Analysis of Pressure Propagation in the Combustion Chamber of Diesel Engine by Means of Water Model

It was suggested in the previous paper that the area of the connecting passage in a divided chamber type Diesel engine determines whether a sharp pressure rise in the auxiliary chamber transmits to the main chamber or not. No attention, however, was paid to the pressure wave propagation in the combustion chamber that would possibly be of importance. In order to make up for this, the water analogue method was applied simulating such a two-dimensional unsteady flow problem. Test results show that, with a wide connecting passage, a sharp pressure pulse is formed and spreads in the main chamber, followed by a rapid pressure rise and pressure vibration of relatively low pitch. Such pulse and vibration decline with a decreasing of the area of the passage and with a smoothing of the pressure rise in the auxiliary chamber. Owing to this pulse, the maximum rate of pressure rise in the main chamber is exceedingly larger than the theoretical value predicted in the previous paper, while the average rate virtually coincides with the latter if fine waves are ignored.