Relevant bibliographies by topics / Recirculation fan

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Recirculation fan'

Author: Grafiati
Published: 4 June 2021
Last updated: 9 February 2022

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Journal articles on the topic "Recirculation fan"

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Borghei, Leila, and Ramin Haghighi Khoshkho. "Effects of Wind on Hot Air Recirculation (HAR) Behavior." Applied Mechanics and Materials 110-116 (October 2011): 2067–74. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.2067.

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The air-cooled condenser system is impacted greatly by many factors such as the wind speed, the direction of wind and arrangement of site equipments. This paper concentrates on the hot air recirculation phenomenon and its dependence on ambient winds are numerically simulated by using the computational fluid dynamics code, FLUENT. In this paper, two different wind directions (case A and case B) and wind speeds are considered: Results show that the hot air recirculation increases with the increment of velocity speed. Case A has a critical wind direction angle. Wind causes an air temperature increase at the fan inlet due to hot air recirculation, resulting in the deterioration of the heat transfer performance. The hot air recirculation is the main factor responsible for the reduction of heat rejection rate. In case A, fan inlet temperature is higher than case B. The peak value of the HAR occurs at 9 m/s in case A.
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Faulkner, David, William Fisk, and John Walton. "Energy Savings in Cleanrooms from Demand-Controlled Filtration." Journal of the IEST 39, no. 6 (November 1, 1996): 21–27. http://dx.doi.org/10.17764/jiet.2.39.6.k8792h8164vk5218.

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In cleanrooms, very low particle concentrations are maintained by recirculation of air at a high rate (e.g., 600 room air volumes/hr) through highly efficient air filters. Results are reported in a Class M3.5 (Class 100) cleanroom with 28 m2 (300 ft2) floor area, where significant energy savings were realized by controlling the rate of air recirculation through the filters in response to real-time measurements of particle concentrations. An inexpensive, $2500, optical particle counter was used to measure particle concentrations. The effect of varying the recirculation airflow rate on particle concentrations was investigated. Changes in recirculation fan speeds of 10 percent or greater did not cause a noticeable particle release from filters or resuspension from indoor surfaces. With new automatic control systems in operation, there were occasional, usually fewer than 10/day, nonconsecutive l-min episodes in which the particle concentration exceeded Class M3.5 (Class 100) status. Depending upon the choice for baseline energy use, the energy consumption of the recirculating fans was reduced by 60 to 80 percent, and the estimated payback period for a 90 m2 (1,000 ft2) Class M3.5 (Class 100) cleanroom is from 1 to 4 yr.
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Li, Xiangjun, Stephen Spence, Hua Chen, Wuli Chu, and Lee Gibson. "Flow Control by Slot Position and Noise Baffle in a Self-Recirculation Casing Treatment on an Axial Fan-Rotor." International Journal of Rotating Machinery 2017 (2017): 1–18. http://dx.doi.org/10.1155/2017/9509212.

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To address the situations where the casing treatment needs to be used to stabilize axial compressors through strong recirculation, this paper initiated a CFD study to investigate how the flow could be suitably controlled in the casing treatment to minimize the efficiency penalty and increase the flow range. A counter-swirl self-recirculation casing treatment was first designed on a low speed axial fan rotor as a baseline case. Then three different slot positions and the influence of including the noise baffle were numerically studied. Based on the understanding of their coeffects, the shorter noise baffle was considered and it was found that the highest efficiency was achieved in the case of the upstream slot when the length of baffle was suitably adjusted to balance the incoming flow and recirculation. The largest flow range was achieved by locating the slot at the most downstream position and using a 50% length baffle since it suitably controlled the recirculating flow and relieved the separation at the low-span region. An optimization study showed that the optimum length of the baffle for efficiency was always larger than for the flow range. Both of the two optimum values reduce as the slot moves downstream.
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KIM, HWA-YOUNG, SUNG-HOON YOON, SEUNG-JAE MOON, JAE-HEON LEE, HOSEON YOO, and YUN-CHUL IM. "A STUDY ON THE FAN EFFICIENCY DECREASE ON THE BACKWARD FLOW IN AN AXIAL FAN WITH ADJUSTABLE PITCH BLADE." International Journal of Air-Conditioning and Refrigeration 18, no. 02 (June 2010): 101–7. http://dx.doi.org/10.1142/s2010132510000216.

