Effect of concave plug shape of a control valve on the fluid flow characteristics using computational fluid dynamics

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Effect of concave plug shape of a control valve on the fluid flow characteristics using computational fluid dynamics

Yasser Abdel Mohsen, Ashraf Sharara, Basiouny Elsouhily, Hassan Elgamal

Mechanical Engineering Department

Faculty of engineering –Alexandria University-Egypt

ABSTRACT: control valves are commonly used as fluid flow control equipment in many engineering applications. Thus it is more and more essential to know the flow characteristic inside the valve. Due to the fast progress of the flow simulation and numerical technique, it becomes possible to observe the flow inside a valve and to study its performance. This paper presents the modeling and simulation of a control valve. The flow system in a control valve has a complex structure and non-linear characteristics, because of its construction and the fluid flow phenomena associated with it. the three-dimensional CFD simulation is conducted to observe the fluid flow characteristics when a control valve is equipped with different concave plug shapes and different openings. Furthermore, the results of the three-dimensional analysis can be used in the design for low noise and efficiency improvement.

Keywords: flow induced valve, characteristics for flow passing throw control valve, plug geometry effect on flow passing control valve, Control valve CFD analysis, control valve plug geometry effect on its vibration, effect of valve configuration on flow passing throw valve,

INTRODUCTION

The optimum design of a control valve requires a preliminary estimation of the lift force acting on the plug for the flow passing through it. In order to solve this problem, many experimental measurements on specific valves are needed. Alternatively, a numerical analysis can be performed by means of computational fluid dynamics (CFD) codes. In previous works, the fluid forces acting on an open center directional control valve were the aim of studies the evaluation of the driving forces acting on ¾ hydraulic center directional control valve by means of computational fluid dynamic analysis are studied [1]. Macro et al. [2,3],Del Vescovo and Lippolis [4]analyzed the effects that different spool edge shapes produce on the flow force profile during the axial spool movement.

Del Vescovo et al. [5-7]analyzed the difference between the fluid dynamics behavior of a proportional valve and a traditional one. Recently, Computational Fluid Dynamics (CFD) has been experiencing rapid advances due to both computer technology progress and efficient algorithms that have been developed to solve the Navier- Stokes (N-S) equations used in the flow analysis around ship hull. The work contributed to the numerical solution of the viscous flow around ship-like bodies is discussed in [8]. The experimental and numerical works on a three-dimensional, complex geometry, control valve were performed for model validation and improved understanding of valve flow features is discussed in [9]. The compressible air flow in a typical puffer chamber with moving contact between fixed electrodes has been studied using computational fluid dynamics techniques [10]. In recent years, the valve manufacturers across the world focused their attention towards developing high

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performance control valve designs to outweigh the problems caused by the conventional control valve. Typical problems faced in the industry with conventional control valves are the vibration of the system. This vibration in the system t can be attributed to many reasons like pressure force affecting on the valve plug under the partial- valve-opening condition. In this paper, the attention has been focused on the plug control valve, and that the modeled geometry is necessarily three dimensional although the periodicity of the geometrical domain has been exploited in order to reduce the computational efforts.

Figure 1: An internal view for the valve configuration

Model description and boundary conditions and grid generation

In this section the plug with a different concave shape is describe and the grid generations require getting the best solution. And show the boundary condition used in this study.

1-Flat face plug:-

In this case a plug is used with flat faced as shown in figure 2. The plug opening is to be changed from 10% to 40%

Figure 2: flat face plug 2- Plug with concave shape no. 1

Physical Boundary

Outlet Flow Inlet Flow

Velocity

Trim Area

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In this case a plug with concave shape is considered (see figure 3). The shape follows the equation

y = 0.0067 х

2

 0.0066 х 0.026 

Figure 3: Plug with concave shape no.1

3-Plug with concave shape no. 2

In this case the plug geometry (see figure 4) follows the equation

y = 0.0053 х

2

 0.0065х 0.033 

Figure 4: plug with concave shape no.2

The Boundary condition

Symmetry boundary conditions were used at the plane of symmetry of the valve body and plug

assembly. All solid boundaries were represented assuming the no slip condition to exist. Inlet

conditions were represented by uniform velocity sufficient to provide the required large Re flow. The

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©2016 RS Publication, [email protected] Page 162 inlet velocity varies from 1m/s to 5m/s. the valve opining varies from 10% to 40%. The Body Forces are neglected. Outlet boundary condition set as with uniform pressure.

Grid generations

The grid used in the numerical study was a tetrahedral grid. After an initial investigation for the grid independence, a grid size of 40 by 25 was used. The nodes of the grid were clustered in the plug and seat region since this was the area of largest flow gradient. In addition, an effort was mad to reduce the grid distortion. Figure 5 shows the geometry of the valve body and plug arrangement and the flow field meshing.

Figure 5: Valve body and plug arrangement with field mesh

RESULTS AND DISCUSSION

Analysis of flow passing through the control valve is performed using CFD model. A flat faced plug and two plugs with the different concave shapes are considered.

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Flat faced plug

The CFD results in Fig. 6 show that the relation between the valve percent opening and lift force when the flow passing throw the valve with flat face plug with the different inlet velocities . It can be seen when the valve opening is small, the lift force is large at the same flow inlet velocity. When the valve opening is large, the lift force is small at the same flow inlet velocity. As the flow inlet velocity increases the lift force increases for the same valve opening. This means that the lift force reaches its maximum value at smallest opening for the same inlet velocity and it reaches its maximum value at highest flow inlet velocity at the same valve opening. The lift force reaches its minimum value at the large valve opening for the same flow inlet velocity.

