Fan Diameter Research Articles

INCAS SUBSONIC WIND TUNNEL

The INCAS Subsonic Wind Tunnel is a closed circuit, continuous, atmospheric pressure facility with a maximum speed of 110 m/s. The test section is octagonal ,of 2.5 m wide, 2.0 m high and 4 m long. The tunnel is powered by a 1200 kW, air cooled variable speed DC motor which drives a 12 blade, 3.5 m diameter fan and is equipped with a six component pyramidal type external mechanical balance with a 700 Kgf maximum lift capacity. The angle of attack range is between -45o and +45o while the yaw angle range is between -140o and +216o . The data acquisition system has been modified recently to allow the recording of all test data on a PC type computer using LABVIEW and a PXI – type chassis containing specialized data acquisition modules. The tunnel is equipped with a variable frequency electrical supply system for powered models and a 10 bar compressed air supply for pneumatic flow control applications. In the recent years the subsonic wind tunnel has been intensively used for tests within several European projects (AVERT, CESAR and others). Introduction The 2.5 m x 2.0 m Subsonic Wind Tunnel is the first aerodynamic facility at INCAS. Fig. 1 . Subsonic Wind Tunnel Its main characteristics are the following: • Prandtl type, horizontal single return • Closed test section, atmospheric • Test section size: 2.5 m wide by 2 m high • Speed range: from 7 to 110 m/s • Angle of attack range: -45o to +45o • Yaw angle range: -140o to +216o • Reynolds number (for S l 1 . 0 = ): 1x10 • Contraction area ratio: k = 10 • Turbulence factor: 1.11 The most usual tests involve forces and moments measurements using the external TEM balance, followed by pressure distributions using the existing classical and electronic scanning devices and flow visualizations using smoke, tufts and oil paints. Laser sheet visualizations have been performed recently with spectacular results. Apart from the usual measurements of aerodynamic forces, pressure distributions and visualizations on models of aircraft, missiles, cars, buildings, bridges etc., there have been many special test programs like, for instance wind turbines (tested in the large area settling chamber of the tunnel), sky divers, skiers, cyclists, flag masts etc. The whole experimental activity in the Subsonic Wind Tunnel is carried out according to the existing Manual for Quality Assurance in the Subsonic Wind Tunnel. Description of the facility The tunnel is powered by a 1200 kW, air cooled variable speed (up to 800 rpm) DC motor which drives a 12 blade, 3.5 m diameter fan. The pressure drop across the fan blades is 210 Kgf/m. The motor air cooling is done by means of a special circuit equipped with a 20 KW fan. The DC motor is fed by a thyristor controlled rectifier system connected to a 6 KV, 2 MVA transformer. The tunnel operation, air speed, model positioning and parameter measurements are controlled from an integrated control panel. 12 INCAS BULLETIN No 1/ 2009 DOI: 10.13111/2066-8201.2009.1.1.3

Exit Flow Behavior of Axial Fan Flows With/Without Impingement

The exit flow patterns of an axial flow fan widely used in electronics cooling are experimentally characterized both in free exit and in the presence of a flat impingement plate. The axial fan is rotated with 12.0 V input from a dc power supply, leading to a nominal Reynolds number of Re=9.0×103 based on fan diameter. One shear layer each is found to form between the exit flow from the axial fan and the surrounding fluid at rest, and between the exit flow and the flow along the fan axis. In addition to creating a highest wall pressure region (the primary stagnation region), the presence of the flat plate induces a flow recirculation zone (the secondary stagnation region) at the plate center. When the fan exit-to-plate spacing normalized by fan diameter (H/D) equals to about 0.6, the wall pressure is minimized in the secondary stagnation region due to the maximized “recirculation” as a result of intensified flow interaction. Within the range considered (0.2≤H/D≤2.0) and with the case of H/D∼0.6 serving as a reference, the flow interaction tends to be suppressed by the proximity of the plate at H/D=0.2 and weakened due to the momentum dissipation at H/D∼2.0.

