Nozzle Guide Vane Design for Dual Function Throttling Using Active Flow Control

Abstract Previous experiments demonstrated the effectiveness of using fluidic actuators to decrease the core mass flow through a nozzle guide vane. An investigation was conducted into increasing the mass flow through a nozzle guide vane using fluidic actuators. Coupling actuators that increase mass flow with actuators that decrease mass flow allows for a Variable Area Turbine (VAT) that has dual function throttling control without mechanically moving vanes. The dual function geometry investigated includes a cavity on the suction side of the vane placed at the location of the geometric throat, and injection mass flow from a Coanda actuator placed at the upstream side of the cavity blowing downstream and into the cavity. With no injection, the primary core flow passes over the cavity, resulting in an effective throat width that is similar to the original geometric throat width. When the fluidic actuation is turned on, the injection flow entrains the core flow into the cavity, expanding the flow, and increasing the effective throat width. Using two-dimensional, periodic, RANS CFD, a design of experiments was conducted to evaluate the effectiveness of the Coanda actuator to increase mass flow for varying cavity and injection geometries, while also evaluating the effectiveness of a blocking actuator to reduce mass flow. The optimum case showed the ability to increase the primary mass flow by 15% and decrease primary mass flow by 19.9%, with the effectiveness of the actuators being approximately two in both cases. This optimum geometry case was then experimentally tested in a small-scale single nozzle guide vane passage. The experimental results show that while the blocking actuator was able to reduce mass flow effectively, the Coanda actuator was not able to increase the mass flow as effectively as predicted. Explanations for this disparity between the CFD results and experimental results are discussed.