| 柴油机侧卷流和分卷流燃烧系统性能测试与分析 |
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| 引用本文： | 张智,李向荣,刘洋,刘丽芳,刘栋,常江.柴油机侧卷流和分卷流燃烧系统性能测试与分析[J].农业工程学报,2022,38(7):20-28. |
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| 作者姓名： | 张智 李向荣 刘洋 刘丽芳 刘栋 常江 |
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| 作者单位： | 1. 北京理工大学机械与车辆学院，北京 100081;;2. 63963部队，北京 100072; |
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| 基金项目： | 国家自然科学基金资助项目（51976011） |
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| 摘 要： | 侧卷流燃烧系统（Lateral Swirl Combustion System，LSCS）和分卷流燃烧系统（Separated Swirl Combustion System，SSCS）均是利用特殊设计的燃烧室壁面导流结构来引导缸内喷雾形成卷流运动，达到改善油气混合质量的目的。两种燃烧系统在缸内的布油策略不同，为对比研究两种燃烧系统的性能，该研究利用模拟增压单缸柴油机进行了侧卷流燃烧系统和分卷流燃烧系统在不同负荷和过量空气系数下的燃烧性能试验；采用AVL Fire软件探究了两种燃烧系统改善油气混合过程的机理。试验结果表明：不同工况下，侧卷流燃烧系统的燃油消耗率和碳烟排放均低于分卷流燃烧系统；相比于分卷流燃烧系统，侧卷流燃烧系统在不同负荷下的燃油消耗率降低了2.4～7.8 g/(kW·h)，碳烟排放降低了2.7～3.9 FSN（Filter Smoke Number，滤纸式烟度单位）；在不同过量空气系数下的燃油消耗率降低了3.2～9.8 g/(kW·h)，碳烟排放降低了2.3～3.8 FSN，燃油消耗率最大降幅为4.3%，碳烟排放最大降幅为87.0%。仿真结果表明：侧卷流燃烧系统中，油束在分流造型的导流作用下形成侧向卷流运动，相邻两束卷流在流出分流造型时产生壁射流干涉作用，进一步提高了燃烧室内的空气利用率；而分卷流燃烧系统在活塞下行时，油束触壁位置的改变导致了燃油聚集现象，不利于油气混合过程。相较于分卷流燃烧系统，侧卷流燃烧系统的空气卷吸量增加了9.3%，在当量比为2～4区间内的燃油质量比例较小，在当量比1～2区间内的燃油质量比例较大，表明侧卷流燃烧系统的油气混合均匀性较好。因此，侧卷流燃烧系统对油气混合过程的改善作用更为显著，明显提升了直喷式柴油机的燃烧性能，减少碳烟生成。研究结果可为直喷式柴油机燃烧室结构设计和优化提供技术参考。
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| 关 键 词： | 燃烧 排放 直喷式柴油机 侧卷流 分卷流 燃烧系统 |
| 收稿时间： | 2021/11/11 0:00:00 |
| 修稿时间： | 2022/3/22 0:00:00 |
Performance test and analysis of lateral swirl combustion system and separated swirl combustion system in diesel engines |
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| Zhang Zhi,Li Xiangrong,Liu Yang,Liu Lifang,Liu Dong,Chang Jiang.Performance test and analysis of lateral swirl combustion system and separated swirl combustion system in diesel engines[J].Transactions of the Chinese Society of Agricultural Engineering,2022,38(7):20-28. |
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| Authors: | Zhang Zhi Li Xiangrong Liu Yang Liu Lifang Liu Dong Chang Jiang |
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| Institution: | 1. School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;;2. Unit 63963, Beijing 100072, China; |
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| Abstract: | A diesel engine has been widely used in ground transportation, agricultural machinery, and sea shipments, due mainly to its excellent reliability and high thermal efficiency. However, the fuel emission and consumption of diesel engines have posed a great threat to the ecological environment in recent years. Therefore, it is very necessary to improve the combustion and emission performance of diesel engines, further to meet the specific requirement of national environmental regulations. Diffusion combustion can generally dominate the combustion process in the direct injection diesel engine. The mixing quality of fuel and air can be expected to serve as the most effective means for the higher performance of diffusion combustion. Different techniques have also emerged to optimize the combustion quality of the fuel/air mixing process in modern diesel engines. For instance, the special geometry structure of the combustion chamber has been adopted to utilize the momentum of the high-pressure fuel jet in the wall-flow-guided combustion system, where the diffusion can be guided in the chamber by the effect of the spray jet hitting the wall. As such, the air utilization rate can be improved for the high combustion and emission performance of a direct injection diesel engine. Both lateral swirl combustion system (LSCS) and separated swirl combustion system (SSCS) have been specially designed for the wall diversion structure in the combustion chamber, where the spray in the cylinder can be guided to form a swirl motion for the high quality of fuel/air mixing process. Nevertheless, the two combustion systems behave in different in-cylinder fuel spray strategies. In this study, a single-cylinder diesel engine was selected to verify the combustion performance of the LSCS and SSCS under different loads and excess air coefficients. AVL Fire software was used to explore the fuel/air mixing mechanism of the combustion system. The test results show that the fuel consumption rate, soot emission, and combustion duration of LSCS under various loads were reduced by 2.4-7.8 g/(kW·h), 2.7-3.9 FSN, and 5.6-10.7 °CA, respectively, compared with the SSCS. Under different excess air coefficients, the fuel consumption rate, soot emission, and duration of combustion were reduced by 3.2-9.8 g/(kW·h), 2.3-3.8 FSN, and 7.9-10.0 °CA, respectively. The maximum drop of LSCS in the fuel consumption and soot emission were 4.3%, and 87.0%, respectively. The simulation results show that the spray jet impinged the convex edge in the LSCS, leading to the wall jets scrolling to form two lateral swirls. The two adjacent spray jets produced the wall jet interference, when flowing out of the convex edge, further improving the air utilization rate. By contrast, there was the fuel aggregation, as the position of the spray jet touched the wall, particularly when the piston was moving down in the SSCS, which was not conducive to the fuel/air mixing process. That is why the air entrainment quantity of the LSCS increased by 9.3%, compared with the SSCS. There was a smaller fuel mass ratio in the interval of equivalent ratio 2-4, whereas, the larger in the interval of equivalent ratio 1-2, indicating the better uniform fuel/air mixing of the LSCS. Therefore, the LSCS can be widely expected to outstandingly improve the fuel/air mixing process, and the combustion performance of the direct injection diesel engine with less soot generation. The finding can provide a technical reference for the structural design and optimization of the combustion chamber in the direct injection diesel engine. |
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| Keywords: | combustion emission direct injection diesel engine lateral swirl separated swirl combustion system |
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