快猫短视频

IT鈥橲 NOT much to look at. Just a shiny metal cylinder about the size of a
small fire extinguisher. Its inventors hope it鈥檚 the beginning of a green
revolution in automobile technology. If their dream comes true, it could
eventually change the face of road transport. If not, it will be remembered only
as a doomed attempt to resurrect a kind of engine that most people wrote off
almost 50 years ago.

Seven years of effort and millions of Deutschmarks have gone into developing
this environmentally friendly 21st-century steam engine. And to show the world
that it鈥檚 serious about steam power, German engineering company Enginion has
already installed a larger version of its engine beneath the bonnet of a Skoda
Fabia, and run it on a test stand for 300 hours.

Enginion鈥檚 dream is to build a new generation of car engines that can power
everything from family runabouts to high-performance roadsters. These engines
will be as fuel efficient and reliable as traditional designs but will release
next to no pollution. And eventually, Enginion hopes, its steam machine could
oust competing clean engine technologies, and power everything from lawnmowers
to locomotives.

Can they possibly be serious? Steam cars were run off the road a hundred
years ago, and ever since, steam technology has been seen as outdated,
inefficient, polluting and cumbersome compared with the all-conquering internal
combustion engine. 鈥淧eople associate steam engines with smoke and noise and
slow-moving machinery,鈥� admits Oliver Mehler, marketing vice-president at
Enginion. Steam lost out to petrol and, later, diesel engines, primarily because
steam engines were a pain to operate. They needed constant maintenance, and you
couldn鈥檛 simply leap in and drive away. You had to get up a head of steam first.
But these problems are a thing of the past, says Mehler: 鈥淥ur technology is
clean, quiet and dynamic.鈥�

The idea for a thoroughly modern, non-polluting steam engine was born at IAV,
a large engine research and development company, based in Berlin. With 60
million euros of European Union grants and funds from the German government, the
company spent 6 years developing the technology, and at its height, the project
employed over 100 people. Build an engine that meets the strictest pollution
targets and the company hoped it would be able to clean up in the massive US car
market.

Then in December 2000, six of the team鈥檚 key members, including Mehler,
decided to buy the technology from IAV and set up their own company to develop
it. That company is Enginion, and it revealed details of its prototype engine in
March this year.

The essential job of any steam engine is to take the energy stored in
high-pressure steam and convert it into motion鈥攗sually by driving a piston
in a cylinder. Enginion鈥檚 rotary engine is no different (see Anatomy of a steam
engine). So why should this steam engine succeed where others have failed?

It鈥檚 all down to the clever use of modern materials to get round the problems
that dog traditional designs. One of the biggest headaches with conventional
steam engines is that lubricating oil can leak into the steam system, where it
reacts with the hot steam and breaks down. This bring two serious problems: the
oil has to be constantly replenished, and regular cleaning of the steam system
is needed to prevent the oil contaminating the engine鈥檚 water supply.
Contamination in the water reduces the heat capacity of the steam, limiting the
engine鈥檚 efficiency.

Enginion gets round these problems at a stroke, by making its engine鈥檚
pistons and most of the other components lubricant-free. 鈥淎n engine without
lubrication is quite an achievement,鈥� says Neil Richardson of the Institute of
Cryogenics and Energy Research at the University of Southampton. It took four
years of research to find the right carbon-based ceramic material for the piston
and piston rings, and to develop the composite that is used to line the steel
cylinders.

Operating together, they have ultra-low friction and are incredibly
hard-wearing鈥攂etter than anything else in existence, according to Mehler.
The main bearings will still need lubrication, but without the conventional oil
circulation system the engine can be made lighter and cheaper, and eliminates
the need to dispose of dirty oil during regular maintenance.

While the engine is running in, particles of carbon transfer from the piston
to the liner. After that, there is apparently almost no interaction at all: the
coefficient of friction is 0.008, Mehler claims, which is less than a metal
skate on ice. 鈥淲e鈥檝e received enquiries from [researchers] at Los Alamos
National Labs,鈥� he says. But secrecy reigns. Until patents are filed, the
company is refusing to reveal details of the materials.

