1. PISTON ENGINES
Part 3
Types of Piston Engine

2. Introduction Piston Engine Layouts Generally speaking,
the more cylinders there are,
the more power the engine will produce
and the smoother the engine will run.
The only limit to the variety of layouts
is the designers imagination,
except to say it is uneconomical
(in manufacturing costs, capacity and use)
to design and build a 4 litre V8 layout engine
when a 2 litre V6 would do the job.

3. Introduction Piston Engine Layouts Single Inline 4 Inline 3 Inline 5
Vee 8
Vee 5
Vee Twin
Vee 6

4. Introduction Piston Engine Layouts Horizontally Opposed (or flat) 4
Vee 8
Firing Order: -
1 – 4 – 3 – 2
1 – 8 – 4 – 3 – 6 – 5 – 7 – 2

5. The Two-Stroke Cycle As its name suggests,
the operating cycle of this engine
is completed in two strokes,
down and up.
i.e. one complete revolution of the crankshaft.
Port A – Crankcase Inlet
Port C –
Exhaust Outlet
Port B – Cylinder Inlet

6. Port A – Crankcase Inlet
The Two-Stroke Cycle
Piston pushed down
forces fuel/air mixture
into cylinder;
Piston rising pulls
fuel/air mixture
into crankcase;
(Induction)
Stroke 1
Stroke 2
Compression is now
causing combustion
and out of the
Exhaust valve
Port A – Crankcase Inlet
Port C –
Exhaust Outlet
Port B – Cylinder Inlet

7. Mechanical Arrangement
The Petrol Engine
The Diesel Engine
This means that ignition is timed exactly when required
without relying on the timing of a spark.
Inlet
Exhaust
Same mechanical
set-up as the
petrol engine
BUT without an
ignition system
or spark plugs

8. Mechanical Arrangement
The Diesel Engine
Combustion is
initiated by
the temperature increase
in the compressed
air/fuel mixture.
Direct Injection
Indirect Injection
Inlet
Exhaust
Fuel is injected
Indirectly into the
inlet manifold, or
Directly into the
cylinder.
Fuel needs to be
injected to obtain the
correct supply rate.

9. Mechanical Arrangement
The Wankel Engine
The piston rotates around the fixed pinion.
This motion drives the
rotating crankshaft.
Which in turn drives
the output shaft.
Casing
Rotating Triangular ‘Piston’
Fixed
(non-rotating) Pinion
Inlet Port
Rotating ‘Crankshaft’
Output Shaft
Exhaust Port
Spark Plug
The piston shape and
the casing make the
piston move up & down
by a small amount as well.
Points of contact

10. Mechanical Arrangement
The Wankel Engine
There are 3 chambers formed by the triangular rotor and the casing.
As Chamber A rotates it draws in fuel/air
(Induction)
the chamber then gets smaller
(Compression).
Chamber B
Chamber A
The mixture is ignited
by the spark plug
in chamber B;
(Combustion/Power)
the expanding gases
then force the rotor
round.
Inlet Port
Exhaust Port
As chamber C rotates,
the exhaust port opens
and the gases forced out.
(Exhaust)
Chamber C

11. Mechanical Arrangement
Radial/Rotary Engines
Radials and Rotary engines look similar;
but in Radial engines, the crankcase and cylinders are stationary,
and the crankshaft rotates the propeller.
Whereas in Rotary engines, the crankshaft was stationary
and the crankcase and cylinders rotated to drive the propeller.
Crankcase
Cylinders
Propeller Mount Bolts
Valve Gear
Valve Pushrods
Spark Plugs

12. Mechanical Arrangement
Radial/Rotary Engines
Radial
Rotary
Aircraft Nose
(viewed from the front)
(viewed from the side)
Radial and Rotary engines were used commonly during WW2
in various transports, bombers and fighters.
Rotary engines, whilst the best for power to weight ratio at the time,
suffered some disadvantages -
Gyroscopic effect – rotating such a large mass
caused aircraft handling problems.
Oil system – it was difficult to recirculate the oil,
which literally splashed everywhere after leaving the engine.

13. Mechanical Arrangement
Radial/Rotary Engines
Radial
Rotary
Aircraft Nose
(viewed from the front)
(viewed from the side)
But making an engine obsolete does not mean it disappears -
Model aero engine
28 Cylinder Radial Engine
Radial Powered Motorbike

14. Check of Understanding
What is the limit
to the variety of cylinder layouts?
12 cylinders
24 cylinders
36 cylinders
No limit

15. Check of Understanding
What is the operating cycle
of a two-stroke engine?
¼ rotation of the crankshaft
½ rotation of the crankshaft
1 rotation of the crankshaft
2 rotations of the crankshaft

16. Check of Understanding
What happens on the down stroke
of a 2-stroke engine?
Induction
Compression
Combustion/Power
Exhaust

17. Check of Understanding
Which of the following statements
does not apply to a diesel engine?
Same mechanical set-up
as a petrol engine
Ignition cannot be timed
It has no spark plugs
Fuel needs to be injected

18. Check of Understanding
In a diesel engine,
where is fuel directly injected?
Into the piston head
Into the inlet manifold
Into the exhaust valve
Into the cylinder

19. Check of Understanding
In a Wankel engine,
How many chambers are formed
by the rotor and casing?
Five
One
Seven
Three

20. Check of Understanding
In a Wankel engine,
what happens in chamber A?
Only Induction
Only Compression
Induction and Compression
Exhaust

21. Check of Understanding
Which of the following statements
applies to a radial engine?
The crankcase rotates
The cylinders rotate
The crankshaft rotates
The crankshaft is stationary

22. PISTON ENGINES
End of Presentation