BULLETIN FA-300. February 1999 AXIAD II. Adjustable Pitch Airfoil Axial Flow Fan

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1 BULLETIN FA-300 February 1999 AXIAD II Adjustable Pitch Airfoil Axial Flow Fan

2 AXIAD II The axial flow fan with: High efficiency Low sound level Adjustable pitch blades Complete range of accessories Axial flow or centrifugal fan? Efficiency, sound level and adaptability are factors which must often be weighed against space requirements and investment, installation and service costs when choosing the type of fan for a particular application. The AXIAD II simplifies the choice. AXIAD II has an efficiency of up to 85%. When downstream guide vanes are used, the maximum efficiency of the AXIAD II is very high, even higher than that of belt driven centrifugal fans. Centrifugal Fan Type FC Impeller Type BI Impeller Axial Flow Fan Without With AXIAD II costs less to buy. The AXIAD II is less expensive than a conventional belt driven centrifugal fan. Usually it costs no more than an ordinary axial flow fan. Cost Fan Efficiency Belt Drive Net 65% 80% 75% 85% AXIAD II is simple and inexpensive to silence. Axial flow fans are usually noisier db than centrifugal fans, but on the AXIAD II the difference is no more than a few decibels. In addition, the sound has a higher frequency and has no single tones. So the cost of silencing is usually as low as that for a centrifugal fan. AXIAD II is compact. The AXIAD II is appreciably more compact than an equivalent centrifugal fan if fitted with a diffuser. AXIAD Diffuser AXIAD II is easy to adapt. The AXIAD II has adjustable pitch blades for adjusting the fan to the required airflow and pressure. Just slacken two screws, turn the blade to the required angle and retighten. Axial Flow Fan Centrifugal Fan Hz Belt Driven Centrifugal Fan Type FC Impeller Type BI Impeller AXIAD II costs less to run. High efficiency and the lack of a belt drive combine to ensure low operating costs. The comparison is made at the best efficiency of each fan. Cost Belt Driven Centrifugal Fan Type FC Type BI Impeller Impeller AXIAD II costs less to service. The AXIAD II is direct driven. It has only two bearings, which do not carry the load of a belt drive. This ensures optimum reliability and thus a minimum of service costs. Axial Flow Fan Conventional With Vanes Less Vanes AXIAD II (+) ( ) Axial Flow Fan Conventional AXIAD II AXIAD II also has: A standard foot mounted motor. High strength cast aluminum blades. A lightweight impeller (low bearing load). A complete range of accessories. Simple vibration isolators. It does not need costly inertia bases or concrete foundations. Cost Belt Driven Fan AXIAD II 2 Aerovent Bulletin FA-300

3 Features Available in 11 sizes from 22" to 55" diameter. Airflows from 2000 to 100,000 CFM Static pressure capabilities to 14" w.g. Aerovent is proud to introduce the AXIAD II fan. This fan is the culmination of a design effort to produce a low noise adjustable pitch axial flow fan with high efficiency, compact size and simple blade adjustment. The AXIAD II fan has been researched both aerodynamically and acoustically in AMCA approved computerized laboratories. The result is a fan that produces low sound power level when compared to other standard axial flow and centrifugal fans. The compact size occupies less space than comparable centrifugal fans and the straight-through airflow design provides installation savings. The blade adjustment mechanism is of simple yet strong design consisting of two bolts and a clamp. To change pitch angle it is necessary merely to loosen the bolts, turn the blade to the proper angle, and retighten the bolts. This provides ease of adjustment and assurance that position will not change. The hub of the fan is index marked for each blade angle. The correct blade position is indicated on the performance curves and corresponds to the hub markings. The adjustable pitch blade feature permits easy system balancing or adjustment for unpredictable duct losses. It also permits changing fan characteristics to match changing job conditions. Since the blades can be changed in pitch approximately 35, a wide variation in performance is possible. Compared with airfoil centrifugal or tubular centrifugal fans, AXIAD II fans are much lighter in weight, requiring only simple isolators instead of concrete inertia bases. AXIAD II fans are also more compact, occupying considerably less space than centrifugal fans. The standard AXIAD II fan has an internal direct connected electric drive motor. A variety of full load speeds is possible, giving wide size selection possibilities. The direct connected motor also eliminates cumbersome V-belt drives, and the adjustable pitch blade design eliminates changing pulley sizes to obtain capacity changes. Because the AXIAD II rotor is a high efficiency design, the fan can be supplied with or without the discharge vane section. This feature allows further refinements in fan selection, making economy in first cost and operating expense a certainty. Without Vane With Vane Section Aerovent certifies that the AXIAD II fans shown herein have been tested and rated in accordance with industry accepted test codes, and are guaranteed by the manufacturer to deliver rated performance. Contents Guide to AXIAD II Performance Charts AXIAD II Nomenclature Fan Selection Fan Curve Sizes: Fan Curve Sizes: Sound Data Corrections Guide to Simplified Selection Charts & Tables Annular Velocity Charts Impact Loss and Velocity Pressure Curves Dimensions Aerovent Bulletin FA-300 3

