Download or read book Reduction in the Run up Distance for the Deflagration to detonation Transition and Applications to Pulse Detonation Combustion written by Joshua Allen Terry Gray and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advanced Turbulent Combustion Physics and Applications written by N. Swaminathan and published by Cambridge University Press. This book was released on 2022-01-06 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore a thorough and up to date overview of the current knowledge, developments and outstanding challenges in turbulent combustion and application. The balance among various renewable and combustion technologies are surveyed, and numerical and experimental tools are discussed along with recent advances. Covers combustion of gaseous, liquid and solid fuels and subsonic and supersonic flows. This detailed insight into the turbulence-combustion coupling with turbulence and other physical aspects, shared by a number of the world leading experts in the field, makes this an excellent reference for graduate students, researchers and practitioners in the field.
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 Applications of Calorimetry written by Jose Luis Rivera Armenta and published by BoD – Books on Demand. This book was released on 2022-06-23 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Calorimetry is used to measure the transfer and exchange of heat. It is a technique that has applications in different research and industrial sectors. It can be applied in kinetic studies as well as to measure physical changes of first- and second-order transitions such as glass transition, melting, and crystallization. It can also be used to evaluate thermodynamic parameters. This book reports on calorimetry in three sections: “Applications in General”, “Calorimetry in Materials”, and “Calorimetry in Biotechnology”.
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 Run Up Distance From Deflagration to Detonation In Fast Flames written by Mohamed Saifelislam Abdelgadir Ahmed and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the process of deflagration-to-detonation transition (DDT) in reactive gases, the flame typically accelerates first to the choked flame condition (known as a Chapman-Jouguet deflagration), where it propagates at the sound speed with respect to the product gases. Subsequently, the choked flame may transit to a detonation. In the present study, the transition length from choked flames to detonations was measured experimentally in laboratory-scale experiments in methane, ethane, ethylene, acetylene, and propane with oxygen as oxidizer. The choked flames were first generated following the quenching of an incident detonation after its interaction with cylindrical obstacles with two different blockage ratios, 75\% and 90\%. Comparison with a recently proposed model confirms that these are Chapman-Jouguet deflagrations. The subsequent acceleration was monitored via large-scale time-resolved shadowgraphy. The mechanism of transition was found to be through the amplification of transverse waves and hot spot ignition from local Mach reflections. The transition length was found to correlate very well with the mixture's sensitivity to temperature and pressure fluctuations. These fluctuations could be connected to a unique parameter (X), introduced by Radulescu. The parameter is the product of the non-dimensional activation energy (Ea/RT) and the ratio of chemical induction to reaction time (ti/tr). Mixtures with a higher X were found to be more prompt to hot spot ignition and amplification of the fast flame into detonations. The run-up distance for unstable mixtures was found to be much shorter than anticipated from a model neglecting the fluctuations in a 1-D framework. The run-up distance was also correlated to the detonation cell size, yielding LDDT ̃7 - 50 cells, with the proportionality coefficient depending on X and the obstacle blockage ratio. Finally, a unique correlation for the run-up distance is proposed, yielding LDDT ̃3000 c tr, where c is the sound speed in the shocked non-reacted gas, valid for large X.
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 Influence of Ignition Energy Ignition Location and Stoichiometry on the Deflagration to Detonation Distance in A Pulse Detonation Engine written by John P. Robinson and published by . This book was released on 2000-06 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The feasibility of utilizing detonations for air-breathing propulsion is the subject of a significant research effort headed by the Office of Naval Research. Pulse Detonation Engines (PDE) have a theoretically greater efficiency than current combustion cycles. However, pulse detonation technology must mature beginning with research in the fundamental process of developing a detonation wave. This thesis explores various ignition conditions which minimize the deflagration-to- detonation transition distance (Xddt) of a single detonation wave in a gaseous mixture.
Download or read book Initiation Mechanisms of Low loss Swept ramp Obstacles for Deflagration to Detonation Transition in Pulse Detonation Combustors written by Charles B. Myers and published by . This book was released on 2009 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to enhance the performance of pulse detonation combustors (PDCs), an efficient deflagration-to-detonation transition (DDT) process is critical to maintain the thermodynamic benefits of detonation-based combustion systems and enable their use as future propulsion or power generation systems. The DDT process results in the generation of detonation and can occur independently, but the required length is excessive in many applications and also limits the frequency of repeatability. Historically, obstacles have been used to reduce the required distance for DDT, but often result in a significant total pressure loss that lessens the delivered efficiency advantages of PDCs. This thesis evaluated various swept-ramp obstacle configurations to accelerate DDT in a single event PDC. Computer simulations were used to investigate the three-dimensional disturbances caused by various swept-ramp configurations. Experimental tests were conducted using various configurations that measured combustion shockwave speed and flame front interactions with the swept-ramp obstacles. Detonation was verified across the instrumented section through high-frequency pressure transducers, and experimental data proved that swept-ramp obstacles successfully accelerate the DDT process with minimal pressure losses.
