Effect of Blend Fuel Properties on Combustion Improvement Under Heterogeneous Combustion Field by Using Multi-Impinging Injection System

To solve the engine performance deterioration and emission problems caused by fuel spray impingement on combustion chamber wall from direct injection internal engines, we bring out the new fuel injection concept, which we call it the impinging injection method. The impinging injection method uses two opposite injectors and tries to achieve spray atomization effect from the fuel sprays collision. A constant volume combustion chamber was used to confirm the spray characteristics and the combustion improvements. Previous study confirmed a significant reduction of spray/wall impingement and combustion improvements. Therefore, in this study, from the aspect of surrogate fuel, we investigated the spray and combustion characteristics of n-butanol addition blend with iso-octane and n-hexadecane, respectively, by using impinging injection and multi-impinging injection with different injection timing conditions. The n-butanol addition ratio ranged from 0% to 50%. Since the blend fuels have different lower heating value (LHV) and liquid fuel is difficult to ignite at the atmospheric condition, the propane-air mixture with different equivalence ratios was used to keep the overall equivalence ratio the same. Moreover, the laser diffraction spray analyzer (LDSA) detected the sauter mean diameter (SMD) of fuel spray around the spark ignition area. The results indicated that the atomization improvement exists by using the impinging injection with n-butanol blend fuels. Especially the reduction of SMD for high viscosity fuel was significant. From the combustion characteristics results, iso-octane with 25% n-butanol and n-hexadecane with 0% n-butanol showed combustion improvement with multi-impinging injection. However, 50% n-butanol addition deteriorated the combustion characteristics with the interaction of n-butanol evaporation effect and low LHV. These results indicate that the atomization effect of impinging injection method with n-butanol blend fuel, and the optimal blend ratio with injection timing conditions exist for different fuel types, which suggest the possibility for blend fuel application with impinging injection method.