Liquid fuel distribution in the combustion chamber by jet impingement on small cylindrical obstacles

Homogenization of lean air-fuel mixture decreases the flame-front temperature and reduces NOx and particulate matter. Impingement of diesel jet onto an arrangement of cylindrical obstacles as a structure close to Porous media, causes high fuel dispersion in the combustion chamber. The injected fuel impinges on the first cylindrical obstacle and splits into two smaller jets and with impingement on other obstacles causes multi-jets splitting in the combustion chamber and fast mixture formation. In this paper, the injection of diesel fuel into a constant pressure chamber is simulated using CFD software. First numerical results of jet length, jet width, jet distribution angle, and spray cone angle shape, were validated with experimental data. Then, effects of obstacles diameter (1, 2 mm), injection pressure (400, 800, 1200 bar), the distance between the nozzle and first obstacle (4-12 mm) for two arrangements of obstacles (one and three cylindrical) on jet length, jet width, jet distribution angle, spray cone angle shape, and jet fuel impingement with hot obstacles impingement, have been investigated. Two new arrangements of cylinders were suggested. First, was an arrangement of three and eight cylinders for the most fuel dispersion for homogeneous mixture formation and second was an arrangement for jet leaving shape similar to liquid leaving the shape of high porosity porous medium (PM). Finally, jet impingement of alumina nano particles and diesel fuel blend on jet length, jet width, jet distribution angle have been studied. Results show that with increasing the distance between the cylindrical obstacles, the jet length for all geometrical structures increased by about 1 mm, and the largest change for the fuel distribution angle was related to the 8d1 structure with a 19 deg increase. Fuel spray considerably does not change obstacles' temperature during the injection and the maximum wall film mass is related to an obstacle with a diameter of 1 mm. On the other hand, the addition of alumina nano-particles to diesel fuel decreases the jet length but increases the jet width.