two-dimensional cfd analysis of butterfly...
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1781 WWW.IJAEGT.COM
TWO-DIMENSIONAL CFD ANALYSIS OF BUTTERFLY
VALVE CAST GATING SYSTEM
Ajay George1, Alwin Jose2, Dijin Jose3,Livin A.V4, Nirmal Sudhakaran5 , Noble Jose6, Sarath V.S7 , Tony Thomas8 and
Rafin T.A9
12345678 Mechanical Engineering, Nirmala college of engineering, Thrissur,kerala,India 9 Assistant professor ,Mechanical Engineering, Nirmala college of engineering, Thrissur,kerala,India
Abstract
The objective of a gating system is to permit
distribution of the metal to the mold cavity at the proper
rate without excessive temperature loss, free from
objectionable turbulence, entrapped gases, slag and dross.
For any newer casting, the development of the gating and
feeding system takes huge amount of time, cost as well as
man power for the manual trial. Casting modifications are
needed for the improved casting. The present study considers
gating system of butterfly valve body. In most casting
industries rectangular gating systems are used. The most
efficient gating system for butterfly valve cast body is
attained by comparing different gating system. simulation
process is done in order to find out the best gating system
for the casting. Hence study directed towards cfd simulation
process.
Keywords: Butterfly valve body, Casting Simulation,
Gating Design
1. Introduction
Designing of gating system is an important stage
in attaining quality of the product. Casting process is
based on the property of a liquid to convert its shape to
that of vessel containing it. Molten metal solidifies and
takes the shape of mold, but not exactly the same since
solid is denser there is reduction of volume. In order to
compensate for shrinkage of metal suitable provisions
should be provided. Casting is thus one of the most
versatile forms of mechanical process for producing
components, because there is no limit to the size, shape
and intricacy of the articles that can be produced by
casting Principles of casting consist of introducing the
molten metal into a cavity and mold of the desired shape
and allowing it to solidify. S.G Iron is generally used for
large casting. SG iron is a bridge between grey iron and
steel casting with combined properties of grey iron and
steel. This Iron is also called Nodular Iron and Ductile
Iron [2]. Gating system is an essential factor while
manufacturing a good casting. Gating system design is
crucial in controlling the rate and turbulence in the molten
metal being poured, the flow of liquid metal through the
gating system, and the temperature gradient within the
metal casting. Hence a good gating system will create
directional solidification throughout the casting, since the
flow of molten material and temperature gradient
determine how the metal casting solidifies
Nomenclature
cp specific heat
Fhj diffusional energy flux in direction xj
gm gravitational field components
h the turbulent diffusional flux of energy
k turbulent kinetic energy
K thermal conductivity
p Pizeometric pressure = ps − ρ0gmxm
ps static pressure
sij the rate of strain tensor
T temperature
T0 reference temperature
ui velocity component in direction xi
uj velocity component in direction xj
u fluctuations about the ensemble average
velocity
xi Cartesian coordinate (i=1, 2, 3)
xj Cartesian coordinate (j=1, 2, 3)
xm coordinates from datum, where ρ0 is defined
Greek letters
δij the “Kronecker delta”, is unity when i = j
and zero
otherwise
ε turbulent dissipation rate
μ molecular dynamic fluid viscosity
ρ density
ρ0 reference density
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1782 WWW.IJAEGT.COM
With the advancement in computational fluid dynamics
(CFD) and computer technology, it is becoming
increasingly possible to predict these complex thermal
hydraulic characteristics of FSA from fundamental
principles, i.e. by numerically solving the 3D conservation
equations of mass, momentum and energy using finite
volume method [1] with appropriate turbulence model.
2. Literature survey
B.Vijaya Ramnatha(2014) presented In this
study, a Commutator End (CE) bracket, a cold chamber
die casted product was chosen. Initially when the
component was casted numerous defects such as Cold
shuts, Misrun, Shrinkage porosity and Gas porosity were
found. This in turn led to rejection of number of
components. In order to improve the quality of the castings
produced, the gating system was changed from theexisting
flat gate to modified spoon fed gate. The component was
designed using Pro- Engineer and flow analysis was
carried out using Rotork Flow 3D Software. [4]
Harshil Bhatt(2014) presented that Casting
simulation can effectively overcome difficulties and
provide powerful tool for prediction of the process growth.
