The Miller cycle has been proven to be an effective way to improve the thermal efficiency for gasoline engines. However, it may show insufficient power performance at certain loads. In this study, the objective is to exploit the advantages of the Miller-cycle engines over the original Otto-cycle engines. Therefore, a new camshaft profile with early intake valve closure was devised, and two various pistons were redesigned to obtain higher compression ratio 11.2 and 12.1, based on the original engine with compression ratio 10. Then, a detailed comparative investigation of the effects of Miller cycle combined with higher compression ratio on the performance and emission of a turbocharged gasoline direct injection engine has been experimentally carried out based on the engine bench at full and partial loads, compared to the original engine. The results show that, at full load, for a turbocharged gasoline direct injection engine utilizing the Miller cycle, partial maximum power is compromised about 1.5% while fuel consumption shows a strong correlation with engine speed. At partial load, since the Miller effect can well reduce the pumping mean effective pressure, thus improves the fuel economy effectively. In addition, the suppression of the in-cylinder combustion temperature induced by the lower effective compression ratio contributes to the reduction of nitrogen oxide emission greatly. However, the total hydrocarbon emission increases slightly. Therefore, a combination of the Miller cycle and highly boosted turbocharger shows great potential in further improvement of fuel economy and anti-knock performance for downsized gasoline direct injection engines.

米勒循环已被证明是提高汽油发动机热效率的有效方法。但是，在某些负载下，电源性能可能不足。在这项研究中，目标是利用Miller循环发动机优于原始的Otto循环发动机的优势。因此，设计了一种具有提前进气门关闭功能的新凸轮轴轮廓，并基于原始压缩比为10的发动机，重新设计了两个不同的活塞以获得更高的压缩比11.2和12.1。然后，对米勒的效果进行了详细的比较研究与原始发动机相比，已经在全负荷和部分负荷条件下基于发动机台架在实验上进行了循环，并结合了更高的压缩比，从而对涡轮增压汽油直喷发动机的性能和排放进行了试验。结果表明，在满负荷情况下，对于使用米勒循环的涡轮增压汽油直喷发动机，部分最大功率降低了约1.5％，而燃油消耗与发动机转速显示出很强的相关性。在部分负荷下，由于米勒效应可以很好地降低泵送平均有效压力，从而有效地提高了燃油经济性。另外，由于较低的有效压缩比而引起的缸内燃烧温度的抑制大大有助于减少氮氧化物的排放。但是，总碳氢化合物排放量略有增加。因此，米勒循环和高增压涡轮增压器的组合显示出进一步改善小型汽油直喷发动机的燃油经济性和抗爆性能的巨大潜力。对于利用米勒循环的涡轮增压汽油直喷发动机，部分最大功率降低了约1.5％，而燃油消耗却与发动机转速密切相关。在部分负荷下，由于米勒效应可以很好地降低泵送平均有效压力，因此可以有效地提高燃油经济性。另外，由于较低的有效压缩比而引起的缸内燃烧温度的抑制大大有助于减少氮氧化物的排放。但是，总碳氢化合物排放量略有增加。因此，米勒循环和高增压涡轮增压器的组合显示出进一步改善小型汽油直喷发动机的燃油经济性和抗爆性能的巨大潜力。对于利用米勒循环的涡轮增压汽油直喷发动机，部分最大功率降低了约1.5％，而燃油消耗却与发动机转速密切相关。在部分负荷下，由于米勒效应可以很好地降低泵送平均有效压力，因此可以有效地提高燃油经济性。另外，由于较低的有效压缩比而引起的缸内燃烧温度的抑制极大地有助于减少氮氧化物的排放。但是，总碳氢化合物排放量略有增加。因此，米勒循环和高增压涡轮增压器的组合显示出进一步改善小型汽油直喷发动机的燃油经济性和抗爆性能的巨大潜力。