Nonaxisymmetric Stator Design for Boundary Layer Ingesting Fans

Gunn, E. J.; Hall, Cesare A.

doi:10.1115/1.4043343

Cited by 17 publications

(4 citation statements)

References 14 publications

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“…On the other hand, the influence of inlet distortion has always been an extensive subject of research due to its detrimental effects on the stall margin [22,23]. With the current trend in the Boundary Layer Ingestion technology to improve the propulsive efficiency, the aerodynamic and aeroelastic response of the fan to inlet distortion has been received an increasing attention [24][25][26][27]. If blade shapes are assumed to be identical, the flow field subject to a circumferential inlet distortion can be computed using a single-passage solution with the current stateof-the-art based on the Fourier method [28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

Phan

2021

Journal of Engineering for Gas Turbines and Power

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Accurate and efficient predictions of the steady and unsteady flow responses due to the blade-to-blade variation as well as due to the non-axisymmetric inlet distortion have been continually pursued. Computation of two problems concurrently has been rarely done in the past partly because of the need to perform whole annulus bladerow simulations, despite the advances in the current state-of-the-art methods with the phase-shift single passage simulations. The current work attempts to deal with this challenge by developing a new computational approach based on the principle of the multiscale method in the framework of a commercial solver (CFX). The methodology formulation relies on summation of the constituent source terms, each of which corresponds to a particular flow perturbation. The source term element corresponding to the blade-to-blade variation effect is linearly superimposed as in the classical Influence Coefficient Method. The unsteady flow field around a blade at any time instant depends only on its relative position to all its neighbouring blades, so that the influences of an arbitrarily mis-staggered bladerow can be computed efficiently. In addition, the source term arisen due to the inlet distortion is calculated based on the spatial Fourier transform. A key enabler is that the source terms can be pre-computed using a small set of identical blade passages. The source term is then propagated to different spatial and temporal locations ... Please find the completed abstract below.

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Section: Introductionmentioning

confidence: 99%

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

Phan

2021

Journal of Engineering for Gas Turbines and Power

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“…However, while the BLI fan layout brings aerodynamic advantages, it also introduces a specific type of spatially nonuniform inflow condition known as BLI inlet distortion. This distortion significantly reduces the fan’s aerodynamic performances (Gunn and Hall, 2014; Gunn and Hall, 2019), consequently undermining the potential aerodynamic benefits of the aircraft. In addition, the distortion intensity will vary with flight conditions due to the variable amount of boundary layer ingested by the fan (Hall et al , 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, as the BLI fan operates from near choke to near stall point, the loss variations of the rotor blade passages at different annulus locations present complex and diverse characteristics. Further, the diverse loss variation trends could be affected by multiple predominant flow features in BLI inflow, including a reduction in axial velocity due to ingesting low-momentum boundary layer fluid, swirl induced by pressure gradients in circumferential direction and streamtube contraction caused by flow redistribution (Gunn and Hall, 2014; Gunn and Hall, 2019). These flow features are highly coupled, making it extremely hard to identify the influence of each flow feature on the loss.…”

Section: Introductionmentioning

confidence: 99%

A data-driven flow loss prediction model for the blade hub region of a boundary layer ingestion fan rotor

