Design and analysis of inlet manifold of a four stroke petrol engine by increasing tumble flow rate and reducing air pollution using aerofoil plate.
Rajendran, S. ; Purushothaman, K.
1. Introduction
Motor conveyances emit astronomically immense volume of carbon
monoxide CO, hydrocarbons HC nitrogen oxides NOx, carbon-di-oxide
C[O.sub.2] and toxic substances such as fine particles and lead as well
as contributing to secondary by products such as ozone. For spark
ignition engine a plausible solution for reducing emissions is by
controlling some combustion parameters, in such way engine performance
is kept unaltered. The nature of the flows behaviour and combustion in
spark ignition engines are important for improving the performance. The
flows in internal combustion engines can be achieved by enhancing the
tumble motion and swirl movement within the engine cylinder which
enhances the mean-flow and turbulence of the mixture. This flow motion
has a strong influence on the engine combustion process. Turbulence is
practically proved to be a phenomenon that leads to better mixing of air
and fuel. It's also leads to increased combustion rate due to
increased flame front. The advantages of inducing a tumble inside a
cylinder are they increasing to chances of complete combustion of mixing
the air and fuel. The turbulence induced by the tumble leads to better
heat flow rate to the cylinder walls. This reduces the uneven load on
the coolant. The in-cylinder flow motion in spark ignition engines is
one of the most important factors controlling the combustion process.
The Swirl and tumble motion are well known approaches for in-cylinder
flow enhancement. Multidimensional modelling became as an important tool
for investigating flow and combustion in reciprocating engines.
Hamai et al. [1] showed that incomplete mixing of fuel/air and
residual contribute to cycle to cycle variation in combustion. Also, the
increase of residuals resulted in increased cyclic pressure variability.
Engine speed also contributes to cycle to cycle variation in combustion,
where increasing the engine speed resulted in an increase in flame
speeds and cyclic flame speed variations. Increase in turbulence has
also been attributed to engine speed and the higher turbulence is the
main reason for the increase in flame speed variations. NanthaGopal et
al. [2] The exhaust emission levels have been focused on carbon monoxide
(CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter
(PM). Energy conservation on engine is one of the best ways to deal with
these problems since it can improve the energy utilization efficiency of
engine and reduces emissions.
Gosman et al. [3] and Yasar et al. [4] to do this, the geometry of
the inlet ports was defined utilizing six fundamental parameters. These
parameters were culled so that the initial and secondary factors, which
define the flow and tumble performance of a port, were included. Sugiura
et al. [5], Payri et al. [6] and Abhilash et al. [7] numerically and
experimentally studied with laminar and turbulent combustion flow in an
axisymmetric reciprocating engine without combustion through a cylinder
head port. Calculated and quantified results were in a good accedence.
They observed that the mean velocity field was influenced more
vigorously by the engine geometry than by the engine speed. In order to
simulate the mass flow rate and flow pattern of the induction system in
an internal combustion engine. Naitoh et al. [8] Computed velocities and
static pressures obtained from simulations were in a good accedence with
the experimental data. Computation of the three-dimensional flow in the
intake ports of and the cylinders of the authentic engines, including
moving valves and piston were carried out by solving the Navier-Stokes
equations. Barbouchi and Bessrour [9] and Theodorakakos et al. [10]
presented the analysis of the swirl intensity effects on spray formation
and obtained plausible accedence with experimental data. However, since
the intake process was not included in the calculation, the initial
swirl was imposed as a parameter. It can be mentioned that the way to
estimate the initial turbulence between these two studies is different.
MuraliKrishna and Mallikarjuna [11], MauriceKettner et al. [12] and
Adomeit et al. [13] have considered the intake valve as a single plate
and inflicted the swirl intensity and the intake angle as boundary
conditions. The overall in-cylinder tumble flows are much dependent on
the crank angle positions irrespective of engine speed. Rajendran and
Purushothaman [14] analyzed The result of volumetric efficiency depends
upon the position of throttle plate such as double throttle plate angle
60[degrees] is identically equal to 66.12%, 75[degrees] is identically
equal to 71.33% and 76[degrees] is equal to 67.76%. Rajendran and
Purushothaman. [15] studied the previous research article based on the
inlet flow of internal combustion engine.
1.1. Structure of pollutant in carbon monoxide (CO)
The amount of CO configuration increases as the mixture becomes
more and richer in fuel. A small amount of Carbon monoxide will emerge
from the exhaust even when the mixture is marginally lean in fuel
because air/fuel mixture is not homogenous and stability is not
conventional when the products pass to the exhaust. At the high
temperature developed during the combustion, the products formation are
uneven and following reactions take place before the stability is
recognized:
2C + [O.sub.2] = 2CO.
