Effectiveness of an inlet flow turbulence control device to simulate flight fan noise in an anechoic chamber

1977 ◽  
Vol 62 (S1) ◽  
pp. S81-S81 ◽  
Author(s):  
R. P. Woodward ◽  
J. A. Wazyniak ◽  
L. M. Shaw ◽  
M. J. MacKinnon
Keyword(s):  
Control Device ◽  
Anechoic Chamber ◽  
Fan Noise ◽  
Inlet Flow ◽  
Turbulence Control ◽  
Flow Turbulence

scholarly journals Characteristics of an Anechoic Chamber for Fan Noise Testing

1977 ◽  
Author(s):  
J. A. Wazyniak ◽  
L. M. Shaw ◽  
J. D. Essary
Keyword(s):  
Mechanical Design ◽  
Full Scale ◽  
Anechoic Chamber ◽  
Nasa Lewis Research ◽  
Design Features ◽  
Fan Noise ◽  
Inlet Flow ◽  
Noise Characteristics ◽  
Scale Levels ◽  
Acoustic Evaluation

Acoustical and mechanical design features of NASA Lewis Research Center’s engine fan noise facility are described. Acoustic evaluation of the 1420-m (50,000-ft) chamber, which is lined with an array of stepped wedges, is described. Results from the evaluation in terms of cut-off frequency and non-anechoic areas near the walls are detailed. Fan models with 0.51-m (20-in.) diameters are electrically driven to 20,600 rpm in either the inlet mode (drawing air from the chamber) or exhaust mode (discharging air into the chamber) to facilitate study of both fore and aft fan noise. Inlet noise characteristics of the first fan tested, the JT8D Refan, are discussed and compared to full-scale levels. Turbulence properties of the inlet flow and acoustic results are compared with and without a turbulence reducing screen over the fan inlet.

The Influence of Transient Inlet Distortions on the Instability Inception of a Low-Pressure Compressor in a Turbofan Engine

2000 ◽  
Vol 123 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Dirk C. Leinhos ◽  
Norbert R. Schmid ◽  
Leonhard Fottner
Keyword(s):  
Total Pressure ◽  
Delta Wing ◽  
Stability Limit ◽  
Stability Control ◽  
Control Device ◽  
Inlet Flow ◽  
Stall Inception ◽  
Hypersonic Aircraft ◽  
Surge Margin ◽  
Power Spectral

While studies on compressor flow instabilities under the presence of inlet distortions have been carried out with steady distortions in the past, the investigation presented here focuses on the influence of transient inlet distortions as generated by variable geometry engine intakes of super- and hypersonic aircraft on the characteristic and the nature of the instability inception of a LPC. The flow patterns (total pressure distortion with a superimposed co- or counterrotating swirl) of the distortions are adopted from a hypersonic concept aircraft. A LARZAC 04 twin-spool turbofan was operated with transient inlet distortions, generated by a moving delta wing, and steady total pressure distortions starting close to the LPC’s stability limit until it stalled. High-frequency pressure signals are recorded at different engine power settings. Instabilities are investigated with regard to the inception process and the early detection of stall precursors for providing data for a future stability control device. It turned out that the transient distortion does not have an influence on the surge margin of the LPC compared to the steady distortion, but that it changes the nature of stall inception. The pressure traces are analyzed in the time and frequency domain and also with tools like Spatial FFT, Power Spectral Density, and Traveling Wave Energy. A Wavelet Transformation algorithm is applied as well. While in the case of clean inlet flow, the compressor exhibits different types of stall inception depending on the engine speed, stall is always initiated by spike-type disturbances under the presence of steady or transient distortions. Modal disturbances are present in the mid-speed range that do not grow into stall, but rather interact with the inlet flow and produce short length scale disturbances. The obtained early warning times prior to stall are adversely affected by transient distortions in some cases. The problem of appropriate thresholding becomes evident. The best warning times have been acquired using a statistical evaluation of the Wavelet coefficients, which might be promising to apply in a staged active control system. This system could include different phases of detection and actuation depending on the current precursor.

