Session: 01-18 Inlets, Nozzles, Mixers and Nacelles III

Paper Number: 129341

129341 - Effect of Gerlach Cross-Section on S-Duct Inlet Performance in High Subsonic Flow 

S-duct diffusers are employed in inlet of aircraft with embedded or offset engine for directing oncoming air into the propulsion system. The external configuration of the flight vehicle and the placement of internal components of aircraft drive the design and geometry of the S-duct diffuser. The characteristic design features of the S-duct are entrance cross-section shape, two or more bends, diffusion ratio, axial length, longitudinal curvature, cross-section transition, and lateral offset.  The flow in the S-duct diffuser is complex and depends strongly on these configurations and geometric parameters. The bend and diffusion causes transverse and axial pressure gradient, respectively, which results in flow separation downstream of the bends. The aerodynamic performance of S-duct diffuser is typically evaluated using longitudinal static pressure recovery, total pressure losses at the exit plane, called Aerodynamic Interface plane (AIP), circumferential and radial total pressure distortion, and swirl at the AIP. Pressure losses are detrimental to the performance of an aircraft engine. Distortion and swirl impose additional unsteady loading on the front stages of compression systems and reduce engine operational capacity and stability margins. The overall goal of the present study was to evaluate the high-speed performance of S-duct diffuser by varying configuration and geometric parameters (e.g. entrance cross-section shape, offset to length ratio, and area ratio). The flow separation downstream of bends is a major source of losses in an S-duct diffuser. It was hypothesized in literature that Gerlach re-shaping of cross-section at the bends may reduce the transverse pressure gradient and mitigate or eliminate separation. This paper aims to document the internal performance evaluation of an S-duct diffuser with Gerlach cross-section re-shaping of a baseline S-duct.  The generic baseline test article was a rectangular-entrance duct transitioning to a circular exit, a configuration typical of single-engine air vehicles. The important geometric parameters were exit-to-entrance area ratio of 1.57, the offset to length ratio of 0.37, and exit diameter of 101 mm. The intake ducts were manufactured in high-density plastic using SLA 3D printing. The performance of the intake was evaluated at Ma = 0.80 by measuring the longitudinal static pressure distribution, exit total pressure and three-dimensional (3D) velocity at the AIP. The measurements were used to evaluate and compare the aerodynamic performance of the S-duct variants. The geometries and flow conditions were also simulated using computational fluid dynamics and validated using experimental performance metrics. This work will contribute to the development of a database for the performance of S-duct inlets and for predicting the performance of aero-engines and air vehicles at high-subsonic flight conditions.

Presenting Author: Asad Asghar Royal Military College of Canada

Presenting Author Biography: Asad Asghar is a Research Associate and Adjunct Associate Professor at the Royal Military College of Canada in the Department of Mechanical and Aerospace Engineering. He teaches thermo-fluid courses and conducts research in the aeronautical engineering field. His research interest and publications are in supersonic and subsonic aerodynamics, flow control, wind tunnel testing, propulsion, aero-engine component testing, inlets, compressors, fans, and turbine. He has published research papers in ASME and AIAA journals and conferences and presented papers in CASI conferences. Asghar holds a B.Sc. in Mechanical Engineering. He holds a M.Sc. in Aerospace Engineering and a Ph.D. in Mechanical and Aerospace engineering from the University of Notre Dame.

Authors:

Benjamin D. Frosst Royal Military College of Canada
Asad Asghar Royal Military College of Canada
William D. E. Allan Royal Military College of Canada
Robert A. Stowe Valcartier Research Centre, Defence Research and Development Canada
Rogerio Pimentel Valcartier Research Centre, Defence Research and Development Canada
Grant Ingram Department of Engineering, Durham University
Timothy Orchard Department of Engineering, Durham University