Engine fuel systems Flashcards
(19 cards)
What type of pump can vary the amount of fuel discharged regardless of speed?
A variable displacement pump
What is used to keep water, sediment and foreign matter out of the carburetor?
The main fuel strainer
What is the purpose of a pressure relief valve in a constant displacement pump?
It returns access fuel that is not required by the engine to the inlet side of the pump
What type of engine driven fuel pumps are widely used other than gear or piston pumps?
Rotary vane type pumps
What function do fuel boost pumps perform?
They supply pressurized fuel to the fuel pump which helps prevent vapor lock and cavitation
What is a commonly used type of fuel boost pump?
A centrifugal type pump
What causes vapor lock and why is it a concern?
Vapor lock can be caused by insufficient fuel pressure high fuel temperatures and excessive fuel turbulence. Vapor lock can completely block fuel flow, resulting in engine failure.
Why is vapor lock serious?
Fuel flow can be completely blocked, resulting in engine failure
What does the use of fuel boost pumps help prevent?
Cavitation and vapor lock
What function does the engine driven pump on a turbine engine perform?
It provides a continuous supply of fuel at the proper pressure while the engine is running
Name the two categories of turbine engine pumps:
Constant displacement
Variable displacement
What category is a gear type pump classified in?
Constant displacement
When performing an external inspection of an engine driven fuel pump what should you look for?
Leaks and security of mounting
What is the purpose of a sheer section on a driveshaft in a dual element constant displacement pump?
If one element fails, the other element continues working
Where in a turbine engine fuel system is ice formation likely to occur and how is it prevented?
Ice formation is most likely to occur in the fuel filter. It is generally prevented by using an engine oil or bleed air heat exchanger to warm the fuel.
What is the purpose of a bypass valve in an engine fuel system micron filter?
Allows unfiltered fuel into the engine if the filter becomes blocked
What is the purpose of duplex fuel nozzles?
Provide different spray patterns, wider during start up and acceleration and narrower when engine speed is above idle
What are the functions of the pressurizing and dump portions of a pressurizing and dump valve?
The pressurizing portion provides primary and secondary fuel flow to a dual line duplex, fuel nozzle
The dump portion allows fuel to drain from the manifolds after engine shut down
What purpose do fuel selector valves serve?
They allow tank and engine selection and provide a means of shutting off fuel flow
