CAREER: Influence of Unsteady Stretch on Premixed Flame Kernel Growth
CAREER: Influence of Unsteady Stretch on Premixed Flame Kernel Growth
批准号:
9702277
负责人:
William Roberts
金额:
$23.0万
依托单位国家:
美国
项目类别:
Standard Grant
财政年份:
1997
资助国家:
美国
项目状态:
已结题
起止时间:
1997-05-15 至 2001-10-31
中文摘要
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英文摘要
ABSTRACT CTS-9702277 This is study of the interactions of a spark-generated flame kernel at various stages of growth with a single, well-defined eddy of known velocity and length scale in order to identify the optimal hydrodynamic flowfield for the fuel-air mixture in a modern internal combustion (IC) engine. It is intended to identify which eddies are most beneficial and which are most beneficial and which a re most destructive in terms of kernel growth for various kinetics parameters such as equivalence ratio and Lewis number. It is known that at low to moderate turbulence levels there is a marked increase in the burning rate and in the flammability limits of the premixed reactants, but that this reverses as turbulence intensity increases and the length scale of the eddies become small compared to the reaction zone, since the eddies are now able to locally quench the flamefront. Advanced laser diagnostics are used to measure temperature, velocity field, and state of reaction. Hydroxyl and methylidine radicals are detected to locate the reaction zone and to indicate the state of the reaction; their absence indicates a quenched flamefront. Temperature is measured by Rayleigh scattering and by seeded nitric-oxide planar laser-induced fluorescence (PPLIF), while particle-image velocimetry (PIV) is used to measure the two-dimensional velocity field and thereby determine the local, instantaneous strain executed on the flame kernel by the local flowfield. In an internal combustion engine, the spark generates a flame kernel that may transfer its energy to the fuel-air mixture resulting in a vigorous, self-sustaining flame front, or, alternatively, may be quenched (extinguished) by a combination of hydrodynamic strain and curvature, collectively termed stretch. In the case of localized extinction, the kernel may survive but exhibit a severe degradation of ovepall combustion efficiency and in increase in pollutant emissions. Perturbation of kernel growth rate is the major cause of cycle -to-cycle variations in engines. Thus understanding of this phenomenon is the key to engines that give smooth, efficient, and clear performance.
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SGER: Effects of Thyroxine on Peripheral Imprinting
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CONNECTION to the INTERNET
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Mathematical Sciences Computing Research Environments
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批准号:9106029
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Theoretical Studies of the Structure and Dynamics of Cloudy Interstellar Medium Spiral Galaxies
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财政年份:1988
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依托单位:
Acquisition of Mathematical Sciences Research Equipment
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批准号:8304459
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资助金额:$3.2万
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Galaxies, the Interstellar Medium, the External Environment:Galactic Gas Dynamics and Evolutionary Simulations
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资助金额:$11.43万
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Pre-College Teacher Development
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批准号:8001236
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财政年份:1980
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Normal Spirals, Barred Spirals, and Active Galaxies: Large-Scale Gas Dynamics in Galaxies
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批准号:7909935
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项目类别:Standard Grant
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资助金额:$7.77万
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财政年份:1979
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依托单位:
Summer Pre-College Teacher Development Project in Earth Sciences
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批准号:7714193
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资助金额:$1.63万
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依托单位:
The Bar Structure in Barred Spiral Galaxies
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资助金额:$9.44万
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依托单位:
海外基金