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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

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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

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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.

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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.

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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

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In GATE2 velocity created in the gate area is higher than

GATE1 and GATE2.



In GATE3 velocity created in the gate area is higher than

GATE1 and lower than GATE2..


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.

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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).

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TWO-DIMENSIONAL CFD ANALYSIS OF BUTTERFLY …ijaegt.com/wp-content/uploads/2016/01/IJAEGT-pp-1781-1787-Ajay... · TWO-DIMENSIONAL CFD ANALYSIS OF BUTTERFLY VALVE CAST GATING SYSTEM