International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1996-2010, Article ID: IJMET_10_01_195
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=1
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
NOISE REDUCTION OF TWO WHEELER BY
REDESIGNING SPIRAL RESONATOR &
PERFORATED TUBE
Raghuram Pradhan, Sukumar Puhan and M. Sreenivasan
(Professor, Department of Mechanical Engineering, Pace IT&S, Ongole, A.P, India)
ABSTRACT
Background: In this study, the Component of normal exhaust system such as
muffler or silencer shell, perforated tube, spiral resonator design have been carried
out by SOLIDWORKS and a Finite Element Approach have presented for modeling
and analysis of muffler noise developed at different locations as well as temperature
distribution over silencer. The main objective of this study was to simulate and
investigate the performance of a general muffler by simulation and experimental
technique.
Methods: In order to minimize two-wheeler noise, testing were carried out in a
Bajaj pulsar two wheeler by redesigning a spiral resonator andperforator tube which
is capable of attenuating noise level by about 7 dBA (Decibels).
Results: The results obtained from simulation that as the distance increases from
inlet of silencer the sound pressure level decreases gradually.
Conclusions: Obtained results shows a significance decrease of sound pressure
level about 7 dBA from existing silencer to new designed silencer
Keywords: ANSYS-FLUENT, CFD & FEA, Mesh Controls,Noise Reduction,
Perforated Tube, Spiral Resonator and SOLIDWORKS etc..
Cite this Article: Raghuram Pradhan, Sukumar Puhan and M. Sreenivasan, Noise
Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube,
International Journal of Mechanical Engineering and Technology, 10(1), 2019, pp.
1996-2010.
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1. BACKGROUND
I.C. Engines are equipped with an exhaust muffler or silencer, to suppress the acoustic pulse
generated by the combustion process. A high intensity pressure wave generated by
combustion inside the engine cylinder which propagates along the exhaust pipe and
to attenuate this airborne noise of the engine sound reducer called muffler uses to decrease the
velocity of the exhaust gases and either absorbs sound waves or cancel them by interference
with reflected waves coming from the same source. Internal combustion engines are a major
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source of noise pollution after industries. Noise is an environmental pollutant with recognized
impacts on the psychological and physiological health of humans. Noise pollution made by
engines turns into a crucial concern when used in residential areas or areas where noise
creates hazard. Countries like India two-wheelers are becoming increasingly prevalent as a
means of transportation. If noise level of more than 80 dBA (decibels) is harmful for human
being. Mufflers have been developed over the last ninety years based on electro- acoustic
analogies and experimental trial and error. G. W. Stewart (1922) used electro – acoustic
analogies in deriving the basic theory and design of acoustic filters. Later D. D. Diviset
al.(1954) published results of a systematic study on mufflers. Igarashi et al. (1958) calculated
the transmission characteristics of mufflers using equivalent electrical circuits. A.V Sreenath
and L. Munjal (1970) gave expression for the attenuation of mufflers using the transfer matrix
approach . The expression they developed was based on the velocity ration concept.
Later,againL.Mujal(1975) modified this approach to include the convective effects due to
flow . C. I .J. Younget al.(1975) used the finite element method to predict four-pole
parameters and then the transmission loss of complex shaped mufflers for the case of no flow.
A.K.M.Mohumuddin (2005) did experimental study of noise and back pressure for silencer
design characteristics. The main objective of this study was to find the relationship between
the back pressure and the noise level. He concludes that the relationship between the noise
and the back pressure is inversely proportional. S.N.Y.Gerges et al. (2005) paper implies the
basic formulation of the Transfer Matrix Method (TMM) to predict the Transmission Loss of
muffler elements has been summarized. Experimental measurements were carried out for
different muffler configurations and compared to the numerical results obtained from TMM.
It was observed that in general a good agreement is obtained between the experimental and
numerical results. Reza Kashani et al.(2011) approach were based on adding tuned acoustic
damping to the combustion environment. By incorporating in-situ adjustability into acoustic
damping devices, they can change their mechanical attributes, e.g., mass and/or stiffness, and
adapt themselves in a semi-active manner to the varying instability frequency. Takashi
Yasuda(2013) studied on an automobile muffler with the acoustic characteristic of low-pass
filter and Helmholtz resonator. Based on the typical structure, a muffler with an
interconnecting hole on the tail pipe was proposed to improve its acoustic performance.
