PISTON ENGINE PROPULSION Chapter 5 Fuel Systems 1933 Alvis Engine 2014 Hyundai Engine Simple Carburettor Fuel System for a Piston Engine

PISTON ENGINE – Carburettor Fuel System Tank ExhaustInlet What do we need to make the engine run? FUEL So we need a container to hold the fuel. A Fuel Tank

PISTON ENGINE – Carburettor Fuel System - Tanks Tank Cavity Filler Cap Filler Neck EF 1/2 FUEL FUEL LEVEL SENSOR COCKPIT FUEL GAUGE

EF 1/2 FUEL EF 1/2 FUEL PISTON ENGINE – Carburettor Fuel System - Tanks

PISTON ENGINE – Carburettor Fuel System – Aircraft Tanks WHERE ARE THE FUEL TANKS IN AIRCRAFT? IN THE OTHERWISE EMPTY WING SECTIONS CI30 HERCULES

PISTON ENGINE – Carburettor Fuel System Tank Cockpit Gauge E F 1/2 Pump ExhaustInlet

PISTON ENGINE – Mechanical Diaphragm Pump One-way Inlet Valve One-way Outlet Valve Diaphragm Driving Cam

PISTON ENGINE – Solenoid Diaphragm Pump One-way Inlet Valve One-way Outlet Valve Solenoid Windings Switch Mechanism Diaphragm Magnetic Plate

PISTON ENGINE – Gear Type Pump FLOW OUT ‘SPUR’ GEARS PUMP FLOW AND RESTRICTION TO FLOW IN CONTROLLER CAUSES PRESSURE TO INCREASE Flow Controller

PISTON ENGINE – Carburettor Fuel System Air Filter Tank Cockpit Gauge E F 1/2 Pump Carburettor ExhaustInlet

PISTON ENGINE – Air Filter - Basic Air Filter Operation Air and Dirt Filter element – corrugated breathable paper

PISTON ENGINE – Air Filter - Basic Air Filter Operation Dirt trapped by Filter element Clean Air

PISTON ENGINE – Carburettor Fuel System Air Filter Tank Cockpit Gauge E F 1/2 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: - PISTON ENGINE – Carburettor Fuel System

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FLOAT CHAMBER NEEDLE VALVEAIR VENT VENTURI FUEL FEED FUEL NOZZLEFLOAT FUEL LEVEL

SIMPLIFIED PISTON ENGINE FUEL SYSTEM AIR IS SUCKED THROUGH VENTURI BY….. A PISTON MOVING DOWN ON INDUCTION STROKE MOVING AIR HAS LOWER PRESSURE FUEL FLOW AIR FLOW THE LOWER AIR PRESSURE PULLS FUEL THROUGH THE JET AIR/FUEL MIXTURE FLOWS TO ENGINE FUEL LEVEL DROPS

SIMPLIFIED PISTON ENGINE FUEL SYSTEM PULLING AIR INTO FLOAT CHAMBER FUEL LEVEL DROPS FUEL LEVEL DROPPING LOWERS FLOAT

SIMPLIFIED PISTON ENGINE FUEL SYSTEM AND ALLOWS FUEL TO ENTER FLOAT CHAMBER FROM PUMP 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

SIMPLIFIED PISTON ENGINE FUEL SYSTEM 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

SIMPLIFIED PISTON ENGINE FUEL SYSTEM CARB. THROTTLE VALVE AIR FILTER ENGINE VENTURI INLET MANIFOLD AND FLOW RESTRICTION THROUGH THROTTLE VALVE CAUSED BY SUCTION FROM ENGINE BETWEEN THROTTLE VALVE AND ENGINE IS A PARTIAL VACUUM EXHAUST MANIFOLD

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FUEL AND AIR IS MIXED DUE TO LOWERED AIR PRESSURE CONTROLS MIXTURE FLOW TO ENGINE ENGINE PULLS AIR IN DURING INDUCTION STROKE CARB. AIR FILTER ENGINE INLET MANIFOLD AND FLOW RESTRICTION THROUGH THROTTLE VALVE CAUSED BY SUCTION FROM ENGINE BETWEEN THROTTLE VALVE AND ENGINE IS A PARTIAL VACUUM EXHAUST MANIFOLD

