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.

Download or read book Cavity Ignition and Flameholding of High Speed Fuel air Flows by a Repetitively Pulsed Nanosecond Discharge written by Ashim Dutta and published by . This book was released on 2011 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kinetic modeling is used to study the mechanism of low-temperature nanosecond pulse plasma assisted ignition. The reduced kinetic mechanism of plasma assisted ignition of hydrogen has been identified and compared with the full mechanism in a wide range of temperatures and pressures, showing good agreement. Kinetic modeling calculations performed to study the effect of non-thermal radical generation in nanosecond pulse discharge plasma on oxidation/ignition of hydrogen-air mixtures demonstrated that removal of plasma chemical radical generation processes inhibits low-temperature exothermic chemical reactions, thus blocking ignition. It is also observed that presence of radicals produced by the plasma accelerates ignition process significantly and reduces ignition temperature. Finally, the kinetic model has been used to interpret the results of flameholding experiments in premixed ethylene-air and hydrogen-air flows.

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.

Download or read book Plasma assisted Combustion in a Supersonic Flow written by Hyungrok Do and published by . This book was released on 2009 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book OH LIF Studies of Low Temperature Plasma Assisted Oxidation and Ignition in Nanosecond Pulsed Discharge written by Inchul Choi and published by . This book was released on 2011 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In recent years, plasma assisted ignition and flame-holding in high speed flows has attracted considerable attention due to potential applications for turbojet engines and afterburners operating at high altitudes, as well as scramjet engines. Conventional methods of igniting a flow in the combustor using a spark or an arc discharge are known to be ineffective at low pressures and high flow velocities, since the ignition kernel is limited by a small volume of the spark or arc filament. Single photon LIF spectroscopy is used to study hydroxyl radical formation and loss kinetics in low temperature hydrogen-air repetitively pulsed nanosecond plasmas. Nanosecond pulsed plasmas are created in a rectangular cross section quartz channel / plasma flow reactor. Flow rates of hydrogen-air mixtures are controlled by mass flow controllers at a total pressure of 40-100 torr, initial temperature T0=300-500 K and a flow velocity of approximately u=0.1-0.8 m/sec. Two rectangular copper plate electrodes, rounded at the corners to reduce the electric field non-uniformity, are attached to the outside of the quartz channel. Repetitively pulsed plasmas are generated using a Chemical Physics Technologies (CPT) power supply which produces ~25 nanosecond pulses with ~20 kV peak voltage. Absolute hydroxyl radical mole fraction is determined as both a function of time after application of a single 25 nsec pulse, and 60 microseconds after the final pulse of a variable length "burst" of pulses. Relative LIF signal levels are put on an absolute mole fraction scale by means of calibration with a standard near-adiabatic Hencken flat flame burner at atmospheric pressure. By obtaining OH LIF data in both the plasma and the flame, and correcting for differences in the collisional quenching and Vibrational Energy Transfer (VET) rates, absolute OH mole fraction can be determined. For a single discharge pulse at 27 °C and 100 °C, the absolute OH temporal profile is found to rise rapidly during the initial ~0.1 msec after discharge initiation and decay relatively slowly, with a characteristic time scale of ~1 msec. In repetitive burst mode the absolute OH number density is observed to rise rapidly during the first approximately 10 pulses (0.25 msec), and then level off to a near steady-state plateau. In all cases a large secondary rise in OH number density is also observed, clearly indicative of ignition, with ignition delay equal to approximately 15, 10, and 5 msec, respectively, for initial temperatures of 27 °C, 100 °C, and 200 °C. Plasma kinetic modeling predictions capture this trend quantitatively.

Download or read book Plasma Assisted Combustion written by Wansheng Nie and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a promising technology, plasma-assisted combustion (PAC) has attracted many researchers to explore the effect of PAC on improving the combustion in propulsion devices, such as scramjet, detonation engines, internal engines, and so on. In this chapter, we aim to exhibit the influence of quasi-DC discharge plasma on the operating performance of scramjet combustor and find the internal mechanisms, which may contribute to the development of PAC technology in supersonic combustion. For case one, a plasma filament is generated upstream of fuel jet through quasi-DC discharge in a scramjet combustor; for case two, the plasma is formed across the backward facing step of a flame holding cavity to improve the flame stabilization of the cavity in the scramjet combustor. The two cases are investigated in detail through three-dimensional numerical simulation based on the dominant thermal blocking mechanism. Important parameters including temperature distribution, separation zone, water production, stagnation pressure loss, combustion efficiency, cavity drag, mass exchange rate, and cavity oscillating characteristics are obtained and analyzed. It shows that the quasi-DC discharge plasma does benefit for the improvement of the combustion in a scramjet combustor.

