1、OR-05-14-1 (RP-1 O1 O) Test Fan ID # 36x 14 An Experimental Study of the Effects of Inlet Plenum Walls on Axial Fan Performance Blade Rotational Blade Data No of Hub Diameter Frequency Number Tip Angle O Vanes in. (mm) DHT Hz 10 1,9, 16,24 8 14.0 (356) 0.39 297 William B. Swim, PhD ABSTRACT This exp
2、erimental study determined the degradation in performance of large axial fans caused by close inlet walls. Three fans with hub to tip ratios of 0.39, 0.49, and O. 74 were each tested at four blade angles and over the jlow rate range of wide open to near shutof The closest walls, 0.5D front clearance
3、 and OD side clearance, caused only modest loss in flow rate, up to 3%, and less than a 5% loss of eficiency in the 0.49 H/Tfan. The other two fans had only minor decreases injlow rate and in eficiency for the closest walls. No signij- cant losses were foundfor any of the test fans when tested with
4、clearances larger than the minimum. INTRODUCTION ASHRAE has a strong and continuing interest in helping develop an understanding of the potential degradation of the noise and performance of fans when installed in realistic, non- ideal, air-handling systems. This degradation of performance, termed sy
5、stem efect, has been used by the technical commu- niy in system design with only limited success. And the noise penalty of non-ideal installations has been mostly guided by personal experience of the designer. This study was initiated by ASHRAE as Research Project 1010, ?Inlet Installation Effects,
6、Air and Sound, on Vaneaxial Fans,? to contribute to the understanding of inlet system effects on axial fans. Noise and performance measurements were made on three 36 in. (914 mm) diameter, variable pitch axial fans with nominal hub diameters of 14, 17, and 26 in. (360,430, and 660 mm). Each of the t
7、hree fans was tested at four blade angles, providing ?12? test fans. These test fans are described in Table 1. Table 1. Test Fans Used on RP I010 Project Type: Joy Series 1000 Axivane Fans Model Numbers: 36-1 4-1 780,36- 17- 1780,36-26- 1780 Fan Nominal Diameter, D: 36 in. (914 mm) Manufacturer: New
8、 Philadelphia Fan Company Fan Motors:1780 RPM (29.7 Hz) Impeller Tip Diameter, DT: 35.9 in. (912 mm) 36x 17 1 12 3,10, 18,25 I 9 1 17.5 (444) I 0.49 1 356 36x26 I 16 15,22,30,37 I 13 I 26.5 (673) I 0.74 I 475 William B. Swim is professor emeritus of Mechanical Engineering at Tennessee Technological
9、University, Cookeville, Tenn. 02005 ASHRAE. 993 Test Wall Positions Test Wall ID Numbers r Movable Tes! Wall Nozzle Chamber Figure 1 Test fan nomenclature and test setup geometry Figure 2 Isometric view of 61,700 ft (1 740 my reverberation room setup for ASHRAE RP-IO10 fan tests. The 12 fans were te
10、sted using 10 test-wall positions designed to simulate the effect of installing fans in close prox- imity to the walls of an inlet plenum. Figure 1 describes the L- shaped test wall as well as the locations and the identification numbers of the 10 test-wall positions. The 120 tests of this project c
11、overed the fan flow rate range from free delivery to near shutoff with data collected at 9 to 11 test points or deter- minations for each test. The test fan sizes, as shown in Table 1, are identified as 36 x 14, 36 x 17, and 36 x 26. The wall positions are identified as WP1 through WP10, as shown in
12、 Figure 1. TEST METHODS The noise measurements were made in a large reverber- ation room with the free inlet of the fan fitted with an inlet bell and inlet screen. The exhaust of the test fan was ducted to an adjacent nozzle chamber where flow rate and static pressure rise were measured. An auxiliar
13、y fan on the exhaust of the nozzle chamber was used to control the back-pressure on the test fan. The test components, test fan, test wall, and micro- phone traversing unit, are illustrated in the isometric drawing of Figure 2. The performance measurements were made 994 ASHRAE Transactions: Symposia
14、 following Figure 12 of AMCA Standard 210-99 (ASHRAE Standard 51-1999). The noise measurements were made in accordance with AMCA Standard 300-96. The L-shaped test wall was used to simulate plenum walls close to the front and the side of the fan inlet. The test wall, constructed of 2 x 4 stud framin