Profile Scaling of Miniature Centrifugal Fans

This paper addresses issues that relate to downscaling the height of centrifugal fans for application in low profile technologies, such as the cooling of portable power electronics. The parameters studied include flow rate, pressure rise, and power consumption characteristics. The former two of these are measured using a fan characterization rig and the latter by directly measuring the power supplied to the fan. These are studied for fan diameters ranging from 15 to 30 mm with numerous profile heights between 0.3 mm and 15 mm. It is found that all of the phenomena encountered are best described in terms of fan aspect ratio. The results show that the conventional scaling laws cannot be accurately applied when blade profile alone is scaled. Indeed, the only parameter reasonably well predicted was the pressure rise attainable, but that was only accurate for fan aspect ratios greater than 0.17. Below this, the pressure rise generated reduces logarithmically toward zero. The study also reveals that no advantage is gained by using fans of aspect ratio greater than 0.3, as the maximum flow rate attainable decreases slightly above this. Overall, the scaling phenomena reported herein provide invaluable information for the future design of efficient low-profile cooling solutions that are to incorporate such fans.

Thermal Management of Low Profile Electronic Equipment Using Radial Fans and Heat Sinks

There is an increasing need for low profile thermal management solutions for applications in the range of 5–10W, targeted at portable electronic devices. This need is emerging due to enhanced power dissipation levels in portable electronics, such as mobile phones, portable gaming machines, and ultraportable personal computers. This work focuses on the optimization of such a solution within the constraints of the profile and footprint area. A number of fan geometries have been investigated where both the inlet and exit rotor angles are varied relative to the heat conducting fins on a heat sink. The ratio of the fan diameter to the heat sink fin length was also varied. The objective was to determine the optimal solution from a thermal management perspective within the defined constraints. The results show a good thermal performance and highlight the need to develop the heat sink and fan as an integrated thermal solution rather than in isolation as is the traditional methodology. An interesting finding is that the heat transfer scales are in line with turbulent rather than laminar correlations despite the low Reynolds number. It is also found that while increasing the pumping power generally improves the thermal performance, only small gains are achieved for relatively large pumping power increases. This is important in optimizing portable systems where reduced power consumption is a competitive advantage in the marketplace.

Operation features of the diametrical disc fan at low pressures

Operation of the diametrical disc fan was studied experimentally at low (5–50 torr) pressures in air. The effect of a drastic decrease in volumetric flow rate of the fan was revealed at pressures below 40 torr (flow rate crisis), what does not correlate with published data. The critical value of dimensionless parameter corresponding to flow transformation and formation of a closed flow inside a fan was determined and proved experimentally.

Design, construction and performance of a large tornado simulator for wind engineering applications

A laboratory tornado simulator was designed, constructed and tested to generate tornado-like vortices for the purpose of quantifying tornado-induced aerodynamic loads on civil engineering structures. This simulator generates a vortex that can translate along a ground plane to interact with models of structures on the ground. The simulator uses a “rotating forced downdraft” technique that loosely matches the rear flank downdraft (RFD) phenomenon often emphasized as important to tornadogenesis. The rotating forced downdraft is generated using a 1.83 m diameter fan and an annular duct suspended from an overhead crane that can translate along a 10.4 m ground plane. Measurements were conducted to quantify the simulator’s flow structures. An 18-hole pressure probe was used to traverse and map the vortex flow field. The flow structures of the vortices were validated by comparing with mobile Doppler radar observations of two major tornados. Results show that tornado vortex radii from 0.23 to 0.56 m can be generated. A wide range of maximum tangential velocities are also possible (from 6.9 to 14.5 m/s). The simulator generates a range of vortex structures from single-celled vortices to two-celled vortices with corresponding swirl ratios ranging from 0.08 to 1.14. Comparisons of general flow structure and normalized profiles of tangential velocity showed excellent match between simulator and radar data. The range of tornado sizes together with model structures of 1/100 to 1/500 scale will allow extensive examination of tornado-induced wind loads on terrestrial structures. The effects of a tornado’s size, translation speed and detailed flow structure on these loads can now be studied.