Download or read book Using Plasmas for High speed Flow Control and Combustion Control written by Saurabh Keshav and published by . This book was released on 2008 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Experiments on characterization of Localized Arc Filament Plasma Actuators used for high-speed flow control, as well as experimental studies of chemiluminescence and chemi-ionization for flame emission and combustion control have been discussed. Pulsed DC and pulsed RF actuator discharge power measurements and plasma temperature measurements demonstrated that rapid localized heating, at a rate of 1000 degrees C / 10 us, can be achieved at low time-averaged actuator powers, 10-20 W for 10% duty cycle. Kinetic modeling of a pulsed arc filament demonstrated formation of strong compression waves due to rapid localized heating, which have also been detected in the experiments. The effect of electrons in chemi-ionized supersonic flows of combustion products on flow emission is studied experimentally. For this, a stable ethylene/oxygen/argon flame is sustained in a combustion chamber at a stagnation pressure of P0=1 atm. Electron density in M=3 flow of combustion products has been measured using Thomson discharge. The results show that nearly all electrons can be removed from the flow by applying a moderate transverse electric field. No effect of electron removal on CH and C2 emission from the flow has been detected. Also, electron removal did not affect NO [beta] band and CN violet band emission when nitric oxide was injected into the combustion product flow. Chemi-ionization current measured in the supersonic flows of combustion products has been used for feedback combustion control. The experiments showed that time-resolved chemi-ionization current is in good correlation with the visible emission (CH and C2 bands) in the combustor at unstable combustion conditions, and is nearly proportional to the equivalence ratio at stable combustion conditions. Chemi-ionization current signal from the combustion product flow has been used to control an actuator valve in the fuel delivery line and to maintain the equivalence ratio in the combustor at the desired level.

Download or read book The Proceedings of 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment IDCOMPU2023 written by Xuzhu Dong and published by Springer Nature. This book was released on 2024-03-28 with total page 731 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes original, peer-reviewed research papers from the 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023), held in Wuhan, China. The topics covered include but are not limited to: insulation, discharge computations, electric power equipment, and electrical materials. The papers share the latest findings in the field of insulation and discharge computations of electric power equipment, making the book a valuable asset for researchers, engineers, university students, etc.

Download or read book Plasma Assisted Combustion written by and published by . This book was released on 2007 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report results from a contract tasking Moscow Institute of Physics and Technology as follows: The contractor will investigate the use of high voltage, nano-second plasma discharges to ignite and efficiently combust fuel/air mixtures in high speed flows. This strongly nonequilibrium low-temperature plasma has a high mean energy of electrons and will provide a source of reactive atoms, radicals, and excited molecules which has been shown to enhance ignition and combustion. The short duration of the pulses results in relatively low power requirements for generating the discharge. The goal is to demonstrate and understand the physics of energy exchange, ignition and combustion . Also, the use of this type of plasma for aerodynamic flow control will be investigated. Finally, applicability to use this type of discharge to directly initiate a detonation wave will be investigated.

Download or read book Mean Pressure Gradient Effects on Flame flow Dynamics in a Cavity Combustor written by David Michael Smerina and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pressure gradient confinement effects are experimentally investigated within a cavity combustor to analyze the flame interactions of premixed, cavity stabilized, flames in a high-speed combustor. Pressure gradient confinement effects are generated in a dual mode ramjet-scramjet (DMSR) by varying the wall geometry to form converging, diverging, and nominal configurations. The velocity field and flame position are captured temporally using simultaneous high-speed particle image velocimetry (PIV) and CH chemiluminescence. The evolution of the flow field and flame structure are analyzed, and the high temporal resolution of these measurements allows for the characterization of turbulence-flame interactions. Consideration of the combustion mode and inlet conditions, such as the inflow velocity and turbulence, are vital in studying flame-vortex interaction dynamics and its effect on the flame stabilization process and is essential in ensuring efficient, complete combustion. The results from the experiment will provide a greater understanding of how flame-vorticity interactions and pressure gradient confinement effects play a key role in the flame-stabilization and combustion process.

