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Experimental Investigation of a Forward Swept Rotor in a Multistage Fan with Inlet Distortion  [PDF]
Aspi R. Wadia
International Journal of Aerospace Engineering , 2011, DOI: 10.1155/2011/941872
Abstract: Previous studies of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep to multistage configurations. The experimental investigation compare two builds of an advanced two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two-stage fan's sensitivity with inlet distortion. 1. Introduction The trend in using aerodynamic sweep to improve the performance of transonic blading [1–8] has been one of the most significant technological evolutions for compression components in turbomachinery. Wadia et al. in [2] reported on the experimental evaluation and the subsequent analytical assessment of both aft and forward sweep compressor rotor technology with respect to aerodynamic performance and stability in a single-stage environment. The reduced shock/boundary layer interaction, resulting from reduced axial flow diffusion and less accumulation of centrifuged blade surface boundary layer at the tip, was identified as the prime contributor to the enhanced performance and aerodynamic stability with forward sweep. Prompted by the single-stage results with the forward swept rotor, a program was started in 1993 at GE Aircraft Engines under the United States government sponsorship to pursue the performance benefits with forward sweep in multistage configurations. Most of this paper deals with the results and insights gained from these two-stage, low-aspect-ratio transonic fan tests including, for the first time, the effect of handling of inlet distortion with forward swept rotors. In addition, in the case of the
The laminar boundary layer on a rotating wind turbine blade
INCAS Bulletin , 2010, DOI: 10.13111/2066-8201.2010.2.2.6
Abstract: The present paper describes a method to calculate velocity profiles in the boundary layer ofrotating blade. A differential approach is used to solve the laminar boundary layer equations. Theeffects of tip speed ratio, dimensionless radial position r/R and angle of attack have been analyzed.The test airfoils used in the simulations are NACA 63-215 and S809. The resulting velocity profiles inthe chordwise and spanwise directions are mapped and stored in a Database according to theboundary layer parameters.
Preliminary experimental investigation of boundary layer in decelerating flow  [cached]
Hladík O.,Joná? P.,P?íhoda J.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134501038
Abstract: Investigations of characteristics of turbulence inside boundary layer under decelerating flow were studied by means of constant temperature anemometer. The decelerating flow was simulated in the closed circuit wind tunnel 0.9 m × 0.5 m at IT AS CR. The free stream turbulence was either natural o risen up by square mesh plane grid. The details of experimental settings and measurement procedures of the instantaneous longitudinal velocity component are described and the distributions of intensity, skewness and kurtosis of turbulent fluctuations are discussed in the contribution.
ВПЛИВ В БРАЦ ПОВЕРХН , ЩО ОМИВА ТЬСЯ НАП ВОБМЕЖЕНИМ СТРУМЕНЕМ, НА ХАРАКТЕРИСТИКИ ПРИМЕЖОВОГО ШАРУ Еxperimental investigation of influence the plate vibration on the characteristics of boundary layer formed by near plate jet Влияние вибрации поверхности, омываемой полуограниченной струей, на характеристики ее пограничного слоя  [cached]
С.А. Ищенко,А.А. Бондарец
Proceedings of National Aviation University , 2010,
Abstract: Наведено результати експериментального досл дження впливу в брац пластини, що омива ться нап вобмеженим струменем, на характеристики його примежового шару. The result of the experimental investigation on the influence of the plate’s vibration on characteristics of boundary layer which is formed by near plate jet has been presented in the article. Представлены результаты экспериментального исследования влияния вибрации пластины, омываемой полуограниченной струей, на характеристики ее пограничного слоя.