Simulation of existing feeding system provides the
locations of the points where chances of defects are high.
This information can be used to modify the feeding system
design. Feeding systems are modified and simulated unless
satisfactory results are obtained. In present paper, authors
have made an attempt to simulate various designs of
feeding system, in order to obtain optimum design. [5]
Swapnil A. Ambekar(2014) presented casting
produced by foundry with internal shrinkage as a major
defect was analyzed and identified that gating and risering
system was improperly designed. The designed gating
system reduced defect and increase yield. Finally, a more
reasonable gating system was obtained by analysis of
simulation results. [6]
3. Modeling of butterfly valve gating system
3.1. CFD modelling
The Butterfly valve body casting model with essential
elements of the gating system like ingate, runner, sprue and
risering system is created in SOLIDWORKS (CAD
modeling software). Hypermesh 13 is used for meshing. A
total of 1.4 million cells are created. Figure 1 shows the
drawing of a butterfly valve body cast and table 1 shows its
specification.
Table 1: Specification of butterfly valve body casting Volume of casting 53432268.5 mm
3
Mass of casting 400kg
Actual weight of molten metal
575kg
Pouring time 25sec
Gating ratio 4:8:3
Choke area 21.205cm2
Sprue area 28.274cm2
Diameter sprue 6cm
Ingate area 21.205cm2
Thickness of ingate 0.814cm
Width of ingate 3.25cm
Runner area 56.546cm2
Width of runner 3.75cm
Height of runner 7.52cm
Diameter of riser 1 103mm
Diameter of riser 2 140mm
Height of riser 155mm
Total weight of riser 76.66kg
Figure 1. 3-D figure of a Butterfly valve body cast
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1783 WWW.IJAEGT.COM
Figure2, 2-d drawing of gating system
Figure 3 mesh distribution in gating system
Table3 shows the different gating designs and its
dimensions. Actually the length and cross sectional area of
all the ingates are same.
3.2Governing equations
The equations that govern the fluid flow and heat transfer
process are as follows [3].
Continuity
(1)
Momentum
(2)
Where
ENERGY
(3)
Where
Turbulence is modelled by the standard k–ε model
(Launder and Spalding, 1974).
Turbulent kinetic energy
= (4)
Turbulent dissipation rate:
(5)
3.3 Boundary conditions The boundary conditions imposed on Equations (1)– (5).
The inlet velocity and temperature of sg-iron are .7671 m/s
and 1370K. The density and viscosity of sg-iron are 7500
kg/m3 and 0.0035kg/ms.
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1784 WWW.IJAEGT.COM
Table 3: Gating designs
GATE
GATING DESIGN
DIMENSIONS
A
B
C
4. Results and discussion
4.1 Contours of Static pressure Figure 4 shows contours of static pressure in GATE1. Here
the pressure is maximum at the inlet and gate area.
Pressure is then decreases from inlet to outlet.
Figure 4, Contours of static pressure in GATE 1
Figure 5 shows contours of static pressure in GATE2. Here
the pressure at the inlet and gate area are higher compared
to GATE1 and GATE3.
Figure5, Contours of static pressure in GATE2
Figure 6 shows contours of static pressure in GATE3. Here
the pressure at the inlet and gate area are higher than
GATE1 and lower than GATE2.
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1785 WWW.IJAEGT.COM
Figure6, Contours of static pressure in GATE 3
There is no negative pressure is created in these three
gating system throughout the gate area. Pressure created in
the GATE2 is higher compared to GATE1 and GATE3.
Figure5 shows the pressure distribution with respect to
distance of three gating system.
Figure7, Pressure distribution of gate1,gate2 and gate3
In figure 7 X-axis shows the distance of gate and Y-axis
shows the pressure. By comparing the pressure created in
these three gating system it is clear that Gate 2 is having
maximum pressure throughout the gate. Gate 1 reaches
more pressure compared to Gate3. Gate 3 is having
minimum pressure. So that gate 2 is better compared to
Gate1 and Gate3 in terms of pressure.
