[modeleng] steam car (OT)
- From: "alanjstepney" <alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Tue, 28 Dec 2004 03:51:10 -0000
It is full size, unelss someone happens to want to make a model of it...
Steam-powered vehicles are not usually deemed as being parked at the cutting
edge of transport technology.
Nor do they seem to be the type to race across desert landscapes in a bid to
smash land speed records in the 21st Century.
But British design engineer Glynne Bowsher and his team have almost finished
building a super-fast vehicle reminiscent of the Batmobile.
And this car puts a new technological breath of life into what is regarded
as a traditional means of power.
He knows engine and vehicle design like old friends, having worked on
Richard Noble's record-breaking Thrust 2 jet car and having designed
ThrustSSC, the first vehicle to break the sound barrier on land.
His team, the British Steam Car Challenge (BSCC), is hoping that its
Inspiration vehicle will live up to its name and not only break a
long-standing steam-car speed record, but also inspire thinking about
alternative fuels for the future.
In and out
The search for a suitable alternative fuel source to hydrocarbons which can
cleanly power our vehicles has touched on various different options.
Fuels which do not "rot" the environment usually bring to mind images of
gently humming electric cars, clean hydrogen, natural gas, or hithane - a
concoction of hydrogen and methane.
The most promising, believes Mr Bowsher, is either nuclear or hydrogen fuel.
The public is reluctant to explore nuclear; but researchers and engineers
across the world are exploring how best to generate and, more importantly,
store hydrogen fuel, one of the main barriers to its widespread use.
Nine European cities are taking part in a pilot scheme to use hydrogen
fuelled buses on certain routes, for instance.
But until a viable mass-scale way of storing and distributing hydrogen
effectively is developed, it remains limited in use.
External combustion engines - like steam ones - hold several advantages over
internal ones.
They have the potential to produce fewer harmful nitrogen oxides (NOx) than
conventional cars which use internal combustion engines.
Although steam engines still need to burn hydrocarbon-based fuels like
petrol and diesel, which in turn release carbon dioxide, external combustion
engines can control the release and the production of CO2 more efficiently.
And because such engines can work well at lower peak temperatures and
pressures, the creation of NOx compounds can be almost negligible.
Inspiration is a far cry from the steam cars made famous by the Stanley
brothers, however.
The 1906 record, set by a Stanley Steamer at what is now Daytona Beach, is
the longest-standing officially recognised land speed record for a steam
car.
It was set at a time when the battle for supremacy between petrol-powered
internal combustion engines and steam-powered external combustion engines
was in full sprint.
Although Stanley Steamers had enjoyed a boom in the early 1900s, they were
quickly being overtaken by internal combustion engines. The steam car,
driven by Fred Marriott, reached 127.7mph (205.5 km/h), beating four
petrol-powered vehicles to pick up the Dewar Trophy rewarding the fastest
vehicles on land.
Even before steam became speedy, a steam-powered engine designed by Nicolas
Joseph Cugnot drove the first self-propelled vehicle in 1769.
But it had to rest every 15 minutes to generate enough steam power to send
it on its way again.
To Mr Bowsher, it is steam's historical legacy that has always attracted
him.
"I grew up with steam locomotives in my own town, so steam was a part of my
life. When I was young we didn't have a car - my father never owned one," he
explains.
"We went on the railway or the bus. It was quite important to me; I always
had a love of aviation and steam so those two things in terms of transport
are still with me."
Own design
Designing a steam engine fit for the demands of a 21st Century land-speed
attempt has proved somewhat of a challenge, however.
"We basically had to come up with our own design, which is innovative in
some ways," says Mr Bowsher. So innovative, in fact, that the team is
exploring patenting the design.
Inspiration's engine works in quite a simple way, he explains.
Water is passed through a steam generator where it is heated by burning
propane gas into superheated steam at 400C and at 40-bar pressure (4 million
Pa).
Inspiration is designed to break the long-standing land-speed record for
steam cars
That steam is then fed into four nozzles on a two-stage turbine arrangement.
"With a turbine, you either use the pressure energy or velocity energy. In
this case, we turn the pressure energy into high velocity.
"Then the moving gas stream strikes the turbine wheels and starts them
rotating - a bit like a small-scale power station," explains Mr Bowsher.
"Once we have a turbine that goes round, rotational power, that along with
gear ratios can be used to drive the wheels and once we have the wheels
rotating we can make it go forward fast."
It sounds simple enough, but there were big challenges technologically to
generate enough power in such a small vehicular space - 300 brake horsepower
to be precise.
That is 225kW of power operating at 12,000rpm. Formula 1 engines typically
operate at more than 17,000rpm, while aircraft turbine engines turn at
85,000rpm and above.
"One difficulty was getting a turbine and transmission system in such a
small space.
"But the worst problem was providing a steam generator to provide steam the
turbine needed in such a small space." It is a method of steam production
that seems not to have been used previously, according to Mr Bowsher.
He does not imagine that steam cars will be the complete road ahead for cars
on our streets.
"Gas turbines have been used in the past," he says. "But the problem of
turbines is that to be efficient, they have to run at a predetermined speed.
"The very nature of road cars is that their speed changes all the time, so
this design would be no good for road vehicles."
But he can imagine the engine design being used in diesel-based commercial
vehicles which belch out a large proportion of pollution, like buses and
lorries.
"Burning propane is environmentally more friendly than burning diesel. If
the technology could be adapted, then it might just be a possibility - it is
something we are investigating," he says.
Engine spec.
Two stage turbine on single spool
Output: 300bhp at 12,000rpm (turbine speed) (225kw)
Output shaft gear ratio: 4:1 or 4.45:1 to twin output shafts
Differential: Epicyclic type with viscous couplings
alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
www.alanstepney.info
Model Engineering, Steam Engine, and Railway technical pages.
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