An orthogonal numerical simulation experiment study towards the decay characteristics and effective swirl length of the swirling flow in a vortex tool inserted tube

Abstract

Studying the decay characteristics and effective swirl length of the gas-liquid two-phase swirling flow generated by vortex tools is of great significance for improving its drainage effect. The effective swirl length is a key parameter related to the working performance, installation spacing and downstream pressure dynamics of vortex tools. However, works addressing the effective swirl length are rare in the literature. In this research, the decay characteristics and effective swirl length of a swirling flow and the factors that affect the swirling flow are systematically investigated using the orthogonal numerical simulation experiment method. Good agreements are achieved between existing experimental data and the numerical results of this study. The range analysis results reveal that the helix angle, mandrel diameter and vane axial length play dominant roles in the initial swirl intensity. An increase in the helix angle results in a decrease in the initial swirl intensity, while the mandrel diameter has the opposite effect. The swirl intensity decay rate is mainly affected by the Reynolds number, helix angle and vane axial length; the decay rate has a negative correlation with the first two factors and a positive correlation with the third factor. On this basis, a comprehensive decay model of the swirl intensity is proposed after obtaining the correlations for the geometrical swirl intensity and swirl intensity decay rate. Furthermore, an effective swirl length evaluation method is established, and the optimal vortex tool structure of a typical gas well is obtained with a helix angle of 55°, a mandrel diameter of 38 mm, a vane axial length of 120 mm and a vane width of 15 mm.