The other major advance over traditional steam engines is the porous ceramic
combustor that generates the heat to make steam. Based on a design by Franz
Durst and his colleagues at the Institute of Fluid Mechanics at the University
of Erlangen-Nuremberg, Germany, it鈥檚 a ceramic block made from fibres of
aluminium oxide or silicon carbide that are fused together to form a structure
riddled with pores. This is the perfect environment in which to burn fuel
cleanly, since each pore acts like a tiny combustion chamber.

When fuel burns in the much larger cylinders of a petrol internal combustion
engine, for example, there are inevitable hot and cold spots caused by poor
mixing. At the hot spots, more nitrogen oxide pollutants form, while in the
cooler zones the fuel does not burn properly, so poisonous carbon monoxide and
unburnt fuel are pumped out through the exhaust. Durst鈥檚 ceramic burner creates
an even, stable, flameless burn totally unlike the turbulent inferno inside an
internal combustion engine. Fuel burns evenly at an optimum temperature of
around 1200 掳C. In tests, researchers at Enginion found that while their
steam engine releases plenty of carbon dioxide it doesn鈥檛 release any unburnt
hydrocarbon fuels, and nitrogen oxide and carbon monoxide levels were measured
at less than 10 parts per million, about one hundredth that emitted by most
internal combustion engines
(see Diagram). With further refinement, they believe
they should be able to halve these emissions.

Engineers are suitably impressed by Enginion鈥檚 data. 鈥淚 believe auto
manufacturers would want to take a look,鈥� says Richard Stobart, professor of
automotive engineering at the University of Sussex. His colleague at Sussex,
mechanical engineer Fred Bayley, agrees: 鈥淚t looks feasible to me, and I鈥檓
prepared to believe their claims for low emissions.鈥�

Improved fuel economy is another benefit. Enginion says its engine runs more
efficiently than a petrol internal combustion engine鈥攁nd can almost match
a diesel engine. And once the fuel is ignited, the combustor heats up quickly to
start generating steam. It can reach operating power in about 20
seconds鈥攁lmost as quick a start-up as some diesels.

A steam-powered car would also have some mechanical advantages. Unlike an
internal combustion engine, it can deliver power from a standstill, so it won鈥檛
need a gearbox or clutch. Power and speed are controlled directly by altering
the amount of steam injected into the cylinders. The explosive expansion in the
cylinder provides up to five times the torque of a regular internal combustion
engine, Enginion claims. That鈥檚 always been one of steam鈥檚 big pluses: at the
beginning of the last century, drivers of Stanley steam cars discovered that if
they accelerated hard, they could lift the front wheels of their vehicles clear
off the ground.

But even with the high-performance combustor and the high-tech material in
place there are still likely to be problems, such as how to keep the cylinders
steam-tight. 鈥淲ith a rotary engine, sealing will be a problem,鈥� says Richardson.
The high temperature superheater is likely to create difficulties too, as steam
at 900 掳C is pretty corrosive stuff. 鈥淚t will need expensive development and
sophisticated materials. The cost could kill the engine,鈥� says Bayley. Mark
Kessell, an engineer at Britain鈥檚 Motor Industry Research Association in
Nuneaton, Warwickshire, reserves judgement. It鈥檚 interesting, he says, 鈥渂ut
unless you can sit down and quantify the thermodynamics, you can鈥檛 tell if it
will work.鈥�

With so many hurdles to leap, it鈥檚 hardly surprising that Enginion is
proceeding cautiously and not rushing to produce a steam-powered car straight
away. Instead, it is concentrating for now on a small auxiliary power unit (APU)
capable of generating 6 kilowatts of electricity鈥攁bout a tenth of the
power needed to propel a small car. Enginion plans to have the 32-kilogram APU
in mass production and generating income within three years. A large car engine
would take far longer to develop鈥攑ossibly up to eight years.

A unit like this could provide air conditioning, heating and electricity for
trucks when their engines aren鈥檛 running. Currently trucks use their polluting
main engines when parked overnight to generate electricity to power vital
systems such as refrigeration units and heaters. 鈥淎 clean and efficient
auxiliary power unit would solve those problems,鈥� says Stobart.

