Symposium (International) on Combustion最新文献

{"title":"Transient combustion response of homogeneous solid propellant to acoustic oscillations in a rocket motor","authors":"Tae-Seong Roh,&nbsp;Sourabh Apte,&nbsp;Vigor Yang","doi":"10.1016/S0082-0784(98)80084-2","DOIUrl":"10.1016/S0082-0784(98)80084-2","url":null,"abstract":"<div><p>Interactions between acoustic waves and the transient combustion response of a double-base homogeneous propellant in a rocket motor have been analyzed numerically. The analysis extends the previous work on gas-phase flame dynamics to include the coupling with condensed-phase processes. Consequently, a more complete description of propellant combustion response to imposed acoustic oscillations can be obtained. Emphasis is placed on the near-surface flame-zone physiochemistry and its coupling with unsteady propellant burning in an oscillatory environment. The formulation treats complete conservation equations and the finite-rate chemical kinetics in both the gas-phase and subsurface regions. The instantaneous propellant burning rate is predicted as part of the solution. Various distinct features of unsteady heat release arising from propellant combustion response in a motor with forced oscillations are studied systematically. As in the pure gas-phase dynamics of the previous case, the dynamic behavior of the luminous flame plays a decisive role in determining the motor stability characteristics. However, the propellant combustion response may qualitatively modify the temporal evolution of heat-release distribution in the luminous flame and as a result exerts a significant influence on the global stability behavior. The primary flame structure adjacent to the propellant surface is usually little affected by flow oscillation. This may be attributed to the large thermal inertial of the condensed phase, which tends to restrain the temperature variation in the near-surface zone in the present study of laminar flows. The situation with a turbulent flow may be drastically different, as turbulence may penetrate directly into the, primary flame and substantially change the local flame dynamics and transport phenomena.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 2","pages":"Pages 2335-2341"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80084-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"107419699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of hardware geometry on gas and drop behavior in a radial mixer spray","authors":"A. Ateshkadi,&nbsp;V.G. McDonell,&nbsp;G.S. Samuelsen","doi":"10.1016/S0082-0784(98)80043-X","DOIUrl":"10.1016/S0082-0784(98)80043-X","url":null,"abstract":"<div><p>The demands on current and future aero gas turbine combustors are requiring a greater insight into the role of the injector/done design and manufacturing tolerances. This paper systematically isolates manufacturing tolerances and focuses on hardware design. The target is the structure of the two-phase flow and combustion performance associated with practical injector/dome hardware. A spray injector with two radial inflow swirlers was custom designed to (1) maintain tight tolerances and strict assembly protocol and (2) thereby isolate the sensitivity of performance to hardware design. Although it represents practical hardware, the custom set is a unique modular design that (1) accommodates parametric variation in geometry, (2) retains symmetry, and (3) maintains effective area. Swirl sense and the presence of a venturi were found to be the most influential. The venturi acts as a fuel prefilming surface and constrains the highest fuel mass concentration to an annular ring near the centerline. Coswirl enhances the radial dispersion of the continuous phase, and counterswirl increases the level of mixing that occurs in the downstream region of the mixer. The combined effect of the two parameters (swirl sense and venturi) revealed that the largest drop sizes, which penetrate the continuous phase flow, are formed with coswirl and without venturi. The smallest drop size distributions were found to occur for the counterswirl configuration with venturi. In the case of counterswirl without venturi, the high concentration of fluid mass is found in the center region of the flow. The lean blowout (LBO) equivalence ratio was lower for counterswirl configurations for reasons that involved the coupling of the centerline recirculation zone with the location of high fuel concentration emanating from smaller droplets. In the coswirl configuration, a lack of fuel drops exists in the reaction anchoring region, thereby leading to poor stability characteristics.