5015 fan silencer by FullPlasticScientist

Last crawled date: 3 years, 3 months ago

Inlet silencer for 5015 blowers.
See bottom for original listing.
----V3 DESIGN UPDATE 2020-11-18---
Another version, same as V2 except:
15mm tall instead of 11.3mm for longer helocid to block line of sight to fan blades completely.
Simplified inner cone for wider flow area and lowest impedance.
some fine geometric refinements to fan inlet, eg smaller cone base.
Made a simplified version with no damping o-ring.
Made a M10 or 1/8thBSP vacuum port inlet version. Experimental for use as as 02 delivery system. Treat as untested/unsafe and use with extreme caution. Potential fire hazard!
----V2 DESIGN UPDATE 2020-11-06---
Made a V2 simplified option with no o-ring groove feature and minimal footprint to allow it to be fitted to a greater variety of printer setups.
----V2 DESIGN UPDATE 2020-10-31----
Thanks to detailed and constructive feedback from esoterik, see comments, I have produced an updated design. Optimised for lower impedance and hence less impact on fan output.
-Modal barrier removed, 4 resonant modes now down from 8
-Velocity stack/venturi OD flared for lower flow impedance
-Toroidal blades wider for lower flow impedance
-2.7mm shorter for tight installation requirements
----FUTURE WORK----
Build flowrate, pressure and acoustic testrig. Using arduino, custom printed venturi flow meter fitted with an RC plane differential sensor MPXV7002DP. Acoustically silenced chamber (eg old fridge turned off) to measure noise (Db) without background interference. May also add accelerometer to characterise spectrograms/scaleograms of resonant modes. So that designs can be made to manipulate resonant modes precisely.
--Test microporous toroidal blades
--Radially patterned angular flared holes around stack OD
--Resonant hidden side chambers in stack OD and cone body, see paper ref at end of listing.
--Different number of toroidal blades for more modes
--Construct a table of flow impedance vs acoustic damping so users can select appropriate levels for their application.
--Adapt for other fan sizes and types
--Make adjustable outlet, eg plane aircon nozzle, using best techniques.
----ROUND 2 FIGHT!----
This is a backburner project as part of a clear mask pressure and flow regulated ventilation system. All critical and constructive feedback is greatly appreciated. If I am not replying immediately its because I'm currently mustering my remaining resources to face Corona head on, one more time, to protect my family and community in the UK. When the opponent is exponential our efforts to counter attack must also be exponential.
Join me #CoronaSlayers for one last push to #HackThePandemic
PRINT & SHARE, until Corona is done!
----ORIGINAL LISTING----
Designed for a clear mask positive pressure system being developed for the https://www.thingiverse.com/thing:4598055
That application required near silent operation at greater than 100% rated voltages. In order to achieve pressure necessary to blow air through a highly restrictive clear mask inlet filter and develop net positive pressure inside the mask trapped volume. A mini PAPR system. In use for several weeks in an office environment with no complains from co workers.
So should work for noisy 5015 3D printer fans too. Check your airflow after fitting.
Features:
Short venturi / velocity stack cone inlet
Modal barrier to break up resonance into 8 separate modes, thus reducing peak intensity of primary fan resonance.
4 way toroid with no sight line to fan
Converts linear airflow to radial as the blower wants
Gap at inlet to fan blades matched to radius of blower fan.
Smooth transition into fan blade leading edge to reduce local high pressure pockets that generate resonance.
Cut out at bottom of toroid to allow air mixing void just before blower fan blades.
Increases efficiency whilst also reducing resonant noise.
O-ring seal groove for a 1.5mm cross section 40mm ID 43mm OD o-ring
Dampens vibration and improves inlet seal
Reduces contact area on first printing layer, no more torn borosilicate using petG!
O-ring optional, silencer will still mount and work fine if not fitted.
Small chamfers on bottom of part, to compensate for elephants foot.
Oversized holes for M4 cap heads to account for differences in blower housing manufacture.
No supports or bridging required. Part is its own support. If toroidal vanes are not 100 solid it may be microporous, this is an advantage as micro porous acoustic silencers are far more effective.
Material doesn't really matter
I print in 0.2 layer height but best results will be 0.1 or nearest magic number. Relatively quick to print. All other settings as per your preferences.
Best used with a dual ball bearing or sleeved bearing fan variant. Avoid cheap winsinn hydraulic bearing fans. Unreliable and the hydraulic bearings give off a high pitched whine this silencer cannot combat. The ball and sleeved bearing 5015 blowers types do not.
This review paper and related literature on toroidal silencers made with additive manufacturing techniques as inspiration.
"Assessment on the use of additive manufacturing technologies for acoustic applications"https://link.springer.com/article/10.1007/s00170-020-05853-2