Design of a Distortion-Tolerant Fan for a Boundary-Layer Ingesting Embedded Engine Application

Cousins, William T.; Voytovych, Dmytro; Tillman, Gregory; Gray, E. Z.

doi:10.2514/6.2017-5042

Cited by 26 publications

(20 citation statements)

References 8 publications

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“…However, designing the rotor of a BLI system is a challenging task as the fan encounters severe aerodynamic and mechanical loads. Cousins [18] designed and tested a distortion-tolerant fan accounting for the highly coupled interaction between the inlet and the rotor. Frohnapfel et al [19] have largely decoupled the total pressure and swirl distortion and measured the rotors response to each of these distortions.…”

Section: Introductionmentioning

confidence: 99%

Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

Vadlamani

Cao

Watson

et al. 2019

Journal of Turbomachinery

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In this paper, we investigate the coupled interaction between a new short intake design with a modern fan in a high-bypass ratio civil engine, specifically under the off-design condition of high incidence. The interaction is expected to be much more significant than that on a conventional intake. The performance of both the intake-alone and rotor-alone configurations are examined under isolation. Subsequently, a comprehensive understanding on the two-way interaction between intake and fan is presented. This includes the effect of fan on intake angles of attack (AoA) tolerance (FoI) and the effect of circumferential and radial flow distortion induced by the intake on the fan performance (IoF). In the FoI scenario, the rotor effectively redistributes the mass flow at the fan-face. The AoA tolerance of the short-intake design has increased by ≈4 deg when compared with the intake-alone configuration. Dynamic nature of distortion due to shock unsteadiness has been quantified. ST plots and power spectral density (PSD) of pressure fluctuations show the existence of a spectral gap between the shock unsteadiness and blade passing, with almost an order of magnitude difference in the corresponding frequencies. In the IoF scenario, both the “large” (O(360 deg)) and “small” scale distortion (O(10–60 deg)) induced by the intake results in a non-uniform inflow to the rotor. Sector analysis reveals a substantial variation in the local operating condition of the fan as opposed to its steady characteristic. Streamline curvature, upwash, and wake thickening are identified to be the three key factors affecting the fan performance. These underlying mechanisms are discussed in detail to provide further insights into the physical understanding of the fan-intake interaction. In addition to the shock-induced separation on the intake lip, the current study shows that shorter intakes are much more prone to the upwash effect at higher AoA. Insufficient flow straightening along the engine axis is reconfirmed to be one of the limiting factors for the short-intake design.

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Section: Introductionmentioning

confidence: 99%

Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

Vadlamani

Cao

Watson

et al. 2019

Journal of Turbomachinery

View full text Add to dashboard Cite

show abstract

“…Based on system studies 1-3 which showed a potential reduction in fuel burn for a hybrid wing body vehicle employing a boundary layer ingesting (BLI) propulsion system, a propulsor was designed [4][5][6] and tested [7][8][9][10] to demonstrate the feasibility of BLI technology. For these benefits to be realized, the BLI propulsor would need to be able to operate in a highly-distorted flow environment while maintaining acceptably high levels of performance and operability.…”

Section: Introductionmentioning

confidence: 99%

Performance Calculations for a Boundary-Layer-Ingesting Fan Stage from Sparse Measurements

Hirt

Wolter

Arend

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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A test of the Boundary Layer Ingesting Inlet/Distortion Tolerant Fan was completed in NASA Glenn's 8-by 6-Foot Supersonic Wind Tunnel. Inlet and fan performance were measured by surveys using a set of rotating rake arrays upstream and downstream of the fan stage. Surveys were conducted along the 100% speed line as well as a constant exit corrected flow line passing through the aerodynamic design point. These surveys represented only a small fraction of the data collected during the test. For other operating points, data was recorded as "snapshots" without rotating the rakes which resulted in a sparser set of recorded data. This paper will discuss an approach to the analysis of these additional, lower-measurement-density data points to expand our coverage of the fan map. Several techniques will be used to enhance snapshot data and compare with survey data to assess the quality of the approach.

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“…[3] One of the main research objectives of the BLI 2 DTF Project was to develop and apply aeromechanics analysis tools to predict the effects of unique BLI distortion on "designed to be distortion-tolerant" fan system. [4,5] Traditional single blade modeling techniques are incapable of accurately modeling the entire rotor blade system due to complex dynamic loading behaviors and vibrations in distorted flow conditions. Thus, the present aeromechanics analysis on BLI 2 DTF fan rotor system had four specific objectives: (1) establish a model based approach that enables a highfidelity full-rotor aeromechanics analysis capability for performance, safety, and computational efficiency in design analysis of a fan rotor system subjected to a distorted inlet flow, (2) complete forced response analyses to determine dynamic stresses in DTF fan blade due to continual operation in a distorted flow resulting from BLI using cyclic symmetry modeling techniques, (3) assess the concerns of fatigue problem using Goodman Diagram approach by examining predicted stress values regarding the HCF behavior due to blade static and vibration dynamic stresses, and (4) provide guidance on the strain measurement by determining optimal strain gauge locations on the blades towards a cost-effective experimental test measurement from overall and/or directional strain characteristics predicted due to a loading condition aforementioned.…”

Section: Figure 1: Conceptual Aircraft Design and Boundary Layer Ingementioning

confidence: 99%

Cyclic Symmetry Finite Element Forced Response Analysis of a Distortion Tolerant Fan with Boundary Layer Ingestion

Min

Reddy

Bakhle

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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Accurate prediction of the blade vibration stress is required to determine overall durability of fan blade design under Boundary Layer Ingestion (BLI) distorted flow environments. Traditional single blade modeling technique is incapable of representing accurate modeling for the entire rotor blade system subject to complex dynamic loading behaviors and vibrations in distorted flow conditions. A particular objective of our work was to develop a high-fidelity full-rotor aeromechanics analysis capability for a system subjected to a distorted inlet flow by applying cyclic symmetry finite element modeling methodology. This reduction modeling method allows computationally very efficient analysis using a small periodic section of the full rotor blade system. Experimental testing by the use of the 8-foot by 6-foot Supersonic Wind Tunnel Test facility at NASA Glenn Research Center was also carried out for the system designated as the Boundary Layer Ingesting Inlet/Distortion-Tolerant Fan (BLI 2 DTF) technology development. The results obtained from the present numerical modeling technique were evaluated with those of the wind tunnel experimental test, toward establishing a computationally efficient aeromechanics analysis modeling tool facilitating for analyses of the full rotor blade systems subjected to a distorted inlet flow conditions. Fairly good correlations were achieved hence our computational modeling techniques were fully demonstrated. The analysis result showed that the safety margin requirement set in the BLI 2 DTF fan blade design provided a sufficient margin with respect to the operating speed range.

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Design of a Distortion-Tolerant Fan for a Boundary-Layer Ingesting Embedded Engine Application

Cited by 26 publications

References 8 publications

Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

Performance Calculations for a Boundary-Layer-Ingesting Fan Stage from Sparse Measurements

Cyclic Symmetry Finite Element Forced Response Analysis of a Distortion Tolerant Fan with Boundary Layer Ingestion

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