Flow and Noise Characteristics of Airfoils With Application to Turbomachinery

Volume 3 ◽  
2004 ◽  
Author(s):  
S. Lee ◽  
H.-J. Kim ◽  
W.-S. Song ◽  
F. E. C. Culick ◽  
N. Fujisawa
Keyword(s):  
Finite Thickness ◽  
Suction Side ◽  
Scale Model ◽  
Frequency Noise ◽  
Pressure Side ◽  
Trailing Edge ◽  
Eddy Simulation ◽  
Noise Characteristics ◽  
Turbulent Vortex Shedding ◽  
Late Transition

The flow-fields around airfoils in a uniform flow under the generation of noise were numerically studied and compared with experimental data. The numerical simulation was carried out by a large-eddy simulation that employs a deductive dynamic model as a subgrid-scale model. The result for a symmetrical airfoil at small angle of attack α = 3°–6° indicates that the discrete or narrow-banded frequency noise is generated when the separated laminar flow reattaches near the trailing edge of the pressure side and a strong instability thereafter affects positive vortices shed near the trailing edge. This type of forced transition or late transition instabilities near the trailing edge of the pressure side, interacting with convected vortices in an attached T.B.L. on the suction side, can be found in many practical airfoils of impellers rotating at moderate speeds under design conditions. The sound spectra derived from the aero-acoustic computations of airfoils indicate a dipole nature of sound having a narrow-banded or discrete peak by laminar instability and turbulent vortex shedding from their trailing edges of finite thickness at a Strouhal frequency, a quadrupole sound by turbulent broadband boundary-layer noise, or a mixed mode depending on flow conditions near the T.E.

The Effect of Airfoil Shape on Trailing Edge Noise

2019 ◽  
Vol 27 (02) ◽  
pp. 1850020 ◽  
Author(s):  
Seongkyu Lee
Keyword(s):  
Boundary Layer ◽  
Noise Source ◽  
Source Region ◽  
Low Frequency ◽  
Suction Side ◽  
Frequency Noise ◽  
Pressure Side ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Naca0012 Airfoil

This paper investigates the effect of airfoil shape on trailing edge noise. The boundary layer profiles are obtained by XFOIL and the trailing edge noise is predicted by a TNO semi-empirical model. In order to investigate the noise source characteristics, the wall pressure spectrum is decomposed into three components. This decomposition helps in finding the dominant source region and the peak noise frequency for each airfoil. The method is validated for a NACA0012 airfoil, and then five additional wind turbine airfoils are examined: NACA0018, DU96-w-180, S809, S822 and S831. It is found that the dominant source region is around 40% of the boundary layer thickness for both the suction and pressure sides for a NACA0012 airfoil. As airfoil thickness and camber increase, the maximum source region moves slightly upward on the suction side. However, the effect of the airfoil shape on the maximum source region on the pressure side is negligible, except for the S831 airfoil, which exhibits an extension of the noise source region near the wall at high frequencies. As airfoil thickness and camber increase, low frequency noise is increased. However, a higher camber reduces low frequency noise on the pressure side. The maximum camber position is also found to be important and its rear position increases noise levels on the suction side.

Boundary Layer and Loss Analysis in a Film Cooled Vane

2001 ◽  
Author(s):  
Giovanna Barigozzi ◽  
Giuseppe Benzoni ◽  
Antonio Perdichizzi
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Suction Side ◽  
Wake Flow ◽  
Generation Process ◽  
Pressure Side ◽  
Wake Region ◽  
Trailing Edge ◽  
Loss Analysis ◽  
Coolant Injection

The paper reports on boundary layer and wake flow analysis in a fully covered, film cooled vane without trailing edge ejection. The investigation, carried out in a low speed wind tunnel for linear cascades, has been mainly focused on the loss generation process due to coolant injection. The investigated region includes the rear part of pressure and suction side boundary layers and the wake region, up to a chord length downstream of the trailing edge. All measurements have been performed at mid-span, air being used as coolant flow. The same measurements have been also performed on a solid blade cascade, i.e. without cooling holes. Boundary layer profiles, integral parameters together with mean and turbulent quantities are presented. It results that the showerhead promotes transition on the suction side, giving rise to a thicker boundary layer all over the surface. On the pressure side, the boundary layer remains laminar up to the trailing edge, as high acceleration prevents transition. The wake region seems not to be strongly altered by the coolant injection. Boundary layer profiles and downstream 5-hole probe traverses have been used to compute loss coefficient distributions all over the blade surface and in the downstream region. Coolant injection strongly increases the profile losses along the suction side, while a much smaller contribution from the pressure side has been found. These increases are mainly due to coolant injection in the vane front part.

