P Formula Exhaust Acoustic Tuning Design Review – Week 5 Greg Wodzicki Kyle Desrosiers Brad Fiedler Chris VanWagenen

Agenda  Introduction / Background  Problem Statement  Customer Needs  Engineering Specs  Understanding the Problem and Current Technology  Concept Review  Test Bench  Closing  Questions

Problem Statement  Formula SAE rules state exhaust noise volume must be lower than 110 dB before allowing a team’s car to compete. Any vehicle that does not pass may be modified and retested until it passes. Current muffler design is glass pack, which is often repacked at competition to lower the noise level within spec. The purpose of this project is to provide the RIT Formula team with means to lower their exhaust noise consistently and more predictably. Introduction / Background

Problem Background  FSAE rules dictate engine noise under 110dB.  Current Passive Noise Control device does not involve extensive design.  Packing material deteriorates over usage time and noise attenuation decreases throughout season. Introduction / Background

Current Glass Pack Design  Not currently heavily designed area of car  Packed/repacked onsite at competition to pass  Summer 2010 scored ~102 dB at competition  Life: ½ season before glass melts and attenuation becomes less affective  Used as reference for concepts explored Source: P11221 Introduction / Background

Original Design Objectives Design system to cancel sound output without sacrificing performance to:  Bring Engine sound under FSAE limit of 110dB.  Adhere to all FSAE Rules  To not add Significant weight to Vehicle  Maintain/Improve engine performance Introduction / Background

Customer needs Customer Need # ImportanceDescriptionComments/Status CN19Reduce the sound level of RIT's Formula SAE engine to meet the legal formula level CN29Be able to demonstrate RIT's Formula Car will pass FSAE Sound Regulations CN33Prove concept of sound acoustics (i.e. attenuation, freq shift, etc) CN41Obtain needed understanding of acoustics and sound waves CN51Obtain needed understanding of Engine Characteristics (i.e. firing freq, Sound characteristics, torque power) CN61Analyze data and identify optimal areas of improvement CN89Maintain Engine Performance (torque, horsepower) CN99Maintain Vehicle Performance (weight, battery reserve, size, Vibration) CN103Demonstrate feasibility of active noise cancellation on IC Engine (Test Stand) CN113 Understand the fundamental sources of noise generation from the normal operation of an IC Engine. (1. Discrete frequency sources, 2. broad band or white noise sources) CN123Propose noise reduction methods for each source CN139Easily fixed during competition (if breaks) CN141Lower center of gravity by location of exhaust system CN153Resilience of design (lasts at least half a season)

Engineering specs Engineering Specifications ES #ImportanceSpecification (Description) Unit of Measure Marginal Value Ideal Value Comments/StatusPerson ES 19Reduce noise leveldBA ES 29Maximum length extending from rear axlein SAE Rules ES 39Maximum distance above the groundin SAE Rules ES 49Passes B10.3 of the SAE Formula rules dBA, fast weighting 110<110SAE Rules ES 53System Power DrawWatts ES 61System Lifehours ES 73Component Costs$ Cheap as possible ES 81Exhaust Envelope (volume of space)ft 3 Discuss with SAE team ES 99Internal Exhaust Components Survivable Temp°F Discuss with SAE team ES 109 Internal Exhaust Components Survivable Pressure psia Discuss with SAE team ES 113Component Shock Thresholdg Discuss with SAE team ES 123Change in Engine Max PowerHP 0 Change in power must be justified by significant improvement elsewhere ES 131Weight limit on exhaust systemlbs 8Approximately equal to current ES 143Maximum allowed back pressurepsi Define from analytical data/literature research

Understanding the Problem  Sound Waves (see Figure 1)  Superposition  Human Auditory Range (frequency)  Harmonics  Four-stroke engine (see Figure 2)  Cycles: intake, compression, power, exhaust  Noise Sources  “Chatter”  Intake  Exhaust- Main source  Firing Frequency (See Fig 3)

Glass Pack  Exhaust Travels through Pipe with Perforated Holes  Sound Insulation Absorbs Sound  Minimal Back Pressure  Least Effective in Reducing Sound Concepts

Multi-pass Muffler  No Baffles  Exhaust Forced to turn back and forth  Increases Exhaust Length  Increased Back Pressure with each turn  Sound Insulation Absorbs Sound  Moderately Effective in Reducing Sound Concepts

Baffle Muffler  Reflects Exhaust Throughout Chamber  Reflections Cancel each other  Most Back Pressure created  Greatest Sound Reduction Concepts

Elimination of Baffle and Multi-Pass Pros:  Multi-pass provides better attenuation than glass pack.  Baffle (chamber style) muffler provides even better attenuation than multi-pass. Cons:  Multi-pass increases exhaust back pressure  Baffle style will cause the most back pressure of all the design concepts. Baffle and multi-pass are quieter, but increase backpressure. It has already been seen that Glass Pack can achieve FSAE limit with lower backpressure Concepts