SIMPLIFIED PISTON ENGINE FUEL SYSTEM THE INLET MANIFOLD VACUUM CAN BE USED TO HELP APPLY THE BRAKES – CALLED ‘POWER-ASSISTING’ CARB. AIR FILTER ENGINE INLET MANIFOLD AND FLOW RESTRICTION THROUGH THROTTLE VALVE CAUSED BY SUCTION FROM ENGINE BETWEEN THROTTLE VALVE AND ENGINE IS A PARTIAL VACUUM EXHAUST MANIFOLD

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

SIMPLIFIED PISTON ENGINE FUEL SYSTEM 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

T CONTROLS FUEL FLOW LOW THROTTLE SETTING - CALLED ‘IDLE’ OR ‘TICK-OVER’ EDGE GAPS BECOME THE VENTURI FOR THE LOW AIR FLOW AT IDLE - SLOW RUNNING JET

SIMPLIFIED PISTON ENGINE FUEL SYSTEM BALANCED AIR PRESSURE AT THE MAIN JET NEXT IS….

SIMPLIFIED PISTON ENGINE FUEL SYSTEM THE AIR FILTER CAN ALSO CAUSE RESTRICTION TO AIR FLOW THIS WOULD CREATE A PRESSURE DIFFERENCE BETWEEN:- HEREAND HERE AND THEREFORE A SLIGHT VACUUM BEFORE CARB FLOAT CHAMBER VENT

SIMPLIFIED 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

SIMPLIFIED PISTON ENGINE FUEL SYSTEM MORE EFFICIENT MIXING OF AIR AND FUEL NEXT….

SIMPLIFIED PISTON ENGINE FUEL SYSTEM MORE EFFICIENT MIXING OF AIR AND FUEL IS ACHIEVED BY FITTING A DIFFUSER TUBE HERE, ABOVE THE MAIN JET LET’S TAKE A CLOSER LOOK AT THIS AREA

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FUEL FEED FROM FLOAT CHAMBER MAIN JET AIR/FUEL MIXING IN DIFFUSER TUBE FUEL LEVEL IN FLOAT CHAMBER IDLE SETTING FUEL SUPPLIED VIA IDLE JET DIFFUSER TUBE

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FUEL FEED FROM FLOAT CHAMBER MAIN JET AIR/FUEL MIXING IN DIFFUSER TUBE FUEL LEVEL IN FLOAT CHAMBER OPEN THROTTLE IDLE JET STOPS WORKING AIR INLET DIFFUSER TUBE

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FUEL FEED FROM FLOAT CHAMBER MAIN JET AIR/FUEL MIXING IN DIFFUSER TUBE FUEL LEVEL IN FLOAT CHAMBER AIR INLET DIFFUSER TUBE CRUISE SETTING AIR MIXES WITH FUEL

SIMPLIFIED PISTON ENGINE FUEL SYSTEM FUEL FEED FROM FLOAT CHAMBER MAIN JET AIR/FUEL MIXING IN DIFFUSER TUBE FUEL LEVEL IN FLOAT CHAMBER AIR INLET AIR MIXES WITH FUEL HIGH POWER SETTING DIFFUSER TUBE INCREASED FLOW OF MIXED AIR/FUEL

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 SYSTEM FIXED END MOVING END NEEDLE VALVE CAPSULE EXPANDS IN LOWER PRESSURES AND CONTRACTS IN HIGHER PRESSURES PRESSURE CAPSULE

SIMPLIFIED 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 SYSTEM AT HIGH ALTITUDE – LOWER ATMOSPHERIC PRESSURE CAPSULE EXPANDS CLOSING FUEL ORIFICE E AND REDUCING FUEL FLOW

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.

Battery Fuel 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 Valve Idle Speed Adjuster Fuel Injector Throttle Valve Engine Temp Sensor Safety Relay Air Inlet High Pressure Fuel Low Pressure Fuel Supply Pressure Fuel Servo Pressure Fuel Electrical Signal Legend (from Air Filter) SIMPLIFIED PISTON ENGINE FUEL SYSTEM

Air Filter Engine ECU Tank E F 1/2 Pump Cockpit Gauge Pressure Regulator Injection Control Unit Engine Temp Engine RPM/TDC Exhaust Temp Throttle Position Forward Speed Air Temps – Inlet & Ambient Fuel Injectors ‘Common Rail’ Throttle

SIMPLIFIED PISTON ENGINE FUEL SYSTEM Any Questions?

IDLE SETTING FUEL SUPPLIED VIA IDLE JET OPEN THROTTLE IDLE JET STOPS WORKING CRUISE SETTING HIGH 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