Numerical investigation of dual-fuel injection timing on air-fuel mixing and combustion process in a novel natural gas-diesel rotary engine
Numerical investigation of dual-fuel injection timing on air-fuel mixing and combustion process in a novel natural gas-diesel rotary engine
复制标题
新型天然气-柴油旋转发动机中空气-燃料混合和燃烧过程双燃料喷射正时的数值研究
DOI：
10.1016/j.enconman.2018.09.050
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发表时间：
2018
影响因子：
10.4
通讯作者：
Lu Yao
中科院分区：
文献类型：
--
作者：
Chen Wei;Pan Jianfeng;Fan Baowei;Otchere Peter;Miao Nannan;Lu Yao
本研究旨在进一步提高柴油机的燃烧效率，并在这方面对一种新型的天然气-柴油转子发动机(NG-DRE)进行了数值研究。在实验验证的计算流体力学(CFD)模型的基础上，采用天然气喷射+柴油直喷的方式，对天然气直喷式柴油发动机进行了三维动态数值研究。探讨了天然气喷油正时(NGIT)和柴油喷油正时(DIT)对空燃混合、燃烧和排放特性的影响。仿真结果表明，NG-DRE的性能优于DRE。在整个空燃混合过程中，由于天然气具有良好的扩散特性，其运动易受涡度密度的影响，而对柴油运动的影响相对较小。在助燃时刻，天然气主要集中在燃烧室的后部，柴油主要集中在燃烧室的前部和中部。由于混合时间较短，延迟了NGIT和DIT，混合物变得更加集中。此外，延迟的NGIT和DIT导致了压力和燃烧速率的提高，而对于进一步延迟的DIT，由于压力负功而导致压力降低。综合发动机的动力性和排放性能，对于双燃料喷射方案，340°CA BTDC和70°CA BTDC分别是天然气和柴油的首选应用方案。其最高燃烧压力(Pmax)分别提高了16.34%和27.38%，但由于混合气浓度的增加，碳烟分别增加了0.023%和0.054%，一氧化碳(CO)值也分别增加了0.026%和0.039%。
This study aimed at further improving the combustion efficiency of the diesel rotary engine (DRE), and in this regard a novel natural gas-diesel rotary engine (NG-DRE) was numerically studied. Based on the experimental validated computational fluid dynamics (CFD) model, a 3D-dynamic numerical study of the NG-DRE was carried out by adopting NG port injection plus diesel direct injection mode. The influence of natural gas injection timing (NGIT) and diesel injection timing (DIT) on air-fuel mixing, combustion and emission characteristics were explored. Simulation results showed that NG-DRE performance was better than DRE. During the entire air-fuel mixing process, NG movement was easily affected by the vorticity density due to its good diffusion characteristics, however its influence on diesel movement was relatively minimal. At assisted ignition timing, NG concentrated at the rear of the combustion chamber, and diesel concentrated at the front and middle of the combustion chamber. Delaying NGIT and DIT, the mixture became more concentrated due to a shorter mixing time. Moreover, the delayed NGIT and DIT resulted in improvement of the pressure and combustion rate, while for a further delayed DIT the pressure was decreased due to the pressure negative work. Considering the engine power and emission performance, for dual-fuel injection schemes, 340°CA BTDC and 70°CA BTDC were the preferred application schemes for NG and diesel respectively. Their peak combustion pressure (Pmax) increased by 16.34% and 27.38% respectively, but due to the richer mixture, soot value increased by 0.023% and 0.054% and CO (carbon monoxide) value also increased by 0.026% and 0.039% respectively.