Towards high efficiency of intelligent charge compression ignition (ICCI) engine by optimizing the high-reactivity fuel injection strategies under medium-high loads

In order to improve the efficiency and inhibit the emissions of internal combustion engines, the intelligent charge compression ignition (ICCI) mode based on in-cylinder dual direct injection has been proposed. The key problem to expand the load range of ICCI is to suppress the rapid heat release caused by the combustion of premixed fuel under medium-high loads. In this paper, the double injection strategies of high-reactivity fuel were applicated to control the heat release progress. The results show that by the application of the double injection strategies of diesel under indicated mean effective pressure (IMEP) of 0.8 and 1.0 MPa, the indicated thermal efficiency (ITE) was improved while in-cylinder maximum pressure and the NOx emissions were reduced. Through a detailed analysis of the double injection strategy under IMEP of 1.2 MPa, the second injection timing and fuel ratio played more important roles in reducing in-cylinder maximum pressure and improving ITE. By optimizing the double strategy of diesel, the ITE under IMEP of 1.2 MPa could reach above 50 %. Meanwhile the in-cylinder maximum pressure maintained around 15.5 MPa, and the maximum of pressure rising rate was lower than 1.2 MPa/oCA.