Combustion characteristics for a hydrogen-fuelled low-pressure-ratio split-cycle engine

Abstract

Investigation of hydrogen-air combustion characteristics for low-pressure-ratio split-cycle engines is performed for the first time. Ignition delay and combustion duration data are presented for low initial pressures below 5 bars and temperatures from ambient level till 550 °C. A simplified constant-volume combustion chamber experiment with glow-plug ignition and timed intake and exhaust valves is constructed in order to simulate the real operation. Ignition delay is found to be inversely proportional to the temperature, and unexpectedly directly proportional with pressure. Equivalence ratio has a weak influence on the ignition delay. Combustion duration exhibits the same behaviour as the ignition delay and represents an average 40% portion of the total combustion delay. Ignition delay results are bounded to the selected glow plug surface temperature range and complements with data in literature. Based on the results, the engine rotational speed would be limited to a maximum of 4500 RPM for an intake duration of 30° at 550 °C and 3.5 bars pre-combustion conditions.