Articoli di riviste: "Fans, Mechanical"

1

Langston, Lee S. "Focus on Fans". Mechanical Engineering 132, n. 08 (1 agosto 2010): 51. http://dx.doi.org/10.1115/1.2010-aug-7.

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This article discusses ongoing research in the area of turbofans used in jet engines. P&W’s gear facilities in Middletown Connecticut have been developing the fan gearbox over a period of 20 years. The company has a long history of gearbox experience associated with their very popular turboprop gas turbines at Pratt & Whitney Canada. Field tests have shown that the geared turbofan has a much lower level of noise. Currently, some airlines have as much as 35–60% of their operating costs in jet fuel use. If the geared fan engine does indeed significantly reduce fuel use, this improvement in fan performance will be hard for the competition to beat. Another way to improve fan performance is to change the pitch of fan blades, during an aircraft flight cycle. Rotating Composite Technologies, a small firm in Kensington, Conn. has also come up with a unique patented design for the variable pitch fan that promises to overcome the deficiencies of those tested in the 1990s.

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Brown, Alan S. "From Whales to Fans". Mechanical Engineering 133, n. 05 (1 maggio 2011): 24–29. http://dx.doi.org/10.1115/1.2011-may-1.

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This article discusses a story about a man named Fish who noticed something unusual about whale flippers and who, after nearly 30 years, turned it into a technology platform. This technology takes its inspiration from the natural design of the bumps, or tubercles, on humpback whale flippers. The 24-foot-diameter fans, based on tubercle technology, use half the number of blades and move 25% more air and consume 25% less power than fans with conventional blades turning at the same speed. After thousands of years of hiding in plain sight, tubercles are emerging as a real, if limited, technology platform. Research has shown tubercles work only on thick, tapered wings operating in a very narrow laminar-to-turbulent transition regime. Whale-inspired fans are already available, and wind and tidal power blades could be the next.

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Chen, P., M. Soundra-Nayagam, A. N. Bolton e H. C. Simpson. "Unstable Flow in Centrifugal Fans". Journal of Fluids Engineering 118, n. 1 (1 marzo 1996): 128–33. http://dx.doi.org/10.1115/1.2817490.

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Rotating stall and the inlet vortex in centrifugal fans with inlet vane control has been studied. The advances in stall research in aero-engine compressors are discussed. The present study shows that stall in centrifugal fans can be quite different from that in axial compressors, in that stall can occur in a progressive and intermittent fashion. The study also shows that a discontinuity in the fan characteristic is not necessarily accompanied by rotating stall, unlike the axial machines. Experimental results indicate that the positive prewhirl created by inlet vanes tends to delay the occurrence of stall. Also, dorsal fin devices that are used to control the inlet vortex do not seem to affect the stall point unfavorably. The inlet vortex frequency was found to invariably exhibit a linear relation with the flow rate even when dorsal fins were used. This offers a practical method to distinguish between the inlet vortex and rotating stall.

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Wright, T., e W. E. Simmons. "Blade Sweep for Low-Speed Axial Fans". Journal of Turbomachinery 112, n. 1 (1 gennaio 1990): 151–58. http://dx.doi.org/10.1115/1.2927413.

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The available literature on aerodynamic and acoustic properties of axial fans with swept blades is presented and discussed with particular emphasis on noise mechanisms and the influence of high-intensity inlet turbulence on “excess” noise. The acoustic theory of Kerschen and Envia for swept cascades is applied to the problem of axial fan design. These results are compared to available data and a provisional model for specifying sweep angles is presented. The aerodynamic performance theory for swept-bladed rotors of Smith and Yeh is adapted for use in designing low-speed axial fans. Three prototype fans were designed using the resultant computer codes. One is a baseline fan with blade stocking lines radially oriented, and two are fans having swept blades of increasingly greater forward sweep. Aerodynamic testing shows that performance of the fans lies within a band width of about ± 2 percent of volume flow rate and pressure rise predictions in the region of design performance, effectively validating the design procedure for selection of the blading parameters. Noise testing of the fans was carried out and the results show an average noise reduction for the swept-bladed fans of about 7 dBA overall, and a reduction of pure tone noise at blade-pass frequency of about 10 dB compared to the zero-sweep baseline model, in close agreement with the theory of Kerschen and Envia.

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V.S., Dmitriev, Kostyuchenko T.G., Minkov L.L., Derdiyashchenko V.V. e Panfilov D.S. "VIBROACTIVITY OF LOW-NOISE FANS". Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, n. 68 (2020): 61–71. http://dx.doi.org/10.17223/19988621/68/6.

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Low-noise fans are widely used in the sphere of human life for sanitary and technological purposes. Creation of low-noise fans is currently an advanced scientific and technical area. In some fields of their application, reduced vibrations and noises are of paramount importance not only in terms of sanitation and health, but also from a scientific point of view. This work presents a comparison of the quality of low-noise fan development depending on the selected resistance type. The efficiency of the damping of mechanical system (a low-noise fan) vibrations according to the type of resistance moment used is confirmed analytically and practically. Nowadays, a number of fan types implemented in hundreds of designs have been developed and are in service. In this work, the whole variety of the produced nomenclature of low-noise fans is reduced to two basic types – axial and radial. The paper reports that to ensure minimum noise in the operating mode of the low-noise fans presented in the work, a wideband vibration damper is needed as a required functional unit, and the walls of the fan housing should be sandwich-like with layers made of sound absorbing, sound insulating, and vibration damping materials.

