Abstract
Direct injection gasoline engines have been developed for improvement of fuel economy and exhaust emissions. Recently, a new stratified charge combustion concept is proposed. A slit nozzle is adopted to realize the new concept. The nozzle has a rectangular orifice as shown in figure 1 and forms a thin-fan shaped spray. This paper describes the spray characteristics of the slit nozzle. The following results were obtained. (1) The spray tip penetration increases with increasing the slit thickness as shown in figure 2. And the calculated results based on Waguri's spray momentum theory agree with the measured spray tip penetration. (2) The relation between the Sauter mean diameter and the effective factors is described by the following equations. For lower injection pressure ΔP=0.1 MPa to 0.3 MPa : d_<32> ∝ ΔP^<-0.25>・H^<0.3> For higher injection pressure ΔP=6 MPa to 14 MPa : d_<32> ∝ ΔP^<-0.5>・H^<0.1> where d_<32> is Sauter mean diameter, ΔP is injection pressure and H is slit thickness. Next, the spray characteristics of the slit nozzle are compared with that of a swirl nozzle. Both nozzles are commercially available. (3) The Sauter mean diameter of the slit nozzle is slightly smaller than that of the swirl nozzle as shown in figure 3. (4) As shown in figure 4, at 0.1 MPa back pressure, the difference in the spray concentration of both nozzles is small. On the other hand, at 0.5 MPa back pressure, the spray concentration of the slit nozzle is lower than that of the swirl nozzle, especially in the center of the spray. (5) It is clarified from the above mentioned results that the feature of the slit nozzle is high spray penetration, widely diffusion spray and fine atomization.
