Simulation Study on Combustion Characteristics of a Spark Ignition Engine Fueled with Gasoline—Hydrogen Fuel Mixture

Experiments of a pure gasoline-fueled engine and a hydrogen-enriched gasoline engine with hydrogen volume fractions in the total intake of 1%, 3% and 5% were conducted on an engine test bench at stoichiometric condition, respectively. Simulation models for gasoline and gasoline-hydrogen mixture fueled engines were built based on AVL Boost and calibrated with the measured combustion pressure, intake gas flow and brake mean effective pressure (BMEP) data from the tests. The simulation study was done at the same intake manifolds absolute pressure (MAP) with different hydrogen volume fractions in the intake and various spark timings to investigate combustion characteristics of a hydrogen-enriched gasoline engine. The simulation results showed that the effect of hydrogen addition on improving the engine combustion was more pronounced at low load conditions. The flame development and propagation durations were reduced with the increase of hydrogen enrichment level when hydrogen volume fraction in the intake was below 5%. The maximum BMEP was achieved when hydrogen volume fraction in the intake was 2%. For a specified hydrogen addition fraction, cylinder pressure first increased and then decreased with the advance of spark timing, and achieved the peak value when spark timing was set to be 13 °CA BTDC. The simulation results also showed that the cylinder pressure rise rate and combustion noise were increased, and the relevant crank angle for peak cylinder pressure was getting close to the TDC with the increase of hydrogen addition level, so the ignition timing should be delayed.