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 2","pages":"Pages 1985-1992"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80043-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"112082628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of dimethyl ether, NOx, and ethane on CH4 oxidation: High pressure, intermediate-temperature experiments and modeling","authors":"Toshiji Am Ano ,&nbsp;Frederick L. Dryer","doi":"10.1016/S0082-0784(98)80428-1","DOIUrl":"10.1016/S0082-0784(98)80428-1","url":null,"abstract":"<div><p>The effects of small amounts of dimethyl ether (DME), NO, and NO₂ on the autoignition and oxidation chemistry of methane, with an without small amounts of ethane present, were experimentally studied in a flow reactor at pressures and temperatures similar to those found in spark- and compression-ignition engines (under autoignition conditions). The reactions were studied at pressures from 10 to 18 atm, temperatures from 800 to 1060 K, and equivalence ratios from 0.5 to 2.0. It is found that 1% DME addition is as effective in stimulating the autoignition and oxidative behavior of methane as 3% C₂H₆ addition, and that NO_<em>x</em> at even ppm levels is more effective than hydrocarbon additives. For the same reaction time and temperatures below 1200 K, addition of small amounts of NO_<em>x</em> lowered the temperature at which reaction becomes significant by more than 200 K. Chemical kinetic mechanisms in the literature for the interactions of methane, ethane, and NO_<em>x</em> do not predict the reported observations well. The most significant rate-controlling reactions for CH₄ autoignition is found to be CH₃+HO₂=CH₃O+OH. Good agreement, with and without NO_<em>x</em> perturbations can be obtained by modifying the rate constants of three reactions (CH₃+HO₂=CH₃O+OH; CH₃+HO₂=CH₄+O₂: CH₂O+HO₂=HCO+H₂O₂) and by adding the reaction CH₃+NO₂=CH₃O+NO to the GRI-Mech v2.11 mechanism. These modifications do not significantly affect predictions for shock tube, flame, and other results used in developing GRI-Mech v2.11. Results strongly suggest that exhaust gas residuals and/or exhaust gas recirculation can have as profound an effect as natural gas contaminants on the apparent octane and cetane behavior.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 1","pages":"Pages 397-404"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80428-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"103296318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study of low- and high-temperature silane combustion","authors":"V.I. Babushok,&nbsp;W. Tsang,&nbsp;D.R. Burgess Jr.,&nbsp;M.R. Zachariah","doi":"10.1016/S0082-0784(98)80095-7","DOIUrl":"10.1016/S0082-0784(98)80095-7","url":null,"abstract":"<div><p>Self-ignition and flame propagation properties of silane combustion systems have been studied through computer simulations using a database of kinetic and thermodynamic information that is consistent with current understanding of the elementary processes. These new inputs include the mechanism for chain branching through the SiH₃ radical, rate constants for the reactions of HO₂ with silane and its breakdown products, and the reaction of SiO with oxygen. Over the entire temperature range, the simulations show two distinct mechanisms. At low temperatures, the kinetics of SiH₃ is controlling, whereas at high temperatures, SiH₂ chemistry is of key importance. The results demonstrate that the upper explosion limit and ignition at room temperature and 1 bar can be described by the same set of reactions. With the new database, many of the experimental observations can be reproduced, and predictions are made regarding dependencies on process parameters. These include the critical conditions for chain ignition, the dependence of the critical pressure on the ratio of silane and oxygen concentration, and the temperature dependence of the critical ratio of silane to oxygen concentration. A scenario for low-temperature ignition is presented. At high temperatures, the importance of condensation processes for accurate prediction of flame velocities is clear. For very lean flames, the maximum reaction rate occurs at the lower temperature region of the flame zone.