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Beiler, M. G., e T. H. Carolus. "Computation and Measurement of the Flow in Axial Flow Fans With Skewed Blades". Journal of Turbomachinery 121, n. 1 (1 gennaio 1999): 59–66. http://dx.doi.org/10.1115/1.2841234.

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A numerical analysis of the flow in axial flow fans with skewed blades has been conducted to study the three-dimensional flow phenomena pertaining to this type of blade shape. The particular fans have a low pressure rise and are designed without stator. Initial studies focused on blades skewed in the circumferential direction, followed by investigations of blades swept in the direction of the blade chord. A Navier–Stokes code was used to investigate the flow. The simulation results of several fans were validated experimentally. The three-dimensional velocity field was measured in the fixed frame of reference with a triple sensor hot-film probe. Total pressure distribution measurements were performed with a fast response total pressure probe. The results were analyzed, leading to a design method for fans with swept blades. Forward swept fans designed accordingly exhibited good aerodynamic performance. The sound power level, measured on an acoustic fan test facility, improved.

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Zhao, Wenxuan, Wei Ye, Qianru Zhang e Xu Zhang. "Simulations on arrangements of induced jet-fans as auxiliary ventilation for a mechanical ventilated space with openings". E3S Web of Conferences 111 (2019): 01036. http://dx.doi.org/10.1051/e3sconf/201911101036.

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Underground garages, indoor stadiums, or more commonly used seagoing ships, can be used as large multi-purpose spaces, which are suitable for the carriage of a wide range of cargoes, as well as evacuation of people at overseas. The indoor environment in a multi-purpose cabin usually varies, in terms of pollutant emissions, hazardous levels and the corresponding ventilation requirements. A possible solution, in addition to a single regular HVAC system, is to use multiple induced jet fans. However, to pre-determine a universal design of fans, e.g., numbers, locations, directions, angles and flowrates, etc., may not be practical. In this preliminary work, methods to design the auxiliary ventilation system were discussed. The heat sources are located in the four corners on the floor. CFD method is used to further study the effects of six regular and four irregular arrangements of a 2×2 array of fans on local heat dilution with or without natural ventilation (e.g., additional openings in the space). Heat exhaust efficiency is used to evaluate the effects of different arrangements of fans on local heat dilution. The results show that adjustable ventilation using induced fans would be useful to provide various airflow distribution for a large space and the dilution of the heat can be improved and the areas of high temperature inside the space can be reduced. Furthermore, the heat exhaust efficiency would be higher and the induced fans have a more significant effect, especially when additional natural ventilation is available.

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Chun, Guo, Wang Mingnian e Tang Zhaozhi. "A Study on Surge and Stall under the Interaction of Parallel Axial flow fan in Tunnel". Noise & Vibration Worldwide 42, n. 11 (dicembre 2011): 9–14. http://dx.doi.org/10.1260/0957-4565.42.11.9.

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In the ventilation design for tunnels above 10km, an axial flow fan of great power needs to be set in ventilation shafts. There are few provisions on the setting modes and less discussion of parallel axial flow fan mode in the Specifications for Design of Ventilation and Lighting of Highway Tunnels. All of these bring a lot of difficulties about the axial fan selection, layout and control design. There is no specialized research on axial flow fan for tunnels and no studies on surge and stall under the interaction of parallel axial flow fan in tunnel in spite of the more and more application of parallel axial flow fan. So, this paper conducts a study on surge and stall under the interaction of parallel axial flow fan in tunnels. Through the study on the operating principle and analysis of parallel axial flow fan, we can know that the noise will increase suddenly, which will in turn result in fan vibration and running instability once the stall occurs. When a fan surges, the air volume and pressure, the motor current will fluctuate sharply, which brings significantly increased vibration and noise. At the same time, the rotary blade and the shell are subject to considerable stress effects and the fan will possibly suffer from great damage. The surge will occur in the unstable zone of axial fan performance curve. The strong pulsation and periodic oscillation of the air flow will increase the noise, which is a serious damage to the fan. So an axial fan should avoid this zone in running. With two axial flow fans of the same power parallel, the mutual influence is not very great. Therefore this research will focus on the efficiency in the case of two fans with a high and a low power parallel. Stall will occur if the outside pressure is greater than the outlet pressure. Once the stall happens, the noise will increase suddenly, which will in turn result in fan vibration and running instability. When two fans parallel, i.e. when the power ratio of the parallel fans is over 5.3, the possibility of the small fan's stall is high, otherwise it is small. With regard to the running efficiency of parallel axial flow fans and the starting safety, it is better to parallel two fans, and the fans with adjustable movable vanes or frequency control or the ordinary nonadjustable fans can be used.

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Bamberger, Konrad, e Thomas Carolus. "Efficiency limits of fans". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, n. 5 (27 settembre 2019): 739–48. http://dx.doi.org/10.1177/0957650919876838.

