Simple Carburettor Fuel System for a Piston Engine … 5...Simple Carburettor Fuel System for a...
Transcript of Simple Carburettor Fuel System for a Piston Engine … 5...Simple Carburettor Fuel System for a...
Simple Carburettor Fuel System for a Piston Engine
And how it works
Tank
PISTON ENGINE – Carburettor Fuel System
ExhaustInlet
Tank Cavity
Filler Cap
Filler Neck
E F1/2
FUEL
FUEL LEVEL
SENSOR
COCKPIT FUEL
GAUGE
PISTON ENGINE – Carburettor Fuel System - Tanks
PISTON ENGINE – Carburettor Fuel System - Tanks
E F1/2
FUEL
E F1/2
FUEL
WHERE ARE THE FUEL TANKS IN AIRCRAFT?
IN THE OTHERWISE EMPTY WING SECTIONS
CI30 HERCULES
PISTON ENGINE – Carburettor Fuel System - Aircraft Tanks
Tank
PISTON ENGINE – Carburettor Fuel System
Cockpit Gauge
Pump
ExhaustInlet
One-way Inlet Valve
One-way Outlet Valve
Diaphragm
Driving Cam
PISTON ENGINE – Mechanical Diaphragm Pump
One-way Inlet Valve
One-way Outlet Valve
Solenoid Windings
Switch Mechanism
Diaphragm
Magnetic Plate
PISTON ENGINE – Solenoid Diaphragm Pump
FLOW OUT
‘SPUR’ GEARS
PUMP FLOW AND RESTRICTION TO FLOW IN CONTROLLER CAUSES PRESSURE TO INCREASE
Flow Controller
PISTON ENGINE – Gear Type Pump
Air Filter
Tank
PISTON ENGINE – Carburettor Fuel System
Cockpit Gauge
Pump
Carburettor
ExhaustInlet
Air and Dirt
Clean Air
Filter element – corrugated breathable paper
Dirt trapped
by
Filter element
Basic Air Filter OperationPISTON ENGINE – Air Filter
Air Filter
Tank
PISTON ENGINE – Carburettor Fuel System
Cockpit Gauge
Pump
Carburettor
ExhaustInlet
We are now going to look at how the carburettor controls the flow to the engine
THE FLOAT CHAMBER
This is done by the: -
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
FLOAT CHAMBER
NEEDLE VALVE AIR VENTVENTURI
FUEL FEED
FUEL NOZZLE
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
FLOAT
FUEL LEVEL
AIR IS SUCKED THROUGH VENTURI BY…..
A PISTON MOVING DOWN ON INDUCTION STROKE
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
MOVING AIR HAS LOWER PRESSURE
FUEL FLOWA
IR F
LOW
AIR
FLO
W
THE LOWER AIR PRESSURE PULLS FUEL THROUGH THE JET
AIR/FUEL MIXTURE
FLOWS TOENGINE
FUEL LEVEL DROPS
PULLING AIR INTO FLOAT CHAMBER
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
FUEL LEVEL DROPS
FUEL LEVEL DROPPING LOWERS FLOAT
AND ALLOWS FUEL TO ENTER FLOAT CHAMBER FROM PUMP
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
FUEL LEVEL DROPS
FUEL LEVEL RISING FORCES THE NEEDLE VALVE CLOSED
FUEL LEVEL DROPPING LOWERS FLOAT
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
FUEL IS PULLED OUT OF THE FLOAT CHAMBER
ONLY WHEN ONE OF THE PISTONS IS ON THE INDUCTION STROKE
FUEL LEVEL RISING FORCES THE NEEDLE VALVE CLOSED
We now need to look at controlling the air/fuel mixture flowing into the engine
THE THROTTLE
Controlling the air/fuel mixture means controlling the engine
The carburettor part which controls the flow is….
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
LINK TO THROTTLE
LEVER/PEDAL
THROTTLE VALVE
VALVE SPINDLE
VALVE DISC
CARB.
