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Journal articles on the topic 'Shrouded fan'

Author: Grafiati

Published: 9 March 2023

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1

Menq, C. H., J. H. Griffin, and J. Bielak. "The Forced Response of Shrouded Fan Stages." Journal of Vibration and Acoustics 108, no. 1 (January 1, 1986): 50–55. http://dx.doi.org/10.1115/1.3269303.

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This paper presents a general approach for modeling shrouded blade vibration that takes into consideration the nonlinear friction constraint at the shroud interface. In this approach, linear structures are characterized by receptances and shroud constraints by nonlinear impedances. The proposed methodology is presented in detail for simplified models of the bladed disk and shroud interface. The corresponding governing equations for the dynamic response are derived for both tuned and mistuned stages. As an example the method is applied to an idealized tuned stage. Two cases are considered, a lubricated shroud for which the coefficient of friction is equal to zero, and a frictionally constrained shroud. The effect of varying the shroud-to-shroud preload is studied. In the lubricated case nonlinear behavior is seen when vibrations are strong enough to result in separation of the shroud interfaces. In the case of finite friction there is a profound change in resonant frequencies when the preload is increased sufficiently to prevent gross slip at the shrouds.

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2

Chi, R. M., and A. V. Srinivasan. "Some Recent Advances in the Understanding and Prediction of Turbomachine Subsonic Stall Flutter." Journal of Engineering for Gas Turbines and Power 107, no. 2 (April 1, 1985): 408–17. http://dx.doi.org/10.1115/1.3239741.

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In this paper, some recent advances in the understanding and prediction of subsonic flutter of jet engine fan rotor blades are reviewed. Among the topics discussed are (i) the experimental evidence of mistuning in flutter responses, (ii) new and promising unsteady aerodynamic models for subsonic stall flutter prediction, (iii) an overview of flutter prediction methodologies, and (iv) a new research effort directed toward understanding the mistuning effect on subsonic stall flutter of shrouded fans. A particular shrouded fan of advanced design is examined in the detailed technical discussion.

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3

Yen, S. C., and Frank K. T. Lin. "Exit Flow Field and Performance of Axial Flow Fans." Journal of Fluids Engineering 128, no. 2 (September 19, 2005): 332–40. http://dx.doi.org/10.1115/1.2169809.

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Flow fields near the exit and the global performance parameters of the various types of axial flow fans are studied with Particle Image Velocimetry and a standard AMCA 210 flow bench. The fans used in this study included the shrouded, shroudless, and winglet-blade types. The velocity vectors, streamlines, vorticity contours, velocity distributions, and performances are presented and discussed. The flow patterns on the radial and axial planes show that a vortex always exists near the exit of the fans at various impeller angles. The experimental results demonstrate that the shrouded fan with winglets has the most stable flow field and the best fan performance.

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4

Liu, Yi-Xiong, Pei-Hong Cong, Yun-Wu Wu, Jin-Liang Li, and Xiang-Ping Wang. "Failure analysis and design optimization of shrouded fan blade." Engineering Failure Analysis 122 (April 2021): 105208. http://dx.doi.org/10.1016/j.engfailanal.2020.105208.

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5

Srinivasan, A. V., and D. G. Cutts. "Aerodynamically Excited Vibrations of a Part-Span Shrouded Fan." Journal of Engineering for Gas Turbines and Power 107, no. 2 (April 1, 1985): 399–407. http://dx.doi.org/10.1115/1.3239740.

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The structural response of a part-span shrouded fan due to an aerodynamic excitation was measured using strain gages. The excitation was provided by means of a 4-lobed distortion screen mounted upstream of the rotor. Vibration measurements made with tuned and mistuned conditions at integral order speeds have been analyzed to determine the aeromechanical response charcteristics of the assembly. The results from the experimental investigation are presented and discussed.

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6

Prstic, Suzana, and Avram Bar-Cohen. "“Heat Shield”—An Enhancement Device for an Unshrouded, Forced Convection Heat Sink." Journal of Electronic Packaging 128, no. 2 (February 16, 2006): 172–76. http://dx.doi.org/10.1115/1.2188955.

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The inherent advantages of forced air cooling have led to the widespread use of fully and partially shrouded heat sinks for the thermal management of high power microprocessors. The superior thermal performance that is achievable in the fully shrouded configuration is accompanied by a significant pressure drop penalty. The concept introduced in the current study, employs a thin sheet-metal “heat shield,” placed around a partially shrouded heat sink, to channel the flow directly into the heat sink. A combined numerical and experimental study has shown that the use of this “heat shield” can substantially enhance heat sink thermal performance, in a channel geometry and air flow range typical of commercial chip packages; making it comparable to that of a fully shrouded heat sink, with a substantially lower pressure drop (∼50%). In addition, this thermal enhancement device can be easily retrofitted into existing systems; improving performance without major channel and/or fan modifications.

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7

Moosania, Mostafa, Chao Zhou, and Site Hu. "Aerodynamics of a partial shrouded low-speed axial flow fan." International Journal of Refrigeration 130 (October 2021): 208–16. http://dx.doi.org/10.1016/j.ijrefrig.2021.05.031.

