INVESTIGATION OF FLOW REGIMES OF AIR-HELIUM MIXTURES DEPENDING ON MICROCHANNEL RADIUS WITH LARGE PRESSURE GRADIENT

Анотація

The relevance of the problem of reliable sealing of installations, aggregates and objects that are operated for a long time and work with aggressive environments existing in the chemical and machine-building industries is shown . Varieties of the main types of devices for detecting flow using a test substance are given; the advantages of using helium are shown. The problem of studying the flow of gases through a microchannel, taking into account changes in the flow modes, is formulated. The paper defines the transition boundaries of Molecular and viscosity flow modes for air-helium mixtures depending on the microchannel radius and pressure drop, and also establishes the dependence of changes in the boundaries of Molecular and viscosity modes on the percentage content of air and helium. The study was carried out in an isothermal formulation for two variants of the composition of the air-helium mixture, five values of microchannel radii and differential pressure, which varied widely: with pressure at the outlet of the microchannel = and pressure at the inlet . The calculation method is presented with reference to the original literature sources of Poiseuil, Hagen, Knudsen and other authors who investigated this problem. In order to determine the boundaries of the transition of gas flow in a microchannel from one flow mode to another, a method for determining the boundaries of the transition of modes is presented, according to which the graphs given in this paper are constructed. As a result of the study, it is obtained that when the channel radius decreases, the transition boundary from the molecular flow regime to the intermediate one shifts in the direction of decreasing the flow value; in the same way, in the direction of reducing the flow value, the transition boundary from the intermediate flow mode to the viscous one also shifts. The obtained results allow us to analyze the nature of the influence of microchannel radii on the flow modes of mixtures through the microchannel, depending on the flow parameters. Based on the obtained data, when monitoring devices and installations for tightness, it is possible to choose an air-helium mixture that comes into contact with aggressive media at high temperatures перепадах тиску.