TOPIC 03.2 - FUEL INJECTION SYSTEMS Flashcards
ADDITIONAL CONCEPTS
2 major limitations of carburetors:
- fuel/air mixture is not evenly distributed to the cylinders
- susceptible to carburetor icing
When fuel is injected directly into the combustion chamber, the injection system is referred to as _______.
Direct fuel injection system
This type of fuel injection system was used on early radial engines and offered benefits of even fuel distribution and a reduced chance of backfiring.
Direct fuel injection system
This is the most common type of fuel injection system in reciprocating aircraft engines.
Indirect fuel injection / Continuous-flow fuel injection system
This system continuously injects fuel into each intake port instead of mixing the fuel and air in the combustion chamber.
Indirect fuel injection / Continuous-flow fuel injection system
In this type of system, a throttle-metering valve varies the pressure of fuel according to airflow to the engine.
Indirect fuel injection / Continuous-flow fuel injection system
In this system, mixture strength is varied by a manually operated mixture control valve, which adjusts the fuel pressure for altitude or operating conditions, as necessary, and which is also used to cut off the fuel supply when stopping the engine.
Indirect fuel injection / Continuous-flow fuel injection system
In an indirect fuel injection/continuous-flow fuel injection system, this varies the pressure of fuel according to airflow to the engine.
Throttle-metering valve
In an indirect fuel injection / continuous-flow fuel injection system, this varies mixture strength, adjusts fuel pressure for altitude or operating conditions, and is used to cut off the fuel supply when stopping the engine.
manually operated mixture control valve
Main components of an indirect fuel injection:
- Fuel pump
- Fuel/air control unit
- Fuel manifold valve
- Discharge nozzles
- Throttle valve
- Fuel pressure gauge
2 fuel pumps an indirect fuel injection is equipped with:
- Electrical pump
- Engine driven pump
This is used in case of a malfunction of the engine driven pump and for engine priming and starting.
Electrical pump
Parts in a fuel/air control unit:
- Throttle valve
- Mixture control valve
- Fuel metering valve
This is connected to the pilot’s throttle lever and controls the airflow to the engine.
Throttle valve
This is connected to the pilot’s mixture control lever, and bleeds off fuel pressure applied to the metering fuel valve
Mixture control valve
This can also close completely, acting as the idle cut off control.
Mixture control valve
This is mechanically connected to the throttle valve and controls fuel flow from the mixture control valve to the fuel manifold valve, thus, fuel flow to the manifold valve and to injectors is proportioned to airflow.
Fuel metering valve
This is the central point for distributing metered fuel to the engine.
Fuel manifold valve
When the engine is stopped, what is the position of all the outlet ports?
Closed
As the fuel pressure builds up, what happens to all the ports to the discharge nozzles?
Open simultaneously
When the inlet pressure drops below a certain level, this closes the fuel inlet, which shuts off all the fuel to the discharge nozzles.
Diaphragm
This is located in each cylinder head, with its outlet directed into the inlet port.
Fuel discharge nozzle
What kind of engines use a nozzle with a calibrated orifice, which has holes for air entry to the lower chamber?
Normally aspirated engines
Nozzles used in this type of engines have turbo-charged output air delivered to a shroud surrounding the nozzle, where output air is forced into the injector to assist in atomizing the fuel spray.
Turbo-charged engines
This is a means of preventing manifold air starvation, caused by blockage from icing or other ingested materials.
Alternate air door
This will shut off the ram air, and at the same time, admit unfiltered air from inside the cowlings directly into the injector air body throat.
Alternate air door
