Autoignition and Emission Characteristics of Gaseous Fuel Direct Injection Compression Ignition Combustion

An experimental investigation of the autoignition and emission characteristics of transient turbulent gaseous fuel jets in heated and compressed air was conducted in a shock tube facility. Experiments were performed at an initial pressure of 30 bar with initial oxidizer temperatures ranging from 1200 to 1400 K, injection pressures ranging from 60 to 150 bar, and injection durations ranging from 1.0 to 2.5 ms. Methane and 90.0% methane/10.0% ethane blend were used as fuel.

Under the operating conditions studied, increasing temperature resulted in a significant decrease in autoignition delay time. Increasing the injection pressure decreased ignition delay as well. The downstream location of the ignition kernel relative to the jet penetration distance was found to be in the range, 0.4<Z_k/Z_t<0.8, while its location relative to the equivalent orifice diameter was in the range, 20<Z_k*<60. NOx emissions were found to increase significantly with increasing temperature and injection pressure. The addition of 10% ethane to the methane fuel increased Z_k/Z_t, Z_k* and NOx emissions significantly, while the ignition delay was relatively unchanged.