Materials Selection Essay

Turbo charger assembly: Turbo charger is the advanced technology in automotive industry which uses exhaust gasses produced by the engine by sucking it from the blow air back into the engine. The additional air is supplemented with fuel by the ECU (electronic control unit). That causes the engine to produce much more power as it is being supplied with more air and fuel than it possibly could without it. A naturally aspirated engine, or “N/A” engine, has to “suck” air through the intake manifolds, throttle body, ait filter, etc.

With this setup, the most air pressure that can enter the combustion chamber of the engine is a bit less than the current atmospheric pressure. With the turbo, air is being blown into the chamber with positive pressure so that much more air and fuel can enter. A typical turbocharged engine will generate 7 to 10 psi of maximum positive pressure, or “boost”. Simply: ————————————————- Turbo charger is a small radial fan pump driven by the energy of the exhaust gases of an engine.

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A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust heat and pressure to rotational force, which is used to drive the compressor. The turbocharger, or “turbo”, is mounted directly to the exhaust manifold, here turbine impeller is attached to a short shaft where exhaust gases will pass. On the other side of this shaft is a compressor turbine, where through air filter the air is pulled out and blows it into the intake manifold.

So basically, the energy from the expelled exhaust gasses, which would normally be wasted on a N/A engine, is being used to pump air back into the engine. The shaft is supported by a bearing housing that is lubricated and cooled by an oil line from the engine. Since engine exhaust has such high temperatures, the exhaust side of the turbo can reach thousands of degrees F. This is why it is so critical that the engine oil be changed religiously (every 3,000 miles), because old oil can burn and leave deposits in oil lines and housings, called “coke”.

Coking can be virtually eliminated by using synthetic oil and changing it frequently (every 6,000 miles). After 1985, the turbos featured an additional passage for a coolant line, to keep the bearing housing cool. This did little to keep temperatures down while running, but it had a huge effect after the engine was shut off. Without the coolant passage, the oil would drain when the engine was shut off and the turbo bearing housing would reach incredibly high temperatures from the heat transferring out of the exhaust manifold.

This took its toll on the life of the bearings. The presence of the water keeps the housing cool. COMPRESSOR: It allows the fresh air into the engine . It has two openings on the compressor housing i. e. , one inlet and the other out let. The fresh air is sucked from the air filter is its inlet and the air which flows into the engine is the outlet ,the fresh air which enters the engine makes it cooled and at a time the fuel and the fresh air mixes in proper proportion.

With that the performance and the efficiency is developed in the vehicle. SHAFT ASSEMBLY: The shaft in the turbo charger plays a major role which is attached with the turbine wheel. which is the middle of the central housing rotating assembly and at the other end of the shaft the compressor wheel is fitted with the reverse headed screw so that when the shaft is rotating in the clock wise direction the screw may not come out as it is tightened in anti clock wise direction.

TURBINE: The exhaust turbine’s job is to convert the energy in the moving and expanding exhaust gasses into rotating kinetic energy of the shaft and turbines. The compressor turbine’s job is to convert that rotating energy into the movement of the air that enters the engine. This air is compressed and heated. The turbines in a turbocharger are measured by the sizes of each stage of the turbine. A turbine has two stages: the inducer stage and the exducer stage.

The size and shape of each stage determines the shape of the turbine’s fins and ultimately the characteristics of that turbine. For the compressor turbine the inducer part of turbine is at the end of the shaft and can be seen by looking into the intake of the turbo compressor housing . The blades that you see there extend into a larger diameter at the other end of the turbine. This is the exducer stage. The inducer on the compressor turbine is responsible for generating the vacuum at the compressor housing inlet that pulls air into the compressor.

The air then “rides” the fins towards the exducer stage, which is a larger diameter, and gets sling-shot towards the outside of the compressor housing. The housing collects this moving air an expells it through the housing’s outlet. The way that the air leaves the fins causes it to swirl as it leaves the housing. Since the intake manifolds on the early Turbo I engines were so close to the turbo, an anti-swirl fin had to be installed in the turbo outlet duct to stop this air motion from effecting the flow characteristics of the intake manifold.

The exhaust turbine also has an inducer and exducer, but because the exhaust turbine has the opposite function of the compressor turbine, the two are switched. The exhaust gasses are directed towards the outside of turbine through a nozzle. This is the inducer stage because it is the part of the turbine that collects the gasses. As the energy from the gasses is transferred into the turbine, the gasses slow down and exit the turbine through the exducer stage.


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