The opening pressure of the nozzle was 19.0 MPa. The pump speed was 600 rpm. Diesel fuel (JIS No.2) was used as an injection fuel. The vessel was filled with N2 gas and the pressure was set at 0.5, 1.0, and 1.5 MPa at room temperature.
A flat wall plate was installed into the pressure vessel. It was set on perpendicular to the direction of spray injection. The growth of the diesel spray was analyzed by high speed photographs taken by a drum camera. The photographs were taken as plain images. Since the sprays were perpendicularly impinged to a wall, they had almost symmetric in appearance. Then we analyzed these images as symmetric ones.
The injection rates were measured using the Bosch type injection rate meter. Figure 2 shows injection rate patterns and injection periods of the sprays investigated in this study. Injection period was determined from both of photographs and the injection rates. The spray having the injection period of 1.8 ms was the short injection spray and its injection rate at early stages was low. The spray of 2.8 ms was the middle duration injection spray having high injection rate at early stage. The spray of 3.8 ms was a long injection but its injection rate at early stage was almost same as the spray of 2.8 ms.
To describe the spray growth behavior, we introduced the spray path penetration [6]. Figure 3 shows the definition of the spray path of the vertical impingement spray. Axial and lateral spray penetrations Lx and Ly were defined in the figure. An imaginary spray tip could be expressed by the position (plotted by ○) which was composed of the axial and lateral penetrations of the spray (plotted by ●). Instantaneous movement of an impinging spray tip was obtained from two spray images which were taken at tinj and tinj + dt. The increment of spray path length during dt was expressed as follows.
Figure 2. Injection rates and periods
Figure 3. Definition of spray path penetration
Figure 4. The spray volume analysis from original impingement spray