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 2","pages":"Pages 2431-2439"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80095-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"93951360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational and experimental study of a forced, timevarying, axisymmetric, laminar diffusion flame","authors":"Rahima K. Mohammed,&nbsp;Michael A. Tanoff ,&nbsp;Mitchell D. Smooke,&nbsp;Andrew M. Schaffer,&nbsp;Marshall B. Long","doi":"10.1016/S0082-0784(98)80462-1","DOIUrl":"10.1016/S0082-0784(98)80462-1","url":null,"abstract":"<div><p>Forced, time-varying flames are laminar systems that help bridge the gap between laminar and turbulent combustion. In this study, we investigate computationally and experimentally the structure of an acoustically forced, axisymmetric laminar methane-air diffusion flame, in which a cylindrical fuel jet is surrounded by a coflowing oxidizer jet. The flame is forced by imposing a sinusoidal modulation on the steady fuel flow rate. Rayleigh scattering and spontaneous Raman scattering of the fuel are used to generate the temperature profile. Particle image velocimetry (PIV) is used to measure the fuel tube exit velocity over a cycle of the forcing modulation. CH flame emission measurements have been done to predict the excitedstate CH (CH^*) levels. Computationally, we solve the transient equations for the conservation of total mass, momentum, energy, and species mass with detailed transport and finite-rate C₂ chemistry submodels to predict the pressure, velocity, temperature, and species concentrations as a function of the two independent spatial coordinates and time. The governing equations are written in primitive variables. Implicit finite differences are used to discretize the governing equations and the boundary conditions on a nonstaggered, noniumiform grid. Modified damped Newton's method nested with a Bi-CGSTAB iteration is utilized to solve the resulting system of equations. Results of the study include a detailed description of the fluid dynamic-thermochemical structure of the flame at a 20-Hz frequency. A comparison of experimentally determined and calculated temperature profiles and CH^* levels agree well. Calculated mole fractions of species indicative of soot production (C₂H₂, CO) are compared against those levels in the corresponding steady flame and are observed to increase in peak concentration values and spatial extent. Analysis of acetylene production rates reveals additional significant production in the downstream region of the flame at certain times during the flame's cyclic history.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 1","pages":"Pages 693-702"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80462-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"98323575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Some chemical kinetics issues in reburning: The branching fraction of the HCCO+NO reaction","authors":"James A. Miller ,&nbsp;Joseph L. Durant ,&nbsp;Peter Glarborg","doi":"10.1016/S0082-0784(98)80410-4","DOIUrl":"10.1016/S0082-0784(98)80410-4","url":null,"abstract":"<div><p>We have determined theoretically some critical kinetic parameters in the mechanism of NO_<em>x</em> reburning under flow-reactor conditions. Specifically, using a variety of electronic-structure methods to investigate the potential energy surfaces and the maximum free-energy method of Quack and Troe to determine the resulting rate coefficients, we have deduced the values of <em>k</em>₂ and <em>k</em>₃ for the reactions HCNO+O a3HCO+NO (R2) and HCNO+OH a3HCOH+NO (R3) to be <em>k</em>₂≈7×10¹³ cm³/mole <em>s</em> and <em>k</em>₃≈2×10¹³ cm³/mole <em>s</em> independent of temperature for 300 K&lt;<em>T</em>&lt;2700 K. With such fast reactions converting HCNO to NO, a critical parameter in the reburn mechanism is <em>α(T)=k</em>_1b(<em>T</em>)/<em>k</em>₁(<em>T</em>), the branching fraction of the HCCO+NO reaction, HCCO+NO a3HCNO+CO (R1a) -a3HCN+CO₂ (R1b) -a3NONC+CO (R1c) Again using PES information from a variety of electronic-structure methods (including the QCISD barrier heights of Nguyen et al.), we have used the statistical-theoretical methodology of Miller, Parrish, and Brown to determine <em>α(T)</em>=0.985 exp (−<em>T</em>/1748), valid for 300 K&lt;<em>T</em>&lt;2000 K. Using a value of <em>k</em>₁=<em>k</em>_1a+<em>k</em>_1b+<em>k</em>_1c=2.4×10¹³ cm³/mole <em>s</em> independent of temperature (consistent with experiment), we have determined modified Arrhenius expressions for <em>k</em>_1a and <em>k</em>_1b, <em>k</em>_1a=1.17×10¹¹ <em>T</em>^0.65 cm³/mole <em>s</em> and <em>k</em>_1b=1.45×10¹⁶ <em>T</em>^−0.968 exp(−648/<em>RT</em>) cm³/mole <em>s</em> for 300 K&lt;<em>T</em>&lt;2000 K. Reaction (R1c) never contributes as much as 1% to the total rate coefficient. Our predictions for <em>α(T)</em> disagree with an experimental determination at <em>T</em>=700 K, but they are only slightly smaller than those used in modeling for 1000 K&lt;<em>T</em>&lt;1400 K.