Experimental investigation the effects of Miller cycle coupled with asynchronous intake valves on cycle-to-cycle variations and performance of the SI engine

A novelty of the Miller cycle with the asynchronous intake valve (AIVMC) was proposed and used in the test SI engine. In addition, the effects of the AIVMC on the combustion cycle-to-cycle variations and performance of the test SI engine were analyzed, and then compared to the experimental results of the Otto cycle (OC). The results indicated that the transient in-cylinder pressure distributions were discrete, and the peak combustion pressure distribution gradually dispersed with decreasing the intake valve spacing angle. The coefficient of variation of the indicated mean effective pressure (COVIMEP) of the test SI engine equipped with AIVMC were respectively 1.45% and 2.79% with using the spacing 90 degrees CA and 50 degrees CA under the low load, while the COVIMEP of the test SI engine equipped with AIVMC were respectively 0.79% and 3.45% with using the spacing 90 degrees CA and 50 degrees CA under the medium load. The application of AIVMC in the test SI engine effectively reduced the pumping mean effective pressure (PMEP) compared with OC. Under the operating condition of 2600 rpm and 8 bar, the EER of the test SI engine equipped with AIVMC (spacing 90 degrees CA) was 13.0, which respectively increased 26.2% and 36.8% compared to the AIVMC (spacing 50 degrees CA) and OC.