World's first gas-turbine car achieved 90 m.p.h. on test track.
We Drive Turbo Cars?
Can the aircraft wonder engine earn a place on the highway? Both U.S. and British engineers think so.
It had no clutch pedal, distributor, valves, radiator, or transmission. It had none of those conventional pulsing exhaust noises. But it had performance.
|Air intakes handle ten times amount of air required by piston engine of comparable power. Compressor rams this into combustion chambers at pressure of about 45 lb. per square inch.||Exhaust issues at 100 mph. It has no jet effect on propulsion. Windshield in top photo is replaced here with small windscreens. This photo and one at left are from Mechanics, London.|
|Instruments on dash are largely for testing. Dials on production model would report compressor and oil pressures, compressor speed. Controls are accelerator, brake, reverse lever.|
accelerated from a standing start to 60 miles an hour in 14 seconds. It
streaked up to 90 miles an hour with no apparent effort, and easily could
have bettered 100. If it tended to "creep" at a standstill, a
light pressure on the brake pedal would hold it stationary. The car had
practically no vibration, moving or standing still.
Outwardly, it looked like a standard British-produced open car with the rear seat blocked off to accommodate an extra-long turtleback. It did smell of kerosene- that lowly product of crude oil-and that was the tip-off.
By coincidence, at the same hour, almost 6,000 miles away in Seattle, Wash., a 10-ton truck was cruising the highways under the thrust of a kind of engine that was brand new to truck wranglers. The weight of the engine was less than a twelfth of that of a Diesel of comparable power, It occupied a, less than a tenth of the space that would have been taken up by a Diesel or gasoline engine and its accessories. It had only a tenth as many parts.
Rover engine is 3 feet long, 18 in. ewide, and 20 in. high. Turbine wheels have 5-in. diameter.
Gas turbine can be compared this way with piston engine.
Sixty of these tiny blades are on perimeter of both compressor and power turbines of Rover engine. Made of "Nimonic" nickel alloy steel, they must withstand constant gas blast of 1,5000 F. Due to high speed, balance is big problem in turbines. Engine idles at 7,000 r.p.m., turns at 36,000 at car speed of 90 m.p.h.
truck, too, had a faint kerosene odor. For the British automobile and the
American truck had this in common: they were the world's first highway vehicles
powered by gas turbines. They had engines that were close relatives of the
engines that drive today's ultrafast fighter planes, some of the newest
bombers, and that spectacular new British airliner, the Comet (PS, May '50,
Contrary to newspaper accounts,
this new automobile and new truck were not jet-propelled. They were not
moved by a hot tailpipe blast. Instead, their turbines produced shaft
power to drive the rear wheels.
car and the truck represent the first basic change in automotive power plants
since the invention of the internal combustion engine in the 19th Century.
The car was designed and built by the Rover Company, Ltd., of Birmingham,
England, as a "test bed" for road turbines (PS, Sept. '48, p.188).
The truck was powered by an engine designed and built experimentally by
the Boeing Airplane Co., of Seattle, maker of the Stratojet, the world's
The car and truck may bring a complete revolution in automotive power and design in the next five years-or less.
They may. No one knows just yet. There is a score of problems to be solved before the man on Main Street can walk into an automobile showroom and order the turbine job with the chrome exhaust ports. Or the truck fleet owner can buy mechanical horses -so compactly packaged that he can tote five to seven tons more cargo without increasing the length of his combo.
But those who have followed the progress of Rover and Boeing during the last couple of years are convinced that the day of turbine propulsion for passenger cars, trucks, and buses is almost a reality.
Turbine engine in truck is almost lost in chassis compared with Diesel at right. Vertical stack at far left (arrow) is one of two for exhaust. Truck was made by Kenworth Motor Truck Corp.
It wouldn't be surprising. The gas turbine as a replacement for the piston engine in aircraft is just coming into its 'own. The gas turbine as a shaft-power unit for propeller-driven aircraft will be flying the oceans as a 'turboprop" in a couple of years. Both the steam turbine and the gas turbine have been adapted to railway locomotives. Turbines are an old story to ocean vessels. It's about time that rubber-tired vehicles got a crack at the turbine.
any gas turbines, the ones in the Rover and Boeing-powered truck are vastly
simpler than a piston engine. Substantially, they have only six parts-a
compressor, two chambers to burn the fuel, a turbine to drive the compressor,
another turbine to develop shaft-power, and two shafts. Three or four, main
hearings 'will take all the load of a turbine engine. There are no other
bearings in the engine proper. There are no reciprocating parts. No pistons
jump up and down. Moving parts rotate like an old-fashioned waterwheel.
The engine has only two "cylinders." In this instance the "cylinders" are a couple of containers where kerosene is burned as simply as in an oil heater. The compressor does the same job as the piston on the compression stroke of a reciprocating engine- it compresses air. Any engine must have a lot of air to burn its fuel, and gas turbines must have an extraordinary amount of air. They are pigs for air.
Gas- and power-flow drawing of Boeing engine. It delivers shaft power via reduction gears.
power turbine is the gimmick, the key to the whole operation. The gases
that have driven tornado-like through the compressor turbine attack the
power turbine and spin it too. That produces shaft-power. Once you've got
shaft-power, you can move something. Gear down the Rover and boeing power-shafts,
and you've got torque for the rubber on the road.