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The purpose of this work is to identify upper efficiency limits of industrial fans such as axial rotor-only fans, axial with guide vanes, centrifugal rotor-only and centrifugal with volute. The efficiency limit is always a function of the class, the design point within the class and the definition of efficiency (total-to-static and total-to-total). The characteristic Reynolds number is another relevant parameter. First, based on analytical and empirical loss models, a theoretical efficiency limit is estimated. A set of idealizing assumptions in the loss models yields efficiencies which are assumed to be an insuperable limit but may be unrealistically high. Second, more realistic efficiency limits are estimated using a computational fluid dynamics-based optimization scheme, seeking for the best designs and hence the maximum achievable efficiencies in all classes. Given the self-imposed constraints in the geometrical parameter space considered, the thus-obtained practical efficiency limits can only be exceeded by admitting more complex geometries of the fans.

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Suzuki, Yasuyoshi. "Replacement of Existing Fans with High-Efficiency Fans for Energy Saving." JAPAN TAPPI JOURNAL 53, n. 11 (1999): 1417–22. http://dx.doi.org/10.2524/jtappij.53.1417.

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Yen, S. C., e Frank K. T. Lin. "Exit Flow Field and Performance of Axial Flow Fans". Journal of Fluids Engineering 128, n. 2 (19 settembre 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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Gu, Fengwei, Meng Yang, Zhichao Hu, Yanhua Zhang, Chong Zhang e Shenying Wang. "Experiment and Optimization of High-Efficiency Mechanical Separation of Peanut Seedlings and Residual Film Based on Suspension Velocity". Transactions of the ASABE 64, n. 4 (2021): 1381–89. http://dx.doi.org/10.13031/trans.14512.

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HighlightsAn efficient method for separating peanut seedlings and residual film harvested from film-mulched peanut was proposed, and the mechanism was optimized.The relationships between the suspension velocity and moisture content of different shredded materials were studied.Four-factor, three-level Box-Behnken experiments were carried out and analyzed, and the optimal parameter combination was determined.A validation test was carried out to verify the rationality and accuracy of the optimized regression model.Abstract. To address the problems of lower residual film removal and higher material loss in the forage utilization of peanut seedlings wrapped in residual film, this study explored the relationships between the suspension velocity and moisture content of different shredded materials derived from peanut seedlings and conducted performance tests and parameter optimization for a machine that uses peanut seedlings as forage material. Four-factor, three-level Box-Behnken experiments were designed using the rotational speeds of the shredding shaft, upper fans, and lower fans and the frequency of the vibrating sieve as test factors, and using the residual film removal rate and material loss rate as response values. The test results indicated that the suspension velocity of the shredded materials showed a quadratic relationship with moisture content. The performance tests showed that the significance sequence of the test factors for the residual film removal rate was: rotational speed of the lower fans, rotational speed of the upper fans, rotational speed of the shredding shaft, and frequency of the vibrating sieve. The significance sequence for the material loss rate was: rotational speed of the lower fans, rotational speed of the shredding shaft, frequency of the vibrating sieve, and rotational speed of the upper fans. The parameter optimization and validation test showed that the residual film removal rate was 92.71% and the material loss rate was 8.19% when the rotational speeds of the shredding shaft, upper fans, and lower fans were 1650, 770, and 665 rpm, respectively, and the frequency of the vibrating sieve was 4 Hz. The relative errors between the validation test results and the predicted values from the regression models were less than 3%, which suggests that the regression models are reliable. This study provides a reference for the forage utilization of peanut seedlings harvested from film-mulched peanut and provides a reference for determining the optimal working parameters of forage processing machines. Keywords: Agricultural machinery, Box-Behnken experiment, Optimization, Peanut film-seedling separation, Suspension velocity.

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Tan, J. J., D. T. Qi e T. F. Luo. "A new approach to the calculation of Euler work for centrifugal fan impellers". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, n. 7 (30 marzo 2009): 1591–96. http://dx.doi.org/10.1243/09544062jmes1396.

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In a conventional one-dimensional scheme design of centrifugal fans and compressors, it is assumed that there is no flow prewhirl at the impeller inlet when the inlet guide vane is absent. However, many experiments have proved that the flow prewhirl does exist at the inlet of centrifugal impellers. This results in an error in the design of centrifugal fans and compressors. In this study a new method is presented to calculate the Euler work of centrifugal impellers considering the presence of an inlet flow prewhirl in the case without the inlet guide vane. Stodola's approach dealing with the slip velocity at the impeller outlet is applied to the impeller inlet. A new formula for Euler work calculation is deduced to evaluate the effect of the inlet prewhirl. The new formula has been applied to 33 industrial centrifugal fans and the calculated results have been compared with the experimental data of these fans. The comparison shows that the new formula is more accurate in most cases than the original formula without consideration of the inlet flow prewhirl, and the accuracy has been improved by more than 10 per cent on average. The aim of this study is to improve the accuracy of the one-dimensional scheme design of centrifugal fans and to provide a reference for a similar research.

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Bianchi, S., A. Corsini, F. Rispoli e A. G. Sheard. "Detection of aerodynamic noise sources in low-speed axial fans with tip end-plates". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, n. 6 (18 marzo 2009): 1379–92. http://dx.doi.org/10.1243/09544062jmes1277.

