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Research Papers

Minimizing Inlet Distortion for Hybrid Wing Body Aircraft

[+] Author and Article Information
Meng-Sing Liou

Aeropropulsion Division, NASA Glenn Research Center, Cleveland, OH 44135meng-sing.liou@nasa.gov

Byung Joon Lee

NASA Postdoctoral Program, NASA Glenn Research Center, Cleveland, OH 44135mdo.bjlee@gmail.com

For example, a uniformly low Pt (high loss) profile will give a very low DPCPavg. Hence, it is prudent that total pressure recovery must be included for evaluation of a design.

J. Turbomach. 134(3), 031020 (Jul 15, 2011) (10 pages) doi:10.1115/1.4003072 History: Received July 06, 2010; Revised August 02, 2010; Published July 15, 2011; Online July 15, 2011

A study of boundary-layer-ingesting flow in an upper-mounted offset inlet in NASA’s hybrid wing body transport concept for achieving environmental and performance requirements has been carried out. This study aims specifically at minimizing flow distortion stemming from the ingested low-momentum fluid to the level acceptable to the operation of fan blades. In this paper, we will focus on using a discrete adjoint method to arrive at an optimized wall geometry, which is parametrically represented by design variables, for transonic turbulent flows described by 3D Navier–Stokes equations supplemented with κ-ω-SST turbulence model. Of special interest herein is the flow physics resulting from optimization, revealing the intricate connections to the remarkable reduction in flow distortion and total pressure losses at the engine face. It is discovered that the counter-rotating vortex pair commonly seen in an S-inlet is eliminated by energizing both the core and boundary layer fluids through the change of wall shape by a series of peaks and valleys. Their exact forms, magnitudes, and locations, unknown a priori, are determined by the discrete adjoint method. The optimal shape, moreover, still holds similar level of superior performance at off-design conditions. The result may suggest a possible paradigm shift in flow control concept, away from disruptive penalty ridden devices, by properly conditioning and guiding the flow.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

N+2B concept configuration

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Figure 2

Schematic of overset grid

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Figure 3

Typical overset grid system for BLI inlet, each color denoting an individual block grid

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Figure 4

NURBS surface modeling

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Figure 5

Representative B-spline patch used to parameterize the surface geometry for optimizing BLI inlet

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Figure 6

Flow chart of the adjoint optimization process

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Figure 7

Schematic of the baseline BLI inlet under study, top and side views. All dimensions are in inches.

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Figure 8

Design history, showing convergence of objective function DPCP and total pressure recovery, and improvement of both over the baseline design

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Figure 9

“Oil flow” pattern of the original (top) and optimal (bottom) inlets, superimposed on pressure contours

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Figure 10

Comparison of Mach number distributions at various cross sections, with superimposed cross flow streamlines

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Figure 11

The optimized shape of bottom wall, modified in −1.5≤x/D2≤0.5. Note: Not to scale, the change in coordinate is O(10−2).

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Figure 12

A top view of wall shape changes in the optimized design; colors denote the levels of changes, red for peaks and blue for valleys

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Figure 13

Streamlines and boundary layer growth on symmetry plane, together with Mach number contours

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Figure 14

Magnified view of streamlines near inlet throat on symmetry plane (Y=0)

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Figure 15

Magnified view of streamlines near inlet throat on plane Y/D=0.5, revealing a valley following a mild peak and preceding a major one

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Figure 16

X-component velocity profiles at various x-locations on the plane Y/D=0.5, baseline inlet causes reverse flow

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Figure 17

Comparison of flow distortions at off-design conditions

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Figure 18

Comparison of total pressure recoveries at off-design conditions

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Figure 19

Streamlines and boundary layer growth on symmetry plane at an off-design condition, Pb/Pt,0=0.8417

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Figure 20

Comparison of Mach number distributions at various cross sections at an off-design condition, Pb/Pt,0=0.8417

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