Analysis of thermal plasma diagnostics based on enthalpy probe system

Abstract

The enthalpy probe with the advantages of simplicity, reliability, and low cost, is generally regarded as a powerful tool in thermal plasma diagnostics. However, the enthalpy probe, known as an invasive measurement method, has an impact on the diagnostic process. To this end, impact factors such as probe presence and size, coolant and sampling-gas flow rates on the thermal plasma diagnostics are investigated here based on experimental and simulation studies. Furthermore, an optimized measurement principle of the enthalpy probe was proposed. The results show that the presence of the probe has a strong effect on the plasma flow, and the effect increases as the probe size rises. The coolant flow rate has little effect on the temperature and flow fields, while the probe sensitivity was improved with the increase in coolant flow rate. However, consideration should be given to the sufficient temperature rise of the coolant by reducing the coolant flow rate. Probe sensitivity and velocity continue to increase as the sampling-gas flow rate rises. At the same time, an inappropriate sampling-gas flow rate would deviate from the isokinetic sampling condition which is critical for temperature measurements. In addition, the measurement accuracy was improved by about 3.6% based on the optimized measurement principle compared with the previous measurement principle.