1.2. Structure of pollutant in Hydrocarbons (HC)
Hydrocarbons appears in exhaust gas due to local rich mixture
pockets at much lower temperature than the combustion chamber and due to
flame quenching near the metallic walls. A significant amount of this
unburnt HC may burn during expansion and exhaust strokes if oxygen
concentration and exhaust temperature is suitable for perfect oxidation.
2. Design and methodology of the aerofoil plate
The experiment facility of the inlet manifold is shown in the (Fig.
1). The most paramount part of our paper is to design the aerofoil plate
that involves in reducing the area of the inlet manifold through which
the air and fuel mixture enters the cylinder. It has to be designed and
mounted in the inlet manifold of most of the subsisting engines. We
opted to design an aerofoil plate in such a way that it is hinged at one
end and placed in cavity like arrangement in the inlet manifold without
making any appreciable changes to it.
[FIGURE 1 OMITTED]
The second most paramount thing is to design an aerofoil plate in a
way that it doesn't act as an obstruction to the airflow. Thus an
aerofoil design was achieved to make it feasible to reduce the area as
well as be aerodynamically efficient and avails in maintaining the flow
pattern of the air/fuel mixture. Hence it's very paramount to
actuate and position at point where it doesn't affect the flow. The
model of the aerofoil plate design and culled a module that proved to
have a very less coefficient of drag from which the Reynold's
number could be calculated to determine the nature of the flow of the
fluid over the surface. The design we incorporated very well proved to
have less co-efficiency of drag and hence the flow over it had a
Reynolds number that betokens that the flow around its surface is still
identically equal. After the tests we determinately incorporated this
aerofoil plate design with a provision for actuating mechanism.
3. Results and discussion
3.1. Experimental evaluation of Brake thermal efficiency, CO, HC
and C[O.sub.2]
The two different types of modified manifold (aerofoil plate) have
been analyzed in the flow path of a single cylinder four-stroke
naturally air cooled engine. The performance studied has been made for
brake thermal efficiency, CO, HC and C[O.sub.2] emissions of the
modified manifold with standard manifold the experimental analysis of
the turbulent flow and combustion in an idealized homogeneous charged
engine. Computations are performed for the different engine speeds and
load with aerofoil plate. The specification of engine cylinder diameter
is 100 mm and stroke is 90 mm.
From this simulation it can be visually perceived that by reducing
the area for the flow utilizing the aerofoil plate increases the
velocity of the fluid. Thus the incrementation in the velocity stream
line that is betokened by the velocity stream line index on the left, we
verbalize that it avails the fluid to gain more kinetic energy with
which the fluid molecules peregrinate more with more speed, hit the
cylinder wall and return towards the piston head which is near BDC at
that moment. This action is called tumbling and as verbally expressed
earlier the kineticism of the piston towards TDC in fact enhances the
indispensable turbulence to be achieved.
(Fig. 2, a) shows that the variation of brake thermal efficiency of
two different modified manifolds (aerofoil plate) based on speed. The
average brake thermal efficiency obtained by without modified model is
21.37%, with modified 8 mm thick plate is 24.33% and 10 mm thick plate
is 23.32% .therefore approximately 2.96% and 1.01% of brake thermal
efficiency increased in modified manifold with 8 mm and 10 mm aerofoil
plate. (Fig. 2, b) shows that based on speed, the average quantity of CO
emissions obtained by without modified model is 0.8515%, with modified 8
mm thick plate is 0.7232% and 10 mm thick plate is 0.8033%. Therefore
approximately 0.1283% and 0.0482% of CO decreased in modified manifold
with 8 mm and 10 mm thick aerofoil plate. (Fig. 2, c) shows that based
on speed, the average quantity of HC ppm in emissions obtained by
without modified model is 193.16 pmm, with modified 8 mm thick plate is
72.52 pmm and 10 mm thick plate is 124 pmm. Therefore approximately
120.64 pmm and 69.17 pmm of HC decreased in modified manifold with 8 mm
and 10 mm thick plate. (Fig. 2, d) shows that based on speed, the
average quantity of C[O.sub.2] emissions obtained by without modified
model is 5.08%, with modified 8 mm thick plate is 4.53% and 10 mm thick
plate is 5.05%. Therefore approximately 0.55% and 0.03% of C[O.sub.2]
decreased in modified manifold with 8 mm and 10 mm thick plate.