15、g covered with heavy, 6 mil (O. 15 mm) Visquene sheeting, measured 123 in. (3 124 mm or 3.4D) along the fan axis, 159 in. (4039 mm or 4.4D) across the front of the fan, and 144 in. (3658 mm or 4D) in height. The photograph in Figure 3 shows the 36 x 26 fan mounted for testing while Figure 4 shows th
16、e test wall installed at the fan inlet. The fan and three test wall positions are shown, as located in the reverberation room, in Figure 5. The test wall was moved in increments from a “free” inlet condition, at 5D in front and 5D to the side of the fan inlet (WPl), to the worst case, where the wall
17、 was closest to the fan inlet, %D in front and OD to the side (WP2). The performance and noise were measured for each test-wall position, first at free inlet condition, identified as wall position 1 (WPl), then at position 2 (WP2), the worst case. The eight other wall posi- tions, WP3 through WP10,
18、followed in order. The test-wall positions, listed in Figure 1 , provided three sets of three front-clearance positions (not counting WP 1). Following the free inlet test, the side wall was moved to zero clearance and tests were conducted at three front wall clear- ances-OSD, D, and 1 SD. The side w
19、all clearance was then set to 0.5D, and tests run at D, 1.5D, and 2D front clearance. Figure3 Photograph of the 36 x 26 fan mounted for testing. Figure 4 Photograph of a fan and test wall setup for test. 30 ft, O in. (9140mr9) d Air Measuring Chamber (for Exhoust Hode Fons) Not Used For RPlOlO Il 8
20、in. (200nri) Air 14-osuring Charber (Fut Supply Mud? Turi Ceiling H?ight 18 ft. 6 in. (5640mm) 71 ft. O in. (21600mm) w Microphone Swing Path 12 ft. O in. (3660mm) u 10 fi. (3050mm) High Figure 5 Plan view of reverberation room and adjacent nozzle chamber: ASHRAE Transactions: Symposia 995 Figure 6
21、Photograph of test wall at WP2, the closest position to the fan. The third set, at side wall clearance of D, was also tested at front wall clearances of D, 1.5D, and 2D. A photograph of the test walls at WP2, the closest to the fan inlet, is given in Figure 6. Each test started at the free delivery
22、operating point and stepped through eight additional test points, spaced approxi- mately in equal steps in flow rate, to near the shutoff condition. The final test point was stall recovery (SR), the operating point where the fan operation first became smooth and steady as the back pressure was slowl
23、y reduced from the near-shutoff point. DATA ANALYSIS The data analysis and interpretation focused on the five or six highest flow rate determinations as these test points were judged to cover the normal, useful operating range of the fans. The results were evaluated using the premise that the free-i
24、nlet condition should yield the best performance and the lowest noise for each of the twelve test fans. It was also assumed that moving the test walls closer to the fan inlet could not improve the performance or reduce the noise but, rather, at best, the fan output, airflow, and noise might remain u
25、nchanged. Further, based on prior evidence, the closest test-wall position was expected to have the largest impact, causing a significant reduction in fan performance and a large increase in fan noise. Fan total pressure and fan total efficiency were plotted versus fan flow rate for the four blade a
26、ngles-one figure for each of the three hub sizes. These trends are illustrated in Figures 7, 8, and 9, which compare the performance of the twelve test fans with a free inlet-the trace identified by solid triangle test-points-to the worst case, the closest wall posi- tion-identified by open square t
27、est-points. The consistency of the trends and the near parallel shapes of most of the perfor- mance curves indicate that the performance measurements were generally repeatable, and the results seem to reflect the performance behavior of these fans with the close inlet walls. The analysis of the flui
28、d dynamic data on all 120 fan test configurations produced no strong, consistent performance trends that covered or fit all 12 test fans. The aerodynamic performance of the “four” 36 x 14 fans is shown in Figure 7. These fans suffered only small decreases in performance, ranging from O to less than