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In this study, a numerical study has been carried out to analyze the factors of the efficiency decrease at backward flow situation in an axial fan with adjustable blades. The analysis is done with the pitch angle of 36° on the forward flow and of -26° on the backward flow. The numerical results show that the air flow rates of the pitch angle of 36° and -6° are calculated to be 285 cubic meter per min (CMM) and 212 CMM, respectively. The results are similar to the experimental results by Chang et al.1 The results had the maximum error of 10.6% compared with the experimental results. The fan efficiency decrease is caused by the fact that the axial fan used for this study was designed for the forward flow. As the results, the pitch angle of -26° has induced the recirculation around the impeller blade, impeller cover and downstream. This recirculation caused the large decrease in total pressure coefficient. This turned out to be the main cause of the efficiency decrease.
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Dilin, P., T. Sakai, M. Wilson, and A. Whitfield. "A computational and experimental evaluation of the performance of a centrifugal fan volute." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 212, no. 4 (June 1, 1998): 235–46. http://dx.doi.org/10.1243/0957650981536763.

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A detailed experimental study of the performance of two radial-flow fan volutes has been carried out at the Science University of Tokyo. This included a volute with a full tongue, such that no recirculating flow occurred, and the same volute but with the tongue cut back to allow flow recirculation. Detailed velocity and pressure distributions at a wide range of azimuth angles were obtained experimentally and are presented. At the University of Bath a computational model, using the k-e turbulence model, has been used to predict the internal flow of both volutes, with particular attention given to the tongue flow. Predicted flow separation at the volute tongue has been demonstrated experimentally through laser sheet studies at the Science University of Tokyo. The performance of the volutes is discussed and the computational fluid dynamics (CFD) analysis is used to recommend design improvements for the volute.
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Wang, Lidong. "SEARCHING UNGROUND FAN INDUCED RECIRCULATION IN A COMPLICATED MINE VENTILATION NETWORK." Stavební obzor - Civil Engineering Journal 27, no. 1 (2018): 104–13. http://dx.doi.org/10.14311/cej.2018.01.0009.

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Shriwas, Mahesh, and Felipe Calizaya. "Automation in detection of recirculation in a booster fan ventilation network." International Journal of Mining Science and Technology 28, no. 3 (May 2018): 513–17. http://dx.doi.org/10.1016/j.ijmst.2018.04.009.

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Mutama, K. R., and A. E. Hall. "The Experimental Investigation of Jet Fan Aerodynamics Using Wind Tunnel Modeling." Journal of Fluids Engineering 118, no. 2 (June 1, 1996): 322–28. http://dx.doi.org/10.1115/1.2817380.

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Jet fan aerodynamic behavior was investigated using wind tunnel modeling. Conditions were created to simulate mine and vehicular tunnel ventilation where these fans are finding increased application. Results showed that the ability of a jet fan to entrain air depends on its proximity to the tunnel wall. Moving the jet fan toward the wall increased the initial pressure drop below ambient in a significant length of the tunnel. This increased the volume of air entrained despite the existence of a large recirculation eddy or back flow whose size diminished as the jet fan was traversed toward the tunnel axis. When the jet fan was located at the tunnel axis the flow was very unstable close to the walls of the tunnel and it had a tendency to reverse itself with periods coinciding with the jet oscillation behavior. The complete set of measurements obtained are suitable for CFD code validation and modeling.
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Chen, Q. G., Y. C. Zhang, F. Li, X. Z. Kong, and X. H. Luan. "Effects of anti-recirculation ring on performance of an automotive cooling fan." IOP Conference Series: Materials Science and Engineering 52, no. 4 (December 20, 2013): 042008. http://dx.doi.org/10.1088/1757-899x/52/4/042008.

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Коновалов, Дмитро Вікторович. "ЗАСТОСУВАННЯ ГАЗОДИНАМІЧНОГО ОХОЛОДЖЕННЯ В СИСТЕМАХ РЕЦИРКУЛЯЦІЇ ВІДХІДНИХ ГАЗІВ СУДНОВИХ ДИЗЕЛІВ." Aerospace technic and technology, no. 7 (August 31, 2019): 81–86. http://dx.doi.org/10.32620/aktt.2019.7.11.

