Influence of Early Fuel Injection Timings on Premixing and Combustion in a Diesel Engine

Abstract

The influence of fuel injection timing on precombustion mixing of diesel fuel and air, combustion, and emissions at early-injection conditions similar to homogeneous charge compression−ignition (HCCI) engine conditions was investigated experimentally in an automotive-size compression−ignition engine and a constant-volume vessel. The injection timing was controlled by electronic fuel injection equipment. In-cylinder pressure measurements, engine-out emission measurements, and imaging of the spray development were used to analyze the ignition delay period and fuel distribution. The ignition delay period was measured over a wide range of injection timings as well as at various compression ratios and engine speeds. With advancing fuel injection timing, the ignition delay increased and the engine-out nitrogen oxides (NOx) decreased, suggesting that increased premixing time results in a lean mixture and low flame temperature. It was also found that the ignition delay period to decrease NOx emissions to a neglig...