Acoustic performances of the proposed muffler were studied experimentally and theoretically
in frequency and time domain. Results showed that the specimen muffler had attenuation
performances of low-pass filter and Helmholtz resonator when an interconnecting hole was
designed on the tail pipe.The paper of Vishal Vaidya et al. (2014), emphasizes the role of
resonator on transmission loss in air intake system and its sound pressure level reduction.
Jigar H. Chaudhari (2014) speaks on the various types of mufflers and design of exhaust
system belonging engine has been studied. The object of this study is choosing muffler design
which one reduces a large amount of noise level and back pressure of engine. In designing,
there are various parameters which has to take in to the consideration. These parameters affect
the muffler efficiency. Absorptive muffler design uses only absorption of the sound wave to
reduce the noise level without disturbing the exhaust gas pressure. Ehsan Sabah M et
al.(2013) were conducted an experimental test for noise attenuation in gasoline engine with
different Types of mufflers. Compares between three different types of an exhaust muffler for
noise attenuation of single cylinder four stroke air-cooled gasoline engine. A set of
conclusions achieved about the effect of the mufflers chamber's expansion ratio, chambers
length, and wall thickness. Sound attenuation of 12.5, 15 and 16 dBA is achieved with, multichamber reactive Muffler, concentric-tube resonator muffler and combined reactive and
dissipative muffler. Wei-Hong Tan et al.(2013) conducted an expansion chamber muffler with
the use of a micro-perforated panel (MPP) to improved acoustic performance. The result
showed that the performance of this muffler with an 80mm air cavity depth improved by
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
75%.At the same time they found that, the noise level was reduced by 20 dBA for the
frequency band of 125Hz to 4000Hz of the engine running at 3000±200 rpm. Bin Li1et
al.(2013) experimented a novel and practical acoustic energy harvesting mechanism to harvest
traveling sound at low audible frequency is introduced and studied both experimentally and
numerically. The acoustic energy harvester in this study contains a quarter-wavelength
straight tube resonator with Lead Zirconate Titanate (PZT) piezoelectric cantilever plates
placed inside the tube. M. L. Munjal (2013) development of long strand fibrous materials that
can be used in hot exhaust systems without binders has led to the use of combination mufflers
in exhaust systems. Breakthroughs have been achieved in the prediction and control of
breakout noise from the elliptical and circular muffler shell as well as the end plates of typical
mufflers.Yu, X et al.(2015) A muffler in the exhaust system of an internal combustion engine
reduces its power and increases fuel consumption. Jesus Madrigal et al.(2017)uses transfer
matrix method to calculate the frequency dependence of the transmission of longitudinal
elastic waves for a layered structure where the specific acoustic impedance of the layers with
odd numbering follows a Gaussian distribution, while the inserted even layers have the same
impedance as the propagation medium
2. DIMENSIONS AND DESIGN OF MODELS BY SOLIDWORKS
The SOLIDWORKS ® CAD Software is a Mechanical Design Automation application that
lets designers quickly sketch out ideas, experiment with features and dimensions, and produce
models and detailed drawings.
2.1. Design of spiral Resonator
Diameter of a spiral resonator, d = 70 mm, Diameter of mandrel, dm= 25 mm
Thickness of spiral profile,
g = 3 mm, Lead of Spiral turn, s = 100 mm
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Figure 1 Basic dimensions of Spiral resonator
2.2. Design of Chamber Separator:
Major Diameter of the chamber separator disk = 68 mm, Minor Diameter of the chamber
separator disk
= 30 mm, Thickness of disc = 10 mm, Number of discs = 2
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
Figure 2 Basic dimensions of Chamber Separator.
