微自由活塞动力装置中混合气泄漏对燃烧过程的影响

Influence of Gas Leakage on Combustion Process in Micro Free-Piston Power Device

利用数值模拟计算软件,结合甲烷详细化学反应动力学机理及动网格技术,对微自由活塞动力装置中自由活塞与微燃烧壁面之间不同间隙条件下压缩着火过程进行模拟计算。计算结果表明:相同条件下,随着间隙的增大,单次压缩着火周期增长,工作频率变小,但着火时刻点基本不变;间隙大小相同的条件下,活塞初速度越大,压缩比越大,动力输出性能越差。同时,对临界压缩比随着间隙大小的变化规律进行计算,分析得出在无泄漏条件下临界压缩比值为48,微动力装置压缩比大于临界压缩比时,混合气体才能压缩着火,且随着泄漏间隙的增大,临界压缩比值也随之增大。

In view of a gap between the free-piston and the micro combustor wall in a micro free-piston power device, the influence of leakage gap on the process of homogeneous charge compression ignition （HCCI）, was investigated by using a numerical simulation software together with a detailed chemical kinetic model of CH4 and dynamic network tochnology under different leakage gap size. The results indicate that under the same conditions, increased leakage gap will lead to increased, single-compression period, and decreased working frequency, but basicly unchanged ignition time. Under the same conditions of leakage gap size, the greater the initial piston speed is, the higher the compression ratio is, while the worse the power output performance is. Meanwhile the relationship between critical compression ratio and leakage gap was calculated, The analytic results show that when the critical compression ratio is 48 without leakage, and the compression ratio of the micro power device is greater than the critical value, the mixture can be compressed to ignite and the critical compression ratio will continue to increase with the increase in leakage gap.