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8

Avanzini, Giulio, Umberto Ciniglio, and Guido de Matteis. "Full-Envelope Robust Control of a Shrouded-Fan Unmanned Vehicle." Journal of Guidance, Control, and Dynamics 29, no. 2 (March 2006): 435–43. http://dx.doi.org/10.2514/1.14314.

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9

de Divitiis, Nicola. "Performance and Stability Analysis of a Shrouded-Fan Unmanned Aerial Vehicle." Journal of Aircraft 43, no. 3 (May 2006): 681–91. http://dx.doi.org/10.2514/1.16210.

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10

Buccieri, Bryan M., and Christopher M. Richards. "Application of the aeroacoustic analogy to a shrouded, subsonic, radial fan." Journal of Sound and Vibration 385 (December 2016): 125–37. http://dx.doi.org/10.1016/j.jsv.2016.09.011.

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11

Han, Jing Ze, Bing Yan Jiang, Chao Wei Zhuang, and Xiong Chun Du. "Experimental Investigation on Aerodynamic Characteristics of Propeller in a Ducted-Fan Type VTOL UAV." Applied Mechanics and Materials 711 (December 2014): 12–15. http://dx.doi.org/10.4028/www.scientific.net/amm.711.12.

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An experimental investigation was completed with the objective of determining the performance characteristics of propeller in a Ducted-Fan Type VTOL UAV. The model consisted of three groups of two-bladed propellers with or withou an annular duct. The propellers share the same diameter but differernt blade pitchs.Model variations included the changes of the propeller and the duct shrouded combination. Static propulsion test data showed figure of lift increases with increasing blade pitch. The coaxial propellers lift did not perform as 2 times of the single propeller lift.The duct increase the duct fan system lift effectively.

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12

Griffin, J. H., and A. Sinha. "The Interaction Between Mistuning and Friction in the Forced Response of Bladed Disk Assemblies." Journal of Engineering for Gas Turbines and Power 107, no. 1 (January 1, 1985): 205–11. http://dx.doi.org/10.1115/1.3239684.

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This paper summarizes the results of an investigation to establish the impact of mistuning on the performance and design of blade-to-blade friction dampers of the type used to control the resonant response of turbine blades in gas turbine engines. In addition, it discusses the importance of friction slip force variations on the dynamic response of shrouded fan blades.

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13

Pardowitz, Benjamin, Antoine Moreau, Ulf Tapken, and Lars Enghardt. "Experimental identification of rotating instability of an axial fan with shrouded rotor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 229, no. 5 (August 2015): 520–28. http://dx.doi.org/10.1177/0957650915595898.

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14

Griffin, J. H. "On Predicting the Resonant Response of Bladed Disk Assemblies." Journal of Engineering for Gas Turbines and Power 110, no. 1 (January 1, 1988): 45–50. http://dx.doi.org/10.1115/1.3240085.

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The vibratory responses of blades in gas turbine engines vary because of mistuning. An approach is developed for calculating the statistical distribution of peak resonant stresses in engine blading. It is used to predict the vibratory response of an un-shrouded fan stage. The results of the calculation compare favorably with test data for the lower frequency modes. The procedure can be used to predict fleet durability and offers a practical engineering approach for dealing with stage mistuning.

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15

Avanzini, G., and G. de Matteis. "Design of the flight management system for a shrouded-fan uninhabited aerial vehicle." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 220, no. 5 (May 2006): 475–85. http://dx.doi.org/10.1243/09544100g02804.

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16

Carassale, Luigi, Andrea Cattanei, Fabio Mazzocut Zecchin, and Mehrdad Moradi. "Leakage flow flutter in a low-speed axial-flow fan with shrouded blades." Journal of Sound and Vibration 475 (June 2020): 115275. http://dx.doi.org/10.1016/j.jsv.2020.115275.

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17

Rynell, Anders, Mattias Chevalier, Mats Åbom, and Gunilla Efraimsson. "A numerical study of noise characteristics originating from a shrouded subsonic automotive fan." Applied Acoustics 140 (November 2018): 110–21. http://dx.doi.org/10.1016/j.apacoust.2018.05.006.

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18

Avanzini, G., S. D'Angelo, and G. de Matteis. "Design and development of a vertical take-off and landing uninhabited aerial vehicle." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 217, no. 4 (April 1, 2003): 169–78. http://dx.doi.org/10.1243/095441003769700735.

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This paper reports the status of the activities carried out at Polytechnic of Turin and University of Rome “La Sapienza” to design, build and fly a shrouded-fan uninhabited aerial vehicle. The project goal is the realization of a reliable vertical take-off and landing platform to be used for research activities in various fields including autonomous remote sensing, design and development of rapid prototype vehicles, flight control system design and high-fidelity modelling for simulation-based control system validation.

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19

Jay, R. L., and D. W. Burns. "Characteristics of the Diametral Resonant Response of a Shrouded Fan Under a Prescribed Distortion." Journal of Vibration and Acoustics 108, no. 2 (April 1, 1986): 125–31. http://dx.doi.org/10.1115/1.3269312.

