Analytical and Experimental Studies of Two-Dimensional Flows in a Radial Bladed Impeller

Abstract

The current state of a research program to study flows in radial turbomachines at both on- and off-design conditions is described. Numerical solutions of the flow within a rotating impeller are described based on potential theory using a direct method of solution instead of by relaxation. The experimental apparatus comprising a rotating cascade rig is described. The rig consisted essentially of a rotor mounted horizontally in an open circular water tank. An external pipe system enabled the water to be circulated for either radial inflow or radial outflow. The rotor speed could be varied up to 300 rpm. A variety of perspex shrouded rotor geometries up to a maximum diameter of 3 ft 6 in could be tested. Flow visualization by means of polystyrene particles could be observed by a camera mounted above the rotor on its axis and driven at the same angular speed. A 12-channel electronic flash unit enabled the particle velocity and directions to be photographed. As an alternative to the flow visualization system, a bank of manometers, could be mounted above the rotor and driven at the same rotational speed, i.e., with no relative movement. Static pressure measurements could be taken on the blade faces and within the rotor passages. A comparison is made of the experimental and analytical results obtained for one straight vaned, constant area rotor.

Pressure Measurements in the Blade Passages of a Radial Inflow Turbine

“…The rotor passage vortex has its origin at the hub surface and is most strongly felt at the shroud. Benson et al (1971) described numerical solutions of the flow within a rotating impeller based on potential theory using a direct method of solution instead of by relaxation. There were differences between theory and experiment which could be accounted for by friction effects in the passage associated with boundary layer growth.…”