HAM Humid Air Motor

• The benign impact of water on combustion processes raises the possibility of carrying the water into cylinders in the form of humid combustion air, and this is the concept of Humid Air Motors.
• They work by putting water vapour into the inlet air stream, and are effective at reducing NOx.
• There are issues to be resolved:
  • Quite high volumes of water need to be evaporated to create enough humid air to achieve the reductions sought, and are comparable with the fuel volumes. This requires heat input. The heat input is provided by heat exchange from the hot compressed air after the engine turbocharger. This implies that at low load there may not be sufficient heat in which case the HAM system is not used.
  • Under varying loads (when it is most difficult to achieve optimum combustion) it is also hard to control the humidity adequately.

These issues are soluble, but need development and refinement that will only be available if there is a clear market for the technology.