01-02-2013, 02:18 PM
Exhaust System & Its Advancements
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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.
CO2 — carbon dioxide. The internal combustion engine contributes to the increased concentrations of CO2 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 C6H6 — Benzene and its derivatives and SO2 — 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.
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.