustion at all flight Mach numbers. However, the square cavity with a back cavity injector does this while limiting losses and drag due to shock wave formation, thermal choking, and geometric effects in the flow. Advisors/Committee Members: Dr. Richard Miller, Committee Chair, Dr. John Saylor, Dr. Xiangchun Xuan.

Subjects/Keywords: Flame holder; Flame stability; Ramjet; Scramjet

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APA (6th Edition):

Quinones, M. (2018). Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/3010

Chicago Manual of Style (16th Edition):

Quinones, Matthew. “Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.” 2018. Masters Thesis, Clemson University. Accessed January 24, 2021. https://tigerprints.clemson.edu/all_theses/3010.

MLA Handbook (7th Edition):

Quinones, Matthew. “Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.” 2018. Web. 24 Jan 2021.

Vancouver:

Quinones M. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. [Internet] [Masters thesis]. Clemson University; 2018. [cited 2021 Jan 24]. Available from: https://tigerprints.clemson.edu/all_theses/3010.

Council of Science Editors:

Quinones M. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. [Masters Thesis]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_theses/3010


Georgia Tech

2. Choi, Woong-Sik. Flame stabilization by a plasma driven radical jet in a high speed flow.

Degree: PhD, Mechanical Engineering, 2009, Georgia Tech

In current afterburners combustion is stabilized by the high temperature, recirculating region behind bluff body flame holders, such as V-gutters. Blocking the high speed flow with bluff bodies causes a significant pressure drop, and heating the flame holder by the hot combustion product causes a thermal signature, which is a critical problem in a military jet. To reduce these problems, ignition methods using a high frequency (HF) spark discharge, or a radical jet generator (RJG) were developed. The HF discharge ignited and stabilized a flame successfully in a premixed methane-air flow. The electrical power consumption was very small compared to the combustion heat release, as long as the operating velocity was relatively low. However, a theoretical study showed that the ratio of the electrical power consumption to the heat generation by the stabilized flame increases rapidly with increasing flow velocity. For flame stabilization in a high velocity flow, the developed RJG showed much better performance than direct exposure to a plasma. The present study investigated the characteristics of a radical jet produced in a RJG and injected into a main combustor. The limits of flame stabilization by this jet was measured experimentally, and compared to those of bluff body flame holders. The flame holding performance of the radical jet was also experimentally compared to that of a thermal jet. The effect of radicals on flame stabilization was examined using CHEMKIN, and the limit of flame stabilization by the radical jet was estimated for a simple flow configuration using an approximate solution. The results suggest that the reduction of local spontaneous ignition delay time by active species in the radical jet and the longer length of a typical radical jet compared to the dimension of the recirculation zone behind a bluff body increases the maximum velocity at which a flame can be stabilized. Advisors/Committee Members: Zinn, Ben (Committee Chair), Jagoda, Jeff (Committee Co-Chair), Glezer, Ari (Committee Member), Jeter, Sheldon (Committee Member), Neumeier, Yedidia (Committee Member).

Subjects/Keywords: Electrical discharge; Flame detector; Ignition distance; Ignition delay; Plasma; Flame holder; Radical jet; Flame stabilization; Afterburners; Combustion; Jets Fluid dynamics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Choi, W. (2009). Flame stabilization by a plasma driven radical jet in a high speed flow. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/29780

Chicago Manual of Style (16th Edition):

Choi, Woong-Sik. “Flame stabilization by a plasma driven radical jet in a high speed flow.” 2009. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021. http://hdl.handle.net/1853/29780.

MLA Handbook (7th Edition):

Choi, Woong-Sik. “Flame stabilization by a plasma driven radical jet in a high speed flow.” 2009. Web. 24 Jan 2021.

Vancouver:

Choi W. Flame stabilization by a plasma driven radical jet in a high speed flow. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Jan 24]. Available from: http://hdl.handle.net/1853/29780.

Council of Science Editors:

Choi W. Flame stabilization by a plasma driven radical jet in a high speed flow. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/29780

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