Theoretical, Experimental and Numerical Investigations of the Effect of Inlet Blade Angle on the Performance of Regenerative Blowers  [PDF]
Tarek Abdel-Malak Mekhail, Omar Mohamed Dahab, Mohamed Fathy Sadik, Mahmoud Mohamed El-Gendi, Hesham Sayed Abdel-Mohsen
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.53025
Abstract: Regenerative machines allow high heads at small flow rates and present performance curves with very stable features. This research includes a study of the effect of four inlet flow angles (90°, 115°, 125° and 135°) of the blade at outlet flow angle of 90° on the performance of regenerative blower at rotation speed of 3000 rpm and at different flow rates. Investigation and comparison of the experimental results with both one-dimensional theoretical model and numerical CFD technique using CFX-ANSYS 16.1 are done. The numerical CFD analysis show that the flow enters the impeller from the blade side (about 65% of the blade side area) and leaves from the blade tip and blade side (the remaining 35% from the blade side area). According to this observation, a mathematical model that is based on momentum exchange theory to handle one inlet angle and two exit angles for the regenerative blower impeller blades is proposed. Consequently, the experimental work is carried out by two steps. The first step is done by studying the effect of inlet blade angle of 90° and analyzing the results by using the CFD analysis. The CFD results show shock losses and vortices behind each blade at the inlet flow regions. To reduce these losses, an increase of the inlet blade angle in a range between 25° to 45° is proposed. The second step is the splitting of this angle range to three inlet blade angles of 115°, 125° and 135° in order to study and analyze the CFD results for these angels. The CFD analysis shows the disappearance of the shock losses and vortices that are formed behind the blade of angle 90°. The experimental results show that the pressure head and the efficiency depend strongly on the blade inlet and outlet flow angles as well as on the blade geometry. The results also show that the best blower performance can be obtained at an inlet flow angle of 125°, and this is confirmed by CFD simulation analysis. Finally, it
Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign
F. Sa d, A. Brut, B. Campistron,F. Cousin
Annales Geophysicae (ANGEO) , 2007,
Abstract: This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL) development during two specific meteorological conditions of the second Intensive Observation Period (IOP). The first situation (IOP2a, from 22 June to 23 June) corresponds to moderate, dry and cold northerly winds (end of Mistral event), coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June). In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.
Effect of Boundary Layer Fence Location on HAWT Power Performance  [PDF]
Sundaravadivel Arumugam, Nadaraja Pillai Subramania, Senthilkumar Chidambaram
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.78101
Abstract: Even though wind energy is a deep-rooted technology, but not yet mature and hence there are bounteous scopes for improvement to reduce the cost of wind energy. An experimental investigation has been carried out on 1:25 scaled S809 aerofoil blade featuring boundary layer fence at various span wise location. Quantifying electrical power obtained by rotation of wind turbine rotor coupled with dynamic testing system. A baseline model with no flow control and an upgraded model with detachable boundary layer fence have been studied in the wind tunnel. For upgraded model, fences were placed along the location of 40% to 90% of the blade span. The rotor blades are then tested dynamically in wind tunnel at open terrain condition for 7 m/s, 9 m/s and 11 m/s velocities. In order to study the effect of boundary layer fence test has been carried out in the low speed wind tunnel having test section of size 0.9 m × 1.2 m × 2 m. Scope corder DL 750 is used to measure time varying voltage and proximity sensor with its compatible display unit is used to measure the rotor RPM. The flow behaviour was found to be considerably favourable from conventional rotor blades. Installation of fence has been found promising for increased energy extraction from air column by controlling the three dimensional span wise flow. Results demonstrate the potential of the proposed model which can obtain a maximum of about 11.8% increase in the power. In addition, the significance of the location of wing fence and blade pitch angle has been analysed.
Effect of Secondary Flows on Heat Transfer of a Gas Turbine Blade  [PDF]
Hesham M. El-Batsh,Sameh A. Nada,Samia Nasreldin Abdo,Abdelgalil A. El-Tayesh
International Journal of Rotating Machinery , 2013, DOI: 10.1155/2013/797841
Abstract: This study presents experimental and numerical investigation for three-dimensional heat transfer characteristics in a turbine blade. An experimental setup was installed with a turbine cascade of five-blade channels. Blade heat transfer measurements were performed for the middle channel under uniform heat flux boundary conditions. Heat was supplied to the blades using twenty-nine electric heating strips cemented vertically on the outer surface of the blades. Distributions of heat transfer coefficient were obtained at three levels through blade height by measuring surface temperature distribution using thermocouples. To understand heat transfer characteristics, surface static pressure distributions on blade surface were also measured. Numerical investigation was performed as well to extend the investigation to locations other than those measured experimentally. Three-dimensional nonisothermal, turbulent flow was obtained by solving Reynolds averaged Navier-Stokes equations and energy equation. The shear stress transport model was employed to represent turbulent flow. It was found through this study that secondary flow generated by flow deflection increases heat transfer coefficient on the blade suction surface. Separation lines with high heat transfer coefficients were predicted numerically with good agreement with the experimental measurements. 