Numerical Modeling of Shockwave Initiated Combustion of a Hydrogen-oxygen Mixture Within a Shock Tube PDF Download
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Author: Reed W. Forehand
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
Shock tubes are as close to an ideal reactor as most modern experiments can attain to examine chemical kinetics. As reaction temperatures drop, homogeneous combustion within a shock tube begins to exhibit inhomogeneous modes, which in a typical Hydrogen-Oxygen system are expressed as deflagration to detonation transition. Experimental results of such a system in the University of Central Florida’s low-pressure shock tube have been collected through end and side-wall imaging to analyze flame structure and chemical kinetics. The purpose of this work is to conduct a baselining of these results using both chemical and computational fluid dynamics modeling. The model will use the Siemens STAR-CCM+ computational fluid dynamics software in order to accurately simulate the system. A seven-step reaction mechanism will be used to accurately capture initialization, propagation, and termination of the combustion within an implicit unsteady, three-dimensional, direct eddy simulation solution on a well-conditioned mesh. The end goal of this study is to create a lightweight model of hydrogen-oxygen combustion with a shock tube for baselining purposes. Both a two- and three- dimensional model were applied in this effort. The simulation results indicate good conditioning and agreement with the experimental results, although some combustion phenomena are not captured as well as a higher fidelity, significantly more computationally expensive model would.
Author: Reed W. Forehand
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
Shock tubes are as close to an ideal reactor as most modern experiments can attain to examine chemical kinetics. As reaction temperatures drop, homogeneous combustion within a shock tube begins to exhibit inhomogeneous modes, which in a typical Hydrogen-Oxygen system are expressed as deflagration to detonation transition. Experimental results of such a system in the University of Central Florida’s low-pressure shock tube have been collected through end and side-wall imaging to analyze flame structure and chemical kinetics. The purpose of this work is to conduct a baselining of these results using both chemical and computational fluid dynamics modeling. The model will use the Siemens STAR-CCM+ computational fluid dynamics software in order to accurately simulate the system. A seven-step reaction mechanism will be used to accurately capture initialization, propagation, and termination of the combustion within an implicit unsteady, three-dimensional, direct eddy simulation solution on a well-conditioned mesh. The end goal of this study is to create a lightweight model of hydrogen-oxygen combustion with a shock tube for baselining purposes. Both a two- and three- dimensional model were applied in this effort. The simulation results indicate good conditioning and agreement with the experimental results, although some combustion phenomena are not captured as well as a higher fidelity, significantly more computationally expensive model would.
Author: Erik Ninnemann
Publisher:
ISBN:
Category :
Languages : en
Pages : 48
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Book Description
Shock tubes are considered ideal reactors and are used extensively to provide valuable chemical kinetic measurements, such as ignition delay times and in-situ species time-histories. However, due to nonideal affects the combustion of fuel inside shock tubes can become nonhomogeneous, particularly at low temperatures, which complicates the acquired data. In this work, the combustion of practical fuels used by society are investigated with high-speed imaging. First, high-speed images were captured through the end wall of the shock tube for two hydrogen-oxygen systems. The combustion process was found to initiate in two modes, one that is homogeneous across the fluid medium and one that proceeds through a deflagration to detonation channel. In the second part of this work, the shock tube test section was redesigned to promote optical access from the end and side walls of the shock tube test section. Two high-speed cameras were used to capture perpendicular views of the combustion of iso-octane and n-heptane, two primary reference fuels. A homogeneous and nonhomogeneous combustion process were seen for these fuels as well. Using the side view images, the impact of the sporadic ignition process was evaluated on commonly used diagnostics in shock tubes. Based on these results, it is recommended that shock tube diagnostics be confined to the homogeneous ignition modes of fuels. This is found to strongly correlate with the temperature of the combustion process, where high temperatures promote a homogeneous ignition event.
Author: Mouna Lamnaouer
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 219
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Book Description
An axi-symmetric shock-tube model has been developed to simulate the shock-wave propagation and reflection in both non-reactive and reactive flows. Simulations were performed for the full shock-tube geometry of the high-pressure shock tube facility at Texas A & M University. Computations were carried out in the CFD solver FLUENT based on the finite volume approach and the AUSM+ flux differencing scheme. Adaptive mesh refinement (AMR) algorithm was applied to the time-dependent flow fields to accurately capture and resolve the shock and contact discontinuities as well as the very fine scales associated with the viscous and reactive effects. A conjugate heat transfer model has been incorporated which enhanced the credibility of the simulations. The multi-dimensional, time-dependent numerical simulations resolved all of the relevant scales, ranging from the size of the system to the reaction zone scale. The robustness of the numerical model and the accuracy of the simulations were assessed through validation with the analytical ideal shock-tube theory and experimental data. The numerical method is first applied to the problem of axi-symmetric inviscid flow then viscous effects are incorporated through viscous modeling. The non-idealities in the shock tube have been investigated and quantified, notably the non-ideal transient behavior in the shock tube nozzle section, heat transfer effects from the hot gas to the shock tube side walls, the reflected shock/boundary layer interactions or what is known as bifurcation, and the contact surface/bifurcation interaction resulting into driver gas contamination. The non-reactive model is shown to be capable of accurately simulating the shock and expansion wave propagations and reflections as well as the flow non-uniformities behind the reflected shock wave. Both the inviscid and the viscous non-reactive models provided a baseline for the combustion model iii which involves elementary chemical reactions and requires the coupling of the chemistry with the flow fields adding to the complexity of the problem and thereby requiring tremendous computational resources. Combustion modeling focuses on the ignition process behind the reflected shock wave in undiluted and diluted Hydrogen test gas mixtures. Accurate representation of the Shock-tube reactive flow fields is more likely to be achieved by the means of the LES model in conjunction with the EDC model. The shock-tube CFD model developed herein provides valuable information to the interpretation of the shock-tube experimental data and to the understanding of the impact the facility-dependent non-idealities can have on the ignition delay time measurements.
