Experimental Investigation into the Application of Spontaneous Raman Scattering to Spray Measurements in an Engine

摘要

The use of spontaneous Raman scattering as a laser probe for precombustion engine spray measurements has been investigated for a continuous-wave laser system. Topics of experimental importance such as spectroscopic distinction between the liquid and vapor phase of the fuel, spray fouling of windows, laser transmission through the spray, laser-droplet induced background, and others are discussed. A technique for vapor temperature measurement in precombustion, vaporizing fuel sprays was derived and applied. Mie scattering has been used to complement the Raman measurements. Results of the study indicate that vibrational Raman scattering alone cannot distinguish between liquid- and vapor-phase propane fuel, at least for the spectral resolution found to be most useful in engine mixing studies. However, when combined with the Mie scattering diagnostic, it was possible to distinguish between liquid and vapor regions and to make sensible, time-averaged number density measurements in the spray boundary. Inherent limitations of the continuous-wave experiment prevented separation of fuel number density measurements obtained in two-phase flow regions into a liquid and vapor phase contribution. Modifications to the experiment which would avoid this difficulty in thin-spray regions have been identified. (ERA citation 06:022259)