Powerplant Chapter 07 Flashcards
Engine Fuel and Fuel Metering
What are the most common types of fuel metering systems used on small reciprocating engines?
Float-type carburetors, pressure-injection carburetors and direct fuel injection systems.
What are some of the sources used to heat the fuel in a turbine engine fuel system?
Bleed air and engine lubricating oil.
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 mixture.
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 peiodically when making carburetor adjustments?
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 economy, reduced overheating of individual cylinders.
What purpose do turbine engines 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 RPM, compressor inlet temperature, compressor inlet pressure, compressor discharge pressure, burner pressure.