Study of the plasma flow interaction with the borehole surface in the process of its thermal reaming

Purpose. Study of the plasma flow interaction with the borehole surface in the process of its thermal reaming for determination of transient temperature distribution along the borehole surface and the average coefficient of heat transfer from the plasma flow to the borehole surface. Methods. Experimental study of the plasma flow interaction with the flange union with internal lateral surface simulating the rock surface in a borehole has been carried out. The essence of the experimental study is in measuring temperature of the flange union external side while the plasma flowing inside the flange union. To measure temperature on the external surface of the flange union, a chromel-alumel thermocouple with thermoelectrodes of 1.2 mm in diameter was used. In experimental research, plasma flows out through a nozzle directly to the flange union made of copper. The parameters of the flange union and the nozzle of plasmatron are geometrically similar. Findings. Experimental data are processed as a relationship between the temperature of the copper flange union lateral surface, i.e. borehole surface, and the time of the copper flange union heating by the heat carrier. Experimental data are processed as a dependence of temperature of the tin pipe side surface, i.e. surface of the borehole, on the location of temperature measurement point along the tin pipe and the time of the tin pipe heating by the heat carrier. Originality. Physical simulation modeling of the heat carrier (low temperature plasma) flow interaction with the borehole surface simulated by the copper flange union and the tin pipe in a certain range of geometrical parameters of the copper flange union, tin pipe and the plasmatron nozzle as well as thermophysical properties of the heat carrier assumed in accordance with geometrical similarity to the technological and design parameters of the plasmatron and borehole diameter before the beginning of thermal reaming process. Practical implications. Methodology of experimental research of the heat carrier (low temperature plasma) flow interaction with the borehole surface that was simulated by the copper flange union of the tin pipe is developed. The results of the influence by high-temperature heat carrier jets on the processes of fragile rock destruction are rather useful in the borehole drilling processes.