Chevrolet Express Gas Turbine Propulsion Research Vehicle 1984

In 1984, General Motors presented the Chevrolet Express research sedan for the 75th Anniversary of its Chevrolet Division. The Chevrolet Express, at the time, was intended at illustrating the American Sedan of the year 2000; automobile was in competition with airplane for inter-city travelling. The Chevrolet Express was presented, in 1984, as a vehicle to provide inter-city commuters with an alternative to the hassle of short-distance air travel. The General Motors description at the time was as follows:

 Its .195 aerodynamic drag coefficient helps provide a safe 150 mph cruising speed and 25 miles per gallon fuel economy, usually incompatible characteristics.
Prospective customer for the Chevrolet Express might live in a large metropolitan area, have a long daily commute and travel often to nearby metropolitan areas. The Chevrolet Express offers convenient, personal mobility to make these trips convenient.
A commuter could pull out in the morning and drive the Chevrolet Express to a special limited-access highway built exclusively for the Chevrolet Express and similar vehicles.
Once on the special highway, the Chevrolet Express would cruise at speeds up to 150 mph, avoiding traffic jams and not bothered by bad weather. Upon nearing its destination city, The Chevrolet Express would leave the limited-access roadway and rejoin the normal traffic flow.

The Chevrolet Express was developed jointly by General Motors Advanced Styling Design Centre in California and the Advanced Engineering Centre at Warren, Michigan. The aerodynamic body consists of a single volume shape with flowing lines; access to the four seats is by a large enveloping glass canopy that tilts forward.
The propulsion system is based on AGT5 Advanced Gas Turbine. Gas Turbine established a revolution in the airplane industry while substituting the reciprocating piston internal combustion engine. A similar trend was expected for the automobile industry in early 1950s. Several manufacturers developed research prototypes to evaluate the solution. General Motors developed the Firebird I 1952 through Firebird III 1958 while Chrysler had its Limited Edition Gas Turbine prototypes in field test in 1963. Other prototypes were developed by Rover Jet 1 Gas turbine 1950, Fiat Turbina 1954 or Renault Etoile Filante 1956. The advantages of the gas turbine for automobile propulsion (no vibration, only rotating components, multi-fuel flexibility..) could not overcome excessive fuel consumption and pollutant emission. It was considered that one limitation was the operating temperature defined by the available materials thermal resistance. During the 1980s, the advent of new industrial ceramic materials, supporting high temperature, resulted in new development for automobile Gas Turbine. In the U.S.A. the Department of Energy (DOE) funded some AGT (Advanced Gas Turbine) programs involving General Motors or Ford. In Japan MITI (Industry & Trade Ministry) supported a similar program involving Toyota, Mitsubishi and Nissan. In Germany, some developments have been conducted by Daimler Benz. The new projects utilized high temperature resistant industrial ceramics for prototype automobile gas turbine. Several Companies were hoping to finally develop a substitute to the reciprocating piston internal combustion engines. The industrial ceramics were expensive in mass production and would turn out to be too brittle, so that this new attempt for the emergence of gas turbine in automobile propulsion was short-lived.

Other features of the 1984 Chevrolet Express include graphite-reinforced plastics for all major exterior body panels, except the hood and engine cover. There was also state-of-the-art four wheel independent suspension, cathode ray tubes (CRTs) for display of various items and vehicle monitor systems. An ETAK navigation system would allow the driver to enter a destination into the system, and see the correct route plotted on a digitized map which is presented by one of the CRTs on the instrument panel.
A few of the mentioned technologies have come to reality after year 2000, but the essential of the Chevrolet Express Project still remains a proposition for the future.

Operating Principle of a Gas Turbine with Heat Regenerator for automobile propulsion

The operating principle of a gas turbine is simpler than a reciprocating piston internal combustion engine. There are only three rotating parts not in rubbing contact with their surrounding cases as shown in the above simplified diagram. There are two shafts. The first shaft supports the air compressor and the primary turbine while the second shaft supports the power turbine and transfers the power by gear reduction to the wheels. An electric starter provides assistance by rotating the air compressor for the starting procedure. Compressed air is fed to a combustion chamber where it is mixed with fuel and ignited. Hot and high pressure gases are generated and sent to the primary turbine before reaching the power turbine. The primary turbine rotates with the air compressor. Hot gases would then be sent to the exhaust system. In order to improve efficiency, the hot gases could be passed through a rotating ceramic heat regenerator, heating this element. Fresh air from the compressor is passed through this regenerator and is preheated. Using preheated air for the combustion reduces fuel requirement and thus improve the gas turbine efficiency.

- Text Paul Damiens - Photos General Motors -

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