IC Engine Fuel Feed Systems

IC Engine Systems

• Fuel systems are a key component
• Cooling Systems
• Lubricating System
• Governing System
• Ignition System

Fuel Systems

• Fuel is supplied to the engine based on its requirements via a specific system
• A tank in the vehicle holds the fuel
• Is fed by different ways to either the carburetor or the injection pump

Fuel Feed Systems

• The system uses in engine manifold, vacuum to draw fuel from tank to autovac tank
• There are three types:
  • Gravity feed system
    • The fuel tank is above the engine
    • Fuel flows to the carburetor or injection pump by gravity
  • Vacuum feed system
    • The system uses vacuum from the engine manifold to draw fuel from the tank to the autovac tank
    • Fuel feeds to the carburetor by gravity from the vacuum tank
    • Operates under atmospheric pressure
  • Pressure feed system
    • Fuel is fed to the carburetor under pressure
    • Fuel can be fed via a mechanical or electrical pump

Pump System

• Pumps petrol to the carburetor through a pipe
• Can be mechanical or electrical

Fuel Injection System

• Fuel is atomized through a nozzle
• Delivered into an air stream
• Separate injectors for each cylinder are used

Petrol Engine Fuel System Components

• Fuel tank holds the fuel
• Fuel filter removes contaminants
• Fuel pump delivers fuel
• Carburetor mixes air and fuel
• Air cleaner filters intake air
• Fuel gauge measures fuel level

Simple Carburetor

• It mixes air and fuel for combustion
• Contains these main parts:
  • Float chamber, fuel jet, venturi, nozzle, throttle valve
• A float keeps the fuel level consistent
• The fuel is slightly below the nozzle to precent spillage once the engine stops
• The float chamber vent equalizes pressure

Simple Carburetor Function

• A fuel jet meters fuel flow to the venturi nozzle
• The venturi creates a restriction in the air passage
• Air velocity increases and pressure decreases at venturi, creating suction
• When using the nozzle, fuel vaporizes in the air stream
• The mixture then goes through the inlet manifold to the engine cylinder

Mechanical Fuel Pump

• Operates using a diaphragm
• The diaphragm consists of synthetic rubber and high grade cotton
• Valve consist of bakelite to reduce weight and inertia streses
• Shaft driven by an eccentric cam
• Eccentric uses a rocker arm to move the diaphragm vertically
• Downward diaphragm movement allows fuel to enter chamber via strainer through the inlet valve
• Upward diaphragm movement closes inlet valve and opens the outlet valve to allow fuel to carburetor

Mixture Strength Requirements

• Mixture strength depends of engine speed, temperature, and load
• A rich mixture (9:1 air:fuel) is required to start the engine
  • Fuel won't vaporize properly
• A rich mixture (12:1 air:fuel) is required at idling condition
  • Is used to overcome frictional power and reach normal temperature
• 14.6:1 air:fuel ratio gives complete fuel combustion and known as stoichiometric mixture
• Mid Speed (35-105 km/hr), mixture leans our at 15:1
• High Speed (120-150 km/hr), the mixture is again enriched about 13:1 with the wide open throttle
• Cruising speed/part throttle, a lean mixture is required (15:1 air:fuel)
• Requires a rich mixture for full throttle (12:1 air:fuel)

Diesel Engine Fuel System

• Diesel engine system components:
  • Fuel tank
  • Fuel feed pump
  • Filter
  • Injection pump
  • Injector

Diesel Engine Fuel System components

• The fuel tank is made of steel, usually rectangular or barrel-shaped
• Fuel filter that removes containments
• The feed pump draws fuel from the tank to the injector
• The fuel injection pump meters fuel to the engine cylinder
• The fuel injector sprays the high pressure fuel into the engine cylinder

Fuel Feed Pump

• The cam rotating moves the plunger upwards
• The upward movement action closes the inlet valve forcing fuel through the outlet valve
• The plunger then moves downward making the low pressure, then allows fuel into the chamber through the inlet valve

Fuel Injection Pump Componets

• Has a delivery valve
• Along with spill port
• Spring
• Roller tappet

Fuel Injection Pump Operation

• Comprises a plunger which reciprocates in a barrel
• Cylindrical barrel with 2 diametrically opposite ports (inlet and spill)
• The upper plunger contains a vertical groove
• A rack and tested segment turn the plunger
• When the plunger moves upwards, both valves close allowing fuel to enter the injector at high pressure
• As soon as spill port uncovers, the fuel passes through the vertical grove to the spill port
• Quantity of fuel delivered is therefore controlled

Fuel Injector Components

• The fuel injection process occurs through this device
• Adjusting screw
• Locking nut
• Leak Off
• Fuel Inlet
• Spindle
• Cap
• Valve
• Nozzle Body

Fuel Injector Operation

• This devices main part is the nozzle and the nozzle holder
• Spring loaded spindle presses against the nozzle valve
• Provides pressure for fuel injection
• Then spray of atomized fuel is fed into combustion chamber
• The fuel is then directed down to space below the nozzle valve
• The valve is then lifted up
• Any leakage from this process goes of through the leak of pipe

Injection Nozzles

• Used to properly inject atomized fuel into the cylinder
• There are Two types:
  • Hole type
    • Used in open combustion engines
  • Pintle type
    • Used in pre-combustion and special swirl chambers
    • Has extension which produces a hollow cone spray

Fuel Filters

• Includes a Primary Filter as well as a Secondary Filter

Primary Fuel Filter

• This filter allows the fuel to flow around the conical diffuser and accelerates the sediment chamber
• This action allows all impurities to be drained off periodically
• And clean oil passes to the outlet of the filter

