The initial stage of flame development has become important for promoting more stable lean/dilute combustion in spark-ignition engines. A technique for taking simultaneous instantaneous measurements of the unburned gas flow and temperature to clarify phenomena related to local extinction is needed. Inexpensive two-color inorganic fluorescent particles (f-particles), which we previously proposed for fluorescent particle image velocimetry of the gas flow around solid objects, have potential for this application. In the present study, we investigate the possibility of carrying out local gas temperature measurements using the combination of two color f-particles and a ratiometric scheme for the simultaneous measurement of the unburned gas flow and temperature in engines. The results show that the two-color f-particles, which contained rhodamine B and rhodamine 6G, emit fluorescence derived from each dye. The fluorescence from dispersed f-particles in two images could be simultaneously detected using simplified dual wavelength optics and a single camera with a high dynamic range. The ratio of fluorescence intensity from the two color f-articles around 577 nm to that around 550 nm shows a linear temperature dependence between 333 and 473 K.
