An Approach to Thermocouple Temperature Measurements that Reduces Uncertainties Associated with Radiative Corrections
Obtaining accurate temperature measurements in flame environments with thermocouples is extremely challenging due to the effects of radiative heat loss. These losses are difficult to quantify and often cannot be corrected for or minimized without sacrificing spatial resolution. In this work, a new experimental methodology is presented that has shown potential to minimize the temperature correction by both increasing and controlling the effects of convection. This is accomplished through high speed rotation of the thermocouple. The rotation yields a high and known convective velocity over the thermocouple. Heat transfer can then be modeled for the thermocouple, and a functional relationship between temperature and rotational speed can be found. Experiments were conducted over a range of rotational speeds in a control flame with a known temperature to test the feasibility of the rotating thermocouple (RTC) technique for temperature measurements in high temperature gases. The experimental results are shown to closely match the theory for the experimental gas temperature, over a range of rotational speeds, yielding extremely accurate gas temperature measurements. The results also demonstrate minimal perturbation to the flow field, even at high rotational speeds. Additionally, a deconvolution technique is proposed that would significantly enhance the spatial resolution of the technique.
Temperature measurement, thermocouple, radiation correction, Engineering, Mechanical Engineering
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