Download or read book Detonation Initiation by a Hot Turbulent Jet for Use in Pulse Detonation Engines written by D H. Lieberman and published by . This book was released on 2002 with total page 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 Detonation Control for Propulsion written by Jiun-Ming Li and published by Springer. This book was released on 2017-12-05 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Detonation Initiation in a Hot Jet and by Colliding Fragments written by Egil Borse and published by . This book was released on 1978 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report describes three phases with experimental observations and theoretical evaluations related to the initiation of detonation in a hot jet caused by the jet itself or by colliding fragments. The report is based upon an evaluation of accidental explosions where initiations of detonations in actual past accidents seem to be connected with the existence of a local constant volume combustion process inside a vapour cloud. There exist two plausible mechanisms for the initiation of detonation -- one is based upon the existence of a radical gradient in a hot jet, which during the initiation process amplifies the process by e.g. the SWACER mechanism through a critical length or volume until a self-sustained detonation wave is formed. -- the other mechanism is that a constant volume combustion (which produces the hot jet) causes metal to fragment and that the collisions between fragments or a wall produces a shock wave strong enough to initiate a detonation. Phase 1 and 2 of this report show that the first mechanism needs one additional factor: either a large scale vortex (phase 2) or the production of a Mach-Stem by merging two or more "low strength" shocks (phase 1). Phase 1 shows through streak and single spark Schlieren photography the most common mechanisms of detonation initiation. Phase 1 also gives additional evidence of the quenching characteristics of a detonation wave. Phase 2 gives evidence of the increased flame velocity in a hot jet and the formation of vortices by use of single spark Schlieren photography and pressure readings. The results from phase 2 indicate that the production of vortices is only secondary in the initiation of detonation in a hot jet; the vortices must only be of a particular size. The discussion in phase 1 shows that the production of Mach-Stem by merging two or more "low strength" shocks might be the prime mechanism of initiation in addition to a mechanism which could well be the SWACER mechanism. Phase 3 shows that detonation initiation caused by colliding fragments might be possible and is a more plausible explanation of past accidents involving initiation of detonation than the above mechanisms. That the pressure build-up is close to the natural frequency of diaphragm seems to be a necessary condition for initiation of detonation in the experimental apparatus used in phase 3. This might explain why detonation initiation in accidental gas explosions only occurs in relation to a constant volume combustion (explosion), but even then, only occasionally. A final theory of detonation initiation by e.g. a static electric discharge initiation a series of vortices building up a system of wavelets, is suggested. The wavelets discussed in phase 1 and the turbulence discussed as secondary to the wavelets in phase 2 might then form a process which is similar to the Swacer mechanism in theory, but not in the physics. There is no final evidence whether this process also is acting in phase 3, with or without help from the fragmentation. A static electric discharge might compete with the fragmentation theory in phase 3, or the shock reflection theory in phase 1, in explaining past accidents

Download or read book Detonation Initiation in a Pulse Detonation Engine with Elevated Initial Pressures written by Andrew George Naples and published by . This book was released on 2008 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: An experimental study was done to examine the effects of elevated initial tube pressure in the PDE. Measured parameters were the ignition time, DDT run-up distance, DDT times, and C-J velocity. Mixed with air, three fuels, i.e., aviation gasoline, ethylene, and hydrogen, were tested at various initial pressures and equivalence ratios. A stock automotive ignition system was employed, along with a transient and thermal plasma ignition system, to quantify the benefits of each. Measured results show a reduction in the ignition time of roughly 50% and in the DDT distance of roughly 30%, for all three fuels at an initial tube pressure of 3 atmospheres. At roughly 2 atmospheres of initial pressure the thermal plasma ignition system showed no benefit over the stock automotive ignition system. In addition to the experimental results, a brief Chemkin analysis was done to model the stock automotive ignition system.

Download or read book Development of a Gas Fed Pulse Detonation Research Engine written by R. J. Litchford and published by . This book was released on 2001 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation and Selection of an Efficient Fuel Air Initiation Strategy for Pulse Detonation Engines written by and published by . This book was released on 2005 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid and efficient initiation of hydrocarbon/air mixtures has been identified as one of the critical and enabling technologies for Pulse Detonation Engines (PDEs). Although the NPS Rocket Propulsion Laboratory has successfully demonstrated fuel/air detonations in a valveless pulse detonation engine using ethylene, propane, and JP-10 fuels, past engine designs have relied upon a sensitive fuel/oxygen initiator unit. To realize the increased thermodynamic efficiencies of PDEs and thus compete with ramjets and other supersonic platforms, it is imperative to eliminate any need for supplementary oxygen in an air-breathing PDE design. This thesis examined ignition technologies and initiator designs which did not require auxiliary oxygen, including capacitive discharge systems and the developing technology of Transient Plasma Ignition (TPI). The current NPS pulse detonation engine architecture was modified to evaluate the various ignition strategies in a PDE operating on an ethylene/air mixture at simulated supersonic cruising conditions. Comparisons were based upon ignition success rate, ignition delay time, detonation wave speed, and Deflagration-to-Detonation (DDT) distance. Reliability and performance of the TPI system proved to be superior to conventional ignition systems. Furthermore, successful initiation of a PDE operating at a frequency of up to 40 hertz was demonstrated without the use of supplementary oxygen.

Download or read book Detonation Initiation Studies and Performance Results for Pulsed Detonation Engine Applications written by and published by . This book was released on 2001 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Detonation Initiation in Pulse Detonation Engines written by Chiping Li and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Detonation Initiation of Hydrocarbon Air Mixtures in a Pulsed Detonation Engine written by and published by . This book was released on 2005 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book 38th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit 02 3900 02 3949 written by and published by . This book was released on 2002 with total page 496 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 Direct Initiation Through Detonation Branching in a Pulsed Detonation Engine written by Alexander R. Hausman and published by . This book was released on 2008 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 39th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit July 20 23 2003 Huntsville Alabama no 4799 written by and published by . This book was released on 2003 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power written by R. J. Litchford and published by . This book was released on 2001 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aerospace America written by and published by . This book was released on 2002 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock Waves Proceedings Of The 20th International Symposium In 2 Volumes written by Hans G Hornung and published by World Scientific. This book was released on 1997-01-22 with total page 1740 pages. Available in PDF, EPUB and Kindle. Book excerpt: The symposia take place every two years. They are the forum at which scientists concerned with shock waves present their research. They USE shock waves for chemical kinetics studies, for materials studies, and smashing kidney stones; they STUDY the phenomena associated with flows involving shock waves, such as supersonic flow, explosions, detonations, volcanic eruptions, and, in this symposium, even such with-it topics as impact of Shoemaker-Levy on Jupiter and blast waves in the World Trade Center. They also discover new, bigger and better ways of generating flows at hypervelocity speeds and develop their technological tools further.The international exchange of information is documented in the proceedings volumes, which have become a storehouse of information on the subject, documenting the history of this peculiar branch of science that involves chemists, physicists, engineers, geophysicists, material scientists and biologists.