Laser Raman scattering method has been applied to measure equivalence ratio of methane/air mixture in injected spray. We used high power KrF excimer laser(λ=248nm) and a high gain ICCD camera to capture low intensity Raman signal. Raman shifts and Raman cross-sections of H2, O2, N2, CO2, CH4 and C3H8 are measured precisely. Our results show an excellent agreement with other groups. Mole fraction measurement of O2 and N2 from air shows that O2 : N2 = 0.206 : 0.794.
We used gas injector which is operated at 1 bar. Methane is used as a fuel. Spray region is 10 mm × 37 mm and this region is divided into 80 points. 100 Raman signals are obtained and ensemble averaged for each point. 3-d and contour plot of distribution of equivalence ratio is presented. Our measured results show that the equivalence ratio of methane/air mixture in methane-rich region is reasonable. However, more study is necessary for methane-lean region because background noise level is almost same as Raman intensity of methane.