1. Piston Engine Operations
PISTON ENGINES
Part 4
Piston Engine Operations
(Oil and Fuel Pumps)

2. Introduction Oil Systems
Lubrication is used between 2 sliding surfaces
to overcoming friction,
and therefore prevent or reduce component wear.
The properties demanded from a lubricant
vary 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 loads
and also retain this viscosity
over the full range of engine temperature.

3. Oil Systems The ‘Wet Sump’ System Common to most vehicles
Engine Block
Pump
Filter
Common to most vehicles
Oil is stored in the sump and pulled out,
through a strainer, by a pump.
The oil then passes through a filter
to ensure it is clean etc.
It then passes into the engine,
returning excess oil to the sump.
SUMP

4. Oil Systems The ‘Dry Sump’ System High Performance/Rally vehicles
Engine Block
Pump
Filter
High Performance/Rally vehicles
and Aircraft
Tank
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.
SUMP

5. Oil Systems The ‘Dry Sump’ System High Performance/Rally vehicles
Engine Block
Pump
Filter
High Performance/Rally vehicles
and Aircraft
Tank
Scavenge Pump
But the oil is then
taken out of the sump
by a scavenge pump & returned to the tank,
hence the name ‘Dry Sump’
SUMP
This gives protection against oil loss in cars;
and helps maintain correct levels of lubrication in aircraft.

6. Oil Distribution Let’s take a closer look here.
Oil flowing from the pump
is passed through the filter,
and then forced along internal passageways
to the areas needing lubrication.
The oil lubricates
the 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.
Sump
(Oil Tank)
Pump
Filter

7. Oil Distribution Bearing Lubrication A 4 CYLINDER ENGINE CRANKSHAFT
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) are
other bearings required to
provide smooth running of
other components
such as the cam shaft,
water pump drive shaft,
oil pump drive shaft etc.
Let’s take a closer look here.
Flywheel
Con Rod 1 2 3 4
Gudgeon
Pin
Front
Support Bearing
Rear
Support Bearings
Support
Bearings
Crankshaft
A 4 CYLINDER ENGINE CRANKSHAFT

8. Oil Distribution Bearing Lubrication
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
Shell Bearings
Crankshaft

9. Oil Distribution Bearing Lubrication
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.
Oil Splash
Con Rod Big End
Shell Bearings
Oil Distribution Groove
Lubricating Oil Film
Crankshaft
Oil Splash
Internal
Oil Feed

10. Oil Distribution Bearing Lubrication
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 in
vehicle Owner Handbooks
and Service Manuals,
and aircraft Maintenance Manuals.
Engine life in vehicles is
monitored as miles travelled,
while in aircraft it is as hours
or cycles flown.
Front
Support Bearing
Rear
Support Bearings
Support
Bearings
Gudgeon
Pin
Con Rod 1 2 3 4

11. Oil Pumps Internal Gear Type Pump
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 gear
via the meshing of the gear teeth or ‘lobes’.
Pump Assembly
(end plate removed)
Pump Body
Driving Gear
Driven Gear
Rotating Parts

12. Oil Pumps Internal Gear Type Pump
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.
Pump Assembly
(end plate removed)
‘Kidney’ Ports
Pump Body
Driving Gear
Driven Gear
Kidney Ports
Yellow = Inlet Flow
Red =
Outlet Flow
Rotating Parts

13. 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 forces
which cause drag.

14. Fuel Pumps The filler connection is usually underneath the wing
and 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.
Filler Cap
Cockpit Fuel Gauge
Filler Neck E F
1/2
FUEL
But to get the fuel
to the engines,
some form of
pump is needed.
Tank
Fuel Level Sensor
Fuel
Pump
Tank Cavity

15. Mechanical Diaphragm Pump
One-way
Inlet Valve
One-way
Outlet Valve
Diaphragm
Spring
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.

16. Solenoid Diaphragm Pump
One-way
Inlet Valve
One-way
Outlet Valve
Diaphragm
Magnetic Plate
Solenoid Windings
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.

17. Fuel Pumps The Gear Type Pump The 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.

18. Fuel Pumps The Gear Type Pump As the gears rotate the fluid is carried
‘SPUR’ GEARS
Flow Controller
FLOW OUT
As the gears rotate the fluid is carried
between the gear teeth.
A control valve is set to limit
the absolute pressure in the system,
(around 450 psi)
to protect against system damage.

19. Fuel Pumps The Gear Type Pump Without the flow controller,
Pump flow restriction
in the controller
causes pressure
to increase
‘SPUR’ GEARS
Flow Controller
FLOW OUT
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.

20. Air Filter Fuel 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.
Air Filter
Carburettor
Inlet
Exhaust
We will look
at this area
Tank E F
1/2
FUEL
Fuel
Pump

21. Air Filter A 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.
Air Filter
Clean Air
Filter of corrugated
paper
Dirt trapped
by filter
Air and Dirt

22. Check of Understanding
Where would a Dry Sump Oil System
be most commonly used?
Most vehicles
High Performance/Rally vehicles
and Aircraft
Only in Aircraft
Only in
High Performance/Rally vehicles

23. Check of Understanding
What differentiates a Dry Sump system
from a Wet Sump system?
A Diaphragm Pump
An Internal Gear Type Pump
A Positive Displacement Pump
A Scavenger Pump

24. Check of Understanding
Bearings in a crankshaft
are made up of two distinct parts.
What are these called?
Dry Bearings
Roller Bearings
Shell Bearings
Ball Bearings

25. Check of Understanding
Where would you find the oil specifications
for an aircraft?
The service manual
The maintenance manual
The operating manual
The aircraft log

26. Check of Understanding
Within an internal gear-type pump
there are two gears.
Which one is driven by the engine?
The Idler Gear
The Driving Gear
The Outer Gear
The Driven Gear

27. Check of Understanding
Which of these pumps
has a flexible diaphragm moved up and down
by an electro-magnetic force?
A Gear Type Pump
A Mechanical Diaphragm Pump
A Scavenger Pump
A Solenoid Diaphragm Pump

28. Check of Understanding
Which is the most favoured type
of pump design?
Solenoid Diaphragm Pump
Gear Type Pump
Mechanical Diaphragm Pump
Meshing Gear Pump

29. Check of Understanding
Without the flow controller
in a gear-type pump,
What flow would the pump supply?
A flow at no pressure
A flow at low pressure
A flow at high pressure
No flow at all

30. Check of Understanding
What is a Micron? 1
1,000,000
of a metre
of a metre 1
100,000 1
10,000
of a metre 1
1,000
of a metre

31. PISTON ENGINES
End of Presentation