Effects and grey relational analysis of electronic control parameters on mixture formation and combustion characteristics of an aviation piston engine during cold-start

Deteriorated cold-start performance in plateau or extremely cold environments is a major challenge limiting the environmental adaptability of the aviation piston engines. A 3D combustion numerical model characterizing cold-start operation was developed and validated through overall engine tests and constant volume combustion chamber (CVCC) spray experiments. The effects of 6 electronic control parameters on spray, mixture formation, ignition, combustion characteristics, and parametric sensitivity were investigated. Results show that pilot injection (PiI) strategies helped form a larger equivalence ratio region (0.6∼1) that was more favorable for ignition and combustion around the periphery of the spray core after main injection (MI). PiI 2 timing had minimal influence on in-cylinder pressure, pressure rise rate (PRR) and heat release rate (HRR). Increasing PiI 2 and PiI 1 quantities enhanced combustion pressure, PRR and HRR during power stroke, though their phases of peaks first advanced and then retarded. The optimal MI timing in this study was identified as −15 °CA BTDC. As injection pressure increased from 40 to 160 MPa, LPL and VPL of spray gradually increased, while the Sauter mean diameter (SMD) gradually decreased. This facilitated to improvement of the spray atomization quality to form a larger near stoichiometric equivalence ratio region (0.8∼1.2) and accelerated the transition from low-temperature combustion (LTC) to high-temperature combustion (HTC), thus increasing the mean combustion temperature. OH was generated in the region of temperature above 2000 K, and the higher the temperature, the more OH was produced. Simultaneously, during power stroke, in-cylinder pressure, PRR, HRR and their peaks progressively increased. The order of sensitivity to the effects of maximum in-cylinder pressure and OH mass fraction peak was: pilot injection number > injection pressure > PiI 2 quantity > PiI 1 quantity > PiI 2 timing > MI timing. These findings support optimizing electronic control parameters for robust cold-start strategies.