4 Guide to AXIAD II Performance Charts This bulletin presents AXIAD II axial fan performance charts, which show in graphical form volume (CFM), pressure (in. w.g.), efficiency, blade position, and fan brake horsepower (BHP) relationships encountered in the most common AXIAD II fan, rotor and blade combinations operating at motor speeds associated with 60 Hertz operation (900, 1200, 1800, and 3600 RPM). Data on other sizes of fans and fans operating at different speeds is available from the factory. A typical AXIAD II performance chart is represented above. You will notice that the charts are presented on the basis of total pressure. The pressure shown as total pressure is the sum of static pressure, velocity pressure, and impact pressure loss. Static pressure is generally given, while velocity pressure and impact pressure loss are calculable by methods explained elsewhere in this brochure, and at greater length in other Aerovent publications. The operating point of a fan can be determined by knowing any two of the six parameters plotted in the fan charts. Generally, selections are made by establishing total pressure and reading across the total pressure line (in. w.g.) to the intersection with the volume (CFM) line; and noting the blade position and efficiency. BHP is established by reading down the volume line to the previously established blade position, locating the brake horsepower by reading horizontally across the chart. In selecting an AXIAD II fan it is best to choose a size that will operate at a point that is in the vicinity of the maximum efficiency oval. An important consideration in fan selection is the relation of the selection point to the stall line. The stall area is located at the upper end of the blade angle lines and must be avoided. Fan operation in this area is unstable, producing vibration, hunting and surging. To ensure avoiding the area, fan selections should use only 90% of the available pressure at the specified flow. Calculation of a system parabola will show that only by allowing this safety margin can an error involving underestimation of static pressure be corrected by the relatively simple method of increasing blade angle. AXIAD II Nomenclature FTFA (+) MOTOR SPEED Fan Size With Vane Section, ( ) = Less Vanes Full Bladed, if 1 = Half Bladed Hub Size will be 3 with 6 or 3 Blades 4 with 8 or 4 Blades 5 with 10 or 5 Blades 4 Aerovent Bulletin FA-300

5 Fan Selection Straight-Through Airflow in Any Direction The data presented in this manual allows the reader to arrive at a fan selection, starting with airflow, pressure, and downstream duct velocity of the system. Generally, for any given set of the above conditions, there are a number of fans that are possible selections. The parameters for separating these selections are generally (1) brake horsepower, (2) acoustics, and (3) first cost. The table below shows nine possible selections to meet the conditions: 40,000 CFM, 2.5 inches static pressure, discharging into a plenum at 500 feet per minute. It may be of value to the reader to use the selection pressure calculations, efficiency calculations, and brake horsepower calculations. The sound data shown here is presented on the fan curve, and this is correctable to octave band readings as shown on pages 42 through 44. The weight that the designer gives to each of the factors involved in selection is something that varies with each individual case. One would note from perusing the data that fans number 1 and 2 are the most compact, fans number 3 and 4 are the least expensive, fans number 5 and 9 are the quietest, and fans number 8 and 9 take up the greatest amount of space and tend to be very expensive. Under normal circumstances we suggest that the designer, after thoroughly investigating the nine possibilities, would tend to narrow them down to fan number 3 versus fan number 5. In this case, the designer must balance a 10% HP savings and 6 db lower noise output of the FTFA with diffuser against a cost differential approximately 40% which favors the FTFA The final selection should be the result of a thorough systematic cost analysis that your Aerovent representative will be happy to assist you with. Example Given: Flow = 40,000 CFM Static Pressure = 2.5" w.g. Discharge Condition: into Plenum, V4 = 500 FPM FAN FAN VANE TOTAL EFFICIENCY OVERALL RELATIVE OUTLET RPM BHP NO. FTFA SECTION PRESSURE PERCENT PWL COST NO CONE NO CONE NO CONE NO YES DIFF YES DIFF YES YES DIFF Aerovent Bulletin FA-300 5

