Investigation of Trailing-edge Blowing on Airfoils for Turbomachinery Broadband Noise Reduction PDF Download
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Author: Julian Winkler
Publisher:
ISBN: 9783844003505
Category :
Languages : en
Pages : 228
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Book Description
Author: Julian Winkler
Publisher:
ISBN: 9783844003505
Category :
Languages : en
Pages : 228
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Book Description
Author: J. M. Brookfield
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 14
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Book Description
Author: Terry D. Scharton
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 0
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721146284
Category :
Languages : en
Pages : 134
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Book Description
A wind tunnel test was conducted in the NASA Langley Transonic Dynamics Tunnel (TDT) on a six percent thick slightly cambered elliptical circulation control airfoil with both upper and lower surface blowing capability. Parametric evaluations of jet slot heights and Coanda surface shapes were conducted at momentum coefficients (Cm) from 0.0 to 0.12. Test data were acquired at Mach numbers of 0.3, 0.5, 0.7, 0.8, and 0.84 at Reynolds numbers per foot of 2.43 x 105 to 1.05 x 106. For a transonic condition, (Mach = 0.8 at alpha = 3 degrees), it was generally found the smaller slot and larger Coanda surface combination was overall more effective than other slot/Coanda surface combinations. Lower surface blowing was not as effective as the upper surface blowing over the same range of momentum coefficients. No appreciable Coanda surface, slot height, or slot blowing position preference was indicated transonically with the dual slot blowing. Alexander, Michael G. and Anders, Scott G. and Johnson, Stuart K. and Florance, Jennifer P. and Keller, Donald F. Langley Research Center WU 23-066-50-AE
Author: Gustave W. Schwartz
Publisher:
ISBN:
Category :
Languages : en
Pages : 90
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Author: Marvin Raymond LaFontaine
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Author: Jules B. Dods (Jr.)
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 145
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Book Description
The investigation reported herein consists of three phases: (1) an experimental investigation of a thin airfoil with blowing over a trailing-edge flap; (2) a comparison of the results of the experimental investigation with the results of other similar investigations; and (3) a theoretical study of the relationships among the air-flow and power parameters for the general blowing case.
Author: Bayindir Huseyin Saracoglu
Publisher:
ISBN:
Category : Aerospace engineering
Languages : en
Pages : 101
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Book Description
The desire for high performance and low fuel consumption aero-engines has been pushing the limits of the turbomachinery and leading cutting-edge engine designs to fulfill the demand. The number of stages is reduced to achieve the same pressure ratios over lighter turbines. The extreme expansion requirements result in transonic-supersonic flow fields. Transonic and supersonic turbines are exposed to the shock waves that appear at the trailing edge of the airfoils, generating substantial efficiency deduction due to the interaction with the boundary layer. Furthermore, pressure fluctuations created by the shocks result in unsteady forcing on downstream components and eventually cause high cycle fatigue. Component failure may lead reduced service life and further damage on the engine. A novel proposal to control the resulting fish tail shock waves consists on, pulsating coolant blowing through the trailing edge of the airfoils. The changes in the base region topology and fish tail shock wave were numerically investigated for a wide range of purge flow at simplified blunt and circular trailing edge geometries. An optimum purge rate which increases the base pressure and significantly reduces the trailing edge shock wave intensity was found. The effects of pulsating base pressure on the shock properties and the base region was investigated in detail to understand the mechanisms driving the flow field under unsteady bleed. A linear cascade representative of modern turbine bladings was specifically designed and constructed. The test matrix comprised four Mach numbers, from subsonic to supersonic regimes (0.8, 0.95, 1.1 and 1.2) together with two engine representative Reynolds numbers (4 and 6 million) at various blowing rates. The blade loading, the downstream pressure distributions and the unsteady wall temperature measurements allowed understanding the effects on each leg of the shock structure. Minimum shock intensities were achieved using pulsating cooling. A substantial increase in base pressure and significant reduction in trailing edge loss were observed for low coolant blowing rate. Analysis of the high frequency Schlieren pictures revealed the modulation of the shock waves with the coolant pulsation. The Strouhal number of the vortex shedding was analyzed for all of the conditions. Finally, the statistical analyses of the results showed that the effects of the state of cooling and free stream conditions were statistically significant on the flow properties.
Author: Abhishek Jain
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
AIRFOIL self-noise consists of five major sources. One of these identified sources is turbulent boundary layer -- trailing edge (TBL-TE) noise, which is an important source of rotor and wind turbine broadband noise, and the focus of this thesis. Trailing edge noise is the result of unsteady flow interacting with the trailing edge of an airfoil or other sharp edged flow surface. The presence of the sharp trailing edge scatters the sound generated by the turbulent eddies very efficiently, especially for sources in the immediate vicinity of the edge. There is a need for accurate and computationally efficient methods to calculate the turbulent boundary layer trailing-edge (TBL-TE) noise that are not reliant on empirical data. The majority of the current semi-empirical techniques are based on measurements from symmetric NACA airfoil sections (i.e. NACA 0012). These techniques are generally not coupled with CFD solvers to obtain turbulent boundary layer data that provides pertinent parameters used in the acoustic calculations. Some methods exist that incorporate CFD solutions like Large Eddy simulations (LES) into their noise prediction algorithms. But these are prohibitively expensive and impractical for routine use. The method described in this paper is a first principles approach that aims to predict the TBL-TE noise using computational aeroacoustic (CAA) techniques without resorting to empiricism.The prediction of trailing edge noise requires an accurate calculation of the boundary layer fluctuations in the vicinity of the trailing edge. Scales in the computational domain ranging from the small turbulent boundary layer scales to those of the long-range noise propagation need to be resolved. These data can be obtained using simulation techniques like Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES). However such simulations for complete helicopters or wind turbine rotors are impractical given today's computational resources. Also, DNS becomes unrealistic for the propagation of the acoustic signal to distant observers. The method described here overcomes these limitations by using a hybrid CAA approach coupled with a flow solver based on the non-linear disturbance equations (NLDE). The overall problem is separated into component problems with the NLDE equations applied over a relatively small noise generating region i.e. approximately the last 10% of the chord or less. This makes the solution more computationally efficient than LES for the full airfoil or rotor and enables the use of the most computationally efficient methods in the required regions. The proposed method is advantageous to helicopter and wind turbine manufacturers as it provides a tool for the prediction of rotor broadband noise at the design stage. This can also be used as a tool to reduce noise through the analysis of appropriate noise reduction devices.
