Prysiazhniuk L. Improvement of methods and means of energy characteristics of natural gas measuring

The analysis of the current state of scientific, normative and technical support for measuring the energy characteristics of natural gas is performed in the work. According to the results of the analysis, the indicators of the best samples of equipment in terms of measured parameters, accuracy and performance characteristics, ways of possible development of means of measuring energy performance of natural gas, from high-precision calorimeters to means of express control of natural gas combustion at the place of consumption. On the basis of the conducted analysis the ways of improvement of methods and creation of new means for measurement of heat of combustion of natural gas are substantiated. The problems that need to be solved are formulated and the directions of dissertation research are determined. The theoretical basis of gas calorimeter creation is developed. The kinetics of hydrocarbon combustion reactions are analyzed. Methods and means of quality control of combustion products are investigated. Theoretical substantiation of parameters and mode of operation of gas calorimeter is carried out. Theoretical studies of the process of measuring the heat of combustion of natural gas in an isoperibolic calorimeter have been carried out. The factors that most affect the accuracy of measurement are investigated, and their numerical value for the prototype of the device is determined. The most influential determinant is the range of temperature changes in the calorimetric tank. Restrictions are determined that do not allow to increase the upper temperature in the tank above 30 °C. Two structural schemes of information-measuring systems for determining the Wobbe number are proposed. A mathematical model of the dependence of the error of determining the calorific value on the range of temperature change of the calorimetric capacity of an isoperibolic calorimeter with active control of heat exchange of the calorimetric tank is obtained. A method of increasing the accuracy of the calorimeter by increasing the range of temperature change due to the introduction into the design of means for supercooling the calorimetric liquid to a value lower than the ambient temperature. Disadvantages have been formulated that prevent the use of isoperibolic calorimeters as devices of the highest accuracy for rapid control of the energy characteristics of the gas. The biggest obstacle to the creation of portable isoperibolic calorimeters is the significant thermal inertia, as a result of which the next measurement can be performed only tens of hours from the previous one. Two methods of eliminating this shortcoming have been proposed and analyzed. To reduce the time between successive measurements, it is proposed to introduce into the design means for controlling the thermal conductivity between the calorimetric tank and the thermostated shell, which provide low thermal conductivity during the measurement and high thermal conductivity during preparation. The design of a direct combustion calorimeter has been developed, which provides the possibility of creating technological devices in the manufacture. A microprocessor thermostat control unit on Peltier elements and a module of Peltier elements were developed and tested and tested as part of a calorimeter prototype. The chemical composition and ways of control of combustion products are analyzed and the system of regulation of the stoichiometric composition of the fuel-air mixture with the residual oxygen sensor based on ZrO2 and the CO content sensor is proposed. The additional CO content sensor allows to control the completeness of combustion and to obtain valuable data on the level of toxicity of combustion products in the optimal combustion mode, which is set according to the readings of the residual oxygen sensor. The physical effects that directly correlate with the density of the gas are analyzed and it is proposed to measure the density using the phenomenon of resonance of the gaseous medium in a closed volume. A practical implementation of this phenomenon is the use of the Helmholtz resonator, the principle of which is the occurrence of resonant oscillations of the gas with a frequency that depends on the geometric parameters of the gas-filled container and its density. The dependences of the natural gas adiabatic index on the content of its individual components as the main source of methodological error are found. Metrological analysis of the developed analyzer and densitometer was performed. The algorithm of operation of the information-measuring system is formulated. An information and measurement system for determining the energy characteristics of gas. All separately developed elements are integrated into a complex device - an analyzer of energy characteristics of gas. A method of gas sampling using the proposed set of technical means and a method of measuring the Wobbe number have been developed.