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There are many ways and methods to reduce exhaust gases emissions on modern ships. One of the most effective ways to reduce NOx and SOx emissions is to use of exhaust gas recirculation (EGR technology). The EGR system disadvantage is an increase in back pressure through additional pressure losses in the scrubber and heat ex-changer, which entails an engine fuel efficiency deterioration. Creating a reliable and efficient heat exchanger for cooling recirculation gases is a complex task due to deposits and pollution emitted by these gases. In the pre-sent work, the jet apparatus effectiveness named aerothermopressor is analyzed in the scheme with exhaust gases recirculation of the ship low-speed two-stroke engine. Aerothermopressor is a two-phase jet for contact disperse cooling, in which by increasing the heat from the gas stream the gas pressure and cooling are increased. The calculation of the characteristics of the engine was carried out, both in nominal, and in operating modes and in all possible range of partial loads. The installation of the aerothermopressor before the scrubber is pro-posed, which allows reducing engine thermal load. Increasing the pressure in the aerothermopressor by 0.2-0.4 ∙ 105 Pa (6-12 %) allows reducing the back pressure in the gas exhaust system and thus reducing the load on the exhaust gas recirculation fan and when the engine load is higher than 75% in the cold zone, the fan is not need-ed, which additionally allows to reduce the specific fuel consumption. The parameters of the exhaust gases that are going to be recirculated and the processes of their gas-dynamic cooling in the aerothermopressor are based on the developed technique and program using the thermodynamic and gas dynamics equations. The proposed scheme-design solution allows at a high environmental friendliness of the existing exhaust gas recirculation sys-tem to provide a certain reduction in specific fuel consumption. It was determined that the engine specific fuel consumption has been decreasing when the aerothermopressor is used to Dge = 2.5-3.0 g/(kW·h) (1.5-1.7%).
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Dissertations / Theses on the topic "Recirculation fan"

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Pawlitko, David. "Návrh mlýnice s kroužkovými mlýny s recirkulací spalin a bez recirkulace spalin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232168.

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This master’s thesis deals with the issue of recirculating of flue-gas of pulverized coal-fired boiler. Part of the thesis are thermal calculations of mills for operational status with and without flue-gas recirculation and design of routes of recirculated flue-gas into the mills at the level of feasibility study.
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Fabresse, Nicolas. "Traitement des intoxications. Étude de deux approches : un système d’épuration extra-rénale de type MARS et un antidote de type Fab anti-colchicine LC–MS/MS quantification of free and Fab-bound colchicine in plasma, urine and organs following colchicine administration and colchicine-specific Fab fragments treatment in Göttingen minipigs. Anti-colchicine Fab fragments prevent lethal colchicine toxicity in a porcine model: a pharmacokinetic and clinical study. Molecular Adsorbent Recirculating System and Continuous Venovenous Hemodiafiltration removal of verapamil: an ex vivo compartmental analysis Nicolas Molecular Adsorbent Recirculating System (MARS) and Continuous Veno-venous Hemodiafiltration (CVVHDF) for diltiazem removal: an ex vivo compartmental analysis." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV082.

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L’objectif de ce travail a été d’étudier deux approches permettant le traitement des intoxications. La première est un antidote de type Fab, permettant de prendre en charge les intoxications aiguës à la colchicine. L’étude pré-clinique a été réalisée chez le cochon nain Göttingen. Un modèle d’intoxication reproductible a préalablement été défini. L’efficacité de l’antidote a ensuite été évaluée à différents horaires post-administration de colchicine (T+1h, T+3h et T+6h). Chez tous les animaux traités (n=6), il a été observé une redistribution tissulaire importante des tissus vers le compartiment sanguin. Seule l’administration précoce de l’antidote (T+1h et T+3h) permet la survie des animaux à T48h, cela souligne l’importance d’une administration précoce afin de garantir une éfficacité chez l’homme.La deuxième partie de ce travail a consisté à évaluer l’efficacité du système de dialyse hépatique MARS dans l’épuration du vérapamil et du diltiazem dans un modèle in vitro. Le système MARS a également été comparé à un système de dialyse conventionnelle (CVVHDF). L’efficacité des deux systèmes a été évaluée à trois concentrations pour le vérapamil (1, 2,5 et 5 mg/L) et 2 concentrations pour le diltiazem (0,75 et 5 mg/L), sur des sessions de 6 heures. Le MARS est le système le plus efficace pour les deux molécules. L’épuration du vérapamil par la CVVHDF est principalement liée à l’adsorption de la molécule à la surface de la membrane de dialyse. Concernant le système MARS, la cartouche de charbon est responsable de l’épuration des deux molécules
The objective of this work was to study two approaches allowing the treatment of intoxications. The first is an antidote (anti-colchicine Fab fragments), allowing the management of acute poisoning with colchicine. The pre-clinical study was carried out using Göttingen minipigs. A reproducible intoxication model has been defined. The effectiveness of the antidote was then evaluated at different schedules (T +1h, T +3h and T +6h). In all treated animals (n = 6), significant tissue redistribution to the blood compartment was observed. Only the early administration of the antidote (T + 1h and T + 3h) allows the survival of animals at T48h, this underlines the importance of early administration to ensure efficacy in humans.The second part of this work was dedicated to the evaluation of the effectiveness of the MARS hepatic dialysis system in the removal of verapamil and diltiazem in an in vitro model. The MARS system was also compared to a conventional dialysis system (CVVHDF). The efficacy of both systems was evaluated at three concentrations for verapamil (1, 2.5 and 5 mg/L) and 2 concentrations for diltiazem (0.75 and 5 mg/L), on 6-hour sessions. MARS is the most efficient system for both molecules. Purification of verapamil by CVVHDF is mainly related to the adsorption of the molecule on the surface of the dialysis membrane. Concerning the MARS system, the carbon cartridge is responsible for the removal of the two molecules
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Book chapters on the topic "Recirculation fan"

