Download or read book Influence of Spark Energy Spark Number and Flow Velocity on Detonation Initiation in a Hydrocarbon fueled PDE written by Ilissa Brooke Schild and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsed Detonation Engines (PDEs) have the potential to revolutionize fight by better utilizing the chemical energy content of reactive fuel/air mixtures over conventional combustion processes. Combustion by a super-sonic detonation wave results in a significant increase in pressure in addition to an increase in temperature. In order to harness this pressure increase and achieve a high power density, it is desirable to operate PDEs at high frequency. The process of detonation initiation impacts operating frequency by dictating the length of the chamber and contributing to the overall cycle time. Therefore a key challenge in the development of a practical PDEs is the requirement to rapidly initiate a detonation in hydrocarbon-air mixtures. This thesis evaluates the influence of spark energy and airflow velocity on this challenging initiation process. The influence of spark energy, number of sparks and airflow velocity on Deflagration-to-Detonation Transition (DDT) was studied during cyclic operation of a small-scale PDE at the General Electric Global Research Center. Experiments were conducted in a 50 mm square transitioning to cylindrical channel PDE with optical access operating with stoichiometric ethylene-air mixture. Total spark energy was varied from 250 mJ to 4 J and was distributed between one and four spark plugs located in the same axial location. Initial flame acceleration was imaged using high-speed shadowgraph and was characterized by the time to reach 20 cm from the spark plug. Measurements of detonation wave velocity and emergence time, the time it takes the detonation wave to exit the tube, was measured using dynamic pressure transducers and ionization probes. It was found that the flame front spread was faster at higher spark energies and with more spark locations. Initial flame acceleration was 16% faster for the 4-spark, 4 J case when compared to the baseline 1-spark, 1 J case. When looking at the effect of airflow on the influence of spark energy, it was found that airflow had a larger effect on emergence time at high energies, versus energies less than 1 J. Finally, for a selected case of 0.25 J spark energy and 4 sparks, the velocity of the fuel-air mixture during fill was found to have a varying influence on detonation initiation and emergence time.
Download or read book 41st AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit 10 13 July 2005 Tucson Arizona 05 4200 05 4249 written by and published by . This book was released on 2005 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of fuel distribution on detonation tube performance written by and published by DIANE Publishing. This book was released on with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detonation Branching in a PDE with Liquid Hydrocarbon Fuel written by Kristin L. Panzenhagen and published by . This book was released on 2004-03-01 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: A pulse detonation engine (PDE) capitalizes on the large mass flux and pressure rise associated with detonations to create thrust, which is proportional to PDE cycle frequency. This research showed that using a branched detonation as an ignition source, as opposed to standard spark ignition, deposits more energy into the thrust tube head. The increase in energy decreases ignition delay and detonation to deflagration transition (DDT) time. This allows a theoretical 85% cycle frequency increase that is accompanied by an 85% increase in thrust. The increase in energy also reduces the need for a DDT enhancement device, thereby increasing thrust as much as 30%. While detonation branching has been accomplished using gaseous hydrogen, this was the first instance of detonation branching using liquid hydrocarbon fuel.
Download or read book Detonation Initiation in Alkane oxygen Mixtures written by Elton L. Litchfield and published by . This book was released on 1966 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Deflagration to Detonation Transition in a Pulsed Detonation Engine written by David Michael Chapin and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A Pulse Detonation Engine (PDE) is a propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the transition of a subsonic deflagration, created using low initiation energies, to a supersonic detonation. This thesis presents the effects of obstacle spacing, blockage ratio, DDT section length, and airflow on DDT behavior in hydrogen-air and ethylene-air mixtures for a repeating PDE. These experiments were performed on a 2 diameter, 40 long, continuous-flow PDE located at the General Electric Global Research Center in Niskayuna, New York. A fundamental study of experiments performed on a modular orifice plate DDT geometry revealed that all three factors tested (obstacle blockage ratio, length of DDT section, and spacing between obstacles) have a statistically significant effect on flame acceleration. All of the interactions between the factors, except for the interaction of the blockage ratio with the spacing between obstacles, were also significant. To better capture the non-linearity of the DDT process, further studies were performed using a clear detonation chamber and a high-speed digital camera to track the flame chemiluminescence as it progressed through the PDE. Results show that the presence of excess obstacles, past what is minimally required to transition the flame to detonation, hinders the length and time to transition to detonation. Other key findings show that increasing the mass flow-rate of air through the PDE significantly reduces the run-up time of DDT, while having minimal effect on run-up distance. These experimental results provided validation runs for computational studies. In some cases as little as 20% difference was seen. The minimum DDT length for 0.15 lb/s hydrogen-air studies was 8 L/D from the spark location, while for ethylene it was 16 L/D. It was also observed that increasing the airflow rate through the tube from 0.1 to 0.3 lbs/sec decreased the time required for DDT by 26%, from 3.9 ms to 2.9 ms.