(Fig. 3, a) shows that the variation of brake thermal efficiency of
two different modified manifolds (aerofoil plate) based on torque. The
average brake thermal efficiency obtained by without modified model is
21.37%, with modified 8 mm thick plate is 24.73% and 10 mm thick plate
is 23.70%. Therefore approximately 3.36% and 2.34% of efficiency
increased in modified manifold with 8mm and 10mm thick aerofoil plate.
(Fig. 3, b) shows that based on torque, the average quantity of CO
emissions obtained by without modified model is 0.853%, with modified 8
mm thick plate is 0.706% and 10 mm thick plate is 0.78%. Therefore
approximately 0.147% and 0.073% of CO decreased in modified manifold
with 8 mm and 10 mm thick plate. (Fig. 3, c) shows that based on torque,
the average quantity of HC ppm in emissions obtained by without modified
model is 197 pmm, with modified 8 mm thick plate is 78.8 pmm and 10 mm
thick plate is 133.33 pmm. Therefore approximately 118 pmm and 63.67 pmm
of HC decreased in modified manifold with 8mm and 10 mm thick plate.
(Fig. 3, d) shows that based on torque, the average quantity of
C[O.sub.2] emissions obtained by without modified model is 5.53%, with
modified 8 mm thick plate is 4.75% and 10 mm thick plate is 5.33%.
Therefore approximately 0.78% and 0.2% of C[O.sub.2] decreased in
modified manifold with 8 mm and 10 mm thick plate.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
3.2. Effect of pressure drop in inlet manifold
Analysis of friction factor, pressure drop, heat transfer
coefficient and heat transfer rate for flow inside a circular tube for
laminar flow conditions.
3.2.1. Flow inside a circular tube
The flow condition inside a circular tube depends in the Reynolds
number which is defined as
Re = [[mu].sub.m]D/[gamma], (1)
when [[mu].sub.m] mean velocity of fluid, D is the inside diameter
of the tube and [gamma] is the kinematic viscosity of the fluid. The
flow inside the circular tube is laminar up to the Reynolds number is
2300.
3.2.2. Friction factor
To verify the friction factor we consider a small fluid element of
thickness dz the pressure force to the shear force of the aerofoil
plate:
[([P.sub.A]).sub.z] - [([P.sub.A]).sub.Z+dz] =
P[[DELTA].sub.z][[tau].sub.w], (2)
[([P.sub.A]).sub.Z] + [([P.sub.A]).sub.Z] - A dP/dz [[DELTA].sub.Z]
= P[[DELTA].sub.Z][[tau].sub.w], (3)
dp/dz = P/A [[tau].sub.w], (4)
when P is the perimeter, A is the cross sectional area and
[[tau].sub.w] is the aerofoil plate shear stress.
dp/dz = 4/D [[tau].sub.w]. (5)
Shear stress at the wall is given by:
[[tau].sub.w] = [mu] du/dy. (6)
The friction factor is defined as:
f = - 2d/[rho][mu][m.sup.2] dp/dz. (7)
Substituting the Eq. (7) in the friction factor:
d = - (8[mu])/([rho][mu][m.sup.2]) dp/dr. (8)
The velocity distribution u(r) is required which is obtained by
solving the equation of motion. The momentum equation for cylindrical
coordinate system is:
r - Momentum
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], (9)
z - Momentum
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. (10)
The mean flow velocity is:
[u.sub.m] = 1/[pi][R.sup.2] [integral] 2[pi]rudr , (11)
[u.sub.m] = 4m/[pi]p[d.sup.2]. (12)
The friction factor:
f = 64/Re. (13)
The pressure drop will be calculated for a given length of tube.
dp/dz = f L[rho][u.sup.2]m/2D, (14)
where f is the friction factor to be taken from the moody chart.
The following equation may also be used to calculate the friction factor
of smooth tubes:
f = 0.316 [Re.sup.-0.25] for < 2 x [10.sup.4], (15)
f = 0.184 [Re.sup.-0.20] for < 2 x [10.sup.4] < Re < 3 x
[10.sup.5]. (16)
The Air flow rate in the 8 mm aerofoil plate is nearly equal in
both Experimental and Analytical methods are shows in the Table 1.
3.3. Statistical analyses ANOVA using two way method
It is convenient to use the following computational formula for
finding the various sums of squares numerically.
