Aerodynamic Investigations of an Advanced VIGV Design of Adjustable Geometry for Very High Flow Turning

On the basis of experimental results the new design of a Variable Inlet Guide Vane (VIGV), as can be used for the control and regulation in multishaft compressors, is presented. Main goal of this investigation is a significant increase of the operating range and a reduction of the total pressure loss compared to a currently used basic design. For both designs 2D-cascades were build for detailed measurements in the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion at the Universität der Bundeswehr München. The basic design exhibits a symmetric profile with only one segment. In contrast to that the new VIGV design consists of two symmetric vane segments which are arranged pivotable to each other. This provides the advantage of a symmetric profile for a fully opened VIGV associated with a low-loss level. For guidance of the flow, both vane segments can be rotated. Hence, the turning of the flow is split onto two segments. This avoids a huge flow separation on the suction side for high turning angles (Δβ > 30°) which is linked with a strong and abrupt loss increase. Due to the design, the new VIGV exhibits a gap between the two vane segments. Results with opened and sealed gap are presented and discussed. Using a sealing between the segments, a reduction of the profile loss could be detected for all investigated operating conditions. Even without a sealing in the gap, the “low-loss working range” is significantly increased. In addition, it is depicted that the presented results are valid for varying inflow velocities. This broadens the usability of the outcomes. Concluding, it is shown that all aims are achieved. Using the new VIGV design with sealing the low-loss working range can almost be doubled (Δβ > 55°) and the total pressure loss decreases in every working condition compared to the basic design.