纯氧氛围下正庚烷均质压燃燃烧特性

Homogeneous Charge Compression Ignition Combustion Characteristics of n-Heptane in Pure Oxygen Atmosphere

摘要:

基于一台双缸柴油机，结合自行设计开发的纯氧进气系统进行试验，研究了不同进气氧体积分数对正庚烷均质压燃燃烧过程及稳定性的影响。试验结果表明，随着混合气中氧体积分数降低，二氧化碳体积分数增加，缸内平均比热容不断增大，使得缸内最高燃烧温度降低，其对应的峰值相位推迟，燃烧始点推迟，放热率峰值下降，热效率降低；同时发现随着二氧化碳体积分数的增加，缸内温度会随之降低，使得燃烧循环不稳定性增强。以上现象均表明较高的二氧化碳体积分数能够有效抑制纯氧氛围下正庚烷均质压燃。此外，试验发现了纯氧氛围下正庚烷均质压燃负温度系数区间持续时间大幅缩短现象。

Abstract:

Based on a two-cylinder diesel engine and a self-designed pure oxygen intake system，the effect of different intake oxygen volume fractions on the combustion process and stability of homogeneous charge compression ignition of n-heptane were investigated.The experimental results show that， with the decreasing volume fraction of oxygen and increasing volume fraction of carbon dioxide in the mixture， the average specific heat capacity in the cylinder is increased， which leads to the maximum combustion temperature in the cylinder is decreased， the corresponding peak phase is delayed， the combustion start point is delayed， the peak heat release rate is decreased， and the thermal efficiency is reduced.Meanwhile， it was found that with the increasing of carbon dioxide volume fraction， the temperature in the cylinder decreased， which led to the strengthening of the combustion cycle instability. The above phenomena indicate that the higher volume fraction of carbon dioxide can effectively inhibit the homogeneous charge compression ignition of n-heptane under pure oxygen atmosphere.Moreover， the interval duration of negative temperature coefficient of n-heptane homogeneous charge compression ignition is significantly shortened in pure oxygen atmosphere.