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A comprehensive controlled study of the resonant vibratory structural response of a shrouded fan blade/disk due to known excitation was performed. A full circumferential definition of the inlet velocity field was obtained at five radial locations for three axial spacings and for four unique patterns of distortion and three mass flow rates. Harmonic analyses of the velocity patterns were used to establish a gust perturbation velocity normal to the blade chord. From these spanwise perturbation velocities, a normalized force parameter was established. In-vacuum, nonrotating testing of the fan assembly allowed identification of individual blade frequencies and system modes. This testing used strain gaging and holography to identify mistuning, damping and split factors for diametral patterns of the 3, 4, 5, and 6 diametral mode families. Dynamic strain signatures from rotating rig resonant responses were obtained for inlet flows having 3, 4, 5, and 6 distorted regions to simulate inlet struts. Groups of 1/4-in. rods were used to create these regions of distorted flow. System mode responses to these distortion patterns included occurrences of standing and traveling waves. Trends of gust perturbation force parameter and measured dynamic stress with varying axial gap, mass flow, and loading were established. The data collectively quantify the strong cause and effect relationship between force parameter and measured dynamic stress.

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20

Khelladi, S., C. Sarraf, F. Bakir, and R. Rey. "Study of a high rotational speed shrouded centrifugal fan: Aerodynamics and effects of a shroud-associated cavity on the performance." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 224, no. 5 (March 25, 2010): 691–700. http://dx.doi.org/10.1243/09576509jpe899.

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21

White, J. F., and O. O. Bendiksen. "Aeroelastic Behavior of Low-Aspect-Ratio Metal and Composite Blades." Journal of Engineering for Gas Turbines and Power 109, no. 2 (April 1, 1987): 168–75. http://dx.doi.org/10.1115/1.3240020.

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The aeroelastic stability of titanium and composite blades of low aspect ratio is examined over a range of design parameters, using a Rayleigh-Ritz formulation. The blade modes include a plate-type mode to account for chordwise bending. Chord-wise flexibility is found to have a significant effect on the unstalled supersonic flutter of low-aspect-ratio blades, and also on the stability of tip sections of shrouded fan blades. For blades with a thickness of less than approximately 4 percent of chord, the chordwise, second bending, and first torsion branches are all unstable at moderately high supersonic Mach numbers. For composite blades, the important structural coupling between bending and torsion cannot be modeled properly unless chordwise bending is accounted for. Typically, aft fiber sweep produces beneficial bending-torsion coupling that is stabilizing, whereas forward fiber sweep has the opposite effect. By using crossed-ply laminate configurations, critical aeroelastic modes can be stabilized.

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22

Menq, C. H., J. H. Griffin, and J. Bielak. "The Influence of a Variable Normal Load on the Forced Vibration of a Frictionally Damped Structure." Journal of Engineering for Gas Turbines and Power 108, no. 2 (April 1, 1986): 300–305. http://dx.doi.org/10.1115/1.3239903.

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An approximate procedure is developed for calculating the steady-state response of frictionally damped structures for which the normal load across the friction interface consists of a constant force and a force that varies linearly with the vibratory displacement. Such situations occur quite frequently in practice, as, for example; in the case of shrouded fan blades or in certain types of turbine-blade friction dampers. Depending on the magnitudes of the constant and the variable normal loads, the friction element will either stick, slip, or lift off at various intervals during a cycle of oscillation. The various possibilities are considered in the present study. Results from the approximate method are compared with “long-time” solutions obtained from a conventional transient analysis of the problem in order to assess the accuracy of the proposed procedure. As an application, the new method is then used to study the influence of the dynamic coupling on the optimization of the friction force in turbine blade dampers. Results show that the optimum friction force and the maximum amplitude of the response increase with dynamic coupling.

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23

Koskin, A. O., and V. G. Seleznev. "The study of shrouded fan vibration modes and frequencies on holograph and as a part of the engine on the test rig." VESTNIK of the Samara State Aerospace University, no. 5-2(47) (June 23, 2015): 109. http://dx.doi.org/10.18287/1998-6629-2014-0-5-2(47)-109-114.

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24

Sitaram, N., and G. Ch V. Sivakumar. "Effect of Partial Shrouds on the Performance and Flow Field of a Low-Aspect-Ratio Axial-Flow Fan Rotor." International Journal of Rotating Machinery 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/146969.

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The flow field at the rotor exit of a low aspect ratio axial flow fan for different tip geometries and for different flow coefficients is measured in the present study. The following configurations are tested: (1) rotor without partial shroud, designated as rotor (wos), (2) rotor with partial shroud, designated as rotor (ws), and (3) rotor with perforated (perforations in the shape of discrete circular holes) partial shroud, designated as rotor (wps). From steady state measurements, the performance of rotor (wps) is found to be the best. Both the rotors with partial shrouds have stalled at a higher flow coefficient compared to that of rotor (wos). From periodic flow measurements, it is concluded that the low velocity region near the tip section is considerably reduced with the use of partial shrouds with perforations. The extent of this low velocity region for both rotor (wos) and rotor (wps) increases with decreasing flow coefficient due to increased stage loading. This core of low momentum fluid has moved inwards of the annulus and towards the pressure side as the flow coefficient decreases. The extent of the low momentum fluid is smaller for rotor (wps) than that of rotor (wos) at all flow coefficients.

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25

Zahariea, Dănuţ. "Computer Aided Design of Centrifugal Fan Impeller Using CATIA Software." Applied Mechanics and Materials 809-810 (November 2015): 853–58. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.853.