Download or read book Investigation of Sustained Detonation Devices written by Robert B. Driscoll and published by . This book was released on 2016 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study is conducted on a Pulse Detonation Engine-Crossover System to investigate the feasibility of repeated, shock-initiated combustion and characterize the initiation performance. A PDE-crossover system can decrease deflagration-to-detonation transition length while employing a single spark source to initiate a multi-PDE system. Visualization of a transferred shock wave propagating through a clear channel reveals a complex shock train behind the leading shock. Shock wave Mach number and decay rate remains constant for varying crossover tube geometries and operational frequencies. A temperature gradient forms within the crossover tube due to forward flow of high temperature ionized gas into the crossover tube from the driver PDE and backward flow of ionized gas into the crossover tube from the driven PDE, which can cause intermittent auto-ignition of the driver PDE. Initiation performance in the driven PDE is strongly dependent on initial driven PDE skin temperature in the shock wave reflection region. An array of detonation tubes connected with crossover tubes is developed using optimized parameters and successful operation utilizing shock-initiated combustion through shock wave reflection is achieved and sustained. Finally, an air-breathing, PDE-Crossover System is developed to characterize the feasibility of shock-initiated combustion within an air-breathing pulse detonation engine. The initiation effectiveness of shock-initiated combustion is compared to spark discharge and detonation injection through a pre-detonator. In all cases, shock-initiated combustion produces improved initiation performance over spark discharge and comparable detonation transition run-up lengths relative to pre-detonator initiation. A computational study characterizes the mixing processes and injection flow field within a rotating detonation engine. Injection parameters including reactant flow rate, reactant injection area, placement of the fuel injection, and fuel injection distribution are varied to assess the impact on mixing. Decreasing reactant injection areas improves fuel penetration into the cross-flowing air stream, enhances turbulent diffusion of the fuel within the annulus, and increases local equivalence ratio and fluid mixedness. Staggering fuel injection holes produces a decrease in mixing when compared to collinear fuel injection. Finally, emulating nozzle integration by increasing annulus back-pressure increases local equivalence ratio in the injection region due to increased convection residence time.
Download or read book Detonation and Two Phase Flow written by S Penner and published by Elsevier. This book was released on 2012-12-02 with total page 381 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress in Astronautics and Rocketry, Volume 6: Detonation and Two-Phase Flow compiles technical papers presented at the ARS Propellants, Combustion, and Liquid Rockets Conference held in Palm Beach, Florida on April 26-28, 1961. This book provides an excellent illustration of research and development on a selected group of problems relating to detonations, two-phase nozzle flow, and combustion in liquid fuel rocket engines. This volume is divided into two parts. Part 1 covers the entire range of physical conditions under which detonation may be initiated or sustained, such as high explosives, solid propellants, liquid sprays, and gases. Experimental and theoretical studies are also discussed, including the significant progress of the basic phenomena involved in transition from deflagration to detonation, and nature of stable detonations in dilute sprays and other systems. The perennial problems associated with high frequency instabilities in liquid fuel rocket engines are considered in Part 2. This publication is valuable to students and investigators working in the field of propulsion research and development.