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Morla, Ramakrishna, Shivakumar Karekal, Ajit Godbole, Mahesh Sriwas, Jan Jacobs, Purushotham Tukkaraja, and Brian Chapula. "Optimizing secondary fan location and air quantity to control DPM recirculation in underground workings using Discrete phase modelling." In Mine Ventilation, 124–32. London: CRC Press, 2021. http://dx.doi.org/10.1201/9781003188476-13.

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Conference papers on the topic "Recirculation fan"

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He, Weifeng, Yiping Dai, Qingzhong Ma, and Danmei Xie. "Numerical Investigation of Hot Air Recirculation in an Air-Cooled Steam Condenser Under Ambient Conditions." In ASME 2011 Power Conference collocated with JSME ICOPE 2011. ASMEDC, 2011. http://dx.doi.org/10.1115/power2011-55055.

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Air-cooled steam condensers (ACSCs) have been extensively utilized to reject heat in modern power plant. Hot air recirculation, which implies that the heated air from the exchangers is again drawn back into the axial fans influence the performance of the ACSC. Hot air recirculation under different wind speeds and directions is numerically simulated in an ACSC of a 2×600MW air-cooled power plant with the commercial Computational Fluid Dynamics (CFD) code, FLUENT, and the performance of the ACSC is investigated. Fan boundary is applied to simulate the fan characteristics when the ambient air flows through the rotor and the source term is added to the Navier-Stokes equation to simulate the pressure loss when the air flows through the exchangers. Phase transition is involved in the simulation because the turbine exhaust condensates in the finned tube exchangers while the ambient air flows outside. As a result, user define function based on the actual steam property is applied to simulate the heat transfer course between the exhaust and the ambient air. Two different mechanisms of hot air are simulated: one is based on wind speed and the other is based on wind direction. The simulation result shows that when the wind blows in the front of the ACSC, the hot air from the heat exchanger flow out free at low wind speed while it flows into the fan in the A-frame, and reverse irrigation occurs. Recirculation rate reaches its peak value at α = 135° under the obstacle effect of the turbine and boiler houses. The hot air recirculation under ambient conditions is systematically studied in the paper, and the research results provide the reference for the design and operation of the power plant.
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Song, Zhihang, and Qian Zhang. "Advanced Data Center Cold Aisle Airflow Organization Optimization Using an Adjustable Fan Unit." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23229.

