The Impact of Intake Duct Water Injection on the Knock Behavior of Hydrogen Internal Combustion Engines

To investigate the effects of water injection technology on knock suppression and power improvement in high-speed， high-load hydrogen internal combustion engines， simulation study was conducted on the influence of intake manifold water injection parameters on hydrogen engine combustion and knock， based on a three-dimensional model of a 1.5 L turbocharged direct-injection hydrogen engine. The research results indicated that when the water injection amount increased from 14 mg to 44 mg， the peak cylinder pressure decreased from 14.8 MPa to 7.5 MPa， and the peak heat release rate dropped from 232 J/（°） to 61 J/（°）. When the water injection amount was 34 mg， the knock intensity was 0.08 MPa， at which point there was no knock occurring in the cylinder. After the water injection amount increased to 44 mg， although the knock intensity decreased to 0.06 MPa， the peak cylinder pressure was only 7.5 MPa， and combustion difficulty negatively affected the performance of the hydrogen engine. The earlier the water injection timing， the more uniform the distribution of water vapor in the cylinder. However， if the injection timing is too early， the liquid film mass in the intake manifold increases. If it is too late， the water in the intake manifold does not have enough time to enter the cylinder. 300° before top dead center is the optimal water injection timing. Increasing the air-fuel mixture concentration can enhance the engine’s power output. When the excess air ratio decreases to 1.53， an indicated power of 141 kW can be achieved under conditions with no knock.