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Design of Four Stroke Engine Simulation Model to Optimize Volumetric

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021

Design of Four Stroke Engine Simulation Model to

Optimize Volumetric Efficiency at Variable Stroke Length
and Compression Ratio
Debarupam Gogoi Forijul Hoque Khitish Kumar Bora
Jorhat Engineering College Jorhat Engineering College Jorhat Engineering College
Mechanical Engineering Mechanical Engineering Mechanical Engineering
Department Department Department
debarupam@gmail.com forijulhoque678@gmail.com kkb.bora@gmail.com

Rupak Saha Abdus Salam

Jorhat Engineering College Jorhat Engineering College
Mechanical Engineering Mechanical Engineering
Department Department
rupakrpk111@gmail.com salamabdus5014@gmail.com

ABSTRACT B Distance between main bearings (mm)

Modelling and simulation tools are very essential supports in Ds Mean coil diameter of spring (mm)
today’s technology that reduce the physical prototypes in the
field of developing multidomain systems. Virtual prototyping L1 Connecting rod length (mm)
also decreases the product development time. This paper N No. of active spring coils
presents a virtual prototype model of a four stroke I.C. engine L2 Piston rod length (mm)
in which an incorporated mechanism will vary the stroke Nt Total no. of spring coils
length during suction stroke and allow more air to be drawn
into the cylinder instead of compressing the intake air to L3 Control lever lengths (mm)
increase the air density. It has a larger stroke length during the L4
suction and compression strokes. The stroke length during the L5 Free length of spring (mm)
power and exhaust strokes is identical to corresponding p Pitch of spring (mm)
conventional engine. As a result, larger volume of air is taken D1 Crank shaft pulley diameter (mm)
in during suction and is compressed. The volumetric k Stiffness of spring (N/mm)
efficiency thus increases. It has been seen that a maximum of D2 Cam shaft pulley diameter (mm)
2 cm extra stroke length may be obtained during suction and L6 Belt length (mm)
compression which yields a 12.5% increase in volume for the x Centre distance, Belt (mm)
proposed design of the model. Also, from dynamic simulation ω Angular velocity (rad/s)
curve, a maximum of 34% increase is observed. There is also
an increase in the thermal efficiency due to increased
compression ratio. The rest of the strokes are performed in the
same way as in a conventional engine. This increases the Keywords
engine efficiency. This concept introduces an economical Variable Stroke Length, Volumetric Efficiency, Variable
advantage over the turbocharger and supercharger. Compression Ratio, Simulation, CREO.
INTRODUCTION
The sole objective of the project lies in increasing
NOMENCLATURE the volumetric efficiency of the engine by having a variable
stroke length of the engine by introducing a cam-controlled
D Cylinder Bore (mm)
lever mechanism. With the evolution of IC engine an effort
r1 Base circle radius of cam (mm)
has always been made to increase the efficiency of the
L Cylinder Length (mm) Engine. Increasing the volumetric efficiency of the engine by
r2 Nose radius of cam (mm) proper combustion of the fuel is one of the successful methods
discovered.
d Piston diameter (mm) For the first time in 1878, supercharger was
α Angle of ascent of cam (degree0) invented by Dugald Clerk [1, 2] in order to increase the
l Piston length (mm) volumetric efficiency by increasing density of the intake
Φ Angle of contact on circular cam (degree 0) which is driven by shafting it with the output shaft. Due to a
major disadvantage of supercharger, as it consumes a part of
Dc Crank shaft diameter (mm) the output power, turbocharger has been developed with the
𝛿 Follower Lift (mm) same principle to increase volumetric efficiency with a
R Crank radius (mm) difference that it is powered by a turbine driven by the
ds Spring wire diameter (mm) engine’s exhaust. However, turbocharger also has certain