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This article reports on the use of modified blade-tip configurations designed with a view to passive noise control in low-speed fans for compact cooling units. The addition of end-plates at the tip of a datum fan blade is shown to have a positive influence on the fan's rotor-only aero-acoustic signature. The aerodynamic effects of the modified blade tips are experimentally tested in a fully ducted configuration in the near field and far field using a correlation technique. The nature of the flow mechanisms in the blade-tip region are correlated with the specific end-plate design features and their role in the creation of overall acoustic emissions is clarified. The noise emitted by the fans is analysed in terms of coherent vortex structures, tip-leakage flow, and noise sources. Differences in human perception of the noise emitted to the environment are also investigated using a dot-pattern visualization. The study concludes that the modified tip configurations have a marked effect on tip-leakage vortex formation by altering the near-wall fluid paths on blade surfaces. The reduction in rotor noise emission is correlated with the control of tip-leakage flows produced by the tip end-plates.

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Aiken, K. Damon, Ajay Sukhdial, Richard Campbell e Aubrey Kent. "Investigating Sport Fan Attitudes Towards Tanking: Th e Role of Values-Based Connections". Sport Marketing Quarterly 29, n. 4 (dicembre 2020): 256–68. http://dx.doi.org/10.32731/smq.294.122020.02.

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While previous research has found support for the existence of tanking in professional sport, attitudinal complexities surrounding the phenomenon have yet to be investigated. This study utilized Amazon’s Mechanical Turk service to obtain a national sample of National Basketball Association (NBA) fans. The sample contained fans of all thirty NBA teams. Respondents provided data regarding their overall attitudes toward tanking as well as their underlying old school values, time-oriented values, and ethics-based values. Results indicate that fans have a relatively strong dislike for perceived tanking and that a team’s win-loss record has very little influence on fans’ generally negative attitudes. Furthermore, these attitudes appear to be guided by fan values.

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Sheard, A. G., e A. Corsini. "The Mechanical Impact of Aerodynamic Stall on Tunnel Ventilation Fans". International Journal of Rotating Machinery 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/402763.

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This paper describes work aimed at establishing the ability of a tunnel ventilation fan to operate without risk of mechanical failure in the event of aerodynamic stall. The research establishes the aerodynamic characteristics of a typical tunnel ventilation fan when operated in both stable and stalled aerodynamic conditions, with and without an anti-stall stabilisation ring, with and without a “nonstalling” blade angle and at full, half, and one quarter design speed. It also measures the fan’s peak stress, thus facilitating an analysis of the implications of the experimental results for mechanical design methodology. The paper concludes by presenting three different strategies for tunnel ventilation fan selection in applications where the selected fan will most likely stall. The first strategy selects a fan with a low-blade angle that is nonstalling. The second strategy selects a fan with a high-pressure developing capability. The third strategy selects a fan with a fitted stabilisation ring. Tunnel ventilation system designers each have their favoured fan selection strategy. However, all three strategies can produce system designs within which a tunnel ventilation fan performs reliably in-service. The paper considers the advantages and disadvantages of each selection strategy and considered the strengths and weaknesses of each.

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van Driel, Irene I., Walter Gantz e Nicky Lewis. "Unpacking What It Means to Be—or Not Be—A Fan". Communication & Sport 7, n. 5 (16 settembre 2018): 611–29. http://dx.doi.org/10.1177/2167479518800659.

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Sports fanship is a multidimensional concept. Fans are fans for a variety of reasons and show their fanship in an assortment of ways. In many studies, sports fanship is based on predetermined categories and closed-ended questions set by researchers. Such categories and questions may include certain types of fans while omitting others. This study assessed the extent to which closed-ended categorizations align with fans’ views of their own fanship. It also captured what it means to be—or not be—a sports fan from the respondent’s perspective. A total of 1,093 adults completed questionnaires using Amazon’s Mechanical Turk. In response to a dichotomous choice question, roughly half self-reported as fans. A majority of self-identified fans described strong emotional and personal ties with sports. Most nonfans found little connection with sports: Sports were boring and inconsistent with how they defined themselves. Open-ended responses from a small proportion of fans and a larger subset of nonfans call into question the validity of a single, dichotomous choice measure of fanship. The results of this study document the importance of explicit conceptualizations and operationalizations of sports fanship.

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Ge, Hengqing, Guang Xu, Jinxin Huang e Xiaoping Ma. "A mine main fans switchover system with lower air flow volatility based on improved particle swarm optimization algorithm". Advances in Mechanical Engineering 11, n. 3 (marzo 2019): 168781401982928. http://dx.doi.org/10.1177/1687814019829281.

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A reliable ventilation system is essential for maintaining a comfortable working environment and ensuring safety production in an underground coal mine. The automated fan switchover technique was developed for changing the main fan for maintenance with lower air flow volatility of underground mine in the switchover process. This article established the optimization model in the main fans switchover process, used the improved particle swarm optimization algorithm to solve the model, and achieved minimum air flow volatility in the fans switchover process. Compared to previous studies, computer simulations have shown that the proposed algorithm can effectively find the global optimal solution with less initial parameters and achieved lower air flow volatility in underground mine. The particle swarm optimization solution, searching diversity, prevents it from confining to local optimal solutions and enhances convergence. The reasonable step length is beneficial to reduce the air flow volatility and main fans switchover time. The air flow volatility is larger comparatively when some doors are nearly open or closed fully at the start–stop phase of the switchover process. A case application in a China’s domestic coal mine shows that the air flow volatility of the underground mine in the main fans switchover process is no more than 0.4%.

