Optimization of combustion mechanisms and injection strategies for jet disturbance enhanced combustion in heavy-duty diesel engines

Improving the fuel-air mixing and combustion rate of heavy-duty diesel engines under high-load conditions is crucial for achieving ultra-high thermal efficiency, which is significant for energy conservation and emission reduction. This study conducted both simulation and experimental research on variable mixing rate conditions utilizing the jet disturbance chamber (JDC) enhanced combustion system. To enhance thermal efficiency, this study investigated the effects of jet flow disturbance under various mixing rate conditions and conducted optimization research on the fuel injection strategy of the JDC. The results indicated that increasing intake pressure in conjunction with injection pressure significantly accelerated the combustion and heat release processes within the JDC, enhancing the sensitivity of the jet flow effect. When the engine operates at a low fuel-air mixing rate boundary characterized by insufficient intake pressure and low rail pressure, the JDC should implement a late injection strategy with a small injection quantity (near CA50) to minimize the low thermal efficiency range of the combustion system. When the engine operates at a high fuel-air mixing rate boundary characterized by high intake pressure and high rail pressure, the JDC should implement an early injection strategy (near CA10). This approach utilizes earlier jet flow disturbance to expand the high thermal efficiency operating range, thereby achieving efficient and clean combustion. At 1200 revolutions per minute and a gross indicated mean effective pressure of 2.3 MPa, the JDC injection timing at 4 degrees ATDC resulted in a gross indicated thermal efficiency of 52.01 %, representing an improvement of 0.67 % compared to the JDC no fuel injection conditions and an improvement of 0.56 % compared to the original engine.