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对一台4缸四冲程直喷式增压柴油机进行了在吸气行程初期从进气道喷水以降低NOX生成量的试验研究，并采用2区域模型法进行计算分析，对比了试验与计算结果。研究表明，在进气绝对湿度换算值为0．035kg/kg空气时，约可降低NOX浓度50％，而且上述效果与柴油机工况条件及喷射定时无关，只取决于进气的绝对湿度。NOX生成量减少的主要原因是燃烧气体中所含水分引起比热增大而导致燃气温度降低。
A 4-cylinder four-stroke direct-injection turbocharged diesel engine was used to reduce NOX production by injecting water into the intake air duct at the initial stage of inhalation stroke. The 2-zone model method was used to calculate and analyze the results. Compared with the experiment and calculation result. The results show that when the absolute value of inlet air humidity is 0.035kg / kg air, the NOx concentration can be reduced by about 50%, and the above effect is independent of diesel engine operating conditions and injection timing, and only depends on the absolute humidity of intake air. The main reason for the reduction of NOX production is that the water contained in the combustion gas causes the specific heat to increase, resulting in a decrease in the temperature of the gas.