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Wu, S. F., S. Su e H. Shah. "NOISE RADIATION FROM ENGINE COOLING FANS". Journal of Sound and Vibration 216, n. 1 (settembre 1998): 107–32. http://dx.doi.org/10.1006/jsvi.1998.1691.

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DeGaspari, John. "A Fan for All Seasons". Mechanical Engineering 121, n. 12 (1 dicembre 1999): 58–60. http://dx.doi.org/10.1115/1.1999-dec-4.

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This article discusses high-volume low-speed (HVLS) fans that keep industrial units cool. High ceilings, heat generating motors and furnaces, and poor ventilation often work together to keep industrial spaces hot. The idea behind the HVLS fan originated several years ago from a class project at the Cooperative Extension of the University of California at Riverside, which develops applications for the state’s agriculture industry. HVLS fans rotate slowly, at 25 to 125 rpm, powered by a motor of less than one horsepower. The concept behind the HVLS fan is to move large amounts of air slowly. The fan produces a soft, cooling breeze that is effective in mixing the air in the plant. A single 20-foot HVLS fan costs $3,750. With average operating costs as low as five to 10 cents an hour, depending on utility rates, HVLS fans offer a simple, low-cost approach to keeping big industrial spaces comfortable.

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BREWER, GIVEN A. "Vibration Absorber System Smooths Operation of Induced-draft Fans". Experimental Techniques 5, n. 1 (28 gennaio 2008): 7. http://dx.doi.org/10.1111/j.1747-1567.1981.tb01594.x.

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Huang, Wenhui, Lei Chen, Lijun Yang e Xiaoze Du. "Energy-Saving Strategies of Axial Flow Fans for Direct Dry Cooling System". Energies 14, n. 11 (28 maggio 2021): 3176. http://dx.doi.org/10.3390/en14113176.

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The operating conditions of axial flow fans are closely related to the thermo-flow characteristics of the mechanical draft direct dry cooling system. Moreover, the uneven distribution of cooling air driven by axial flow fans may lead to the deterioration of the heat transfer capacity of air-cooled condensers (ACCs). Therefore, developing energy-saving operating methods for axial flow fans is very meaningful. In this work, two kinds of adjustment strategies to make the flow field more uniform are proposed for a 2 × 300 MW direct dry cooling power-generating unit. The performance of ACCs in the prevailing wind direction is predicted with the help of the macro heat exchanger model. It is found that the inlet air temperatures of fans are significantly reduced by proposed strategies, especially at high wind speeds. Moreover, the minimum cooling air can meet the cooling demand of ACCs for the strategy which made the air flow rates of all fans consistent. Compared with the case without adjustment of fans, the total power consumption of the fan array was cut down effectively, up to 13.94% at the wind speed of 12 m/s. In conclusion, the energy efficiency of ACCs can be improved by the uniform flow field.

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FUJII, Takeo, Takashi IKEDA e Ryuji MATSUSHITA. "Vibrations in Centrifugal Fans due to V-Belt Excitation(Mechanical Systems)". Transactions of the Japan Society of Mechanical Engineers Series C 76, n. 763 (2010): 516–24. http://dx.doi.org/10.1299/kikaic.76.516.

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Slavov, Valentin, e Georgi Vukov. "Modelling and researching of forced spatial vibrations of axial fans". MATEC Web of Conferences 287 (2019): 03006. http://dx.doi.org/10.1051/matecconf/201928703006.

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This work presents a mechanic - mathematical matrix modelling of the forced spatial vibrations of an axial fan. The axial fan is considered as a mechanical system consisting of three rigid bodies and with 18 degrees of freedom. The differential equations of the forced vibrations are derived. They take into account the mass, inertial, elastic, damping and geometric characteristics of this mechanical system. Algorithms are developed for computer calculating, analysis and synthesis of the design of this axial fan. These algorithms are a prerequisite for achieving the required operational properties of the fan and its compliance with the standards and regulations for vibrations’ impact on the human body. Calculations and results of the forced spatial vibrations are provided for specific parameters of the mechanical system.

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Dafermos, C. M. "Admissible wave fans in nonlinear hyperbolic systems". Archive for Rational Mechanics and Analysis 106, n. 3 (settembre 1989): 243–60. http://dx.doi.org/10.1007/bf00281215.

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Karadimas, G. "Design of High-Performance Fans Using Advanced Aerodynamics Codes". Journal of Turbomachinery 110, n. 4 (1 ottobre 1988): 419–25. http://dx.doi.org/10.1115/1.3262214.

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In the recent past, the performance of transonic fans has been significantly improved. In addition, through the extensive use of advanced aerodynamic computation codes, the development time required has been considerably reduced. Methods used range from the definition of airfoils in quasi-three-dimensional flow with boundary layer optimization to the analysis of three-dimensional inviscid flow for stage operation at the design point and in off-design conditions. Such a set of methods was used to design the fan blade of the CFM56-5 engine to a very high performance level. This paper will discuss the optimization of rotor and stator airfoils, the assessment of off-design performance, and the operational stability of this fan. A detailed comparison of full-size component test data with computation results shows the validity of these methods and also identifies those areas where research is still required.

