EXPERIMENTAL DETERMINATION OF PRESSURE TUBES COEFFICIENTS
DOI:
https://doi.org/10.30837/2522-9818.2020.12.148Keywords:
pressure tube, pneumometric method, tube coefficient, velocity, flowAbstract
The subject of this research is pressure tubes, which serve as sensors for instruments measuring the velocity and flow rate of gases by the pneumometric method. The purpose of the work is to improve the method of determining the coefficients of pressure tubes in order to increase the accuracy of measuring the velocity and flow rate of gases. The article solves the problem of experimental determination of the coefficients of a point and averaging pressure tubes in the velocity range from 2 to 20 m/s. The average coefficients of the pressure tubes and the error caused by the displacement of the orientation of the pressure tube from the flow axis at a speed of 10 m/s were calculated at the average value of the coefficient of the pressure tube for the studied tubes. The studies used methods of analysis and synthesis, analytical and descriptive geometry, probability theory, mathematical statistics, and numerical methods using computer technology. The results of the work are presented in the form of graphical dependencies of the pressure tube coefficient as a function of gas flow rate. The graphical dependence of the flow velocity on the angle of rotation of the axis of the pressure tube relative to the axis of the flow at a speed of 10 m/s at the average value of the coefficient of the pressure tube for the tubes that participated in the experiment is also shown. Conclusions: the method for determining the coefficients of a point and averaging pressure tubes has been improved. It was found that in most of the investigated tubes, the pressure coefficient of the pressure tube is not stable at the velocity range from 2 to 20 m/s. Thus, an additional error arises due to the instability of the pressure tube coefficient, since the coefficient of the pressure tube is proportional to the gas flow rate. The most stable coefficients are Pitot tubes and TNU-8-6. The Pitot tube has an average coefficient of 1.009, the stability of the coefficient of the tube relative to the average value was ±0.8%. The TNU-8-6 tube has an average coefficient of 0.6683, and the tube coefficient stability for the average value is ±1.3%. Also included are recommendations for velocity meter software and gas flowmeters to reduce instrumental error.
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