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Research Papers: Gas Turbines: Aircraft Engine

Low Frequency Distortion in Civil Aero-engine Intake

[+] Author and Article Information
Mauro Carnevale

Centre of Vibration Engineering,
Department of Mechanical Engineering,
Imperial College London,
London SW7 2BX, UK
e-mail: m.carnevale@imperial.ac.uk

Feng Wang

Centre of Vibration Engineering,
Department of Mechanical Engineering,
Imperial College London,
London SW7 2BX, UK
e-mail: feng.wang207@imperial.ac.uk

Luca di Mare

Centre of Vibration Engineering,
Department of Mechanical Engineering,
Imperial College London,
London SW7 2BX, UK
e-mail: l.di.mare@imperial.ac.uk

1Corresponding author.

Contributed by the Aircraft Engine Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 1, 2016; final manuscript received August 2, 2016; published online October 18, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(4), 041203 (Oct 18, 2016) (12 pages) Paper No: GTP-16-1297; doi: 10.1115/1.4034600 History: Received July 01, 2016; Revised August 02, 2016

The main role of the intake is to provide a sufficient mass flow to the engine face and a sufficient flow homogeneity to the fan. Intake-fan interaction off design represents a critical issue in the design process because intake lines are set very early during the aircraft optimization. The offdesign operation of an aero-engine, strictly related to the intake flow field, can be mainly related to two different conditions. When the plane is in near ground position, vorticity can be ingested by the fan due to crosswind incidence. During the flight, distortions occur due to incidence. In these conditions, the windward lip is subjected to high acceleration followed by strong adverse pressure gradients, high streamline curvature, and cohabitation of incompressible and transonic flow around the lip. All these features increase the risk of lip stall in flight at incidence or in crosswind near ground operation and increase the level of forcing seen by the fan blades because of the interaction with nonuniform flow from the intake. This work deals with the study of two sources of distortions: ground vortex ingestion and flight at high incidence conditions. A test case representative of a current installation clearance from the ground has been investigated and the experimental data available in open literature validated the computational fluid dynamics (CFD) calculations. An intake, representative of a realistic civil aero-engine configuration flying at high incidence, has been investigated in powered and aspirated configurations. Distortion distributions have been characterized in terms of total loss distributions in space and in time. The beneficial effect of the presence of fan in terms of distortion control has been demonstrated. The mutual effect between fan and incoming distortion from the intake has been assessed in terms of modal force and distortion control. CFD has been validated by means of comparisons between numerical results and experimental data which have been provided. Waves predicted by CFD have been compared with an actuator disk approach prediction. The linear behavior of the lower disturbance frequency coming from distortion and the waves reflected by the fan has been demonstrated.

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References

Figures

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Fig. 1

Intake flow features

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Fig. 2

Actuator disk approach Ref. [18]

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Fig. 4

Grid independence for near ground test case

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Fig. 7

Computational domains: (a) aspirated intake analysis, (b) steady LPC, (c) powered intake analysis, and (d) powered intake including the LPC

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Fig. 3

Near ground model intake Ref. [7]

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Fig. 8

Intake lower lip Cp distribution for different grid levels

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Fig. 5

Distortion coefficient and nondimensional circulation in crosswind

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Fig. 6

Nondimensional circulation at different yaw incidence angles

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Fig. 11

DC60 prediction at different incidence conditions

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Fig. 12

Local Mach distribution lower lip for αref with k−ω

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Fig. 9

Log-law profiles near intakes walls

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Fig. 10

Separation at different angles of incidence and total pressure contour plots on fan face at different angles of incidence

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Fig. 13

Turbulence viscosity prediction: k−ω and Spalart Allmaras

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Fig. 15

(a) Legend, (b) static pressure profile at 80% span blade, and (c) total pressure profile at 80% span blade

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Fig. 16

Pressure ratio map in the distorted passage in powered intake

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Fig. 14

DC60 prediction at different incidence conditions including powered with OGV stage

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Fig. 17

Comparison of perturbed static pressure between aspirated (a) and powered intake (b)

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Fig. 18

Perturbation ratio (powered/aspirated)

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Fig. 19

Harmonic content of low frequency distortion: ground vortex condition and high incidence

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Fig. 20

Distortion static pressure signal for aspirated and aspirated test case

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Fig. 21

60% radius: Four engine order prediction from CFD and actuator disk: (I) aspirated form CFD—(II) reflected wave from actuator disk—(III) difference (I–II–IV) powered form CFD

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Fig. 22

90% radius: Four engine order prediction from CFD and actuator disk: (I) aspirated form CFD—(II) reflected wave from actuator disk—(III) difference (I–II–IV) powered form CFD

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Fig. 23

Reflection coefficient for fan in near ground condition and flight at incidence condition

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