杏吧原创

AMERICANS may soon be able to breathe easier. The Environmental Protection
Agency and California state regulators have been cracking down on pollution from
the petrol-burning engines that power hand-held tools such as chainsaws and
garden trimmers鈥攁 significant if underrated source of air pollution. Now
Deere & Company of Moline, Illinois, says it has designed an engine that
could meet EPA targets, cutting emissions by up to 75 per cent and fuel
consumption by up to 30 per cent.

Compact two-stroke engines are widely used because they generate high power
for their size, but they tend to produce disproportionately high pollution. For
example, running a logger鈥檚 chainsaw for an hour releases as many hydrocarbons
as driving a typical passenger car 320 kilometres, says the EPA. A garden
trimmer, with rotating plastic threads that clip grass, releases about a third
as much pollution鈥攁n hour鈥檚 operation is the same as driving a car 110
kilometres. While hand-held leaf blowers and chainsaws are mainly considered
noise nuisances, with seven to eight million sold each year, and tens of
millions in use, the EPA estimates that they generate about 10 per cent of all
air pollution in the US.

Deere鈥檚 innovation adds an injection tube and nozzle to compress and reroute
fuel and hot gas between the combustion chamber and the crankcase. This reduces
the amount of unburnt fuel that escapes, both cutting pollution and enhancing
efficiency.

鈥淚t鈥檚 an interesting technology,鈥� says Bob Larson of the EPA鈥檚 engine
programmes and compliance division in Ann Arbor, Michigan, which is delaying new
rules on hand-held engines while it evaluates the idea.