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021
disadvantages. Due to increase in the temperature of the kinematics, engine friction, specific fuel consumption, and
intake air, it may cause detonation especially in petrol efficiency. Moteki, K. et al. [15] presented a variable
engines. Also, turbocharger is very expensive. compression ratio (VCR) system that has a new multiple link
So, looking at these disadvantages our aim is to in piston-crankshaft mechanism. The multi-link mechanism
develop an engine such that the same task can be done with varies the piston position at top dead center (TDC), making it
comparative low cost in an effective manner. D. Osorio, possible to vary the compression ratio of the engine
Julian et al. [3] have proposed a Continuous Variable Valve continuously. Jiang, S. et al. [16] focused on a multiple-link
Timing (CVVT) system for load control in spark-ignition mechanism that realizes variable compression ratio and
engines, analyzed and compared with a conventional Throttle- displacement with varying piston motion, specifically the Top
controlled Engine. A fuel economy increment of up to 4.1% is Dead Center (TDC) and Bottom Dead Center (BDC) positions
observed from the analysis, for a CVVT Engine with relative to the crankshaft. They used Design of Experiments
reference to a Throttled Engine at a 20% – 30% load that is (DoE) methodology for creating sets of geometric designs of
typical of a real vehicle engine operation. Satyanarayana K. et the mechanism, in which kinematics are calculated and
al. [4] predicted the design performance based on stress-strain checked against the conditions.
behavior for three different variable compression ratios of a
diesel engine. Pournazeri Mohammad et al. [5] proposed and
1. METHODOLOGY
designed hydraulic variable valve actuation system which The joint between the piston rod and the connecting rod has
significantly improves the engine performance in terms of the control lever attached. The other end of the lever is
volumetric efficiency, fuel consumption etc. Wakode Vaibhav connected to the follower through a hinge. The lever gets its
R. et al. [6] investigated a modification on single cylinder motion from the follower. And the motion of the follower in a
diesel engine for three different values of compression ratios contour is controlled by a rotating cam with a spring
and fuel injection pressures. They found that fuel injection arrangement. The speed of camshaft is half the speed of the
pressure at 220 bar and compression ratio of 18 yields crankshaft. The camshaft gets the power from the crankshaft
optimum engine performance and emissions. Ganji; Rao itself by means of a belt drive (for the wooden model).
Prabhakara et al. [7] analyzed numerically using Mechanism for the variable stroke length engine, which was
CONVERGE™ Computational Fluid Dynamics code to drafted in CREO, is shown in figure 1. The various
optimize compression ratio and other related parameters at parameters of the model were designed and calculated as
100% engine load to test its performance and was found below:
satisfactory. Radivoje B. Pesic et al. [8] did both theoretical 1.1 Piston and Cylinder [17]
and experimental investigation of the impact of automatic For the model, the bore of the engine cylinder is assumed to
variable compression ratios on working process parameters in
be equal to D = 100mm and the Length of the cylinder, L =
experimental diesel engine. They illustrated and critically
150mm. The (L/D) ratio of the cylinder is usually in the range
examined alternative methods of implementation of variable
1.15 to 1.5. A larger range is taken considering variable
compression ratio. Doric, Jovan Z., et al. [9] presented a
stroke conditions. Assuming clearance, C = 2.5mm on each
simulation of variable movement of piston for obtaining
side we calculate,
variable compression ratio, variable displacement and
Piston diameter, (1)
combustion during constant volume. Yamin, Jehad A. A. et
al. [10] presented a theoretical study on the effect of variable = 95mm.
stroke length technique on the emissions of a water-cooled Piston length, l = 0.5d to 1.2d (2)
four-stroke, direct injections diesel engine with the help of
experimentally verified computer software designed mainly = 50mm.
for diesel engines. The emission levels were studied over the The crankshaft diameter is chosen as, Dc = 50 mm, crank
speed range in between 1000 rpm and 3000 rpm and stroke radius, r = 50mm. The distance between the main bearings,
lengths in between 120 mm and 200 mm, which were B = 2d to 3d (3)
compared with those of the original engine design. Yamin,
Jehad A.A. et al. [11] developed a simulation model and = 285 mm
verified with experimental results from the literature for both The connecting rod length is an important parametric
constant and variable-stroke engines which shows the consideration. In our design the length of the connecting rod
advantages of utility of variable stroke engines in fuel is kept short because we also use a “piston rod” and a “control
economy issues. G, Abhishek Reddy et al. [12] did an lever”. This arrangement is to control the position of the small
experimental investigation of the influence of compression end of the connecting rod required for the variation of stroke.
ratios 14, 15, 16 and 18 and engine loads of 3kg to 12 kg, with The connecting rod has greater angular swing when it is short
increments of 3kg, utilized for diesel on the brake power, as compared to the crank radius. The angular swing is suitably
brake thermal efficiency, brake mean effective pressure and controlled by the control lever itself.
specific fuel consumption for the Kirloskar variable Connecting rod length,
compression ratio dual fuel engine. Ebrahimi, Rahim [13] in L1 = 1.6 r (4)
his experiment showed that output power increases with
increase in stroke length if compression ratio is less than
= 80 mm.
certain value, on other hand the power output first increases The design of the piston rod is made with the care to minimize
and then start decreases with increase in stroke length if the side thrust on the piston. This is done by having a suitable
compression ratio exceeds certain value. The output power ( ) ratio. For moderate speed engines the ratio varies from 4
decreases with increase in stroke length for further increase in to 5 (V. B. Bhandari, 2017).
compression ratio. Asthana, S. et al. [14] reviewed the work Piston rod length,
of technological advancements in the design of a VCR engine L2 = 4r to 5r (5)
and describes the various techniques by which VCR is being
implemented and provides a qualified study for original and
modified technology on the basis of engine rigidity and piston Or L2 = 4.4 r (6)

