| 陈淼钰,龚航,黄粉莲,等.基于喷孔布置及喷射参数协调控制的双直喷发动机燃烧及碳烟排放特性研究[J].内燃机工程,2023,44(2):17-25. |
| 基于喷孔布置及喷射参数协调控制的双直喷发动机燃烧及碳烟排放特性研究 |
| Research on Combustion and Soot Emission Characteristics of A Dual Direct Injection Engine Based on the Combined Control of Nozzle Arrangements and Injection Parameters |
| DOI：10.13949/j.cnki.nrjgc.2023.02.003 |
| 关键词:高压直喷 天然气发动机 射流角度 喷射持续期 碳烟排放 |
| Key Words:high pressure direct injection natural gas engine jet angle injection duration soot emission |
| 基金项目:国家自然科学基金项目（51866004）；昆明理工大学学生课外学术科技创新基金项目（2022ZK065）；云南省教育厅科学研究基金项目（2022Y157） |
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| 摘要:通过建立三维计算流体力学（computational fluid dynamic， CFD）柴油/天然气双直喷模型耦合多组分混合物简化化学动力学机理及现象学碳烟模型，模拟研究了天然气射流中心轴线与水平方向夹角α、天然气喷射持续期（natural gas injection duration， NID）的协调作用对柴油微引高压直喷天然气发动机燃烧过程及碳烟生成、氧化过程的影响。结果表明：缩短NID可提高扩散火焰的传播速度，增加燃烧区域的化学反应速率，且最高燃烧压力、峰值放热率、最大压力升高率（maximum pressure rise rate， MPRR）、指示热效率（indicated thermal efficiency， ITE）升高；随NID缩短，A4、C2H2消耗反应速率增加，OH生成峰值增加，碳烟生成降低而氧化增强。增大α促进了大尺度涡旋结构的生成，降低了进入挤气区域的燃料比例，同时利于ITE的改善；较短的NID下，增大α后最高燃烧压力、峰值放热率提升明显；α增大至20°可显著降低A4、C2H2生成峰值，抑制碳烟成核及表面生长反应，降低碳烟生成。综合考虑最高燃烧压力、ITE、MPRR及碳烟排放，确定两个优化方案分别为：α=15° & NID=16.5°及α=20° & NID=21.5°。 |
| Abstract:The analysis of combustion process and soot formation and oxidation processes of a pilot diesel ignited high pressure direct injection engine with the combined effects of the angle α between the central axis of the natural gas jet and the horizontal direction， and natural gas injection duration（NID）， were performed by establishing a three-dimensional computational fluid dynamic（CFD） diesel/natural gas dual direct injection model coupled with a simplified chemical kinetic mechanism of multi-component mixture and a phenomenological soot model. The results show that shortening the NID can increase the diffusion flame propagation speed and the chemical reaction rate in the combustion area. Meanwhile， the burst pressure， peak value of heat release rate， maximum pressure rise rate（MPRR）， indicated thermal efficiency（ITE） increase with the increasing of NID. As NID shortens， the reaction rates of A4 and C2H2 consumption increase， the peak value of OH increases， soot production decreases and oxidation effect is enhanced. Increasing α promotes the formation of large-scale vortex structure， reduces the proportion of fuel entering the squish region， and facilitates the improvement of ITE. At a shorter NID， the burst pressure and peak value of heat release rate increase significantly with the increase of α. The peak values of A4 and C2H2 can be significantly reduced， soot nucleation and surface growth reactions can be inhibited， and soot production can be reduced when α is increased to 20°. Considering the combined effects of the burst pressure， MPRR， ITE and soot emissions， the optimized cases are α=15° & NID=16.5° and α=20° & NID=21.5°. |
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