Preliminary Investigation on the Effect of the Modification of the Sweep Angle at the Blade Tip of Forward Swept Axial Fans

2017 ◽  
Author(s):  
Massimo Masi ◽  
Andrea Lazzaretto
Keyword(s):  
Preliminary Investigation ◽  
Suction Side ◽  
The Other ◽  
Axial Fan ◽  
Sweep Angle ◽  
End Effects ◽  
Flow Rates ◽  
Stall Margin ◽  
Other Hand ◽  
Blade Tip

The flow path close to the suction side of fan rotor blades mostly affects the overall drag of the blading. The blade lift is affected as well because of the separation of the low energy boundary layer that drives the blade into stall at low fan flow rates. Forward sweep allows to position the airfoil sections of blades featuring a positive circulation gradient along the span so that they “accompany” the near-wall flow trajectories at the blade suction side. So, rotor efficiency and stall margin of the fan can be improved. On the other hand, blade end effects play a relevant role in high hub-to-tip and low aspect ratio rotors and may compromise the effectiveness of forward sweep. Nevertheless, some authors in the literature stated the beneficial contribution of changing the sweep angle at the ends of the blade both at design and off-design conditions. The paper studies the end effects on constant-swirl design rotors by means of CFD simulations focusing on the distribution of blade sweep in the near-tip region. In particular, the performance and efficiency calculated for a forward swept tube-axial fan featuring a hub-to-tip ratio equal to 0.4 are compared with those estimated for the corresponding unswept fan at equal duty point. Several modifications of the sweep distribution in the blade tip region are considered in the swept fan to quantify their effect on performance, efficiency and stall margin. Results show that the addition of up to 6 degrees of local forward sweep at the blade tip to the unswept blading does not affect fan pressure at design operation. On the other hand, this local increase of the sweep angle allows for a very notable increase of the peak pressure and efficiency at flow rates close to stall inception.

Numerical Study of Flow and Heat Transfer on a Blade Tip With Different Leakage Reduction Strategies

2003 ◽  
Author(s):  
Sumanta Acharya ◽  
Huitao Yang ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Flow Rates ◽  
Leakage Reduction ◽  
Flow And Heat Transfer ◽  
Reduction Strategies ◽  
Blade Tip

Numerical calculations are performed to explore different strategies for reducing tip leakage flow and heat transfer on the GE-E3 High-Pressure-Turbine (HPT) rotor blade. The calculations are performed for a single blade with periodic conditions imposed along the two boundaries in the circumferential-pitch direction. Several leakage reduction strategies are considered, all for a tip-clearance of 1.5% of the blade span, a pressure ratio (ratio of inlet total pressure to exit static pressure) of 1.2, and an inlet turbulence level of 6.1%. The first set of leakage reduction strategies explored include different squealer tip configurations: pressure-side squealer, suction-side squealer, mean-camber line squealer, and pressure plus suction side squealers located either along the edges of the blade or moved inwards. The suction-side squealer is shown to have the lowest heat transfer coefficient distribution and the lowest leakage flow rates. Two tip-desensitization strategies are explored. The first strategy involves a pressure-side winglet shaped to be thickest at the location with the largest pressure difference across the blade. The second strategy involves adding inclined ribs on the blade tip with the ribs normal to the local flow direction. While both strategies lead to reduction in the leakage flow and tip heat transfer rates, the ribbed tip exhibits considerably lower heat transfer coefficients. In comparing the two desensitization schemes with the various squealer tip configurations, the suction side squealer still exhibits the lowest heat transfer coefficient and leakage flow rates.

Compressible Simulation of Flow and Sound Around a Small Axial-Flow Fan With Flow Through Casing Slits

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Hiroshi Yokoyama ◽  
Katsutake Minowa ◽  
Kohei Orito ◽  
Masahito Nishikawara ◽  
Hideki Yanada
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Aerodynamic Performance ◽  
Design Flow ◽  
Low Flow ◽  
Axial Fan ◽  
Flow Rates ◽  
Blade Tip ◽  
Flow Through ◽  
Design Flow Rate