</p><p>The theoretical analyses and the reburn mechanism are discussed in detail.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 1","pages":"Pages 235-243"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80410-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113852028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Absolute radical concentration measurements and modeling of low-pressure CH4/O2/NO flames","authors":"W. Juchmann ,&nbsp;H. Latzel ,&nbsp;D.I. Shin ,&nbsp;G. Peiter ,&nbsp;T. Dreier ,&nbsp;H.-R. Volpp ,&nbsp;J. Wolfrum ,&nbsp;R.P. Lindstedt ,&nbsp;K.M. Leung","doi":"10.1016/S0082-0784(98)80436-0","DOIUrl":"10.1016/S0082-0784(98)80436-0","url":null,"abstract":"<div><p>An experimental and theoretical investigation of CH and CN radical formation and destruction in a low-pressure 13.3-hPa (10 Torr) premixed stoichiometric CH₄/O₂ flame seeded with NO is presented. Relative concentration profiles of CH and CN are measured by linear unsaturated laser-induced fluorescence (LIF). An absolute calibration of the relative profiles is obtained by Rayleigh scattering. A computational study is performed to identify key uncertainties in the formation and destruction chemistry of the CH and CN radicals. It is shown that the reaction of the CH radical with molecular oxygen is of particular importance in the present flame. Prevailing uncertainties in the reactions of ³CH₂ with hydrogen atoms and molecular oxygen are also discussed. The present quantitative measurements of the CN radical also indicate that further attention should be given to the formation and oxidation chemistry of HCN. Nevertheless, computational results are encouraging and reasonable agreement is obtained for both the CH and CN radicals. It is further shown that the effects on CH concentration levels of introducing NO dopants may be reproduced. Comparisons of absolute concentration profiles of CH₃, OH, and CH radicals as well as NO are also made with computed results obtained using GRI Mech. 2.11 and a reaction mechanism developed by Warnatz. The computations highlight significant differences in reaction paths and rate selection. The major areas of uncertainty are outlined and tentative recommendations are made in relation to the key reaction paths.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 1","pages":"Pages 469-476"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80436-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"105332465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A group combustion model for treating reactive sprays in I.C. engines","authors":"P. Stapf ,&nbsp;H.A. Dwyer ,&nbsp;R.R. Maly","doi":"10.1016/S0082-0784(98)80028-3","DOIUrl":"10.1016/S0082-0784(98)80028-3","url":null,"abstract":"<div><p>A model is presented and discussed treating the complex interactions between the fluid dynamics, the size, space, and time distributions of droplets as well as the combustion chemistry in a Diesel spray. The three-dimensional droplet characteristics are modeled with an overset gridding scheme, CHIMERA, and time dependent solutions of the Navier-Stokes equations have been carried out with the digital computer. The chemistry is treated with global and detailed reaction kinetics in a two-stage model. The global kinetics were used with the detailed Navier-Stokes equations, and the detailed kinetics were employed with a time dependent one-dimensional model that used information from the detailed model. The typical thermodynamic conditions of a modern truck engine have been used to provide insight into the details of ignition, combustion, and pollutant formation in spray commbustion. The study has considered droplet groups that have both uniform and different size droplets, and different groupings of the droplets have been investigated. The present model allows the droplets to move and vaporize in time, and the time development of ignition has been studied. The results indicate that group combustion effects have a dominant influence on all aspects of spray combustion.