NOISE REDUCTION FOR INTERNAL COMBUSTION ENGINE Chris Morehouse: Team Leader Julie Maier: Resonator Lead Ted Zachwieja: ANC Lead Caroline Bills: Lead Engineer Prof. Edward Hanzlik: Team Guide Dr. Alan Nye: Customer Mr. Jagdish Tandon: Graduate TA P11221 NOISE REDUCTION FOR INTERNAL COMBUSTION ENGINE

Project Overview Understand phenomenon of sound Design sound attenuation system(s) Maintain engine performance

CUSTOMER NEEDS

ENGINEERING SPECIFICATIONS

Design Options HELMHOLTZ RESONATOR CONCENTRIC TUBE RESONATOR ABSORPTION MUFFLER ACTIVE NOISE CANCELLATION

RESONATOR DEMONSTRATION MODULE Study of resonators Variable cavity lengths (both) 2 outer pipe options (Concentric Tube only) CONCENTRIC TUBE RESONATOR HELMHOLTZ RESONATOR

RESONATOR TESTING Concentric Tube: Helmholtz: Vary Frequency Vary Length Waveform Helmholtz: Vary frequency Waveform CONCENTRIC TUBE RESONATOR TONE GENERATOR (LAPTOP) SOUND LEVEL METER SPEAKERS

CONCENTRIC TUBE FIXED FREQUENCY TEST RESULTS Predicted: Max at ½ λ ~ 20 to 30 dBA Result: Max 6 dB Offset Reduction at ½ λ > ¼ λ SCT similar results SCT less reduction than LCT for most

CONCENTRIC TUBE FIXED LENGTH TEST RESULTS Predicted: Max at ½ λ Less at ½ λ multiples ~ 20 to 30 dBA Result: Offset from λ multiples Max ~ 10 dBA (550 Hz) SCT similar results SCT less reduction Possible sources of error: Exact location cavity length (o-ring or plunger end) Possible weird wave motion in plunger rod section

HELMHOLTZ RESONATOR FIXED FREQUENCY TEST RESULTS Prediction: Modest reduction (at least 10 dBA) Narrow Frequency Range Result: Reduction offset Achieved expected level

WAVEFORM TESTING RESULTS target peak frequencies for each resonator C-Tube – around ½ λ for each F Helm – freq equation

CONCENTRIC TUBE RESONATOR RESULTS Optimal = 26 cm Overall ~ 9.6 dBA Optimal based on reduction at peaks and overall reduction Modest attenuation across broad frequency range

HELMHOLTZ RESONATOR RESULTS No clear optimal Overall reduction ~ 0 dBA Behavior of resonator – narrow frequency band Possibly array

Absorption Muffler: overview Outer steel casing Perforated inner steel pipe 5 shapes Steel end caps Packing material in cavity 3 materials 3 densities

Absorption Muffler: material & density options Fiberglass Mineral Wool Steel Wool Fiberglass & Mineral Wool: 175, 200, and 225 g/L Steel Wool: Grades 0000, 1, and 4 Mineral Wool – made from molten glass, stone, or slag which is spun into a fiber-like structure similar to common household insulation Steel Wool grade - determines the thickness of the strands in the steel wool

Absorption Muffler Testing Test 1: Optimal Packing Material & Density Standard Shape Option only Test 2: Optimal Shape Optimal Material & Density only

Optimal material Results

Optimal shape Results

Active Noise Cancellation Additive property of sound Noise cancellation

Dipole Box

Feed forward Control

Project Evaluation Resonator Demo Absorption ImagineRIT Resonator behaved as expected Waveforms testing success Absorption Steel wool better material Geometry needs further testing ImagineRIT Successful Lots of positive feedback Back pressure testing Inconclusive Overall = success Very good knowledge gain Good start for follow-on projects SAE Recommendations Steel Wool packed muffler Concentric Tube Resonator

RECOMMENDATIONS Resonators Absorption ANC Variable length for testing on ICE Array of Helmholtz resonators Optimize concentric tube for Formula SAE Nature of Offset Absorption Composite Material layering Continue Steel Wool Density Testing ANC Complete working system (demo) Apply to B&S Engine Develop Feedback system Develop prediction models for all Design Back Pressure testing system Engine Mounted w/ Engine Loaded

Questions?? References: Bell, Lewis H. Industrial noise control: Fundamentals and Applications. New York : M. Dekker, 1982. Print. http://students.sae.org/competitions/formulaseries/rules/2011fsaerules.pdf http://focus.ti.com.cn/cn/lit/an/spra042/spra042.pdf ANC patent on EDGE website