A 3-Shaft versus a 2-Shaft Cycle in Automotive Gas Turbines

A 3-shaft cycle turbine with a twin-spool compressor system is compared to a 2-shaft cycle with a variable geometry power turbine. Operating in a heavy commercial vehicle, the following engine parameters are considered: specific output power, fuel consumption, engine response, torque characteristics, and engine braking capability.

The 3-shaft cycle showed an average improvement of 5% in sfc, a stall torque ratioof 3.8 versus 2.65 for the 2-shaft cycle, a potential increase in engine braking capability, and engine response consistent with the 2-shaft cycle.