piston engines part 4 piston engine operations (oil and fuel pumps)

PISTON ENGINES

Part 4

Piston Engine Operations(Oil and Fuel Pumps)

IntroductionOil Systems

Lubrication is used between 2 sliding surfaces to overcoming friction,

and therefore prevent or reduce component wear.

The properties demanded from a lubricantvary considerably with the particular application.

Lubricant for a bicycle is not suitable for a steam engine;a lubricating oil for any engine

should be of a suitable viscosity for maximum loadsand also retain this viscosity

over the full range of engine temperature.

Engine Block

SUMP

Oil SystemsThe ‘Wet Sump’ System

Common to most vehicles

FilterPump

Oil is stored in the sump and pulled out,through a strainer, by a pump.

The oil then passes through a filterto ensure it is clean etc.

It then passes into the engine,returning excess oil to the sump.

Engine Block

SUMP

Oil Systems

FilterPump

High Performance/Rally vehiclesand Aircraft

Tank

The ‘Dry Sump’ System

Oil is stored in a separate tank,

but still pulled by pump through a strainer,

and passed through a filter into the engine,

returning excess oil to the sump.

Engine Block

SUMP

Oil Systems

FilterPump


Tank Scavenge Pump

The ‘Dry Sump’ System

But the oil is then taken out of the sump by a scavenge pump &

returned to the tank,hence the name ‘Dry

Sump’This gives protection against oil loss in cars;and helps maintain correct levels of lubrication in aircraft.

Oil flowing from the pump is passed through the filter,

and then forced along internal passagewaysto the areas needing lubrication.

The oil lubricatesthe ball and roller bearings,

gear teeth, piston rings,cylinder walls and

other moving parts, then drains to the sump.

Let’s take a closer look here.

Oil Distribution

Sump (Oil Tank)

Pump Filter

The illustration shows the main bearing locations for: -Crankshaft support bearings.

Conrod to crankshaft bearings (big-ends) for each piston.The gudgeon pins.

In addition (not illustrated) areother bearings required to provide smooth running of other componentssuch as the cam shaft, water pump drive shaft,oil pump drive shaft etc.

Let’s take a closer look here.

Oil DistributionBearing Lubrication

Flywheel

Front Support Bearing

Rear Support BearingsSupport

Bearings

Gudgeon Pin

Crankshaft

Con Rod

A 4 CYLINDER ENGINE CRANKSHAFT

1

2 3

4

Con Rod Big End


Crankshaft

Shell Bearings

The illustration shows a cross sectional view of a plain bearing.

The plain bearings are made up of two distinct halves, called ‘shell’ bearings,

and the big-ends are fixed to prevent rotation in the conrod.

Con Rod Big End

Oil Splash

Oil Splash

Oil Splash

Oil Splash


Crankshaft

Oil Distribution

Groove

Internal Oil Feed

Lubricating Oil Film

Shell Bearings

The oil is fed into distribution grooves cut in the shells, spreading an even thin film of oil

between the bearing and crankshaft surfaces.

Excess oil is then returned to the sump.

Maintaining oil pressure is critical.In most cars a simple indicator light is illuminated.

In performance cars and aircraft, a gauge is usual to display actual pressure.

To prevent mechanical damage regular servicing is necessary.

Oil specification is found invehicle Owner Handbooksand Service Manuals, and aircraft Maintenance Manuals.

Engine life in vehicles ismonitored as miles travelled, while in aircraft it is as hours or cycles flown. Front

Support Bearing

Rear Support BearingsSupport

Bearings

Gudgeon Pin

Con Rod

1

2 3

4


Oil PumpsInternal Gear Type Pump

Rotating Parts

Driving Gear

Pump Body

This pump consists of two gears, one inside the other.The smaller centre gear is the driving gear, powered by the engine.

The larger outer gear (‘idler’ gear) is driven by the inner gearvia the meshing of the gear teeth or ‘lobes’.

Pump Assembly (end plate removed)

Driven Gear

Oil PumpsInternal Gear Type Pump

Pump Assembly (end plate removed)

Rotating Parts

Driving Gear

Driven Gear

Pump Body

Yellow = Inlet Flow

Red = Outlet Flow

‘Kidney’ Ports

The inlet and outlet ports are a known as kidney ports.Fluid is pulled in and forced out through these ports.

As the gears rotate,fluid is pulled in and forced out.

Kidney Ports

Fuel Pumps

Where are the fuel tanks in most aircraft ?

Aircraft fuel tanks are formed by the structure of the wing.Fuel can be transferred from tank to tank

to help balance the aircraft in flight.This allows trimming the aircraft efficiently

without using aerodynamic forceswhich cause drag.

