Press Information Service
Detroit 31 Michigan
HIGHUGHTS OF GAS TURBINE ENGINE DEVELOPMENT PROGRAM AT CHRYSLER CORPORATION
Chrysler Corporation -- the first major U.S. auto manufacturer to be awarded prime contracts by the U.S. Government for missile development and production - - has a long history of interest in the gas turbine engine.
Brief engineering surveys of gas turbine potentialities for automotive use had been made prior to World War II. These studies showed that although the gas turbine engine had strong possibilities of being an ideal automobile engine, neither materials nor techniques had advanced to the point where the cost and time of research would be warranted.
Chrysler Corporation became directly involved, during World War II, in the development of aircraft turbine engines and superchargers as part of its defense production program.
Chrysler engineers resumed limited experimental work on a laboratory auto gas turbine engine in 1945. Also at this time, because of the firmís early interest in gas turbine theory, Chrysler was awarded a research and development contract by the U.S. Navy to create a turboprop engine for aircraft, This program - - although terminated in 1949, due to lack of military development funds in the pre-Korean War period, -- resulted in the development of a turboprop engine which achieved fuel economy approaching that of aircraft piston engines and resulted in new knowledge of the perplexing problems involved in translating gas turbine theory Into practical application.
With this additional experience at hand, Chrysler research scientists and engineers returned to their original objective -- the automotive gas turbine engine.
Chryslerís first gas turbine engine was designed primarily as a laboratory tool to check the performance of various components placed together as a power plant and to help determine if a small gas turbine based on the regenerative principle would be practical in an automobile.
This engine, rated at 100 true brake horsepower, was installed in a 1954 standard Plymouth passenger car, the first serious attempt by an American auto firm to apply a gas turbine engine to an in-production automobile rather than to a special test-bed vehicle.
Later, the success of this first engine was graphically demonstrated in a transcontinental test run from New York City to Los Angeles in March 1956, using a standard production Plymouth as a turbine-powered vehicle. Relatively good fuel economy -- 13 to 14 miles per gallon -- was achieved throughout the trip although this component test engine was not in any sense a developed power plant.
The New York City-Los Angeles run also marked the first time the continent had been spanned by a turbine-powered passenger car and proved the first practical application of the regenerative principle in operation over standard U.S. highways.
Through extensive experimentation and design modification, Chrysler engineers gradually reduced the inherent problems of the gas turbine bit-by-bit. Basing their calculations on performance results of the 1956 cross-country test run, they decided to enlarge the second engine, developed in 1957, to get more power and to simplify some of the basic problems encountered in the smaller engine, it was rated in the 200-horsepower range and in essence, because it was a larger engine, the second generation engine was easier to work with. It became a more practical laboratory tool and, in the process, eliminated some of the problems existent in its smaller brother.
To support laboratory findings, the second-generation gas turbine engine was installed in a standard Plymouth passenger car for operation over a 576-mile highway test, from Detroit to New York, in December of 1958. The engine achieved economy of 19.4 miles per gallon at a constant speed of 37 miles per hour and on the return trip achieved 17.25 miles per gallon at an average speed of 52.5 miles per hour, including stops, city traffic and highway driving.
Successful though it was, and a decided advance over its predecessor, the second engine was larger than desired for practical passenger car use, Chrysler engineers decided. So a decision was made to redesign the engine for a third time, making it smaller, incorporating the benefits of the lessons learned from work on the previous engines.
The result of this design decision was the development of the third generation of Chrysler gas turbine engines, the present Model CR2A which is a much more practical device than its ancestors and is essentially intended for use in a passenger car.
Its most satisfying features, Chrysler engineers say, have been its smaller size, reduced weight (about two-thirds that of a comparable piston engine), improved economy and particularly its reduction of acceleration lag. (The first gas turbine engine had an acceleration lag of seven seconds from idle to full-rated output; the second engine required three seconds to achieve maximum vehicle acceleration; the third engine -- the present Model CR2A -- requires less than one and one-half seconds to accomplish the same performance,)
The present gas turbine engine has a gas generator speed of 20, 000 rpm when the engine is operating at idle. When the fuel (gas) pedal in the driverís compartment is depressed to accelerate the vehicle, that speed increases to 45,000 rpm within one and one-half seconds, which is design speed for the engine.
