Fan Response to Inlet Swirl Distortions Produced by Boundary Layer Ingesting Aircraft Configurations

Frohnapfel, Dustin J.; O’Brien, Walter F.

doi:10.2514/6.2015-3804

Cited by 14 publications

(3 citation statements)

References 10 publications

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“…The mean axial velocity profiles presented in Fig. 10 display a series of features related to structures introduced to the flow by the presence of the StreamVane, since they are not present in the design profile or in clean inlet results presented by Frohnapfel et al [22,23]. These features indicate total pressure losses, as previously described by the total-to-static pressure ratios calculated using the following relationship in Ref.…”

Section: Resultsmentioning

confidence: 62%

Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

Guimarães

Lowe

O’Brien

2018

Journal of Engineering for Gas Turbines and Power

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The future of aviation relies on the integration of airframe and propulsion systems to improve aerodynamic performance and efficiency of aircraft, bringing design challenges, such as the ingestion of nonuniform flows by turbofan engines. In this work, we describe the behavior of a complex distorted inflow in a full-scale engine rig. The distortion, as in engines on a hybrid wing body (HWB) type of aircraft, is generated by a 21-in diameter StreamVane, an array of vanes that produce prescribed secondary flow distributions. Data are acquired using stereoscopic particle image velocimetry (PIV) at three measurement planes along the inlet of the research engine (Reynolds number of 2.4 × 106). A vortex dynamics-based model, named StreamFlow, is used to predict the mean secondary flow development based on the experimental data. The mean velocity profiles show that, as flow develops axially, the vortex present in the profile migrates clockwise, opposite to the rotation of the fan, and toward the spinner of the engine. The turbulent stresses indicate that the center of the vortex meanders around a preferred location, which tightens as flow gets closer to the fan, yielding a smaller radius mean vortex near the fan. Signature features of the distortion device are observed in the velocity gradients, showing the wakes generated by the distortion screen vanes in the flow. The results obtained shed light onto the aerodynamics of swirling flows representative of distorted turbofan inlets, while further advancing the understanding of the complex vane technology presented herein for advanced ground testing.

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Section: Resultsmentioning

confidence: 62%

Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

Guimarães

Lowe

O’Brien

2018

Journal of Engineering for Gas Turbines and Power

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“…The study of fan stability under the effect of specific profiles mimicking realistic environments, such as those caused by boundary layer ingestion [5,6], flow separation in the inlet duct [7] or sudden manoeuvres of the aircraft [8], is an understudied part of the engine/airframe interaction and an active area of research [9]. Experimental and numerical investigation by Hah et al [10] have shown that the inlet total pressure distortion increases aerodynamic losses when a strong unsteady interaction between the passage shock and the blade boundary layer develops.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Stability Analysis of a Generic Fan With Distorted Inflow Using Passage-Spectral Method

Romera

Corral

2021

Journal of Turbomachinery

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The dependence of the aerodynamic stability of fan blades with the nodal diameter and amplitude of the inlet perturbations is studied. The analysis is conducted using a block-wise spatial Fourier decomposition of reduced-passages to reconstruct the full-annulus solution. The explicit spatial Fourier approximation is exploited to characterize the relevance of each nodal diameter of the inlet perturbation in the fan stall process and study the nonlinear stability in a harmonic by harmonic basis. This approximation allows studying the contribution to stall of each circumferential mode separately. The methodology has been assessed for the NASA rotor 67. The maximum amplitude of total pressure distortion at which the compressor becomes unstable and triggers a stall process has been mapped. It has been proven that despite the complexity of a screen-induced total pressure distortion the only relevant parameter for the nonlinear stability of the fan is the most unstable nodal diameter. Full-annulus simulations have been conducted to assess the accuracy of the simplified nonlinear stability limit. It is concluded that performing a nonlinear simulation with the proper single harmonic perturbation is enough to assess fan stability. It is shown that for the NASA rotor 67 running at the nominal speed the most unstable nodal diameter is the first. This study not only shows a reduction in computational time to assess nonlinear fan stability by a factor of seven but also creates an efficient methodology for understanding the nonlinear instability of fans due to inlet distortion profiles.

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“…Several investigations of the effects of swirl distortion have been performed, both computationally [10][11][12], and experimentally. These experimental efforts have employed pressure probes in ducts [13,14] or cascades [15], and, more recently, particle image velocimetry [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Vortical flow development in round ducts across scales for engine inlet applications

2019

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Turbofan engine performance depends highly on the characteristics and conditions of the inlet flow. Swirl distortions, caused by non-uniformities in flows arising from boundary layer or ground/fuselage vortex ingestion are of concern and need to be fully understood to guarantee efficiency and safety of propulsion systems. To investigate a fundamental single-vortex distortion development in a duct at different Reynolds numbers, a StreamVane distortion generating device was designed and experimentally analyzed in a small-scale low-speed wind tunnel (Re D 500 × 10 3 ) and in a full-scale engine testing rig (Re D 3 × 10 6 ). Stereoscopic particle image velocimetry was used to measure the three-component velocity fields at discrete measurement planes downstream of the distortion device. Results show that the secondary flow is generated and develops very similarly in both scales, and is mostly driven by two-dimensional (2D) vortex dynamics. Induced velocities arising from the proximity of the vortex to the duct wall causes the vortex center to convect circumferentially around the duct, in the same sense as the vortex rotation, as it travels downstream. Small-scale turbulence results show small-scale instabilities related to the development of the vortex. This work shows that the development of this vane-generated, vortex-dominated flow is largely Reynolds number independent for the covered range, so that details of similar duct-bounded flows can be analyzed in depth in small-scale experiments, decreasing development efforts and cost. arXiv:1808.07273v1 [physics.flu-dyn]

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Fan Response to Inlet Swirl Distortions Produced by Boundary Layer Ingesting Aircraft Configurations

Cited by 14 publications

References 10 publications

Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

Nonlinear Stability Analysis of a Generic Fan With Distorted Inflow Using Passage-Spectral Method

Vortical flow development in round ducts across scales for engine inlet applications

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