Ignition delays in diesel combustion and intake gas conditions
Ignition delays in diesel combustion and intake gas conditions
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DOI：
10.1177/1468087417731410
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发表时间：
2018-10
影响因子：
2.5
通讯作者：
H. Ogawa;A. Morita;Katsushi Futagami;Gen Shibata
中科院分区：
文献类型：
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作者：
H. Ogawa;A. Morita;Katsushi Futagami;Gen Shibata
在一台单缸自然吸气直喷式柴油机（缸径110 mm，冲程106 mm，冲程容积1007 cm ~ 3）上，测量了4种十六烷值和3种压缩比下不同进气条件（包括不同氧浓度随废气再循环量和不同进气温度的变化）下柴油燃烧的着火延迟。该发动机具有共轨燃料喷射系统，该共轨燃料喷射系统可以设置为可选的喷射正时，并且具有带针升程传感器的喷射器，以精确地估计喷射正时。进气氧浓度由废气再循环气体的量设定，进气温度由进气管中的水冷式废气再循环冷却器和电加热器改变。三个压缩比，16.7，18.0，和21.3，建立了三个活塞的不同空腔体积。四种不同十六烷值的燃料，32（CN 32），45（CN 45），57（CN 57），和78（CN 78），由正链烷烃和异链烷烃组成，进行了检查的三个压缩比，并讨论了废气再循环和进气温度的影响，为12个组合的压缩比和十六烷值。结果表明，在相同十六烷值和压缩比下，着火延迟期随冷却废气再循环改变的进气氧浓度降低量的1.67次方线性增加。点火延迟随进气温度的降低而线性增加，并且点火延迟的增加程度在十六烷值较低的燃料和较低的压缩比下更显著。在进气氧浓度为21%~ 11%、进气温度为40°C ~ 100°C的实际工况下，点火延迟随进气氧浓度的变化比随进气温度的变化更显著。点火延迟随着压缩比的降低而线性增加，并且在进气氧浓度较低和十六烷值较低的燃料的情况下，点火延迟随着压缩比的降低而增加的程度较大。由于较高的缸内气体压力，在上止点处相同缸内气体温度的情况下，较高压缩比下的点火延迟显著短于较低压缩比下的点火延迟。在较低的进气氧浓度和较低的压缩比下，随着十六烷值的降低，着火延迟的增加程度更加显著，并且着火延迟随着十六烷值增加的0.25次幂线性减小。
Ignition delays in diesel combustion under several intake gas conditions, including different oxygen concentrations changed with exhaust gas recirculation quantities and different intake gas temperatures, were measured for four cetane numbers and three compression ratios in a single-cylinder, naturally aspirated, direct injection diesel engine (bore: 110 mm, stroke: 106 mm, and stroke volume: 1007 cm3). The engine has a common rail fuel injection system which can be set to optional injection timings and has an injector with a needle lift sensor to accurately estimate the injection timing. The intake oxygen concentrations were set by the quantity of exhaust gas recirculation gas, and the intake gas temperatures were changed with a water-cooled exhaust gas recirculation cooler and an electric heater in the intake pipe. Three compression ratios, 16.7, 18.0, and 21.3, were established with three pistons of different cavity volumes. Four fuels with different cetane numbers, 32 (CN32), 45 (CN45), 57 (CN57), and 78 (CN78), consisting of normal and isoparaffins, were examined for the three compression ratios, and the influence of exhaust gas recirculation and intake gas temperature is discussed for 12 combinations of compression ratios and cetane numbers. The results showed that the ignition delay increases linearly with the 1.67 power of the decrease in the intake oxygen concentration changed with cooled exhaust gas recirculation at the same cetane number and the same compression ratio. The ignition delay increases linearly with lowering intake gas temperatures, and the degree of increase in the ignition delay is more significant with lower cetane number fuels and lower compression ratios. Under practical conditions with the intake oxygen concentration between 21% and 11% and the intake gas temperature between 40°C and 100°C, the changes in ignition delays with the intake oxygen concentration are more significant than the changes with intake gas temperature. The ignition delay increases linearly with lowering compression ratios, and the degree of increase in the ignition delay with reductions in the compression ratio is larger in the cases with lower intake oxygen concentrations and lower cetane number fuels. The ignition delays at the higher compression ratios are significantly shorter than with the lower compression ratios in the case of the same in-cylinder gas temperature at top dead center due to higher in-cylinder gas pressures. The degree of increase in the ignition delay with lower cetane numbers is more significant at lower intake oxygen concentrations and lower compression ratios, and the ignition delay decreases linearly with the 0.25 power of the increase in cetane numbers.