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Abstract The real-time smart data center cooling has become a key to maintenance and operation of energy-efficient data centers, primarily including the server inlet airflow/thermal domains. Here, the cold-aisle airflow phenomena in a widely-used cold/hot aisle data center configuration was under parametric investigation, This concern is mainly because of the airflow separation and recirculation from the stream emerging from the server outlet and returning to the computer room air-conditioning unit. In order to achieve a better understanding and to correspondingly eliminate the negative effects of the hot air over-tack recirculation towards a satisfied effectiveness, an addition of a rack-level adjustable fan unit (AFU), which is placed inside the cold aisle, was considered at an early stage and the model prototype was numerically analyzed with respects to differently predefined parameters. The cooling performance consequence, consisting of the server-neighbored inflow rates and maximum server inlet temperatures explored by computational fluid dynamics (CFD) observation panel and sensors, demonstrates that the over-rack air recirculation and its resulting hot spot, in comparison with the case in absence of the AFU, can be suppressed. The results additionally concludes the extents to which the optimized airflow organization and temperature drop of the rack-level region (e.g., from the bottom towards the top of the rack unit) can be achieved with/without the AFU addition.
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Maulbetsch, John S., Michael N. DiFilippo, and Joseph O’Hagan. "Effect of Wind on Air-Cooled Condenser Performance." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63157.

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This paper documents the results of a field tests to determine the effect of wind on the performance of air-cooled condensers (ACCs) at power plants. Continuous measurements of wind speed, wind direction, cell inlet temperature and air flow and plant operating variables were made for several days at the El Dorado Energy Center. ACC performance was shown to be affected both by hot air recirculation and by fan performance degradation. Average recirculation, defined as the difference between the average cell inlet temperature and the far-field inlet temperature, was usually less than 3 °F. Occasional excursions to 4 to 10 °F were noted. Fan performance degradation is more difficult to quantify or generalize. Under low wind conditions this was typically close to the design value. The reduction in air flow, estimated from inlet velocity measurements would sometimes exceed 60 to 70% of the average flow in cells near the edge of the ACC during high wind conditions. Fan performance degradation appears to be the more important mechanism. Comparisons with flow modeling results support design recommendations for suppressing unfavorable flow patterns under the ACC.
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Wagner, Patrick H., Jan Van herle, and Jürg Schiffmann. "Theoretical and Experimental Investigation of a Small-Scale, High-Speed, and Oil-Free Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91361.

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Abstract The Laboratory for Applied Mechanical Design (LAMD) designed, manufactured, and experimentally tested a novel recirculation fan for a 10 kWe solid oxide fuel cell (SOFC). The fan uses oil-free bearings, more specifically herringbone-grooved journal and spiral-grooved thrust gas bearings. The radial inducer-less fan with a tip diameter of 19.2 mm features backward-curved prismatic blades with constant height. Prior to coupling the recirculation fan with the SOFC, the fan was experimentally characterized with air at 200 °C. At the nominal point of 168 krpm, the measured inlet mass flow rate is 4.9 kgh−1, the total-to-total pressure rise 55 mbar, the isentropic total-to-total efficiency 55 %, and the power 18.3 W. This paper compares the experimental data towards a computational fluid dynamic simulation of the full fan impeller and volute suggesting an excellent correlation at the nominal point what validates the numerical approach. However, the heat flows crossing the fan fluid domain, have an increased effect at off-design conditions, thus the experimental results need careful consideration. The fan backface leakage has negligible impact on the measurements.
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Sanjose, M., D. Lallier-Daniels, and S. Moreau. "Aeroacoustic Analysis of a Low-Subsonic Axial Fan." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43737.

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A mesh convergence study of direct aero-acoustic simulations of a typical automotive engine cooling rotor is performed. The simulations are performed using the Lattice Boltzmann Method (LBM) that has been extensively used in the recent years for low speed fan applications. The influence of the mesh refinement on the global performances, the pressure distribution over the blade and in the wake and tip gap zones is investigated using the large experimental database available. The direct acoustic predictions for the different numerical setups is compared with acoustic measurements and a Ffowcs Williams and Hawking’s analogy is applied to identify the noise source contributions from the rotor parts. With the three setups investigated the convergence is achieved on the global performances and the sound power spectra. Still some discrepancies between the setups appear in the unsteady pressure loading of the blades and the wake flow. The blades are seen as the main noise contributors particularly the cusp region near the hub and the tip region with the tip flow recirculation.
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Natarajan, Shankar, Aditya Mulemane, and Pradip Dube. "Underhood and Underbody Studies in a Full Vehicle Model Using Different Approaches to Model Fan and Predict Recirculation." In SAE World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2008. http://dx.doi.org/10.4271/2008-01-1173.

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Jang, Choon-Man, Sang-Yoon Lee, and Sang-Ho Yang. "Efficiency Enhancement by Shape Optimization of Centrifugal Fan Installed in Refuse Collecting System." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78491.