Secondary Fuel Filter

• Contains resin-impregnated paper is used as filtering element
• This will also fliter 95% of abrasive particles
• The filter element retains solid and abrasive particles of water dropplets
• The droplets end of forming larger from the resin-impregnated element
• Heaviers droplets settle down in in the chamber

Ignition System of Sl Engine

• Needs to provide electrical energy
• Needs to boost low voltage from the source
• Needs a timing and distribution of high voltage to each spark plug
• The two types of ingition systems are:
  • Magneto ignition
  • Battery ignition

Battery Ignition System

• System has a primary and secondary circuit
• The primary circuits are battery, ammeter, ignition switch, primart and the breaker points
• Secondary circuits constists of secondary coil, distributor and the spark plug
• One primary winding is connected to positive end terminal and opposite side is contact breaker
• Cam operates contact breaker point
• Condenser connected parallel to the contact beaker

Battery Ignition System Operation (Coil)

• Closing point will allow current to flow to primary and then magnetize the core
• Opening point will break down the current and charges condenser to a higher voltage
• Condenser discharges with the battery reversing
• The collapse produces a high voltage which distributed out using the rotary distributer

Battery Ignition Advantages

• Low cost, provides better sparks and it's a simple design
• Has a low maintenance cost

Battery Ignition Limitations

• Can't start when battery is low, not compatible with airplane, and the breaker points are exposed to wear

Cooling Systems

• Controls temperature in the engine
• Dissapates excess heat from the cylinder wall
• Resists burning of lubricant to prevent damage

Cooling Methods

• There are two kinds:
  • Air Cooling
  • Water Cooling

Air Cooling

• Airflow past heated metal surface removes heat
• Relies heat transfer by conduction and convection
• Factors affecting heat dissipation include:
  • Air contact with metal surface
  • Air flow rate
  • Temperature Gradient
  • Thermal gradient

Air Cooling Fin

• Fins increase the surface are of air cooling cylinder and cylinder head

Air Cooling Advantages

• Lightweight due to lack of radiator or coolant system
• Operates in extreme cold
• Easy to maintain
• Easier to warm up

Air Cooling Disadvantages

• Uneven Cooling around an engine
• Least efficient cooling because of lower gradient of transfer
• Uses fan leading to engine power loose
• Air Cool engines are noisy

Water Cooling system

• Uses water jacket surrounding cylinder
• Dissipates heat from cylinder wall to water
• Hot water moved to radiator, and antifreeze is added coolant

Two Types of Water Cooling

• Thermosyphon (Gravity circulation)
  • Works due to the difference of hot and cold liquid
• Forced circulation System
  • Uses a water pump to flow the liquid

Thermo Syphon Details

• Relies hot water density differences as opposed to cold water
• The water heated in the jackets flows to the upper tank
• Cold water flows to engine jacket, and process is repeated

Thermo Syphon: From Upper Tank

• The water goes down and passes through the radiator
• Then air is drawn by shaft
• Air blast from the cylinder drives the cool air

Thermo Syphon

• Requires radiator and coolant to flow under gravity and function
• Will start working effectively when the engine is hot
• Cant be used on heavy engines when heat transfer is high

Components of a Thermostat Cooling System

-Water Tank and Jacket uses themostat

• Needs a pump for predefined temp as the themostat is used during the cold to start engine
• The coolant can be controlled through radiator

Stats and Coolants

• The Stats operate in the hose connection (which is the temp based valve)
• And it makes hard to make sure the circuit operates in the low temp state

Thermostat

• Keeps the cooling temperature steady
• Types include bellows and wax-based thermostats.

Air Cool

Bellows Thermostat

• Contains copper tubes with volatile alcohol liquid
• Will have expansion which opens the release valve with pump

Bellows Thermostat With Engine Activated

• Releases the liquid when heat rises
• Opens with high pressure
• Releases cooling as the engine operates

Wax Thermostat

• Designed to coolant and will transmit high copper through release valve
• Heat will rise upwards when the engine turns up

Radiators function

• Close contact and have a high transfer rate
• The parts include overflow pipe, lower and upper tanks
• Hot water flows to radiator and flows through to be picked up by cold air

Two type of Radiators are

• Tubular type
• And Cellular Type
• Two have types each can differ in space of travel with coolant, air, and tubes

Temp Indicators (coolant in engine)

• Shows how coolant is measured through panel temp

There are two types of Temp Indicators

• Electrical operated systems
• Mechanism operated systems

Electrically operated

• Reduces electrical resistance and has an electrical element
• Elements cause increases flow to the coil
• The coil moves and the temp can be read off a gauge

Mechanically Operated Types

• Sealed bulb fitted to connect it to voltaile liqud

IC Lubication (engines)

• Minimizes power loss
• Reduces wear and tear
• Cleans waste products
• prevents gaps from forming
• Minimizes noise

Governing Types of methods

• Splash Lubrication
• Pressure Lubrication
• Petroil Lubrication

Splash Lubication process

• Contains lubrication for the parts by a dipper on the crankshaft
• The pockets collect the splashing oil and bearing surfaces will be covered by holes

Pressure Lubication Process

• A process that makes precise where the pump distributes key oils
• Then pump in filtered until oil can b re-oiled
• This makes the viscosity as the system becomes more consistent

Petroil Lubrication System

• Used in scooters motorcycle and any similar that does not include air
• Will contain a certain proportion to give the engine the desired performance