铠装热电偶护套的发射率测量与分析OA

[Objective]Due to the radiant heat loss,mineral-insulated metal-sheathed(MIMS)thermocouples measure temperatures lower than the actual fluid temperature when they are used in flowing gases.Notably,this radiant heat loss is directly related to the surface emissivity of the thermocouple sheath.To correct the measurement results,herein we investigate the emissivity of the MIMS thermocouple sheath.[Methods]In this study,we measured the emissivity of a 3.2 mm MIMS thermocouple sheath using both fuel-lean and fuel-rich Hencken flames.Computational Fluid Dynamics(CFD)simulations were employed to model the measurement process.By iteratively adjusting the emissivity until the simulated junction temperature matched the experimental temperature reading,the sheath surface emissivity was obtained.[Results]In the fuel-lean flame(oxidizing environment),as the thermocouple temperature increased from 1 073 K to 1 371 K,the sheath emissivity increased from 0.63 to 0.77.In the fuel-rich flame(reducing environment),as the temperature increased from 1 111 K to 1 278 K,the emissivity increased from 0.43 to 0.46.The thermocouple emissivity in the reducing environment was significantly lower than that in the oxidizing environment.This trend of emissivity changing with temperature and oxidation degree is consistent with previous studies,but specific values differ.Such a phenomenon indicates that the composition of the measured gas also affects the sheath emissivity of the MIMS thermocouple.[Conclusion]The composition of the measured gas significantly changes the thermocouple emissivity by altering the surface composition of the MIMS thermocouple sheath.