Lean mix tames pollution

A SIZABLE reduction in the polluting gasesemitted by a four-stroke, four cylinderautomobile engine can be achieved.This can be done by applying the leanburn technique, coupled with modifications to the engine like fitting it with acopper coated piston crown, shroudedinlet valve and nickle exhaust valve.This was reported by the students ofthe Bharath Institute pf Science and Technology, Madras.

in the lean burn technique, the air-fuel ratio is altered to have more airthan is chemically correct, by changingthe size of the main jet. The leaner mixture operates at a low temperaturethereby reducing the formation ofoxides of nitrogen, for which highcalorific energy is needed. Since thecombustion temperature is very low,the dissociation losses are reduced.Combustion with excess of air also considerably reduces the amount ofunburnt fuel.