Technical Seminar Topic: Exhaust System & Its Advancements Presented By: Mohammed Azeem 1DS08ME404, VIII SEM, `A` SEC, Dayananda Sagar College of Engg. Bangalore

INTRODUCTION Exhaust gas or flue gases is emitted as a result of the combustion of fuels such as petrol, diesel or fuel oil. A car's exhaust system is responsible for transporting the burned exhaust, or combustion gases, from its engine and out through the tail pipe. An exhaust system is usually tubing used to guide reaction exhaust gases away from a controlled combustion inside an engine. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes, depending on the overall system design.

Importance of exhaust system The exhaust system has three major functions: To channel out the waste products of combustion out of the engine. To reduce the noise generated by the engine. To clean up the emissions that are harmful to the environment.

Pollutants from Car Exhaust CO — carbon monoxide. The main source of CO in cities is the internal combustion engine, where it is produced by incomplete combustion. CO 2 — carbon dioxide. The internal combustion engine contributes to the increased concentrations of CO 2 in the atmosphere. NOx — nitrogen oxide forms when fuels are burned at high temperatures. HC — hydrocarbons. Much of the hydrocarbon fuel passes through the process unconsumed and is expelled into the atmosphere along with other exhaust fumes. Other pollutants such as C 6 H 6 — Benzene and its derivatives and SO 2 — sulphur dioxide are also present.

Exhaust system A good exhaust system is designed to reduce the pollution and to increase the efficiency of the engine. The exhaust system may essentially consist of the following components. Components of Exhaust System: Exhaust Manifold Exhaust Pipes Muffler/Catalytic Converter The Tail Pipe

Exhaust Manifold: A vehicle's exhaust manifold is the upper end of the exhaust system. The exhaust manifold is attached directly to the side of the engine and is the first part of the exhaust system to receive the burned exhaust gases from the car's engine. The exhaust manifold, which is extremely hot, further burns any fuel that was inadequately burned by the engine and funnels it down into the main exhaust system.

Exhaust Pipes: The exhaust pipes, which can be metal or aluminium, are responsible for transporting the burned exhaust gases from the engine and the exhaust manifold and funnelling them towards the car's tailpipe.

Muffler/Catalytic Converter As a car's exhaust gases are transported along the exhaust pipes, they must pass through the muffler, which is an enclosed metal container responsible for "muffling" the sounds of the travelling exhaust gases, and the catalytic converter, which is an "after burner" responsible for igniting and burning any leftover exhaust gases not burned by the engine and exhaust manifold. A catalytic converter is a device that uses a catalyst to convert harmful compounds in car exhaust into harmless compounds. MUFFLER

The Tail Pipe: The final destination for a car's exhaust gases is the tailpipe. The tailpipe is the end of the entire exhaust system, and it funnels the burned car exhaust out into the outside air, or atmosphere.

ADVANCEMENTS IN EXHAUST STYSTEM

Technology to counter pollution from exhaust gases and to increase efficiency Exhaust Heat Recirculation: In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by re-circulating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust displaces the amount of combustible matter in the cylinder. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture.

Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates.

Advantages of EGR There are several ways to use a vehicle's exhaust to increase its fuel efficiency and make it run with fewer emissions. For example, the heat of the car's exhaust can be used to warm the engine coolant to keep the engine running warm, even when the motor has been turned off for a significant length of time. The interior of the car can also be warmed using exhaust heat, even in very cold weather. The lower temperatures also help fuel economy. With fuel less prone to detonation. The lower temperatures also help to avoid heat transfer energy losses, meaning that more of the car's energy goes into providing power for its wheels. The amount of nitrous oxide (N2O) emissions can be reduced, and a vehicle's exhaust can actually be used to generate electricity.

Emerging Field in Automotive/Mechanical Engineering

Technology uses auto exhaust heat to create electricity, boost mileage Thermoelectric materials, as the name implies, can produce heat from electricity. These materials were discovered in 1821 by the German physicist Thomas Seebeck. The U.S. Department of Energy has expressed interest in funding the development of a practical thermoelectric system that could be used in cars. Given that most cars already re-circulate exhaust in an EGR loop and that this technology will be even more important in the future.

Principle of generating electricity from exhaust heat Thermoelectric materials generate electricity when there is a temperature difference. The thermoelectric material is contained in chips a few inches square that will be tailored for their specific location within the system. They are optimized to work best at different temperatures, which decrease as gas flows along the system. The material is hot on the side facing the exhaust gases and cool on the other side, and this difference must be maintained to continually generate a current. Thermoelectric materials are Bismuth telluride, Bismuth calcogenides, Skutterudite.

Applications: This electricity could be used to power the car's electrical systems, recharge the batteries, and perhaps most importantly, run the electric motor in hybrid and plug-in battery electric vehicles. This would be a nearly perfect confluence of several technologies, and would have the side effect of helping to reduce nitrous oxide emissions by further cooling the exhaust before it's mixed with fuel. Any type of car could benefit from this thermoelectric boost, but once again, it would be most useful when applied to hybrid vehicles. Thermoelectric technologies also might be used in other applications such as harnessing waste heat to generate electricity in homes and power plants and for a new type of solar cell and solid-state refrigerator.

Future Scope: The development of fuel-efficient and low pollution technologies like exhaust recirculation and thermoelectric power will make the cars of the future - which will have little or no use for fossil fuels. It's important that we develop these technologies now, before fossil fuels run out and pollution does significant damage to the Earth's atmosphere and climate -END-

Bibliography M.L Mathur, R.P Sharma., Internal Combustion Engine, Dhanpat Rai Publications, 2011, New Delhi, ISBN: V Ganeshan., Internal Combustion Engines, Third Edition, Tata McGraw Hill,2010, New Delhi, ISBN: R.B. Gupta, Automobile Engineering, Seventh Edition, Satya Prakashan Publication, New Delhi, ISBN: mmh php urdue.edu/newsroom/research/2010/layout_1_9653_9653.html urdue.edu/newsroom/research/2010/layout_1_9653_9653.html

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