What are A Turbocharger and Its Operation?

A turbocharger is called a turbo. It is a forced induction device that is powered by the flow of exhaust gases. When air is compressed the oxygen molecules are packed closer together.

Today in this article I will discuss the turbocharger and its operation. 


Turbocharger of an engine
Turbocharger of an engine

The power generated by the I.C. engine is directly related to the compression force exerted on the air-fuel mixture. In other words, the greater the compression, the greater the output of the engine. Two approaches can be used to increase engine compression. One is to modify the internal configuration of the engine to increase the basic compression ratio. This has been accomplished in many ways including the use of such things as domed or high-top pistons, altered crankshaft strokes, and changes in the shape and structure of the combustion chamber design. Another, less expensive way to increase mixture compressions without physically changing the shape of the combustion chamber is to simply increase the quantity of the intake charge. By pressurizing the intake mixture before it enters the cylinder, more air and fuel molecules can be packed into the combustion chamber. Keep in mind that any time the amount of the air-fuel mixture that enters the cylinder is increased, there is a substantial increase in power. The two processes of artificially increasing the amount of airflow into the engine are known as turbochargers and supercharging.

Turbocharger operation

Turbochargers are used to increase engine power by compressing the air that goes into the engine’s combustion chambers. Increased power comes from the additional fuel that the denser air accommodates. Today, turbochargers are the most popular method of increasing engine compression. The turbocharger does not require a mechanical connection between the engine and the pressurizing pump to compress the intake gases. Instead, it relies on the rapid expansion of hot exhaust gases exiting the cylinders to spin turbine blades then the name turbocharger), Because exhaust gas is a waste product, the energy developed by the turbine is said to be free since it theoretically does not rob the engine of any of the power it helps to produce.

The turbocharger is located on one side of the engine, usually close to the exhaust manifold. An exhaust pipe runs between the engine exhaust manifold and the turbine housing to carry the exhaust flow to the turbine wheel. Another pipe connects the compressor housing intake to an injector throttle body or a carburetor.

Pressure regulation of turbocharger.
Pressure regulation of turbocharger. 

Inside the turbocharger, an exhaust-driven turbine wheel (hot wheel) is attached via a shaft to an intake compressor wheel (cold wheel). Each wheel is encased in its own spiral-shaped housing that serves to control and direct the flow of exhaust and intake gases. The shaft that joins the two wheels rides on bearings (generally the free-floating type). These bearings are part of bearing lubrication and rotational housing cartridge assembly. One of the surest ways to get more power out of an engine is to increase the amount of air and fuel that it can burn. One way to do this is to add cylinders or make the same cylinders bigger. Sometimes, these changes may not be feasible — a turbo can be a simpler, more compact way to add power, especially for an aftermarket accessory. Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 4.2 to 5.6 N/cm2. Since normal atmospheric pressure is 10 N/cm2 at sea level, you can see that you are getting about 50% more air into the engine. Therefore, you would expect to get 50% more power. It is not so perfect, so you might get a 30 to 40% improvement instead.

One cause of the inefficiency comes from the fact that the power to spin the turbine is not free. Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back pressure. This subtracts a little bit of power from the cylinders that are firing at the same time. The turbocharger also helps at high altitudes, where the air is less dense. Normal engines will experience reduced power at high altitudes because, for each stroke of the piston, the engine will get a smaller mass of air. A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump.

Older cars with carburetors automatically increase the fuel rate to match the increased airflow going into the cylinders. Modern cars with fuel injection will also do this to a point. The fuel injection system relies on oxygen sensors in the exhaust to determine if the air-fuel ratios are correct, so this system is added to a fuel-injected car, the system may not provide enough fuel — either software programmed into the controller will not allow it, or the pump and injectors are not capable of supplying it. In this case, other modifications will have to be made to get the maximum benefit from the turbocharger.

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