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.
Purpose. Experimental research on the high-speed interaction of the heat transfer medium jet with the surface of the borehole in the process of fragile rock destruction with the purpose of determination of the heat transfer medium velocity along the borehole surface and the heat transfer coefficient from the heat transfer medium to the rock surface. methodology. Methods of comparative analysis, mathematic and physical simulation modelling as well as experimental research are used. findings. The methodology of experimental research on high-speed interaction of the heat transfer medium jet with the surface of borehole as the lateral surface of the cross duct imitated the rock surface in a borehole is developed. Experimental research that consisted of pressure measurement on the lateral surface of the cross duct at the air jet impingement on the lateral surface is conducted. Experimental research treatment is executed as dependence of absolute pressure at the lateral surface of the cross duct, i.e. absolute pressure on the rock surface, from relative pressure of air before a nozzle and relative diameter of the cross duct. Dependences between the values of pressure before a nozzle and values of pressure on the rock surface, values of relative diameter of the cross duct, nozzle outlet diameter, inner diameter of the cross duct and values of air pressure along the lateral surface of the duct are determined. originality. The work presents physical imitational modelling of high-speed interaction of the heat transfer medium jet with the surface of the borehole in a certain range of geometrical parameters of the cross duct and the nozzle, that is accepted in accordance with geometrical similarity to the technological and processing parameters of plasmatron and borehole diameter before the beginning of thermal reaming process. Practical value. Expediency of high-speed plasma jets application as a thermal tool in the processes of fragile rock destruction and, in particular, in the processes of thermal reaming of the boreholes is substantiated.
Purpose. To study rock spallation dynamics in the process of the borehole thermal reaming and analyze energy consumption of the borehole thermal reaming process by plasma jets of the axial plasmatron.Methods. Field experimental study of rock spallation by plasma jets is carried out with the view to measuring the thermal power of plasma, weight of rock spalls and duration of plasma jets impact on the borehole. VT-200 scales were used to measure the rock spalls weight. In the experimental study, plasma jets flow out directly into the borehole in the granite block. The borehole and plasmatron nozzle parameters are geometrically similar.Findings. Experimental data are processed in the form of a table that shows the following parameters of individual experiments: duration of the borehole surface treatment by a plasma jet; thermal power of a plasma jet; heat release of a plasma jet, weight of the rock spalls, energy efficiency of the rock spallation process; productivity of the rock destruction. Experimental data are processed in the form of the dependence of energy consumption of the borehole thermal reaming on the duration of the borehole inner surface thermal treatment. The range of thermophysical and plasmodynamic parameters of the plasma torch that allow to achieve rock spallation is determined.Originality. The linear relationship between the energy consumption in the process of the borehole thermal reaming by low temperature plasma and the duration of the reaming process is revealed, with energy consumption of the reaming process decreasing dramatically with the increase in the process duration.Practical implications. Methodology of the experimental research into the borehole thermal reaming by plasma jets rock spallation is developed. The results of the study could be applied to borehole drilling processes.
The performed analysis of scientific sources confirms the existence of a small number of publications devoted to the experimental research of the gasdynamics and plasmodynamics of jets used as a heat-transfer medium in the thermal methods of mine rocks destruction. There are almost no experimental and theoretical publications related to the multiple-jet plasmotrons research. The expediency of own experimental researches performing has been substantiated concerning the lateral inflow of heat-transfer medium high-speed jets on the borehole surface. An experimental research has been made of the interaction between the heat-transfer medium high-speed jets and the surface of the borehole imitated by the through duct. The further prospects of this work are the following: to determine the gas velocity along the lateral surface of the through duct and the value of the heating capacity coefficient from the heat-transfer medium to the lateral surface of the through duct, which imitates the rock surface in the borehole. These parameters are required for creating a mathematical model of the brittle destruction of rocks.
Analysis of the perspectives of the coal fuel for thermal power plants is carried out. The necessity of the experimental study for temperature measurement in the boiler furnace. The results of the experimental study are presented: temperature change over time at the burner outlet for different constant pressure value of the backlighting gas, dependence of the temperature at the burner outlet from the backlighting gas pressure for constant concentration value of pulverized coal in coal-air mixture, dependence of the temperature at the burner outlet from the concentration of pulverized coal in coal-air mixture for constant value of the backlighting gas pressure, temperature measurements for constant backlighting gas pressure value, constant value of the concentration of pulverized coal in coal-air mixture when plasmatron is switched and operates for some time range. The results of the study could be applied to the solid fuel treatment for different thermal units.
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