Synergistic Regulation of Common Rail Pressure and Injection Angle on Heavy‐Duty Diesel Engine Performance

This study investigates a commercial heavy‐duty diesel engine equipped with a DOC + DPF + SCR + ASC aftertreatment system, which already meets China VI emission standards. Through coordinated optimization experiments of injection timing and common‐rail pressure under typical operating conditions, the comprehensive effects of injection parameters on the power performance, fuel economy, emission characteristics, and vibration levels of the engine are systematically studied. The results indicate that increasing common rail pressure enhances the power performance of heavy‐duty diesel engines: when the injection timing is maintained constant at 5°CA before top dead center (BTDC) and the rail pressure is gradually increased from 100 MPa to 130 MPa in 10 MPa increments, the engine's torque and power increase continuously with rising rail pressure, specifically increasing from 1330.5 N·m and 166.8 kW (at 100 MPa) to 1368.1 N·m and 177.0 kW (at 130 MPa), respectively. However, the influence of injection advance angle on power performance does not exhibit a monotonic positive correlation; instead, an optimal injection advance angle exists. Regarding fuel economy, increasing common rail pressure effectively reduces the engine's brake specific fuel consumption (BSFC), while the injection advance angle exhibits an optimal calibration value for its impact on BSFC, and the effect of increasing common rail pressure on BSFC varies under different injection advance angles. For emissions, an increase in common‐rail pressure resulted in a reduction in engine‐out CO and THC emissions, whereas NO x and NH 3 emissions were elevated. Among these test conditions, condition 6, with an injection timing of 5°CA BTDC and a rail pressure of 130 MPa, exhibited the best emission performance, with CO, THC, and NO x emissions of 127.5 ppm, 56.9 ppm, and 1678.3 ppm, respectively. A moderate increase in injection advance angle lowers CO and THC emissions, whereas an excessive increase results in elevated CO and THC emissions. Furthermore, the common rail pressure and injection timing of heavy‐duty diesel engines collectively influence the engine's combustion process, thereby affecting the engine's cyclic operation and ultimately modifying the vibration level of the cylinder block.