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In this paper, the 3D model of the centrifugal fan impeller will be obtained using CAD software (CATIA). The blade will be obtained with 4 design methods: constant blade width and variable blade angle; hyperbolic blade width and variable blade angle; hyperbolic blade width and constant blade angle; linear blade width and variable blade angle. A comparative analysis of the weight of the blade, as well as of the weight of the rotor composed by cascade of blades, front and rear shrouds will be presented. Two materials have been used for all the elements of the centrifugal fan impeller: steel and aluminium. For computational purposes the MATLAB programming language will be used. The centrifugal fan blade will be designed as untwisted geometry with =2 reference curves (one on the rear shroud and the other one on the front shroud) with different numbers of reference points ={5, 10, 20, 30, 40, 50}. After running the MATLAB script file, the coordinates of reference points of the blade will be obtained for all 4 blade design methods. The transfer of the reference points coordinates from MATLAB workspace to CATIA has been performed using the automatic surface generation method, via an EXCEL macro file. This is the recommended method especially for a big number of reference points.

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26

Neal, D. R., and J. F. Foss. "The Application of an Aerodynamic Shroud for Axial Ventilation Fans." Journal of Fluids Engineering 129, no. 6 (January 2, 2007): 764–72. http://dx.doi.org/10.1115/1.2734206.

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An experimental investigation of an aerodynamic shroud applied to an axial ventilation fan system is reported. The aerodynamic shroud consists of a pressurized plenum and Coanda attachment surface, which also serves as the shroud for the fan. This combination delivers a curved surface wall jet of high momentum air into the tip region of the fan and subsequently into the downstream diffuser region. Simultaneous improvements of performance and efficiency were found for a specific fan geometry with an aerodynamic shroud system when compared with a standard production fan (no shroud) system. Overall, the addition of the aerodynamic shroud was able to increase the system flowrate by 34% while simultaneously improving the efficiency by 13%. A higher efficiency condition (+17%) was also found that resulted in a somewhat lower improvement in flow rate (+23%). These results clearly show that the best blade design for the aerodynamic shroud system is different than the best blade design for a system that does not include the aerodynamic shroud. Particle image velocimetry measurements made at the exit plane of the system’s diffuser provide insight into the mechanistic basis for the performance measurements.

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27

Wang, Yan, Quanlin Dong, and Yulian Zhang. "Meridional shape design and the internal flow investigation of centrifugal impeller." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, no. 23 (August 30, 2016): 4319–30. http://dx.doi.org/10.1177/0954406216667407.

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This paper describes an inverse design method for calculating the shape of meridional plane of centrifugal impeller. This design method permits the shroud and hub contours to be indirectly calculated by medial axis contour and constraint equations. The design process is computationally inexpensive and can conveniently modify the shroud and hub shapes as the design’s demand. Based on this design method, new constraint equations are used for a new shape design of meridional plane that lead to a uniform velocity distribution in the inlet of impeller. Numerical simulations are employed to investigate the fluid flows of centrifugal fan. After validation of the numerical strategy, the pressure and velocity distributions in centrifugal fan are illustrated. The numerical results show that the inlet performance is improved and the velocity distribution is more uniform. Furthermore, in order to understand the flow mechanism inside the centrifugal fan, the secondary flow in the blade passage and velocity distribution at the shroud and hub have been carried out a detailed investigation and study.

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28

Carroll, Jim K. "Low noise and rotating fan and shroud assembly." Journal of the Acoustical Society of America 94, no. 2 (August 1993): 1178. http://dx.doi.org/10.1121/1.406894.

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29

IKEDA, Masafumi, Junya TSUKADA, Satoshi KIKUCHI, Shigeki IMAO, and Yasuaki KOZATO. "205 Effect of Shroud Plates on Ducted Fan." Proceedings of Conference of Tokai Branch 2016.65 (2016): _205–1_—_205–2_. http://dx.doi.org/10.1299/jsmetokai.2016.65._205-1_.

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30

Morris, Scott C., and John F. Foss. "An Aerodynamic Shroud for Automotive Cooling Fans." Journal of Fluids Engineering 123, no. 2 (December 31, 2000): 287–92. http://dx.doi.org/10.1115/1.1359212.

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Results from an experimental investigation of an aerodynamic fan shroud are reported. The device was motivated by the relatively large (2.5 cm) tip clearance required in automotive cooling fans which are mounted to the engine. The shroud consists of a pressurized plenum and a Coanda attachment surface to deliver a jet of high momentum air into the tip clearance region. Both the performance and the efficiency for the initial system design were enhanced at higher flow rates, and degraded at lower flow rates. A small tuft was used to observe qualitative flow features in the near wake and tip clearance region of the fan. This information was used to create a modified design. The new geometry was tested and found to provide improved performance characteristics for a wider range of flow rate conditions.

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31

Lee, Yu-Tai, Vineet Ahuja, Ashvin Hosangadi, Michael E. Slipper, Lawrence P. Mulvihill, Roger Birkbeck, and Roderick M. Coleman. "Impeller Design of a Centrifugal Fan with Blade Optimization." International Journal of Rotating Machinery 2011 (2011): 1–16. http://dx.doi.org/10.1155/2011/537824.

