Effect of Inlet Distortion Features on Transonic Fan Rotor Stall

Page, James H.; Hield, P; Tucker, Paul G.

doi:10.1115/1.4040030

Cited by 22 publications

(10 citation statements)

References 25 publications

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“…The distortion events that are shown within this work are therefore in the frequency range of interest for the engine instabilities. However, the lower the frequency of the disturbances, the higher is the magnitude required to trigger stall inception [38]. Therefore, it is theorized that the shift towards a lower frequency bands observed with Profile A and Profile B at = 0° may be beneficial for the engine stability.…”

Section: Spectral Analysismentioning

confidence: 99%

The impact of inlet boundary layer thickness on the unsteady aerodynamics of S-duct intakes

Migliorini

Zachos

MacManus

2019

AIAA Propulsion and Energy 2019 Forum

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The need to reduce aero-engine emissions and direct operating costs is driving the civil aerospace sector towards considering more integrated propulsion systems. Many of the proposed novel aircraft architectures employ convoluted intakes for either the aero-engine or propulsion system. These intakes are characterized by unsteady distortion that can hinder the performance and operability of the propulsion system. This work assesses the impact of the inlet boundary layer on the unsteady aerodynamics of an S-duct intake using time-resolved particle image velocimetry at the aerodynamic interface plane. An increase in the boundary layer thickness at the intake inlet increases the flow unsteadiness on the swirl angle by up to 40% relative to the baseline case. The azimuthal orientation of the inlet boundary layer modifies the intensity and topology of the most frequent swirl distortion pattern. For a relatively thick inlet boundary layer, the reduction of the dominant frequencies associated with the unsteady swirl angle is postulated to be beneficial for the engine stability. Overall, this works gives guidelines for the integration between the intake and the engine across the range of potential inlet operating conditions.

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Section: Spectral Analysismentioning

confidence: 99%

The impact of inlet boundary layer thickness on the unsteady aerodynamics of S-duct intakes

Migliorini

Zachos

MacManus

2019

AIAA Propulsion and Energy 2019 Forum

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“…The simulations of Page et al [22] support this observation as a notable loss of stability margin was demonstrated when low momentum flow was ingested in the tip region of the fan.…”

mentioning

confidence: 80%

“…Cousins [21] states that the time which is taken for a distortion to convect from the leading edge to the throat of the rotor blade is important in defining the response of the compressor to distortion. However, a typical assumption which is made is that distortions which persists for a duration which is less than the equivalent time for 60° of the rotor revolution are expected to have a negligible impact on fan stability [22]. Similarly, for sufficiently slow variations in intake distortion, the response of the fan is primarily influenced by the spatial distribution of the steady-state flow distortion.…”

Section: B Flow Field Spectral Analysismentioning

confidence: 99%

Influence of Upstream Total Pressure Profiles on S-Duct Intake Flow Distortion

McLelland

MacManus

Zachos

et al. 2020

Journal of Propulsion and Power

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For some embedded engine arrangements, the nature of the inlet distortion is influenced by the boundary layer characteristics at the inlet plane of the intake. This research presents the first quantitative assessment on the influence of inlet boundary layer thickness and asymmetry on the swirl distortion at the exit of an S-shaped intake. Measurements of high spatial and temporal resolution have been acquired at the outlet plane of the S-duct using time-resolved particle image velocimetry. When boundary layer profiles typical of embedded engines are introduced, the characteristic secondary flows at the outlet plane are intensified. Overall, the peak swirl intensity increases by 40% for a boundary layer which is 7 times thicker than the reference case. The unsteady modes of the S-duct remain, although the dominant fluctuations in the flow arise at a frequency 50% lower. When the inlet boundary layer profile becomes asymmetric about the intake centerline the peak swirl events at the hub are reduced by up to 40%. At the tip the peak swirl intensity increases by 29%. The results demonstrate that the effects of inlet boundary layer thickness and asymmetry must be carefully considered as part of engine compatibility tests for complex intakes. Nomenclature ai(t) = Temporal coefficient for i th mode in Proper Orthogonal Decomposition [ms -1 ] Ain = S-duct inlet plane area [m 2 ] Aout = S-duct outlet plane area [m 2 ] Din = S-duct inlet plane diameter [m]

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“…Page et. al [4] calculated the stall inception process with different inlet distortions generated by curved intake ducts. The results provided evidence that the low momentum flow in the tip region leads to damaging instability.…”

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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Effect of Inlet Distortion Features on Transonic Fan Rotor Stall

Cited by 22 publications

References 25 publications

The impact of inlet boundary layer thickness on the unsteady aerodynamics of S-duct intakes

The impact of inlet boundary layer thickness on the unsteady aerodynamics of S-duct intakes

Influence of Upstream Total Pressure Profiles on S-Duct Intake Flow Distortion

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

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