  The thermographic phosphor ScVO4:Bi3+ is used to obtain time-resolved surface
temperature measurements with sub-oC precision at 5 kHz. Measurements are used
to study transient heat loss and flame-wall interactions (FWI) within a
dedicated narrow two-wall passage (crevice) in an optically accessible fixed
volume chamber. This passage emulates a crevice relevant in many technical
environments, where FWI is less understood due to lack of detailed
measurements. Chemiluminescence (CH*) imaging is performed simultaneously with
phosphor thermometry to resolve how the spatiotemporal flame features influence
the local surface temperature. ScVO4:Bi3+ is benchmarked against
Gd3Ga5O12:Cr,Ce, a common phosphor used at low-kHz rates in FWI environments.
ScVO4:Bi3+ is shown to offer higher luminescence signal levels and temperature
sensitivity as well as negligible cross dependence on the excitation laser
fluence, improving the precision and repeatability of the wall temperature
measurement. ScVO4:Bi3+ is further used to resolve transient heat loss for
variations in crevice spacing and uniquely capture temperature transients
associated with flame dynamics. Taking advantage of these precise surface
temperature measurements the wall heat flux is calculated with crevice spacing
of 1.2 mm, where flame extinction is prevalent. Wall heat flux and estimated
quenching distance are reported for flames that actively burn or extinguish at
the measurement location.
