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