Single filtered photodetector-based H₂O emission thermometry for ammonia flames: a cost-effective optical sensing approach

Optical thermometry based on spontaneous flame emission is an efficient temperature monitoring method with wide applications in industrial combustion devices. However, traditional methods relying on spectral soot emission become irrelevant in the combustion of zero-carbon fuels such as hydrogen and ammonia. Here, we report a solution for ammonia flame thermometry based on spontaneous infrared H 2 O emission using a single photodetector (PD). To our knowledge, this is the first time such a handy yet precise temperature monitoring technique has been developed and demonstrated for the thermometry of ammonia (NH 3 ) flames. Specifically, a PD equipped with interchangeable bandpass filters was used to collect the infrared flame emission in two carefully selected spectral bands. Detailed spectroscopic analysis was performed to derive the quantitative correlation between the measured emission and the flame temperature. Extensive experiments were conducted to validate the method for spatially resolved measurements in laminar premixed ammonia flames. The proposed method boasts the significant advantage of being economically scalable to the monitoring of flames produced by industrial zero-carbon fuels due to its low cost and fast data processing.