Abstract Small axial fans are used for cooling electronic equipment and are often installed in a casing with various slits. Direct aeroacoustic simulations and experiments were performed with different casing opening ratios to clarify the effects of the flow through the casing slits on the flow field and acoustic radiation around a small axial fan. Both the predicted and measured results show that aerodynamic performance deteriorates at and near the design flow rate and is higher at low flow rates by completely closing the casing slits compared with the fan in the casing with slits. The predicted flow field shows that the vortical structures in the tip vortices are spread by the suppression of flow through the slits at the design flow rate, leading to the intensification of turbulence in the blade wake. Moreover, the pressure fluctuations on the blade surface are intensified, which increases the aerodynamic sound pressure level. The suppression of the outflow of pressurized air through the downstream part of the slits enhances the aerodynamic performance at low flow rates. Also, the predicted surface streamline at the design flow rate shows that air flows along the blade tip for the fan with slits, whereas the flow toward the blade tip appears for the fan without slits. As a result, the pressure distributions on the blade and the torque exerted on the fan blade are affected by the opening ratio of slits.

The Separation of Light Gaseous Isotopes by Mass Diffusion Columns II

1964 ◽  
Vol 19 (6) ◽  
pp. 747-755
Author(s):  
W. J. De Wet ◽  
J. Los
Keyword(s):  
Theoretical Analysis ◽  
Mass Diffusion ◽  
Experimental Results ◽  
The Other ◽  
Countercurrent Flow ◽  
Gas Solubility ◽  
Flow Rates ◽  
Mixing Effects ◽  
Other Hand ◽  
Good Agreement

The design of mass diffusion columns operated with partition membranes, for the separation of light gaseous isotopes, is discussed. A theoretical analysis of experimental results obtained indicates that a good agreement between experimental results and theory is only obtained at low column pressures and moderate countercurrent flow rates. At fairly low countercurrent flow rates mixing effects due to viscous dragging and gas solubility by the condensate appear to be considerable whereas excessively high countercurrent flow rates, on the other hand, also seem undesirable. Some suggestions are proposed to obviate impairing effects at least to some extent.

Identifying the Types of Phobia: A Preliminary Investigation to Reduce Phobia through Gaming Approach

2019 ◽  
Vol 892 ◽  
pp. 150-156
Author(s):  
Aslina Baharum ◽  
Nurul Hidayah Mat Zain ◽  
Anita Mohd Yasin ◽  
Mohd Nor Hajar Hasrol Jono ◽  
Nor Azida Mohamed Noh ◽  
...  
Keyword(s):  
Mental Health ◽  
Quantitative Method ◽  
Online Survey ◽  
Preliminary Investigation ◽  
The State ◽  
The Other ◽  
Other Hand ◽  
Receive Treatment ◽  
To Receive

People fear something, as the feeling is normal for a person. Fear reactions are essential for survival. Fear will triggered whenever an individual facing something scary or even confronted with something new that seems potentially dangerous. Phobia on the other hand is an intense feeling of fear towards objects, animals, activities, situations or persons. However, many people do not know they suffered from phobia. Any fear during childhood might develop into phobias. People with phobias are most likely to avoid any place or situation that might trigger their fear so that they feel relief. They also keep their phobia to themselves and not telling other people about it. Besides, they are most likely refuse to go to receive treatment from psychiatrist or therapist. This is due to the norm of the society that seeing psychiatrist or therapist means that person suffering from mental health, which is embarrassing. This paper identified the types of phobia among Malaysian for preliminary investigation for reducing phobia through gaming approach. The quantitative method based on questionnaires, which contains of 18 questions used in the random online survey. The set of questions are adapted from Fear of Spiders Questionnaire. The higher the marks are the higher the state of phobia of the individuals will be. It is hope that by identifying the types of phobia may use to suggest an alternative gaming tool in reducing phobia.

Attenuation of leakage flow using axially nonuniform tip clearance in high loading transonic compressor rotor

2021 ◽  
pp. 095441002110221
Author(s):  
Weiwei Cui ◽  
Fusong Liu ◽  
Xinglu Wang ◽  
Fei Yao
Keyword(s):  
Suction Side ◽  
Boundary Layer Separation ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Front Part ◽  
Low Velocity ◽  
Stall Margin ◽  
Blade Tip ◽  
Transonic Rotor ◽  
Velocity Region

