Study on the calibration coefficients of a quasi-dimensional model for HCNG engine

A quasi-dimensional model has been developed for an SI engine fuelled with natural gas/hydrogen blends, the combustion chamber was divided into two zones by the flame front, and a turbulent entrainment combustion model was conducted. This paper investigates the effects of calibration coefficients on the model, which includes the turbulence intensity coefficient C2, the Taylor length scale coefficient C3, and the Ignition lag coefficient Cig. Validation by experiments is carried out under various operating conditions including different ignition timing, excess air ratio, manifold ambient pressure (MAP) and fraction of hydrogen enrichment. The results show that Cig always stay the same at 1.52. When the fuel is pure natural gas, C3 plays an important role in the simulation which changes from 0.95 to 2. The main factor changes from C3 to C2 when the hydrogen fraction increases from 30% to 55%. When the engine is fuelled by pure hydrogen C2 to changes from 1.65 to 2.1.

► A quasi-dimensional model for HCNG engine has been studied under various conditions.
► Coefficients Cig, C2, C3 are calibrated, Cig always stay the same.
► C2, C3 can increase the maximum pressure, but Cig has the opposite influence.
► C3 effected the simulation when H2 fraction is small, it’s C2 when H2 increases.