A study of slip factor and velocity components at the rotor exit of forward-curved squirrel cage fans, using laser Doppler anemometry

2001 ◽  
Vol 215 (4) ◽  
pp. 453-463 ◽  
Author(s):  
N Montazerin ◽  
A Damangir ◽  
A. Kazemi Fard
Keyword(s):  
Large Deviation ◽  
Laser Doppler Anemometry ◽  
Incidence Angle ◽  
Design Criterion ◽  
Tangential Component ◽  
Radial Velocity Component ◽  
Squirrel Cage ◽  
Slip Factor ◽  
Prime Design ◽  
Local Slip

Velocity profiles outside the rotor of four squirrel cage fans are measured in order to calculate their local slip factors. They show that the fluid exit angle from the rotor and the blade outlet angle of such fans are very different. Inlet configuration and volute spread angle both affected the direction of the flow out of the rotor and hence the slip factor. The general understanding in centrifugal turbomachines is that more energy transfer per unit mass is equivalent to a larger tangential component of velocity and therefore a larger slip factor. In squirrel cage fans a small slip factor results from a large radial velocity component out of the rotor. This gives a larger volumetric flowrate with no sensible head loss. The advantages of a large incidence angle and a large deviation mean that flow adherence to the blades is not always a prime design criterion in such fans.

Flow and Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

2000 ◽  
Author(s):  
Abdul A. Jaafar ◽  
Fariborz Motallebi ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Laser Doppler Anemometry ◽  
Tangential Component ◽  
Rotating Disc ◽  
Turbine Engine ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Rotating Discs ◽  
Cooling Air

In this paper, new experimental results are presented for the flow in a co-rotating disc system with a rotating inner cylinder and a stationary stepped outer casing. The configuration is based on a turbine disc-cooling system used in a gas turbine engine. One of the rotating discs can be heated, and cooling air is introduced through discrete holes angled inward at the periphery of this disc. The cooling air leaves the system through axial clearances between the discs and the outer casing. Some features of computed flows, and both measured and computed heat transfer, were reported previously for this system. New velocity measurements, obtained using Laser Doppler Anemometry, are compared with results from axisymmetric, steady, turbulent flow computations obtained using a low-Reynolds-number k-ε turbulence model. The measurements and computations show that the tangential component of velocity is invariant with axial location in much of the cavity, and the data suggest that Rankine (combined free and forced) vortex flow occurs. The computations fail to reproduce this behaviour, and there are differences between measured and computed details of secondary flow recirculations. Possible reasons for these discrepancies, and their importance for the prediction of associated heat transfer, are discussed.

Peculiarities of marine eddy manifestation in the structure of surfactant slick band

2021 ◽  
Author(s):  
Olga Shomina ◽  
Tatiana Tarasova ◽  
Olga Danilicheva ◽  
Ivan Kapustin
Keyword(s):  
Water Surface ◽  
Remote Sensing Data ◽  
Radial Component ◽  
Tangential Component ◽  
Length Scale ◽  
Russian Science ◽  
Radial Velocity Component ◽  
Radar Images ◽  
Wind Velocities ◽  
Spiral Shape

<p>Slick structures on the sea surface can mark processes occurring in upper ocean and atmosphere. Spiral shape of slicks observed in optical and radar images of water surface is traditionally interpreted through the manifestation of marine eddy which length scale is supposed to be equal to the scale of spiral. This assumption implies that wind has no effect on the kinematics of forming slick band, which, according to our estimation, is incorrect even at moderate wind velocities. This approach can cause misinterpretation of remote sensing data when estimating the characteristics of observed marine eddies. This study is devoted to the investigation of conditions necessary for the formation of slick spiral and to some peculiarities of its shape and scale.</p><p>The system of equations for the description of kinematics of Lagrangian particle (element of water surface covered with surface active substance) in the fields of axisymmetric eddy with non-zero radial velocity component and homogeneous wind was obtained. It is demonstrated that the spiral center is not collocated with the center of the eddy; the distance between them can achieve the eddy length scale. It is shown that the displacement of the spiral center and the direction of the main axis is quasi perpendicular to the wind direction when radial component of the eddy is small compared to the tangential component. The presence of the threshold wind velocity corresponding to the breakdown of the spiral structure is demonstrated analytically. The possibilities of correct retrieval of length scales and character velocities of observed sub mesoscale marine eddies are discussed.</p><p>The research was funded by the Russian Science Foundation (Project RSF 18-77-10066).</p>

Effect of J-Shaped Casing Treatment on Flow Stability and Performance of an Axial Compressor

2012 ◽  
Author(s):  
Ramjan R. Pathan ◽  
Quamber H. Nagpurwala ◽  
Ananthesha Bhat
Keyword(s):  
Incidence Angle ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Stability Margin ◽  
Tangential Component ◽  
Favourable Effect ◽  
Slight Reduction ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor

Casing Treatment (CT) is one of the passive methods to increase the stability margin of the compress and hence that of the aircraft jet engines. In this paper, a novel J-shaped axial CT slot geometry is designed and numerically analysed for its effect on the performance of a single stage NACA transonic compressor. The predicted performance of the isolated rotor was validated by comparing with the published experimental results. The predicted efficiency of the baseline transonic rotor agreed well with experimental data, but the total pressure ratio was under predicted over the entire operating range. The J-shaped CT slots, with 100% axial coverage over the rotor tip chord, were able to extend the stall mass flow rate by almost 19.45% compared to the baseline rotor, accompanied with a slight reduction in rotor efficiency by 1.42%. The high pressure air entered the slots at rotor exit and flowed back through the slots and the plenum, and ejected at the rotor inlet to energise the low momentum end wall flow. The interaction of main inlet flow and the ejected flow having large tangential component of velocity, had favourable effect on the rotor incidence angle, and hence on rotor stall margin.