Flow through aerodynamic torque converter installed in new type turbofan engine

It is desired to increase the core engine speed of the turbofan, to get the best efficiency for the next leap of the engine technology. The conventional mechanism in which the front fan is directly connected to the output shaft of the core engine has a limit of increasing the spool speed because the fan diameter is very large. The authors have proposed a new driving system in which the front fan is driven through the aerodynamic torque converter. The front fan can work at the conventional speed while the core engine runs more efficiently at higher speed. Continuously, in this paper, the flow through the converter is simulated numerically by CFX-5 with the k-e turbulence model of the commercial CFD code. The secondary flow occurred on the hub wall affects markedly the flow condition on the blade surfaces, and the flow along the suction surface of the driver blade separates near the trailing edge, which is deviated to the blade tip by the centrifugal force due to the wheel rotation.

Sugarcane Chopper Harvester Extractor Fan and Ground Speed Effects on Yield and Quality

Operational settings on chopper harvesters are extremely important in green-cane harvesting since one is relying solely on the harvester to remove extraneous matter instead of the traditional pre-harvest burn method. The objective of this research was to determine the combined effect of selected ground and fan speeds on sugar yield, cane quality, and field losses using a commercial chopper harvester. In both 2003 and 2004, a split-plot experiment was performed at harvest with the main plots having ground speeds of 4.0, 4.8, and 5.6 km h-1 and subplots having primary extractor fan speeds of 650, 850, and 1050 rpm of the 1.5-m diameter fan. Under the optimal conditions (low leaf and soil moisture), the 1050 rpm fan speed increased theoretical recoverable sugar (TRS) by 10% but decreased cane yield by 15% compared to the two lower fan speeds resulting in similar sugar yields for all fan settings. Under poor conditions (high leaf and soil moisture), the 1050-rpm fan speed decreased cane yield by 13% without an increase in TRS, resulting in lower sugar yields than the low or medium fan settings. Ground speed, under both conditions, did not affect cane yield or quality. The chopper harvester performed well under ideal conditions with a primary fan speed of 1050 rpm but had decreasing performance under poor conditions regardless of fan speed.

Determining Fan Performance Using FANS: An Investigation of Performance Impacts

Emission rates of gaseous pollutants from intensive livestock housing are obtained as the product of gas concentration and the ventilation rate. Much effort has been expended developing methods to measure gas and particle concentrations; however accurate in-situ air flow measurements have always been particularly problematic. A Fan Assessment Numeration System (FANS) can be used in the livestock houses to obtain an in-situ calibration of each fan in its exact configuration including shutters, louvers, and discharge cones. An evaluation of the typical mode of use of the FANS to determine the fan performance characteristic for fans between 450- and 1290-mm diameter is reported. The FANS is placed directly in front of the fan to be tested, sealed to minimize air leakage and a single measurement taken at each static pressure is reported. The determination of fan airflow with FANS is very repeatable (within 0.26% of nominal reading), indicating that replicated tests are not required. There was no 'penalty' associated with the FANS when testing fans with diameters of 915 mm or less, or 1220-mm diameter fans with capacities of less than 34,000 m3 h-1. Based on limited testing, a significant 'penalty' could exist for fans with diameters larger than 1220 mm or with higher performance characteristics. When using a FANS to determine the performance characteristic of a fan with a diameter greater than 1220 mm, the 'penalty' should be determined by evaluation in a fan test facility. For fans significantly smaller than the FANS unit, test results suggest that no transition is needed.

Fast drying of Fine Needle Aspiration slides using a hand held fan : Impact on turn around time and staining quality

To analyze the impact of using a hand held fan to speed the air-drying process during immediate adequacy evaluation of Fine Needle Aspirations. The effect on turn around time and staining quality is evaluated.Two mirror image air-dried smears for each pass were prepared. One was subjected to a small hand-held fan with a fan diameter of 7 cm held an average distance of 3 to 5 cm from the slide. The other smear was left to dry without a fan. A total of 93 consecutive pairs were evaluated over a 2-month duration.The average time needed for air-drying using the fan was 73 seconds (range 10–300 seconds, standard error 6.986), while it was 200 seconds (range 15–645 seconds, standard error 17.799) for those without fan. This difference was statistically significant (p < 0.001). Smears were then evaluated for single cells, cell clusters and background material and no appreciable difference in stain quality was noted between the 2 groups.The use of a small hand-held fan for air-drying shortened the drying time for FNA adequacy by an average of 127 seconds (63% time reduction) for each pass. The quality of staining was comparable. Using a fan is highly recommended.