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Shape optimization in the design of turbomachinery based on the three-dimensional flow analysis has been developed remarkably in recent years with the rapid enhancement of computational power. In the present study, optimal design of a centrifugal fan installed in refuse collecting system has been performed using response surface method and three-dimensional Navier-Stokes analysis to increase fan efficiency. The centrifugal fan is used to increase suction pressure for the moving of a waste through the pipe line of the system. Two design variables, which are used to define the shape of an inlet guide, are introduced to increase the efficiency of the fan. In the shape optimization using the response surface method, data points for response evaluations are selected, and linear programming method is used for an optimization on a response surface. To analyze three-dimensional flow field in the centrifugal fan, general analysis code, CFX, is employed in the present work: SST turbulence model is employed to estimate the eddy viscosity. Unstructured grids are used to represent a composite grid system including blade, casing and inlet guide. Throughout the shape optimization of a centrifugal fan, the fan efficiency is successfully increased by decreasing local losses in the blade passage. The result of shape optimization shows that the efficiency of the optimized shape at the design flow condition is enhanced by 1.42% based on the reference fan. It is found that recirculation flow region of optimum one is relatively small compared to the reference one. The reduction of recirculation region can be decreased the shaft power of an impeller, thus it can be increased the efficiency of the fan.
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Louw, Francois G., Theodor W. von Backström, and Sybrand J. van der Spuy. "Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25927.

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Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.
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Chilukuri, R. "Inviscid, Axisymmetric, Annular Wall Jet Impingement As an Idealization of Cascade Thrust Reversers." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4641.

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Abstract An analytical solution to inviscid, axisymmetric, impinging wall jet flow is proposed as a limited idealization of internal flow within a cascade thrust reverser of an aircraft engine. Behavior of prior Bessel Series solution for round jets is critically examined, before extending the formulation to an annular jet with non-zero inner wall radius. Behavior and accuracy of prior spectral and finite difference algorithms are examined, leading to an efficient hybrid computational scheme. Jet inflow velocity profile has a deficit as well as non-zero vorticity-function at the inner radial boundary, as is typical in engine fan ducts. Inviscid recirculation appears at the impingement corner, the strength of which is made determinate by assuming locally constant vorticity-function. Results indicate that fan duct velocity profile deficit is a significant contributor to occurrence of a large recirculation zone that is experimentally observed within a fully deployed thrust reverser.
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Galdo-Vega, Mo´nica, Carlos Santolaria-Morros, Jesu´s Manuel Ferna´ndez Oro, and Katia Maria Argu¨elles-Di´az. "Influence of the Pressure Load in the Efficiency of a Longitudinal Ventilation System in Road Tunnels." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78355.

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The longitudinal ventilation system (LVS) efficiency in road tunnels is conditioned by geometric and operational parameters. Typical geometric parameters are the length of the tunnel, its slope and the transversal section. All these factors are generally fixed and thus not modifiable in the regular operation of the facility. On the other hand, operational parameters, like the working fans layout, the environmental conditions or the traffic density are case-sensitive and susceptible to influence the baseline performance of the ventilation system. In the present study, different pressure gradients, established between inlet and outlet location of the jet fan influence, are analyzed. This static resistance is shown to have a significant impact on the momentum transfer established between the jet expansion and the bulk flow inside the tunnel. For moderate pressure gradients, the jet discharged from fan is relativity well-mixed, allowing to reach uniform flow conditions in the streamwise direction. When the adverse pressure gradients become severe, the high-velocity flow is blocked, unable to mix out in the inter fan spacing and losing spanwise uniformity. At critical conditions, large recirculation areas can be developed within primary flow structures, generating turbulence and important energy losses, and even inducing reverse flow at the tunnel exit. The extreme operating conditions of a longitudinal ventilation system in a road tunnel have been studied using a 3D numerical simulation. Preliminary analysis for grid sensitivity and election of an accurate turbulence closure were performed to guarantee a valuable modeling. Following, systematic computations over a cluster of PC’s were executed using the well-tested Fluent code. RANS modeling with RSM scheme allowed a satisfactory description of three-dimensional vortical structure in the recirculation zones, especially for adverse pressure gradients. At this point, numerical results have provided a comprehensive overview of the mechanism associated to the momentum transfer of the jet expansion, comparing the performance for zero-pressure gradients with those observed for adverse conditions. Also, this paper gives valuable information about practical limits of the LVS, advancing operational conditions that compromise the ventilation efficiency.
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