6 Performance Data FTFA Aerovent Bulletin FA-300

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8 Performance Data FTFA Aerovent Bulletin FA-300

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10 Performance Data FTFA Aerovent Bulletin FA-300

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41 Performance Data FTFA , Aerovent Bulletin FA

42 Performance Data FTFA Sound Power Correction Factors The Correction Factors shown below are to be added to the total Sound Power found on the appropriate fan curve, (i.e. for RPM, 10,000 CFM, 0.7" total press. Lwt = 86 the correction at 250 Hz is 7. Therefore the corrected PWL at 250 Hz = 79 db. OCTAVE/BAND HERTZ CENTER FREQUENCY FAN RPM 1/63 2/125 3/250 4/500 5/1000 6/2000 7/4000 8/ (+) (+) (+) (+) (+) (+) (+) (+) ( ) (+) (+) ( ) (+) (+) ( ) Aerovent Bulletin FA-300

43 Sound Power Correction Factors FAN RPM OCTAVE/BAND HERTZ CENTER FREQUENCY 1/63 2/125 3/250 4/500 5/1000 6/2000 7/4000 8/ (+) (+) ( ) ( ) (+) (+) ( ) ( ) (+) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) Aerovent Bulletin FA

44 Sound Power Correction Factors FAN RPM OCTAVE/BAND HERTZ CENTER FREQUENCY 1/63 2/125 3/250 4/500 5/1000 6/2000 7/4000 8/ ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) ( ) ( ) (+) Aerovent Bulletin FA-300

45 Selection of AXIAD II Axial Flow Fans Using Simplified Selection Charts Vaneaxial fans are usually rated in terms of total pressure (pt), total pressure being the sum of the system static resistance (ps), plus the velocity pressure (pv) in the duct leaving the fan. In the case of AXIAD II fans, the total pressure shown on the individual fan curves is as measured in the annulus of the vane section, so we have to add the impact loss (pi) to ps and pv to arrive at pt. This is done because the impact loss varies to a considerable degree with variations in discharge duct geometry. All of this is discussed in detail in our brochure Vaneaxial Fan Characteristics and Application Fundamentals. That brochure presents a more accurate method for computing these discharge or impact losses, and this method is used at the factory to check selections on orders before they are manufactured. However, a simplified method would be more desirable for the use of consultants and sales representatives, and this bulletin presents such a method. The enclosed data will permit quick selections and performance comparisons between alternate selections. This method will give you the total pressure within 2% of the computed figure arrived at from the formulas in the brochure. Guidelines for Use of Simplified Selection Tables To select an axial flow fan using the simplified selection charts, it is only necessary to know: 1. Airflow (CFM) 2. Static pressure (SP) 3. Approximate duct velocity downstream of the fan With this information you can make an initial selection of fan size and then verify, using the attached charts, that the selection is a good one or that an alternate size should be chosen. If a single fan system is to be selected, it is desirable to pick the operating point at the area of maximum efficiency. Selection in this part of the curve insures economical operation and good sound characteristics. Since job conditions and calculated requirements do not always agree, it is necessary to allow a safety factor in pressure and flow when making the selection so the fan can do more if field conditions so require. For this reason, do not select a fan at more than 90% of the rated pressure shown on the curve at design flow, and do not select a fan at higher than the maximum indicated blade position. If fans are to be selected to operate in parallel, care must be taken so that fans which come on while the system is operating do not pass through the dip in the fan curve, which is the stall region. To prevent this condition, parallel fans should be selected so that the system curve crosses the maximum blade setting line at a point below the level of the dip. This procedure is necessary to avoid the possibility of the last fan to be started having to pass through the dip in the stall envelope above the performance curve. Since this fan must come up to the system operating pressure before it can contribute to system flow, there is a possibility, if the fan is not selected in this manner, that it may go into a stall condition and not perform as expected. How To Select Fans To make a simplified selection, proceed as follows: 1. Using the individual fan performance charts (higher static pressures require higher RPM), make a tentative selection of fan diameter and hub size. Remember that total pressure will typically be 1" to 3" higher than the static pressure. 2. Using Chart 3 and 4, enter at the bottom with CFM, go up vertically to the tentative fan selection, and then read left to determine V1, the air velocity in the annulus of the fan. 3. Determine velocity pressure (pv), and impact loss (pi) from Chart 5 (if you do not intend to use a diffuser) or Chart 6 (if there will be a diffuser). In either case, enter the chart with the duct velocity downstream of the fan, rise to V1 ascertained in Step 2, and read left for pv + pi. If the fan discharges into a plenum, use the velocity in the cross-sectional area of the plenum as duct velocity. If a sound trap is located in the plenum, use the normal face velocity through the trap as duct velocity. Add pv + pi to your static pressure to arrive at pt. P1 can now be used directly on the individual fan curve to confirm that the selection is a good one or that it should be revised. 5. If the selection is to the left of the optimum efficiency, you may have too large of a fan, and should try the next smaller diameter. If the selection is well below the point of optimum efficiency, you may have selected too large of a hub size, or perhaps a fan with fewer blades will prove more efficient. In making alternate selections, retrace Steps 2, 3, and 4 for your new fan size. Aerovent Bulletin FA