Total sum of squares is:
SST = [[summation].sub.j] [[summation].sub.i] [y.sup.2] ji
-correction factor, (17)
where correction factor [c.sup.2]/N .
Between treatment sum of squares:
[R.sub.1] = [[summation].sub.j] [T.sup.2.sub.i]/r - correction
factor. (18)
Between block sum of squares:
[R.sub.2] = [[summation].sub.j] [B.sup.2.sub.i]/K - correction
factor (19)
Error sum of squares [SS.sub.error] = SST - [R.sub.1] - [R.sub.2].
[F.sub.1] < F(5,10) reject [H.sub.01] and conclude that there is
no significant effect due to difference in speeds. and [F.sub.2] > F
(2,10) accept [H.sub.02] and conclude that there is no significant
effect due to difference in Manifold models shows in the Table 2.
4. Conclusions
The analysis of the air and fuel flows in-cylinder internal
combustion engine utilizing different thickness of aerofoil plate, the
following conclusions were drawn:
The overall in-cylinder tumble flows are much dependent on the
Aerofoil plate thickness with irrespective of engine speed. It is
suggested to utilize the aero dynamical Aerofoil plate rather than flat
Aerofoil plate as far as tumble flows are concerned. The quantity of
molecules entering the in-cylinder is reduced perpetually with
incrementing the thickness of Aerofoil plate thick.
This is due to a reduction in the area of the inlet manifold so
that, the 8mm thick aerofoil plate, gives the result of drag coefficient
as 0.21. This is the best result as compared to the other aerofoil
plate. But as the airfoil plate thickness increases above 10mm, it may
be blocks the flow of the air fuel mixture.
It is suggested to utilize, the 8mm thickness of aerofoil plate
utilized in the inlet manifold, less amount of emission emitted to the
atmosphere such that volume of CO and HC (ppm) compared to other
thickness of aerofoil plate.
The two different fuel mixture concept (8mm and 10mm aerofoil plate
in the inlet modified manifold) results in the brake thermal efficiency
incremented by 2.96% and 3.36% in the both condition of speed and load.
It is additionally decrease the HC emissions were found and
approximately 120.64-118 ppm reduction is achieved with the two
different fuel mixture concept operations in both speed and loading
conditions. A significantly reduction in CO emission is approximately
0.1283%-0.147% and C[O.sub.2] emissions were observed in the two
different fuel mixture concept is 0.55 -0.78% with an incrimination in
engine performance without increase in emissions.
In future, introducing the modified aerofoil plate at inlet flow is
possible to increment turbulence kineticism, so that it increments the
efficiency and reduces the emission due to congruous commixing of flow.
http://dx.doi.org/ 10.5755/j01.mech.21.3.8685
Received November 13, 2015
Accepted April 28, 2015
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S. Rajendran *, K. Purushothaman **
* Department of Mechanical Engineering, Jaya Engineering College,
Ann University, Tamilnadu, India, E-mail: srajend1975@gmail.com
** St.Peter's College of Engineering and Technology, Anna
University, Tamilnadu, India
Table 1
Effect of pressure drop in inlet manifold
Torque N-m TFC Break power, Velocity of Reynolds friction
KW flow, m/s number factor
3.25 0.1080 0.1905 343.95 326172 0.0002
3.9 0.1021 0.2163 325.19 308381 0.0002
4.55 0.1003 0.2429 319.38 302874 0.0002
5.2 0.0921 0.2585 293.20 278048 0.0002
5.85 0.0838 0.2706 266.95 253148 0.0003
6.5 0.0780 0.2925 248.41 235569 0.0003
Torque N-m Pressure drop Power, KW Flow rate
Ap, N/[m.sup.2] Q, m/[s.sup.2]
3.25 5.8031 0.6267 0.0839
3.9 5.4866 0.5602 0.0816
4.55 5.3886 0.5404 0.0808
5.2 4.9469 0.4554 0.0774
5.85 4.5039 0.3775 0.0739
6.5 4.1911 0.3269 0.0713
Table 2
ANOVA table
Source of Degrees of Sum of squares Mean squares
variations freedom
Speed Load Speed Load
Speed in RPM 6 738.1594 738.0268 147.6319 147.6054
Manifold 2 63.2359 7.3171 31.6179 3.6586
model
Error 10 135.6909 121.2063 13.5691 12.1206
Total 17 937.0862 866.5502 -- --
Source of Variance ratio
variations
Speed Load
Speed in RPM 10.88 12.178
Manifold 2.3301 0.3018
model
Error -- --
Total -- --
