Abstract
The objective of this study is to find strategies for extending the load range of low-temperature combustion (LTC) while improving thermal efficiency and reducing combustion noise and exhaust emissions. Experiments were performed using a single-cylinder direct-injection diesel engine equipped with a common-rail injection system and a cooled EGR system. First, experiments were carried out with single-stage injection. The results indicated a notable improvement of NO_x and smoke emissions by selecting lower EGR rates and later injection timing according to the increase in injection quantity. However, the problems of high pressure rise rates and unburned species emissions developed. To solve these problems, two-stage injection was applied. Additional experiments started with the injection and EGR conditions based on the results of single-stage injection tests, and modifications were made to mitigate the increased emissions and decreased thermal efficiency. Through the process of optimizing the conditions, a control strategy of two-stage injection was proposed.
