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Flame Stabilization By A Plasma Driven Radical Jet In A High Speed Flow
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Book Synopsis Flame Stabilization by a Plasma Driven Radical Jet in a High Speed Flow by : Woong-Sik Choi
Download or read book Flame Stabilization by a Plasma Driven Radical Jet in a High Speed Flow written by Woong-Sik Choi and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Active Control of High Speed Jet Flames Using Counterflow by :
Download or read book Active Control of High Speed Jet Flames Using Counterflow written by and published by . This book was released on 2003 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Countercurrent flow control was applied as a novel flame stabilization technique on a premixed jet flame. In the experimental setup a converging nozzle burner was placed concentrically in a suction collar to generate suction driven countercurrent flow. Flame blow off velocity was measured at different suction velocity and equivalence ratio values. Tests show that by applying countercurrent flow around the periphery of a jet flame it can be stabilized up to jet exit velocity of 40 m/s. Particle Image Velocimetry (PIV) measurements and shadowgraph visualizations reveal that, application of suction changes the shear layer structure. An optical temperature measurement technique, refereed to as Laser Speckle Displacement (LSD) was developed for instantaneous temperature field measurements. It is shown that the technique is easy to implement and can be used in conjunction with PIV for simultaneous velocity and temperature measurements in reacting flows.
Book Synopsis Flame Stabilization in High Speed Flow by Pilot Flames by : Thomas Joseph O'Connor
Download or read book Flame Stabilization in High Speed Flow by Pilot Flames written by Thomas Joseph O'Connor and published by . This book was released on 1961 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhancement of Combustion and Flame Stabilization Using Transient Non-Equilibrium Plasma by :
Download or read book Enhancement of Combustion and Flame Stabilization Using Transient Non-Equilibrium Plasma written by and published by . This book was released on 2007 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of non-equilibrium plasma on both partially premixed and non-premixed flames was investigated through the development of a newly integrated magnetic gliding arc (MGA) system. The lifted jet diffusion flame experiments showed a significant enhancement of the flame stabilization with plasma discharge in the air co-flow. The counterflow experiments also demonstrated that the extinction limits were extended dramatically. Laser diagnostics of flame temperature and OH distribution using planar Rayleigh scattering and planar laser-induced fluorescence revealed that the plasma-flame interaction at low air temperature was dominated by thermal effects due to rapid radical quenching. Counterflow ignition experiments for CH4-air and H2-air non-premixed flames demonstrated clearly that the MGA significantly decreased the ignition temperatures via kinetic enhancement by the NOx, catalytic effect. Numerical modeling showed that there were two ignition regimes for plasma enhanced ignition, kinetic at low strain rates and thermal at high strain rates. Comparison between experiment and simulation were in good agreement and also suggested the possibility of enhancement by ions, excited species or other mechanisms. Theoretical analysis of minimum ignition energy in a quiescent mixture showed that the production of small hydrocarbon fuel fragments by plasma discharge also led to a significant decrease of ignition energy due to radiation and transport coupling.
Book Synopsis Ignition and Flame Stabilization in High Speed Flows by :
Download or read book Ignition and Flame Stabilization in High Speed Flows written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reduced mechanisms for ignition of hydrogen by heated air were deduced for the high-temperature/low-pressure and the low-temperature/high-pressure regimes. The reduced mechanisms were subsequently applied to the physical situations of the supersonic mixing layer and the counterflow through numerical simulation and activation energy asymptotics. Various ignition criteria were derived, and the issues of thermal versus radical induced ignition, external versus internal heating in inducing ignition, and quasi-steady versus transient ignition, were explored.
