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Understanding the basics behind a marine turbocharger

Updated on December 12, 2011

Understanding the basics behind a marine turbocharger


Turbochargers are used basically to improve the efficiency of an engine and it is type of supercharging. The marine turbochargers generally allow large mass of air to be introduced into the engine. The turbocharger is very much required in any marine engine as it helps in allowing large quantity of fuel to be burnt by providing the same amount of air by them.

History

In olden days when engine power was utilized to move a ship, Rotary blowers, reciprocating pumps and pressure charging from the underside of piston were used to improve the efficiency of a marine diesel engine. But all these methods added to the maintenance of the engine and were more troublesome leading its way to a newer technology known as turbo charging system.

Construction

The turbocharger consists of a turbine side, compressor side and a volute casing

  • Turbine side:

The turbine side consists of nozzle ring to drive the exhaust gases towards the turbine side. There is a turbine blade having a fir like arrangement to improve its free expansion and the blades are attached together with the help of binding wires. Roller bearings are provided to hold the shaft in its position. Roller bearing reduces the vibration and the friction drag and they must be renewed every 8000 hours.

  • Compressor side:

The compressor side consists of a compressor to draw air from the atmosphere. The compressor is coupled with the turbine present with the help of a shaft. A labyrinth seal present prevents the exhaust gases from reaching the compressor side.

  • Volute casing:

The volute casing is used to contain both the compressor as well as the turbine side. The casing has its own sump filled with oil for lubricating the bearings. This method of lubrication in turbocharger is known as splash lubrication. Besides this, there is lubrication carried out from main engine lubricating system too. The cooling of the turbochargers is carried out with the procedure of water washing. The water washing or the washing of turbocharger with fresh water generally removes all the fouling and dirt that could have accumulated from the exhaust gases and from the atmospheric air. There is a drain provided to remove the washing water outside.

Working

The exhaust gases from the main engine enter into the turbine side, where the pressure energy from the exhaust gases drives the turbine present in the turbine side after passing through the nozzle ring. Once the turbine is rotated, the compressor also gets rotated as it is coupled with the help of a shaft. The compressor draws air from the atmosphere. The atmospheric air after passing through an air filter gets driven by the compressor side to compress the atmosphere air to a higher pressure and then delivering it to a charge air cooler to maintain its mass and density.

Types of turbochargers

Turbochargers are of two types and they are pulse and constant pressure type turbocharger.

  • Pulse type turbocharger:

In pulse type turbocharger, the exhaust gas directly enters the turbine side and drives the turbine with the exhaust gas energy. The connection from the exhaust side of an engine is directly connected to the turbine side of a turbo charger. The pipe connections from the exhaust gas towards the turbine side are generally small in length and exhaust grouping is provided to prevent the blowback of gases from one cylinder to another.

  • Constant pressure type turbocharger:

In constant pressure type turbocharger, the exhaust gases gets collected in a single exhaust gas reservoir, where the pressure is maintained constant so as to avoid any fluctuation in the exhaust gas energy pressure. The exhaust gas is introduced to the turbine side after maintaining the pressure inside the cylinder.

Materials:

Turbine and compressor blades: Steel or nickel alloy.

Volute casing: cast iron

Bearings: steel or gun metal.

Abnormalities

There are various abnormalities that can occur inside a turbocharger like

  • Surging:

It is a condition when there is mismatch in the running of the turbocharger. This occurs when there is high pressure in the scavenge manifold, this high pressure gas blows back towards the compressor side causing a large noisy sound and results in abnormal running of the compressor. Surging occurs due to uneven exhaust gas energy developed to run turbine of the turbocharger.

  • Fouling:

Fouling occurs when the dirt present in exhaust gases accumulates on the blade of the turbine side. When it accumulates a mismatch or uneven balance of both the turbine and compressor blades occurs resulting in stoppage of the turbocharger. The turbine side must be cleaned regularly with fresh water and drains are opened to remove the dirt present.

marine turbocharger


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    • profile image

      KAMLESH Ghule 2 months ago

      Sir,please explain how the pulse pressure from each unit dampened to maintain constant pressure inside the exhaust manifold in constant pressure turbocharging system..

    • profile image

      rajrajankumar993@gmail.com 2 years ago

      Nice article..easy to undrstnd..

    • profile image

      Capt. Kannan 4 years ago

      Very simply worded and highly informative.. good article useful for many basic learners. kannan

    • profile image

      prayag 5 years ago

      excellent notes.......even a duffer can understand after reading this notes....good job

    • vasanthakumarvc profile image
      Author

      vasanthakumarvc 5 years ago from kERALA,INDIA

      @Yaduvanshi:thanks a lot...ur comments are always encouraging ...it helps me write better one like this..thanking you once again

    • Yaduvanshi profile image

      Yaduvanshi 5 years ago from Bharat Vrse

      Vaanth

      It is a very informative article written in simple words