Kostyk I. Measurement of flow rate of gaseous fluids with variable gas-dynamic flow structure

The dissertation work is devoted to research of influence of a variable gas-dynamic flow structure on the accuracy of flow rate measurement for gaseous fluids by means of the differential pressure method. By analyzing the physical principle of the process of flow rate measurement for non-stationary flow the additional components of uncertainty of the measured value of the flow rate are revealed and classified for non-stationary flow. To define the values of these components of uncertainty, the technique for estimating the additional component of uncertainty caused by the nonlinear dependence between the flow rate and the differential pressure is improved. The technique for estimating the additional component of uncertainty caused by the absence of the inertial term in the sub-root expression of the quasi-stationary flow equation is also improved. The mathematical model of the pneumatic channel of the pressure (differential pressure) transducer was developed. The experimental setup for studying the dynamic properties of the pneumatic channel was developed and the experiments were carried out. The adequacy of the developed model was confirmed by the results of the experimental study. The dependence of the resonance frequency on the design characteristics of the channel was investigated by applying a linearized mathematical model of the pneumatic channel. The recommendations for avoiding the resonance in the pneumatic channels of pressure (differential pressure) transducers were developed. The experimental flow measuring facility was developed and the study of the influence of protrusions at the internal surface of the measuring pipe of a differential pressure flow meter on the discharge coefficient of orifice plates was carried out. Based on the results of experimental studies, new analytical dependences were developed for quantitative assessment of the additional uncertainty of the orifice plate discharge coefficient, caused by the influence of protrusions at the internal surface of the measuring pipe. The equation of combined uncertainty of the measured flow rate value is improved by introducing additional components of uncertainty, caused by non-stationary flow of gaseous fluid and by the influence of protrusions at the internal surface of the measuring pipe. The improved equation provides the possibility to expand the scope of the differential pressure method for measurement of flow rate of gaseous fluids with variable gas-dynamic flow structure. The results of the dissertation were implemented in R&D and production companies involved in research, design, production and installation of fluid energy carriers metering systems.