Book Synopsis Plasma Assisted Combustion and Flameholding in High Speed Cavity Flows by : Joseph Aloysius Heinrichs
Download or read book Plasma Assisted Combustion and Flameholding in High Speed Cavity Flows written by Joseph Aloysius Heinrichs and published by . This book was released on 2012 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This thesis presents an experimental study of non-equilibrium, low temperature, large volume plasma assisted ignition and flameholding in high-speed, non-premixed fuel-air flows. The plasma is produced between two electrodes powered by a high-voltage, nanosecond pulse generator operated at a high pulse repetition rate. Ignition in this type of plasma occurs due to production of highly reactive radicals by electron impact excitation and dissociation, as opposed to more common thermal ignition. Previously, it has been shown that this type of plasma can reduce ignition delay time and ignition temperature. The experiments performed in this thesis focus on application of these plasmas to ignition, and flameholding in high-speed cavity flows. The experiments discussed in this thesis continue previous work using a high-speed combustion test section with a larger cavity, and the previous results are compared to the present work. Several modifications have been made to the test section and electrodes compared to the design used in previous work in order to reduce the cavity effect on the main flow and maintain diffuse plasma between the electrodes in the cavity. The electrodes used in these experiments are placed in a cavity recess, used to create a recirculation flow region with long residence time, where ignition and flameholding can occur. In order to analyze the nanosecond pulse plasma and the flame, various diagnostics were used, including current and voltage measurements, UV emission measurements, ICCD camera imaging, static pressure measurements, and time-averaged emission spectroscopy. The experiments in this thesis were performed at relatively low pressures (P=150-200 torr) using hydrogen and ethylene fuels injected into the cavity. Current and voltage measurements showed that ~1-2 mJ was coupled to the plasma by each pulse. ICCD imaging and UV emission data revealed that the plasma sustained in quiescent air was diffuse. When ethylene was injected into the cavity to ignite the flow, ICCD imaging and UV emission data showed arcing to bare metal surfaces in the test section occurred shortly after ignition, which prompted switching to hydrogen fuel. Using hydrogen, ICCD imaging and UV emission showed that the plasma remained diffuse and confined to the area between electrodes. Time-average emission spectroscopy measurements revealed that the air-flow temperature remained low until fuel was injected and ignition occurred. Pressure and UV emission measurements were used to find velocity limits within which the flow ignited. It was found that the upper limit of velocity depends strongly on the static pressure in the test section. The highest flow velocity at which combustion was achieved in H2-air flows was 270 m/s at 180 torr. This represents considerable improvement compared to previous work using nanosecond pulse discharge for ignition in cavities. Preliminary results show that plasma generation and ignition are possible using a smaller diameter electrode such that the cavity size can be further reduced, and that a supersonic flow can be produced in the present test section using a Mach 2 nozzle placed upstream of the cavity. The appendix details a study on the production of oxygen atoms using a pulsed excimer laser.
Book Synopsis Flame Stabilization in High Speed Streams by : J. J. Zelinski
Download or read book Flame Stabilization in High Speed Streams written by J. J. Zelinski and published by . This book was released on 1956* with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flame Stabilization in High Velocity Flow by : Joshua Swithenbank
Download or read book Flame Stabilization in High Velocity Flow written by Joshua Swithenbank and published by . This book was released on 1977* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Stabilization and Dynamic of Premixed Swirling Flames by : Paul Palies
Download or read book Stabilization and Dynamic of Premixed Swirling Flames written by Paul Palies and published by Academic Press. This book was released on 2020-07-21 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stabilization and Dynamic of Premixed Swirling Flames: Prevaporized, Stratified, Partially, and Fully Premixed Regimes focuses on swirling flames in various premixed modes (stratified, partially, fully, prevaporized) for the combustor, and development and design of current and future swirl-stabilized combustion systems. This includes predicting capabilities, modeling of turbulent combustion, liquid fuel modeling, and a complete overview of stabilization of these flames in aeroengines. The book also discusses the effects of the operating envelope on upstream fresh gases and the subsequent impact of flame speed, combustion, and mixing, the theoretical framework for flame stabilization, and fully lean premixed injector design. Specific attention is paid to ground gas turbine applications, and a comprehensive review of stabilization mechanisms for premixed, partially-premixed, and stratified premixed flames. The last chapter covers the design of a fully premixed injector for future jet engine applications. Features a complete view of the challenges at the intersection of swirling flame combustors, their requirements, and the physics of fluids at work Addresses the challenges of turbulent combustion modeling with numerical simulations Includes the presentation of the very latest numerical results and analyses of flashback, lean blowout, and combustion instabilities Covers the design of a fully premixed injector for future jet engine applications
Book Synopsis An Investigation of the Effects of Unsteady Flow on Flame Stabilization by a Reverse Jet Flame Holder ... by : Billie Joe Fluker
Download or read book An Investigation of the Effects of Unsteady Flow on Flame Stabilization by a Reverse Jet Flame Holder ... written by Billie Joe Fluker and published by . This book was released on 1969 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced technologies in flow dynamics and combustion in propulsion and power, volume II by : Lei Luo
Download or read book Advanced technologies in flow dynamics and combustion in propulsion and power, volume II written by Lei Luo and published by Frontiers Media SA. This book was released on 2023-02-09 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Plasma-Induced Ignition and Plasma-Assisted Combustion in High-Speed Flow by :
Download or read book Plasma-Induced Ignition and Plasma-Assisted Combustion in High-Speed Flow written by and published by . This book was released on 2003 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper is dedicated to the experimental demonstration of plasma technology abilities in the field of high speed combustion. It is doing in three principal directions: control of the structure and the parameters of the duct driven flows; the ignition of air fuel composition at low mean gas temperature; and the mixing intensification inflow.
