NDLI: Does fan blades require cyclic pitch when in push configuration inside telecommunication chassis?

Content Provider	IEEE Xplore Digital Library
Author	Roknaldin, F.
Copyright Year	2004
Description	Author affiliation: Appl. Thermal Technol., Santa Clara, CA, USA (Roknaldin, F.)
Abstract	It has been realized that fan tray does not function in push configuration in telecommunication chassis when inlet height is smaller than certain value. Originally this was associated with excessive pressure drop due to flow turn inside inlet plenum or basically bottle neck pressure drop through inlet opening it self, however, the problem became worst when higher pressure capacity fans were used. In latter, total CFM increased, as expected, but slot to slot as well as front to back airflow distribution became very uneven, leaving few slots starving. CFD simulations were used to understand this flow behavior, however, they were not capable of duplicating the measured airflow distribution. In this work, this problem is presented and analyzed by means of aerodynamic theory of fan blades. It is shown that high speed flow through small inlet do not turn completely, but rather, enter the fan tray at shallow angle. This causes one side of fans to be ineffective leaving slots over those portions starving. Even the effective sides of fans produce directional jets leaving rear portion of those boards directly above them starving. By bringing knowledge from helicopter aerodynamics to fan blade design, the cause for this mysterious behavior was discovered. Consequently, the concept of fan blade cyclic pitch is introduced as possible solution to this problem. Next generation fans might be designed to have variable blade angle within each revolution. Other implication of this work is to lay out building blocks for better CFD model for fan that include some blade aerodynamic effect. This will be the subject for future work.
Sponsorship	Components, Packaging and Manufacturing Technol. Soc. of the Inst. of Elec. and Electron. Eng
Starting Page	165
Ending Page	170
File Size	585491
Page Count	6
File Format	PDF
ISBN	0780383575
DOI	10.1109/ITHERM.2004.1319169
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2004-06-01
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Blades Computational fluid dynamics Fans Testing Thermal management Aerodynamics Neck Fluid flow measurement Helicopters Switches
Content Type	Text
Resource Type	Article

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