1. Design and Analysis of single cylinder two stroke diesel engine.
A Report Submitted for project based laboratory to K. L. University for the
partial fulfilment of awarding B. Tech Degree.
ID.No Name
13007293 Naga sai ram.G
13007295 Harieswar .A
13007270 Anwar Hussain .Sk
13007297 Arun Kumar.N.J
13007 Somsai
UNDER THE GUIDANCE OF
K.Mohana Venkata Ravi Teja
K.L. UNIVERSITY
Green fields, Vaddeswaram, Guntur Dist.522502
2. DECLARATION
We hereby declare that the work in this project is our own except for
quotations and summaries which have been duly acknowledged. The
project has not been accepted for any degree and is not concurrently
submitted for other awards.
Date: 08/11/2015 Place: Vaddeswaram
3. K.L. UNIVERSITY
Green fields, Vaddeswaram, Guntur Dist.
CERTIFICATE
This is to certify that this project work entitled “Design and Analysis of two stroke single
cylinder desiel engine” By the above mentioned students is a bonified work carried out by
the students NAGA SAI RAM.G, Harieswar .A, Anwar Hussain .Sk, Arun
Kumar.N.J, Somsai in Department of Mechanical Engineering.
Project supervisor Head of the Department
4. ACKNOWLEDGEMENT
We express our sincere gratitude to our project guide
Mohana Venkata Ravi Teja.sir for encouraging and guiding us to
undertake this project work. We express our deep sense of gratitude to
Hanumanth rao sir and beloved course lecturers of department for
their encouragement.
Place: Vaddeswaram
Date:
5. Design and analysis of Single Cylinder Two
Stroke Diesel Engine.
ABSTRACT:
for the most of the engine the valve operations is the basic operations for the engine to work. Well
there are more approaches to the design of the cam and every one (companies and garage and
designers) have their own methodology in designing and fabricating them depending upon the
engine specification the cam are actuated with multiple valve operation principle like multiphase
actuation and variable valve lift operation and so on.In this case study we concentrate on the new
design approach called as flow lift quantization.
6. Introduction
1 BASIC TERMINOLOGY OF THE CAM SHAFT
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.
In internal combustion engines with pistons, the camshaft is used to operate poppet valves. It
then consists of a cylindrical rod running the length of the cylinder bank with a number of
oblong lobes protruding from it, one for each valve. The cam lobes force the valves open by
pressing on the valve, or on some intermediate mechanism as they rotate.
Working of Camshaft
A camshaft is a long bar with the cams called as lobes, one lobe for each valve and fuel injector.
Each lobe has a follower .as the camshaft is rotated, the follower is forced up and down as it
follows the profile of the cam lobes, the followers are connected to engine valves and fuel
injectors through the various type of linkages called pushrods and rocker arms. The push rods
and rocker arms provide reciprocating motion generated by the camshaft lobes to the valve and
injector causing opening and closing as they are needed. The valves are maintained by the
springs. It is typically connected to a flywheel to reduce the pulsation characteristic of the four-
stroke cycle, and sometimes a torsional or vibrational damper at the opposite end, to reduce
the torsional vibrations often caused along the length of the crankshaft by the cylinders farthest
from the output end acting on the torsional elasticity of the metal.
Materials used
Camshafts can be made out of several types of material. These include:
Chilled iron castings: this is a good choice for high volume production. A chilled iron camshaft
has a resistance against wear because the camshaft lobes have been chilled, generally making
them harder. When making chilled iron castings, other elements are added to the iron before
casting to make the material more suitable for its application.
Billet Steel: When a high quality camshaft is required, engine builders and camshaft
manufacturers choose to make the camshaft from steel billet. This method is also used for low
volume production. This is a much more time consuming process, and is generally more
expensive than other methods. However the finished product is far superior.
Types of the camshaft assembly
1) Chain driven camshaft assembly
2) Gear driven camshaft assembly
7. Parts of Camshaft
The camshaft generally have the following parts in any specification design book.
