Reactive muffler
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This document provides an overview of a research paper on reactive mufflers. It begins with an introduction to noise reduction in automobiles and motivation for using reactive mufflers. It then describes the geometric design of reactive mufflers and considerations for their design such as acoustics, aerodynamics, mechanics, cost, and materials. A case study is presented on designing a reactive muffler for a low commercial vehicle diesel engine to achieve a targeted transmission loss. Virtual simulation and prototype testing are discussed. The effects of corrosion on reactive mufflers are also covered. The paper concludes that this design methodology can help understand the importance of each design step from concept to validation.
![Case study on LCV Reactive muffler
Targeted data:
Bore Diameter (D) 80 mm
Stroke Length (L) 98 mm
No. of cylinder (n) 3
Engine Power (P) 65 hp
Maximum RPM (N) 3500 rpm
Targeted transmission
loss (dB)
30 dB
Engine Input data:
Target Frequencies
Cylinder Firing Rate:
CFR = Engine max speed/120 for 4 stroke engine
CFR = 3500/120 = 29.17 Hz
Engine Firing Rate:
EFR= No. of cylinder * CFR
EFR= 3*29.17 = 87.50 Hz
Engine- Benchmarking Data
Muffler Volume calculation
Volume of muffler (Vm) = Vf ×
[
𝜋
4
×D2x 𝐿] ×
𝑁
2
Volume factor is taken as 16
So, Volume of muffler (Vm) = 11.83 Lit](https://image.slidesharecdn.com/nvh-reactivemuffler-180412210527/85/Reactive-muffler-10-320.jpg)
Reactive muffler
- 1. A Research Paper “Overview of Reactive Muffler” Submitted To: Dr. Colin Novak Submitted By: Devarsh Patel (104861000) Bandhav Fadia (104817821) AUTO APPS FOR NOISE/ VIBRATION/ HARSHNESS (06-85-525-01)
- 2. CONTENTS Introduction Reactive muffler Geometric Design The Reactive muffler design considerations Helmholtz Resonator Case study on LCV Diesel engine vehicle Corrosion Effect on reactive muffler Conclusion References
- 3. INTRODUCTION Automobile Noise Sound & Vibration Noise Reductiuon Noise is characterized as undesirable sound. Engine exhaust noise is one of the major concern of every automobile company Motivation behind a Reactive muffler is to decrease vehicle exhaust noise
- 4. Reactive muffler Geometric Design Figure 1: Geometric design of reactive muffler The geometrical shape of reactive muffler consists of numerous chambers, flow diffusers, tuned resonated cylinders, and discharge tube connected with the outlet connection pipe
- 5. The Reactive muffler design considerations 1. Acoustical consideration: Insertion loss Transmission loss • It is defined as the difference between the acoustic power radiated without and with a muffler fitted. • It is defined as the difference (in decibels) between the sound power incidents at the entry to the muffler to that transmitted by the muffler.
- 6. The Reactive muffler design considerations 2. Aero dynamic consideration with backpressure: • Aerodynamic consideration specifies the flow of exhaust gases from muffler to create less pressure in muffler. • The extra static pressure generated by the muffler on the vehicle engine through restriction in flow of exhaust fumes to achieve higher noise reduction may result in higher backpressure to the engine. Figure 2: Aerodynamic flow diagram of reactive muffler
- 7. The Reactive muffler design considerations 3. Mechanical consideration: 4. Economical consideration: • Mechanical considerations are taken for material selection, which decide muffler’s durability • The material properties of exhaust required for the hot section include good strength for high temperature, thermal fatigue properties, oxidation and salt corrosive resistance. • Majorly two types of materials used in manufacturing the reactive muffler which include Stainless steel and the Aluminum • Muffler must have to be less expensive with consideration of design cost, material cost and fabrication cost • The performance of muffler may matter by its cost
- 8. Helmholtz Resonator • It is used in car exhausts to alter the sound of the exhaust note and for differences in power delivery by adding chambers to the exhaust muffler • Exhaust resonators are also used to reduce potentially loud and obnoxious engine noise • The waves reflected by the resonator helps to cancel out certain frequencies of sound in the exhaust. Figure 3: Helmholtz resonator in muffler chamber
- 9. Case study on LCV Reactive muffler Shital S., Saisankaranarayana K, Kalyankumar S. and Prof. Thombare performed Experiment on low commercial vehicle diesel engine vehicle. Designed Reactive muffler by deciding a target of required transmission loss.
