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Shock Tube (shock + tube)
Selected AbstractsPrediction of jet flows in the supersonic nozzle and diffuserINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10-11 2005Yi Liu Abstract The authors' recently-developed code for a needle-free powdered vaccine delivery device, the epidermal powdered inject system (EPI), is summarized in this paper. The behaviour of supersonic jet flows, which accelerate micron sized powdered vaccines to penetrate human skin or mucosal tissue, is therefore of great importance. A well-established modified implicit flux vector splitting (MIFVS) solver for the Navier,Stokes equations is extended to study numerically the transient supersonic jet flows of interest. A low Reynolds number k,, turbulence model, with the compressibility effect considered, is integrated into MIFVS solver to predict the turbulent structures and interactions with inherent shock systems. The results for the NASA validation case NPARC, Venturi and contoured shock tube (CST) of the EPI system are discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Some recent finite volume schemes to compute Euler equations using real gas EOSINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2002T. Gallouėt Abstract This paper deals with the resolution by finite volume methods of Euler equations in one space dimension, with real gas state laws (namely, perfect gas EOS, Tammann EOS and Van Der Waals EOS). All tests are of unsteady shock tube type, in order to examine a wide class of solutions, involving Sod shock tube, stationary shock wave, simple contact discontinuity, occurrence of vacuum by double rarefaction wave, propagation of a one-rarefaction wave over ,vacuum', , Most of the methods computed herein are approximate Godunov solvers: VFRoe, VFFC, VFRoe ncv (,, u, p) and PVRS. The energy relaxation method with VFRoe ncv (,, u, p) and Rusanov scheme have been investigated too. Qualitative results are presented or commented for all test cases and numerical rates of convergence on some test cases have been measured for first- and second-order (Runge,Kutta 2 with MUSCL reconstruction) approximations. Note that rates are measured on solutions involving discontinuities, in order to estimate the loss of accuracy due to these discontinuities. Copyright © 2002 John Wiley & Sons, Ltd. [source] A shock tube study of cyclopentane and cyclohexane ignition at elevated pressuresINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2008Shane M. Daley Ignition delay times for cyclopentane/air and cyclohexane/air mixtures were measured in a shock tube at temperatures of 847,1379 K, pressures of 11,61 atm, and equivalence ratios of , = 1.0, 0.5, and 0.25. Ignition times were determined using electronically excited OH emission monitored through the shock tube endwall and piezoelectric pressure measurements made in the shock tube sidewall. The dependence of ignition time on pressure, temperature, and equivalence ratio is quantified and correlations for ignition time formulated. Measured ignition times are compared to kinetic modeling predictions from four recently published mechanisms. The data presented provide a database for the validation of cycloalkane kinetic mechanisms at the elevated pressures found in practical combustion engines. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 624,634, 2008 [source] Ignition and oxidation of 1-hexene/toluene mixtures in a shock tube and a jet-stirred reactor: Experimental and kinetic modeling studyINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2007M. Yahyaoui The oxidation of several binary mixtures 1-hexene/toluene has been investigated both in a shock tube and in a jet-stirred reactor (JSR). The self-ignition behavior of binary mixtures was compared to that of neat hydrocarbons studied under the same conditions. Furthermore, molecular species concentration profiles were measured by probe-sampling and GC/MS, FID, TCD analyses for the oxidation of the mixtures in a JSR. Experiments were carried out over the temperature range 750,1860 K. Mixtures were examined under two pressures 0.2 and 1 MPa, with 0.1% initial concentration of fuel. The equivalence ratio was varied from 0.5 to 1.5. The experiments were modeled using a detailed chemical kinetic reaction mechanism. The modeling study showed that interactions between hydrocarbons submechanisms were not limited to small reactive radicals. Other types of interactions involving hydrocarbon fragments derived from the oxidation of the fuel components must be considered. These interactions mainly consist of hydrogen abstraction reactions. For example, benzyl radical that is the major radical produced from the oxidation of toluene at high temperature can abstract hydrogen from 1-hexene and their products such as hexenyl radicals. Similarly, propyl, allyl, and hexenyl radicals that are the major radicals produced during 1-hexene oxidation at high temperature can abstract hydrogen from toluene. Improved modeling was achieved when such interaction reactions were included in the model. Good agreement between experimental and calculated data was obtained using the proposed detailed chemical kinetic scheme. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 518,538, 2007 [source] Kinetics of the thermal isomerization of 1,1,2,2-tetramethylcyclopropaneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2006David K. Lewis Reaction rates for the structural isomerization of 1,1,2,2-tetramethylcyclopropane to 2,4-dimethyl-2-pentene have been measured over a wide temperature range, 672,750 K in a static reactor and 1000,1120 K in a single-pulse shock tube. The combined data from the two temperature regions give Arrhenius parameters Ea=64.7 (±0.5) kcal/mol and log10(A, s,1) = 15.47 (±0.13). These values lie at the upper end of the ranges of Ea and log A values (62.2,64.7 kcal/mol and 14.82,15.55, respectively) obtained from three previous experimental studies, each of which covered a narrower temperature range. The previously noted trend toward lower Ea values for structural isomerization of methylcyclopropanes as methyl substitution increases extends only through the dimethylcyclopropanes (1,1- and 1,2-); Ea then appears to increase with further methyl substitution. In contrast, the pre-exponential factors for isomerization of cyclopropane and all of the methylcyclopropanes through tetramethylcyclopropane lie within ±0.3 of log10(A, s,1) = 15.2 and show no particular trend with increasing substitution. