Design of a Free Turbine for Simulation of Flow in a Turbine-Annular-Diffuser-With-Struts Delivery System

A free turbine is intended to produce the effect of a rotating flow field to be fed into a strutted annular diffuser for simulating a 3D fluid mechanic interaction and effect. This turbine is driven by the flow from a flow driver fan, upstream of the turbine. As sufficient pressure is required for the diffuser air flow, the concept of maximum work generation by a turbine is bypassed in the design intent. An inlet guide vane is designed for the turbine such that the rotational speed of the turbine matches the design intended speed and also produces an axial exit flow (no swirl) at design condition, and a rotating wake for off design conditions. The consideration of using of the inlet guide vanes (rather than usual stator-nozzles) is to avoid a mismatch between the absolute angle of the flow coming from the flow driver fan and the absolute design intent flow angle requirement, to run the turbine. Also, due to the 3D flow effects, some uncertainty exists in determining the exact entry air flow angle to the guide vane; this uncertainty is provided for with a rounded leading edge to the inlet guide vanes. The above design considerations when embedded in the conventional turbine design procedure resulted in an unusual turbine design with very low blade cambers.