- 10. Case study on LCV Reactive muffler Targeted data: Bore Diameter (D) 80 mm Stroke Length (L) 98 mm No. of cylinder (n) 3 Engine Power (P) 65 hp Maximum RPM (N) 3500 rpm Targeted transmission loss (dB) 30 dB Engine Input data: Target Frequencies Cylinder Firing Rate: CFR = Engine max speed/120 for 4 stroke engine CFR = 3500/120 = 29.17 Hz Engine Firing Rate: EFR= No. of cylinder * CFR EFR= 3*29.17 = 87.50 Hz Engine- Benchmarking Data Muffler Volume calculation Volume of muffler (Vm) = Vf × [ 𝜋 4 ×D2x 𝐿] × 𝑁 2 Volume factor is taken as 16 So, Volume of muffler (Vm) = 11.83 Lit
- 11. Case study on LCV Reactive muffler Virtual Simulation CFD analysis: There will have steady pressure drop which is related to flow and geometry of air passages by supplying steady air flow through mufflers. Pressure drop in muffler is important tool for the design and development of mufflers. All three concept of muffler are tested for flow analysis using CFD simulation tool (a): Concept 0A (b): Concept 0B (c): Concept 0C Figure CFD Model of Concept 0A, 0B, 0C
- 12. Case study on LCV Reactive muffler Virtual analysis: The mean flow performance of the three mufflers considered in the acoustic analysis has been assessed. Frequency range for this case study is taken in 10-2000 Hz. Reflection on inlet and outlet end cover is neglected From the virtual analysis of transmission loss it can see that concept 0A is having better transmission loss compared to other concept 0B and 0C in initial frequency range 20 Hz to 600 Hz. As well as in mid frequency range of 1000 Hz to 1400 Hz.
- 13. Case study on LCV Reactive muffler Prototype manufacturing and experimental testing: Some important factors have to take care such as there should not be any gas leakage The experimental determination of backpressure on engine and transmission loss. The prototypes of all concepts that are made at the above step are tested for the transmission loss to verify the target value. All three concept muffler tested on engine for evaluate back pressure measurement.
- 14. Case study on LCV Reactive muffler As per the results received from FFT analyser transmission loss v/s frequency schematic diagram is plot for all three different mechanical exhaust concept models. Transmission loss is calculated between 10 dB to 60 dB to frequency range. From the experimental frequency and transmission loss plot, it has been observe that concept 0A is having higher transmission loss in same initial frequency range 20 to 600 Hz. By comparing virtual analysis and prototype experimental results, best concept muffler is identified, also for back pressure CFD results are compared with engine back pressure results. Based on this compression concept 0A selected
- 15. Corrosion effect on Reactive muffler The main drawback of reactive muffler is corrosion, which is happen due to exhaust gas condensate In general practice it is seen that the corrosion problem is mostly observed at a time of short distance driving, when the temperature does not go high and wet corrosion start due to condensation mainly in the muffler at the cold end becomes the major factor of failure Corrosion failures may cause perforation of components causing exhaust leaks in internal components that may result in noise issues due to change in muffler acoustics and can also result in pollution causing damage to environment. Types of corrosion in muffler: • Condensate Pitting corrosion • Exterior Salt pitting • Crevice corrosion • Oxidation • Galvanic corrosion
- 16. Corrosion effect on Reactive muffler
- 17. Conclusion • This paper emphasizes the importance of the reactive muffler through various consideration for vehicle noise including their characteristics starting from the design to proto manufacturing and validation of exhaust muffler. • The measuring cycle which described in this paper though one case study could provide the noise and pressure determinations, within the particular design models made with artificial softwares within specific limitation. • Practical approach from the concept design to prototype model and validation of exhaust muffler. This design methodology will help to understand the importance of each step of design from concept level to validation level. Numbers of attempt, product development time and cost can save by this practical approach.
- 18. References 1. Kuppm P. K. R., Shahab F., & Amiya R. M. (2018). A new sound quality metric for the design of engine exhaust mufflers. Journal of Automobile Engineering, 232(2), 254-263. 2. Krishnal B., Prof. R.S., & Prof. P.K.S. (2015). Vibration analysis of an Automotive silencer for reduced incidence of failure. International Journal of Engineering and Technical Research, 2321-0869, 79-84. 3. Potente, D. (2005). General Design Principles for an Automotive Muffler. Australian Acoustical Society, 9-11, 153-157. 4. Nitinkumar A., Kalpana G., Shrikant N., & Santosh S. (2015). Vibration and Noise in Reactive Muffler: A Study. Advances in Mechanical Engineering Techniques, 12-13,1-5 5. Shital S., Saisankaranarayana K., Kalyankumar S.H., Prof. D.G.T. (2010). A Practical Approach towards Muffler Design, Development and Prototype Validation. SAE International, 032-0021, 1-16. 6. Krunal C.C., Prof. R.Y.P., Prof. N.R.S., & Prof. S.J.C. (2016). Investigation of Geometrical Parameter on Performance of Muffler Using CFD Analysis. International Research Journal of Engineering and Technology, 2395-0056, 1332-1338. 7. M. H.N., Z. A.K., A. S., & K. S. (2016). A predictive model for life assessment of automotive exhaust mufflers subject to internal corrosion failure due to exhaust gas condensation. Engineering failure Analysis, 63, 43-60.
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