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A method is presented for redesigning a centrifugal impeller and its inlet duct. The double-discharge volute casing is a structural constraint and is maintained for its shape. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. The present effort utilized a numerical optimization with experiential steering techniques to redesign the fan blades, inlet duct, and shroud of the impeller. The resulting flow path modifications not only met the pressure requirement, but also reduced the fan power by 8.8% over the baseline. A refined CFD assessment of the impeller/volute coupling and the gap between the stationary duct and the rotating shroud revealed a reduction in efficiency due to the volute and the gap. The calculations verified that the new impeller matches better with the original volute. Model-fan measured data was used to validate CFD predictions and impeller design goals. The CFD results further demonstrate a Reynolds-number effect between the model- and full-scale fans.

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32

Rama Krishna, S., A. Rama Krishna, and K. Ramji. "An experimental study on the reduction of motor-fan noise by modification of the blade and shroud configuration." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 2 (February 1, 2010): 315–20. http://dx.doi.org/10.1243/09544062jmes1869.

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The noise reduction (NR) of fans used for cooling electric motors is one of the key parameters in the design of a motor fan. In the authors’ previous paper, aeroacoustic analysis (which is based on unsteady computational fluid dynamics results) was performed for the baseline fan to know its sound level. To further find a better blade shape from an NR point of view, aeroacoustic analysis on various blade profiles from the NACA-63 and NACA-65 series was conducted. In this work, an experimental study on the baseline fan and three redesigned composite material fans for the low-noise fan is performed. The experimental parameters under investigation are better aerofoil-shape blade cross-section, using inlet bell-mouth entry, using composite materials, reducing the number of blades, using uneven blade spacing, making it a mixed flow fan, using backward-skewed blade design and reducing tip clearance. From the noise measurements in a semi-anechoic chamber for Fan-2, it is observed that the overall NR was 12.8 dB(A) compared with the baseline fan. It is observed that a mixed flow fan consisting of seven evenly spaced blades of NACA 65-010 aerofoil cross-section with backward swept shape and fabricated with glass and jute fibre produced the low-noise fan design at the fan operating point.

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33

Heinemann, Till, and Stefan Becker. "Axial Fan Performance under the Influence of a Uniform Ambient Flow Field." International Journal of Rotating Machinery 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/6718750.

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In their application to air-cooled condensers, axial fans are often subject to the detrimental influence of ambient flow fields at their inlet or outlet. While effects have been investigated mostly under perpendicular cross-flow conditions on fans operating as part of an array in their target design point, this study aims at examining the integral influence of uniform ambient flow fields on a single axial fan over a wide operating range. For this purpose, a wind tunnel fan test rig has been designed and assessed. Multiple angles between uniform ambient flow field and fan axis are examined in their integral influence on the characteristic curve of two distinct industrial axial fans with varying inlet modifications. Increasingly with the fan flow rate, perpendicular inlet cross-flow was found to always have a detrimental influence on fan performance. The straight bladed fan reacted less sensitively than the forward skewed fan, and the adverse cross-flow influence could be reduced with an inlet guard grille and with short conical shroud extensions. Cross-flow at the fan outlet showed potential static fan pressure increases at low flow rates.

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34

Tsukada, Junya, Shota Fujine, Satoshi KIKUCHI, Shigeki IMao, and Yasuaki KOZATO. "Influence of Shroud and Plates on Flow from Propeller Fan." Proceedings of Conference of Tokai Branch 2017.66 (2017): 408. http://dx.doi.org/10.1299/jsmetokai.2017.66.408.

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35

Wang, Song Ling, Zhe Sun, and Zheng Ren Wu. "Investigation of Strength in G4-73 Type Centrifugal Fan Impeller." Advanced Materials Research 383-390 (November 2011): 5669–73. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.5669.

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For the large centrifugal fan impeller, its working condition generally is bad, and its geometry generally is complex. So its displacements and stresses distribution are also complex. In this paper, we can obtain the fan impeller’s displacements and stresses distribution accurately through numerical simulation in G4-73 type centrifugal fan impeller using the finite element method software ANSYS. The calculation result shows that the maximum total displacement of the impeller is m, it occurs on the position of the half of the blade near the outlet of the impeller; and the maximum equivalent stress of the impeller is 193 MPa, it occurs on the contacted position of the blade and the shroud near inlet of the impeller. Furthermore, check the impeller strength, the result shows that the strength of the impeller can meet the requirement.

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36

Wasala, Sahan, Lon Stevens, Raye Sosseh, and Tim Persoons. "Numerical analysis of acoustic noise from an electronic cooling fan at flow disturbed by an external obstacle." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 3 (February 1, 2023): 4486–93. http://dx.doi.org/10.3397/in_2022_0645.

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Axial cooling fans are widely used in data center dense Hard Disk Drive (HDD) storage systems. However, these fans emit high noise levels and degrade HDD performance at certain frequencies. Flow at the fan's inlet can be highly turbulent due to the wake generated by fan components such as struts, finger guards, stators/guide vanes, shrouds, and other external system components such as connectors and mounts, power cables and components, circuits etc. The wake-fan interaction also causes high tonal noise. Therefore a proper understanding of this noise mechanism will help optimize the cooling system in next-generation high-performance HDD enclosure systems. This paper focuses on studying this phenomenon using numerical simulations of a typical data center cooling fan combined with various simplified strut geometries as the obstacle. The high-fidelity Computational Fluid Dynamic (CFD) method, Large Eddy Simulation (LES), was used to obtain a transient flow field. The Ffowcs-Williams and Hawkings acoustic analogy was used to predict far-field noise.

