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Research Papers: Gas Turbines: Turbomachinery

Effects of Flow Distortions as They Occur in S-Duct Inlets on the Performance and Stability of a Jet Engine

[+] Author and Article Information
Rudolf. P. M. Rademakers

Institute of Jet Propulsion,
University of the German Federal
Armed Forces Munich,
Neubiberg 85577, Germany
e-mail: Ruud.Rademakers@unibw.de

Stefan Bindl, Reinhard Niehuis

Institute of Jet Propulsion,
University of the German Federal
Armed Forces Munich,
Neubiberg 85577, Germany

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2015; final manuscript received July 30, 2015; published online September 7, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(2), 022605 (Sep 07, 2015) (10 pages) Paper No: GTP-15-1290; doi: 10.1115/1.4031305 History: Received July 14, 2015; Revised July 30, 2015

One of the research areas at the Institute of Jet Propulsion focuses on the design and optimization of s-shaped engine inlet configurations. The distortion being evoked within such inlet ducts should be limited to ensure an optimal performance, stability, and durability of the engine's compression system. Computational fluid dynamics (CFD) play a major role in the design process of bent engine inlet ducts. The flow within such ducts can be computed, distortion patterns can be visualized, and related distortion coefficients are easily calculated. The impact of a distortion on flow phenomena within the compressor system can, however, only be computed with major computational efforts and thus the quality of an s-duct design in development is usually assessed by analyzing the evoked distortion with suitable distortion coefficients without a true knowledge of the duct's influence on the downstream propulsion system. The influence of inlet distortion on both the performance and stability of the Larzac 04 jet engine was parameterized during experimental investigations at the engine test bed of the Institute of Jet Propulsion. Both pressure and swirl distortion patterns as they typically occur in s-duct inlet configurations were reproduced with distortion generators. Pressure distortion patterns were generated using seven types of distortion screens. The intensity of the distortion varies with the mesh size of the screen whereas the extension of the distortion is defined by the dimensions of the screen in radial and circumferential direction. A typical counter rotating twin-swirl was generated with a delta-wing installed upstream of the compressor system. First, the development of flow distortion was analyzed for several engine operating points (EOPs). A linear relation between the total pressure loss in the engine inlet and the EOPs was found. Second, the flow within the compressor system with an inlet distortion was analyzed and unsteady flow phenomena were detected for severe inlet distortions. Finally, the effect of both pressure and swirl distortion on the performance and stability of the test vehicle was parameterized. A loss in engine performance with increasing inlet distortion is observable. The limiting inlet distortion with respect to engine stability was found; and moreover, it was shown that pressure distortion has a stronger influence on the stability of the compressor system compared to a counter rotating twin-swirl distortion. The presented parameterization was essential for the s-duct design, which was under development for an experimental setup with the Larzac 04 jet engine.

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Figures

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Fig. 1

Larzac 04 jet engine

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Fig. 2

Overview of the experimental setup

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Fig. 3

Schematic representation of all distortion screens

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Fig. 4

Measurement rake with eight five-hole probes

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Fig. 5

Positioning of five-hole probes in the AIP

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Fig. 6

Distortion configurations within the LPC performance map

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Fig. 7

Pressure distortion patterns of all test cases at NLc = 90%

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Fig. 8

Relation of pressure loss ΔpT,AIP at different EOPs

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Fig. 9

Dynamic wall static pressure (p2) 10 mm upstream of the first LPC stage: (a) case 4 at NLc = 76%, (b) case 4 at NLc = 90%, (c) case 7 at NLc = 76%, and (d) case 7 at NLc = 88.3%

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Fig. 10

SMLPC as a function of (a) ΔpT,AIP, (b) CDImean, and (c) DC60mean

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Fig. 11

pT(1,21) as a function of (a) ΔpT,AIP, (b) CDImean, and (c)DC60mean

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Fig. 12

SFC as a function of CDImean

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Fig. 13

SMLPC as a function of CDImean

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Fig. 14

ΠLPC as a function of CDImean

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