Fan Flow Field in an Installed Variable Pitch Fan Operating in Reverse Thrust for a Range of Aircraft Landing Speeds

Rajendran, David John; Pachidis, Vassilios

doi:10.1115/1.4044686

Cited by 10 publications

(17 citation statements)

References 13 publications

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“…Statistical measures of convergence that compare the standard deviations of different parameters of interest over fixed iteration intervals are defined to determine the stopping convergence criteria, specified as <0.5% variation over iteration bands. Further details about the individual component module development, domain discretization and flow field solution schematics of the integrated airframe-engine model to obtain the reverse thrust flow field are discussed in the work on the installed fan flow field by the authors [6].…”

Section: Figure 1: Components Of Integrated Airframe-engine Model [6]mentioning

confidence: 99%

“…The turned back reverse stream, on which the fan work has been done, flows through the OGV, where it loses its momentum, and re-joins the reverse stream from the bypass nozzle exit. Further details about the general reverse thrust flow field and the evolution of the fan flow field at different landing speeds and operating conditions are discussed in [6].…”

Section: General Installed Reverse Thrust Flow Fieldmentioning

confidence: 99%

“…All the previous studies explored the reverse flow behavior in uninstalled isolated static conditions or in limited forward flow conditions to characterize the reverse flow fan. The understanding of VPF in reverse thrust was extended in a recent study by the authors, by providing insight into the evolution of the actual installed reverse thrust fan flow field during the entire aircraft landing run from 140 knots to 20 knots, using an integrated airframe-engine model [6].…”

Section: Introductionmentioning

confidence: 99%

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Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

Rajendran

Pachidis

2021

Journal of Turbomachinery

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The flow distortion at core engine entry for a Variable Pitch Fan (VPF) in reverse thrust mode is described from a realistic flowfield obtained using an integrated airframe-engine-VPF research model. 3D RANS solutions are generated for the complete aircraft landing run from 140 to 20 knots at different VPF settings. The internal reverse thrust flowfield is characterized by nozzle lip separation, pylon wake and recirculation of flow turned back from the VPF. A portion of the reverse flow turns 180° with separation at the splitter edge to feed the core engine. The core feed flow exhibits circumferential and radial non-uniformities that depend on the reverse flow development at different landing speeds. The temporal dependence of the distorted flow features is also explored by an URANS analysis. Total pressure and swirl angle distortion descriptors, and total pressure loss are described for the core feed flow at different VPF settings and landing speeds. It is observed that the radial intensity of total pressure distortion is critical to core engine operation, while the circumferential intensity is within acceptable limits. Therefore, the baseline sharp splitter edge is replaced by two larger rounded splitter edges of radii, ∼0.1x and ∼0.2x times the core duct height. This was found to reduce the radial intensity of total pressure distortion to acceptable levels. The description of the installed core feed flow distortion, as in this study, is necessary to ascertain stable core engine operation, which powers the VPF in reverse thrust mode.

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Section: Figure 1: Components Of Integrated Airframe-engine Model [6]mentioning

confidence: 99%

Section: General Installed Reverse Thrust Flow Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

Rajendran

Pachidis

2021

Journal of Turbomachinery

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“…Further details of the VPF design and the components of the integrated research model are described in Ref. (Bentley, 2018;Rajendran and Pachidis, 2019).…”

Section: Integrated Research Modelmentioning

confidence: 99%

Development of a Research Model to Study the Operability of a Variable Pitch Fan Aero Engine In Reverse Thrust

Rajendran¹,

Aguirre²,

Tunstall³

et al. 2020

Proceedings of Global Power &Amp; Propulsion Society

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A rationale for the level of model fidelity required to provide the most representative flow field information to ascertain the feasibility of using a Variable Pitch Fan (VPF) in a modern high bypass ratio aero engine to generate reverse thrust is described in this paper. This is done by comparing the 3D RANS flow field solution for a newly developed reverse flow VPF design from two research models: i) isolated engine model in which the bypass duct, guide vanes, splitter and VPF are wrapped in an axisymmetric nacelle and placed in a generic far-field domain and b) integrated model in which the engine is installed to an airframe in landing configuration through a pylon and placed in a far-field domain bound by a rolling runway. The flow field solution obtained at an aircraft landing speed of 80 knots indicates that even though both models can predict the general flow patterns, there are substantial differences in parameters such as the amount of reverse stream, circumferential distribution of flow properties and flow development downstream of the engine. These differences impact the levels of reverse thrust generated, flow distortion entering the core engine and resultant airframe forces. This study makes the case that it is necessary to use an integrated model that includes a full engine nacelle installed on an airframe, to answer design questions for engineering the VPF system to generate reverse thrust.

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“…NASA experimental campaigns demonstrated reverse thrust as a percentage of gross take-off thrust of 53% for Stage 51B (Kovich & Steinke, 1976), 66% for Stage 51 (Moore, et al, 1976), 53% for the Q-Fan (Schaefer, et al, 1977), and 43% for the QCSEE scale fan (Giffin, et al, 1977) exceeding the estimated requirement on landing for the QCSEE program of 35%. These thrust values were measured at engine-static conditions, which excluded the significant reduction in fan flow with representative bypass duct inlet distortion, observed in rig tests by Reemsnyder & Sagerser (1979) and in flight-configuration URANS simulations by Rajendran & Pachidis (2019).…”

Section: Introductionmentioning

confidence: 99%

Variable Pitch Fan Aerodynamic Design for Reverse Thrust Operation

Williams¹,

Hall²,

Wilson³

2022

Proceedings of Global Power &Amp; Propulsion Society

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Variable pitch low pressure ratio fans could enable higher propulsive efficiency and eliminate the need for heavy thrust reversers. In this paper, the effects of the fan rotor design on reverse thrust capability have been explored by varying key parameters of NASA’s Advanced Ducted Propulsor (ADP) while maintaining cruise point performance. Reverse thrust performance has been assessed using RANS single passage CFD of the variable pitch fan system with an extended domain. This computational approach has been validated using NASA Stage 51B, an experimental variable pitch fan test case. Predicted total pressure and total pressure ratios for this case were found to agree with test data within experimental error, except where large tip region separations occurred at high incidence. Applying individual variations to rotor pitch-to-chord, radial loading distribution, and chordwise camber distribution generated changes to rotor incidence, blockage, and peak surface Mach numbers in reverse operation. An increase in gross reverse thrust of up to 8% was achieved through reductions in rotor pitch-to-chord due to improved loading and lower shock Mach numbers. Controlling section camber distributions was used to move the rotor shock downstream and was found to increase reverse thrust by up to 3%. Increasing rotor loading at the mid span relative to the tip resulted in high tip incidence and a 50% reduction in gross reverse thrust across all rotor speeds. This suggests that tip loaded designs are required for high levels of reverse thrust.

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Fan Flow Field in an Installed Variable Pitch Fan Operating in Reverse Thrust for a Range of Aircraft Landing Speeds

Cited by 10 publications

References 13 publications

Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

Development of a Research Model to Study the Operability of a Variable Pitch Fan Aero Engine In Reverse Thrust

Variable Pitch Fan Aerodynamic Design for Reverse Thrust Operation

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