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为满足严格的排放法规和燃油经济性要求,乘用车柴油机呈现出低压缩比的趋势。较低的压缩比在降低排放方面具有优势。但是,较高的压缩比对获得更高的理论热效率有益。米勒循环的进气门延迟关闭策略可使压缩比低于膨胀比,这样可以降低压缩行程终点的温度。将米勒循环应用于轻型商用车柴油机,并对其降低排放和燃油耗的效果进行了验证。通过应用米勒循环,降低了日本排放测试循环JE05运行工况下的发动机燃油耗和碳烟排放,并且对氮氧化物排放没有产生负面影响。
To meet the stringent emission regulations and fuel economy requirements, passenger car diesel engines show a trend of low compression ratio. Lower compression ratio has an advantage in reducing emissions. However, a higher compression ratio is beneficial for achieving higher theoretical thermal efficiency. Miller cycle intake valve delay closing strategy allows the compression ratio is lower than the expansion ratio, thus reducing the compression stroke end temperature. The Miller cycle is applied to light commercial vehicle diesel engines and the effect of reducing emissions and fuel consumption is verified. By applying the Miller cycle, the engine fuel consumption and soot emissions under the Japanese emission test cycle JE05 operating conditions are reduced and have no negative impact on NOx emissions.