Book Synopsis Effects of Pilot Flame Stabilization on Gas Jet Flames in a Cross-flow by : S. R. Gollahalli
Download or read book Effects of Pilot Flame Stabilization on Gas Jet Flames in a Cross-flow written by S. R. Gollahalli and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Studies on Flow Field and Flame Stabilization of a Premixed Reacting Jet in Vitiated Crossflow by : Jason Allen Wagner
Download or read book Experimental Studies on Flow Field and Flame Stabilization of a Premixed Reacting Jet in Vitiated Crossflow written by Jason Allen Wagner and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flame Stabilization in a Model Ram-jet Combustion Chamber by : A. H. Newcombe
Download or read book Flame Stabilization in a Model Ram-jet Combustion Chamber written by A. H. Newcombe and published by . This book was released on 1951 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Study of Laminar Burning Speed and Plasma-stabilized Flame by : Saeid Zare
Download or read book Experimental Study of Laminar Burning Speed and Plasma-stabilized Flame written by Saeid Zare and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since being discovered, combustion of fuels, especially fossil fuels in the last centuries, has been the dominant source of energy for human life. However, over the years, the adverse effects and shortcomings caused by the vast utilization of these energy sources have been observed; the three most important of which are unreliable resources, unfavorable natural outcomes, and limited performance. Using biofuels is one of the well-established proposed solutions to the scarcity and environmental issues of fossils as they are sustainable sources of energy with acceptable and even superior combustion characteristics. As a second-generation biofuel, anisole has shown promising results with high flame speed and high knock resistance. Therefore, the first chapter of this thesis is focused on experimental investigation of anisole laminar burning speed and stability properties so that it can be used as a benchmark for future kinetic mechanism validations. Stability is another important parameter in combustion systems, especially in diffusion jet flame combustion as used in many applications like thrusters or burners. Different methods are applied to improve the stability of such diffusion flames in propulsion systems, e.g., changing geometrical or flow characteristics of the burner. Most of these efforts have not been practically successful, due to the cost and compatibility issues. Another technique which minimizes such problems is to use electron impact excitation, dissociation and ionization and generate highly concentrated charged/excited species and active radicals. These methods include microwave, dielectric barrier, and repetitive nanosecond pulsed (RNP) discharge and the latter has shown promising results as one of the most effective low-temperature plasma (LTP) methods. In chapters 3 to 5, the benefits and issues associated with using RNP discharge in a single-element concentric methane-air inverse diffusion jet flame are discussed. It has been shown that RNP discharge with adequate discharge properties (voltage and repetition) can increase the stability of the flame and expand the flammability of the jet toward leaner compositions. However, the effectiveness is significant in a certain voltage-frequency ranges which results a non-thermal spark discharge mode. Hence, different modes of discharge were investigated and a parametric study on the transition between these modes were done.
Book Synopsis An Experimental Study of Flame Stabilization Mechanisms in Turbulent Non-premixed Jet Flames Under Autoignitive Conditions by : Aravind Ramachandran
Download or read book An Experimental Study of Flame Stabilization Mechanisms in Turbulent Non-premixed Jet Flames Under Autoignitive Conditions written by Aravind Ramachandran and published by . This book was released on 2019 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:
