CFD ANALYSIS ON SILENCER MODIFIED WITH BAFFLE PLATES AND INSULATION OF LCV DIESEL ENGINE

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1 Volume 118 No , ISSN: (printed version); ISSN: (on-line version) url: ijpam.eu CFD ANALYSIS ON SILENCER MODIFIED WITH BAFFLE PLATES AND INSULATION OF LCV DIESEL ENGINE 1 S.Prakash, 2 M.Prabhahar, 3 M.Saravana Kumar, 4 Mubasheer 5 Muhamed Shahabaz.M 6 Muhammed Lijas.B 1,3 Research Scholar, 2 Associate Professors 4, 5,6UG Students, Aarupadai Veedu Institute of Technology, Vinayaka Mission University Abstract A silencer is device used for reducing the amount of noise emitted by the exhaust of an internal combustion engine. When exhaust gases are removed outside the combustion chamber at the end of the combustion process, the gases move into the exhaust manifold at high pressure and at a considerably high speed, with controlling their flow and speed, When an engine runs, high pressure exhaust gas is released with help of baffle plates and insulation in the rear most exhaust system inside the silencer to reduce pressure, The idea being to allow expanding exhaust gases ( hot and noisy) to be slowed to a more uniform rate before leaving exhaust system. The paper report simulates the field by numerical method with turbulence Flow and analyses the effect which the internal flow field has on the performance of the silencer with 5 baffle plates and 15 baffle plates with compressed full insulation. With this method the pressure distribution in the silencer is simulated and the pressure loss is predicted for the structure modification. The experiment results verify that the assembly performance of the silencer modified. Keywords: silencer, Baffle plates, insulation, CFD 1. Introduction A silencer is device used for reducing the amount of noise emitted by the exhaust of an internal combustion engine. Internal combustion engines are typically equipped with an exhaust silencer to suppress the acoustic pulse generated by the combustion process. When exhaust gases are removed outside the combustion chamber at the end of the combustion process, the gases move into the exhaust manifold at high pressure and at a considerably high speed. When an engine runs, high pressure exhaust gas is released. This causes a pressure wave in the air causing and explosion very fast to form a steady noise. To reduce the noise, the engine exhaust is connecting to exhaust pipe to the silencer it is also called as muffler in automobile vehicles. 1001

2 Fig 1.1 silencer The objective of the project is to analyze the flow characteristics of exhaust gases in the existing and modified design of the silencer. The work is to focus on to optimize the design in order to have minimum back pressure and increased life of silencer and at the same time to reduce the pollution. The Computational Fluid Dynamics analysis would be carried out by using CFD tool CFX. A comprehensive study would be carried out with the parameters such as pressure and temperature distribution of turbulence and fluid force varying load conditions. 1.1 Catalytic Converter Catalysts are compounds that can trigger a chemical reaction without being affected themselves. For example, enzymes are natural catalysts that control many important chemical reactions in living organisms. Catalysts are also used in automobiles to reduce emissions of certain harmful compounds. In order to reduce air pollution, modern automobiles are equipped with a device called a catalytic converter that reduces emissions of three harmful compounds found in car exhaust: i. Carbon monoxide (a poisonous gas) ii. Nitrogen oxides (a cause of smog and acid rain) iii. Hydrocarbons (a cause of smog) These are converted into less harmful compounds before leaving the car s exhaust system. This is accomplished using a catalyst, which gives the device its name.the catalyst used in a catalytic converter is a combination of platinum (Pt), palladium (Pd), and rhodium (Rh). These metals coat a ceramic honeycomb (or ceramic beads) contained within a metal casing that is attached to the exhaust pipe. The catalytic converter s honeycomb structure provides the maximum surface area on which reactions can take place while using the least amount of catalyst. A reduction and oxidation reaction occurs inside the device. Carbon monoxide (CO) in converted to carbon dioxide (CO2). Nitrogen oxides (NOx) are broken down into nitrogen gas (N2) and oxygen gas (O2). And hydrocarbons (HC) are converted into carbon dioxide (CO2) and water (H2O). First of all, the catalytic converter uses a reduction catalyst composed of platinum and rhodium to reduce the nitrous oxides. As the nitrous oxide molecules (NO and NO2) pass through the device, the catalyst removes the nitrogen atom, allowing the free oxygen to form oxygen gas (O2). The nitrogen atom that is attached to the catalyst reacts with other attached nitrogen atoms to form nitrogen gas (N2). Reduction Reaction 1: 2NO => N2 + O2 Reduction Reaction 2: 2NO2 => N2 + 2O2 In the second stage of the reaction, an oxidative catalyst of platinum and palladium decreases emissions of carbon monoxide (CO) and unburned hydrocarbons (HC). Oxidation Reaction 1: 2CO + O2 => 2CO2 Oxidation Reaction 2: H4C2 + 3O2 => 2CO2 + 2H2O In gasoline engines, catalytic converters are reliable and efficient at reducing pollution. They convert an estimated 90% of the hydrocarbons, carbon monoxide, and nitrogen oxides produced into less harmful compounds. However, catalytic converters are less efficient when used with diesel engines, which run colder than gasoline engines. 1002

3 Catalytic converters work best at higher temperatures. Diesel engines also produce particles such as soot. 1.2 Baffle Plates These baffle plates are found in the rear most exhaust system known as the silencer. (Not the catalyst) it is part of the internal structure of the silencer (exhaust rear box) looking like a piece of metal with uniform holes perforating it. The idea being to allow expanding exhaust gases ( hot and noisy) to be slowed to a more uniform rate before leaving exhaust system. It acts also like a 'barrier' in that the gas cannot so quickly pass through as the metal acts a sieve. The silencer box will also have tubes again perforated along inner length of the box where gas must pass from engine outlet pipe then across from the perforated pipe and past baffle plates into another perforated pipe before exiting to outside air. It baffles air to create the pressurized conditions required within your systems design for proper and distribution and flow rate throughout your system. Many baffles are adjustable and some are fixed. There are various reasons for that too. Air noise is also something that baffles is used to help alleviate noisy type situations that may exist or have a potential to do so. Hope this helps: Jimi wane in your gas tank they dampen the movement of the fuel when you accelerate or decelerate as an example function of baffles is to prevent swirling in agitation. The baffle helps to hinder the motion of waves and splashing which also helps to keep air from getting within the hydraulic system, improve the effect of mixing They reduce fuel movement from sloshing around during turning, on larger tanks they can help the handling a great deal Baffle plates are used in oil pans to keep the oil near the pickup tube during hard: turning/braking/acceleration. If there wasn't any the oil would all go to 1 side turning a hard turn and the engine would be starved of oil and cause engine damage. Fig.1 Silencer filled with insulation 2. Setup and Solution 2.1 Preparation Initially made the external wall design, and added 5 baffle plates in first stage then 15 baffle plates added for reducing pressure, its selected left side as velocity inlet and right side as pressure outlet with the domain extends of x-coordinate: min (m) = e-01, max (m) = e+01, y-coordinate: min (m) = e+00, max (m) = e+00 Volume statistics: minimum volume (m3): e

4 maximum volume (m3): e-03, total volume (m3): e+01, Face area statistics: minimum face area (m2): e-02, maximum face area (m2): e-02. Material mixture-template switched on in CFD tool for mixing of diesel to analyzing the velocity inlet and pressure outlet, then thermal conductivity has added with viscosity and Mass Diffusivity to find the Mass-Weighted Average at pressure coefficient of fluid is Fig 2 silencer design with 5 Baffle Plates Fig 3 silencer design with 15 Baffle Plates 2.3 Materials Properties UNIT VALUE Density Kg/m Specific heat j/kg-k 2090 Thermal Conductivity w/m-k Velocity Kg/m-s Problem Solution After the construction of silencer model in Autodesk inventor it is analyzed in ANSYS FLUENT 15. The FLUENT analysis is carried out by considering the boundary conditions of Velocity inlet and Pressure outlet. 3. Results and Discussion The mean flow performance of the silencer considered in the flow analysis has been assessed. The results of the simulated silencer models obtained with the use of CFD modeling are very encouraging. From Figure it has been observed that for a velocity inlet boundary condition in model 1, the exhaust from the engine enters the silencer at a velocity of 8m/s for both model of 5 baffle and 15 baffle plates. 1004

5 Fig 4 Velocity inlet set in CFD tool For Initialize the solution, 0.1 m2/s2 for Turbulent Kinetic Energy and 100 m2/s3 for Turbulent Dissipation Rate. Fig. 5 Residuals Graphs For Continuity x and y velocity energy k epsilon Fig. 6 Convergence History of Velocity Magnitude on Pressure Outlet Velocity Inlet Boundary Condition for 15 baffle plates 1005

6 Change the removable baffle from wall to interior. Select interior from the Type dropdown list. Retain the default name and change the model with 5 baffle plates. Fig. 7 Contours of Velocity Magnitude with 5 Baffels The area under this curve must be unity. Exit age distribution E (t) = C (t)/ R 0 C (t)dt Here C (t) is the concentration of tracer at the outlet as a function of time. Rt 0 C (t)dt represents the fraction of particles which spend a time less than t inside the reactor. Fig.8 Static Pressure Fig.9 Velocity Magnitude Vs. curve length For Pressure Outlet 1006

7 Fig.10 E-curve for Reactor with 15 Baffles The fraction of particle which spend a time more than t is Using the same method, calculate the minimum time for which 50% and 25% of particles spend inside the reactor. Fig. 11 E-curve for Reactor with 5 Baffles Once you obtain the E-curve, calculate the minimum time for which 75%, 50%, and 25%of the particles spend inside the reactor. Using the same method explained earlier, you can get the values as shown the table The following table shows the residence time comparison which is helpful for selecting the suitable design of the reactors based on the requirement. Particle % Inside Reactor 4. Conclusion Time (s) for Reactor with 15 Baffles Time (s) for Reactor with 5 Baffles In this work two different arrangement baffle plate with insulation of a silencer have been designed for the engine output of an LCV diesel engine and the flow has been simulated using ANSYS FLUENT. The experimental perforated tube have good contour, so this design is optimize design from the all On comparing the results and performances of the two different arrangement baffle plates, we observe that though both the arrangement have same similar design parameters, the both arrangement was more effective in reducing the exhaust pressure because of its internal baffle arrangement and insulation. The Maximum velocity in has reduced 50% to pressure 1007

8 outlet for arrangement of 5 and 15 baffle plates with insulation Hence we conclude that baffle plate with insulation is more efficient in reducing the exhaust pressure. 5. Reference 1. Pradyumna Saripalli, K. Sankaranarayana, CFD Analysis on Flow Through a Resistance Muffler of LCV Diesel Engine International Journal of Science, Technology and Society, 2015; 3(4): Published online June 6, Dattatray Dilip Giripunje, Prof. Dr. Vilas B. Shinde, Swapnil S. Kulkarni, THERMAL ANALYSIS FOR MOTOR-BIKE EXHAUST SILENCER FOR ENSURING REDUCTION IN HOT SPOTS THROUGH DESIGN ENHANCEMENT International Journal of Advanced Engineering Research and Studies E-ISSN , July-Sept., 2013/ Keval I. Patel, Ravi Engineer, Parikshit K. Patel, Cfd Analysis of Perforated Tube of Aqua Silencer INDIAN JOURNAL OF RESEARCH, Volume : 4 Issue : 5 May 201, ISSN AugustoDellaTorre, MULTI-SCALE CFD MODELLING OF INTAKE AND EXHAUST SYSTEMS FOR INTERNAL COMBUSTION ENGINES 2013 XXV Cycle STEN 5. PL.S. Muthaiah, Dr.M. Senthil kumar, Dr. S. Sendilvelan, CFD Analysis of Catalytic Converter to Reduce Particulate Matter and Achieve Limited Back Pressure in Diesel Engine Global Journal of Researches in Engineering, Vol.10 Issue 5 (Ver1.0) October R Sundara Raman, G. Sankaranarayanan, N. Manoharan and S. Sendilvelan, Experimental Investigation on Emission Characteristics of a Marine Diesel Engine with Catalytic Convertor for Compliance with Marpol Regulations Asian Review of Mechanical Engineering ISSN: Vol. 4 No. 2, 2015, pp The Research Publication, 7. S. Sendilvelan and K. Bhaskar, - Effect of Multiple Injection Strategies to Reduce Oxides of Nitrogen and Control of Pollutant Emissions of an Automobile, Vol. 9 No October - December PL.S. Muthaiah, Dr.M. Senthil kumar, Dr. S. Sendilvelan, CFD Analysis of Catalytic Converter to Reduce Particulate Matter and Achieve Limited Back Pressure in Diesel Engine, Global Journal of Researches in Engineering, Vol.10 Issue 5 (Ver1.0) October Keval I. Patel, Ravi Engineer, Parikshit K. Patel, Cfd Analysis of Perforated Tube of Aqua Silencer, Indian Journal of Research, Volume: 4 Issue: 5 May

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