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首页> 美国政府科技报告 >Cycle to cycle variations in spark ignition engines - The effects of fluid flow and gas composition in the vicinity of the spark plug on early combustion
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Cycle to cycle variations in spark ignition engines - The effects of fluid flow and gas composition in the vicinity of the spark plug on early combustion

机译：循环到火花点火发动机的循环变化 - 火花塞附近的流体流动和气体成分对早期燃烧的影响

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To reveal the influence of fluid flow on early combustion, simultaneous measurements of fluid flow and combustion were performed. The fluid flow was measured with Laser Doppler Velocimetry (LDV). The combustion was monitored by two different techniques. The pressure in the cylinder was used in a heat release calculation to extract duration from ignition to a percentage heat released. The very early flame propagation was detected with two Schlieren imaging systems. The results show that, if the fuel and air are well mixed and the engine load is high, the dominant cause of variations in early combustion is the flow situation in the vicinity of the spark plug. The very early flame is most influenced by the mean velocity. This is probably due to the cooling effect of the combustion chamber walls. Approximately five crank angle degrees after ignition, the high frequency turbulence is more important. A frequency-resolved analysis of the turbulence revealed a higher correlation between the energy content in the frequency interval 4-6 kHz and early combustion rate. With the use of Taylor's hypothesis this can be transferred to eddies with a size of 0.5-l.5 mm. Fuel concentration measurements with Laser Induced Fluorescence (LIF) in the vicinity of the spark plug revealed an inhomogeneous charge if port fuel injection was used. A dramatically increased fluctuation of early combustion, from cycle to cycle was then detected. This decrease of combustion stability could be explained by the fluctuating fuel concentration measured with LIF. Water content measurements with LIF showed a cycle to cycle correlation between early combustion rate and residual gas concentration in the vicinity of the spark plug. The increased combustion fluctuation found with residuals at part load could only to a small extent be explained by the residual concentration obtained with LIF. 75 refs, 34 figs, 4 tabs

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