Figure 6: Relation between lift force acting on flat faced plug and percentage valve opening for different inlet velocities

Plug with different parabolic shapes.

The relation between the lift force and valve opening for two plugs having concave shape are shown in figures 7 and 8. For all plug geometry the lift force increases when the valve opening decreases. And it also increases when the inlet velocity increases. The lift force attains its maximum value at smallest opening and it reaches its minimum value at opening 40%. After 40% opening it reaches an asymptotic value for all plug geometries. At small inlet velocity the change of lift force with valve opening is low. At high velocity inlet the change of it is high. The comparison between the previous result for flat faced plug geometry and the latter result shows that

0 500 1000 1500 2000 2500

0% 10% 20% 30% 40% 50%

lift f or ce(N )

valve opening

v=1m/s v=2m/s v=3m/s v=4m/s v=5m/s

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the lift force decreases when the concave plug geometry curvature increases. The lift force attains its maximum value for flat face plug. The lift force reaches its minimum value for the plug shape no.2

Figure 7: Relation between lift forces acting on plug with concave shape no.1 and percentage valve opening for different inlet velocities

Figure 8: Relation between lift force acting on plug with concave shape no.2 and percentage valve opening for different inlet velocities

0 200 400 600 800 1000 1200 1400 1600

0% 10% 20% 30% 40% 50%

lift f or ce(N )

valve opening

0 200 400 600 800 1000 1200 1400

0% 10% 20% 30% 40% 50%

lift f or ce ( N)

valve opening

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Examination of valve pressure contours

Figure 9-17 displays the numerical pressure contours with valves different plugs .Each valve is shown at opening 10, 20, 30, and 40 percent. In each case the pressure decreases in the downstream direction with the largest pressure gradient occurring in the plug and seat region. No significant pressure changes are observed upstream of valve only minor changes are observed downstream of the plug. The pressure changes are observed when the valve percent opening, flow inlet velocity and valve plug geometry change. At small valve opening the pressure increases around the plug region and it decrease at low inlet velocity. The pressure for flat face plug region is higher than the concave plug region and it decreases to minimum forthe concave plug no. 2.

Figure 9:

Pressure contours for flat faced plug at valve opening 10% and v=1m/s

Figure 10: Pressure contours for flat faced plug at valve opening 20% and v=3m/s

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Figure 11: Pressure contours for flat faced plug at valve opening 40% and v=5m/s

Figure 12:

Pressure contours for p1 plug at valve opening 10% and v=1m/s

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Figure 13:

Figure 14:

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Figure 15: Pressure contours for p2 plug at valve opening 10% and v=1m/s

Figure 16:

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Figure 17: Pressure contours for p2 plug at valve opening 40% and v=5m/s

CONCLUSIONS

The analysis of flow passing through the control valve using a three-dimensional model has been investigated by solving the Navier-stokes and the continuity equations using comsol CFD code. From the results it is concluded that

1- The lift force acting on the plug decreases when the plug concave shape curvature increases for constant valve opening and for the same inlet velocity.

2- The lift force acting on the plug increases when the valve opening decreases for specific plug shape and the same inlet velocity.

3- The lift force acting on the plug increases when the inlet velocity increases for the same plug shape and the same valve opening.

REFRENCES

[1] R. Amirante, G. Del Vescovo and A. Lippolis, “Evaluation of the flow forces on an open centre directional control valve by means of a computational fluid dynamic analysis.” Journal of Energy conversion and management. Vol. 47, PP. 1748-1760 (2006).

[2] Macor A,Badin D.Turbulence modeling influence on flow force analysis in hydraulic directional control valves.in :proceeding of the 54^th congress nazionle ATI, 1999 [in Italian].

[3] Macor A. Experimental analysis on a directional valve with a flat notch metering section. In: proceeding of the 57^th congresso nazional ATI, pisa, 2002 [in Italian].

[4] Del Vwscovo G, Lippolis A. Flow force analysis on an electro piloted hydraulic directional control valve. In proceeding of the 3^rd international congress Minihydro, Maratea, 2001 [in Italian]

[5] Del Vescovo G, Lippolis A. CFD analysis of flow forces on spool valves. In : Proceedings of the 1^st international confrance on computational method in fluid power technology , Melbourne November 26-28,2003;2003.

[6] Del Vescovo G,Lippolis A.Three –dimensional analysis of flow forces on directional control valves. Int J Fluid power 2003;4(2).

[7] Del Vescovo GLippolis A. flow forces analysis on a four way valve. In: proceedings of 2^nd FPN PhD international symposium, Modena, July 3-6, 2002; 2002.

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[8] S. Hayashi, T.Matsui and T. Ito, “Study of flow and thrust in nozzle-flapper valves” Journal of fluid engineer. Trans. ASME, Vol 45, PP. 39-50 (1975).

[9] K. K. Botros, G.H. Dunn and J. A. Hrycyk, “Riser-Relief valve dynamic interaction” Journal of Fluids Engineering. Vol. 119 PP. 671- 679 (1997).

[10] B. Min, F. Xin, C. Ying, Scholl Frank, “Computational fluid dynamic approach to pressure loss analysis of hydraulic spool valve”

Journal of Energy Conversion Management. Vol. 149 PP. 234-239 (2000).

Effect of concave plug shape of a control valve on the fluid flow characteristics using computational fluid dynamics

©2016 RS Publication, [email protected] Page 159