46 AIRFLOW (CFM) CHART 3 ANNULAR VELOCITY (FPM) 46 Aerovent Bulletin FA-300

47 AIRFLOW (CFM) CHART 4 ANNULAR VELOCITY (FPM) Aerovent Bulletin FA

48 pv + pi (inches W.G.) FPM Duct Velocity (V3) pv + pi for FTFA Axial Fans WITHOUT DIFFUSER OR CONE 48 Aerovent Bulletin FA-300

49 pv + pi (inches W.G.) FPM x 100 Duct Velocity (V4 or V5) pv + pi for FTFA Axial Fans WITHOUT DIFFUSER OR CONE Aerovent Bulletin FA

50 Dimensional Data C-D Diffuser and Cone Annular Fan Casing Diffuser AA AA Size LC CL Cone Outlet Area Sq. Ft. EE FF R S T Overall Diff. Cone Inlet Outlet Area ID Area Hub: DD = For Size < 125 BB = AA + 1.5" BB (1) = AA (1) + 1.5" 4 Hub: DD = For Size > 125 BB = AA + 2.0" BB (1) = AA (1) + 2.0" 5 Hub: DD = C-D Diffuser Cone 50 Aerovent Bulletin FA-300

51 Dimensional Data Adjustable Pitch Vaneaxial Fan Fan Size All dimensions in inches A B C D E F G H J L N S T U X Aerovent Bulletin FA

52 Quality Air Handling Equipment AIR HEATER ROOF VENTILATOR CENTRIFUGAL VANEAXIAL AXIAL FLOW Tubeaxial Type VT Industrial Exhaust Upblast Propeller Panel Fan Type W Adjustable Pitch CB / CBA Upblast Axial Mancooler Type VTF Fiberglass Series 14 High Pressure Tu-WAY Ring Fan Type B Higher Pressure Centaxial Fiberglass Tubeaxial Adjustable Pitch Axico Anti-Stall Pressure Blower PRV Centrifugal Gas-Fired Air Make-Up Steam Air Make-Up Door Air Heater WARRANTY Aerovent equipment is guaranteed to deliver its rated output, if properly installed and operated under normal conditions. Aerovent will correct by repair, replacement, or issuance of credit at our option, F.O.B. our plant, defects in material or workmanship which may develop under normal and proper use within eighteen (18) months after date of shipment from our factory, if purchaser gives us notice within ten (10) days of discovering such defects. The correction of these defects by repair, replacement, or issuance of credit shall constitute fulfillment of all obligation to purchaser. (NOTE: We will not assume expense or liability for repairs made outside our factory without prior written consent.) 3MPP08/06 TM