While considering the pressure analysis, consider the inlet
pressure. It is found that GATE2 provides a lesser pressure
drop compared to other gates. GATE1 makes 29.411% and
GATE3 makes 36.36% but GATE2 makes only 23.52%
pressure drop. While compare GATE1 and GATE2,
GATE2 provides 20% more pressure at inlet than GATE1,
but comparing GATE1 and GATE3, then GATE3 makes
19.117% pressure drop. Based on pressure analysis
GATE2 is suitable.
4.2 Contours of velocity magnitude
Figure 8 shows contours of velocity magnitude in GATE1.
Here the velocity is maximum at the gate area. Velocity is
then decreases from gate area to outlet. In GATE1 velocity
created in the gate area is lower than GATE2 and GATE3.
Figure 8, Velocity magnitude in GATE1
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1786 WWW.IJAEGT.COM
Figure 9 shows contours of velocity magnitude in GATE2.
In GATE2 velocity created in the gate area is higher than
GATE1 and GATE2.
Figure 9, Velocity magnitude in GATE2
Figure 10 shows contours of velocity magnitude in GATE3.
In GATE3 velocity created in the gate area is higher than
GATE1 and lower than GATE2..
Figure 10, Velocity magnitude in GATE3
Velocity formed in gate 2 is higher compared to gate1 and
gate3. Figure 11 shows the velocity with respect to
distance of three gating system.
Figure 11, velocity distribution of GATE1,GATE2 and GATE3
In figure X-axis shows the distance of gate and Y-axis
shows velocity of molten metal. Gate 2 attains maximum
velocity. Gate 3 is having higher velocity than gate 1. So
that gate 2 is better in terms of velocity.
While considering the velocity analysis, consider the outlet
velocity. It is found that the GATE2 makes only 11.25%
velocity drop, but GATE1 makes 15 % and C makes
14.75% velocity drop which is more than that GATE2.
While comparing GATE1 and GATE2, GATE2 provides
25% more velocity at the outlet, but comparing GATE1
and GATE3, GATE3 makes only 1.6% velocity increase at
the outlet. Thus, based on velocity analysis also GATE2 is
suitable.
5. Conclusions 2-D component models was developed using
CAD software SOLIDWORKS.
Simulation process is done using ANSYS 14.5 to
evaluate which gating system is efficient for sand
casting of Butterfly valve body cast.
Three gating systems were examined through
simulation and an optimized design was chosen
through this process.
Gate 2 is having higher pressure.
Gate 2 is having higher velocity.
A new gating system was designed so that the
molten metal flows into the die cavity with
uniform filling.
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-4, Issue-2, March 2016
1787 WWW.IJAEGT.COM
The negative pressure at the gate entry due to
which turbulence was caused is also rectified.
Acknowledgement This paper is the result of hard work of authors with the
help from many sources. We express our gratitude and
sincere thanks to college management and all the faculties
of the department of mechanical engineering, Nirmala
College of Engineering.
References [1] Patankar, S.V., 1980. Numerical Heat Transfer and
Fluid Flow. McGraw-Hill,New York.
[2] R. PALANIVELU “Gating and risering of ferrous
casting”-The institute of Indian foundry men.
[3] Hughes, W.F., Gaylord, E.W., 1964. „Basic Equations
of Engineering Science‟.
Schaum‟s Outline Series. McGraw-Hill, New York
[4] B. Vijaya Ramnatha “Analysis and Optimization of
Gating System for Commutator End Bracket”-3rd
International Conference on Materials Processing and
Characterisation (ICMPC 2014)
[5] Harshil Bhatt “Design Optimization of Feeding System
and Solidification Simulation for Cast Iron”-2nd
International Conference on Innovations in Automation
and Mechatronics Engineering, ICIAME 2014.
[6] Swapnil A. Ambekar “A Review on Optimization of
Gating System for Reducing Defect”-International Journal
of Engineering Research and General Science Volume 2,
Issue 1, January 2014).