Loss and Outlet Flow Angle Estimation in Rectangular Scrolls for Radial Turbines by a Constructed Flow Model

The flow model and loss model in the rectangular scrolls constructed from the main flow with free vortex flow, the 3D equilibrium boundary layer on the side walls and the 2D boundary layer on the inner and outer walls, and the equation to estimate the loss in it were made in this research. The model is based on the theory of the 3D equilibrium boundary layer. The calculated results of it are shown good coincidence with test results. The flow equations are made from the 3D boundary layer equation with 1/n multiplier law and Mager's equation, and main flow with free vortex flow. Those equations have three unknown variables which are n, boundary layer thickness and radial velocity parameter. The mean outlet flow angles are estimated by using the values of those three variables decided by the measured volocity distributions. It is made clear that the flow rate of main flow is reduced by the flow through the 3D equilibrium boundary layer and the outlet flow angle become small at the main flow, and the loss less main flow is sustained for being main flow.