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If you turn the combustion chamber of a car engine into a microwave oven
you’ll have a virtually pollution-free vehicle, says the Research Centre in
Karlsruhe (WO 99/37911). The microwaves warm the petrol and air mixture before
ignition and then generate a spark to ignite the mixture. The frequency of the
microwaves is adjusted to match the resonant frequency of the chamber, which
concentrates the energy. The technique is said to burn both rich and lean
mixtures completely.