A global approach to turbomachinery flow control loss reduction using endwall suction and midspan vortex generator jet blowing

A Global Approach to Turbomachinery Flow Control: Loss Reduction using Endwall Suction and Midspan Vortex Generator Jet Blowing Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Matthew Jon Bloxham, M.S Graduate Program in Aeronautical and Astronautical Engineering The Ohio State University 2010 Dissertation Committee: Jeffrey P Bons, Advisor Jim Gregory Jen-Ping Chen Mohammad Samimy Copyright By Matthew Jon Bloxham 2010 Abstract A flow control scheme using endwall suction and vortex generator jet (VGJ) blowing was employed in an effort to reduce the turbine passage losses associated with the endwall flow field and midspan separation Unsteady midspan control at low Re had a significant impact on the wake area-average total pressure losses, decreasing the losses by 54% Initially, the focus of the endwall control was the horseshoe vortex system The addition of leading edge endwall suction resulted in an area-average total pressure loss reduction of 57% The minimal additional gains achieved with leading edge endwall suction showed that the horseshoe vortex was a secondary contributor to endwall loss production (primary contributor- passage vortex) A similar flow control strategy was then employed with an emphasis on passage vortex (PV) control During the design, a theoretical model was used that effectively predicted the trajectory of the passage vortex The model required inviscid results obtained from two-dimensional CFD It was used in the design of two flow control approaches, the removal and redirection approaches The emphasis of the removal approach was the direct application of flow control on the endwall below the passage vortex trajectory The redirection approach attempted to alter the trajectory of the PV by removing boundary layer fluid through judiciously placed suction holes Suction hole positions were chosen using a potential flow model that emphasized the alignment of the endwall flow field with inviscid streamlines Model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade comprised of the highly-loaded L1A blade profile ii Detailed wake total pressure losses were measured while matching the suction and VGJ massflow rates, for the removal and redirection approaches at ReCx=25000 and blowing ratio, B, of When compared with the no control results, the addition of steady VGJs and endwall suction reduced the wake losses by 69% (removal approach) and 68% (redirection approach) The majority of the total pressure loss reduction resulted from the steady spanwise VGJs, while the suction schemes provided modest additional reductions (