Friday, March 16, 2012


Fig. 17-4 A typical combustion chamber injection system.
7. The  combustion  chamber  injection  systemshown in fig. 17-4 is a typical system for a turbo-jet engine. The coolant flows from an aircraft-mounted tank to an air-driven turbine pump that delivers it to a water flow sensing unit. The water passes from the sensing unit to each fuel spray nozzle and is sprayed from two jets onto the flame tube swirl vanes, thus cooling the air passing into the combustion zone. The water pressure between the sensing unit and the discharge jets is sensed by the fuel control system, which  automatically  resets  the  engine  speed governor to give a higher maximum engine speed.

8. The water flow sensing unit opens only when the correct  pressure  difference  is  obtained  between compressor  delivery  air  pressure  and  water pressure. The system is brought into operation when the engine throttle lever is moved to the take-off position,  causing  microswitches  to  operate  and select the air supply for the turbine pump. 9. The sensing unit also forms a non-return valve to prevent air pressure feeding back from the discharge jets and provides for the operation of an indicator light to show when water is flowing.

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