Diagnostics of Resistance Coefficients and Cavitation of Flow Control Valve

Abstract

The paper deals with the determination of characteristic as dependence of the valve pressure drop on the flow rate, flow characteristic and cavitation conditions in case of water flow in the flow control valve. Emphasis is put on the utilization of simple, available relationships and measuring for identification of the basic valve coefficients, e.g. loss coefficient, flow rate coefficient and cavitation factor. These coefficients are used for designing of pipe circuits. In this paper there is defined methodology for determining those coefficients and is applied to the modified cone of flow control valve for verification the linear flow characteristic. It is necessary to consider the fact that in various countries the modifications of coefficients are preferred and it is therefore necessary to specify them.

Flow characteristics of control valve for different strokes

“…The presence of air and vapour cavitation was also confirmed in other hydraulic elements [13,14,15].…”

“…The outlet is given by pressure boundary condition and is specified from experimental measurement, so the pressures on outlet are the same. From the literature [13,14,15] it is evident that air cavitation refines numerical calculation. The amount of air in the liquid is difficult to measure and it is only determined from the numerical experiments.…”

“…) where p 1 is the absolute pressure at the inlet of the valve; p v is the saturated vapour pressure for a given temperature; p 2 is the absolute pressure at the outlet of the valve. The critical value of cavitation index that determines the beginning of cavitation for the valve construction was determined based on a calculation from the experiment, see [8,13,15]. The value of cavitation index equals 2 and corresponds to the measured valve.…”

“…Two equation cavitation turbulent k-İ RNG model on the basis of the Reynolds number and recommendations of the literature [9,12,13] was selected. The third phase i.e.…”

Physical and mathematical fundamentals of cavitation

“…The dependence between flow rate Q and pressure loss Δp is the basic characteristic of the valve. This dependence is comprised of partial characteristics for the selected cone strokes of control valve, and it is determined experimentally [4,8]. The test circuit is on Fig.…”