It's no more complicated than that. The automotive turbine differs from an aircraft turbine in that it has two shafts. An aircraft turbine engine has only one. The reason for that is the same reason that a conventional automobile has a way of disengaging the engine from the rear wheels. If the automotive turbines were permanently geared to the rear wheels, it would stop every time the car stopped. So that second shaft, the power-shaft, is motionless when the car is at test. Like the propeller shaft in a conventional car, it is in constant gear with the wheels. The shaft on which the compressor and the-compressor's 'turbine turn isn't. It keeps going, whether the car is in motion or not. The power shaft delivers power as the driver needs it.
The power turbine revolves at a speed dictated by two conditions: the load on the engine and the amount of energy fed to it by the compressor. The speed of the compressor depends on the amount of fuel fed to the burning chambers. -On a hill, the turbine, assailed by an inferno of gases, twists harder. In one sense, when the car hits smooth sailing on a straight away the turbine becomes a "fluid" coupling between the compressor and the wheels.
that's on the plus side. So is quick starting, characteristic of the turbine
engine. It will roll without a whimper at 650 below zero. It doesn't cough
or die under load.
On the plus side too are the absence of a continuously operating ignition system, and the turbine's smaller size. Fitted with tur bines, today's cars could be lowered several inches. Hoods could be shorter, increasing road visibility. Cars could be aerodynamically cleaner. There is no radiator to propel against the air.
The turbo car (as they are dubbing it here in England) can have a much lighter chassis without sacrifice of strength because the engine is light. That would boost fuel mileage. Moreover, it burns cheap fuel. A turbine will run on almost anything short of firewood. For railway use, they are even experimenting with powdered coal. Boeing proposes using natural gas.
Boeing engineers have succeeded in silencing normal whine and roar of gas turbine through big muffler at far right. Turbine has been under development for U. S. Navy Bureau of Ships.
Within this quartz jacket, gas-turbine combustion is under study. Boeing engineer observes how and where burning occurs. Research is resulting in lower fuel consumption, higher power.
sheer simplicity should make a turbo car's or turbo truck's maintenance
costs considerably below those on a piston vehicle. Removing the Boeing
turbine engine, dismantling- it, inspecting it, reassembling it, and putting
it back in the chassis is a job for one man-in just six hours. He doesn't
even need a chain hoist.
Gas turbines supply extra dividends.
The turbine-powered passenger car or truck doesn't need a special heater
to keep its human cargo warm in frigid weather. Heat can - be bled off
the compressor at will.
All this sounds too good to be true. There has to be a catch somewhere. Actually, there are a good many of them. The biggest drawback to the gas turbine for road vehicles is that it does its best at near-maximum r.p.m. It falls down in its power delivery at low speeds, or part-load, as the engineers say. And automobiles, trucks, and buses operate a lot more at part-load than they do at full load. The cure for this ailment may be a transmission, the same device that piston engines use to overcome their problem of low torque at low speeds.
Gas turbines are notorious for low fuel mileage. They develop a lot of heat but they waste too much of it. The Rover's engine, rated at 200 brake horsepower, gets around six miles to the gallon of kerosene. Using kerosene, the Boeing turbine, rated at 175 hp., is three and a half times more expensive to run than a Diesel.
There is a reason for that.
It goes right back to that voracious appetite of a gas turbine for air.
In a piston engine about 4,5000 F. is developed in a cylinder head at
the instant of fuel explosion, the start of the power stroke. The engine
metals can stand this only because the explosions are intermittent. Water
jackets, air, and oil keep carrying away the heat.
Diagram by R.H. H. Barr, British engineer, indicates how heat exchanger can be adapted to a gas-turbine engine. Power Jets, Ltd., of London, pioneer in gas-turbine research for propulsion of road vehicles, holds copyright on drawing and concept of this type of engine.
ultimate solution to better efficiency is better metals. The metallurgists
are working on that one. Gas turbines will have to do a lot better ii~ passenger
cars before the crossroads of Great Britain and America grow forests of
kerosene pumps. It may be another story on gas-turbine trucks, though. Fuel
costs in trucking are the least of the operator's worries.
Preheaters May Help
Heat exchangers, transferring heat from burned gases to incoming air, will help fuel mileage. Pre.heating the air before it is burned may double the fuel mileage. That merely means better combustion, like getting a better draft in a fireplace.
There are other stoppers for the present. High engine speeds pose problems of exact balance or possible bearing overloads. Then, too, gas turbines don't do as well in summer heat as they do in the winter; the compressor can't bite thin, hot air as well.
For the first two or three seconds, acceleration from a dead stop is poor on the Rover. The engine is sluggish initially because it takes time to get the power turbine up to speed. But once it starts rolling, it goes. The jump from 10,000 r.p.m. to 15,000 takes just three seconds. Boeing smartly put a gearbox in its job. The truck's acceleration leaves nothing to be desired.
Noise in the automotive gas turbine can be another problem. The Rover car hisses and whines. On sudden acceleration it roars. The noise comes from air intakes, compressor vanes, reduction gearing, and exhausts. Filters, insulation, and muffling may reduce the decibel level of turbo cars to that of piston-driven vehicles. Boeing has succeeded in reducing the noise level to less than that of piston-driven trucks.
Boeing, too, has whipped the problem of getting engine-assisted braking in going downhill. So far, Rover hasn't.
Says Turbos Are Coming
But no less an expert than England's leading lay authority on the gas turbine, C. Geoffrey Smith, editorial director of Autocar, and the first man ever to drive a gas-turbine car 90 m.p.h.; says, "The Rover in performance already compares favorably with the modern piston-engine automobile- which has 50 years of experience behind it. I don't say the turbo car is here yet as salable article. But it's coming. It's bound to."
So it may well be that presently
you will roll up to a service-station pump and say, "Ten, please-of
the lowest octane you've got."