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Research Papers: Gas Turbines: Turbomachinery

Entrance Aspect Ratio Effect on S-Duct Inlet Performance at High-Subsonic Flow

[+] Author and Article Information
Asad Asghar, William D. E. Allan

Department of Mechanical & Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada

Robert A. Stowe

Weapons Systems Section,
Defence Research and Development Canada,
Québec, QC G3J 1X5, Canada

Derrick Alexander

LR Martec Limited,
Halifax, NS B3J 3J8, Canada

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 23, 2016; final manuscript received September 16, 2016; published online January 4, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(5), 052602 (Jan 04, 2017) (8 pages) Paper No: GTP-16-1270; doi: 10.1115/1.4035206 History: Received June 23, 2016; Revised September 16, 2016

This paper reports the internal performance evaluation of S-duct diffusers with different entrance aspect ratios as part of a parametric investigation of a generic S-duct inlet. The generic S-duct diffusers studied had a rectangular entrance (aspect ratios of 1.5 and 2.0) transitioning S-duct diffuser in high-subsonic (Mach number > 0.8) flow. The test section was manufactured using rapid prototyping to facilitate the parametric investigation of the geometry. Streamwise static pressure and exit-plane total pressure were measured in a test-rig using surface pressure taps and a five-probe rotating rake, respectively. The baseline and a variant were simulated through computational fluid dynamics (CFD). The investigation indicated the presence of streamwise and circumferential pressure gradients leading to a three-dimensional flow in the S-duct diffuser and to distortion at the exit plane. The static pressure recovery increased for the diffuser with the higher aspect ratio. Total pressure losses and circumferential and radial distortions at the exit plane were higher than that of the podded nacelle type of inlet. An increase in the total pressure recovery was observed for the increase in the aspect ratio for the baseline area ratio (1.57) S-ducts, but without a clear trend for the other area ratio (1.8) ducts. The work represents the development of a database on the performance of a particular type of generic inlet. This database will be useful for predicting the performance of aero-engines and air vehicles in high-subsonic flight.

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Figures

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Fig. 1

Main parameters of an S-duct diffuser

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Fig. 2

Schematic of an S-duct inlet test-rig in a transonic wind tunnel

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Fig. 3

Schematic of an S-duct diffuser test section without a bellmouth

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Fig. 4

Five-probe total pressure rake

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Fig. 5

A cross-section view of the total pressure probe tip

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Fig. 6

Schematic of a longitudinal cross section of an S-duct diffuser test-rig and data acquisition system

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Fig. 7

Axial static pressure recovery along two circumferential locations for the baseline and AS = 2 S-duct diffusers

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Fig. 8

Computed axial Mach number and total pressure in the baseline S-duct diffuser: (a) Mach number distribution and (b) total pressure distribution

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Fig. 9

Axial static pressure recovery for Mach 0.80, AR = 1.8 S-ducts with AS = 1.5 and 2

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Fig. 10

Axial static pressure recovery for Mach 0.85, AR = 1.8 S-ducts with AS = 1.5 and 2

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Fig. 11

Total pressure ratio for S-duct diffusers at AIP: (a) experiment (baseline, AS = 1.5), (b) computation (baseline, AS = 1.5), (c) experiment (AS = 2), and (d) computation (AS = 2)

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Fig. 12

Computed streamlines and formation of separation bubble for a baseline S-duct diffuser

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Fig. 13

Total pressure ratio for an S-duct diffuser at AIP (Mach 0.8): (a) AR = 1.8, AS = 1.5 and (b) AR = 1.8, AS = 2

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