Deflagration to Detonation Transition Initiation in Pulsed Detonation Engines PDF Download
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Author:
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ISBN:
Category :
Languages : en
Pages : 39
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This report results from a contract tasking Imperial College Consultants Limited (ICON) as follows: It is here proposed to build upon the experience gained and extend ongoing work in two directions. The first is related to the sensitivity of the initial explosion phase to the state of the mixture resulting from injection of the relevant mixture. The second aspect of the proposed work features computations of two-dimensional unsteady flows with comprehensive chemistry and a transported PDF approach closed at the joint scalar level. The contractor proposes the evaluation of a computational approach in the context of the computation of time-dependent compressible flows in two spatial dimensions. Such computations constitute an essential step in the direction of establishing an ability to model Deflagration to Detonation Transition (DDT) in the context of POEs and are exceptionally resource intensive. Although a limited study is here proposed to be accomplished (due to funds limitations). it is expected that significant information will be gained.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 39
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Book Description
This report results from a contract tasking Imperial College Consultants Limited (ICON) as follows: It is here proposed to build upon the experience gained and extend ongoing work in two directions. The first is related to the sensitivity of the initial explosion phase to the state of the mixture resulting from injection of the relevant mixture. The second aspect of the proposed work features computations of two-dimensional unsteady flows with comprehensive chemistry and a transported PDF approach closed at the joint scalar level. The contractor proposes the evaluation of a computational approach in the context of the computation of time-dependent compressible flows in two spatial dimensions. Such computations constitute an essential step in the direction of establishing an ability to model Deflagration to Detonation Transition (DDT) in the context of POEs and are exceptionally resource intensive. Although a limited study is here proposed to be accomplished (due to funds limitations). it is expected that significant information will be gained.
Author: David Michael Chapin
Publisher:
ISBN:
Category : Propulsion systems
Languages : en
Pages :
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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.
Author: R. J. Litchford
Publisher:
ISBN:
Category : Detonation waves
Languages : en
Pages : 52
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Author: Alexander R. Hausman
Publisher:
ISBN:
Category : Detonation waves
Languages : en
Pages : 158
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Author:
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ISBN:
Category :
Languages : en
Pages : 11
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An in-house computational and experimental program to investigate and develop an air breathing pulse detonation engine (PDE) that uses a practical fuel (kerosene based, fleet-wide use, JP type) is currently underway at the Combustion Sciences Branch of the Turbine Engine Division of the Air Force Research Laboratory (AFRL/PRTS). PDE's have the potential of high thrust, low weight, low cost, high scalability, and wide operating range, but several technological hurdles must be overcome before a practical engine can be designed. This research effort involves investigating such critical issues as: detonation initiation and propagation; valving, timing and control; instrumentation and diagnostics; purging, heat transfer, and repetition rate; noise and multi-tube effects; detonation and deflagration to detonation transition modeling; and performance prediction and analysis. An innovative, four-detonation-tube engine design is currently in test and evaluation. Preliminary data are obtained with premixed hydrogen/air as the fuel/oxidizer to demonstrate proof of concept and verify models. Techniques for initiating detonations in hydrogen/air mixtures are developed without the use of oxygen enriched air. An overview of the AFRL/PRTS PDE development research program and hydrogen/air results are presented.
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Category :
Languages : en
Pages : 13
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Detonation initiation of hydrocarbon-air mixtures is critical to the development of the pulsed detonation engine (PDE). Conventionally, oxygen enrichment (such as a predetonator) or explosives are utilized to initiate detonations in hydrocarbon/air mixtures. While often effective, such approaches have performance and infrastructure issues associated with carrying and utilizing the reactive components. An alternative approach is to accelerate conventional deflagration-to-detonation speeds via deflagration-to-detonation transition (DDT). Analysis of hydrocarbon-air detonability indicates that mixing and stoichiometry are crucial to successful DDT. A conventional Schelkin-type spiral is used to obtain DDT in hydrocarbon-air mixtures with no excess oxidizer. The spiral is observed to increase deflagrative flame speeds (through increased turbulence and flame mixing) and produce 'hot-spots' that are thought to be compression-wave reflections. These hot spots result in micro-explosions that, in turn, then give rise to DDT. Time-of-flight analysis of high-frequency pressure-transducer traces indicate that the wavespeeds typically accelerate to over-driven detonation during DDT before stabilizing at Chapman-Jouget levels as the combustion front propagates down the detonation tube. Results obtained for a variety of fuels indicate that DDT of hydrocarbon-air mixtures is possible in a PDE.
Author:
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ISBN:
Category :
Languages : en
Pages : 85
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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.
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Category :
Languages : en
Pages : 0
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The aim of the work performed in the current contract is to assess the accuracy of potential modelling techniques applied to the formation of Deflagration to Detonation (DDT) kernels in mixtures of hydrocarbons with air. The application area is of direct relevance to the transition to detonation in pulsed detonation engines featuring premixed gases. The latter technology is currently pursued at Wright Laboratories and the current evaluation is directly linked to this technology. Key aspects covered include guidance on suitable theoretical development directions and a preliminary investigation of optimal conditions for transition to detonation. The work is technically demanding and features several aspects that has not previously been accomplished. The main conclusions of the study are perhaps surprisingly positive. The work does show, for the first time, that the application of higher moment closures to model the initial onset of DDT is technically possible. Furthermore, the work illustrates that two physical limits on the chemical source term closure does in most cases bracket the experimental data. It is also shown that the transported PDF approach can be successfully applied to the modelling of premixed turbulent flames with scalar spaces of sufficient size to model auto-ignition type phenomena. It is also evident from the current work that the modelling of explosion kernels in pre-existing turbulence fields is very sensitive to both the details of the injection process and to the chemical source term closure. The present work does lay the foundations and also indicates the directions for further studies.
Author: Jiun-Ming Li
Publisher: Springer
ISBN: 3319689061
Category : Technology & Engineering
Languages : en
Pages : 246
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This book focuses on the latest developments in detonation engines for aerospace propulsion, with a focus on the rotating detonation engine (RDE). State-of-the-art research contributions are collected from international leading researchers devoted to the pursuit of controllable detonations for practical detonation propulsion. A system-level design of novel detonation engines, performance analysis, and advanced experimental and numerical methods are covered. In addition, the world’s first successful sled demonstration of a rocket rotating detonation engine system and innovations in the development of a kilohertz pulse detonation engine (PDE) system are reported. Readers will obtain, in a straightforward manner, an understanding of the RDE & PDE design, operation and testing approaches, and further specific integration schemes for diverse applications such as rockets for space propulsion and turbojet/ramjet engines for air-breathing propulsion. Detonation Control for Propulsion: Pulse Detonation and Rotating Detonation Engines provides, with its comprehensive coverage from fundamental detonation science to practical research engineering techniques, a wealth of information for scientists in the field of combustion and propulsion. The volume can also serve as a reference text for faculty and graduate students and interested in shock waves, combustion and propulsion.
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Category : Autograph albums
Languages : en
Pages :
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