Experimental Study of Impingement Spray of Dual-fuel Injector of Opposed Piston Two-stroke Diesel Engine

Due to the special combustion chamber shape and spray mode of opposed piston two-stroke diesel engine, the fuel injection sprays impinge at the center of combustion chamber. The good matching of combustion chamber shape, spray characteristics and in-cylinder gas flow should be assured to obtain desired gas mixture. For the spray characteristics of combustion chamber in opposed piston two-stroke diesel engine, the schlieren method is used to study the influences of fuel injector position, injection pressure, constant volume bomb pressure and injection duration on spray penetration and spray spatial diffusion rate. The results show that, compared with single injector, the dual-fuel injector has higher spatial diffusion rate and is more beneficial to the atomization of fuel in the case of 75 MPa injection pressure, 2 MPa constant volume bomb pressure and 1.5 ms injection duration. The increase in injection pressure is beneficial to the diffusion of fuel in space, but the fuel distributed in near-wall area would be increased. As a result, the emission will be worsen because of “cylinder wall wetting”. Low constant volume bomb pressure causes a rich mixture near the cylinder wall, while high back pressure makes the fuel concentrate in the center of combustion chamber where the flow is weak. With the increase in injection duration, the increase in spray penetration and spatial diffusion rate becomes less noticeable.