Underwater explosion approximate method research on ship with polymer coating

2016 ◽  
Vol 231 (2) ◽  
pp. 384-394
Author(s):  
Zhen-Hua Zhang ◽  
Yong Chen ◽  
Xiu-Chang Huang ◽  
Hong-Xing Hua
Keyword(s):  
Polymer Coating ◽  
Optimization Design ◽  
Underwater Explosion ◽  
Hard Core ◽  
Design Criterion ◽  
Soft Core ◽  
Homogenization Theory ◽  
Shock Load ◽  
Prime Design ◽  
Equivalent Continuum Model

Battle damage survivability is the prime design criterion of naval ships. Composites and hybrid structures such as polymer coating attract much attention to increase the ship survivability. Aiming to develop the parameter optimization design of the coating and to assess the underwater explosion shock environment and the blast-resistant effect of polymer coating efficiently, an approximate numerical method was performed in this preliminary study. An equivalent continuum model based on the homogenization theory was introduced to simulate the dynamic behavior of the coating. The test data of full-scale underwater explosion tests and the numerical simulation results were investigated. The blast-resistant property of the polymer coating was elaborated. The core strength had an important influence on the ship dynamic response: under low-intensity underwater explosion shock load, “soft” core had greater blast-resistant effect than the other ones, while under high-intensity underwater explosion shock load, “ordinary” core and “hard” core had better blast-resistant effect than the “soft” core.

A new concept for squirrel-cage fan inlet

1998 ◽  
Vol 212 (5) ◽  
pp. 343-349 ◽  
Author(s):  
N Montazerin ◽  
A Damangir ◽  
S Mirian
Keyword(s):  
Laser Doppler Anemometry ◽  
Separated Flow ◽  
Rotor Blades ◽  
Manufacturing Cost ◽  
Flow Area ◽  
Squirrel Cage ◽  
Standard Characteristic ◽  
Measured Flow ◽  
Major Loss ◽  
Conceptual Study

The squirrel-cage fan with a newly introduced outward inlet lip is studied experimentally. Previous research has demonstrated the importance of inlet flow control on the general flow field and vortex generation of such fans. The bell-mouth inlet, which is the common industrial and academic practice, has drawbacks that result in flow separation and turbulence enhancement. The adapted experimental approach is a conceptual study. It is a combination of standard characteristic measurements and detailed laser Doppler anemometry. The measured flow pattern inside the volute demonstrates that the separated flow behind the inlet lip, which for an ordinary inward lip occupies a large part of the rotor blades, disappears. This is promising since removing this separated flow diminishes a major loss-making region in this fan and adds to the effective flow area. It also reduces noise and gives uniform blade loading. The results also show an improvement in performance in comparison with that of a fan with an ordinary inward inlet lip. This modification is industrially feasible with no extra manufacturing cost and therefore can represent a substantial advance over the current practice.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

Atomic force microscopy (AFM) of the topography of silicon surfaces exposed to ion beams

1992 ◽  
Vol 50 (2) ◽  
pp. 1132-1133
Author(s):  
Mark Denker ◽  
Jennifer Wall ◽  
Mark Ray ◽  
Richard Linton
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Incidence Angle ◽  
Ion Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
Ion Beams ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Trace Impurities ◽  
Energy Dose

Reactive ion beams such as O2+ and Cs+ are used in Secondary Ion Mass Spectrometry (SIMS) to analyze solids for trace impurities. Primary beam properties such as energy, dose, and incidence angle can be systematically varied to optimize depth resolution versus sensitivity tradeoffs for a given SIMS depth profiling application. However, it is generally observed that the sputtering process causes surface roughening, typically represented by nanometer-sized features such as cones, pits, pyramids, and ripples. A roughened surface will degrade the depth resolution of the SIMS data. The purpose of this study is to examine the relationship of the roughness of the surface to the primary ion beam energy, dose, and incidence angle. AFM offers the ability to quantitatively probe this surface roughness. For the initial investigations, the sample chosen was <100> silicon, and the ion beam was O2+.Work to date by other researchers typically employed Scanning Tunneling Microscopy (STM) to probe the surface topography.

Principle and practice of high-resolution imaging with a field-emission TEM

1992 ◽  
Vol 50 (1) ◽  
pp. 138-139
Author(s):  
Max T. Otten ◽  
Wim M.J. Coene
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Incidence Angle ◽  
Temporal Coherence ◽  
Energy Spread ◽  
High Resolution Imaging ◽  
Major Improvement ◽  
High Resolution Images ◽  
Resolution Imaging

High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

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