Dutch on the road to a pollution-free engine

By Staff
article image

‘Reprinted from the January 10, 1970, issue of Business Week
by special permission. Copyrighted (c) 1970 by McGraw-Hill,

We thank Mr. Paul B. Finney, Managing Editor for kind permission
to use this article in our Gas Engine Magazine. Our appreciation
also to Mr. Denis McCormack, 404 West Timonium Road, Timonium,
Baltimore Co., Maryland 21093, for his efforts in acquiring this
article and permission to use same.

One of these days, a Dutch engineer named R. J. Meijer expects
to step out of his lab in Eindhoven, the Netherlands, and tool off
in a revolutionary new car powered by a silent, vibration-less,
pollution-free engine that will run on anything from alcohol to
salad oil.

That day, he admits, is still down the pike. But Meijer’s
employer, the giant Dutch electronics company Philips’ Lamp
Works, has made a 30-year wager that the Stirling cycle engine
Meijer has been puttering with for 22 years will eventually do to
the diesel what the gasoline engine did to the horse and buggy. By
1975, backers predict, the Stirling will be operating in buses,
boats, ships, submarines, trucks, and even locomotives. A
nuclear-fueled Stirling for space travel is not too far beyond
that, nor is Meijer’s hot rod. In fact, he already has a cabin
cruiser outfitted with a Stirling.

Less noise.

The idea Philips is betting on is a thermodynamic phenomenon
discovered over 140 years ago by a Scottish clergyman named Robert
Stirling. His own ‘air engine’ proved too bulky and
inefficient compared with steam and internal combustion engines,
and did not gain widespread use. Like the internal combustion
engine, the Stirling relies on the principle that gas expands when
heated, and this expansion can do work. However, instead of drawing
in gas with air and exploding it inside a cylinder to drive a
piston, the Stirling engine is completely closed. Gas–helium or
hydrogen in Philips’ versions-is heated in a chamber
surrounding the cylinder, and never mixes with the atmosphere. The
heated gas drives a piston in a leak-proof cycle.

The result is an engine free of rattling valves and noisy
explosions. Fuel is not consumed inside the cylinder, so many of
the complications of reducing noxious pollutants are

Rube Goldbergian.

It took two major innovations by Meijer himself, however, as
well as the evolution of better heat-conducting and heat-resistant
materials not available in Stirling’s day, before an efficient
Stirling engine could be developed, even in prototype. The problem
was to keep gas from escaping from the cylinder. Working almost
sin-glehandedly, Meijer developed the so-called rhombic drive, a
Rube Goldberg configuration of gears, counterweights, rods, and
shafts, which limits the motion of the Stirling’s piston rod to
a simple up-and-down motion. This cut down the area where gas could
escape most easily.

Then, a few years ago, Meijer succeeded in making the cylinder
leak-proof when he came up with the roll-sock seal, a polyurethane
diaphragm that fits snugly around the piston rod and operates like
the rolling of a stocking up and down. The result is a much more
durable engine.

Diesel rival.

‘Our goal is an engine that will run 10,000 hours without
maintenance,’ says Meijer. One 10-hp prototype has already
logged more than a month and a half of continuous operation, and is
still going strong. That is equal to an engine driving a car
steadily at 100 mph for 120,000 mi. This engine, like two others
Philips has made, has only one cylinder. But the first of 11
four-cylinder, 200 hp prototypes, suitable for use in buses, should
be operating this month. These will be the same size, weight, and
have about the same power-to-weight ratio as comparable diesels,
which are most vulnerable to the challenge which the Stirling

‘The gas turbine will probably replace the gasoline
engine,’ says Stig Carlqvist, president of United Stirling Co.,
a Philips’ licensee in Malmo, Sweden, ‘and the Stirling
will probably replace the diesel. At least that’s how it looks
to us now.’

Philips’ technicians now are also putting together the first
versions of four-cylinder engines suitable for passenger cars. In
these ‘double-acting’ engines, gas is interchanged from one
cylinder to the next, instead of having a separate closed system
for each cylinder. This eliminates several working parts and
permits a lighter, more compact design. The prototype, which may be
in operation within two months, will be capable of generating 60 hp
and will weigh about 250 lb., roughly the same as an internal
combustion engine of similar horsepower.


Carlqvist, whose United Stirling was formed by three Swedish
manufacturing companies, thinks the initial market for the Stirling
will be for stationary units in the range of 10 to 200 hp. These
would be ideal in places where it is vital that noise, vibration,
and pollution be suppressed-in mines, for example. United Stirling,
formed in July, 1968, expects to sink $8-million into research over
the next four years.

Carlqvist, like Philips, has his eye on the bus market. ‘For
that,’ he says, ‘you have to have customers. You have to
start someplace.’

