Cycle variations in a hydrogen internal combustion engine

The cycle variation characteristics of a port fuel injection hydrogen internal combustion engine (PFI-HICE) have been extensively investigated. The covariance of indicated mean effective pressure (COV_imep) is the best parameter for evaluating the cycle variations in the PFI-HICE. COV _imep decreases as fuel-air ratio increases from 1000 to 5500 rpm, and engine speed minimally affects COV_imep. The effect of ignition advance angle on COV_imep is determined by fuel-air ratio. The ignition advance angles that correspond to the minimum COV_imep of the PFI-HICE decrease as fuel-air ratio increases. The effect of ignition advance angle on COV_imep diminishes as fuel-air ratio increases. The COV _imep of the PFI-HICE rapidly decreases as throttle increases when the throttle is less than 20%. Injection timing only slightly affects COV _imep under high-speed conditions, and COV_imep increases when hydrogen is injected in intake periods under low-speed conditions. These results indicate that studying COV_imep improves the stability of PFI-HICEs.