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021
= 220mm. Angle of ascent, 𝛼 = 80°

Scale
We assume the following:

Fig. 1: Model of Variable Stroke Length Engine Mechanism

The distance between the cam center and nose center is
Length of Control Lever: calculated as,
The control lever is basically a rocker arm which applies a
moment to control the position of the small end of the
connecting rod about a hinge. OQ = Follower lift – (r2 – r1) (8)
The ratio of the lengths of the lever on either side of = 70 mm
the hinge is taken as We know, PQ =PF – FQ = PE – FQ = OP + OE – FQ
= 3. (7) = OP + 50 – 20 = OP + 30
From triangle OPQ,
Assuming, L4 = 50 mm,
PQ2 = OP2 + OQ2 – 2 × OP × OQ cos𝛽 (9)
L3 = 3 × L4
(OP + 30)2 = OP2 + 702 – 2 × OP × 70 × cos (180°–80°)
= 150mm. (10)
1.2 Cam profile [18]
The geometry is shown in Figure 2. Solving we get, OP = 112mm.
Therefore, Radius of circular flanks is given by
R = PE = OP + OE
= 162 mm.
And, PQ = OP + 30
= 142mm.
From triangle OPQ,
The angle of contact on the circular flank, ∅ is given by the
equation,
= (11)
Or, ∅ = 29°

1.3 Belt and Pulley (Wooden Model) [18]

The power is transmitted from the crankshaft to the camshaft
by means of a belt drive. Pulleys are mounted on the shafts.
One pulley is mounted on the camshaft of the model.
Speed of the crankshaft = N1
Speed of the camshaft = N2
Camshaft pulley diameter = D2
A groove on the crankshaft serves as a pulley itself. So,
Fig. 2: Cam profile geometry Crankshaft pulley diameter, D1=50mm.
The speed of the camshaft is half of the speed of the
We assume the following: crankshaft. Therefore,

Maximum lift of the follower is taken as 40mm.

Base circle radius, r1 = 50mm; Now, Velocity ratio is given as,
Nose circle radius, r2 = 20mm;

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021

(12) L5 = solid length + total axial gap + 𝛿 (21)

≅ 90 mm.
Pitch of the spring coil is calculated as,
Or, D2 = 100 mm.
The center distance between the shafts is found to be 43cm.
Since the center distance is small and is less than, so we p= (22)
choose a V-Belt Drive.
Now, the Length of the belt is calculated as, = 6.4 mm.
( ) The spring stiffness is calculated as,
( ) (13)
( ) k=( ) (23)
= ( )
= 110 cm = 1250.5 N/m.
Therefore, considering the calculations, a standard V-belt is
Table 1 shown below has listed various parts of the model,
chosen which has length 114cm.
their parameters with symbol and dimensions.
1.4 Spring (For Animated model) [19] Table 1 Dimensions of various parameters of the parts of
The follower lift is 40 mm. So accordingly, the required model.
deflection of the spring should be 40mm; i.e., 𝛿 = 40 mm. The Sl.
Parts Parameters Symbols Dimensions
spring material is patented and cold drawn steel wire of Grade No.
-1. For the spring material, G = 43350 N/mm2, spring index: C 1 Cylinder
Bore D 100mm
= 10, maximum force: P = 50 N, ultimate stress: Sut = 324 Length L 150mm
N/mm2 , shear stress: 𝜏 = 0.5 × 36.5 = 162 N/ mm2. 2 Piston
Diameter d 95mm
Wahl’s factor is calculated as, Length l 50mm
Diameter Dc 50mm
K= (14) Crank radius r 50mm
3 Crankshaft Distance
= between B 285mm
= 1.145 main radius
Shear stress is given by, Connecting
4 Length L1 80mm
Rod
𝜏=K( ) (15) 5 Piston Rod Length L2 220mm
Control L3 150mm
Or, 162 = 1.145( ) 6 Lengths
Lever L4 50mm
Or, ≅ 3 mm Base radius r1 50mm
Mean coil diameter is calculated as, Nose radius r2 20mm
D=C×d (16) Angle of
α 800
ascent
= 30 mm 7 Cam
Number of Active coils is calculated as, Angle of
contact on Φ 290
𝛿= ( ) (17) circular cam
Follower lift δ 39.98mm
Or, 40 =( ) Wire
ds 03mm
diameter
Or, N = 13. Mean coil
Assuming, the spring has square and ground ends. Number of Ds 30mm
diameter
inactive coils is 2. Therefore, Total number of coils is given No. of
by, N 13nos.
active coils
8 Spring
Nt = N + 2 (18) Total no. of
Nt 15nos.
= 15 coils. coils
Free length
Now, the actual deflection of the spring is given by, L5 90mm
of spring
𝛿=( ) Pitch p 6.4mm
Stiffness k 1250.5N/mm
Or, 𝛿 = 39.98 mm. Cam shaft
Solid length of the spring is calculated as, pulley D2 100mm
(19) diameter
9 Pulley
= 45 mm. Crank shaft
Axial gap between adjacent coils is found as 0.2mm and Solid pulley D1 50mm
length as 47mm. Therefore, diameter
Total Axial gap = ( ) axial gap between adjacent Length L6 110cm
coils (20) 10 Belt Centre
x 43cm
distance
= 2.8 mm.
Free length of the spring is calculated as,