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:

Download or read book Plasma Science and Technology written by Haikel Jelassi and published by BoD – Books on Demand. This book was released on 2019-02-27 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: Usually called the "fourth state of matter," plasmas make up more than 99% of known material. In usual terminology, this term generally refers to partially or totally ionized gas and covers a large number of topics with very different characteristics and behaviors. Over the last few decades, the physics and engineering of plasmas was experiencing a renewed interest, essentially born of a series of important applications such as thin-layer deposition, surface treatment, isotopic separation, integrated circuit etchings, medicine, etc. Plasma Science

Download or read book Numerical Simulation of Plasma Assisted Turbulent Combustion written by Anand Srinivas Ankala and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: In order to improve the combustion performance inside a gas turbine combustion chamber, many attempts have been made and the area of turbulent combustion has been of keen interest to the researchers in the recent years. In particular, CFD simulations in this area have a significant importance, because of their accuracy being on par with the experimental solutions and substantial reduction in the cost and time. An attempt has been made to study the combustion of methane-air mixture in a gas turbine combustion chamber by incorporating the fluid dynamic effects of a standard plasma actuator into the flow field of the regime. Application of high voltage potential between two copper electrodes separated by a dielectric material leads to the generation of plasma and an electric field. This electric field creates a body force and by orienting the plasma force in the desired direction, combustion rate can be accelerated by increasing the flame's blow-off velocity. For the present study, the geometry was created in Gambit. All steady and transient simulations were carried out in Fluent employing the appropriate turbulent models. Initially the effect of plasma force was studied in the regime without any chemical reaction in the flow field. Non-premixed combustion of methane and air has been modeled and in the next stage, plasma force is applied to the system. The actuators are placed near the regions where vortices are present in the flow field and the plasma force tends to break them down and at the same time the flow is accelerated and enhancement in the mixing of reactants is observed. An unsteady detached eddy simulation has been performed to analyze the modifications in the flow field and combustion phenomenon created by the plasma force.

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 46 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.

Download or read book Study of Internal and External Plasma Assisted Combustion in Supersonic Gas Flow written by and published by . This book was released on 2005 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Project is devoted to basic study on the field of external and internal plasma assisted combustion. This effort consists of three Tasks: Task #1 is titled "Internal plasma assisted combustion controlled by improved plasma generators in metal channel at conditions similar to Scramjet"; Task #2 is tilted "External plasma combustion experiment in a supersonic flow (Mtilde2, Pst=1 Bar)". This is a study of flow around model F with plasma combustion generator in wind tunnel; Task #3 is tilted "Study of supersonic flow around model E with combined plasma generator (PG Comb= PG HF +E beam)". Here. the main plasma parameters could be changed independently in PG- Comb. Electron concentration will be controlled by E-beam. Electron temperature could be controlled by external HF electric field. The main goals of this work is a study of following: Optimal radical generation in fuel/air mixture and combustion control by non equilibrium plasmoids, Advanced mixture of fuel in gas flow by structural plasmoids.

Download or read book The Scramjet Engine written by Corin Segal and published by Cambridge University Press. This book was released on 2009-06-22 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: Demand for high-speed propulsion has renewed development of the supersonic combustion ramjet engine (Scramjet engine) for hypersonic flight applications.

Download or read book Unsteady Supersonic Combustion written by Mingbo Sun and published by Springer Nature. This book was released on 2020-04-14 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the unsteady phenomena needed to understand supersonic combustion. Following an initial chapter that introduces readers to the basic concepts in and classical studies on unsteady supersonic combustion, the book highlights recent studies on unsteady phenomena, which offer insights on e.g. interactions between acoustic waves and flames, flow dominating instability, ignition instability, flame flashback, and near-blowout-limit combustion. In turn, the book discusses in detail the fundamental mechanisms of these phenomena, and puts forward practical suggestions for future scramjet design.