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J. engine fuel sys
engine fuel systems 10
Question | Answer |
---|---|
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 return excess fuel that is not required by the engine to the inlet side of the pump. |
what type of engine-driven fuel pump is widely used other than gear or piston pumps? | a rotary vane type. |
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? | the centrifugal type. |
what causes vapor lock and why is it of concern? | vapor lock is caused by insufficient fuel pressure, high fuel temps and excessive fuel turbulence, which may completely block any fuel flow resulting in engine failure. |
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 and variable displacement. |
what category is a gear-type pump classified in? | constant displacement. |
when performing an internal inspection of an engine-driven fuel pump, what should you look for? | leaks and security of mounting. |
what is the purpose of a shear section of the driveshaft in a dual element constant displacement pump? | if one element seizes, a portion of the driveshaft seizes, allowing the other element to continue to operate. |
where in a turbine engine fuel system is ice formation likely to occur and how is it prevented? | the fuel filter is most susceptible to ice formation, so a fuel heater is used that consists of a heat exchanger using either engine oil or bleed air to warm the fuel. |
what is the purpose of a bypass valve in an engine fuel system micron filter? | it is a safety feature that allows fuel to flow to the engine if the filter becomes blocked. |
what is the purpose of a duplex fuel nozzle? | a duplex fuel nozzle discharges two different spray patterns. the spray pattern is wider during start up and acceleration and narrows when engine speed increases above idle. |
what are the functions of the pressurizing and dump portions of a pressurizing and dump valves? | the pressurizing portions primary and secondary fuel flow to dual-line duplex fuel nozzles, and the dump portion allows fuel to drain from the manifolds after engine shutdown. |
what purpose do fuel selector valves serve? | they allow tank and engine selection, and provide a means for shutting off fuel flow. |
what could happen to an oil that is too low in viscosity at normal engine operating temperatures? | it may become so thin that the oil film between moving parts is easily broken resulting in premature wear. |
name two types of turbine engine oil coolers. | air cooled and fuel cooled. |