Investigation on the Influence of Intake Port Flow Pattern on the Performance of a NG Engine

The intake port was re-designed for a natural gas(NG) engine in order to change the swirl flow into the tumble flow. A performance test was then implemented on the NG engine bench which matched the original and the new intake port respectively. The result shows that，compared with the original intake port under the same operating conditions and control parameters，the new port has lower pre-turbine pressure and temperature，and the brake specific fuel consumption is decreased by 1—2 g/(kW·h). It also has higher cylinder pressure and lower cyclic variation. Both the start of combustion phase angle(AI 05) and the combustion center phase angle(AI 50) are advanced by 2°—3° CA，but the combustion duration is prolonged by 5°—7° CA. Further investigation founds that the reason for the advantage of the new intake port is that the spark plug can be better scavenging. However，the new intake port cannot accelerate combustion and therefore induces a more seriously knocking event，which is ascribed to its shorter ignition delay and weaker designed tumble strength. In addition，the characteristic of better combustion stability makes the new intake port to have higher exhaust gas recirculation(EGR) tolerance，which is beneficial for lower exhaust temperature. © 2023 Chinese Society for Internal Combustion Engines. All rights reserved.