Delay of ignition in early direct-injected PCCI engine combustion using fuel-evaporative cooling and cooled EGR

摘要

In early direct-injected PCCI combustion, one of the several approaches to ideal PCCI, the early injected fuel forms a nearly homogeneous air-fuel charge, but most or all of the mixture ignites and burns during the compression stroke, which limits its application to light load operation range with lower-than-expected thermal efficiency. In the present research a unique split fuel injection technique was developed to delay the combustion of the entire fuel for mixing with air before burning. Evaporative cooling effects provided by the fuel in the second injection at precise timing held the self-ignition of the early injected fuel, and thus allowed the entire fuel to burn in PCCI mode at a favorable time in a cycle, namely a little after the top center. The single cylinder test engine run this way demonstrated the diesel-like efficiency along with an-order-of-magnitude lower NOx emissions than in conventional diesel combustion.