Emission control system's success
Catalytic converters in car exhaust systems only work when they get hot (above 3000°C). This can take up to two minutes from starting the engine, which is the time when the exhaust stream is most full of pollutants. To overcome this problem, Dr Nick Collings has been working with Dr Tom Ma of the Ford Motor Company to develop a technique to shorten warm-up time. By adding extra air to the exhaust gas stream during the initial warm-up period, and combusting residual fuel and carbon monoxide within the catalytic converter, the catalyst can be made to reach its working temperature in about four seconds. A two-section device with an extra segment added to provide space for combustion was used for tests. The engine fuel/air mix is critical for success and ignition is initiated by two spark plugs.
Combustion in the catalyst.
Using this low-cost technique a 60% reduction in emissions can be produced during a standard drive cycle. 'Even though this and other techniques under study are not necessary to enable motor vehicle manufacturers to meet current emission standards, they will be necessary to meet new standards, towards the end of the decade,' comments Nick Collings.
|number 1, summer '93|