After buses, ships are likely candidates for Stirlings, says
Otto Syassen, head of another outfit licensed by Philips and
composed of West Germany’s two competing diesel makers,
Maschinenfabrik Augsburg-N?rnberg and Motorenwerke Mannheim.
Syassen’s group is tinkering with five 30-hp Stirling engines
of its own design and expects to have them in operation any day
now. These will be single-cylinder units, but Syassen is sure he
can turn out a mul-ticylinder version in a year or so.

GM’s doubts.

In the U. S., General Motors Corp. has been toying with the
Stirling engine since 1958, when it signed an agreement with
Philips to cooperate on research. While GM gives the Stirling high
marks for efficiency, output, quiet operation and clean exhaust,
the company does not think it will ever replace the internal
combustion engine in cars. ‘The Stirling is still bulky, heavy,
complex, and expensive,’ a spokesman told a recent
Congressional subcommittee. GM feels that the potential for the
engine lies in boats, engine-generator sets, submarines, torpedoes,
and other quiet, lightweight power-plant uses.

The Europeans are far more optimistic. Carlqvist says it is
technically possible to put a Stirling engine in a bus in as little
as two years, but it would probably cost up to twice as much as the
diesel, largely because of higher costs for special heat-resistant
materials. Philips uses a specialty steel in the engines cooling
tubes that is about five times as expensive as ordinary steel.

Cool view.

Meijer thinks concern over noise and air pollution will muffle
the cost difference. He is also confident about shrinking the
radiator, which is about two and a half times the size of a
standard radiator. Meijer explains that the Stirling requires a
bigger radiator because the engine is more efficient, and less heat
is lost in the exhaust than in the internal combustion engine.

This need for a jumbo radiator is a major drawback in fitting
the Stirling into trucks, say some critics. But Meijer insists
radiator space is not a problem: ‘There’s no reason to
believe designers can’t design around a bigger cooling

Perhaps the biggest problems still facing the Stirling, however,
are starting it and getting it to respond faster. The engine must
be preheated to about 1,300 F to start up, which takes at least 15
seconds even with a quick-firing kit. And since power is adjusted
by varying gas pressure or temperature, not simply fuel, critics
say response is naturally slower. ‘Philips is talking in tenths
of a second,’ says a competitor. ‘The ordinary automobile
engine responds in hundredths.’

Antipollution role.

Despite these drawbacks, the Stirling is getting a stronger push
than ever. It is as quiet as an electric motor, and the only
contaminants it releases come from the external heating chamber,
where it is far easier to reduce noxious elements. In the internal
combustion engine, firing takes place with the cylinder, and
tampering with the fuel-air mixture to trim pollutants can impair

Meijer is confident that the Stirling engine right now can beat
the most stringent U.S. pollution standards. A single-cylinder
engine tested recently released only 0.1 milligram of carbon
monoxide per second per hp, compared with 2 mg for the gas turbine
and 0.2 for the diesel. Under greater load, the diesel spews out 5
mg per second, while the Stirling puts out only 0.3.

The Stirling also releases only traces of nitrogen oxides, the
peskiest of pollutants. And Meijer is now patenting a technique
which will cut these emissions to .025 mg per second per hp, well
below existing or even proposed standards.

Indeed, since the engine can operate on alcohol, crude oil,
butane, natural gas, gasoline, and salad oil, pollution can be
reduced merely by the selection of fuel. It is even possible to use
heat sources that do not involve combustion.

Besides a nuclear-heated Stirling that Philips foresees,
technicians have produced engines that get their heat from electric
cables immersed in a heat reservoir of lithium fluoride. A heat
pipe filled with liquid sodium transfers the heat from the storage
tank to the engine.


It is ironic that Philips is now trying to use electricity to
drive the Stirling: The company first developed the engine to
generate electricity. Some 30 years ago, it stumbled on the
Stirling while hunting for a cheaper, multifuel generating source
to power radios where electricity was not available. That pursuit
ended in the early 1950s, when the transistor made it more
practical to use batteries.

How the Stirling engine kicks over

Hot gas is what makes the Stirling engine work. A source of
constant heat warms the gas, such as hydrogen or helium, that is
kept in a closed cylinder. The hot gas expands and forces the
displacer down. The displacer squeezes cooler gas above the piston,
which then forces the piston down. The displacer then moves back to
its original position and the piston follows it, driving cool gas
through the heat regenerator and the heater, and the cycle starts

The rhombic drive in the crankcase translates the piston’s
motion into a circular movement, so wheels can be turned.

The Stirling does not emit the pollutants turned out by the
standard engine. But it needs a huge radiator to keep cool.

The project staff was pared down to Meijer and one assistant,
and little hope was held out for a practical Stirling–until Meijer
came up with his rhombic drive and the roll-sock seal. These
boosted the engine’s chances to make the Stirling a real threat
to the internal combustion engine in the years ahead.

Philips’ Lamp of Holland expects its Stirling engine to
rival diesels by 1975

Europeans see Stirlings for autos as well as buses, but GM is

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