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37

Petrov, A. P., S. N. Sinitsyn, and S. N. Bannikov. "Design features of fan assembly in automobiles." Izvestiya MGTU MAMI 10, no. 3 (September 15, 2016): 50–57. http://dx.doi.org/10.17816/2074-0530-66917.

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Nowadays in the engine cooling system and in air-conditioning system of passenger compartment and cabin of tractor is applied a great variety of designs of fan units for the supply of cooling air. A distinctive feature of fan units of automobiles is that they need not only to supply cooling air, but also must make efficient use of air flow. This is not an easy task, because these two functions are almost always in conflict. The problem becomes even more complicated when a car air conditioner is installed. Efficiency factor of the incident flow is higher than the efficiency of the fan. It is therefore necessary to use more efficient the incoming air flow. The article analyzes the most common fan assemblies of automobiles used for the operation of the engine cooling and passenger compartment air conditioning system. Its strengths and weaknesses were evaluated. There were evaluated the most important characteristics: the effectiveness of the fan use, the rational use of air flow when the vehicle is moving, mass-dimensional characteristics and the noise produced by the fans in their work. The conclusions and recommendations for improving the fan installations were given. When choosing one or another variant of the fan assembly it is needed to take into account the features of the automobile design. High efficiency of fan can be obtained when the fan shroud has a full coverage of the radiator. In this case, for rational use of incoming flow is necessary to install in the fan cover the valves of a large cross-section in contrast to traditional, these valves must be driven to forced opening and closing.

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38

Kjo¨rk, A., and L. Lo¨fdahl. "Hot-Wire Measurements Inside a Centrifugal Fan Impeller." Journal of Fluids Engineering 111, no. 4 (December 1, 1989): 363–68. http://dx.doi.org/10.1115/1.3243654.

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Measurements of the three mean velocity components and five of the Reynolds stresses have been carried out in the blade passage of a centrifugal fan impeller. The impeller was of ordinary design, with nine backward curved blades, and all measurements were carried out at the design flow rate. The mean velocity measurements show that the flow can be characterized as an attached flow with almost linearly distributed velocity profiles. However, in a region near the suction side close to the shroud a low velocity region is created. From the turbulence measurements it can be concluded that relatively low values of the turbulent stresses are predominating in the center region of the channel. Closer to the walls higher values of the normal as well as shear stresses are noted.

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39

Vasudeva Karanth, K., and N. Yagnesh Sharma. "Numerical analysis of a centrifugal fan for performance enhancement using boundary layer suction slots." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 8 (January 12, 2010): 1665–78. http://dx.doi.org/10.1243/09544062jmes1990.

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Flow in centrifugal fans tends to be in a state of instability with flow separation zones on both the suction surface and the front shroud. The overall efficiency of the diffusion process in a centrifugal fan could be enhanced by judiciously introducing the boundary layer suction slots. With easy accessibility of computational fluid dynamics (CFD) as an analytical tool, an extensive numerical whole field analysis of the effect of boundary layer suction slots in discrete regions of suspected separation points is possible. This article attempts to explore the effect of boundary layer suction slots corresponding to various geometrical locations on the impeller as well as on the diffuser. The analysis shows that the suction slots located on the impeller blade near to its trailing edge appreciably improves the static pressure recovery across the fan. Slots provided at a radial distance of 30 per cent from the leading edge of the diffuser vane also significantly contribute to the static pressure recovery across the fan.

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40

Azzam, Tarik, Richard Paridaens, Florent Ravelet, Sofiane Khelladi, Hamid Oualli, and Farid Bakir. "Experimental investigation of an actively controlled automotive cooling fan using steady air injection in the leakage gap." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, no. 1 (January 12, 2017): 59–67. http://dx.doi.org/10.1177/0957650916688120.

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In an axial fan, a leakage flow driven by a pressure gradient between the pressure side and the suction side occurs in the gap between the shroud and the casing. This leakage flow is in the opposite direction to the main flow and is responsible for significant energy dissipation. Therefore, many authors have worked to understand this phenomenon in order to reduce these inherent energy losses. Up to now, most of the studies reported in the literature have been passive solutions. In this paper, an experimental controlling strategy is suggested to reduce the leakage flow rate. To this end, a fan with hollow blades and a specific drive system were designed and built for air injection. Air is injected in the leakage gap at the fan periphery. The experiment was performed for three rotation speeds, five injection rates and two configurations: 16 and 32 injection holes on the fan’s circumference. The experimental results of this investigation are presented in this article.

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41

Ottersten, Martin, Hua-Dong Yao, and Lars Davidson. "Inlet Gap Influence on Low-Frequency Flow Unsteadiness in a Centrifugal Fan." Aerospace 9, no. 12 (December 19, 2022): 846. http://dx.doi.org/10.3390/aerospace9120846.

