Impact of Compression Ratio on Combustion and Emission Characteristics of Hydrogen Fuel for Turboprop Aircraft Engines Operating at Various Excess Air Coefficients

Abstract

One of the ways to mitigate carbon emission from air transportation can be through the integration of hydrogen internal combustion engines. This paper examines the performance of TurbAero TA200TP direct-injection hydrogen fueled engine, its emissions, and its combustion characteristics when the engine has compression ratio of 9 and 11, 13 and Excess Air Ratio ranges from 1 to 5 under lean-burn conditions. The volumetric efficiency, the thermal efficiency, the NOx emissions, and the combustion stability were all studied by a validated one-dimensional GT-POWER model calibrated with 0.6 bar inlet pressure. From the findings, it is evident that thermal efficiency increases with increased excess air ratio while volumetric efficiencies reduce with maximum at 41.25% when compression ratio is 13:1 and excess air coefficient is 2.5. The NOx emissions take a non-monotonic trend, reaching a maximum value of 1950 ppm with excess air value of 1.5 and then decrease as air becomes leaner. Although high compression ratio augments the possibility of aberrant combustion, it is also contributing towards combustion phasing and lean burn limit at 5.0 excess air coefficient when the compression ratio is 13:0. Power, efficiency and emission trade offs indicate that excess air coefficient of 2.5 is optimal for balancing thermal efficiencies and NOx minimization while that of excess air coefficient of 1 gives the best power output. Since, this work provides valuable information regarding compression ratio and excess air coefficient adjustments for the improvement of Hydrogen internal combustion engine operation, it contributes to the transition to sustainable air transportation.