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Rojas, Jhan Piero, Edwin Espinel e Eder Florez. "Parametrical Study of Centrifugal Airfoil Fans by Computational Tools". International Review of Mechanical Engineering (IREME) 14, n. 12 (31 dicembre 2020): 750. http://dx.doi.org/10.15866/ireme.v14i12.19281.

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Montazerin, N., A. Damangir e A. Kazemi Fard. "A study of slip factor and velocity components at the rotor exit of forward-curved squirrel cage fans, using laser Doppler anemometry". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 215, n. 4 (1 giugno 2001): 453–63. http://dx.doi.org/10.1243/0957650011538712.

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Abstract (sommario):

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.

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29

Khalkhali, Abolfazl, Mehdi Farajpoor e Hamed Safikhani. "MODELING AND MULTI-OBJECTIVE OPTIMIZATION OF FORWARD-CURVED BLADE CENTRIFUGAL FANS USING CFD AND NEURAL NETWORKS". Transactions of the Canadian Society for Mechanical Engineering 35, n. 1 (marzo 2011): 63–79. http://dx.doi.org/10.1139/tcsme-2011-0005.

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Abstract (sommario):

In the present study, multi-objective optimization of Forward-Curved (FC) blade centrifugal fans is performed in three steps. In the first step, Head rise (HR) and the Head loss (HL) in a set of FC centrifugal fan is numerically investigated using commercial software NUMECA. Two meta-models based on the evolved group method of data handling (GMDH) type neural networks are obtained, in the second step, for modeling of HR and HL with respect to geometrical design variables. Finally, using the obtained polynomial neural networks, multi-objective genetic algorithms are used for Pareto based optimization of FC centrifugal fans considering two conflicting objectives, HR and HL.

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30

Podsedkowski, Leszek, Piotr Wroblewski, Lukasz Fracczak, Agnieszka Kobierska, Emil Marciniak, Grzegorz Wrobel, Adrian Marciniak et al. "A differential planetary gear for regulation drive design and selected tests". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, n. 21 (9 dicembre 2017): 3964–76. http://dx.doi.org/10.1177/0954406217745338.

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Abstract (sommario):

Radial fans with efficiency regulation during their work using variational geometry of the rotor have not been used in industries until now, despite the fact that this is the most economically effective regulation method. One of the causes for this was the lack of a convenient method of transferring drive to moving blades of the fan. This paper presents an innovative method of transferring drive on the blades using a differential planetary gear. The construction is described, and a strength calculation methodology and tests confirming correctness of work are shown as well. The presented solution can become a new standard in the construction of energy fans.

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31

Čudina, M. "Noise generation in vane axial fans due to rotating stall and surge". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 215, n. 1 (1 gennaio 2001): 57–64. http://dx.doi.org/10.1243/0954406011520517.

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Abstract (sommario):

A characteristic of axial flow fans is instabilities in their performance and noise in partial load operation. These instabilities are a consequence of rotating stall created in the rotor blade and/or in the guide vane cascade. At some operating conditions the rotating stall caused the appearance of a surge representing the lowest region of fan operating stability. The rotating stall and especially surge caused a steep increase in the emitted noise and lowered the performance of the fan. The present paper highlights the rotating stall generation phenomenon and its influence on the emitted total noise level and noise spectra for axial flow fans with inlet and outlet guide vanes.

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32

Kim, Jae-Won, Eun Young Ahn e Hyoung Woo Oh. "Performance Prediction of Cross-Flow Fans Using Mean Streamline Analysis". International Journal of Rotating Machinery 2005, n. 2 (2005): 112–16. http://dx.doi.org/10.1155/ijrm.2005.112.

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Abstract (sommario):

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

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33

Raeisi, Bahram, e Hekmat Alighanbari. "Simulation and analysis of flow around tilting asymmetric ducted fans mounted at the wing tips of a vertical take-off and landing unmanned aerial vehicle". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, n. 15 (3 luglio 2017): 2870–97. http://dx.doi.org/10.1177/0954410017716954.

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Abstract (sommario):

Tilting ducted fans attached to the wing tips of vertical take-off and landing unmanned aerial vehicles define new applications for these types of aerial vehicles. This new configuration gives vertical take-off and landing unmanned aerial vehicles the ability to hover like helicopters and fly forward like airplanes, which results in using any arbitrary location for take-off and landing combined with increasing range and speed. Furthermore, generating additional lift using asymmetrical shape for the external body of the ducted fans can lead to reducing the wing area and related overall drag, which results in saving more energy. This research provides experimental results from wind tunnel tests in addition to computational fluid dynamics simulations to investigate the advantages of using an asymmetrical tilting ducted fan instead of a symmetrical one. “actuator disk model” combined with the assumption of “constant delivered power” to the propeller were used successfully to calculate the induced velocity to the rotor plane of the ducted fan in the computational fluid dynamics simulations. The effects of the stall and flow separation on the aerodynamic coefficients were also studied and compared for the symmetrical and asymmetrical ducted fans. Both computational fluid dynamics and experimental results showed noticeable improvement in the lift coefficient using an asymmetrical shape for the external body of the tilting ducted fans.