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In this study, unsteady low-frequency characteristics in a voluteless low-speed centrifugal fan operating at a high mass flow rate are studied with improved delayed detached eddy simulation (IDDES). This study is motivated by a recent finding that the non-uniformly distributed pressure inside this type of fan could be alleviated by improving the gap geometry. The present simulation results show that the velocity magnitudes of the gap have distinct low and high regions. Intensive turbulent structures are developed in the low-velocity regions and are swept downstream along the intersection between the blade and shroud, on the pressure side of the blade. Eventually, the turbulence gives rise to a high-pressure region near the blade’s trailing edge. This unsteady flow behavior revolves around the fan rotation axis. Additionally, its period is 5% of the fan rotation speed, based on the analysis of the time history of the gap velocity magnitudes and the evolution of the high-pressure region. The same frequency of high pressure was also found in previous experimental measurements. To the authors’ knowledge, this is the first time that the trigger of the gap turbulence, i.e., the unsteady local low velocity, has been determined.

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42

NAKASONE, Nobuo, Kohei IWAMOTO, Kazuya KUSANO, Soichiro TABATA, Masato FURUKAWA*, and Masakazu ISHIKAWA. "J051035 Effect of Tangential Lean Blade in Propeller Fan With Ring Shroud." Proceedings of Mechanical Engineering Congress, Japan 2011 (2011): _J051035–1—_J051035–5. http://dx.doi.org/10.1299/jsmemecj.2011._j051035-1.

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43

Pereira, Michaël, Florent Ravelet, Kamel Azzouz, Tarik Azzam, Hamid Oualli, Smaïne Kouidri, and Farid Bakir. "Improved Aerodynamics of a Hollow-Blade Axial Flow Fan by Controlling the Leakage Flow Rate by Air Injection at the Rotating Shroud." Entropy 23, no. 7 (July 8, 2021): 877. http://dx.doi.org/10.3390/e23070877.

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Axial flow fans are used in many fields in order to ensure the mass and heat transfer from air, chiefly in the heating, ventilation and air conditioning industry (HVAC). A more proper understanding of the airflow behavior through the systems is necessary to manage and optimize the fan operation. Computational fluid dynamics (CFD) represents a real tool providing the ability to access flow structures in areas that measuring equipment cannot reach. Reducing the leakage flow rate, inherent in operation, by synthetic-jet techniques improves performance. This paper presents the CFD results performed on a hollow blade fan developed by our team. The leakage flow is controlled by blowing air from 16 designated circular holes and arranged on the fan shroud. We discuss the results for two rotational speeds (1000 and 2000 rpm) and two injection rates (400 and 800 L/min). The numerical results consistent with the experimental show, for the low rotation speed and high injection ratio, significant gains in power (53%), torque (80%) and leakage flow rate (80%).

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Morinushi, Ken. "The Influence of Geometric Parameters on F. C. Centrifugal Fan Noise." Journal of Vibration and Acoustics 109, no. 3 (July 1, 1987): 227–34. http://dx.doi.org/10.1115/1.3269425.

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In this report, through experiments the influence of five major geometric parameters on noise and aerodynamic performance of forward curved (F.C.) centrifugal fans was studied. The parameters considered are: (1) width-inner diameter ratio of impeller, (2) axial clearance between the fan inlet nozzle and the impeller shroud plate, (3) blade-setting angle, (4) blade pitch-chord ratio, and (5) spiral extension index of the scroll. Noise characteristics were evaluated by means of the specific noise level (A-weighted) at every operating point except the surging region. The optimal values for the parameters to realize low noise are discussed. Design diagrams for low noise F.C. centrifugal fans are shown.

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45

Jang, Choon-Man, Masato Furukawa, and Masahiro Inoue. "Analysis of Vortical Flow Field in a Propeller Fan by LDV Measurements and LES—Part I: Three-Dimensional Vortical Flow Structures." Journal of Fluids Engineering 123, no. 4 (July 21, 2001): 748–54. http://dx.doi.org/10.1115/1.1412565.

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Three-dimensional structures of the vortical flow field in a propeller fan with a shroud covering only the rear region of its rotor tip have been investigated by experimental analysis using laser Doppler velocimetry (LDV) measurements and by numerical analysis using a large eddy simulation (LES) in Part I of the present study. The propeller fan has a very complicated vortical flow field near the rotor tip compared with axial fan and compressor rotors. It is found that three vortex structures are formed near the rotor tip: the tip vortex, the leading edge separation vortex, and the tip leakage vortex. The tip vortex is so strong that it dominates the flow field near the tip. Its formation starts from the blade tip suction side near the midchord. Even at the design condition the tip vortex convects nearly in the tangential direction, thus impinging on the pressure surface of the adjacent blade. The leading edge separation vortex develops close along the tip suction surface and disappears in the rear region of the rotor passage. The tip leakage vortex is so weak that it does not affect the flow field in the rotor.

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Jackson, M. D., and A. K. Agrawal. "Active Control of Combustion for Optimal Performance." Journal of Engineering for Gas Turbines and Power 121, no. 3 (July 1, 1999): 437–43. http://dx.doi.org/10.1115/1.2818492.

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Combustion-zone stoichiometry and fuel-air premixing were actively controlled to optimize the combustor performance over a range of operating conditions. The objective was to maximize the combustion temperature, while maintaining NOx within a specified limit. The combustion system consisted of a premixer located coaxially near the inlet of a water-cooled shroud. The equivalence ratio was controlled by a variable-speed suction fan located downstream. The split between the premixing air and diffusion air was governed by the distance between the premixer and shroud. The combustor performance was characterized by a cost function evaluated from time-averaged measurements of NOx and oxygen concentrations in products. The cost function was minimized by the downhill simplex algorithm employing closed-loop feedback. Experiments were conducted at different fuel flow rates to demonstrate that the controller optimized the performance without prior knowledge of the combustor behavior.

