Calculation of three-dimensional boundary layers on turbomachinery blades

The aerodynamic behaviour of turbomachinery is dominated by viscous effects. In the design of a component for the machine, inviscid methods are normally employed. However, it is useful to cover the viscosity in the calculation to achieve a better understanding of the fluid behaviour. This feature can be analysed by using Navier-Stokes calculations or simpler and more approximate techniques such as boundary-layer calculation. In recent years there have been a considerable number of Navier-Stokes solvers as well as boundary-layer solvers. However, Navier-Stokes methods require a large amount of computer storage and CPU time, which limits the number of grid points that can be used inside the boundary-layer. Hence, boundary-layer techniques become very attractive. The purpose of this study is to develop a boundary-layer calculation that is efficient, accurate and simple to implement, and can be applied to flow over complex geometry such as turbomachinery blades. To account for the surface curvature and rotation, the three-dimensional unsteady boundary layer equations are expressed in generalised curvilinear co-ordinate system on the body surface with respect to a rotating frame of reference. The equations are solved numerically by using Finite Difference Approximation without employing the similarity transformation. The steady state solutions are obtained by integrating the equations in time. Two methods, an interactive scheme and FLARE approximation scheme, are described for calculating separated flow. The concept of the interactive approach is general but its application, in this study, is limited to two-dimensional flow. The viscous losses, expressed in term of entropy generation, is also calculated from the computed flowfield. Computational results on a wide variety of flow situations and configurations are validated and show good agreement with analytical results and experimental measurements. Results reveal, in general, that the method holds a practical advantage, in both speed and accuracy of computation, for solving the boundary-layer problems to which it is best suited

Determination of Hydraulic Ram Pump Performance: Experimental Results

The possibility of using a hydraulic ram pump (HRP) as a means of utilizing its energy to produce high head for pump has been investigated. To make such a system economically competitive, it is necessary to improve the performance of HRPs. To achieve this improvement, it is also necessary to understand the parameters that marked out the design of conventional HRPs. The performance is presented in dimensionless terms as the head ratio H∗ or discharge head to drive head and flow-rate ratio Q∗ or discharge flow rate to drive flow rate. The experiments on HRPs were conducted by which each of the following factors could be varied independently: (a) supply head, (b) air chamber pressure, and (c) waste valve beats per minute. An increase in the supply head tends to increase the supply flow rate, delivery flow rate, delivery head, and the overall efficiency of the pump. An increase in air chamber pressure tends to decrease the overall efficiency of the pump. However, there was no significant difference on the HRP performance over a wide range of flow conditions when air chamber pressure was varied. An increase in waste valve beats per minute tends to decrease the supply flow rate, delivery flow rate, and delivery head. But it tends to increase the head ratio, the flow-rate ratio, and the overall efficiency of the pump. The experimental data reveal that the HRP characteristics are functions of the waste valve beats per minute and the supply head