The Influence of the TCS on the Circumferential Mode Distribution in the Inlet of a Fanrig (UFFA)

2012 ◽  
Author(s):  
Wolfram Köhler
Keyword(s):  
Control Device ◽  
Mode Analysis ◽  
Test Bed ◽  
Turbulence Control ◽  
Turbulence Structures ◽  
Mode Detection ◽  
Significant Difference ◽  
Full Picture ◽  
Rotor Stator Interaction ◽  
Static Conditions

Sophisticated noise testing of an aero engine fan on a static indoor test bed requires special arrangements to produce reliable data. One of these items used to improve the measured data quality is the TCS (turbulence control screen) (also called ICD, inlet control device). The TCS reduces the disturbances in the inflow resulting from the static conditions. In this way the results are comparable to flight tests with a more uniform inflow. The effects of the TCS with regards to turbulence structures in general are well studied. To get the full picture of the acoustic behaviour of the TCS the mode generation needs to be investigated and understood. This paper gives an overview of the inlet mode analysis performed for the UFFA (Universal Fan Facility for Acoustics). As expected the noise characteristic shows a significant difference especially upstream of the fan whether measurements were carried out with or without TCS. To get a better understanding of what is happening, the circumferential mode distribution in the inlet was measured with a CMD (circumferential mode detection) ring and the measurements were analysed with an algorithm based on the information published by the NLR (National Aerospace Laboratory of the Netherlands). The results show, that the inflow has a considerable influence on the spinning modes caused by the rotor-stator interaction (RSI) described by Tyler-Sofrin as well as on the rotor-alone noise. The circumferential modes generated by the rotor-stator interaction are significantly reduced by an unsteady nonuniform inflow while the rotor self noise is increased through turbulence-rotor interaction.

scholarly journals Cyclostationary Analysis of Fan Noise Influenced by an Inflow Control Device

AIAA Journal ◽  
2021 ◽  
pp. 1-12
Author(s):  
Larisa Grizewski ◽  
Maximilian Behn ◽  
Stefan Funke ◽  
Henri A. Siller
Keyword(s):  
Control Device ◽  
Fan Noise ◽  
Inflow Control Device

The Influence of Transient Inlet Distortions on the Instability Inception of a Low Pressure Compressor in a Turbofan Engine

2000 ◽  
Author(s):  
Dirk C. Leinhos ◽  
Norbert R. Schmid ◽  
Leonhard Fottner
Keyword(s):  
Total Pressure ◽  
Delta Wing ◽  
Stability Limit ◽  
Travelling Wave ◽  
Stability Control ◽  
Control Device ◽  
Inlet Flow ◽  
Stall Inception ◽  
Surge Margin ◽  
Power Spectral

While studies on compressor flow instabilities under the presence of inlet distortions have been carried out with steady distortions in the past, the investigation presented here focuses on the influence of transient inlet distortions as generated by variable geometry engine intakes of super- and hypersonic aircrafts on the characteristic and the nature of the instability inception of a LPC. The flow patterns (total pressure distortion with a superimposed co- or counter-rotating swirl) of the distortions are adopted from a hypersonic concept aircraft. A LARZAC 04 twin-spool turbofan was operated with transient inlet distortions, generated by a moving delta-wing, and steady total pressure distortions starting close to the LPC’s stability limit until it stalled. High frequency pressure signals are recorded at different engine power settings. Instabilities are investigated with regard to the inception process and the early detection of stall precursors for providing data for a future stability control device. It turned out that the transient distortion does not have an influence on the surge margin of the LPC compared to the steady distortion, but that it changes the nature of stall inception. The pressure traces are analysed in the time and frequency domain and also with tools like Spatial FFT, Power Spectral Density and Travelling Wave Energy. A Wavelet Transformation algorithm is applied as well. While in the case of clean inlet flow the compressor exhibits different types of stall inception depending on the engine speed, stall is always initiated by spike-type disturbances under the presence of steady or transient distortions though modal disturbances are present in the mid speed range that do not grow into stall, but rather interact with the inlet flow and produce short lengthscale disturbances. The obtained early warning times prior to stall are adversely affected by transient distortions in some cases. The problem of appropriate threshholding becomes evident. The best warning times have been acquired using a statistical evaluation of the Wavelet coefficients which might be promising to apply in a staged active control system which could include different phases of detection and actuation depending on the current precursor.

Sign in / Sign up

Export Citation Format

Share Document