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 483,488, 2006 [source] A shock tube study of the reaction NH2 + CH4 , NH3 + CH3 and comparison with transition state theoryINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2003Soonho Song The rate coefficient for NH2 + CH4 , NH3 + CH3 (R1) has been measured in a shock tube in the temperature range 1591,2084 K using FM spectroscopy to monitor NH2 radicals. The measurements are combined with a calculation of the potential energy surface and canonical transition state theory with WKB tunneling to obtain an expression for k1 = 1.47 × 103T3.01e,5001/T(K) cm3 mol,1 s,1 that describes available data in the temperature range 300 ,2100 K. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 304,309, 2003 [source] Oxidation of small alkenes at high temperatureINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2002Barbara Heyberger If the mechanism of formation of alkenes, the main primary products of the combustion of alkanes above 1000 K, is now well understood, their ways of degradation have been much less studied. Following a previous modeling of the oxidation of propene in a static and a jet-stirred reactors by using an automatically generated mechanism, the present paper shows new validations of the same mechanism for ignition delays in a shock tube. It also describes the extension of the rules used for the automatic generation to the case of 1-butene. The predictions of the mechanism produced for the oxidation of 1-butene are compared successfully with two sets of experimental results: the first obtained in a jet-stirred reactor between 900 and 1200 K; the second being new measurements of ignitions delays behind reflected shock waves for temperatures from 1200 up to 1670 K, pressures from 6.6 to 8.9 atm, equivalence ratios from 0.5 to 2, and with argon as bath gas. Flux and sensitivity analyses show that the role of termination reactions involving the very abundant allylic radicals is less important for 1-butene than for propene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 666,677, 2002 [source] Shock tube pyrolysis of thiopheneINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2003Hafeez Ur Rahman Memon Abstract The kinetics of the thermal decomposition of thiophene diluted in argon have been studied behind reflected shock waves in a single pulse shock tube over the temperature range 1598,2022 K and pressures between 2.5 and 3.44 bar. Product yields and composition were determined using capillary column gas chromatography with flame ionization detection and flame photometric sulphur selective detection. The principal hydrocarbon product at all temperatures was ethyne. Ethanethiol was found to be the major sulphur product together with H2S formed in significant concentrations at lower temperatures. Carbon disulphide was also formed at higher temperatures. Additional reaction products were CH4, C2H4, C3H4, C4H3, C4H6, C4H4, C6H6 and C4H2 with some traces were found of C5 and C6H5 species. It was concluded that pyrolysis of thiophene is initiated by C,S bond fission to form the C4H4S radical which reacts to give C4H3 + SH together with the reaction giving C3H4 + CS. The rate expression obtained for the pyrolysis reaction was k (C4H4S)=2.2×1011 exp (270 kJ mol,1) s,1. Copyright © 2002 John Wiley & Sons, Ltd. [source] Combustion Measurements of Fuel-Rich Aluminum and Molybdenum Oxide Nano-Composite MixturesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010Tim Bazyn Abstract Fuel rich nano-composite powders of aluminum and molybdenum oxide were tested for ignition and combustion behind the incident and reflected shock waves in a shock tube. The powders consisted of approximately 10,,m particles, each of which contained Al and MoO3 mixed by mechanical alloying on the nano-scale. These powders were aluminum rich with composition ratios of 4,:,1, 8,:,1, and 16,:,1 Al,:,MoO3 by mass. Ignition tests were performed behind incident shocks for temperatures in the range of 900 to 1500,K. From these tests, ignition delay times were obtained, and some information on combustion duration was also derived. Samples were tested in air at 0.2,MPa, and compared against nano-Al, 2.7,,m Al, and 10,,m Al baselines. Ignition results for the baseline Al cases were as expected: 10,,m Al not igniting until 2000,K, 2,,m Al igniting down to ,1400,K, and n-Al igniting as low as 1150,K. The thermite samples showed considerable improvement in ignition characteristics. At the lowest temperature tested (900,K), both the 8,:,1 and 4,:,1 samples ignited within 250,,s. The 16,:,1 sample (94% Al) ignited down to 1050,K , which represents an improvement of roughly 1000,K over baseline Al with only a small energetic penalty. In all cases, the ignition delay increased as the amount of MoO3 in the composite was reduced. The 4,:,1 nano-composite material ignited as fast or faster than the n-Al samples. Ignition delay increased with decreasing temperature, as expected. Emission spectra and temperature data were also taken for all samples using high-speed pyrometry and time-integrated spectroscopy. In these cases, measurements were made behind the reflected shock using end-wall loading, though the conditions (temperature, pressure, and gas composition) were identical to the incident shock tests. Spectroscopy showed strong AlO features in all the samples, and the spectra fit well to an equilibrium temperature. Broadband, low resolution spectra were also fit to continuum, gray body temperatures. In general, the observed temperatures were reasonably close to 3500,K, which is similar to the combustion temperatures of pure aluminum under these conditions. [source] | |||||||||||||