Numerical Study of Heat Transfer in Novel Wavy Trailing Edge Design for Gas Turbine Airfoils

2019 ◽  
Author(s):  
Sarwesh Parbat ◽  
Li Yang ◽  
Minking Chyu ◽  
Sin Chien Siw ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Gas Turbine ◽  
Numerical Study ◽  
Turbine Blades ◽  
Suction Side ◽  
Inlet Temperature ◽  
Protective Film ◽  
Pressure Side ◽  
Trailing Edge

Abstract The strive to achieve increasingly higher efficiencies in gas turbine power generation has led to a continued rise in the turbine inlet temperature. As a result, novel cooling approaches for gas turbine blades are necessary to maintain them within the material’s thermal mechanical performance envelope. Various internal and external cooling technologies are used in different parts of the blade airfoil to provide the desired levels of cooling. Among the different regions of the blade profile, the trailing edge (TE) presents additional cooling challenges due to the thin cross section and high thermal loads. In this study, a new wavy geometry for the TE has been proposed and analyzed using steady state numerical simulations. The wavy TE structure resembled a sinusoidal wave running along the span of the blade. The troughs on both pressure side and suction side contained the coolant exit slots. As a result, consecutive coolant exit slots provided an alternating discharge between the suction side and the pressure side of the blade. Steady state conjugate heat transfer simulations were carried out using CFX solver for four coolant to mainstream mass flow ratios of 0.45%, 1%, 1.5% and 3%. The temperature distribution and film cooling effectiveness in the TE region were compared to two conventional geometries, pressure side cutback and centerline ejection which are widely used in vanes and blades for both land-based and aviation gas turbine engines. Unstructured mesh was generated for both fluid and solid domains and interfaces were defined between the two domains. For turbulence closer, SST-kω model was used. The wall y+ was maintained < 1 by using inflation layers at all the solid fluid interfaces. The numerical results depicted that the alternating discharge from the wavy TE was able to form protective film coverage on both the pressure and suction side of the blade. As a result, significant reduction in the TE metal was observed which was up to 14% lower in volume averaged temperature in the TE region when compared to the two baseline conventional configurations.

Laminar separation bubble development on an airfoil emitting tonal noise

2015 ◽  
Vol 780 ◽  
pp. 167-191 ◽  
Author(s):  
S. Pröbsting ◽  
S. Yarusevych
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Quantitative Description ◽  
Suction Side ◽  
Pressure Side ◽  
Laminar Separation Bubble ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Laminar Separation ◽  
Trailing Edge Noise

The subject of this experimental study is the feedback effects due to tonal noise emission in a laminar separation bubble (LSB) formed on the suction side of an airfoil in low Reynolds number flows. Experiments were performed on a NACA 0012 airfoil for a range of chord-based Reynolds numbers $0.65\times 10^{5}\leqslant \mathit{Re}_{c}\leqslant 4.5\times 10^{5}$ at angle of attack ${\it\alpha}=2^{\circ }$, where laminar boundary layer separation is encountered on both sides of the airfoil. Simultaneous time-resolved, two-component particle image velocimetry (PIV) measurements, unsteady surface pressure and far-field acoustic pressure measurements were employed to characterize flow development and acoustic emissions. Amplification of disturbances in separated shear layers on both the suction and pressure sides of the airfoil leads to shear layer roll-up and shedding of vortices from separation bubbles. When the vortices do not break up upstream of the trailing edge, the passage of these structures over the trailing edge generates tonal noise. Acoustic feedback between the trailing edge noise source and the upstream separation bubble narrows the frequency band of amplified disturbances, effectively locking onto a particular frequency. Acoustic excitation further results in notable changes to the overall separation bubble characteristics. Roll-up vortices forming on the pressure side, where the bubble is located closer to the trailing edge, are shown to define the characteristic frequency of pressure fluctuations, thereby affecting the disturbance spectrum on the suction side. However, when the bubble on the pressure side is suppressed via boundary layer tripping, a weaker feedback effect is also observed on the suction side. The results give a detailed quantitative description of the observed phenomenon and provide a new outlook on the role of coherent structures in separation bubble dynamics and trailing edge noise generation.

