Automotive component supplier Delphi is proposing hydrogen enrichment as a solution to future emissions legislation for internal combustion engines.
It is developing a microreformer to generate hydrogen by partial oxidation of fuel. This would be used with a normal petrol engine to reduce emissions of hydrocarbons and nitrogen oxides from cold starts, and nitrogen oxides when the vehicle is cruising.
The system would not require any significant changes to the design of internal combustion engines, according to Jean Botti, chief technologist of Delphi’s innovation centre for dynamics and propulsion.
Botti said that hydrogen enrichment would allow the precious metal content of exhaust catalysts to be reduced by almost half. It would avoid a dramatic increase in the size of catalysts which would otherwise be needed under forthcoming emissions rules and which would be difficult to fit into small cars.
The microreformer technology has been demonstrated in a component measuring two litres in volume. Botti is confident this can be halved by the time production starts by the middle of the decade.
In the reformation reaction, petrol plus a limited amount of air is partly oxidised to hydrogen and carbon monoxide, both combustible gases, before entering the engine.
Though this reaction would also need a catalyst to promote it, experts say cheaper materials such as nickel could be used.
Apart from reducing emissions the enriched fuel allows the catalyst to reach ‘light-off’, the temperature at which it starts operating effectively, sooner. Delphi says the system will be particularly useful for larger- engined, high emission vehicles.
The reformer is a development of the one used in the fuel cell auxiliary power unit, being developed by Delphi with BMW and Renault. This is intended to provide electricity for car ancillary systems such as air conditioning, heating and navigation systems, without running the engine or draining the battery.
The auxiliary power unit employs a solid oxide fuel cell as opposed to the proton exchange membrane type being developed for traction applications.
As proton exchange fuel cells needs much purer hydrogen than solid oxide, the reformer technology would not, in its current state of development, be suitable for motive power applications.