2.3. Design of Perforated Tube
Internal Diameter = 70 mm, Diameter of the perforated holes = 8 mm
External Diameter = 72 mm, Length of the tube = 400 mm
Figure3 Design of Exhaust Perforated Tube
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Figure 4 Design of Exhaust Perforated Tube
2.4. Design of silencer shell
Diameter = 80 mm, Thickness=4mm, Length of the tube = 400 mm
Figure 5 Design of Silencer
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
Figure 6 Design of Perforated Tube
2.5. Design of Plate
External Diameter = 84 mm, Internal Diameter = 30 mm, Thickness = 4 mm
Figure 7 Design of Plate
3. COMPUTATIONAL FLUID DYNAMICS & FLOW ANALYSIS
Computational Fluid Dynamics also generally called CFD is an important branch of fluid
mechanics and it uses numerical methods and algorithms to analyse and solve fluid flow
problems. It has become popular since the previous methods, experimental and theoretical are
either very expensive, time consuming, or involve too much labour. In CFD, computers are
used to solve the algorithms that define and analyse the fluid flow. Due to the increase in the
computational capabilities over time and better numerical solving methods, most experimental
and theoretical work has been done using CFD. It is not only cost effective but it helps one
analyse and simulate complex geometries, heat transfer, and shock waves in a fluid flow. It
also helps solve partial differential equations (PDE) of any order in a fluid flow. This mainly
helps analyse the internal or external fluid flow. The use of CFD has become increasingly
popular in branches of engineering such as Aerospace to study the interaction of the
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propellers or rotors with aircraft fuselage, Mechanical to obtain temperature distribution of a
mixing manifold, Bio-medical engineering to study the respiratory and circulatory systems.
Figure 8 Processes of CFD and FEA
4. FEA SOFTWARE
There are many FEA software’s available in the market. Some of them mostly used in
Industry are ANSYS, ANSYS WORKBENCH, MSC NASTRAN and ABACUS.Apply Mesh
Controls/Preview Mesh: Meshing is the process in which geometry is spatially discretized
into elements and nodes. This mesh along with material properties is used to mathematically
represent the stiffness and mass distribution of your structure. Model is automatically meshed
at solve time. The default element size is determined based on a number of factors including
the overall model size, the proximity of other topologies, body curvature, and the complexity
of the feature. If necessary, the fineness of the mesh is adjusted up to four times (eight times
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
for an assembly) to achieve a successful mesh. If desired, preview of the mesh is available
before solving. Mesh Controls: When in Simulation, your part or multi body part is
automatically meshed at solve time. The default element size is determined based on the size
of the bounding box, which is the smallest box that the part or assembly will fit in, as well as
the proximity of other topologies, body curvature, and the complexity of the feature. If
necessary, the fineness of the mesh is adjusted up to four times (eight times for an assembly)
to achieve a successful mesh using the assembly's bounding box first, then the part's bounding
box in the second pass. Define Analysis Type: We can choose the analysis type based on the
loading conditions and the response we wish to calculate. For example, if natural frequencies
and mode shapes are to be calculated, would choose a modal analysis. There are several types
of analyses we can perform in Simulation. The primary differences are in the specific types of
loads that we apply and results that review. Establish Analysis Settings:Each analysis type
includes a group of analysis settings that allow defining various solution options customized
to the specific analysis type, such as large deflection for stress analysis.
5. ANALYSIS OF SILENCER
Figure 9 Meshing of silencer
6. PROBLEM SETUP AND SOLUTION
The mesh was checked. The analysis type was changed to density based type and the velocity
formulation was changed to absolute. Time was changed to transient state. Models and
location of receivers: Energy was set on position and viscous model selected is LES model.
Subgris scale model is Smagorinsky-Lily sub model. For enabling LES model in 2-D, a TUI
command is to be used. The command is (rpsetvsr’les2-d? #t). Ffowcs-Williams& Hawking’s
acoustics model is used. The source of sound and receivers are specified.
Direction
Distance from Inlet (mm)
Y
100
Y
200
Y
350
Y
440
Y
18728
The receivers are placed at inlet of the silencer and the distances are mentioned are above.
This distance is selected so that the source becomes a point source and a distribution of
acoustic pressure level does not change with angle of measurement.
Materials: Air (ideal gas) as fluid and stainless steel as solid was selected from the fluent
database by clicking change/create.
