燃气发动机瞬态工况下NO_x排放特征

Characteristics of NO_x emission from gas engine under transient operating conditions

NO_x排放控制是发展燃气汽车的核心问题.为获得增压中冷燃气发动机瞬态工况NO_x的排放特征,实验选取了6MK375N-50增压中冷燃气发动机,研究了不同转速、转矩、进气流量、进气温度及湿度对NO_x排放的影响.试验结果表明NO_x的排放随着转速的增加先升高后减缓,转速为1400 r·min-1时NO_x排放最高,转矩的增加也会使NO_x排放增加,随着进气流量的增加,NO_x排放量先增加后稳定,进气流量为180 kg·h^(-1)时NO_x排放最高,进气温度对NO_x排放也有直接影响,进气温度为31℃时NO_x排放最高,随着进气湿度的增加,NO_x排放水平降低,对试验结果的双因素方差分析得到,各影响因素对NO_x的排放影响均非常显著.对1400 r·min-1下各个工况对应NO_x进行拟合,变化规律符合公式y=a-b×ln(x+c).

NOx emission control is the core issue of development of gas vehicles. To obtain the characteristics of NOx emission from gas engine under transient operating conditions,we selected the 6MK375N-50 turbocharged inter-cooled gas engine and investigated the effects of rotating speed,torque,inlet flow rate,inlet flow temperature,and inlet flow humidity on NOx emissions. The results showed that NOx emissions increased first and leveled off with increasing rotational speed. NOx emission was the most significant under the rotating speed of 1400 r·min^-1. The increase in torque results in the increase of NOx emission. NOx emission increased steadily in the beginning and then leveled off along the increase of inlet flow rate.The highest NOx emission was obtained under the inlet flow rate of 180 kg·h^-1. Meanwhile,the inlet temperature has a direct effect on NOx emission,with the maximum NOx emission achieved at inlet temperature of 31 ℃. NOx emission decreased with the increase of inlet flow humidity. All the above-mentioned factors have significant influence on the NOx emission by calculating the test results based on two-factor variance analysis. By fitting the abovementioned parameters with NOx emission,the empirical equation under 1400 r·min^-1was derived in accordance with y = a- b × ln（ x ＋ c）.