Throttle - Other Engines

Other Engines

Most engines have some kind of throttle control, though the particular way that power is regulated is often different.

Steam locomotives normally have the throttle or "regulator" in a characteristic dome at the top of the boiler. The additional height afforded by the dome helps to avoid any liquid (e.g. from bubbles on the surface of the boiler water) being drawn into the throttle valve, which could damage it. The throttle is used in conjunction with the reversing lever to start, stop and to control the locomotive's power although, during steady-state running of most locomotives, it is preferable to leave the throttle wide open and to control the power by varying the steam cut-off point (which is done with the reversing lever), as this is more efficient. A steam locomotive throttle valve poses a difficult design challenge as it must be opened and closed using hand effort against the considerable pressure (typically 250psi) of boiler steam. Examples include the balanced "double beat" type used on Gresley A3 Pacifics.

Liquid rockets are throttled by controlling the pumps that send liquid fuel and oxidizer to the combustion chamber. Solid rockets are not controllable once their solid fuel is ignited. Hybrid rockets, like the one used in Space Ship One, use solid fuel and liquid oxidizer; thus, throttling is possible through the oxygen pumps, as in a full liquid rocket motor.

In a jet engine, engine output is also directly controlled by changing the amount of fuel flowing into the combustion chamber. In some instances, a "throttle" is known as a "thrust lever" (as in most Airbus and Boeing aircraft). This is chiefly due to the fact that "throttle" is associated with traditional gasoline engines.