Catalytic Igniter to Support Combustion of Ethanol-Water/Air Mixtures in Internal Combustion Engines

Lean ethanol-water/air mixtures have potential for reducing NO_x and CO emissions in internal combustion engines. Igniting such mixtures is not possible with conventional ignition sources. An improved catalytic ignition source is being developed to aid in the combustion of aqueous ethanol. The operating principle is homogeneous charge compression ignition in a catalytic pre-chamber, followed by torch ignition of the main chamber. In this system, ignition timing can be adjusted by changing the length of the catalytic core element, the length of the pre-chamber, the diameter of the pre-chamber, and the electrical power supplied to the catalytic core element.

A multi-zone energy balance model has been developed to understand ignition timing of ethanol-water mixtures. Model predictions agree with pressure versus crank angle data obtained from a 15 kW Yanmar diesel engine converted for catalytic operation on ethanol-water fuel. Comparing the converted Yanmar to the stock engine shows an increase in torque and power, with improvements in CO and NO_x emissions. Hydrocarbon emissions increased significantly, but are largely due to piston geometry not well suited for homogeneous charge combustion. Future engine modifications have the potential to lower emissions to current emission standards, without requiring external emission control devices.