Numerical Simulation of Turbulent Flow Past a Serrated Airfoil

2011 ◽  
Author(s):  
Changhwa Han ◽  
Takeshi Omori ◽  
Takeo Kajishima
Keyword(s):  
Turbulent Flow ◽  
Pressure Fluctuations ◽  
Density Variation ◽  
Aerodynamic Noise ◽  
Experimental Investigations ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Eddy Simulation ◽  
Naca0012 Airfoil ◽  
Edge Side

Despite a lot of experimental investigations, the effect of airfoil serrations on the reduction of discrete frequency noise (DFN) is not fully understood. We apply the large-eddy simulation (LES) to the turbulent flow around the NACA0012 airfoil without angle of attack in a uniform stream. In this case, a major source of aerodynamic noise is quasi two-dimensional spanwise vortices, which take place near the trailing edge. We therefore investigate the effect of serration in the trailing edge side. The depth of the serration is 10% of chord length. To take into account the weak compressibility at low Mach number, we made a particular modification to the pressure equation. One equation dynamic model for the subgrid scale stress is used for LES. These techniques have originally been developed in our research group. The serration successfully reduced the pressure fluctuations on the surface of the airfoil near the trailing edge. The observed structure of the density variation suggests that this modification contributes to the reduction of sound source.

scholarly journals Effects of Unsteady Flow Interactions on the Performance of a Highly-Loaded Transonic Compressor Stage

2015 ◽  
Author(s):  
Chunill Hah
Keyword(s):  
Total Pressure ◽  
Suction Side ◽  
Pressure Side ◽  
Rotor Wake ◽  
Transonic Compressor ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compressor Design ◽  
Stator Blade ◽  
Total Temperature

The primary focus of this paper is to investigate the loss sources in an advanced GE transonic compressor design with high reaction and high stage loading. This advanced compressor has been investigated both experimentally and analytically in the past. The measured compressor efficiency is significantly lower than the efficiency calculated with various existing tools based on RANS and URANS. The general understanding is that some important flow physics in this modern compressor design are not represented in the current tools. To pinpoint the source of the efficiency miss, an advanced test with detailed flow traverse was performed for the front one and a half stage at the NASA Glenn Research Center. In the present paper, a Large Eddy Simulation (LES) is employed to determine whether a higher-fidelity simulation can pick up any additional flow physics that can explain past efficiency miss with RANS and URANS. The results from the Large Eddy Simulation were compared with the NASA test results and the GE interpretation of the test data. LES calculates lower total pressure and higher total temperature on the pressure side of the stator, resulting in large loss generation on the pressure side of the stator. On the other hand, existing tools based on the RANS and URANS do not calculate this high total temperature and low total pressure on the pressure side of the stator. The calculated loss through the stator from LES seems to match the measured data and the GE data interpretation. Detailed examination of the unsteady flow field from LES indicates that the accumulation of high loss near the pressure side of the stator is due to the interaction of the rotor wake with the stator blade. The strong rotor wake interacts quite differently with the pressure side of the stator than with the suction side of the stator blade. The concave curvature on the pressure side of the stator blade increases the mixing of the rotor wake with the pressure side boundary layer significantly. On the other hand, the convex curvature on the suction side of the stator blade decreases the mixing and the suction side blade boundary layer remains thin. The jet velocity in the rotor wake in the stator frame seems to magnify the curvature effect in addition to inviscid redistribution of wake fluid toward the pressure side of the blade.

Effect of Surface Roughness Location and Reynolds Number on Compressor Cascade Performance

2010 ◽  
Author(s):  
Seung Chul Back ◽  
Garth V. Hobson ◽  
Seung Jin Song ◽  
Knox T. Millsaps
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Trailing Edge ◽  
Blade Loading ◽  
Linear Compressor Cascade

An experimental investigation has been conducted to characterize the influence of surface roughness location and Reynolds number on compressor cascade performance. Flow field surveys have been conducted in a low-speed, linear compressor cascade. Pressure, velocity, and flow angles have been measured via a 5-hole probe, pitot probe, and pressure taps on the blades. In addition to the entirely smooth and entirely rough blade cases, blades with roughness covering the leading edge; pressure side; and 5%, 20%, 35%, 50%, and 100% of suction side from the leading edge have been studied. All of the tests have been done for Reynolds number ranging from 300,000 to 640,000.Cascade performance (i.e. blade loading, loss, and deviation) is more sensitive to roughness on the suction side than pressure side. Roughness near the trailing edge of suction side increases loss more than that near the leading edge. When the suction side roughness is located closer to the trailing edge, the deviation and loss increase more rapidly with Reynolds number. For a given roughness location, there exists a Reynolds number at which loss begins to visibly increase. Finally, increasing the area of rough suction surface from the leading edge reduces the Reynolds number at which the loss coefficient begins to increase.