Several linearly nonuniform clearances have been designed to explore a novel strategy for attenuation of leakage flow in tip region of high loading transonic rotor and the effects of axially nonuniform clearance on detailed tip flow structure and stable operating range of rotor have been discussed as well. The results showed that the tip flow characteristic of rotor is affected mainly by the combined effects of two parts of low-velocity flow, which are produced by interaction of leakage flow with passage shock and boundary layer separation near suction side, respectively. However, the stall margin of rotor and isentropic efficiency near tip region is dominated significantly by the former part, and the local changes of size and shape of tip clearance have a large influence on it. Once the strength of leakage flow decreases due to clearance size variation, the boundary layer separation near suction side of blade tip worsens gradually and increases additional aerodynamic losses in passage. Both the mass flow rate and mixing losses of the tip leakage flow can be reduced due to a smaller size of clearance existing in front part of clearance of rotor with a linearly divergent clearance shape, and the area of low-velocity region near pressure side has reduced accordingly. By contrast, a linearly convergent shape of tip clearance can increase both the area of low-velocity region and the mixing loss of leakage flow as a result of a larger size of clearance existing over the front part of blade tip of rotor. Eventually, a divergent shape of tip clearance with a reasonable minimum size near leading edge of blade tip is preferred for transonic rotor in consideration of the benefit in stall margin improvement with nearly no penalty in efficiency.

Effect of increased neck vein pressure on intestinal lymphatic pressure in awake sheep

1992 ◽  
Vol 262 (5) ◽  
pp. R892-R894 ◽  
Author(s):  
R. E. Drake ◽  
R. D. Abbott
Keyword(s):  
Thoracic Duct ◽  
Lymphatic Vessels ◽  
Ringer Solution ◽  
Lymph Flow ◽  
The Other ◽  
Flow Rates ◽  
Intestinal Lymph ◽  
Other Hand ◽  
Intestinal Lymphatics ◽  
Increased Pressure

Lymphatic vessels from the intestines drain into the thoracic duct, and the thoracic duct empties into veins in the neck. Thus increases in neck vein pressure (PNV) might slow intestinal lymph flow, provided the increased pressure is reflected upstream through the lymphatic vessels. To test the effect of increases in PNV on lymphatic pressure, we cannulated intestinal lymphatics in the direction of flow in six sheep. After the sheep recovered from surgery, we measured the pressure in the lymphatics (Px) as we increased PNV in steps. Px increased only slightly (but significantly) from 7.4 +/- 2.0 to 11.4 +/- 5.2 (SD) cmH2O when we increased PNV from baseline (0.8 +/- 2.4 cmH2O) to 37.4 +/- 4.1 cmH2O. However, when we simulated an increased lymph flow by infusing Ringer solution into the lymphatics at 1,000 microliters/min, Px increased to 24.6 +/- 7.0 cmH2O at PNV equal to 37.1 +/- 5.3 cmH2O. These results indicate that, at normal lymph flow rates, increases in neck vein pressure cause only small increases in intestinal lymphatic pressure. On the other hand, when lymph flow is elevated, increases in neck vein pressure may substantially increase lymphatic pressure and thus slow intestinal lymph flow.

Investigation on the effects of winglet geometry in a high loading compressor rotor

2021 ◽  
pp. 095765092110170
Author(s):  
Qingjun Zhao ◽  
Weiwei Cui ◽  
Wei Zhao ◽  
Xiaorong Xiang ◽  
Jianzhong Xu
Keyword(s):  
Flow Characteristics ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Low Velocity ◽  
Flow Area ◽  
Significant Deterioration ◽  
Maximum Width ◽  
Stall Margin ◽  
Blade Tip

The tip winglet is employed to improve the flow stability of NASA Rotor 37. Two suction-side winglets with the maximum width of 0.25 and 0.5 times of the width of local blade tip section and two pressure-side winglets with the maximum width of 0.5 and 0.9 times of the width of local blade tip section are designed and evaluated by numerical analysis of 3-D flowfield. The results show a rough leakage channel with two static pressure peaks over blade tip is formed due to the existing of pressure side winglet, and it benefits to reduce the effective through-flow area and massflow rate of leakage flow. The blocking effect on leakage flow weakens in new rotor with suction side winglet and it brings out the dramatical increase of leakage massflow rate and additional losses in tip region of rotor. With the comprehensive effects produced by tip winglet on leakage flow, the low-velocity region concerned on the interaction of leakage flow with passage shock has been reduced obviously in rotor with pressure side winglet and it leads to an over 11% increase of stall margin of transonic rotor with no penalty of efficiency. On the contrary, the suction side winglet contributes to a significant deterioration of tip flow characteristics of rotor with full expanded leakage flow and a smaller stall margin with over 17% decrease.