Download or read book The Effect of Initial Temperature on Flame Acceleration and Deflagration to detonation Transition Phenomenon written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The High-Temperature Combustion Facility at BNL was used to conduct deflagration-to-detonation transition (DDT) experiments. Periodic orifice plates were installed inside the entire length of the detonation tube in order to promote flame acceleration. The orifice plates are 27.3-cm-outer diameter, which is equivalent to the inner diameter of the tube, and 20.6-cm-inner diameter. The detonation tube length is 21.3-meters long, and the spacing of the orifice plates is one tube diameter. A standard automobile diesel engine glow plug was used to ignite the test mixture at one end of the tube. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in DDT corresponded to the mixture whose detonation cell size, [lambda], was equal to the inner diameter of the orifice plate, d (e.g., d/[lambda]=1). The only exception was in the dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/[lambda] equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 mIs and then decelerated to below 2 mIs. By maintaining the first 6.1 meters of the vessel at the ignition end at 400K, and the rest of the vessel at 650K, the DDT limit was reduced to 9.5 percent hydrogen (d/[lambda]=4.2). This observation indicates that the d/[lambda]=1 DDT limit criteria provides a necessary condition but not a sufficient one for the onset of DDT in obstacle laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the point of detonation initiation, referred to as the run-up distance, was found to be a function of both the hydrogen mole fraction and the mixture initial temperature. Decreasing the hydrogen mole fraction or increasing the initial mixture temperature resulted in longer run-up distances. The density ratio across the flame and the speed of sound in the unburned mixture were found to be two parameters which influence the run-up distance.
Download or read book The Effect of Axial Spacing of Constant and Variable Blockages on the Deflagration to detonation Transition in a Pulse Detonation Engine written by Nicole Gagnon and published by . This book was released on 2016 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was conducted into the effects of obstacle spacing on the deflagration-to-detonation transition section length in a pulse detonation engine. Testing was conducted with one hundred and ninety-five different obstacle, and spacing configurations. The configurations included constant, as well as variable spacing between obstacles. The goal of this investigation was to correlate the spacing between obstacles and the blockage ratio of the obstacles with the detonation success and the shortening of the DDT section. The ten cases that achieved the highest percentage of detonations were investigated further to determine the distance needed for the deflagration-to-detonation transition. A 33% blockage ratio was the most successful to induce turbulence and not quench the detonation wave. With these conditions, DDT was achievable with 100% success in a section whose length was 31 times the inner diameter of the DDT section. Detonation was unachievable in 82 times the inner diameter in a "smooth" tube. This is a greater than 63% decrease in detonation transition length. This decrease in length will further facilitate the integration of pulse detonation engines into gas turbine engines.
Download or read book Hydrogen for Future Thermal Engines written by Efstathios-Al. Tingas and published by Springer Nature. This book was released on 2023-07-14 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the potential of hydrogen combustion in thermal engines and serves as a foundation for future research. Hydrogen, a well-established energy carrier, has been used in internal combustion engines for centuries, but despite progress and industry interest, hydrogen engines have yet to reach mass production. In light of recent efforts to combat climate change with clean energy and environmentally-friendly technologies, the use of hydrogen in thermal engines is gaining momentum. This book examines the unique challenges of hydrogen combustion due to its wide flammability limits, high auto-ignition temperature, and high diffusivity. It reviews current knowledge on the fundamental and practical aspects of hydrogen combustion and considers current developments and potential future advancement.
Download or read book High Speed Deflagration and Detonation Fundamentals and Control International Colloquium on Control and Detonation Processes Held in Moscow Russia on July 4 7 2000 written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Twenty two papers on fundamentals of high-speed deflagrations and detonations written by international experts are assembled in this volume. The papers have been presented at the International Colloquium on Control of Detonation Processes held in Moscow, Russia on July 4-7, 2000. Various aspects of deflagration to detonation transition as well as direct detonation initiation in gaseous and heterogeneous media are discussed with the emphasis on control of the predetonation distance and parameters of transient high-speed combustion regimes. Applications of various explosion control techniques to pulsed detonation engines (PDE) are described.
Download or read book Journal of Propulsion and Power written by and published by . This book was released on 2008 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Evaluation of Straight and Swept Ramp Obstacles on Enhancing Deflagration to Detonation Transition in Pulse Detonation Engines written by Carlos A. Medina and published by . This book was released on 2006 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of detonations to achieve thrust in pulse detonation engines (PDEs) offers significant advantages in efficiency, simplicity, and versatility. An enabling mechanism for practical PDE implementation will likely utilize an efficient deflagration-to-detonation transition (DDT) process. This method simplifies detonation generation, but the required length is prohibitive in many applications and limits the frequency of repeatability. Obstacles have historically been employed to minimize the DDT distance, but often result in significant total pressure losses that degrade the delivered efficiency advantages of PDEs. This thesis explored the use of straight and swept ramp obstacles to accelerate DDT while minimizing the overall pressure losses. Computer modeling examined three-dimensional disturbances caused by such obstacles. Experimental tests measured combustion shockwave speed, flame velocity, and flame front interactions with obstacles. Evaluations were completed for several straight ramp obstacle configurations in a modeled two-dimensional flow. The placement of consecutive ramps resulted in flame acceleration accompanied by significant pressure spikes approaching 500 psi. Although detonation was not verified across the instrumented section, experimental data prove that straight ramp obstacles successfully accelerate the DDT process. Computer modeling predicts that swept ramps may be even more effective by introducing streamwise vorticity with a relatively low pressure drop.
