臭氧对天然气HCCI发动机燃烧影响的数值研究

A Numerical Study of the Effect of Ozone Additive on the Nature Gas Fueled HCCI Engine

HCCI（均质充量压燃）发动机的燃烧过程主要是受到燃料本身的化学反应动力学控制，因此改变燃料的化学性质能够有效地控制HCCI发动机的燃烧过程。由于天然气不易压燃的化学特性，所以天然气HCCI发动机低负荷运行时，会因燃烧反应速率过慢而出现火焰温度低、燃烧不充分甚至“失火”等现象。本研究中，通过耦合详细介绍天然气和臭氧（O3）的燃烧反应机理，并结合HCCI单区模型，模拟计算了进气道添加O3对天然气HCCI发动机燃烧相位的影响并进行化学反应路径分析。通过模拟计算与试验结果对比得出：进气道中添加10-40ppm的O3可以改变天然气的燃烧反应路径，实现对天然气HCCI发动机燃烧相位的控制。低浓度的O3能有效地改变天然气低温燃烧时的燃烧相位并提高缸内燃烧压力，拓宽天然气HCCI发动机低负荷工况范围。

The combustion progress of HCCI （Homogeneous Charge Compression Ignition）en- gines is mainly governed by chemical kinetics of the fuels. Therefore, it is desirable to adjust the combustion progress by changing the chemical property of the fuels. As nature gas cannot be ignited easily by compression alone when HCCI engines run in low load condition, the low in-cylinder tem- perature leads to misfire. In this work, through the combination of the detail chemical kinetic mecha- nism of nature gaswith that of ozone in a single-zone model, the impact of O3 on the combustion phase of HCCI engines were investigated, and the chemical reaction paths were analyzed. Comparing the calculated results with the experimental results, it reveals that chemical reaction paths of the na- ture gas can be changed by adding 10 to 40 ppm ofO3into the intake port, to control the combustion phase of HCCI engines. Low concentration of O3can effectively advance the combustion phase of na- ture gas and improve the in-cylinder combustion pressure, which can extend the operational region of HCCI engines in low load conditions.