Abstract
ABSTRACTThe design of optimum spiral casing configuration is a difficult task and a big challenge in the field of turbomachinery. Computational fluid dynamics (CFD) analysis of fluid flow characteristics in a turn around spiral casing plays an important role in its design. The objective in this study is to propose an optimum spiral casing configuration by reducing the total pressure loss and increasing the spiral velocity coefficient and average radial velocity at the exit of spiral casing. For this, three different configurations of spiral casing, viz. accelerated, decelerated and free vortex type, with different aspect ratios (ARs) are numerically simulated. A Eulerian velocity-correction method based on the streamline upwind Petrov–Galerkin (SUPG) finite-element method is employed to solve complete Reynolds-averaged Navier–Stokes (RANS) equations governing fluid flow characteristics. The results show that the average radial velocity along the exit of spiral casings is more for elliptical cross-sectional spiral casings of AR>1 when compared to circular cross-sectional spiral casings. The total pressure loss is found to be at minimum for decelerated spiral casings. In the case of decelerated spiral casings, a further reduction in total pressure loss is obtained with elliptical cross-sections of AR>1. The spiral velocity coefficient is found to be at maximum for decelerated spiral casings with AR>1.
Highlights
Hydropower is a clean, renewable energy as it requires only water
Numerical analysis of the fluid flow dynamics in threedimensional spiral casings was carried out using the streamline upwind Petrov–Galerkin (SUPG) finite-element method
Secondary flow exists in the cross-sections of spiral casings, its strength differing from one cross-section to another
Summary
Hydropower is a clean, renewable energy as it requires only water. It is one of the largest sources of renewable energy and the most efficient way to generate electricity. The fluid flow through spiral casings was numerically simulated by Maji and Biswas (1998, 1999) using a finite-element method In their studies, the velocity field, pressure distribution and behavior of secondary flow inside the spiral casing are presented in detail. The effects of elliptical and circular crosssections on flow parameters in different configurations of spiral casing are numerically studied for predicting the total pressure loss, spiral velocity coefficient and average radial velocity at the distributor exit. Based on these results, an optimum configuration is proposed.
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