LNG-fueled Main Engines

Decarbonization Alternative Fuels
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What are the main differences between low pressure and high-pressure LNG-fueled two stroke Main Engines?

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There are two predominant technologies for LNG-fuelled two-stroke Main Engines : high pressure gas injection and low pressure gas admission engines.

High Pressure Gas Injection (300 bar) based on Diesel Cycle:

  • High Fuel Efficiency (10% higher than Otto Cycle)
  • High Compression ratio
  • Negligible methane slip (important for future environmental regulations)
  • No risk of knocking
  • Not sensitive to methane number
  • Higher capital cost
  • High power density (requires smaller LNG fuel tanks)
  • No compliance with IMO Tier III in gas mode. Requires Tier III reduction technology (EGR, SCR)
  • Lead engine type: MAN ME-GI

Low Pressure Gas Admission (7-13 bar) based on Otto Cycle:

  • Lower fuel efficiency
  • Lower compression ratio
  • Higher Methane Slip
  • High risk of knocking
  • Low Power density (requires bigger LNG fuel tanks)
  • Sensitive to methane number
  • Tier III compliant in gas mode
  • Lower capital cost
  • Lead engine type: Wartsila XDF or MAN ME-GA
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Interesting feedback George.
Is there any difference in terms of fuel valves design and operation (perhaps the opening pressure is set at a different range?)
Additionally, are there any other differences in the fuel equipment ?

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