MAN Diesel & Turbo’s Two-Stage Turbocharging passes the ‘Acid Test’


MAN Diesel & Turbo’s innovative two-stage turbocharging concept “The ECO CHARGE” – passes the first test and we can expect the two-staged turbocharging system to hit the market soon.

The two-stage turbocharging system is currently being tested on MAN 12V35/44 gas engine on a test bed at its Augsburg, Germany workshop.  The “ECO CHARGE” system has been designed in such a way that it works both on diesel fuel and gas engines.  MAN Diesel & Turbo reported that they have combined individual MAN TCR20 and MAN TCX17 turbocharging units – as a single, two-stage turbocharging system.  This combination has been fitted on to the MAN 12V35/44 gas engine for testing and approval purposes.  The test is the first real opportunity to prove the thermodynamic calculations on an engine which is key to a successful field test.

It is to be noted that

MAN TCR20 – is employed at the low pressure stage, and

MAN TCX17 – is for the high pressure stage.

The above turbocharging combination proves that the diesel engine would be more efficient, complying to emission restrictions, and higher power to weight ratio with lower specific fuel oil consumption.

The Conventional 4-stroke engines would reach a charge air pressure of about 2 to 4 bar depending upon the operating power range.  With the two-stage turbocharging, it is expected that the charge air pressures would reach a range from 5 to >10 bar with improved turbocharging efficiencies.

The image below shows a basic 2-stage turbocharging system working principle.


It is well established and witnessed that an air compressor uses intercoolers to take the heat of compression from the compressed air.  By removing the heat of compression, the temperature of air entering the next stage reduces thereby the air becomes more denser.  This improves the compressor efficiency and the output pressure.

The above principle is being employed in case of the two-stage turbochargers.  The compressed air from the first stage passes through the intercooler where the heat of compression is removed by the cooling water.  The compressed air temperature drops to near ambient in the after part of the intercooler thereby increasing the charge air density.  Once again the compressed cooled charge air enters the second stage of the turbocharging system, where the pressure ratios are being increased much beyond the conventional turbocharging pressure ranges.

The increase in turbocharging efficiencies, in comparison to single-stage turbochargers, is mainly related to the intercooler – positioned between the low-pressure-stage and high-pressure-stage turbochargers – that significantly reduces the energy required to compress the intake air to high pressure.  The resulting, higher efficiencies have an instantaneous impact on the engine by advantageously increasing the air pressure over the cylinder during the scavenging process.


By means of two-stage turbocharging the charge air pressure can be increased substantially.

The result is optionally higher power density and, in conjunction with Miller engine cycle, reduced exhaust emissions and lower fuel consumption.

With the TCX series MAN Diesel & Turbo has developed a turbocharger especially suited for two-stage turbocharging of two- and four-stroke engines.

Your direct benefits:

  • Higher power density
  • Lower fuel consumption
  • Reduced exhaust emissions
  • Compact design with integrated intermediate- and charge-air coolers

Image and Video Credits: MAN DIESEL-TURBO.


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