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Breakthrough could see vulnerable Australia fight fire with fire

English.news.cn   2014-05-22 08:33:13

SYDNEY, May 22 (Xinhua)-- As back-burning to prevent summer fires cloaks Sydney in a blanket of haze, researchers here have a powerful new weapon that they hope will literally blow any the fury of Australia's seasonal bushfires.

Graham Doig, of the School of Mechanical and Manufacturing Engineering, has traveled the world and come home with the evidence that explosives -- rather than water -- could be used to extinguish an out-of-control bushfire.

Building on the long-standing technique used to put out oil well fires, the University of New South Wales team says the process is not dissimilar to blowing out a candle: it relies on a blast of air to knock a flame off its fuel source.

With Sydney, Thursday morning, wrapped in a shroud of smoke, residents in many parts of NSW will have woken to an eerie and familiar haze as fire authorities here step up hazard-reduction burns.

Above-average rainfall in March and April for most of NSW and Victoria has constricted the autumn burning period.

Robert Rogers of the NSW Rural Fire Service said teams will be out burning from August right through until March in the busiest fire season since 2000-01.

Australia has suffered under drier conditions in the last 12 months with some record breaking heat fuelling concerns here of another tinder box -- or catastrophic -- fire conditions.

According to the climate commission, Australia has broken all the wrong records this year. Over 120 extreme weather related records were eclipsed in the 2012/2013 summer.

Australia experienced the hottest January on record, the hottest summer and the hottest day ever recorded in Australia.

An alternate approach to damaging fires saw Doig travel to the Energetic Materials Research Testing Center -- a high-explosives and bomb test site in a remote part of New Mexico -- earlier in the year to scale up tests he originally conducted at UNSW's heat transfer and aerodynamics laboratory.

The U.S. visit was made possible by funding from UNSW and an American Australian Association Fellowship.

The New Mexico tests used a four-meter steel blast tube, which contained a cardboard cylinder wrapped in detonation cord, to produce a concentrated shockwave and rush of air. This was directed at a meter-high flame fuelled by a propane burner.

"The sudden change in pressure across the shockwave, and then the impulse of the airflow behind it pushed the flame straight off the fuel source," Doig explains. "As soon as the flame doesn't have access to fuel anymore, it stops burning."

Doig hopes the concept can now be scaled up to fight out-of- control forest and bushfires burning in remote parts of the world.

He wants to test if it is possible to blow flames out of treetops and knock any loose, dry material in the trees that is fuelling the fire to the forest floor, where it will burn more slowly, if at all.

"Fire is very fast moving if it gets up into the tree tops. If the fire is still smouldering or burning on the forest floor, it's moving at a fraction of the speed, giving emergency services extra time to come in with water bombing or ground operations," Doig said.

"We're thinking of this as being a potential way to stop a fast uncontrolled fire in its tracks and give you a lot more time to get things under control or evacuate people that are downwind of the blaze."

Doig speculates that the explosive charge could be carried into place by a helicopter before being unleashed on the fire.

"Of course as soon as the blast happens you'd want to detach the explosives from the helicopter," he said. "But helicopter transport would allow you to position the blast somewhere where people couldn't otherwise get in easily."

The team has been researching the impact of shockwave interaction with flames for four years, building on PhD work on the aerodynamics of low-flying aircraft and the reflection of shockwaves from the ground.

Thousands of volunteers remain deep in the bush around the state, with more than 40 areas to be targeted in NSW alone.

According to the Bureau of Meteorology, not only was last September the warmest September on record, but the warmest September by the greatest margin of any recorded monthly temperature increase people have experienced in Australia.

Climate scientists are insisting that climate change is seeing Australia experience hotter days, more heat-waves and more of the negative impacts on human health, agriculture, industry and many plants and animals that come with a warming climate in a country already beset by ferocious heat.

Bushfires are an emotive issue here. Australia has a long history of fire and already faces the regular risk of serious and extreme fire danger conditions.

Over the past decade, large and uncontrollable fires destroyed 500 houses in Canberra in 2003, and bushfires in Victoria in 2009 took 173 lives and destroyed over 2,000 houses.

Editor: xuxin
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