chapter 7 Flashcards
(37 cards)
What are some of the sources used to heat the fuel in a turbine engine fuel system?
Bleed air and engine lubricating oil.
What are the most common types of fuel metering systems used on small reciprocating en-gines?
Float-type carburetors, pressure-injection carburetors and direct fuel injection systems.
What function does the mixture control perform?
Controls the fuel/air mixture.
What generally causes spark plug fouling?
Operating the engine with an excessively rich mixture at idle.
What is the purpose of an accelerating system?
It provides an immediate but brief increase in fuel flow in the venturi to enrich the mix-ture. (Page
What is a carburetor economizer system?
- It is a power enrichment system that provides a richer mixture at high power settings, where the excess fuel aids in engine cooling. This system functions at throttle settings above cruise power settings.
When the mixture is placed in the idle-cutoff position, a slight rise in r.p.m. is noted prior to the engine decelerating. What does this indicate?
The idle mixture is set correctly.
Why should engine r.p.m. be accelerated periodically when making carburetor adjustment
- To clear the engine.
What maintains the fuel pressure in a pressure-injection carburetor?
An engine-driven fuel pump.
What happens if the manual mixture control of a pressure injection carburetor is moved to the idle cutoff position?
The engine stops.
How does an automatic mixture control (AMC) function?
A sealed brass bellows connected to the fuel metering system, expands and contracts with changes in pressure and temperature, adjusting the mixture accordingly.
What are some of the advantages of fuel injection systems over carburetor systems?
Less danger of induction icing, better acceleration, better fuel distribution, better fuel econ-omy, reduced overheating of individual cylinders.
What purpose do turbine engine fuel control units serve?
They automatically meter fuel to the engine.
What are the two basic types of turbine engine fuel control units?
Hydromechanical and electronic.
What are the engine variables detected by the fuel control unit?
Power lever position, engine r.p.m., compressor inlet temperature, compressor inlet pres-sure, compressor discharge pressure, burner pressure.
What are the two major components of a supervisory electronics engine control?
The electronic control unit (computer), and the hydromechanical fuel control.
What are some of the advantages some of the advantages of a full-authority digital engine control (FADEC) over a hydromechanical fuel control?
- Better fuel economy, improved starts, requires no endine trimmina provides encine a ments, fully modulates the active clearance control, and allows more repeatable engine
What do turbine engine fuel spray nozzles do?
They inject fuel into the combustion
What are the different engine indications used for trimming a turbine engine?
either EPR, rpm
what maintenance adjustment are normally allowed on installed hyromechanucal fuel control
specific gravity for fuel, idle rpm, maximum rpm
what type of pump can vary amount of fuel discharged regardless of speed
variable displacement pump
what is used to keep water, sediment, foreign matter out of carburetor
main fuel strainer
What type of engine-driven fuel pump is widely used other than gear or piston pumps?
A rotary vane type.
What is the purpose of a pressure relief valve in a constant displacement pump
It returns excess fuel that is not required by the engine to the inlet side of the pump.
