Turbochargers
E-mail

 

 

Very few technical innovations in the automobile industry have become as popular as the Turbochargers. They have had a huge impact and what they do to an automobile is so significant that the term Turbocharged has almost become a valid english metaphor used in every context possible! Let’s attempt to understand a thing or two about them, and how they work...

A Turbocharger was patented in 1905 by Swiss engineer Alfred Büchi.

A Turbocharger is a mechanical device whose basic job is to enhance the power output of an internal combustion engine. It achieves this boost by increasing the intensity of the air that enters the cylinders for combustion by compressing it. The Turbocharger is driven by the exhaust gases of the engine.

Construction and working:
A Turbocharger consists of two turbine wheels encased in separate housings driven by a common shaft. One of the turbines is driven by the exhaust gases which in turn helps better air suction thru the second turbine and compressing the charge. However before the air charge makes its way to the engine, the air is cooled with the help of an intercooler which is strategically placed between the turbocharger and the intake
manifold. Controlling of the air charge is done by using wastegate, which is mounted on the exhaust side of the turbocharger. Wastegate by passes the excessive exhaust gas pressure directly to the outlet. (refer fig 1.1)


1.1


Implementation:
Although Turbochargers are used in aircrafts, marines, they have proved to be a boon to the automotive industry for it's a quite useful to increase the power output of any engine with minimal costs (designing and production of turbochargers) and would occupy very small space as compared to a normal engine for the similar power output.

Earlier, Turbochargers were mostly used to enhance diesel engines because of the exhaust gas from a diesel engine having relatively higher pressure compared to that of a gasoline engine.

However, now, even petrol engines are being equipped with a Turbocharger. One such example is the TSI (Turbo Stratified Injection) engine introduced by the German VW group. This engine sports a better performance per cubic capacity of the engine thanks to the Turbocharger and as it allows for a smaller engine cubic capacity, you get better fuel economy figures.

It is a myth that Superchargers and Turbochargers are same; they are not. We will get to Superchargers in one of our following articles.

Turbo Lag:
A major factor that one has to counter with a Turbocharger is Turbo lag. Turbo lag can be defined in simple terms as the time lapsed between the throttle pressing and for the effect of the Turbocharger to be felt in the the acceleration of the car. In naturally aspirated engines one experiences a hesitation while rapid acceleration in response to the throttle.
A higher Turbo lag can be felt when a disproportionately large Turbocharger is fixed to an engine and an attempt is made to generate disproportionately higher power output.


Types of Turbochargers:
Hybrid Turbocharger: A Hybrid Turbocharger is an electric Turbocharger consisting of an ultra high speed turbine-generator and an ultra high speed electric air compressor. The turbine and compressor are high-speed aero machines, as in a conventional turbocharger.

Variable Geometry Turbocharger (VGT):
A Variable Geometry Turbocharger helps in providing a variable air charge to the intake manifold depending on the engine rpm. A VGT has its significance in the variable vanes. Its basic function is to control the flow of exhaust gas to the turbine wheel. These vanes are controlled electronically in modern age cars. Having the VGT doesn’t require wastegates (refer fig 1.2)


1.2

A turbine with variable vanes (VGT)