text: The compressor has to run with the same speed (or fixed gear ratio) as its driving turbine and have equal power and pass the same flow as its driving turbine. This constitutes a gas generator which produces gas power. The compressor also has to pass the same flow as whatever uses the gas power, ie additional turbine stages for a single shaft engine or separate power turbines or a jet nozzle. This equal-flow requirement is alongside an equal pressure-ratio requirement, between overall compression and expansion ratios, and together they position the running line for steady state operation.
  Single-shaft engines which drive an electric generator or helicopter rotor/aircraft propeller run with the compressor at no-load while accelerating to operating speed. No-load refers to a minimum fuelling as necessary to run the generator with no electrical load or rotor/propeller pitch at a minimum and occurs close to choke. Cohen et al. show electrical generators run up to required speed at no load. An increase in electrical load is obtained by increasing fuel flow. Barkey et al. give a detailed description of the sequence of events which bring the generator turbine to design speed, or grid frequency, with no load before increasing fuel as the load comes on. Grandcoing shows the Turbomeca Artouste helicopter engine constant speed operation from no-load idle to maximum power. No-load is minimum rotor pitch and idle fuel flow. The increase in fuel flow is shown on a compressor map as lines of constant engine temperature ratio, Turbine inlet temperature/Compressor inlet temperature. Grandcoing also shows the effect of a rapid load increase where the speed droops before regaining its required setting.