Shi,

Lu,

Song

et al. 2023

HFF

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Purpose In a boundary layer ingestion (BLI) propulsion system, the fan operates continuously under distorted inflow conditions, leading to an increment of aerodynamic loss and in turn impacting the potential fuel burn reduction of the aircraft. Usually, in the preliminary design stage of a BLI propulsion system, it is essential to assess the impact of fuselage boundary layer fluids on fan aerodynamic performances under various flight conditions. However, the hub region flow loss is one of the major loss sources in a fan and would greatly influence the fan performances. Moreover, the inflow distortion also results in a complex and highly nonlinear mapping relation between loss and local physical parameters. It will diminish the prediction accuracy of the commonly used low-fidelity computational approaches which often incorporate traditional physics-based loss models, reducing the reliability of these approaches in evaluating fan performances. Meanwhile, the high-fidelity full-annulus unsteady Reynolds-averaged Navier–Stokes (URANS) approach, even though it can give rather accurate loss predictions, is extremely time-consuming. This study aims to develop a fast and accurate hub loss prediction method for a BLI fan under distorted inflow conditions. Design/methodology/approach This paper develops a data-driven hub loss prediction method for a BLI fan under distorted inflows. To improve the prediction accuracy and applicability, physical understandings of hub flow features are integrated into the modeling process. Then, the key physical parameters related to flow loss are screened by conducting a sensitivity analysis of influencing parameters. Next, a quasi-steady assumption of flow is made to generate a training sample database, reducing the computational time by acquiring one single sample from the highly time-consuming full-annulus URANS approach to a cost-efficient single-blade-passage approach. Finally, a radial basis function neural network is used to establish a surrogate model that correlates the input parameters and the output loss. Findings The data-driven hub loss model shows higher prediction accuracy than the traditional physics-based loss models. It can accurately capture the circumferentially and radially nonuniform variation trends of the losses and the associated absolute magnitudes in a BLI fan under different blade load, inlet distortion intensity and rotating speed conditions. Compared with the high-fidelity full-annulus URANS results, the averaged relative prediction errors of the data-driven hub loss model are kept less than 10%. Originality/value The originality of this paper lies in developing a new method for predicting flow loss in a BLI fan rotor blade hub region. This method offers higher prediction accuracy than the traditional loss models and lower computational time cost than the full-annulus URANS approach, which could realize fast evaluations of fan aerodynamic performances and provide technical support for designing high-performance BLI fans.

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“…In order to reduce the adverse impact of BLI distorted inflow on the fan aerodynamic performance, an effective fan blade design strategy that aims to reduce the additional loss in the BLI fan is necessary. The research work conducted on blade design has demonstrated that reducing the flow separation loss in the BLI fan stator is probably a good way to improve the fan efficiency effectively [19]. In this situation, it is essential to find a good way to suppress the flow separations in the stator to reduce the additional loss and further improve the aerodynamic performance of the BLI fan.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigations of a Non-Uniform Stator Dihedral Design Strategy for a Boundary Layer Ingestion (BLI) Fan

Pan

Shi

et al. 2022

Energies

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A distributed propulsion system has the advantage of saving 5–15% fuel burn through ingesting the fuselage boundary layer of an aircraft by fan or compressor. However, due to boundary layer ingestion (BLI), the fan stage will continuously operate under serious inlet distortion. This will lead to a circumferentially non-uniform flow separation distribution on the stator blade suction surface along the annulus, which significantly decreases the fan’s adiabatic efficiency. To solve this problem, a non-uniform stator dihedral design strategy has been developed to explore its potential of improving BLI fan performance. First, the stator full-annulus blade passages were divided into blade dihedral design regions and baseline design regions on the basis of the additional aerodynamic loss distributions caused by BLI inlet distortion. Then, to find the appropriate dihedral design parameters, the full-annulus BLI fan was discretized into several portions according to the rotor blade number and the dihedral design parameter investigations for dihedral depth and dihedral angle were conducted at the portion with the largest inflow distortion through a single-blade-passage computational model. The optimal combinational dihedral design parameter (dihedral depth 0.3, dihedral angle 6 deg) was applied to the blade passages with notable flow loss which were mainly located in the annulus positions from −120 to 60 degrees suffering from inlet distortion, while the blades in the low-loss annulus locations were unchanged. In this way, a non-uniform stator dihedral design scheme was achieved. In the end, the effectiveness of the non-uniform stator dihedral design was validated by analyzing the internal flow fields of the BLI fan. The results show that the stator dihedral design in distorted regions can increase the inlet axial velocity and reduce the aerodynamic load near the blade trailing edge, which are beneficial for suppressing the flow separations and reducing aerodynamic loss. Specifically, compared with the baseline design, the non-uniform stator dihedral design has achieved a reduction of aerodynamic loss of about 7.7%. The fan stage has presented an improvement of adiabatic efficiency of about 0.48% at the redesigned point without sacrificing the total pressure ratio. In the entire operating range, the redesigned fan has also shown a higher adiabatic efficiency than the baseline design with no reduction of the total pressure ratio, which provides a probable guideline for future BLI distortion-tolerant fan design.

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Nonaxisymmetric Stator Design for Boundary Layer Ingesting Fans

Cited by 17 publications

References 14 publications

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

A data-driven flow loss prediction model for the blade hub region of a boundary layer ingestion fan rotor

Numerical Investigations of a Non-Uniform Stator Dihedral Design Strategy for a Boundary Layer Ingestion (BLI) Fan

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