The Air Assisted Direct Injection ELEVATE Automotive Engine Combustion System

The purpose of the ELEVATE (European Low Emission V4 Automotive Two-stroke Engine) industrial research project is to develop a small, compact, light weight, high torque and highly efficient clean gasoline 2-stroke engine of 120 kW which could industrially replace the relatively big existing automotive spark ignition or diesel 4-stroke engine used in the top of the mid size or in the large size vehicles, including the minivan vehicles used for multi people and family transportation. This new gasoline direct injection engine concept is based on the combined implementation on a 4-stroke bottom end of several 2-stroke engine innovative technologies such as the IAPAC compressed air assisted direct fuel injection, the CAI (Controlled Auto-Ignition) combustion process, the D2SC (Dual Delivery Screw SuperCharger) for both low pressure engine scavenging and higher pressure IAPAC air assisted DI and the ETV (Exhaust charge Trapping Valve). Its design process extensively supported by 1D and 3D CFD simulation studies has been presented in a previous paper. Such simulations have been useful to give preliminary V4 ELEVATE engine design specifications corresponding to the expected performance targets. Based on these specifications, a representative single cylinder research and development engine has been designed and manufactured. Detailed results of this experimental engine are presented in this new paper. They illustrate how the ELEVATE engine concept is based on a unique and innovative combustion system combining air assisted direct injection of gasoline with controlled auto ignition combustion. The effect of the design specifications of the main innovative engine features on the auto-ignition characteristics is analyzed in details. This analysis shows how the part load auto-ignition combustion process parameters can be controlled for best benefits in terms of low NOx emissions and high fuel economy. Finally, the results obtained give precious indications on the ways of future development testing and calibration of the ELEVATE V4 engine demonstrator for its in-vehicle assessment.