Gasoline compression ignition operation on a multi-cylinder heavy duty diesel engine

Gasoline compression ignition (GCI) is a promising combustion concept with high thermal efficiency, low emissions, and minimal modification of standard engine hardware. With a relaxed constraint on the engine-out NOx emissions, different GCI operating parameters such as exhaust gas recirculation (EGR), injection timing, injection pressure, pilot-main injection interval, and pilot mass were swept to find their optimal calibrations. The entire operating map of a heavy duty diesel engine using GCI combustion with multi-injection strategies was also investigated. Results show that the use of pilot injection is effective in controlling the premixing heat release rate, reducing the combustion noise and emissions, and improving controllability, and allows for advancing combustion timing within the imposed mechanical constrains. With the engine-out NOx calibration of around 4.5 g/kW-h for typical Euro 6 compliant engines, the double injection strategy is applied over the entire operating map in GCI mode, and similar engine performance and emissions can be achieved by GCI combustion compared to conventional diesel combustion (CDC) mode, just using lower injection pressures. The peak brake thermal efficiency (BTE) of 44% over the entire operating map is demonstrated with minimal pumping and friction losses while keeping the peak cylinder pressure (PCP) within 16 MPa.