Investigations on the Effect of Inflow Distortion on the Performance of a High Aspect Ratio, Low Speed Contra Rotating Fan Stage

Mistry, Chetan S.; Pradeep, A. M.

doi:10.1115/gt2013-94311

Cited by 11 publications

(8 citation statements)

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“…10,11 To obtain a deeper insight into the flow physics in CRAC, a large amount of work has been carried out on the effects of some major factors such as rotor stagger angle, pitch-chord ratio, inlet distortion, casing treatment, speed ratio of the two rotors, axial spacing between two rotors, etc. [12][13][14][15][16][17][18][19] Results showed that those factors have significant impacts on the performance of CRAC. So as to understand the tip clearance size effect on the overall performance and TLF, Gao et al 20 and Wang et al 21 have conducted steady numerical simulations on several tip clearance sizes for both rotors.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the unsteady flow behaviors in a counter-rotating axial compressor

Mao

Liu

2016

Proceedings of the Institution of Mechanical Engineers, Part A:

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Unsteady numerical simulations of a counter-rotating axial compressor are performed to investigate the unsteady effects of rotor-rotor interaction process and the tip flow unsteady behavior near the stall operating condition. The results show that potential effects from the rear rotor have a more pronounced influence on the front rotor. Because of the interaction between the two rotors and the unsteady flow behaviors, the strongest fluctuant regions are different for the two rotors. Additionally, the oscillation on the pressure side is generally much stronger than that on the suction side. Frequency analyses show that self-unsteadiness occurs with the frequency of 0.76 blade passing frequency due to the impingement of the tip leakage flow on the pressure side near leading edge of the adjacent blade. An interesting phenomenon, i.e., the emergence of a local high pressure spot, is observed in the tip region. As a whole, it is concluded that there are two key effects of the emergence of the local high pressure zone in the tip region: (a) more leading edge spillage of tip leakage flow and increasing the risk to trigger stall; and (b) a decrease in blockage associated with doubleleakage of tip clearance flow within the influenced region of the local high pressure zone.

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Section: Introductionmentioning

confidence: 99%

Numerical investigation of the unsteady flow behaviors in a counter-rotating axial compressor

Mao

Liu

2016

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…Flow field measurements and simulations have shown that distortion leads to a large-scale flow redistribution upstream of a compressor rotor, leading to non-uniform velocity and swirl angles at its leading edge, [20][21][22][23][24]. In many of these studies the rotor is found to operate at high incidence in localised regions of the annulus, with a flow coefficient below the critical clean-flow value, while the machine as a whole remains stable.…”

Section: Introductionmentioning

confidence: 99%

Stall Inception in a Boundary Layer Ingesting Fan

Perović

Hall

Gunn³

2019

Journal of Turbomachinery

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Jet engines with boundary layer ingestion (BLI) could offer significant reductions in aircraft fuel burn compared with podded turbofans. However, the engine fans must run continuously with severe inlet distortion, which is known to reduce stability. In this paper, an experimental study has been completed on a low-speed rig fan operating with a BLI-type inlet distortion. Unsteady casing static pressure measurements have been made at multiple locations during stall events. Steady-state, full-annulus area traverses have also been performed at rotor inlet and exit at a near-stall operating point. The reduction in stability caused by BLI is found to be small. It is found that with BLI the fan can operate stably despite the presence of localized regions where the rotor operating point lies beyond the stability boundary measured in clean flow. With the BLI-type distortion applied, the measured rotor incidence varies around the annulus due to nonuniform upstream velocity and swirl. The measured amplitude of unsteady casing pressure fluctuations just prior to stall is found to correlate with the circumferential variation of rotor incidence, suggesting that rotor incidence is a key variable affecting the creation and growth of flow disturbances. In regions of high incidence, disturbances resembling local flow separations are initiated. However, in regions of low or negative incidence, any disturbances decay rapidly. Full rotating stall with BLI occurs when high incidence regions are widespread enough to sustain disturbances which can propagate around the entire annulus.

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“…Other literature applicable to fan inlet distortion also looked at square waves. Mistry et al [4] carried out experiments on a contra-rotating rotor rig and analysed effects on aerodynamics and performance. Gunn et al [5] conducted experiments on a low speed fan stage and studied the effect on loss mechanisms.…”

Section: Inlet Distortionmentioning

confidence: 99%

Pathways to Improved Aerodynamic Design

Page¹,

Hield²,

Mantell³

et al. 2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

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Abstract. Large-scale unsteady graphical processor unit (GPU) based calculations are used to study the flow in realistic transonic fan geometries and shown to produce useful insights into the complex unsteady flow physics in systems of practical engineering relevance. Inlet flow distortion produces complex flow patterns which can significantly reduce stall margin. In order to design efficient, well targeted fan stabilizing technologies, it is essential to gain understanding into which specific features of distorted flow patterns are important in causing instability.In this paper, the use of large-scale, high-fidelity 3D unsteady Reynolds-Averaged Navier Stokes (URANS) calculations with sliding planes is shown to allow the isolation of a wide range of inlet distortion features and a high throughput of calculations is achieved. This facilitates a comprehensive investigation into stall margin loss and the observation of complex instability processes, which is in turn used to support the development of specialized design solutions. The costs of simulations and turnaround times are given. The potential for mixed fidelity simulations, in particular mixing one-dimensional low order models and large eddy type simulations to generate inlet conditions, is discussed. 7544Figure 1: Aerospace airframe and propulsion technology under development.

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Investigations on the Effect of Inflow Distortion on the Performance of a High Aspect Ratio, Low Speed Contra Rotating Fan Stage

Cited by 11 publications

References 0 publications

Numerical investigation of the unsteady flow behaviors in a counter-rotating axial compressor

Numerical investigation of the unsteady flow behaviors in a counter-rotating axial compressor

Stall Inception in a Boundary Layer Ingesting Fan

Pathways to Improved Aerodynamic Design

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