According to the Ron Fitzrberg design book 11
figure 1a showing thr assembly of the chain driven camshaft assembly and Gear driven
camshaft assembly
Cycles of the Camshaft:
Intake Stroke - exhaust valve is closed, intake valve is open to let air into the cylinder.
Compression Stroke - both valves are closed so that no air leaks out of the cylinder, lowering
pressurization.
Power Stroke - both valves are still closed so that expanding air can transmit its force
completely to the piston.
Exhaust Stroke - intake valve is closed, exhaust valve opens to let the exhaust out of the
cylinder.
The operation of intake and exhaust valves overlaps nearing the end of the exhaust stroke
because the intake valve actually starts to open before the piston has completed its travel to the
top of the cylinder. The overlap is supposed to take advantage of the scavenging effect whereby
the sudden rush of air-fuel mixture suddenly entering the combustion chamber forces more of
the exhaust gases out of it. Overlapping the intake and exhaust strokes also makes engine run
more smoothly.
8. Materials
Camshafts can be made out of several types of material. These include:
Chilled iron castings: this is a good choice for high volume production. A chilled iron camshaft
has a resistance against wear because the camshaft lobes have been chilled, generally making
them harder. When making chilled iron castings, other elements are added to the iron before
casting to make the material more suitable for its application.
Billet Steel: When a high quality camshaft is required, engine builders and camshaft
manufacturers choose to make the camshaft from steel billet. This method is also used for low
volume production. This is a much more time consuming process, and is generally more
expensive than other methods. However the finished product is far superior. When making the
camshaft, CNC lathes, CNC milling machines and CNC camshaft grinders will be used.
Different types of steel bar can be used, one example being EN40b. When manufacturing a
camshaft from EN40b, the camshaft will also be heat treated via gas nitriding, which changes
the micro-structure of the material. It gives a surface hardness of 55-60 HRC. These types of
camshafts can be used in high-performance engines.
Duration
Duration is the number of crankshaft degrees of engine rotation during which the valve is off
the seat. As a generality, greater duration results in more horsepower. The RPM at which peak
horsepower occurs is typically increased as duration increases at the expense of lower rpm
efficiency (torque).
Duration can often be confusing because manufacturers may select any lift point to advertise a
camshaft's duration and sometimes will manipulate these numbers. The power and idle
characteristics of a camshaft rated at .006" will be much different than one rated the same at
.002".
Many performance engine builders gauge a race profile's aggressiveness by looking at the
duration at .020", .050" and .200". The .020" number determines how responsive the motor
will be and how much low end torque the motor will make. The .050" number is used to
estimate where peak power will occur, and the .200" number gives an estimate of the power
potential.
Lift
The camshaft "lift" is the resultant net rise of the valve from its seat. The further the valve rises
from its seat the more airflow can be released, which is generally more beneficial. Greater lift
has some limitations. Firstly, the lift is limited by the increased proximity of the valve head to
the piston crown and secondly greater effort is required to move the valve's springs to higher
state of compression. Increased lift can also be limited by lobe clearance in the cylinder head
construction, so higher lobes may not necessarily clear the framework of the cylinder head
casing. Higher valve lift can have the same effect as increased duration where valve overlap is
less desirable.
9. Higher lift allows accurate timing of airflow; although even by allowing a larger volume of air
to pass in the relatively larger opening, the brevity of the typical duration with a higher lift cam
results in less airflow than with a cam with lower lift but more duration, all else being equal.
On forced induction motors this higher lift could yield better results than longer duration,
particularly on the intake side. Notably though, higher lift has more potential problems than
increased duration, in particular as valve train rpm rises which can result in more inefficient
running or loss of torque.
