Testing of Fans with Microperforated Housings

Transcription

1 Purdue University Purdue e-pubs Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering Testing of Fans with Microperforated Housings J Stuart Bolton Purdue University, bolton@purdue.edu Seungkyu Lee sklee36@purdue.edu Follow this and additional works at: Bolton, J Stuart and Lee, Seungkyu, "Testing of Fans with Microperforated Housings" (2013). Publications of the Ray W. Herrick Laboratories. Paper This document has been made available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information.

2 Tes)ng of Fans with Microperforated Housings Seungkyu Lee and J. Stuart Bolton Ray W. Herrick Laboratories Purdue University 1/26

3 Acknowledgement The author acknowledge the support of 3M Corpora)on through the provision of materials for the fan noise test and the financial support for this work. 2/26

4 Outline Objec)ves Literature Review Experimental Set Up» Fan Specifica)on» Housing Materials» Fan specifica)on and performance curve Measurement Results» Sound Power Level spectrum and Cumula)ve Spectrum» Blade Passage Tone level values» Contour Plots Conclusion 3/26

5 Objective v To reduce the blade passage tone level of axial cooling fan (120 mm)» Focusing on reducing )p clearance noise. v Tip noise can be reduced by installing a finite flow resistance strip in the housing around the fan circumference.» Finite level of flow resistance created by the slightly Permeable housing may reduce turbulence levels in the )p region. v The fan noise was quan)fied on the basis of the blade passage tone level. Tip region 4/26

6 Literature Review Structural Design of the Fan: Strut designs, etc.» W. M. Gresho (1985)» J. Wang and L. Huang (2005)» S. Lee, G- S Lee, S. Heo and C. Cheong (2005) Impact of the guard grille design» A. Gregor, M. Hocevar and B. Sirok (2009) Ac)ve noise control» D. A. Quinlan (1992)» K. L. Gee and S. D. Sommerfeldt (2003)» J. W. Schulz, W. Neise and M. Moser (2006) 5/26

7 Literature Review Tip Clearance region» G. Jin, H. Ouyang, Y. Wu and Z. Du (2011): Blade Design» L. Gorny, G. L. Koopmann, W. Neise and O. Lemke (2011): perforated resonator within the housing» D. L. Sutliff and M. G. Jones (2009): Beneficial effect of foam metal liner in turbine blade- )p. Foam Metal 6/26

8 Experimental Equipment Setup INCE Plenum (ISO 10302) Controllable opening Plenum designed based on ISO The test plenum is intended for measuring the flow rate and the fan sta)c pressure. Controllable opening from 2x2 cm 2 to 10x10 cm 2 to control flow resistance. 7/26

9 Experimental Equipment Setup Hemispherical Frame Configuration v 10 Microphone posi)ons on equal areas on the surface of a hemisphere to measure sound power. [ISO 3744] v Radius of hemispherical frame is 5.5 k. v Test equipment including the hemispherical frame was set up in the anechoic chamber at Herrick Laboratories. 8/26

10 Fan Specification Model: 4710KL- 05W- B20 Characteris)c Curve Manufacturer provided Specifica)on Rated V olt [V] Opera)ng Voltage [V] Current [A] Input Power [W] Speed [RPM] Max Air Flow [m 3 /min] Max. Sta)c P ressure [Pa] Noise [db] Mass [ g] ~ /26

11 Fan design Modified fan to amach the housing materials Microperforated casing amached! 10/26

12 Materials Impermeable (Regular) MPP 751 Rayls Impermeable Casing MPP 1204 Rayls MPP 1759 Rayls MPP Casing 11/26

13 P-Q Curve and Operating Points 2x2 cm 2 3x3 cm 2 5x5 cm 2 7x7 cm 2 10x10 cm 2 MPP used for comparison - - Flow Resistance: 751 rayls MPPs with higher flow resistance than 751 rayls gave similar performance curve as Regular Casing 12/26

14 P-Q Curve and Operating Points Pt. Pressure [Pa] Opening Area [cm 2 ] Flow Rate [m 3 /min] Fan opera)on Speed [RPM] x x x x x x x x x x Fan opera)on condi)on for comparison ü Rota(on speed was controlled by giving different input voltage 19V, 21V and 23V of input voltage ü Flow exit area was varied from 2x2 to 10x10 cm x x x x x /26

