fuel metering

Biggest advantae that a fuel injector has over a pressure carburetor

even fuel distribution

difference between spurt/direct injection and continuous fuel injection system

direct= timed spurts. continuous=continuously flowing

2 reasons we spray fuel on to our intake ports with certain fuel injection designs

better atomization

cooling

what is the purpose of the constant head spring in the RSA fuel injection system

keeps poppet valve off seat

purpose of the flow divider in a fuel injection system

divide fuel into individual cylinders

main difference between continental fuel injection and the RSA fuel injection

RSA uses Air as the main metering system. Teladyne uses Engine RPM as Main Metering system

two parts of hydromechanical FCU

Fuel metering section

computing section

two main types of nozzles used in turbine engines

Atomizing

Vaporizing

3 disadvantages of float Carburetor

Abrupt manuevers(starve engine of fuel), uneven fuel distribution to cylinders, Carburetor Ice.

How do pressure carburetors fix the abrupt movement issue

by removing the float and pressurizing the carburetor, abrupt movements have no effect on carburetor operation

how does the pressure carburetor fix the Carburetor ice issue

by placing fuel discharge nozzle after throttle plate, carb ice build up on throttle plate is mitigated

2 main metering forces in carburetor

Air metering

Fuel metering

explain how idele cut off is achieved in a pressure carburetor

3 basic principles that float carburetors use for operation

Bernoulli’s principle:in convergent duct Velocity increases as pressure decreases in divergent duct pressure increases as velocity decreases

Pressure differential: areas of high pressure move to areas of low pressure

pressure building behind obstruction: throttle plate forces pressure to build upstream of throttle plate

How does back suction mixture work in a float type carburetor

flows fuel by varying pressure in bowl, changing pressure differential

Aviation standard day

29.92 in/Hg. 59 degrees ferenheit 0ft altitude

how does air bleed economizer work in float type carburetor

varying airflow of air bleed economizer, enrichening mixture (less air=more rich)(more air=more lean)

if idle mixture is set correctly why does engine rpm rise slightly when engine is shutoff

increase in rpm occurs when mixture “passes” best power mixture ratio

what causes afterfiring? where does it occur

too rich of mix, occurs in exhaust

what causes backfiring? where does it occur

Too lean of a mix, occurs in intake

3 types of induction system icing

Throttle ice

fuel evaporation ice

Impact ice

4 parts of a naturally aspirated induction system

inlet

inlet filter

fuel metering device

intake manifold

3 ways to prevent, remove, or bypass induction system icing

carb heat

anti ice fluid

bypass/Alt air

5 types of mixtures

rich(8:1), lean(18:1), stochiometric(15:1), Best econ(16:1), best power(12.5:1)

6 metering systems

main metering

idling syetem

acceleration

mixture control

idle cut off

economizer/power enrichment

3 types of mixture control

backsuction mix

variable orriface

automatic

Advantagges of pressure carburetor

better vaporization

lowers vaporization ice

eliminates float

air metering forces

impact air+venturi air

Fuel metering forces

unmetered and metered fuel pressure

Idle cut off operation

Equalize pressures in chamber A+B

ADI

Anti Detonation Injection

ADI purpose

allows for engine to produce more power at takeoff by leaning mixture

cools cylinders

RSA fuel injection system advantages

increases horsepower output of engine cylinders

each cylinder has seperate fuel nozzle, better distribution

2 types of RSA fuel injection systems

direct:timed spurts

continuous: deliveres fuel continuously(better atomization)

Constant head spring function

keeps ball of seat during idle

constant effort spring function

allows for smooth transition from idle to power

Flow divider

RSA fuel injection system, divides flow of fuel

Teledyne continental fuel injection method of distributing fuel

Fuel manifold valve

what is added to jet fuels to inhibit microbial growth and lower freezing temp

PRIST

positive displacement pump types

vane type

gear type

G-rotor

what does FCU control

fuel flow

engine acceleration

engine deceleration

engine driven accesory meters fuel

hydromechanically

electrically

hydropneumatically

hydromechanical fcu sections

fuel metering section

computing section

Electronic FCU uses

Supervisory EEC

FADEC

atomizing nozzles

simplex,duplex,spill type,variable port nozzle, air spray nozzle, Lubbock

vaporizing nozzles

Cane shaped

T-shaped

fuel storage+distribution systems

Gravity feed systems:fuel pressure provided by weight of fuel

pressure feed systems:boost pumps

cross feed systems: transfers fuels betwixt tanks

fuel tank types

welded/riveted tank

composite tank

wet wings

bladder tank

common guidelines for fuel lines

route seperate from other systems

route below electrical

support lines to relieve stress

avoid sharp bends

Strainers and filters are located where

lowest point of fuel tank

2 types of positive displacement pumps

variable displacement piston pump

diaphram pump

auxilary fuel pumps

manual

centrifugal

pulsating electric

auxilary fuel pumps can use bypass or check valves. when would you use either?

bypass=installed in series. check vale: installed in series

5 parts of fuel system

tank

fuel selector

strainer/filter

primer

carb

engine driven pump purpose

provide positive pressure on fuel delivered to fuel metering device

Auxilary fuel pump purpose

provide fuel pressure for starting, backup, or crossfeed

variable displacement pump purpose

output changes to suit demands placed on it

positive displacement pump purpose

moves specific amount of fluid each time pump is actuated

why do you use fuel strainers

to strain contaminants out of fuel

what is the float used for in the bowl

to seat needle, controling fuel level within bowl

main metering system

controls flow of fuel above idle

idling system

controls flow of fuel at idle

acceleration system

supplies extra fuel for sudden throttle movements

idle cut off system

allows for safe shut off of engine

power enrichment/ economizer system

enrichens or leans mixture