Design of a needle throttle valve using computational fluid dynamics

The article is devoted to the development of the geometry of the flow part of a quadratic throttle with a needle shut-off and control element using computational fluid dynamics. The paper presents the results of calculating the main geometric parameters of the flow part of the throttle for a given nominal mass flow rate and operating range of the needle stroke. It is shown that the results of calculating the flow characteristic of a quadratic throttle significantly depend on the recommendations for choosing the values of the hydraulic resistance coefficients of its flow part. Therefore, to select the geometric parameters of the flow part of the throttle, it is advisable to carry out numerical modeling of the fluid flow in it. The article presents the parameters and results of modeling the fluid flow in the flow part of a needle throttle in two versions at different positions of the shut-off and control element. Based on the modeling results, the flow characteristics of both throttle versions are determined and the choice of the optimal throttle version in terms of linearity of the flow characteristic and the width of the flow control range is substantiated. In addition, based on the results of numerical modeling, the magnitude of the force acting on the shut-off and control element from the liquid side in each studied position of the needle was determined. Also, the fields of velocity distribution and static pressure in the longitudinal section of the flow part of the throttle were obtained, which allow us to estimate the hydrodynamic picture of the liquid flow and the presence of additional undesirable resistances in the flow part, as well as the possibility of receipt effects in the working range of mass flows. The throttle under study was manufactured and subjected to an experimental study to determine the actual flow characteristic of the device. The experimental results showed that the discrepancy between the actual flow characteristic and the characteristics obtained as a result of numerical modeling does not exceed 5 % in the entire working range of the shut-off and control element.