Control of steady-state pH in rabbit proximal straight tubules

1987 ◽  
Vol 253 (2) ◽  
pp. F282-F289
Author(s):  
J. L. Atkins ◽  
M. B. Burg
Keyword(s):  
Steady State ◽  
Proximal Tubule ◽  
The Other ◽  
Slow Flow ◽  
Bicarbonate Concentration ◽  
Flow Rates ◽  
Other Hand ◽  
Straight Tubules

Steady-state pH (defined as the limiting pH reached at slow flow rates) was measured in isolated perfused rabbit proximal straight tubules (S2). With normal bath conditions (pH 7.4, bicarbonate 25 mM) the luminal steady-state pH was 6.85. Steady-state pH was directly related to bath pH and bicarbonate, but not to bath PCO2. Lowering of bath pH or bicarbonate consistently decreased luminal steady-state pH, and raising either caused steady-state pH to increase. When bath PCO2 was increased, on the other hand, steady-state pH either increased or decreased, depending on the concomitant changes in bicarbonate and pH. The changes in steady-state pH observed in the present studies following alterations in bath pH and bicarbonate concentration should, when extrapolated to the in vivo kidney, result in decreased delivery of bicarbonate from the proximal tubule in acidosis and increased delivery in alkalosis. The effects of potassium and chloride were also determined. Removal of potassium from the bath increased the steady-state pH, but removal of chloride from both the perfusate and bath had no significant effect.

Numerical Investigation of Cut-Corner in Recess Vaned Casing Treatment

2019 ◽  
Author(s):  
Xiangyi Chen ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Bo Luo
Keyword(s):  
Main Flow ◽  
Tip Clearance ◽  
Axial Fan ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stable Operating ◽  
Flow Circulation ◽  
Blade Tip ◽  
Flow Blockage ◽  
Blade Tip Clearance

Abstract This paper studies the effects of cut-corner in the recess vaned casing treatment (RVCT) on the performance of a low-speed axial fan. The solid casing fan and fans with corner-cut RVCT have been simulated respectively. The numerical simulation shows that the introduction of the RVCT and the modification of RVCT cut-corner size bring about obvious changes in fan performance. The RVCT establishes a connection between the RVCT channel and the main flow, contributing to the extra flow circulation in the tip region and resulting in an efficiency penalty for each RVCT configuration. The cut-corner is not necessarily beneficial to the improvement of the stable operating range. With the increase of cut-corner size at the rear wall of RVCT, the improvement of stall margin firstly demonstrates a drop to −8.82% before jumping to over 60%. RVCTs with different cut-corner sizes play different roles in the flow interaction between RVCT channel and main flow, and the stall margin poses a positive relationship with the mass flow passing through RVCT. The size of the cut-corner is responsible for the flow field in RVCT. The RVCT with small cut-corner size functions as a larger blade tip clearance and results in a smaller stall margin than the solid casing fan. Therefore, the size of the cut-corner in RVCT should be large enough to dredge the flow blockage in the tip region and delay the origin of stall.

scholarly journals The production and preliminary investigation of Burulin, a new skin test reagent for Mycobacterium ulcerans infection

1975 ◽  
Vol 74 (1) ◽  
pp. 7-16 ◽  
Author(s):  
J. L. Stanford ◽  
W. D. L. Revill ◽  
W. J. Gunthorpe ◽  
J. M. Grange
Keyword(s):  
Skin Test ◽  
School Children ◽  
Preliminary Investigation ◽  
Cross Reaction ◽  
Mycobacterium Ulcerans ◽  
The Other ◽  
Normal School ◽  
Test Antigen ◽  
Other Hand ◽  
New Skin

SUMMARYThe preparation of a skin test antigen from Mycobacterium ulcerans by ultrasonic disintegration and filtration is described. The reagent, called Burulin, was tested in Africa in normal school children, and in patients with leprosy, tuberculosis or M. ulcerans disease. Those with tuberculosis or M. ulcerans disease were simultaneously tested with Tuberculin PPD. Burulin was found to be highly specific for patients in the reactive stage of M. ulcerans disease, and there was no cross-reaction in patients with other mycobacterioses. On the other hand, the majority of patients with M. ulcerans disease reacting to Burulin also produce positive reactions to Tuberculin PPD.

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