Cams that have too high a resultant valve lift, and at high rpm, can result in what is called
"valve bounce", where the valve spring tension is insufficient to keep the valve following the
cam at its apex. This could also be as a result of a very steep rise of the lobe and short duration,
where the valve is effectively shot off the end of the cam rather than have the valve follow the
cams’ profile. This is typically what happens on a motor over rev. This is an occasion where
the engine rpm exceeds the engine maximum design speed. The valve train is typically the
limiting factor in determining the maximum rpm the engine can maintain either for a prolonged
period or temporarily. Sometimes an over rev can cause engine failure where the valve stems
become bent as a result of colliding with the piston crowns.
Position
Depending on the location of the camshaft, the cams operate the valves either directly or
through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and
leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders. In
the past when engines were not as reliable as today this was seen as too much bother, but in
modern gasoline engines the overhead cam system, where the camshaft is on top of
the cylinder head, is quite common.
Number of camshafts
While today some cheaper engines rely on a single camshaft per cylinder bank, which is known
as a single overhead camshaft (SOHC), most modern engine designs (theoverhead-valve or
OHV engine being largely obsolete on passenger vehicles), are driven by a two camshafts per
cylinder bank arrangement (one camshaft for the intake valves and another for the exhaust
valves); such camshaft arrangement is known as a double or dual overhead cam (DOHC), thus,
a V engine, which has two separate cylinder banks, may have four camshafts (colloquially
known as a quad-cam engine).
More unusual is the modern W engine (also known as a 'VV' engine to distinguish itself from
the pre-war W engines) that has four cylinder banks arranged in a "W" pattern with two pairs
narrowly arranged with a 15-degree separation. Even when there are four cylinder banks (that
would normally require a total of eight individual camshafts), the narrow-angle design allows
the use of just four camshafts in total. For the Bugatti Veyron, which has a 16-cylinder W
engine configuration, all the four camshafts are driving a total of 64valves.
10. Maintenance
The rockers or cam followers sometimes incorporate a mechanism to adjust and set the
valve play through manual adjustment, but most modern auto engines have hydraulic lifters,
eliminating the need to adjust the valve lash at regular intervals as the valvetrain wears, and in
particular the valves and valve seats in the combustion chamber.
Sliding friction between the surface of the cam and the cam follower which rides upon it is
considerable. In order to reduce wear at this point, the cam and follower are bothsurface
hardened, and modern lubricant motor oils contain additives specifically to reduce sliding
friction. The lobes of the camshaft are usually slightly tapered, causing the cam followers or
valve lifters to rotate slightly with each depression, and helping to distribute wear on the parts.
The surfaces of the cam and follower are designed to "wear in" together, and therefore when
either is replaced, the other should be as well to prevent excessive rapid wear. In some engines,
the flat contact surfaces are replaced with rollers, which eliminate the sliding friction and wear
but adds mass to the valvetrain.
Timing Of The Camshaft:
The sequence of the opening and closing of the valves, overlap, and lift (how much they open
the valve) have a great effect on engine performance at a given speed. These parameters are
controlled by the cam design (i.e. - the height of the lobes, the angle at which they are
positioned on the cam shaft) but until recently, they were fixed for a given engine running at
all speeds. The result is varying engine efficiency and output at different speeds, now featuring
variable cam timing that tries to maintain optimum engine performance and efficiency by
compensating for the different valve timing required at various engine speeds and loads.
Increasing the number of valves per cylinder is limited by the complexity of manufacturing the
camshafts and followers for those designs, the increased unreliability brought about by
introducing so many moving parts in the engine, and the difficulty that will be encountered in
making the valves strong enough to withstand engine stresses when they become smaller as
their number increases.
Case study and assumption
To simplify the study proceedure and the analysis of the camshaft assemby the following
assumptions are made
1) The gear driven camshaft assembly is taken as objective of the case study
2) Porshe 968 Engine timing values are taken to simulate the model with some optimal
timing.
3) 8 Cam configuration is taken.
4) Temperature distribution on the Cam is taken as the pior study objective of the case
study.
