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POLLUTION BREAKTHROUGH
Page 44
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DTI and Shell claim lead for Britain in battle against petrol exhaust emissions
• A new technology for substantially reducing the emission of noxious gases from petrol engines has been announced by the Department of Trade and Industry's National Engineering laboratory at East Kilbride.
The new development, called Vapipe, is a heat pipe vaporizer, the heat pipe being a compact high-conductivity heat exchanger consisting of a metal tube containing a liquid and its vapour. In use, waste heat from the exhaust gases heats the lower part of the tube causing the liquid to boil before condensing in the upper, cooler, part of the heat pipe.
Heat given out by the condensing liquid is thus available to evaporate petrol in the fuel /air mixture before it enters the cylinders. The condensed liquid returns by gravity to the base of the heat pipe, this cycle being continuously repeated and maintaining a steady evaporation of the fuel.
The Vapipe ensures that the petrol is completely vaporized so that the air/fuel mixture fed to each cylinder is identical. Low levels of pollution are obtained by minimizing the creation of unburnt carbon monoxide and oxides of nitrogen in the engine cylinders. This is done by using a weaker mixture of air and petrol than is used in a conventional engine. Without the use of Vapipe a very lean mixture is not a practical proposition
and other methods have to be used to deal with the pollutants created in the 4ngine through conventional combustion.
Road tests on two standard production cars as well as test-bed experiments have indicated that reductions in emissions of carbon monoxide and oxides of nitrogen in the region of 70 per cent and 90 per cent respectively are attained.
The development has been undertaken jointly by the DTI and Shell Research Ltd and it is claimed that Vapipe gives Britain a significant lead "in an area in which the world's motor car industries have invested in large research programmes".