Lean mix tames pollution
A SIZABLE reduction in the polluting gases emitted by a four-stroke, four cylinder automobile engine can be achieved. This can be done by applying the lean burn technique, coupled with modifications to the engine like fitting it with a copper coated piston crown, shrouded inlet valve and nickle exhaust valve. This was reported by the students of the Bharath Institute pf Science and Technology, Madras.
in the lean burn technique, the air-fuel ratio is altered to have more air than is chemically correct, by changing the size of the main jet. The leaner mixture operates at a low temperature thereby reducing the formation of oxides of nitrogen, for which high calorific energy is needed. Since the combustion temperature is very low, the dissociation losses are reduced. Combustion with excess of air also considerably reduces the amount of unburnt fuel.