Hello knowledge aspirants, today
we are going to learn the idea of five stroke engine. Yes you are reading
correctly its five stroke not four stroke engine. When we have discussed eight
stroke engine at that time we have mentioned that eight stroke engine was
combination six stroke and five stroke engine and today we will go through
construction and working of these engines. It is recommended that you also read
my article on eight stroke engine for better understanding.
So the idea and development of
five stroke engine is given by the ilmor private limited company which was
established in 1983. It is a British company which deals with high performance
automobile engineering. It is also the same company which had partnership with
McLaren and Mercedes Benz to power their F1 cars.
Construction
In practice this engine consists
of basic parts of our normal engine. There is not much difference between our
normal four stroke engine parts and five stroke engine parts. So one can easily
manufacture a five stroke engine without using any special part. This is a big
advantage of this engine.
Five stroke engine consists of two
high pressure (H.P.) cylinder and one low pressure (L.P.) cylinder. So it is
require to have at least three cylinder for five stroke engine. Exhaust manifolds
of H.P. cylinder are attached with the intake of L.P. cylinder. And intake of
H.P. cylinder and exhaust of L.P. cylinder has normal arrangement as of four
stroke engine.
Working
Before understanding working of
whole engine first we have to study working of both H.P. and L.P. cylinder
individually.
H.P. Cylinder
These two cylinders has four
strokes exactly same as normal four stroke engine
Stroke 1 (Suction) - Combustible
fuel enters through inlet valve
Stroke 2 (Compression) - Fuel is
compressed as piston goes upward
Stroke 3 (Power/Ignition) - Fuel
is ignited and piston is forced to move downward
Stroke 4 (Intermediate exhaust)
- Burnt gases exits from H.P. cylinder
L.P. Cylinder
Stroke 1 (Suction) – Exhaust gas
from H.P. cylinder enters through inlet valve
Stroke 2 (Exhaust) – Compressed
gases are expelled from cylinder
Working of engine
(1) At starting first two strokes in H.P. cylinder 1
takes place. Remaining both moves with crank shaft without any supply.
(2) Remaining two strokes of H.P. cylinder 1 takes
place and exhaust of H.P. cylinder 1 is sent to L.P. cylinder 1. At same time
first two strokes of H.P. cylinder 2 takes place.
(3) Now again first two strokes in H.P. cylinder 1
takes place. Meanwhile exhaust of H.P. cylinder 2 is sent to L.P. cylinder 1.
(4) And cycle repeats.
Advantages
(1) A single
cylinder four stroke engine produces 4 power strokes in two rotation while in 3
cylinder five stroke engine also generates 4 power stroke during two rotation
but this power strokes are of low impulse hence there is condition of evenly
balanced low magnitude forces. So it easy to balance forces in this
engine.
(2) In normal engine exhaust gases are expelled at
high pressure hence generates noise. But in five stroke engine due to expansion
of gases in low pressure cylinder noise is reduced.
(3) This engine also reduces emission of
hydrocarbons as it will be easier to reduce compression ratio. In normal
engine emission of hydro carbon increases with increase in compression ratio.
(4) A secondary cylinder provides an additional
expansion process enabling extra work to be extracted, hence increasing
thermodynamic efficiency.
(5) The engine runs an overall expansion ratio
approaching that of a diesel engine – in the region of 14.5:1. (source ilmor
website)
(6) Less tendency of knocking.
(7) Engine has no special parts hence it makes manufacturing
easier.
Useful links
This animation video will help
you to understand this concept easier.
Ilmor official page –Ilmor
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