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34

Calvert, W. J., e A. W. Stapleton. "Detailed Flow Measurements and Predictions for a Three-Stage Transonic Fan". Journal of Turbomachinery 116, n. 2 (1 aprile 1994): 298–305. http://dx.doi.org/10.1115/1.2928364.

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Abstract (sommario):

Detailed flow measurements were taken at DRA Pyestock on a Rolls-Royce three-stage transonic research fan using advanced laser transit velocimetry and holography techniques to supplement the fixed pressure and temperature instrumentation. The results have been compared with predictions using the DRA S1-S2 quasi-three-dimensional flow calculation system at a range of speeds. The agreement was generally encouraging, both for the overall performance and for details of the internal flow such as positions of shock waves. Taken together with the computational efficiency of the calculations and previous experience on single-stage transonic fans and core compressors, this establishes the S1-S2 system as a viable design tool for future multistage transonic fans.

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35

FUJII, Takeo, Takashi IKEDA e Ryuji MATSUSHITA. "Amplitude Modulation Phenomena of Vibrations in Belt-Driven Centrifugal Fans(Mechanical Systems)". Transactions of the Japan Society of Mechanical Engineers Series C 76, n. 768 (2010): 2084–93. http://dx.doi.org/10.1299/kikaic.76.2084.

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36

Williams, Marc H., Jinsoo Cho e William N. Dalton. "Unsteady aerodynamic analysis of ducted fans". Journal of Propulsion and Power 7, n. 5 (settembre 1991): 800–804. http://dx.doi.org/10.2514/3.23394.

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37

Walsh, Patrick, Vanessa Egan, Ronan Grimes e Edmund Walsh. "Profile Scaling of Miniature Centrifugal Fans". Heat Transfer Engineering 30, n. 1-2 (gennaio 2009): 130–37. http://dx.doi.org/10.1080/01457630802293555.

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38

Chang, Cheng-Yuan, Xiu-Wei Liu, Sen M. Kuo, Department of Electrical Engineering, Chung Y, Department of Electrical Engineering, Chung Y, Department of Electrical Engineering, Chung Y, Department of Electrical Engineering, Chung Y e Department of Electrical Engineering, Chung Y. "Active noise control for centrifugal and axial fans". Noise Control Engineering Journal 68, n. 6 (1 novembre 2020): 490–500. http://dx.doi.org/10.3397/1/376840.

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Abstract (sommario):

Fans are widely used in industry for heat dissipation or airflow production. It is achieved by driving a motor of fan to rotate a number of blades. Most industrial fans can be categorized into one of two general types: centrifugal fans and axial fans. However, fan noise is loud when the motor speed is high. This article develops using active noise control (ANC) system to reduce noise from both centrifugal and axial fans. By integrating loudspeakers and microphones, we present multiple-channel feedback ANC structure with the filtered-X least mean square (FXLMS) algorithm to simultaneously reduce noise from the inlet and the outlet of the fans. Several realtime experiments verify that the proposed method and experimental setup not only reduces the narrowband noise but also achieves the global cancellation of the fan noise.

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39

Montazerin, N., A. Damangir e H. Mirzaie. "Inlet induced flow in squirrel-cage fans". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 214, n. 3 (1 maggio 2000): 243–53. http://dx.doi.org/10.1243/0957650001538335.

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Abstract (sommario):

Energy conversion in squirrel-cage fans is sensitive to the inlet geometry. It occurs at the inlet where a separation zone which occupies a major volume in the rotor and the volute starts. In this research, different inlets of inward and outward types were tested on two fans. First, the inlet diamenter and position were matched with the rotor, which improved the fan characteristic curves. The results of the experiments were sensitive to the width of the blade retaining ring (shroud). Later the tangential and radial components of the velocity out of the rotor were measured. The resulting velocity profiles across the scroll width showed that outward inlets produce a more uniform velocity angle inside the volute than inward inlets did. This was not because of a more aerodynamic flow through the rotor blades by was due to a better match between the inlet and the volute. The axial energy transfer resulted in tangential velocities larger than the rotor velocity, at axial positions across the volute where there was no flow out of the rotor.

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40

Lv, Yukun, Zheng-Wei Lv, Hong-Yang Li, Bao-Jun Song, Bo Cheng e Bo Zhang. "Design of volute shape of centrifugal fans". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 230, n. 2 (30 dicembre 2015): 141–53. http://dx.doi.org/10.1177/0957650915624034.

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41

Pan, D., A. Whitfield e M. Wilson. "Design considerations for the volutes of centrifugal fans and compressors". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 213, n. 4 (1 aprile 1999): 401–10. http://dx.doi.org/10.1243/0954406991522356.

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Abstract (sommario):

The initial conceptual design of centrifugal fan and compressor volutes is considered and extended to accommodate overhung volute designs often used in process and turbocharger compressors. The initial passage design is then developed through the application of a commercial computational fluid dynamics (CFD) code.’ Based on the experimental data of a turbocharger compressor volute, three-dimensional, compressible, steady flow computations were carried out for alternative volute designs. Detailed internal flow data in both a conventional and a modified volute design, at both design and off-design flow conditions, are presented. The design investigation showed that enlarging the flow passage area near the tongue region, but without changing the exit-inlet area ratio of the volute, led to an improvement in the internal flow distribution at off-design flow conditions.

