Performance Output of Double-Injection Gasoline Compression Ignition (GCI) Combustion in a Common-rail Diesel Engine

The use of low ignition quality fuel in gasoline compression ignition (GCI) engines to form the partially premixed charge during the extended ignition delay period has demonstrated significantly improved engine efficiency and lower smoke/NOx emissions in many previous investigations. The major advantage of GCI combustion over other advanced regimes achieving similar goals such as kinetics-controlled homogenous-charge compression-ignition (HCCI) engines is a close coupling between the fuel injection event and the combustion phasing, a much needed characteristic for practical engine applications. In the present work, the GCI engine tests were emphasised on a direct comparison between single and double injection strategies at fixed engine operating conditions of 1600 rpm and ~910 kPa net indicated mean effective pressure (IMEPn). The tests were carried out in a single-cylinder light-duty diesel engine equipped with a conventional common-rail fuelling system, which is connected with an Eddy Current (EC) dynamometer. It is found that the double injections implementing the early 170°CA bTDC injection and the late near-TDC injection results in overall smoother pressure traces and lower apparent heat release rates than those obtained from the single injection at 30~10°CA bTDC. While keeping the low 3% coefficient of variations of IMEP, these in-cylinder characteristics of the double injection lead to higher net indicated efficiency by 93% and lower indicated specific fuel consumption (ISFC) by 48%, clearly demonstrating the advantages of independently controlling the mixture premixedness using the early first injection and the combustion phasing with the late second injection.