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47

Jang, Choon-Man, Masato Furukawa, and Masahiro Inoue. "Analysis of Vortical Flow Field in a Propeller Fan by LDV Measurements and LES—Part II: Unsteady Nature of Vortical Flow Structures Due to Tip Vortex Breakdown." Journal of Fluids Engineering 123, no. 4 (July 21, 2001): 755–61. http://dx.doi.org/10.1115/1.1412566.

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The unsteady nature of vortex structures has been investigated by a large eddy simulation (LES) in a propeller fan with a shroud covering only the rear region of its rotor tip. The simulation shows that the tip vortex plays a major role in the structure and unsteady behavior of the vortical flow in the propeller fan. The spiral-type breakdown of the tip vortex occurs near the midpitch, leading to significant changes in the nature of the tip vortex. The breakdown gives rise to large and cyclic movements of the tip vortex, so that the vortex impinges cyclically on the pressure surface of the adjacent blade. The movements of the tip vortex cause the leading edge separation vortex to oscillate in a cycle, but on a small scale. The movements of the vortex structures induce high-pressure fluctuations on the rotor blade and in the blade passage.

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48

Smith, L. H. "M. J. Hartmann Memorial Session Paper: NASA/GE Fan and Compressor Research Accomplishments." Journal of Turbomachinery 116, no. 4 (October 1, 1994): 555–69. http://dx.doi.org/10.1115/1.2929445.

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Fan and compressor research projects carried out at GE Aircraft Engines under NASA sponsorship are described in this paper. Four 1400-fps-tip-speed rotors designed with different airfoil shapes were found to have comparable stall lines but different efficiency trends. A stator placed behind one of these affected its performance somewhat. Adjustments of variable camber inlet guide vanes placed ahead of a 1500fps stage were found to affect its pumping capability without much affecting its stall line. For the Quiet Engine Program (QEP), two 1160-fps fans and one 1550-fps fan were tested. Development of the high-speed fan revealed the effects on performance of airfoil shape and part-span shroud blockage. The 950-fps variable-pitch fan for the Quiet Clean Short-haul Experimental Engine (QCSEE) demonstrated reverse thrust capabilities and a novel method of avoiding large core inlet pressure losses during reverse thrust operation. The 1350-fps Energy Efficient Engine (E3) fan demonstrated excellent performance with a novel quarter-stage arrangement that eliminated the need for interspool bleed while giving good dirt removal potential. The E3 compressor program employed Low Speed Research Compressor tests to identify the most appropriate blading type. High-speed rig tests and engine tests were then used to develop this 23:1-spool-pressure-ratio compressor. Research on casing boundary layer control through bleeding and blowing led to the discovery that irregular casing geometries usually give stall line enhancements even without auxiliary air circuits. Some of the resulting casing treatment research is reported herein. Instances in which NASA-sponsored research has affected GE Aircraft Engine products are pointed out.

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49

Strazisar, A. J. "Investigation of Flow Phenomena in a Transonic Fan Rotor Using Laser Anemometry." Journal of Engineering for Gas Turbines and Power 107, no. 2 (April 1, 1985): 427–35. http://dx.doi.org/10.1115/1.3239743.

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Several flow phenomena, including flow field periodicity, rotor shock oscillation, and rotor shock system geometry have been investigated in a transonic low aspect ratio fan rotor using laser anemometry. Flow periodicity is found to increase with increasing rotor pressure rise and to correlate with blade geometry variations. Analysis of time-accurate laser anemometer data indicates that the rotor shock oscillates about its mean location with an amplitude of 3–4 percent of rotor chord. The shock surface is nearly two-dimensional for levels of rotor pressure rise at and above the peak efficiency level but becomes more complex for lower levels of pressure rise. Spanwise shock lean generates radial flows due to streamline deflection in the hub-to-shroud streamsurface.

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Isomura, K., and M. B. Giles. "A Numerical Study of Flutter in a Transonic Fan." Journal of Turbomachinery 120, no. 3 (July 1, 1998): 500–507. http://dx.doi.org/10.1115/1.2841746.

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The bending mode Flutter of a modern transonic fan has been studied using a quasi-three-dimensional viscous unsteady CFD code. The type of flutter in this research is that of a highly loaded blade with a tip relative Mach number just above unity, commonly referred to as transonic stall flutter. This type of Flutter is often encountered in modern wide chord fans without a part span shroud. The CFD simulation uses an upwinding scheme with Roe’s third-order flux differencing, and Johnson and King’s turbulence model with the later modification due to Johnson and Coakley. A dynamic transition point model is developed using the en method and Schubauer and Klebanoff’s experimental data. The calculations of the flow in this fan reveal that the source of the flutter of IHI transonic fan is an oscillation of the passage shock, rather than a stall. As the blade loading increases, the passage shock moves forward. Just before the passage shock unstarts, the stability of the passage shock decreases, and a small blade vibration causes the shock to oscillate with a large amplitude between unstarted and started positions. The dominant component of the blade excitation force is due to the foot of the oscillating passage shock on the blade pressure surface.

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