Temperature measurement with compositional correction of gas mixture based on laser-induced plasma

Laser-induced breakdown plasma was used for gas temperature measurement based on the residual energy of a laser pulse defined as the laser energy detected in the beam path as well as plasma emissions. Gas mixtures with different compositions (O₂/N₂, O₂/CO₂, and O₂/N₂/CO₂) were used to simulate the main components of combustion products at different temperatures. First, the correlation of residual energy and gas temperature was investigated, which showed that the residual energy increased with an increase in the gas temperature. The results showed that it also relates to the gas composition, which would affect the characteristics of laser-induced plasma. Then the spectral emission ratio of the plasma (O/N, O/C, and C/N) was obtained simultaneously to correct the compositional effect on the temperature measurement. Finally, the gas temperature with different components can be obtained by the equation coupled with the gas temperature, residual energy, and gas composition. The corrected temperature is consistent with that obtained by thermocouple and the gas temperature measurement error is less than 3.5% in the range from 309 K to 548 K.