Unsteady operation of new type turbofan engine with aerodynamic torque converter reducing front fan speed

It is desired to increase the rotational speed of the core engine of the turbofan so as to get the best efficiency for the next leap of engine technology. The conventional mechanism in which the front fan is directly connected to the output shaft of a core engine, have a limit of increasing the spool speed, because the fan diameter is very large. The authors have proposed a new driving system in which the front fan is driven through the aerodynamic torque converter. The front fan can work at the best performance at slower speed while the core engine runs more efficiently at higher speed. Continuously, this paper discusses the response of the front fan in the unsteady operation of the core engine, accompanying with the internal flow. The system has the acceptable responsibility in the unsteady operation which is very important for the aircrafts.

Effects of PPV Attack on Thermal Conditions in a Compartment Downstream of a Fire

There have been relatively few technical studies conducted on the effects of PPV on compartments downstream of the fire. Live fire tests in an acquired house were conducted in order to study the effect of PPV attack on the thermal environment downwind of the fire. Temperature measurements were made using 40 thermocouples located in a fire room, hallway, and downstream room referred to as “the victim room”. Video camera and infrared camera images were taken in several locations to visually record the progress of the fire and firefighting. A total of eleven cases are reported in this study. These cases correspond to three different fan configurations: no fan, a 45.7 cm (18″) diameter fan with a volumetric output of 3.06 m3/s (6,500 CFM), and a 61 cm (24″) diameter fan with a volumetric output of 4.31 m3/s (9,130 CFM). Two venting strategies were used: venting the fire room and venting the victim room. Fluctuations in environmental factors such as wind and the inherent statistical variation common in fire testing made it difficult to draw many absolute conclusions. In general, however, we found that cases with fire room venting and fan application had somewhat higher fire room or hallway temperatures when compared to cases without fan application. We also found that cases with victim room venting and fan application resulted in higher gas temperatures in the victim room at the higher elevations than both fire room vented cases and cases without fan application.

Airtightness testing of very large buildings: a case study

The airtightness of a building envelope impacts upon uncontrolled air leakage, associated ventilation energy losses and occupant thermal comfort. The scale of these problems in large buildings would be expected to increase in relation to the potential size of possible leakage areas. Recent changes to UK Building Regulations have required new, large, nondomestic buildings (/ 1000 m2 floor area) to meet a specified standard of airtightness. A building’s airtightness is conventionally assessed using a steady state fan pressurization technique. There was some discussion in the airtightness testing industry that the upper practical limit of large buildings capable of being tested might be around 5000 m2 due to technical issues relating to fan size, power requirements, transportation and noise. The feasibility of testing very large buildings (over 5000 m2) with a steady state fan technique has been questioned. This paper demonstrates that such testing is feasible by describing the development, calibration and application of a 2 m diameter fan pressurisation system. The fan was tested on the largest building in the world (floor area 57 440 m2) ever to have its airtightness determined by steady state fan pressurization. Practical Application: The changes to Building Regualtions Part L2 that came into effect on 1st April 2002 raised the profile of the pressure testing of large buildings for airtightness. There were doubts raised concerning the feasibility of pressure testing very large buildings but the paper demonstrates that it is technically and practically possible.

EFFECT OF WINDBREAK WALL LOCATION ON VENTILATION FAN PERFORMANCE

Windbreak walls may be installed downstream of ventilation exhaust fans to block wind or deflect exhaust airupwards. Little information is available on the effects these walls have on fan performance. Six agricultural ventilation fansof various sizes were tested with a 2.9m high wall located at several positions downstream. There was no significant reductionof fan performance if the wall was located at least 4x fan diameters downstream. Among the fans tested, airflow was reduced10 to 19% when the wall was located 2x fan diameters or less downstream. Fan ventilating efficiency was affected slightlymore than airflow performance.