11. 5) The FEA model is solved using the Solidworks 2014 Professional version
Figure 1B showing the Porshe 968 engine timing chart of force cylinder with engine basic
cycle
Valve attributes and design iteration model of a Cam shaft.
To increase the efficiency, it is ideal that the change in the cam angles for the response of the
system there could be the possibility of change in the efficacy there by increase the performance
of the engine somehow or the other by the anther multiplier of any other parameter. The
following derivation shows the possible relation between the angle of lift and valve opening of
and the closing of the engine. This later used for the designing the timing diagram of the cam’s
and valve opening.
The lift of the cam is directly imposing effect on the valve opening of the engine so the
following expression shows the quantized equation of the system as follows.
L∞ H
Where L is called as lift of the cam.
H is called as the height of the valve opened
The lift of the cam is a design variable denoted by the L if it is possible that the lift is quantized
after the motion is transposed back at the valve it is the same. The following shows the possible
relation of the area of the valve opened by the response of the lift which is called as curtain
area.
AC = π * LV * DV
Where Ac is the area of the curtain.
Lv is the lift of the valve
DV is the diameter of the valve.
But the flow of fuel is dependent on the net effective area of the valve and the expression is
given by the following formula as
12. AVALVE AREA = 0.785*(Dvalve2
– Dstem
2
).
Where DVALVE is the diameter of the valve
Dstem is the diameter of the stem of valve.
But the valve is also called as the curtain area hence the formula is rewritten as follows as
follows.
AVALVE AREA = 0.785*(π * LV * DV ) .
Coming back to the discharge of the valve the following formula is consider.
Q=VA
Where Q is the discharge
V is the velocity of flow
A is the area.
By using the above equation and resubstituting them
Q=V (0.785*(π * LV * DV )) but this is a static and point in nature to extend our discussion in
the times of pressures and temperatures of the vale the following relation is taken as follows.
m = ρo*co*AE(
pt
𝑝𝑝𝑝𝑝
)1/γ
[
2
𝛾𝛾−1
{1- (
pt
𝑝𝑝𝑝𝑝
)γ-1/γ
}]1/2
where ρo = density.
PO =upstream stagnation pressure.
Co = speed of the sound
TO = ambient temperature
Pt = downstream flow pressure.
For flow into the cylinder through an intake valve:
• Po = the intake system pressure, Pi
• PT = the cylinder pressure.
For flow out of the cylinder through an exhaust valve,
• Po = the cylinder pressure
• PT = the exhaust system pressure
We know that m= V A r.
So the velocity is so designed as follows
V= co* (
pt
𝑝𝑝𝑝𝑝
)1/γ
[
2
𝛾𝛾−1
{1- (
pt
𝑝𝑝𝑝𝑝
)γ-1/γ
}]1/2
so the design variable is taken out for the design
validation without velocity hence the following expression is made as
m ∞ ρo * AE the product of density and area is called as Vaux factor and the graph generally
forms as follows.
13. M ∞ ρo* 0.785*(π * LV * DV ). Hence this is a linear model according to the system and the
further formulation is formulated as follows
M ∞ LV the response of the system is given as follows.
So the mass flow rate of the system is a dependent variable of the lift of the cam.
Hence proved.
However, the entire engine can’t be simulated by single shot the cam valves are prior taken and
the life is calculated and the placed in the above equation so as to form the amount of fuel flow
through the curtain area as of density is constant and the flow parameter is taken in the same
way. The following empirical formulation is taken for the getting the lift of cam.
The mass flow rate of the fuel is basically taken in the valve curtain area which is given as
follows in the terms of bore and stroke and r.p.m of the engine and the stem area of the valve.
𝜋𝜋
4
�
𝑁𝑁𝑁𝑁𝐿𝐿2
2,286,000
-
𝜋𝜋
4
𝐷𝐷𝑆𝑆
2
= ACURTAIN…………………………………………………………………(1)
DS is the diameter of the stem.the area of the stem is quantized by following relation.
