Effect of ignition timing on operating characteristics of a micro hydrogen reciprocating engine

Abstract

Reliable hydrogen combustion aero engines will be needed for future aircrafts including UAVs (Unmanned Aerial Vehicles). In our previous study, we established how to supply a lubricant into a micro reciprocating engine (FG-11, originally a 4-stroke gasoline engine) and succeeded in its continuous operations with hydrogen. Delayed ignition timing was needed to prevent the engine stalls at higher hydrogen flow rates. In this study, the engine was operated with various ignition timings with hydrogen and break power and thermal efficiency were measured. Also, the pressure in the cylinder was measured to clear its combustion process. When the ignition timings are far before TDC, the break powers are low, and it will cause the engine stall because the compression work increased. To maximize the power in a micro reciprocation hydrogen engine, it is important to spark in the narrow range near the TDC due to the short ignition delay and high burning velocity of hydrogen.