University of Waterloo Live Fire Research Facility

Every year in North America, fire accounts for a significant number of deaths, injuries, and capital losses, as well as the related economic burdens of fire insurance, fire suppression and building fire protection systems. Indirect costs of fire due to emissions to the environment and groundwater contamination are immeasurable. These costs can be reduced through the development of fire-safe products, advancements in detection, suppression and fire fighting methodologies, and the development of innovative equipment for the fire protection and response industries. With this aim, University of Waterloo researchers from the Departments of Mechanical Engineering and Applied Health Sciences, together with the fire service in their region and other municipalities across Canada, have conducted collaborative fire training and research exercises for over a decade. A unique synergy has developed, leading to direct transfer of technology to the broader fire service community; however, it is very difficult to access facilities in which controlled, realistic, large-scale, live-fire research can be conducted. To address this need, a $5.6M, state-of-the-art Live Fire Research Facility is being constructed by the University of Waterloo with shared funding from the Region of Waterloo, the City of Kitchener, the Canadian federal and Ontario provincial governments and industry. The research facility is an integral part of a larger Region of Waterloo Emergency Services Training and Research Complex, situated on a 16 ha. site, minutes from the UW campus. The major fire research infrastructure at the Facility includes • a large-scale fire research area with capability for generation and control of ambient winds and ventilation conditions, • leading edge diagnostics and instrumentation for scenario monitoring, control and data acquisition, • a large cone calorimeter and ISO room fire test area, • a small cone calorimeter, smoke density chamber, flame spread and flammability apparatus for testing the fire performance of materials, and • laboratory facilities for small and medium-scale fire research/analysis and the study of physiological impacts of fire fighting. The large-scale fire test area is 3,975 ft and 4+ storeys high. It is designed to accommodate a two storey house or other large-scale burn experiment. It consists of an outer enclosure with a moveable, inner steel burn ‘house’ in which fires can be set. Rooms in the house can be reconfigured, lined with representative materials and furnished as appropriate for a particular test fire scenario. Ambient crosswinds from 0 to Copyright © International Association for Fire Safety Science 114 20 mph can be generated by a bank of six, 72 inch diameter fans with a plenum/flow straightening system leading to a 20 ft × 24 ft opening into the main test area. The crosswinds flow around the ‘house’ (or other fire experiment) and exhaust through a large overhead sectional door at the far end of the enclosure. Also in the main test area are a 2 MW calorimeter and an ISO room fire test area situated adjacent to a 10 ft × 10 ft exhaust hood. A 3,385 ft conventional building is attached to the large-scale test area. It houses the main control room, general support services, a small-scale fire test laboratory and a physiological research lab for researchers from Applied Health Sciences. Fullscale studies of fire behavior in the burn ‘house’ can be complemented by laboratory studies of the fire performance of materials (heat release rate, smoke generation and ignition, and flame spread characteristics) and the effects of the fire environment on fire fighting personnel. Experiments in any part of the Facility can be instrumented for velocity, temperature, pressure and species concentration measurements with a variety of fixed and portable systems. Video and infrared visualization, laser/phase Doppler particle anemometry, particle image velocimetry, Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry systems are also available. Research efforts will focus on the application of basic principles of fire science to areas such as the movement of smoke and heat in full-scale structural fires, fire initiation, heat release rate and spread, flammability and fire performance of materials and components, fire safety, equipment and methodologies for fire detection and suppression and health issues in the fire service. Combined with the existing fire and diagnostics laboratories on the main University of Waterloo campus, this new Facility will allow advancements in fundamental fire research, as well as full-scale investigations with direct application to fire service and fire safety issues, performance-based building codes and occupational health in the fire service.