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42

Neal, D. R., e J. F. Foss. "The Application of an Aerodynamic Shroud for Axial Ventilation Fans". Journal of Fluids Engineering 129, n. 6 (2 gennaio 2007): 764–72. http://dx.doi.org/10.1115/1.2734206.

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Abstract (sommario):

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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43

Azimian, A. R., R. L. Elder e A. B. McKenzie. "Application of Recess Vaned Casing Treatment to Axial Flow Fans". Journal of Turbomachinery 112, n. 1 (1 gennaio 1990): 145–50. http://dx.doi.org/10.1115/1.2927411.

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Abstract (sommario):

The effect of applying a vaned recessed casing treatment to a single-stage axial flow fan has been investigated. The influences of the axial position of the recess relative to the rotor leading edge and other geometric modifications of the vane passage have been examined. Significant improvements in stall margin were observed without (in some builds) loss in peak efficiency. Slow and fast frequency response yawmeter probes have been used in the study to examine both the steady flow conditions and the unsteady flow caused by rotating stall.

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44

Corsini, Alessandro, e Anthony G. Sheard. "End-plate for noise-by-flow control in axial fans". Periodica Polytechnica Mechanical Engineering 57, n. 2 (2013): 3. http://dx.doi.org/10.3311/ppme.7039.

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45

Szlivka, Ferenc, e Ildikó Molnár. "Measured and non-free vortex design results of axial flow fans". Journal of Mechanical Science and Technology 22, n. 10 (ottobre 2008): 1902–7. http://dx.doi.org/10.1007/s12206-008-0730-0.

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46

Huang, Cheng-Hung, e Min-Hsiang Hung. "An optimal design algorithm for centrifugal fans: Theoretical and experimental studies". Journal of Mechanical Science and Technology 27, n. 3 (marzo 2013): 761–73. http://dx.doi.org/10.1007/s12206-013-0126-7.

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47

Lichter, Seth, Arie Dagan, William B. Underhill e Hassan Ayanle. "Mixing in a Closed Room by the Action of Two Fans". Journal of Applied Mechanics 57, n. 3 (1 settembre 1990): 762–68. http://dx.doi.org/10.1115/1.2897089.

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Abstract (sommario):

The mixing induced by two constant flow rate fans, which vary periodically in direction, is studied as a function of the period of oscillation of the fans. The three-dimensional equations of motion are integrated to determine the particle trajectories. As first shown by Aref’s work on a two-dimensional map, mixing may be greatly enhanced by unsteadiness. It is found that trajectories can be trapped in a restricted region by surfaces which function similarly to KAM tori in two dimensions. Results are presented for the largest Lyapunov exponent and the correlation dimension as a function of oscillation period. These results may be used to determine the conditions for good mixing.

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48

He, Yijian, Xiangyu Chen, Youming Zheng e Guangming Chen. "Numerical simulation of a wire–plate solid-state fan for ultra-quiet museum display cases". Indoor and Built Environment 29, n. 7 (18 settembre 2019): 1028–37. http://dx.doi.org/10.1177/1420326x19876100.

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Abstract (sommario):

Conventional microenvironment control systems of a museum display case generally use mechanical fans which produce great noise and vibration for heat dissipation of semiconductor air-conditioning units. Solid-state fans (ionic wind) operate with no moving parts and can overcome noise and vibration issues of a microenvironment control system. In this study, a multi-electrode mathematical and physical model of wire–plate solid-state fans was developed, and its performance has been analysed in depth. Simulation results indicate that there is an optimal distance between discharge electrodes ( d), which corresponds to the largest average wind velocity at the exit of the simulation area ( ua). Under the same power consumption, ua and the vertical height from a discharge electrode to a collecting electrode ( H) exhibit a monotonically increasing relationship. Similarly, ua and the radius of a discharge electrode ( r) show a monotonically decreasing relationship. In addition, a manufactured solid-state fan with an average wind velocity of 1.48 m·s−1 shows a noise intensity of 4.3 dB(A), which is considerably lower than that of a mechanical fan, with the same power consumption. These positive results suggest that ultra-quiet microenvironment control technologies of a museum display case can be potentially developed in the near future.

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49

Sorguven, Esra, e Yilmaz Dogan. "Acoustic optimization for centrifugal fans". Noise Control Engineering Journal 60, n. 4 (7 gennaio 2012): 379–91. http://dx.doi.org/10.3397/1.3701018.

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50

Sharke, Paul. "From Helios to Our House". Mechanical Engineering 123, n. 08 (1 agosto 2001): 42–46. http://dx.doi.org/10.1115/1.2001-aug-1.

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Abstract (sommario):

A study commissioned by Florida Power and Light Co. of Juno Beach reports that energy savings in Florida from ceiling fans came only with the raising of air conditioner thermostats. Making fans with high-efficiency motors offered one way of achieving that goal and aerodynamic blades offer another. Infrared thermogram of a typical ceiling fan shows heat generated by the motor. Temperature scale at bottom reads from coolest to hottest. With simulations having helped the decision on the choice of design, the engineer team set out to discover a building method for making the prototype blades. As work proceeded on the blades, Florida Solar Energy Center, in Cocoa, also considered what sort of control system would eventually operate a production version. Even after undergoing many redesigns from the original wooden-blade prototype development team tested back in 1997, the two production models offer substantial improvements in energy efficiency.

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