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021
The wooden working model mechanism which adds a 2cm used to measure the variation of the strokes during the 4
length in suction and compression stroke is shown in figure 3. strokes of the engine cycle. The stroke length during suction,
compression, power and exhaust strokes is measured by
means of the scale. The difference in stroke length during the
first two strokes and the last two strokes of the engine cycle
gives the stroke variation of the model as listed in Table 2.

Table 2: Difference in stroke lengths obtained during the test

Sl. Stroke Length

Stroke Character
No. (cm)
1 Suction 18 L1
2 Compression 18 L2
3 Power 16 L3
4 Exhaust 16 L4

Average stroke lengths during suction and compression,

(24)
18 cm
Fig. 3: Wooden model of the mechanism
Average stroke lengths during power and exhaust,
CREO prepared model with different parts name has been (25)
shown in Figure 4.
16 cm
Therefore, variation in stroke length during suction and
compression, 18cm - 16cm = 2cm. The percentage
increase in volumetric efficiency depends on the varying
suction stroke length, which is given by Percentage increase
[20],
. (26)

Here, is the value of suction stroke length after variation

and is the length of the conventional stroke. So, Increase in
Volume = = 0.125 = 12.5 % and hence increase in
volumetric efficiency accordingly.
A dynamic analysis is done on the movement of the
piston inside the cylinder. A graph is plotted between the
stroke length and time period during different strokes for a
number of cycles. The graph shows that the stroke length
Fig. 4: Prototype model with Bill of Materials during suction and compression is larger than the power and
Two animated views showing two different (opposite) exhaust strokes. Then the cycle repeats. Hence the results
positions of cam are shown in figure 5. fulfill our objective. Figure 6 shows the analysis graph of the
simulating model prepared in Creo [21].

Fig. 5: Two different positions of cam in animated model.

Fig. 6: Dynamic analysis of the simulating model

2. TEST AND RESULTS
The Table 3 shown below reflects the value of percentage
After fabrication of the model, a scale is fitted to the cylinder. increase in efficiency for the different value of suction stroke
The cylinder is made to have a slit which allows the visual of
(the values are taken from the Creo model analysis graph).
the piston’s movement inside the cylinder. The scale is then

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 ISSN (O): 2393-8609
International Journal of Aerospace and Mechanical Engineering
Volume 8 – No.1, March 2021
Normal length Variable values of % increase in
of suction stroke length of suction volumetric increased by 12.5% and may be more for a better replica.
(L) in cm stroke ( ) in cm efficiency ( ) Secondly, of low cost as compared to a turbocharger /
5 6.5 30 % supercharger installed engine. Thirdly, Intake air pressure is
not increased as in a turbocharger or supercharger. So, the
5 6.4 28% issue of detonation in petrol engine is avoided.
5 6.7 34%
5 6.3 26% 4. ACKNOWLEDGEMENT
5 6.6 32%
We acknowledge to department of Mechanical Engineering
and staff members of workshop of Jorhat Engineering
Table 3: Variation of suction length and percentage increase College, Jorhat-785007, who directly or indirectly help us to
in volumetric efficiency against normal suction length complete the project.

Figure 7 shows a graph indicating percentage increase in 5. REFERENCES

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