The filler connection is usually underneath the wingand is a self sealing device to prevent spillage.

It is also hidden away behind an access hatch to maintain aerodynamic smoothness.

Fuel level is measured via a level sensor and indicated on the flight deck by the fuel gauge.

The tank is filled from either a vehicle born bowser

or underground storage tanks, as with vehicle filling stations.

Tank

E F1/2FUEL

Fuel Pumps

Tank Cavity

Filler Cap

Filler Neck

Fuel Level Sensor

Cockpit Fuel Gauge

But to get the fuelto the engines,some form of

pump is needed.FuelPump

Mechanical Diaphragm PumpOne-way Inlet Valve

Diaphragm

One-way Outlet Valve

Driving Cam

This is a Positive Displacement pump,which means when the pump stops, flow is prevented.

This pump consists of a flexible diaphragm, which is moved up by spring force

and down by an engine driven cam, and two one-way valves.

Spring

Solenoid Diaphragm PumpOne-way Inlet Valve

One-way Outlet Valve

Diaphragm

Solenoid Windings

Magnetic Plate

Switch Mechanism

Another Positive Displacement pump.

Consisting of a flexible diaphragm, moved up and down by an electro-magnetic force.

In this pump, the piston is moved up and down by a magnetic field generated by

the electrically powered coil underneath.

Fuel PumpsThe Gear Type Pump

‘SPUR’ GEARS

BODY

The Gear Type Pump is the most favoured pump design,because it consists of just a few easy to produce working parts.

Intermeshing straight cut spur gears rotating in a close fitting body.

FLOW OUT


‘SPUR’ GEARS

Flow Controller

As the gears rotate the fluid is carriedbetween the gear teeth.

A control valve is set to limit the absolute pressure in the system,

(around 450 psi) to protect against system damage.

FLOW OUT


‘SPUR’ GEARS

Pump flow restrictionin the controllercauses pressureto increase

Flow Controller

Without the flow controller, the pump would provide a flow,

but at no pressure. Pressure is only achieved

because the flow control system works on flow restrictions

which causes the pressure to rise.

Carburettor

Air FilterFuel is pumped to the carburettor

(which we will examine later).

The carburettor controls the mixing of air and atomized fuel,but the air must be filtered to prevent any

damage or blockage in the fuel system or engine.

Tank

E F1/2FUEL

FuelPump

Air Filter

Inlet Exhaust

We will look at this area

Air Filter

Air FilterA paper based element bonded into a rubberized material,

is concertinaed to get the greatest surface area.

Air with contaminants passes through the filter, which catches the contaminants and leaves the air cleaner.

Filtration rate is in Microns (1 micron = 0.000,001 metre). So a 30 micron filter

stops particles of 30 microns or more.

Filter of corrugated paper

Air and Dirt

Dirt trapped by filter

Clean Air

Check of Understanding

Where would a Dry Sump Oil Systembe most commonly used?

Only inHigh Performance/Rally vehicles

Most vehicles

Only in Aircraft


What differentiates a Dry Sump systemfrom a Wet Sump system?

A Scavenger Pump

A Diaphragm Pump

A Positive Displacement Pump

An Internal Gear Type Pump


Bearings in a crankshaft are made up of two distinct parts.

What are these called?

Ball Bearings

Dry Bearings

Shell Bearings

Roller Bearings


Where would you find the oil specificationsfor an aircraft?

The aircraft log

The service manual

The operating manual

The maintenance manual


Within an internal gear-type pump there are two gears.

Which one is driven by the engine?

The Driven Gear

The Idler Gear

The Outer Gear

The Driving Gear


Which of these pumps has a flexible diaphragm moved up and down

by an electro-magnetic force?

A Solenoid Diaphragm Pump

A Gear Type Pump

A Scavenger Pump

A Mechanical Diaphragm Pump


Which is the most favoured type of pump design?

Meshing Gear Pump

Solenoid Diaphragm Pump

Mechanical Diaphragm Pump

Gear Type Pump


Without the flow controller in a gear-type pump,

What flow would the pump supply?

No flow at all

A flow at no pressure

A flow at high pressure

A flow at low pressure


What is a Micron?


of a metre1

100,000

11,000,000

of a metre

110,000

of a metre

1

1,000of a metre

PISTON ENGINES

End of Presentation

piston engines part 4 piston engine operations (oil and fuel pumps)

Documents

excess oil

film of oil

oil pressure

lubricating oil

oil loss

vehicles filter pump

dry sump system oil

oil pump drive shaft