Properties given for the used fluid are:
Density : ideal gas density
Specific heat
: 1006 j/kg-K (constant)
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Thermal conductivity
: 0.0242 W/m-K (constant)
Viscosity : 1.7894e-05kg/m-s (constant)
Cell zone conditions
The interior of the nozzle is assigned as fluid. Different boundary conditions were applied
for different zones. The boundary conditions are below
Type of Boundary
Location
Value
Condition
Inlet
Pressure-inlet
1500000pa
Outlet
Pressure-outlet
0.0pa
Inlet
Temperature
623 k
Solution methods: The solution methods were set as follows
1. Formulation =implicit
2. Flux type =Roe-FDS
3. Gradient=least square cell based
4. Flow=second order upwind
5. Transient formulation=second order implicit
Initialization
Hybrid initialization is done. Convergence criteria
The convergence criteria were set to 10-4
Run calculationTime step size = 1s
Number of time steps=500
Number of iterations per time step=500
7. EXPERIMENTAL SET-UP & PROCEDURE (METHODS)
The details of the experimental set up are presented in this chapter the alternations made to
the instrumentation are also described .The experimental setup is fabricated to fulfil the
objective of the present work. The various components of the experimental set up including
modification are presented in this chapter. The silencer existed and new designed silencer is
fixed to the bike in below. The experimental set-up consists of spiral resonator, perforated
tube diameter 700mm, chamber separator, divergent, perforated tube of diameter 30mm, and
cylinder shell. Before starting the engine, the existing silencer is separated from the engine.
The designed silencer is fitted correctly. Then the decibel meter is placed at distance of
1900mm. The engine is allowed to run for 1 minute , so that it can get steady conditions are
attained. The various steps involved in the setting of the experiments are explained below
1. The Experiments were carried out after installation of the silencer.
2. Precautions were taken, before starting the experiment.
3. Always the engine was started with no load condition
4. The readings such as decibels are to be noted at intervals.
5. After completion of test, the load on the engine was completely relieved, then the
engine was stopped. Finally the results were noted.
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
Figure 10 (A) Bike with Existing Silencer
Figure 10 (B) Bike with New Designed Silencer
8. RESULTS
8.1. The Temperature Distribution over Silencer
Figure 11 Temperature Distributions Over Silencer
8.2. The noise developed at different locations in the simulation areas follows
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Figure 12(A) (SPL / St no) Receiver-1 Graph
Figure 12(B) (SPL / St no) Receiver-2 Graph
Figure 12(C)(SPL/St no) Receiver-3 Graph Figure 12(D)(SPL/Stno) Receiver-4 Graph
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Noise Reduction of Two Wheeler by Redesigning Spiral Resonator & Perforated Tube
Figure 12(E)(SPL / St no)Receiver Graph
8.3. The noises developed at outlet in existing silencer areas follows
Figure 13(A)Decibels of existing silencer
Figure 13(B)Decibels of Experimental(New) Silencer
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9. CONCLUSIONS
The results obtained from simulation(refer fig.12) are at 100mm distance from inlet of
silencer, the sound pressure level is 130.946dBA.From 200mm distance from inlet of silencer,
the sound pressure level is 100.643dBA. From 350mm distance from inlet of silencer, the
sound pressure level is 95.12dBA. From 440mm distance from inlet of silencer, the sound
pressure level is 84dBA. From 18728mm distance from inlet of silencer, the sound pressure
level is 73.24dBA.From result of simulation, it has been concluded that the silencer design
has the lowest sound pressure level of 73.24dBA is generatedexperimental testing for new
designed silencer is 1900mm distance from outlet of silencer , the sound pressure level is 69
dBA. From experimental test (refer fig.13), it was concluded that there is decrease of sound
pressure level about 7 dBA from existing silencer to new designed silencer.
10. FUTURE SCOPE
Future experiments can be done with the addition of glass wool to the silencer. Experiments
can be extended with addition of multi tubes with this new design. With above modification
this silencer can be fitted to the sports bike to test the sound level also. The future research of
sound transmission and absorption can be done with bio-based materials, wood plastic
composites and carbon name tubes (CNT) also.
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