Download or read book Initiation of Orderly Spinning Detonation Waves Via Phased Sparking written by Jacob A. Boening and published by . This book was released on 2016 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Continuous Rotating Detonation Engine (CRDE) was tested with two unique features. First, the conventional pre-detonator was replaced by a novel detonation wave generator. This generator sequentially fired spark plugs at a speed near the acoustic speed of a reactant gas mixture thereby producing free radicals ready to partake in detonation. The generator produced high speed detonation waves traveling with homogenous direction in gaseous mixtures of H2 and O2. Detonation waves continued to spin in a self-sustained fashion after turning off the wave generator. The number of simultaneous sparks did not influence the number of detonation waves observed. Instead the number of observed detonation waves was a strong function of the mass flow rate of reactants. Second, the fuel and oxidizer were injected radially. To avoid the thrust-area loss of conventional axial injection, all injection holes were oriented along the annulus radially, thereby allowing the high pressure to work over the entire front end area. Furthermore, radial injection modulated the mixing of fuel and oxidizer to adjust the axial location of detonation zones avoiding damage to the wave generator.
Download or read book FLUID MOTION EFFECT ON CYCLE TO CYCLE COMBUSTION VARIATION FLAME DEVELOPMENT AND SPARK DELIVERY IN SPARK IGNITION ENGINES written by PHILIP SHAFER KELLER and published by . This book was released on 1991 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: in the determination of the cycle-resolved mean velocity, the greater the correlation.
Download or read book Spark Ignition of Flowing Gases written by Clyde C. Swett and published by . This book was released on 1954 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Directed Air Flow on Combustion in a Spark ignition Engine written by Addison May Rothrock and published by . This book was released on 1940 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detonation Initiation and Evolution in Spray Fueled Pulsed Detonation Rocket Engines written by and published by . This book was released on 2007 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Successful pulsed detonation engine operation requires robust, reliable, repetitive detonation initiation and evolution, up to 100 times per second. Spark-initiated combustion of fuel-oxidizer mixtures appears to be the operational technology. Our research program was designed to model the transient events following time-resolved deposition of thermal energy into a finite volume of reactive mixture. Computational solutions of the reactive Euler equations are used to predict the time history of deflagration to detonation transitions (DDT's). Solutions describe the temporal variation of the spatial distributions of temperature, pressure and fuel concentration. The presence of shocks, localized reactive hot spots and high speed reaction zones are noted. Solution dependence on the location of the initial power deposition, the amount of power deposition and the activation energy on a one step reaction is investigated. In all cases the DDT process is facilitated by the spontaneous appearance of localized high pressure and temperature ":reaction centers" that are the subsequent sources of acoustic compression waves.
Download or read book Influence of Electrode Material on Spark Ignition Probability written by Jeffrey Shawn Peterson and published by . This book was released on 1992 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Initiation and Sensitization of Detonable Hydrocarbon Air Mixtures for Pulse Detonation Engines written by and published by . This book was released on 2004 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The initiation of detonation in hydrocarbon fuel-air mixtures and the effect initiation has on performance are two key issues for the assessment and progress of Pulse Detonation Engines. This report presents the results of experimental studies into the initiation of detonation and the impact of initiation on the impulse generated in a single-cycle Pulse Detonation Engine. In order to facilitate the prompt initiation of detonation, a number of chemical sensitizers were considered (nitrates, nitrogen dioxide, peroxides). None of these were shown to have a significant sensitizing effect, as quantified either by the run-up distance to detonation or by the detonation veil size. Partial reforming of the fuel/oxygen mixture via the "cool flame" process was shown to have a significant sensitizing effect, reducing the run-up distance by a factor of two and the cell size by a factor of three. This effect was transient, in that it was only observed immediately prior to the onset of cool flame. The ability to initiate an unsensitized fuel-air mixture via a turbulent jet of combustion products was demonstrated in two different facilities at different scales. Different techniques of creating a nearly instantaneous constant volume explosion in a pre-combustion chamber were investigated. These techniques were then used to drive a turbulent jet of combustion products through orifices of different geometries. The use of flame tubes was shown to be highly effective in creating constant volume explosion pressures, and the use of an annular orifice to create a centrally focused jet was found to be the most effective orifice design. The scaling for jet initiation of detonation was determined in terms of the characteristic cell size.
Download or read book Fuel Effects on Driveability and Hydrocarbon Emissions of Spark ignition Engines During Starting and Warm up Processes written by Kuo-Chiang Chen and published by . This book was released on 1996 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow in the Piston cylinder ring Crevices of a Spark ignition Engine written by M. Namazian and published by . This book was released on 1982 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
