Effects of Surrounding Gas Condition, Fuel Injection Condition and Fuel Properties on Ignition Delay in Diesel Engines.

Abstract

Ignition delay of diesel fuel sprays is investigated experimentally using a rapid compression expansion machine at operating conditions which are common in modern diesel engines. A comparison of experimental result with published data shows that higher injection pressure and smaller orifice diameter can shorten ignition delay respectively. In an attempt to make the physical ignition delay as short as possible, an experiment is conducted using injection nozzles with tiny orifices processed by a laser drilling. The result shows that ignition delay becomes short as the orifice diameter decreases, but it remains unchanged if the orifice diameter is smaller than 0.05 mm. It is also worth noting that there exists a temperature range around 790 K in which ignition delay remains almost constant being independent of the temperature. This trend is similar to that observed in shock tube studies concerning homogeneous mixture autoignition, implying that the ignition delay obtained with those nozzles is governed mainly by chemical ignition delay.