.New G.M. Gas Tu rbine for Heavies
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ikNEW 280-h.P. regenerative gas turbine designed specifically for heavy-duty commercial vehicles has been developed by General Motors Research Laboratories and will be exhibited at the New York World's Fair, which opens on April 22 and closes on October 18. The new engine is known as the GT-309, and is a fifth-generation design with more than 15 years of research and development behind it: it will he recalled that one of the first G.M. gas turbines for vehicle use was' installed in the Turbocruiser bus in 1954.
The new engine has the same basic components as previous turbines—compressor, gasifier turbine, power turbine and regenerator—but a new system termed Power Transfer is incorporated whereby a variable coupling or clutch transfers a predetermined amount of power from the engine's gasifier turbine to the output shaft, This maintains a virtually constant turbine-inlet temperature over most of the engine's operating range, it is claimed. When the vehicle is decelerating, the Power Transfer couples the transmission line to the turbine compressor and provides two to three times the braking power of a comparable petrol or diesel engine.
According to Dr. Lawrence R. Hafstad. vice-president in charge of the Research Laboratories, the Power Transfer improves the new turbine's part-load fuel economy, and also gives better acceleration, limits the power-turbine speed and makes the use of manual or automatic transmissions possible. The GT-309 develops its rated 280 h.p..at an outputshaft speed of 3,603 rep.m.. this being stepped down from a power-turbine-shaft speed of 30,480 r.p.m. It has a failing torque curve, with maximum torque near the stall speed, and it is claimed to occupy one-third less space arid to we,gh less than half the weight of a diesel engine of equivalent performance. The gas temperature at the gasifier-turbine inlet is 927C. (1,700°F.), and the single regenerator results in exhaust temperatures in the 150°-260C. (300"-500F.) range, and salvages more than 90 per cent of the recoverable exhaust-system heat.
Several GT-309 gas turbines are being evaluated under a variety of operating conditions in vehicles and on G.M. Jest beds.