Page 56 - The Jet Engine

Fig. 5-1 A triple-stage turbine with single shaft system.

from the gas flow, the rotational speed at which it ratio fan engines that feature an intermediate
must be produced and the diameter of turbine pressure system, another turbine may be interposed
permitted. between the high and low pressure turbines, thus
forming a triple-spool system (fig, 5-3). On some
3. The number of shafts, and therefore turbines, engines, driving torque is derived from a free-power
varies with the type of engine; high compression ratio turbine (fig. 5-4). This method allows the turbine to
engines usually have two shafts, driving high and low run at its optimum speed because it is mechanically
pressure compressors (fig, 5-2). On high by-pass independent of other turbine and compressor shafts.

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