Transcript Poster4.ppt

Noise Reduction in Over-molded HVAC Module Doors
Industrial Sponsor:
Goal: Create a component and or system
Result: Eliminated acoustic whistling
design that will eliminate any acoustic
signal audible to automobile passengers.
with the experimentally proven Tear-Drop
Design.
Problem Statement
Design Recommendation
Design Requirements
During the initial 5-15% rotation of an HVAC bypass temperature door from its sealed to unsealed
position, a whistling noise is generated from air
flowing between gaps created by door’s seal and
HVAC housing in panel full cold mode.
ο Eliminate the acoustic whistle
ο Size must remain within 101.6 x 50.8 x
19.0, +/- 0.2 [mm]
ο Ease of Manufacture
ο Low Cost
ο Minimal number of parts
Noise Reducing Tear-Drop Design
ο Minimal effect on housing
ο Available for mass production
ο Service life exceeds 10 years
ο Adaptive to existing platform
ο Reliable and robust
Stimulated Vortex Generation and
Sound Radiation
Whistling Is
Audible to
Automobile
Passengers
A-Side ByPass Door
Existing HVAC Door Module
Airflow to Passengers
Initial investigation focused on
decreasing the air velocity between
the by-pass door and HVAC housing
oHousing
o Inexpensive and easily mass produced.
Why it Works
oVortex Drift Velocity (Vd)
= 0.8 x FlowVelocity
Resonance Conditions for Stimulated Vortex Generation and Sound Emission
Time for a vortex to reach Housing = L/Vd
Vortex Shedding Period T=5d/V
Time for pressure pulse to reach door= L/c
Condition for Resonance is L/Vd=5nd/V
Total time= L/Vd + L/c  L/Vd
Existing Door
o Easily Manufactured with existing Injection Overmolding with minimal retooling
oFlow Separation
BEHR
Previous Investigation
o Total Added Volume – 441.5 mm3.
oHigh Flow Velocity
Provided by:
HVAC Unit
o A-side seal edge receives Tear-Drop Extension.
Existing By-Pass Door
Resonance Occurs when: L=4nd
A-Side
Benchmark
Values
Increased Seal Tip diameter:
o Changes the conditions of resonance for Stimulated Generation.
o Minimizes boundary layer separation by increasing seal-tip radius
o Minimizes vortex formation thus resonant feedback.
Whistling
Vmax =28.5 m/s
Vavg= 10.3 m/s
Tear-Drop Design
Resonant Sound
Waves
Waved Design
Waved Results
B-Side
Experimental Validation
Vmax = 28.8 m/s
Over-molded By-Pass Temp. Door
By-Pass Temperature Door Specs.
Mfg. Process: Injection Over-molding
Door Material: Hard Plastic Seal
Material: 35 Grade Sanoprene
Vavg= 10.4 m/s
1.Air boundary layers encounter:
i) Large pressure gradient between the plenum and channel.
Door-seal’s small tip diameter.
Ribbed Design
Ribbed II.
Results
ii)
1B. The turbulent boundary layer separates from the door and forms air vortices and sound.
Vmax = 21.8 m/s
2. Sound (Pulsed Pressure) is reflected from the housing providing a feedback mechanism to
stimulate the formation of air vortices.
Vavg= 8.9 m/s
3. Feedback increases the intensity of emitted sound creating the acoustic whistle.
Outer Dimensions: 27 x 20 x 5 [mm]
(length x width x seal thickness)
Whistling Still Remained!
Team Members: Aaron Kleinow (Industrial Advisor), Dr. Giles Brereton (MSU
Faculty Advisor), Bethany Danielski, Andrew W. Siefert, and Matt Warner
Clay Molding
Clay Molded By-Pass Door
o Conceptual designs were modeled by
molding clay to the existing door platform.
o Doors were tested in HVAC under operation
conditions producing whistling.
o Results were analyzed and the best design
was optimized.
o Tear-Drop Design was validated by tested
prototype (not pictured)
Existing Door Platform
Clay Molding