It is this amazing speed-up of moving parts that accounts for the smooth get away and acceleration rate of the turbine-powered car, Under such acceleration conditions, the increase in movement is a smooth, steady one for the passenger and driver,
Under present conditions, the piston engine vehicle might have a slight initial edge on acceleration but it is overtaken by its counterpart turbine-powered car in a very short time. Within, a matter of seconds, the piston-powered vehicle cannot hope to equal the performance of the same type of gas turbine-powered vehicle.
Such performance gains result from continued improvement of compressor and turbine design and higher torque availability, Chrysler engineers point out.
Some of the turbine engine problems solved by Chrysler research scientists and development engineers since 1945 are astonishing, to say the least.
From the burner through the turbines, there is a drop in pressure of the gases to atmospheric pressure, but the gases retain large amounts of heat, which would be wasted if merely allowed to escape through the exhaust pipe. So a device for salvaging this heat is placed in the path of the out-rushing gases. This component is the famous Chrysler originated regenerator, a form of heat exchanger. It recovers heat from the hot exhaust gases and transfers this energy to the high-pressure air coming from the compressor. This lightens the burnerís job of raising the gas temperature for entry to the turbines. The result is conservation of fuel as well as lower exhaust temperatures.
The key to outstanding performance in the Chrysler turbine engine Is a variable second-stage nozzle mechanism. This device allows continuous automatic variation of the nozzle blades with gas generator and vehicle speed, so that the gas flow is directed to the power turbine wheel blades at an angle of attack optimum over the entire operating range for the achievement of economy, acceleration, or braking.
Reversing the nozzles makes it possible to obtain greater engine braking than from a piston engine with a torque converter drive. The braking torque is appreciable at high power turbine speeds, and a small reverse torque can actually be obtained with the power turbine stalled.
Early in the gas turbine engine development program, Chrysler project engineers realized they could not use large quantities of high-cost alloys if their turbine engines were to be mass-produced. For one thing, the free-world supply of some of these alloys would not be sufficient to meet the requirements of even a small-scale passenger car gas turbine production program.
Therefore, they set out to do the impossible: to develop a low-cost, low- strategic alloy content material for turbine buckets which would have the high temperature strength, stress rupture, and creep characteristics of a much used and well-known cobalt-base alloy.
Chrysler metallurgists developed such metals, one of which has a stress- to-rupture value at high temperature, of 30,000 pounds per square inch and the other equal to 27,000 pounds per square inch under the same conditions.
Another alloy program by Chrysler metallurgists proved highly successful and led to the development of an oxidation-resistant material. This material is now used for the gas turbine engineís burner liner and in other internal parts.
In the all-important field of fabrication and joining metals, Chrysler had to develop processes, which would lend themselves to production as well as be reliable.
They found, for instance, that they could either cast a turbine wheel ring together with alt its blades and weld to it a combined hub and disc of lower alloy, or cast the entire disc with its blades as a single unit. Both processes have proven feasible for high-production manufacturing at a modest cost.
As far as Chryslerís production experts are concerned, they have to create a textbook on the machines and techniques that have to be devised to build turbine engines economically. Otherwise, no major technological or material problems now remain which could render production of the gas turbine engine for passenger car use unlikely. Progress in turbine engine development in the past two years has far exceeded expectations and the rate of improvement is moving steadily upward with each refinement of the component engine.
Further improvements in fuel economy, reliability, performance, simplicity, cost, materials developments and weight (as well, as reduction in size) are inevitable.
Theoretically, a gas turbine engine could run forever because of Itís simplicity and because it is a frictionless machine. Air and heat (fuel) do the work. Because the turbine is basically the most simple of manís power machines (a windmill or waterwheel is a turbine), it has few working parts.
Page updated 4-15-2004