This document describes the design of a cam reciprocating engine as an alternative to conventional reciprocating engines with crankshafts. The new design aims to improve volumetric efficiency by removing all exhaust gas particles from the combustion chamber clearance volume. It does this by using a piston shape that matches the clearance volume, allowing it to push out exhaust gases during the exhaust stroke. A cam is used instead of a crankshaft to enable variable stroke lengths, providing clearance volume during compression but removing it during exhaust. The document provides the specifications of an example engine and details the design process for the cam profile and piston.

1. 1
Design of Cam Reciprocating Engine
S.Balamurugana
, I.Saravananb
a
Adhi College of Engineering and Technology, Kanchipuram, Tamilnadu, India
b
Adhi College of Engineering and Technology, Kanchipuram, Tamilnadu, India
Abstract
This paper presents about the design of cam reciprocating engine. For this new design of cam operated
reciprocating internal combustion engine the changes such as removing of crank shaft, introducing of cam, retention of
exhaust gas particles exist in the clearance volume of the reciprocating internal combustion engine will be removed by the
piston itself instead of fresh air and fuel particles as used in the current engines and to improve the suction in the engine
cylinder, the intake of fresh air and fuel particles will be happens after creation of small vacuum inside the cylinder. This
project mainly focuses on improving the volumetric efficiency of the reciprocating internal combustion engine by
removing all of the exhaust gas particles present in the clearance space.
Index Terms—Displacement diagram for suction stroke and compression stroke, cam profile, piston model, model
of cam engine.
I.INTRODUCTION
Now a day’s energy and power are the most
valuable things in our world. Because the resources of
materials used to produce the energy and power are
reduces day by day due to the utility of these things in
our life. In the other hand the corresponding
organizations and industries would like to create the
awareness about the energy consumptions, energy saving
methods and energy production technologies. The well-
known slogan about the energy is that,
1 unit of energy saving = 2 units of energy production
For this energy saving two methods are available. First
one is optimum utilization of energy that will leads to
energy saving. On the other hand reducing the losses is
also one type of energy saving method. There are lots of
losses available to waste the energy among the different
type of energy production technologies. In that
reciprocating internal combustion engine is the major
one that is used in vehicles for transportation in our day
to day works. Normally the efficiency of actual
reciprocating internal combustion engine is lower than
that of its theoretical cycle. This reduction in the
reciprocating engine efficiency will be due to the
following losses happens during the engine cycle.
These losses occurs due to,
1. Heat transfer
2. Friction
3. Blow down losses ofexhaust gas particles
4. In-efficient suction
In the above mentioned losses the first two losses are
unavoidable. But the other two losses are related to each
other. This blow down losses and in-efficient suction are
happens due to retention of exhaust gas particles in the
clearance volume of combustion chamber of the
reciprocating engine. To reduce these blow down losses,
the normal reciprocating engine is little bit modified in
this project work. With these modifications this work
focuses to improve the volumetric efficiency of the
reciprocating internal combustion engines.
II.PROBLEM IDENTIFICATION
While look into the cycle of IC engine the
process moves from exhaust stroke of previous cycle to
the suction stroke of the next cycle. During these change
of process, some amount of exhaust particles of previous
cycle is retained in the clearance volume even the piston
will be at TDC. This is called as blow down loss in the
reciprocating engine. And the piston moves from TDC to
BDC for the next power cycle. During this downward
movement of piston, the volume increases. So that the
retained exhaust gas particles also gets expanded. This
expansion increases the volume of the exhaust gas
particles. That the retained exhaust gas particles occupies
the volume more than that of its engine clearance
volume, during this expansion.
TDC – Top Dead Center
BDC – Bottom Dead Center
Vc – Compression Volume
Vs – Swept (or) Stroke Volume