Fan Size and Energy Efficiency

The use of ceiling mounted circulating fans to provide air movement for cooling in industrial premises and animal houses is particularly essential in warm, humid climates. Methods to substantially improve the efficiency of this approach are demonstrated in this paper. Fan laws are identified as one source of strategies for increasing energy-efficiency of fans. Industrial ceiling fans are used to demonstrate that using larger, slower, fans will not only improve energy efficiency but also reduce fan noise. By using large diameter fans (7.3m diameter) in place of conventional fans, energy savings of over 40% are demonstrated. Field studies of air flow characteristics from ceiling fans are shown to provide further opportunities to increase air flow efficiency in industrial buildings. Utilising lower friction losses associated with the Coanda effect in air flow adjacent to the floor is shown to increase air flow toward the outer limits of the radial outflow. Lower fan mounting heights are also shown to provide increased air flow toward the outer limits of the radial outflow. For situations where the floor plane has numerous obstructions to air flow, CFD software is suggested as a means to simulate air flow before installation of fans. Where possible, validation of CFD software output against physical measurements is advised.

Turbofan engine database as a preliminary design tool

A large database of currently manufactured turbofan engines with a bypass ratio of at least 2.0 was compiled in 1996. Key parameters (dry weight, length, fan diameter, nacelle diameter, cruise thrust, air mass flow, bypass ratio, total pressure ratio, take-off specific fuel consumption, and cruise specific fuel consumption) were plotted, most as a function of take-off thrust. The resulting plots are a rich source of basic information, which can be used to quickly define an engine for use in a preliminary airplane design. The database is sorted by take-off thrust and can also be used to determine if an existing engine can be used in the proposed airplane. Relationships are suggested for use in preliminary design.

Noise control as a revenue enhancer

A small (1.6-MW) power plant was designed to a very strict noise specification. As the various noise sources in plant design iterations were reduced in level, the engine coolers emerged as important noise sources. Noise design requirements dictated that the cooler fan tip speed be significantly reduced. Cooling requirements led to a necessary increase in fan diameter and thus general size of the cooler tube bundles and support structure, at greater acquisition cost. However, the slower fans required smaller electric drive motors. The reduced parasitic load of the smaller motors enabled the plant to export more electric power for revenue. The added investment in quiet fans was recouped in 13 months of operation.

Pink Bollworm Mortality Using Large-diameter, Gin-trash Fans

Processing gin trash through flat-blade centrifugal fans to kill pink-bollworm larvae (pectinophora gossypiella Saunders) has long been an accepted method of control. Specifications for the operation of pink bollworm fans from 48.3 to 82.6 cm (19 to 32.5 in.) diameter are part of USDA, APHIS regulations. Gins are now being built that use pink bollworm fans up to 107.3 cm (42.24 in.) in diameter. It was necessary to determine pink bollworm mortality using the larger diameter fans. Results indicated that fan tip speeds above 3,962 m/min (13,000 ft/min) resulted in 100% mortality of pink bollworm larvae contained in green bolls regardless of fan wheel diameter.

Design and Performance of a Horizontal, Axial-Flow Water Circulator

An axial-flow water circulator was developed for use in channel catfish, Ictalurus punctatus, culture ponds. The circulator design incorporated a series of 0.76-m diameter fan blades housed within a belled inlet duct 0.92 m in diameter and 1.22 m in length. Power was provided by a 2.24-kW gear motor. Power demand and discharge rates were established using all combinations of the following design variables: impeller type-three blades set at 30' angle or six blades set at 25' angle; impeller speed-90, 120, 144, and 180 rpm; number of impellers in series-1, 2, 3, or 4. The highest discharge rate of 63 m3/minute was established using four six-blade impellers operating at 144 rpm. A maximum discharge rate per unit of power input (efficiency) of 91.4 m3/minute-kW was obtained using two three-blade impellers operating at 90 rpm. Circulator efficiency decreased with increasing discharge rates as described by the model Y = 12888.8X-1.68315, where Y = m3/minute-kW and X = m3/minute. Field tests conducted in 1.62-ha channel catfish production ponds demonstrated the ability of the circulator to increase water movement in all areas of the ponds and to reduce the frequency and total duration of required emergency aeration by 39.3% and 54.6%, respectively. Net production of channel catfish in ponds outfitted with the water circulator (6,683 kg/ha, n = 3) was not different (P > 0.05) than production in control ponds (6,205 kg/ha, n = 3).