The unit鈥檚 6 kilowatts would also be enough to power mopeds, motorcycles and
small commercial vehicles. All over the developing world, there are millions of
small carts that use noisy and dirty two-stroke engines. 鈥淥ur technology will do
the job but be clean and quiet,鈥� says Mehler.

The company is also planning a larger APU that could be installed in homes to
provide heat and electricity on demand. This unit could be 90 per cent cheaper
to run than the equivalent fuel cell or gas turbine, Mehler claims. Ultimately,
the design could be scaled up to an engine generating 300 kilowatts鈥攅nough
to power a small railway locomotive or railcar.

In the past 9 months, Enginion has shown its steam APU to more than a dozen
car manufacturers and power generator companies. And in October the company
received its first order, a 鈥渉uge鈥� contract, according to Mehler, 鈥渇rom one of
the world鈥檚 foremost car manufacturers鈥�. But here, too, secrecy reigns. Mehler
says that mass production of the APU will begin in 2004, but won鈥檛 reveal other
details of the contract.

So does the company鈥檚 focus on auxiliary power units mean that a full-blown
steam powered-car is no longer on the cards? Far from it, says Mehler. He points
to plans to build a larger version capable of powering a hybrid car that could
use batteries to power an electric motor in towns, when clean running is
required, with the APU to top them up. 鈥淚t makes sense to use our APUs in hybrid
vehicles,鈥� he says.

And main engines will surely follow. 鈥淯nquestionably the technology would be
ideal for vehicle propulsion. After all, it was the original intent of our
research,鈥� says Michael Hoetger, Enginion鈥檚 president. To prove the point, last
year the company built a three-cylinder, two-stroke reciprocating version of
their steam engine and installed it under the bonnet of a Skoda Fabia. Mounted
on a test stand, the engine chuffed away for 300 hours without a hitch.

But that鈥檚 still way short of the thousands of hours between servicing that
will be needed for a practical car engine. And however good the steam engine
looks on paper, convincing the car industry to launch a new generation of steam
cars is likely to be an uphill struggle. 鈥淭he automotive industry is very
conservative,鈥� says Roger Waller, chief engineer of the Swiss company DLM, which
makes steam locomotives. 鈥淭here鈥檚 been so much money put into the development of
the internal combustion engine that they don鈥檛 want to change.鈥�

Besides, in the race to develop a low-emission engine, there are other strong
contenders. For example, industry experts say we will soon be driving cars
powered by fuel cells running on nothing but hydrogen and air
(快猫短视频, 25 November 2000, p 34).
These cells release the lowest levels
of pollutants of all propulsion systems. However, the need for a completely new
fuel infrastructure, and problems with storing large quantities of hydrogen are
likely to delay implementation. Experts predict that by 2020, about a quarter of
new cars will use fuel cells powered by hydrogen. Even if these predictions for
fuel cell usage are pessimistic, that still leaves a large proportion of the car
engine market for us, says Mehler.

So steam needs to get a toehold while it can. If Enginion can begin
production of steam-driven cars by the end of the next decade, before fuel cells
start to take off, its steam car could still be a contender in the market for
low-emission vehicles. It has one big factor in its favour: any fuel will do.
Steam cars can run on petrol, diesel, methane, hydrogen and even biofuels such
as ethanol. Maybe we won鈥檛 have to end out love affair with the car, even when
the world鈥檚 precious petroleum reserves eventually run out.

When starting from cold, vaporised fuel and air are pumped into the
ring-shaped, porous ceramic combustor and ignited with a spark.

The hot exhaust gases then flow across a pair of heat exchangers. The larger of the
two, the primary heat exchanger, boils water and heats the steam to about 500 掳C.
This steam is pumped through the smaller, secondary heat exchanger or
superheater, where hot gases straight from the combustor boost
it to around 900 掳C. An electronic injection system releases the steam
through a valve into the piston chamber, where it turns a curved piston that
spins the drive shaft. (According to Enginion鈥檚 marketing literature the piston
resembles that in a Wankel rotary engine, although the company claims their
technology is very different.)

As the steam cools, it leaves the chamber and gives up its remaining heat to
the incoming feed water, condenses, and flows back to the water reservoir. This
means the system shouldn鈥檛 need topping up.