Download or read book Experimental Study of Deflagration to Detonation Enhancement Techniques in a H2 Air Pulsed Detonation Engine written by and published by . This book was released on 2002 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments are performed on a number of deflagration-to-detonation (DDT) enhancement techniques for use in a H2/Air pulsed-detonation engine (PDE). The mechanism, speed and location of DDT for three configurations are considered, including a Shehelkin spiral, an extended cavity/spiral and a co-annulus. High speed digital imaging is used to track flame propagation. and simultaneous time-correlated pressure traces are used to record progress of the shock structure. It is found that DDT is initiated primarily through local explosions that are highly dependent on the particular geometry. In addition to various geometries. The effect of equivalence ratio and spark timing are also investigated.

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 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 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 29th International Symposium on Shock Waves 1 written by Riccardo Bonazza and published by Springer. This book was released on 2015-07-09 with total page 832 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings present the results of the 29th International Symposium on Shock Waves (ISSW29) which was held in Madison, Wisconsin, U.S.A., from July 14 to July 19, 2013. It was organized by the Wisconsin Shock Tube Laboratory, which is part of the College of Engineering of the University of Wisconsin-Madison. The ISSW29 focused on the following areas: Blast Waves, Chemically Reactive Flows, Detonation and Combustion, Facilities, Flow Visualization, Hypersonic Flow, Ignition, Impact and Compaction, Industrial Applications, Magnetohydrodynamics, Medical and Biological Applications, Nozzle Flow, Numerical Methods, Plasmas, Propulsion, Richtmyer-Meshkov Instability, Shock-Boundary Layer Interaction, Shock Propagation and Reflection, Shock Vortex Interaction, Shock Waves in Condensed Matter, Shock Waves in Multiphase Flow, as well as Shock Waves in Rarefield Flow. The two Volumes contain the papers presented at the symposium and serve as a reference for the participants of the ISSW 29 and individuals interested in these fields.

Download or read book The Fluidic Obstacle Technique written by Benjamin W. Knox and published by . This book was released on 2011 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current research explored the fluidic obstacle technique and obtained relative performance estimates of this new approach for enhancement of deflagration-to-detonation transition. Optimization of conventional physical obstacles has comprised the majority of deflagration-to-detonation enhancement research but these devices ultimately degrade the performance of a pulsed detonation engine. Therefore, a new approach has been investigated that demonstrates a fluidic obstacle has the potential to maximize turbulence production and enhance the flame acceleration process, leading to successful DDT. A fluidic obstacle is also able to reduce total pressure losses, "heat soaking", and ignition times. A reduction in these variables serves to maximize available thrust. In addition, the fluidic obstacle technique is an active combustion control method capable of adapting to off-design conditions. Steady non-reacting and unsteady reacting flow have been utilized in two facilities, namely the UB Combustion Laboratory and AFRL Detonation Engine Research facility, to provide experimental measurements and observations into the feasibility of this new approach.

Download or read book The Detonation Phenomenon written by John H. S. Lee and published by Cambridge University Press. This book was released on 2008-06-30 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the detonation phenomenon in explosives. It is ideal for engineers and graduate students with a background in thermodynamics and fluid mechanics. The material is mostly qualitative, aiming to illustrate the physical aspects of the phenomenon. Classical idealized theories of detonation waves are presented first. These permit detonation speed, gas properties ahead and behind the detonation wave, and the distribution of fluid properties within the detonation wave itself to be determined. Subsequent chapters describe in detail the real unstable structure of a detonation wave. One-, two-, and three-dimensional computer simulations are presented along with experimental results using various experimental techniques. The important effects of confinement and boundary conditions and their influence on the propagation of a detonation are also discussed. The final chapters cover the various ways detonation waves can be formed and provide a review of the outstanding problems and future directions in detonation research.

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 38th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit 02 3700 02 3749 written by and published by . This book was released on 2002 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Deflagration to Detonation Transition Processes in Pulsed Detonation Engines written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Detonability of Hydrocarbon Air Mixtures Using Combustion Enhancing Geometries for Pulse Detonation Engines written by Neil G. Sexton and published by . This book was released on 2001-06 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research studied combustion enhancing geometries and shock reflection on generating a hydrocarbon/air detonation wave in a combustion tube. Ethylene was used as a baseline fuel to determine the preferable geometries. Propane was then used in later testing because of its combustion similarities with heavy hydrocarbon fuels such JP5, JP8, and JP10. Three criteria were used to measure the effectiveness of the combustion enhancing geometries: ability to generate a detonation, wave speed, and time for shock formation. The evaluated geometries included flow-restricting orifice plates and a Schelkin spiral. The shock reflection was accomplished by a vertical fence (large orifice) placed in the last fourth of the tube length. The optimum geometry was found to be the orifice plate used in conjunction with the spiral. Detonations occurred when using ethylene in this configuration, but did not develop when using propane. Because propane's overall reaction rate is slower than that of simpler fuels, more large- and small-scale turbulence to further enhance combustion needs to be generated to create a detonation wave in a short distance when using complex hydrocarbons, such as propane.

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 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 Computational Study of Variable Fuel Air Ratio and Hydrogen Doping in a Rotating Detonation Engine written by and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotating detonation engines (RDEs) hold great promise as a technology for powering aviation engines. The pressure gain that results from continuously traversing detonation waves enables high theoretical performance compared to deflagration-based combustion. However, the harsh operating conditions inside an RDE restrict the availability of suitable experimental diagnostics to study these systems in detail and the range of spatial and temporal scales render numerical simulations of these systems difficult. In this study, we have combined adaptive mesh refinement and a robust shock-capturing approach to study RDE systems computationally using the compressible, reactive solver PeleC. Multi-species transport along with compressible Navier-Stokes equations are solved in the model along with finite-rate chemistry. Complex geometries are represented using an embedded boundary method with second-order spatial accuracy and the system is evolved in time using a second-order Runge-Kutta method. We present studies of a methane-air RDE system that is doped with varying levels of hydrogen. Our analysis focusses on how fuel mixture and doping levels effect the detonation flame structure and the generation of multiple wave modes.

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 Investigation on Novel Methods to Increase Specific Thrust in Pulse Detonation Engines Via Imploding Detonations written by and published by . This book was released on 2009 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulse Detonation Engines (PDE) are seen to be the next generation propulsion systems due to enhanced thermodynamic efficiencies based on the Humphrey cycle. One of the limitations in fielding practical designs has been attributed to tube diameters not exceeding 5 inches as the shock wave takes a long run distance for transition to detonation, thus potentially affecting specific thrust. Novel methods via imploding detonations were investigated to remove such limitations. During the study, a practical computational cell size was first determined so as to capture the required physics for transient detonation wave propagation using a Hydrogen-Air test case. Through a grid sensitivity analysis, one-quarter of the induction length was found sufficient to capture the experimentally observed initial wave transients. Test case models utilizing axisymmetric head-on implosions were studied in order to understand how the implosion process reinforces a detonation wave as it expands. This in effect creates localized overdriven regions, which maintains the transition process to full detonation. A parametric study was also performed to determine the extent of diameter increase and it was found that the detonations could be supported with no change in run distance even when the tube diameter exceeds 5 inches.