AS = ¾ AC…………………………………………………………………(1a)
From the above equation is applied into flow through the area of curtain is given by following
formula.
𝑚𝑚̇ = ACURTAIN ρ V…………………………………………………………(2)
Where 𝑚𝑚̇ is called as mass flow rate.
ACURTAIN is called as area of curtain.
ρ is called as density of fuel 850 kg/m3
V is the velocity of the fuel.
The above is for the no change in curtain length so the curtain length that is lift of cam is placed
and the following equation is generated.
𝑚𝑚̇ = ACURTAIN ρ V Lv…………………………………………………………………………………….(3)
And the lift of cam is gained by the equation transformation as follows.
𝑚𝑚̇
∁ 𝑉𝑉
= LV……………………………………………………………………….(4)
Where C is the flux flow.
The following is the data taken into account for caluculation.
Bore diameter is 0.8 meters.
Stroke of engine is 0.11 meters.
RPM of the engine desired is 3600
14. Diameter of the valve is
𝜋𝜋
4
�
3600∗80∗1102
2,286,000
= 0.039 meters.
Area of the valve is 0.001194 meters.
Area of the stem is = ¾ AC = 0.0008955 meters.
Area of the curtain is 0.00029909 meters.
The following tabulation gives the iterations of mas flowrate and velocity.
MASS FLOW RATE FLUX VELOCITY LIFT 0F CAM
15 0.248245 60.42425 0.004767
16 0.248245 64.45253 0.004767
17 0.248245 68.48082 0.004767
18 0.248245 72.5091 0.004767
19 0.248245 76.53738 0.004767
20 0.248245 80.56567 0.004767
21 0.248245 84.59395 0.004767
22 0.248245 88.62223 0.004767
23 0.248245 92.65052 0.004767
24 0.248245 96.6788 0.004767
25 0.248245 100.7071 0.004767
26 0.248245 104.7354 0.004767
27 0.248245 108.7637 0.004767
28 0.248245 112.7919 0.004767
29 0.248245 116.8202 0.004767
30 0.248245 120.8485 0.004767
Therefore the cam is designed as lift in 0.004767 meters. With taking the mean data 22.5 mass
flow rate and 0.004767 lift. The differential valve timing gives the differential mass flowrates.
The following is the technical diagram of an cam designed in Solidworks 2014. And keyshot.
Figure 1.0 showing the rendered camshaft in Keyshot 5 with stainless steel and anonised faux
steel
16. Design of Cam shaft.
From the cams designed from the above they are assembled in solidworks to get the cam
shaft a shaft.
Figure 1.1 showing the camshaft as a model.
figure 1.2 showing the mesh data of an model.
17. The following gives the thermal analysis of the cam shaft.
Figure 1.3 showing the temparature distribution on the cam shaft.
figure 1.4 showing the total heat flux on the cam shaft
The following gives the structural analysis of the camshaft.
Figure 1.5 shows the total deformation on the camshaft.
18. Figure 1.6 showing the Directional deformation in x axix of the cam shaft.
Figure 1.7 showing the isometric view of strains of camshaft.
figure 1.8 showing the von misess stress of the camshaft.
21. Results and discussions.
the fllowing graph shows the minimum and maximum quintisation of the values which we can extend
the study.
As from above we can see that the overall design values of total heat flux and stress values are
in great extent but often never fell in out side of safty factor and over all thermal properties are
most likely to be in the zero quintisation and the thermal equibrium is gained in the parameters
made as assumptions.though the thermal error of maximum but the minium value is rounding
back to zero hence the fluctuation of above thermal values is likely show the intresting pattrens
which can be extended.
22. References:
1) Camshaft – Wikipedia https://en.wikipedia.org/wiki/Camshaft.
2) Textbook of Engine design by Arkeson and Koba Denstu Acess from open libery of
Edith Cowan University, Perth 2 Bradford St, Mount Lawley WA 6050, Australia.