2. 2
III.CONCEPT OF NEW DESIGN
The main theme of this new design is to
increase the volumetric efficiency by removing all the
retained exhaust gas particles in the clearance volume of
the normal reciprocating engine. As discussed in the
previous, the retained exhaust gas particles in the
clearance volume occupies more volume than that of its
clearance volume during the expansion (suction) stroke
of next power cycle. So that the mass and volume of the
fresh intake for the next power cycle will be lowered in
the convention reciprocating engine design. Thus the
volumetric efficiency will be lowered in the actual cycle
compared to theoretical cycle.
ηvol = Actualmas of fresh intake
Theoretical mass of fresh intake
(Or)
ηvol = Volume of fresh intake entered
Stroke volume (or) swept volume
If the exhaust gas particles will be removed
fully, the mass and volume of fresh intake will also be
increases. So that volumetric efficiency will be increases
correspondingly. For the removal of all exhaust gases
retained in the clearance volume of the combustion
chamber, the piston is designed as such of its clearance
shape. Thus the piston head and the clearance chamber
are almost of same shapes and approximately equal
radius. When the piston is at TDC, the piston head will
occupy the entire clearance volume. So there is no
clearance space between the engine head and clearance
chamber. During the exhaust stroke, the piston moves
from BDC to TDC. Thus the piston tends to pushes all
the exhaust gas particles. Due to this design changes,
during the upward movement of piston all the exhaust
gases pushes out from the combustion chamber to
exhaust port of the reciprocating engine. So that fresh
intake of the next cycle is almost equal to the total
volume of the engine. Thus the intake volume will be
increases as compared to the conventionalengine.
IV.DESIGN CONSIDERATIONS
As discussed in the conceptual design, the
piston head is as same as the clearance shape of the
engine head. Thus there is no clearance space in the
combustion chamber of the reciprocating engine, while
the piston moves from BDC to TDC. We should focus
on the process and valve movement during the
movement of piston from BDC to TDC.
The processes involved in the reciprocating engine cycle
for piston movement from TDC to BDC are as follows:
1. Exhaust stroke
2. Compression stroke
During the exhaust stroke of the reciprocating engine
cycle the inlet valve is in closed position whereas the
exhaust valve will be in the open position. As per new
design the piston head occupies the entire clearance
space of the combustion chamber during the exhaust
stroke. At the same time the exhaust valve will be
opened, that the exhaust valve move some distance
inside the combustion chamber. So that there will be the
interference between the exhaust valve and piston head
of new design.
Then look into the compression stroke there is no
clearance space when the piston is at TDC. This is the
right choice for exhaust stroke whereas for the
compression stroke the fresh intake has to be compressed
at optimum level for good combustion of air and fuel. So
that new design should provide some clearance space for
the compression of fresh intake during compression
stroke and there is no clearance space during the exhaust
stroke.
V.DESIGNREQUIREMENTS
The following two problems occurs in the
reciprocating engine cycle as per the new design and are
follows,
1. Interference of exhaust valve with the piston
head during exhaust stroke
2. Clearance space has to be provided during the
compression stroke
3. There is no clearance space during the exhaust
stroke
4. Transfer of force from piston to cam
With the above requirements cannot run the
reciprocating engine by using the crank. Because the
crank will always moves the piston for a constant stroke
length. But requirement is to provide clearance space
during compression stroke only and clearance space
must be removed during the exhaust stroke. This
clearance space will be provided in the combustion
chamber of the reciprocating engine, if the piston moves
shorter stroke length during the compression stroke. And
to remove the clearance space during the exhaust stroke
the piston has to moves longer stroke. Thus the piston
moves with the stroke length during the exhaust stroke
will be longer than that of compression stroke.
Thus the piston has to moves with variable stroke
lengths for a single power cycle. If the piston connected
with the crank through connecting rod this variable
stroke will not be achieved. So that crank has to replace
by some other mechanical elements for the variable
stroke length. The cam is the best mechanical element
for the variable stroke length with the smooth operation.
Thus the crank should replace by the cam.
As per the requirements of new design of cam
reciprocating engine, the crank has to be replaced by the
cam. In the conventional reciprocating IC engines the
crank is connected to the piston through the connecting
rod with rigid fixings. And look into the movements of
piston, the piston receives the energy from the crank
through connecting rod during the suction, compression
and exhaust strokes. But in the power stroke the energy
is transfer from the piston to crank through same via.
Due to the rigid fixing the transfer of force in both cases

3. 3
is easy and ensured. But in our design there is a cam
instead of crank.
So that as per this new design the force has to transfer
fromthe cam to piston except the power stroke. Thus the
cam has to actuate the piston just like a follower. But
during the power stroke the transfer of force is vice
versa. This means the piston (follower) has to rotate the
cam during the power stroke. Thus the theme of this
design is just like cam and follower mechanism. In the
cam and follower mechanism the transfer of force from
the cam to follower is easy and endurable. It is almost
applicable in most of the applications. But in this case
the transfer of force from the follower (piston) to the
cam must be ensured because the entire energy by the
air-fuel burning, impacts the piston. And this energy is
reused for other three processes.
VI.MODEL SPECIFICATION
Before starting the design work of the cam
reciprocating engine, the conventional engine was
studied. For this study purpose, engine with the
following specification was taken.
Model–Reciprocating IC engine
Type–Four stroke
Ignition–Spark ignition
Fuel–Petrol
Stroke – 50mm
Bore – 50mm
Valve lift – 5mm
Projection of spark plug – 5mm
Valve angle - 70º to piston head
Clearance volume height – 15mm
VII.DESIGN OF CAM
Clearance volume in existing design
Vc =
𝜋ℎ
6
(3𝑎2
+ ℎ2
) h = 15mm a = 24.7mm
Vc=
𝜋𝑥15
6
(3𝑥24.72
+ 152
)
Vc = 16142.05mm3
Clearance volume in new design
𝜋ℎ
12
(3𝑎2
+ ℎ2
) +
𝜋
6
𝐷2
∆𝐿 = 16142.05
∆𝐿 = 4mm
Suction stroke length LS = 50mm
Compression stroke length LC = LS - ∆𝐿
LC = 50 – 4
LC= 46mm
Displacement diagram for suction & exhaust stroke
Displacement diagram for compression & power stroke
Profile of cam
Assume that the cam rotates in the clockwise direction
and the processes of a cycle of engine is mentioned
below:
1-2 → suction 2-
3 → compression
3-4 → power
4-1 → exhaust
Stroke length for suction & exhaust strokes – 50mm
Stroke length for compression & power strokes – 46mm

4. 4
VIII. DESIGN OF PISTON
IX. CAM ENGINE MODEL
X.CONCLUSION
The proposed cam reciprocating engine was
designed with the reference model engine. During this
design process the compression volume, stroke and bore
diameter was maintained as in the reference model
engine. First this cam reciprocating engine was designed
to remove entire exhaust gas particles retained in the
clearance volume. Thus half of the retained exhaust gas
particles of the reference model will be removed in this
new cam reciprocating engine. So that fresh intake will
be increased than that of reference model engine. This
cam reciprocating engine was designed using the
modelling software.
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