29、2% with the closest wall position. The 36 x 17 fan had the largest performance losses, from 2% to 3.5%, with the closer walls as shown in Figure 8. Figure 9 shows the 36 x 26 fans were nearly unaf- fected by the proximity of the test walls to the fan inlet, having less than a 1% performance loss and
30、 less than 1 point effi- ciency loss in going from free inlet to the closest wall position. Since the closest wall had only %D front clearance and OD side clearance, these small and sometimes insignificant perfor- mance losses were rather surprising. The performance loss for the 12 test fans, caused
31、 by the wall position with smallest inlet clearance, Y/D of 0.5, were converted to the system effect factor (SEF) and displayed in Figure 10. The SEF, defined in AMCA Publication 201-90, is a measure of the drop in a fans ideal rating performance curve, caused by non-ideal inlet or outlet configurat
32、ions. AMCAs SEF chart gives a means of predicting the performance loss due to real-world geometry imposed on the fan. The RP- 1 O 1 O results for the closest front wall position, WP2 where Y/D = 0.5, are plotted on a duplicated section of AMCA Figure 7.1. The 36 x 17 fan loss follows the AMCA “Y cor
33、relation line for an inlet wall at YD = 0.5 reasonably well. However, the other two sizes had measured losses smaller than that predicted by Figure 7.1. Both the 36 x 14 and the 36 x 26 fans losses were significantly below the AMCA correlation line. CONCLUSIONS AND RECOMMENDATIONS The performance fa
34、ll-off with the closest test wall was very small for the 36 x 26 fan, small for the 36 x 14 fan, and only moderate for the two largest blade angles on the 36 x 17 fan. The flow rate fell less than 1% for the 36 x 26 fan, 0% to 1.2%forthe36x 14fan,and3%to3%forthe36x 17fan. Flow losses at inlet cleara
35、nces larger than %D were too small to effectively measure. Efficiency losses ranged from 4.7 points for the 36 x 17 fan to less than 1 point with the 36 x 26 fan. The efficiency data for the 36 x 14 fan were too scattered to reach a conclusion on efficiency loss. The pressure losses for the 36 x 17
36、fan at the closest wall condition were reasonably close to the system effect factor (SEF) correlation given on Figure 7-1 of AMCA 201-90 for a front wall clearance of %D. But the losses at increased wall clearances were too small and scattered to fit on the AMCA SEF correlation chart. The correlatio
37、n of the measured losses for the 36 x 14 and the 36 x 26 fans with AMCA 201 were poor, as Figure 7-1 predicted larger losses than were found by these experiments. Improved test methods of simulating an inlet plenum need to be developed. It is also suggested that a more responsive set of test fans be
38、 used in any future system-effect studies. 996 ASHRAE Transactions: Symposia Fan Flow Rate, Q, cfm (Lls) Figure 9 Performance of 36 x 26 axial fan with IS“, 229 309 and 37“ blade tip angles REFERENCES AMCA Standard 21 0-99/ASHRAE Standard 51-1999, Labo- ratory Methods of Testing Fans for Aerodynamic
39、 Perfor- mance Rating. Air Movement and Control Association International, Inc., Arlington Heights, IL. AMCA Standard 300-96, Reverberant Room Method for Sound Testing of Fans. Air Movement and Control Association International, Inc., Arlington Heights, IL. AMCA Publication 201-90, Fans and Systems.
40、 Air Move- ment and Control Association International, Inc., Arlington Heights, IL. William B. Swim, Final Report on ASHRAE Research Project 1010, Inlet Installation Effects, Air and Sound, on Vane Axial Fans, ASHRAE, Atlanta, August 2003. DISCUSSION Charles Wayne Frazell, Engineer, Pritchard & Abbo
41、tt, Fort Worth, Tex.: I believe, as mentioned in the conclusions, that the use of a plastic sheet wall absorbed sound, making the results invalid. 998 ASHRAE Transactions: Symposia 1 .o0 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.0s O.OE 0.07 O.OE O.O! 0.01 o. o: 0.0: 0.0 10 V 20 30 40 50 60 70 80 90 AIR VELOCITY, FPM IN HUNDREDS Figure 10 System effectjactor chart from AMCA 201-90 with values for RP-I010 fans at Y/D = 0.5 and Del. 4. X 1 O0 ASHRAE Transactions: Symposia 999
