Figure 5. Penetrations of wall impingement sprays on the 1.8 ms-sprays
Figure 6. Penetrations of wall impingement sprays on the 2.8 ms-sprays
Figure 7. Penetrations of wall impingement sprays on the 3.8 ms-sprays
This spray path could present the scalar length along the spray movement before and after impingement. According to previous work [6], it was proved that this spray path coincided with the conventional spray tip penetration. Figure 4 shows the analysis method of spray volume. In order to obtain the spray volume, all the photographic data were analyzed with a computer. The contour lines of spray peripheries were obtained by computer image analysis. By means of computer, all the photographic image was changed to binary value of u = 1 (spray) and u = 0 (space). Then the spray volume V could be calculated by an asymmetric model and following equation.
3. EXPERIMENTAL RESULTS
3.1 Penetrations of Wall Impingement Sprays
Spray path penetrations of wall impingement sprays on the 1.8 ms-sprays under ambient pressure of 1.5 MPa are shown in Fig 5. For the comparative study, spray path penetration of a free spray is also displayed in the figure. Horizontal solid lines in the figure indicate the distance Lw from the nozzle tip to the wall. The spray was impinged to the wall of distance Lw. With this impingement, the penetration of post-impingement spray began to increase slowly. So, it was considered that the momentum loss occurred with the impingement.
Figures 6 and 7 show the spray path penetrations of 2.8 ms- and 3.8 ms-sprays under the same ambient pressure of Fig.5. In comparison of these two figures, the penetration rates of 2.8 ms-sprays were similar to those of 3.8 ms-sprays. Also the increment slops on penetrations of 2.8 ms- and 3.8 ms-sprays were steeper than those of 1.8 ms-sprays in Fig.5. In this study, similar tendency was also observed under ambient pressures of 0.5 MPa and 1.0 MPa. Here, the sprays of 2.8 ms- and 3.8 ms -injections had similar injection rates at the early stage. Then, they had similar spray tip penetrations nevertheless of different injection periods. This result corresponds with the result of the previous papers reported by the authors[10, 11].
However comparing two figures closely, the penetration rates of 3.8 ms-sprays were still little higher than those of 2.8 ms-sprays. It seemed that the spray tip penetration after the early stage of injection depended on injection rate history. It seemed that the injection rate rise of 3.8 ms-spray was maintained until 2.2 ms from injection start, while that of 2.8 ms-spray lasted only about 1 ms. It was considered that spray tip penetration was affected not only by injection rate at the early stage of the injection but also by injection rate history.
From figures 5, 6 and 7, it was confirmed that the spray path penetration of impingement spray was lower than that of the free spray. Also, with increase of wall distance, the spray path penetration became longer. It was concluded that as the wall distance was short, the momentum loss that occurred at impingement point became larger.
3.2 The Comparison of Spray Volumes
The comparison of spray volumes at injection period of 1.8 ms is shown in Fig.8. The broken line is corresponding to the volume of the free spray.
