Numerical Investigation on Knock Combustion in a Diesel-Dimethyl Ether Dual-fuel Engine
Numerical Investigation on Knock Combustion in a Diesel-Dimethyl Ether Dual-fuel Engine
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柴油-二甲醚双燃料发动机爆震燃烧数值研究
DOI：
10.1021/acs.energyfuels.9b00695
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Dongxing Wang
中科院分区：
文献类型：
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作者：
Ying Wang;Chunlan Guo;Peng Wang;Dongxing Wang
对采用左舷预混二甲醚（DME）燃料的直喷柴油机进行了爆震数值研究。基于多维计算流体动力学（CFD）分析，模拟了发动机在不同工况下固定转速下的爆震燃烧，研究了预混二甲醚比、喷射正时和废气再循环（EGR）速率对爆震抑制的影响。采用简化的柴油-二甲醚动力学机制与CFD模型相结合，得到了计算域内各监测点的局部压力和自由基浓度。采用带通滤波的方法对压力数据进行处理，并以压力振荡的最大幅值作为爆震强度的评价指标。物种浓度分析也被用来量化这里的敲击声。研究结果表明，压力分布和主要中间物质分布可以为二甲醚-柴油双燃料预混压燃燃烧爆震的量化和预测提供有用信息。此外，EGR是降低爆震强度和延缓爆震发生的有效途径。降低二甲醚预混比和延迟喷射时间也可以减轻爆震。
Numerical investigation on knock was conducted in a direct-injection diesel engine with port premixed dimethyl ether (DME) fuel. Knock combustion at various engine operating conditions with a fixed speed was simulated, and the effects of premixed DME ratio, injection timing, and exhaust gas recirculation (EGR) rate on knock suppression were studied based on the multidimensional computational fluid dynamics (CFD) analysis. A reduced diesel–DME kinetic mechanism coupled with the CFD model was used to obtain local pressure and radical concentration at various monitoring locations within the computation domain. A method with a band-pass filter was then employed to deal with pressure data, and maximum amplitude of pressure oscillation was adopted as an evaluation index of the knock intensity. The analysis of species concentration was also used to quantify knock here. The research results indicated the profiles of pressure and major intermediate species could provide useful information to quantify and predict knock for DME–diesel dual-fuel premixed compression-ignition combustion. Moreover, using EGR was an effective way to reduce the knock intensity and delay the knock onset. A lower DME premixed ratio and retarded injection timing could also mitigate the knock.