A Study on Micture Formation in Propane Spray by Laer Induced Grating Technique

Since the question in mixture formation is how spray is developing and because a spray is including the fuel in gas as well as liquid droplets, laser induced grating technique which is performable in gas phase is supposed to be carried out. The aim was to investigate the evaporated fuel concentration in a spray during injection process. Such two phase systems are difficult to investigate by commonly used optical diagnostic techniques. Therefore, in this work, the Mie scateering and the LIG techniqes have been applied together to a sirect injection process. The fuel was considered to be propane. The Mie technique hleped to figure out the evaporatoin process of propane during a direct injection proces, as well as the characteristics of the spray. After the charactrization of the bhaviour of the propane spray, based on the maximum spray length and the time duration for total evaporation, a set of LiG measurements were performed. The LIG measurements were carried out at different positons from the nozzle along spray axis where the spray is dense. By applying the LIG technique, a concentration measurement of propane in gas phase during mixutre formation could be done. The results verified that a combination of both techniques, Mie and LiG, is suitable to invetigate liquid propane spray of direct infjeciton processes in liquid and gas phase.

The following improvements could be considered to be done for next measurements. Concerning injection process it is concluded that

1) The duration of the propane injection pulses should be shorter than 5 ms for a more intense air entraiument of rapid evaporation.

2) In order to be sure that no gasou propane from the past measurement will exist at the next measurement the injection repetition rate should be reduced or the gas flow should be increased.

Bases in the discussed parameters before, LIG measurement should be performed

3) At different positions in respect to the nozzle front vertically and horizontally at the boundary of liquid phase sprach, which was detected by Mie scattering, in order to determine the air/fuel ratio of the spray at boundarie radially as well as axially which enable us to understand the mixture formation of a spray.

4) The measurements could be done at two or three different delay times after start of injection (SOI). By this way, the development of mixing the fuel in air can be suceeded.