Stereoscopic PIV Measurements of Swirl Distortion on a Full-Scale Turbofan Engine Inlet

Nelson, Michael A.; Lowe, K. Todd; O’Brien, Walter F.; Hoopes, Kevin

doi:10.2514/6.2014-0533

Cited by 22 publications

(13 citation statements)

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“…Although no previous S-PIV work has been successfully performed at the full AIP of a convoluted air intake, some previous studies are pertinent to this work [17][18][19][20] . Kalpakli et al 17 performed cross flow, time resolved S-PIV measurements at the exit plane of curved pipes.…”

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confidence: 99%

“…Previous experiments for cylindrical ducts with water 18 , proved the feasibility of S-PIV techniques to measure flows with large out-of-plane velocity components. Doorne et al 18 and Nelson et al 19 highlighted the complexities of performing S-PIV through cylindrical ducts and quantified some of the underlying challenges associated with it. These tests showed that the curved cylindrical walls of the test section cause additional optical distortions that impose uncertainties onto the mapping functions especially close to the boundaries.…”

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confidence: 99%

“…These errors can be accounted for through a mis-registration correction algorithm. The importance of laser light management was also highlighted to avoid excessive secondary light scattering and reflections by the cylindrical walls which increase the measurement noise by up to 60% 19,20 . Within the context of flow distortion, Guimarães et al.…”

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Flow Distortion Measurements in Convoluted Aeroengine Intakes

et al. 2016

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The unsteady flowfields generated by convoluted aero-engine intakes are sources of instabilities that can compromise the performance of the downstream turbomachinery. Hence, there is a need for synchronous, high-spatial resolution measurements that will allow a greater understanding of the aerodynamics. In this work, Stereo Particle Image Velocimetry (S-PIV) is used in a new application to characterize the distorted flow at the outlet of complex intake. A suite of measurements and analyses for two S-duct configurations across a range of inlet Mach numbers are presented. The work demonstrates the feasibility of using SPIV techniques for determining the flow field at the exit of convoluted intakes with a higher spatial resolution than typical pressure measurements. Analysis of the distortion descriptors quantifies the dependency upon the S-duct configuration and highlights that the more high-offset duct generates greater levels of swirl distortion relative to the low-offset configuration. Distortion maps show that the flow is highly unsteady with a characteristic switching of the swirling flow. The results provide a new dataset which shows that the conventional assessments based on time-averaged data substantially underestimates the swirl distortion level and that the less frequent distortion events give rise to more potentiallysignificant threats to the compression system. Nomenclature A = area

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Flow Distortion Measurements in Convoluted Aeroengine Intakes

et al. 2016

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“…This nonuniform flow developed in a straight connecting duct before being ingested by the turbofan. The StreamVane method has been previously proven to accurately generate specific swirl distortion for both wind tunnel [18] and turbofan engine [19][20][21] testing. To mitigate the risk of stalling/surging the fan compression system under the distorted flow conditions, the fan speed was limited to 65% design maximum, corresponding to an inlet mass flow rate of approximately 45 lbm/s (20 kg/s) and fan inlet Mach number of approximately 0.3.…”

Section: Experimental Methodsmentioning

confidence: 99%

Experimental Quantification of Fan Rotor Effects on Inlet Swirl Using Swirl Distortion Descriptors

Frohnapfel

Lowe

O’Brien

2018

Journal of Engineering for Gas Turbines and Power

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The prominence of highly integrated engine/airframe architectures in modern commercial aircraft design concepts has led to significant research efforts investigating the use of conventional turbofan engines in unconventional installations where severe inlet distortions can arise. In order to determine fan rotor capabilities for reducing or eliminating a complex inlet swirl distortion, an experimental investigation using a StreamVaneTM swirl distortion generator was conducted in a turbofan engine research platform. Three-dimensional (3D) flow data collected at two discrete planes surrounding the fan rotor indicated that the intensity of the swirl distortion was decreased by the fan rotor; however, substantial swirl distortion effects remained in the fan exit flow. Flow angle magnitudes and swirl intensity (SI) decreased by approximately 30–40% across the fan rotor, while the presence of large-scale features within the distortion profile was nearly eliminated. Secondary flow streamlines indicated that small-scale features of the distortion were less affected by the rotating component and remained coherent at the fan rotor outlet plane. These results led to the conclusion that swirl distortion survived interactions with the fan rotor, leading to off-design conditions cascading through downstream engine components.

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“…StreamVane has recently been developed to model complex inlet swirl distortions in operational turbofan engines. 8,9 A turbofan engine ground test investigation was conducted to demonstrate the response of the fan rotor to inlet swirl distortion generated by a custom StreamVane swirl distortion generator. 10 The peak flow angle magnitudes of swirl were reduced by approximately 30-40% across the fan rotor, and the fan rotor was incapable of completely eliminating the swirl distortion.…”

Section: Introductionmentioning

confidence: 99%

Effect of swirl on the performance and stability of transonic axial compressor

Zhang

2017

Proceedings of the Institution of Mechanical Engineers, Part A:

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To investigate the effect of twin swirl and bulk swirl on the performance and stability of a transonic axial compressor, a blade swirl generator was designed and simulated with a transonic single rotor using steady and unsteady numerical calculation methods. The bulk swirl intensity was adjusted by replacing the blades with different camber angles. The twin swirl intensity was decreased by reducing the blade number. The counter-rotating bulk swirl generated a significant drop in both the efficiency and stall margin, and resulted in an increase in the choked mass flow, and total pressure ratio. The co-rotating bulk swirl generated a decrease in the mass flow, total pressure ratio and stable operating range. The counter-rotating bulk swirl resulted in suction surface boundary layer separation beyond 50% of the span-wise height as well as more serious tip leakage blockage. The twin swirl resulted in a decrease in the total pressure ratio, maximum efficiency and stable operating range. The steady and unsteady numerical calculation results were consistent, though some differences were observed in the values. For the steady calculation, the maximum efficiency and choked mass flow decreased by 0.88% and 1.74%, respectively, and the mass flow at the stable boundary increased by 3.92% as compared to the uniform inlet flow at twin swirl intensity of 24°. During the unsteady calculation, the mass flow exhibited an increase of only 2.2% at the stable boundary. Under twin swirl and co-rotating bulk swirl and uniform inlet flow, the leading edge spillage of the tip leakage flow resulted in compressor instability. The counter-rotating bulk swirl changed the mechanism of instability. The characterisation of the swirl distortion presented a difference between the steady and unsteady calculations near the stable boundary. The unsteady calculation exhibited a lower mass flow at the stable boundary point and a higher total pressure ratio.

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Stereoscopic PIV Measurements of Swirl Distortion on a Full-Scale Turbofan Engine Inlet

Cited by 22 publications

References 8 publications

Flow Distortion Measurements in Convoluted Aeroengine Intakes

Flow Distortion Measurements in Convoluted Aeroengine Intakes

Experimental Quantification of Fan Rotor Effects on Inlet Swirl Using Swirl Distortion Descriptors

Effect of swirl on the performance and stability of transonic axial compressor

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