Effect of Nozzle Inclination Angle on Fuel-Air Mixing and Combustion in a Heavy Fuel Engine.

Heavy-fuel engines are widely used in UAVs (Unmanned Autonomous Vehicles) because of their reliability and high-power density. In this study, a combustion model for an in-cylinder direct injection engine has been implemented using the AVL FIRE software. The effects of the angle of nozzle inclination on fuel evaporation, mixture distribution, and combustion in the engine cylinder have been systematically studied at 5500 r/min and considering full load cruise conditions. According to the results, as the angle of nozzle inclination increases, the maximum combustion explosion pressure in the cylinder first increases and then it decreases. When the angle of nozzle inclination is less than 45°, the quality of the mixture in the cylinder and the combustion performance can be improved by increasing the angle. When the angle of nozzle inclination is greater than 45°, however, the mixture unevenness increases slightly with the angle, leading to a deterioration of the combustion performances. When the angle of nozzle inclination is between 35° and 55°, the overall combustion performance of the engine is relatively good. When the angle of nozzle inclination is 45°, the combustion chamber's geometry and the cylinder's airflow are well matched with the fuel spray, and the mixture quality is the best. Compared with 25°, the peak heat release rate increases by 20%, and the maximum combustion burst pressure increases by 5.5%. [ABSTRACT FROM AUTHOR]