The Development and Mechanisms of the High Pressure Turbine Vane Wake Vortex

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Dun Lin ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Vortex Shedding ◽  
Wave Interaction ◽  
Suction Side ◽  
Wake Vortex ◽  
Pressure Waves ◽  
Pressure Side ◽  
Eddy Simulation ◽  
Turbine Vane

The wake vortex is an important origin of unsteadiness and losses in turbines. In this paper, the development and underlying mechanisms of the shedding vortex of a high-pressure transonic turbine vane are studied and analyzed using the delayed detached eddy simulation (DDES) and proper orthogonal decomposition (POD). The goal is to understand the unsteadiness related to the wake vortex shedding and the wake evolution and mixing. Special attention is paid to the development of the wake vortex and the mechanisms behind the length characteristics. Interactions of the wake vortex with the shock wave and pressure waves are also discussed. First, the DDES simulation results are compared with published experimental data, Reynolds Averaged Navier-Stokes, and large eddy simulation (LES) simulations. Then, the development of the vane wake vortex, especially the different length characteristics from the cylinder vortex, is discussed. The reason of stronger pressure-side vortex shedding compared to suction-side vortex shedding is revealed. Wake-shock wave interaction and wake-pressure wave interaction are also investigated. The pressure waves are found to have a stronger effect than the shock wave on the spanwise motion and the dissipation of the wake vortex. An analysis of the losses through the turbine vane passage is carried out to evaluate the contributions of thermal and viscous irreversibilities. Losses analysis also confirms the strong interaction between the wake vortex and pressure waves. After that, POD study of the wake behavior was carried out. The results indicate that the shedding vortex is dominant in the unsteady flow. The phase relation between the pressure side wake vortex (PSVP) and the suction side wake vortex (SSVP) is confirmed.

Multi-Row Film Cooling Performances of a High Lift Blade and Vane

2012 ◽  
Author(s):  
S. Naik ◽  
J. Krueckels ◽  
M. Gritsch ◽  
M. Schnieder
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Operating Conditions ◽  
Pressure Side ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
High Lift ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

This paper investigates the aerodynamic and film cooling effectiveness characteristics of a first stage turbine high lift guide vane and its corresponding downstream blade. The vane and blade geometrical profiles and operating conditions are representative of that normally found in a heavy-duty gas turbine. Both the vane and the blade airfoils consist of multi-row film cooling holes located at various axial positions along the airfoil chord. The film cooling holes are geometrically three-dimensional in shape and depending on the location on the airfoil; they can be either symmetrically fan shaped or non-symmetrically fan shaped. Additionally the film cooling holes can be either compounded or in-line with the external flow direction. Numerical studies and experimental investigations in a linear cascade have been conducted at vane and blade exit isentropic Mach number of 0.8. The influence of the coolant flow ejected from the film cooling holes has been investigated for both the vane and the blade profiles. For the nozzle guide vane, the measured film cooling effectiveness compared well with the predictions, especially on the pressure side. The suction side film cooling effectiveness, which consisted of two pre-throat film rows, proved very effective up-to the suction side trailing edge. For the blade, there was a reasonable comparison between the measured and predicted film cooling effectiveness. Again the blade pre-throat fan shaped cooling holes proved very effective up-to the suction side trailing edge. For the vane, the impact of varying the blowing ratios showed a strong variation in the film cooling effectiveness on the pressure side. However, on the blade, the effect of varying the blowing ratio had a greater impact on the suction side film effectiveness compared to the pressure side.

Effects of Solid Particle Ingestion Through an HP Turbine

2012 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
Leading Edge ◽  
Suction Side ◽  
Operating Conditions ◽  
Pressure Side ◽  
Trailing Edge ◽  
Premature Failure ◽  
Narrow Strip ◽  
Tracking Model

Modern gas turbines operate in severe dusty environments, and because of such harsh operating conditions, their blades experience significant degradation in service. This paper presents a numerical study of particle dynamics and erosion in an hp axial turbine stage. The flow field is solved separately from the solid phase and constitutes the necessary data in the particle trajectories simulations using a Lagrangian tracking model based on the finite element method. Several parameters consider a statistical description such as particle size, shape and rebound, in addition to the turbulence effect. A semi empirical erosion correlation is used to estimate erosion contours and blades deteriorations, knowing the locations and conditions of impacts. The trajectory and erosion results show high erosion rates over the pressure side of NGV near trailing edge, in addition to extreme erosion observed toward the root corner, due to high number of particles impacting with high velocities. On the suction side, erosion is mainly over a narrow strip from leading edge. Erosion in the rotor blade is shown along the leading edge and spreading over the fore of the blade suction side, owing to a flux of particles entering at high velocities and incidence. On the pressure side, regions of dense erosion are observed near the leading edge and trailing edge as well as the tip corner. Critical erosion spots seen over NGV and rotor blade are signs of a premature failure.

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