THROTTLE VALVE
AIR FILTER
ENGINE
VENTURIFUEL AND AIR IS MIXED DUE TO LOWERED AIR
PRESSURE
CONTROLS MIXTURE FLOW TO
ENGINE
INLET MANIFOLD
ENGINE PULLS AIR IN DURING
INDUCTION STROKE
AND FLOW RESTRICTION THROUGH THROTTLE VALVE CAUSED BY SUCTION FROM ENGINE
BETWEEN THROTTLE VALVE AND ENGINE IS A PARTIAL VACUUM
THE INLET MANIFOLD VACUUM CAN BE USED TO HELP APPLY
THE BRAKES – CALLED ‘POWER-ASSISTING’
EXHAUSTMANIFOLD
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
THROTTLE VALVE
THIS WOULD BE A HIGH THROTTLE SETTING OR ‘FULL –POWER’
OPEN THROTTLE ALLOWS VENTURI TO WORK AT MAXIMUM EFFICIENCY
LOW THROTTLE SETTING - CALLED ‘IDLE’ OR ‘TICK-OVER’
ALMOST CLOSED THROTTLE MEANS THE VENTURI DOES NOT WORK VERY WELL
LOW AIR FLOW MEANS VERY LITTLE OR NO FUEL/AIR MIXING IN THE VENTURI
SO AN ALTERNATIVE AND EFFECTIVE VENTURI NEEDS TO BE FOUND
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
T CONTROLS FUEL FLOW
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
LOW THROTTLE SETTING - CALLED ‘IDLE’ OR ‘TICK-OVER’
EDGE GAPS BECOME THE VENTURI FOR THE LOW AIR FLOW
AT IDLE - SLOW RUNNING JET
BALANCED AIR PRESSURE AT THE MAIN JET
NEXT IS….
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
THE AIR FILTER CAN ALSO CAUSE RESTRICTION TO AIR FLOW
THIS WOULD CREATE A PRESSURE DIFFERENCE BETWEEN:-
HERE AND HERE
AND THEREFORE A SLIGHT VACUUM BEFORE CARB
FLOAT CHAMBER VENT
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
EQUALISING THE PRESSURE AT LOW SPEED
THEREFORE PREVENTING TOO MUCH FUEL MIXING WITH THE AIR
AND THE FLOAT CHAMBER IS CONNECTED TO THE CARB AIR INTAKE
SO THE VENT TO THE FLOAT CHAMBER IS CLOSED OFF
FLOAT CHAMBER VENT
MORE EFFICIENT MIXING OF AIR AND FUEL
NEXT….
MORE EFFICIENT MIXING OF AIR AND FUEL
IS ACHIEVED BY FITTING A DIFFUSER TUBE
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
HERE, ABOVE THE MAIN JET
LET’S TAKE A CLOSER LOOK AT THIS AREA
IDLE SETTING FUEL
SUPPLIED VIA IDLE JETOPEN THROTTLE
IDLE JET STOPS WORKING
CRUISE SETTINGHIGH POWER SETTING
AIR INLET
DIFFUSER TUBE
INCREASED FLOW OF MIXED AIR/FUEL
FUEL FEED FROM FLOAT CHAMBER
MAIN JET
AIR MIXES WITH FUEL
AIR/FUEL MIXING IN DIFFUSER TUBE
FUEL LEVEL IN FLOAT CHAMBER
SIMPLIFIED PISTON ENGINE FUEL SYSTEM
AUTOMATIC MIXTURE CONTROL
NEXT..….
This is required to take into account that at higher altitude there is less air, so therefore less fuel is required.
It is called a pressure bellows or pressure capsule.
This change in fuel flow is controlled by a device that can sense the change in air pressure.
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
FIXED END
MOVING END
NEEDLE VALVE
CAPSULE EXPANDS IN LOWER PRESSURES AND CONTRACTS IN HIGHER PRESSURES
PRESSURE CAPSULE
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
AT LOW ALTITUDE – HIGHER ATMOSPHERIC PRESSURE
CAPSULE CONTRACTED
HIGH FUEL FLOW
AT HIGH ALTITUDE – LOWER ATMOSPHERIC PRESSURE
CAPSULE EXPANDS
SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM
AT HIGH ALTITUDE – LOWER ATMOSPHERIC PRESSURE
CAPSULE EXPANDS
CLOSING FUEL ORIFICEE AND REDUCING FUEL FLOW
AUTOMATIC MIXTURE CONTROL
NEXT..….
This is required to take into account that at higher altitude there is less air, so therefore less fuel is required.
It is called a pressure bellows or pressure capsule.
This change in fuel flow is controlled by a device that can sense the change in air pressure.
BatteryFuel Tank
Pump
Warm Up Regulator
Fuel Accumulator
Ignition Switch
Filter
Primary Pressure
Valve
Air Sensor Plate
Mixture Control Unit (Fuel Distributor Valve)
Auxiliary Air Device
Cold Start ValveIdle Speed
Adjuster
Fuel Injector
Throttle Valve
Engine Temp Sensor
Safety Relay
Air Inlet
High Pressure FuelLow Pressure Fuel
Supply Pressure FuelServo Pressure Fuel
Electrical Signal
Legend
PISTON ENGINE – Hydro-Mechanical Fuel Injection System
(from Air Filter)
Air Filter
PISTON ENGINE – Electronic Fuel Injection System
Engine ECU
TankPump
Cockpit Gauge
Pressure Regulator
Injection Control
Unit
Engine TempEngine RPM/TDCExhaust TempThrottle PositionForward SpeedAir Temps – Inlet & Ambient
Fuel Injectors
‘Common Rail’
Throttle
Any Questions?