针对一款2.0 L自然吸气缸内直喷汽油机，通过调整配气相位，试验研究了有效压缩比和外部EGR对发动机燃油消耗的影响。研究结果表明：有效压缩比对燃油消耗率影响显著，降低有效压缩比，能够抑制爆震，改善燃油消耗。试验所选工况范围内，低有效压缩比相对高有效压缩比方案燃油消耗率降低2.7%，热效率提升1个百分点，但低有效压缩比情况下，由于进气持续时间过长，活塞达到下止点后缸内工质的推出量过大，对整体性能的影响较为显著。通过引入外部EGR可改善燃烧过程，燃烧重心有所提前，EGR率达到21%时，燃油消耗率降低约6.8%。EGR率过大会导致燃烧放热过程变缓，滞燃期和燃烧持续期显著延长，同时过高的EGR温度会加剧爆震，导致燃油消耗率恶化。

Aiming at a 2.0 L naturally-aspirated in-cylinder direct injection gasoline engine, the influence of effective compression ratio and external EGR on engine fuel consumption was tested by adjusting the valve phase. The results show that the effective compression ratio has a significant impact on fuel consumption and its reduction can suppress knocking and improve fuel consumption. Within the tested working conditions, the low effective compression ratio can reduce fuel consumption by 2.7% and increase the thermal efficiency by 1%. However, too long intake duration leads to the release of more working substance after BDC, which affects the whole performance obviously. External EGR can improve the combustion process and advance the center of combustion. The fuel consumption rate reduces by about 6.8% when the EGR rate reaches 21%. However, the larger EGR rate will slow down the combustion process and significantly prolong the ignition delay and combustion duration. The too high temperature of EGR will also aggravate knocking and cause deterioration of fuel consumption.