Variable Length Resonator  Engine Traditional Resonators are tuned to address particular range of frequencies Generally target the most problematic (loudest) frequencies As engine speed changes, exhaust frequencies change Variable length resonator addresses wider range of frequencies Cons: Adds weight Waves reflect in accordion (baffles) FSAE states system must be tested in all positions. If not at the ideal position for a given frequency, the resonator will do nothing to attenuate sound

Parallel ANC with Microphone and Feedback Courses of Action

Multiple Speaker with Error Microphone Courses of Action

Exhaust in Speaker Chamber

Performance Objective Possible Performance Effects of Active Noise Cancellation Technology:  A – No Exhaust Tuning  B – Traditional Exhaust Length Tuning  C – Possible Active Noise Cancellation Improvement* * Dependent on cancellation method Introduction / Background

Risk Assessment Risk #Description of RiskPossible Consequences Overall Risk (81 = high) Preventative MeasuresContingency Plan 1 FSAE Engine is occupied or non- functional Lack of data from formula car9 Constant communication with RIT Formula team (Taylor Hattori) Test exclusively on lawn mower engine 2Microphone not functionalCan not record engine waveform9 Keep in safe place, handle with care, use appropriately New Microphone 3Lawn mower engine failure Can not record engine waveform, can not test designs 27 Check oil level before each use, otherwise maintain engine properly Use backup engine 4 Non-ideal testing conditions (rain, noisy, etc) Equipment ruined, testing delayed 27Keep an eye on weather conditionsReschedule Testing 5Lack of budget Design not able to be created spring quarter 27 Ensure each aspect of the design is designed as cost effectively as possible Borrow parts, see what is available from various labs 6 None of the muffler designs reduce sound within the target range Project fails9 Use best available, most feasible design Explain why designs did not work as expected. 7 Materials/mufflers are destroyed/ruined during testing. Sound absorption of design is reduced. 27 Purchase excess material, incorporate factor of safety into designs Purchase excess material.

8 Lack of scientific knowledge surrounding signal processing Deliverables missed, sound not attenuated 9 Use simple components and software that we have existing knowledge of or can readily learn Find expert to assist in signal processing. Simplify design by removing some components. 9 Engine noise (non-exhaust) is not negligible for lawnmower engine. Sound reading not accurate.9 Make sure measuring sound according to SAE rules. Insulate engine "chatter" from microphone 10ANC design is improperly calibrated ANC muffler actually creates more sound rather than attenuates sound. 81 Have a system that is able to be modified and recalibrated. Re-calibrate and try again. 11Deviation from project timeline. Fall behind on project objectives 9 Allot appropriate time for each task Simplify and re-prioritize tasks. 12 Oversimplified or bad assumptions lead to incorrect data. Exhaust system design might be incorrect and need to be modified 9 Double-check all assumptions with subject matter expert, test assumption with data collection. Exhaust design would have to be modified to accommodate misconceptions. 13 Equipment doesn’t exist that can survive in the conditions around the engine Design not able to be built in SD2 81 Go through each aspect of the design, keeping in mind survivability conditions. Change materials or geometry. 14Customer needs change Project plan no longer completes customer needs by the end of senior design. 3 Constant communication with RIT Formula team (Taylor Hattori) Change the project plan to accommodate changes and discuss feasibility of changes with customer

Concept Screening ABCDEFGH ANC1ANC2ANC3 Selection CriteriaGlass packModified Glass packMultlipassBaffle muffler Variable length resonator Speaker parallel to exhaust Multiple speakers Exhaust in speaker chamber Ease of manufacture Noise reduction Weight Ease of field repair Costs Effect on back pressure Center of gravity Size Power usage Survivability Sum + 's Sum 0's Sum -'s Net Score Rank Continue? YNNNYNY

Concept Screening (cont’d) ABCDEFGH Glass packModified Glass PackMultipassBaffle MufflerVariable length resonatorSpeaker Parallel to exhaustMultiple SpeakersExhaust in speaker chamber Selection CriteriaRatingWtdRatingWtdRatingWtdRatingWtdRatingWtdRatingWtdRatingWtdRatingWtd Ease of manufacture Noise reduction Weight Ease of field repair Costs Effect on back pressure Center of gravity Size Power usage Survivability Total Score Rank

Proposed Design Objective  Test Bench that can be used as a tool by the formula team to facilitate muffler design and evaluate possible solutions prior to competition  Characteristics to be analyzed may include:  Pressure drop across muffler  Flow rate (volumetric, mass flow rate)  Sound level output  Waveform data Test Bench