EGR compressor technology in diesel engines

Principle of the EGR system

In the EGR system, after a cooling and cleaning process, part of the exhaust gas is recirculated to the scavenge air receiver. In this way, part of the oxygen in the scavenge air is replaced by CO2 from the combustion process.

This replacement decreases the O2 content and increases the heat capacity of the scavenge air, thus reducing the temperature peak of the combustion and the formation of NOx. The NOx reduction is almost linear to the ratio of recirculated exhaust gas.

The EGR compressor is a single-stage turbo compressor with oil lubricated bearings, direct driven with an asynchronous motor and a Variable Frequency Drive (VFD). The design features the unique flow optimisation mechanism, utilising Inlet Guide Vanes (IGVs) to optimise efficiency for a given motor rating.

The core compressor features an impeller with backward leaning blades angled according to regulation and milled from a solid, forged piece of duplex stainless steel with an optimal weight/strength ratio.

EGR Compressor illustration

EGR compressor technology for integration into IMO Tier III compliant two-stroke diesel engines.

EGR Compressor - advantages in brief

  • Reliable design and material
  • Fast "Swop" replacement from emergency pool
  • Smallest footprint
  • Design to cost
  • High efficiency for the small pressure ratios
  • Variable speed regulation
  • Adaption possibilities in case of engine derating
EGR Compressor for Diesel engines


  • Impeller made of forged duplex stainless steel (W. No. 1.4462 EN 10088) with a geometry customized for low pressure conditions.
  • Hydrodynamic journal bearings for reliable operation
  • Compressor housing machined from casted stainless steel (AISI316), all components in the air path are made of the same material.
  • Carbon floating ring sealing, external air supply.
  • Pre-set fixed inlet guide vanes adapting the EGR frame capacity to the individual engine size for improved efficiency and flexibility.
  • External lube-oil supply and water cooling supply.
  • Terminal box for connection of power supply (400 V/ 440 V) and instrument sockets.
  • Flange mounted for minimal space requirements.
  • Compact, mechanical design.
EGR Compressor for Diesel engines

Service set-up


Customer ships compressor A for repair, and Howden returns refurbished compressor B from stock, and place refurbished compressor A in stock.


Customer advantage:

No lead time for refurbished pre-set compressor.


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