|Fig. 17-3 A typical compressor inlet injection system.|
5. The compressor inlet injection system shown in fig. 17-3 is a typical system for a turbo-propeller engine. When the injection system is switched on, water/methanol mixture is pumped from an aircraft- mounted tank to a control unit. The control unit meters the flow of mixture to the compressor inlet through a metering valve that is operated by a servo piston. The servo system uses engine oil as an operating medium, and a servo valve regulates the supply of oil. The degree of servo valve opening is set by a control system that is sensitive to propeller shaft torque oil pressure and to atmospheric air pressure acting on a capsule assembly.
6. The control unit high pressure oil cock control lever is interconnected to the throttle control system in such a manner that, until the throttle is moved towards the take-off position, the oil cock remains closed, and thus the metering valve remains closed, preventing any mixture flowing to the compressor inlet Movement of the throttle control to the take-off position opens the oil cock, and the oil pressure passes through the servo valve to open the metering valve by means of the servo piston.