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 2","pages":"Pages 1857-1864"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80028-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"93508695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of combustion on flowfield in a model scramjet combustor","authors":"Shuhei Takahashi ,&nbsp;Kazunori Wakai ,&nbsp;Sadatake Tomioka ,&nbsp;Mitsuhiro Tsue ,&nbsp;Michikata Kono","doi":"10.1016/S0082-0784(98)80062-3","DOIUrl":"10.1016/S0082-0784(98)80062-3","url":null,"abstract":"<div><p>The effects of combustion on the change of the flowfield in a model SCRamjet combustor with a backward step is investigated experimentally and numerically. The main airflow has a Mach number of 2.0. The total temperature is 1000 K for cold flow and 1800 K for hot flow. Hydrogen fuel is injected parallel to the main airflow through a slit on the backward face of the step. The combustion mode is categorized in two modes. One is a weak combustion (WC) mode that is not accompanied by a shock wave, where the flowfield is similar to that in cold flow. Another is an intensive combustion (IC) mode that is accompanied by a shock wave, where the flowfield is much different from that in cold flow. In IC mode, a large separation region is generated behind the step by the shock wave, and the vortex generated at the region rolls the fuel up. The main reacting region is in the shear layer just behind the shock wave, where the main airflow bumps the rolled-up fuel, and the temperature is relatively high due to the shock wave. The flowfield is then controlled by the rate of mixing, leading to fast heat release, which raises the pressure level in the combustor and supports the shock wave. This passive feedback works, and both the mixing efficiency and the combustion efficiency become high. On the other hand, in WC mode, the reacting region spreads over the shear layer downstream of the step, and its heat release rate is lower than that in IC mode. The flowfield is then controlled by the rate of chemical reaction, and the combustion efficiency remains low.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 2","pages":"Pages 2143-2150"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80062-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"104070187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of stretch on the local structure of preely propagating premixed low-turbulent flames with various lewis numbers","authors":"Bruno Renou,&nbsp;Abdelkrim Boukhalfa,&nbsp;Daniel Puechberty,&nbsp;Michel Trinité","doi":"10.1016/S0082-0784(98)80480-3","DOIUrl":"10.1016/S0082-0784(98)80480-3","url":null,"abstract":"<div><p>An experimental investigation of the flame response to strain rate in the case of unsteady premixed low-turbulent flames is presented. In order to point out the fundamental aspects of the mutual interaction between combustion and turbulence, measurements of local flame properties (curvature, displacement speed) and tangential strain rate were performed under varying conditions of Lewis number and turbulence.</p><p>Three different mixtures (methane/air, propane/air, and hydrogen/air) were successively spark ignited in a vertical wind tunnel. The expanding flame freely propagated in a grid-generated decaying turbulent flow. An advanced field imaging technique coupling high-speed laser tomography and cross-correlation particle image velocimetry (PIV) was used to measure the temporal evolution of local flame stretch exerted by the turbulent cold flow.</p><p>Local flame curvature and local displacement speed were calculated from flame-front contours. Curvature probability density functions (PDFs) were negatively skewed, especially for nonunity Lewis numbers, and displacement speed distributions underlined the influence of local stretch and thermodiffusive effects on flame-speed variations. Tangential strain rate was determined by using the velocity field in the neighborhood of the flame front and appears to be independent of the Lewis numbers. A strong correlation between local flame curvature and tangential strain rate was demonstrated, underlining the cold flow effects on the local flame structure. The influences of turbulence and Lewis number were evaluated and compared with numerical simulations. Then, local flame stretch distributions were determined versus time, indicating that a significant proportion of the flame was under compression.</p></div>","PeriodicalId":101203,"journal":{"name":"Symposium (International) on Combustion","volume":"27 1","pages":"Pages 841-847"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0082-0784(98)80480-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"96256655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}