15 Measurement Procedure Pick a measurement point from P- Q curve Operate the fan amached to plenum at required voltage (speed). Acquire noise signals from 10 different microphone posi)ons. ü Sampling )me: 120 sec; Sampling rate: 25.6 khz Signal processing ü Power Spectral Density ü Welch s method of PSD ü Hann Window ü 50% overlap Calculate sound power level according to ISO /26

16 Sound Power Level Calculation The Sound Power Level es)ma)on from the sound pressure level L w = L p +10log 10 S L p : Space averaged sound pressure level S ref S ref : Reference area, 1 m 2 S : Surface area of the hemisphere 10 microphone arrays for the sound power level es)ma)on [ISO 3744] 15/26

17 Acoustic Measurement Results Point # x2 cm 2 Opening Area High Pressure (17.8 Pa) / Low Flow Rate (0.05 m 3 /min) At Blade Passage Frequency Region Blade Passage Frequency Region 16/26

18 Acoustic Measurement Results Point # x3 cm 2 Opening Area Mid Pressure (12.03 Pa) / Low Flow Rate (0.21 m 3 /min) At Blade Passage Frequency Region 17/26

19 Acoustic Measurement Results Point #7-5x5 cm 2 Opening Area - Mid Pressure (9.58 Pa) / Low Flow Rate (0.49 m 3 /min) At Blade Passage Frequency Region 18/26

20 Acoustic Measurement Results Point #11-7x7 cm 2 Opening Area - Mid Pressure (8.23 Pa) / Mid Flow Rate (0.88 m 3 /min) At Blade Passage Frequency Region 19/26

21 Acoustic Measurement Results Point #13-10x10 cm 2 Opening Area - Low Pressure (4.49 Pa) / High Flow Rate (1.25 m 3 /min) At Blade Passage Frequency Region 20/26

22 Blade Passage Tone levels 21/26

23 Blade Passage Frequency Tones Area [cm 2 ] Point BPF [Hz] Regular [dba] MPP751 [dba] MPP1204 [dba] MPP1759 [dba] Actual Sound Power Reduced! % 2 x % % % 3 x % % % 5 x % % % 7 x % % 10 x % % % 22/26

24 Reduction of Sound Power at BPF Regular and MPP 751 Regular and MPP 1204 Regular Sound Power Percentage and MPP - Regular and 1759 MPP Sound Power Percentage - Regular and MPP 751 Sound Power Percentage - Regular and MPP Pressure [Pa] 10 Pressure [Pa] 10 Pressure [Pa] Flow Rate [m^3/min] Flow Rate [m^3/min] Flow Rate [m^3/min] Reduc)on of Sound Power: ü Actual Sound Power was used in comparison L = 10log w 10 Red region: BPF tone was reduced by using MPP casing Blue region: BPF tone was increased by using MPP casing P P 0 P : Sound Power P 0 : Reference value, 1 pw 23/26

25 Final Comments on the results Red : MPPs with High flow resis(vity showed beser performance in reducing BPF tone Blue : MPPs with Low flow resis(vity showed beser performance in reducing BPF tone 24/26

26 Conclusion Detailed experiments in reducing the Blade Passage Frequency tone level of the 120 mm fan using microperforated materials were conducted. Repeatable and accurate measurement procedure was established and achieved reliable results. Microperforated panel casing reduced the Blade Passage Frequency tone level of the fan. ü MPPs with flow resistance of 751 rayls and 1204 rayls reduced BPF tone level for most of the opera)ng condi)on Different flow resis)vity of MPP is required to reduce the Blade Passage Frequency tone of the fan that operates at different opera)ng condi)on. 25/26

27 Future Plan Provide guidelines for design treatments that can be integrated into typical fan design. Sugges)ng the op)mal design of the fan for bemer reduc)on in the noise level. ü Op)mal flow resis)vity of the housing ü Bemer structural design; the struts and bell mouth of the fan. 26/26