1. Introduction The performance of gas turbine engines is determined by their specific work and thermal efficiency which are improved by increasing combustor gas exit temperature. However, increasing combustor exit temperature increases the thermal load on the first stage of a gas turbine engine. Consequently, heat transfer characteristics are required for engines safe operation. In addition, effective cooling of turbine blades is required to reduce thermal load and allow safe and effective operation at high levels of gas temperatures. To optimize blade cooling, exact understanding of surface heat transfer of a turbine blade is necessary. Heat transfer mechanism in gas turbine blades is very complicated due to the complexity of flow pattern around the blades. Flow in turbine cascades is characterized by different flow features which include accelerating flow on blade pressure side and accelerating and decelerating flow on blade surface. In addition, the passage flow is characterized by boundary layer effects, secondary flow generated by the passage pressure gradients, and vertical flow structures such as the leading edge horseshoe vortices. These flows affect the three-dimensional heat transfer in gas turbine
Investigation of Approaching Ocean Flow and its Interaction with Land Internal Boundary Layer
American Journal of Environmental Engineering , 2013, DOI: 10.5923/j.ajee.20130301.04
Abstract: The Alcantara Launch Center is located near the Brazilian Northeastern coastline downwind of a cliff 40 m high. Furthermore, the flow transition from open ocean past by the coastline generated an internal boundary layer (IBL) due to the roughness step change. The flow is mainly driven by the Trades, although the interaction with land-sea circulation may not be negligible. These features modify the ocean wind ocean profile as measured over land at the coastal site. We present here an ongoing research aiming to characterize the wind profile, which would serve as input flow profile in wind tunnel experiments and for gas dispersion studies. We analyzed the data of wind speed and direction collected between 1995 and 1999 by six aerovanes mounted in a 70-m height tower located about 200 m downwind the cliff. To study the diurnal and annual patterns of the wind profile the stored mean values of 10 min were monthly and hourly averaged. A simple estimate of the IBL height by assuming a dependence on the upwind distance of the shore as suggested in the literature were carried out. IBL height ranges from 30 to 40 m at tower location and being higher between 10 and 15 Local Time (LT). The wind profile power-law shows an alpha exponent greater (up to 0.35) than those encountered in the literature (about 0.10–0.11) for open ocean wind profile. The step change in the surface roughness cannot alone explain such a change in the alpha exponent. Other causes such as temperature step change and the cliff elevation certainly play a role to be still addressed.
Effect of the Radial Pressure Gradient on the Secondary Flow Generated in an Annular Turbine Cascade  [PDF]
Hesham M. El-Batsh
International Journal of Rotating Machinery , 2012, DOI: 10.1155/2012/509209
Abstract: This paper introduces an investigation of the effect of radial pressure gradient on the secondary flow generated in turbine cascades. Laboratory measurements were performed using an annular sector cascade which allowed the investigation using relatively small number of blades. The flow was measured upstream and downstream of the cascade using a calibrated five-hole pressure probe. The three-dimensional Reynolds Averaged Navier Stokes equations were solved to understand flow physics. Turbulence was modeled using eddy-viscosity assumption and the two-equation Shear Stress Transport (SST) k-ω model. The results obtained through this study showed that the secondary flow is significantly affected by the pressure gradient along blade span. The experimental measurements and the numerical calculations predicted passage vortex near blade hub which had larger and stronger values than that predicted near blade tip. The loss distribution revealed that secondary flow loss was concentrated near blade hub. It is recommended that attempts of reducing secondary flow in annular cascade should put emphasis on the passage vortex near the hub. 1. Introduction Large-scale steam and gas turbines are always used in power generation and industrial applications. Therefore, turbine efficiency and performance have major concern. The losses in a turbine can be divided into profile loss, secondary flow loss, and tip clearance loss. The profile loss is caused by the growth of the boundary layer on the blades. Secondary flow loss is generated due to the deflection through blade channel. Tip leakage loss is induced due to pressure difference between blade pressure side and blade suction side when the tip clearance gap exists. There are many factors which influence turbine losses. The pressure gradient, turbulence level, blade geometry, incoming velocity, and inlet boundary layer thickness represent important parameters affecting turbine efficiency. It is practically very difficult to perform detailed flow field measurements in an engine at operating conditions. Understanding the physics that governs the flow and the associated turbine cascade losses has been obtained through wind tunnel experiments. These laboratory tests not only allow detailed flow field measurements but also give the experimenter the possibility to investigate the effect of several parameters separately. Experimental studies using linear turbine cascades introduce the aspect of flow periodicity by arranging a number of blades of constant cross-sections separated by a constant pitch. Linear cascade experiments
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