Author: Hans Grönig
Publisher:
ISBN: 9783826581083
Category : Combustion
Languages : en
Pages : 101
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Book Description
Author: E. S. Oran
Publisher:
ISBN:
Category :
Languages : en
Pages : 37
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Book Description
Detailed one-dimensional calculations have been performed to simulate weak and strong ignition in reflected shock tube experiments in hydrogen-oxygen-argon mixtures. It is found that the experiment and simulations agree well in the strong ignition case studied. In the weak ignition case, the simulations show the same qualitative behavior as the experiment. Here ignition starts at a distance away from the reflecting wall at a time much earlier than the calculated chemical induction time. This latter effect is shown to arise because of the sensitivity of the chemical induction time to fluctuations in the calculation. In the calculations these fluctuations arise from small numerical inaccuracies. In experiments, they can arise from a number of sources including nonuniformities in the incident shock wave leading to non-uniform reflection, thermal conduction to the walls, and interactions with boundary layers. (Author).
Author: Gerald P. D'Arcy
Publisher:
ISBN:
Category : Blast effect
Languages : en
Pages : 154
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Book Description
Presented theoretically and experimentally are (1) the feasibility of simulating a nuclear blast environment by detonating a gas and (2) determination of the initial conditions of hydrogen-oxygen mixtures to yield blast waves of the same pressure-velocity relationship as that in air shock waves. When the theory was derived by predicting the characteristics of the simulated blast waves, a computer program was written. Experimental data were used to adjust the computed data. The experiments were conducted in a 13-inch-diameter, high-pressure shock tube and yielded four mixtures of hydrogen and oxygen capable of simulating shock waves with overpressures of from 300 to 1,200 psi. It was found that detonation waves may be substituted for air shock waves when the incident loading is important and that applications are generally limited to instances in which only one characteristic of an air shock is simulated. (Author)
Author: Gabi Ben-Dor
Publisher: Elsevier
ISBN: 0080533728
Category : Science
Languages : en
Pages : 2188
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Book Description
The Handbook of Shock Waves contains a comprehensive, structured coverage of research topics related to shock wave phenomena including shock waves in gases, liquids, solids, and space. Shock waves represent an extremely important physical phenomena which appears to be of special practical importance in three major fields: compressible flow (aerodynamics), materials science, and astrophysics. Shock waves comprise a phenomenon that occurs when pressure builds to force a reaction, i.e. sonic boom that occurs when a jet breaks the speed of sound.This Handbook contains experimental, theoretical, and numerical results which never before appeared under one cover; the first handbook of its kind.The Handbook of Shock Waves is intended for researchers and engineers active in shock wave related fields. Additionally, R&D establishments, applied science & research laboratories and scientific and engineering libraries both in universities and government institutions. As well as, undergraduate and graduate students in fluid mechanics, gas dynamics, and physics. Key Features* Ben-Dor is known as one of the founders of the field of shock waves* Covers a broad spectrum of shock wave research topics* Provides a comprehensive description of various shock wave related subjects* First handbook ever to include under one separate cover: experimental, theoretical, and numerical results
Author: Zonglin Jiang
Publisher: Springer Science & Business Media
ISBN: 3540270094
Category : Science
Languages : en
Pages : 1346
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Book Description
The 24th International Symposium on Shock Waves (ISSW24) was held at the Beijing Friendship Hotel during July 11-16, 2004, in Beijing. It was a great pleasure for the Local Organizing Committee to organize the ISSW in China for the first time, because forty-seven years have passed since the First Shock Tube Symposium was held in 1957 at Albuquerque. The ISSW24 had to be postponed for one year because of the SARS outbreak in Beijing shortly before the Symposium was scheduled to be held in 2003, but it has achieved success due to the continuous support and kind understanding from all the delegates. It is very heart-warming to have had such an experience and I am very happy to have served as chairman for the Symposium. I would like to thank all for the contributions and help that they have given us over the past three years, without which we would not have had the Symposium. A total of 460 abstracts were submitted to the ISSW24. Each of the abstracts was evaluated by three members of the Scientific Review Committee and the decision on acceptance wasmade based on the reviewers' reports. 195oral papers,including 9plenary lectures, wereaccepted to be presented in three parallel sessions, and 135poster papers in three dedicated poster sessions. Topics discussed in these papers cover all aspects ofshock wave research.
Author: Michael Anthony Valentino
Publisher:
ISBN:
Category :
Languages : en
Pages : 246
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Book Description
Author: F. Zhang
Publisher: Springer Science & Business Media
ISBN: 3540884475
Category : Science
Languages : en
Pages : 407
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Book Description
The fourth of several volumes on solids in this series, the six extensive chapters here are more specifically concerned with detonation and shock compression waves in reactive heterogeneous media, including mixtures of solid, liquid and gas phases.
