喷射策略对某重型柴油机高原燃烧特性的影响

为研究高原条件下不同喷射策略对某重型柴油机燃烧特性的影响。建立基于ECFM-3Z燃烧模型的某增压柴油机燃烧室三维模型并将其与平原台架试验结果进行对比验证,分析在海拔4 550 m条件下不同喷射策略对柴油机缸内燃烧过程的影响。结果表明,随着喷油提前角增大,单次喷射时缸内高温区域缩小,温度分布变得均匀,缸内预混合燃烧增强。和平原条件下的结果相比,喷油提前角的增大可以减少碳烟的排放但是增加了NO_x的排放。采用多次喷射策略时,预喷的提前可以使燃油与空气混合更充分,从而有助于主喷燃油更好地燃烧,功率能够得到进一步提升,较单次喷射NO_x排放增加,碳烟排放减少。根据模拟结果最终选择预喷提前角为22°CA BTDC和主喷提前角为2°CA BTDC的喷射策略,示功图面积较单次喷射相比有所提高,可恢复至平原的85.6%。

Influence of Injection Strategy on Plateau Combustion Characteristics of a Heavy Diesel Engine

In order to research the influence of different injection strategies on the performance of heavy-duty diesel engines under high altitude conditions, a three-dimensional model of a supercharged diesel engine chamber model is established and verified based on the ECFM-3Z combustion model. And the effects of different injection strategies on the in-cylinder combustion process at the altitude of 4550m are analyzed based on the verification of the plain bench test. The simulation results show that as the injection advance angle increases, the high temperature region in the cylinder shrinks when a single injection is used, the temperature distribution becomes uniform, the premixed combustion in the cylinder is enhanced. An increase in the fuel injection advance angle can reduce soot emissions but increase NOx emissions compared to the results under plain conditions. When using the multiple injection strategy, the advance of the pre-injection can make the fuel and air mix more fully, which helps the main injection fuel to burn better, the power can be further improved, but the average temperature inside the cylinder rises. However, due to the increase in the average internal temperature of the cylinder, the NOx emissions are increased compared with the single injection, and soot emissions are reduced. According to the simulation results, the injection strategy with the pre-ejection advance angle of 22°CA BTDC and the main spray advance angle of 2°CA BTDC is finally selected. The area of the indicator diagram is improved compared with the single injection, which can be restored to 85.6% of the plain.