CLC number: TK284.2

On-line Access: 2013-01-31

Received: 2012-06-14

Revision Accepted: 2012-11-13

Crosschecked: 2013-01-23

Cited: 17

Clicked: 7840

Zhi-jiang Jin, Lin Wei, Li-long Chen, Jin-yuan Qian, Ming Zhang. Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve[J]. Journal of Zhejiang University Science A, 2013, 14(2): 137-146.

@article{title="Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve",

author="Zhi-jiang Jin, Lin Wei, Li-long Chen, Jin-yuan Qian, Ming Zhang",

journal="Journal of Zhejiang University Science A",

volume="14",

number="2",

pages="137-146",

year="2013",

publisher="Zhejiang University Press & Springer",

doi="10.1631/jzus.A1200146"

}

%0 Journal Article

%T Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

%A Zhi-jiang Jin

%A Lin Wei

%A Li-long Chen

%A Jin-yuan Qian

%A Ming Zhang

%J Journal of Zhejiang University SCIENCE A

%V 14

%N 2

%P 137-146

%@ 1673-565X

%D 2013

%I Zhejiang University Press & Springer

%DOI 10.1631/jzus.A1200146

TY - JOUR

T1 - Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

A1 - Zhi-jiang Jin

A1 - Lin Wei

A1 - Li-long Chen

A1 - Jin-yuan Qian

A1 - Ming Zhang

J0 - Journal of Zhejiang University Science A

VL - 14

IS - 2

SP - 137

EP - 146

%@ 1673-565X

Y1 - 2013

PB - Zhejiang University Press & Springer

ER -

DOI - 10.1631/jzus.A1200146

**Abstract: **In this paper, a new pressure reducing valve (PRV) with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are composed of the continuity, momentum, energy and

**
**

1. Introduction

The new high parameter PRV (Fig.

Most previous studies on valves were based on experiments and mathematical models, which were time-consuming but provided reliable results. Amini and Owen (

With the booming development of computers, the finite element method has generally been applied to research on fluid flow, since it can give a clear insight into the physics of the flow. Also, the accuracy of numerical simulation methods has been validated with experimental data (Kim et al.,

This paper uses a numerical simulation method to investigate the PRV internal flow field to reveal the mechanisms of pressure reduction and energy conversion, and proposes a structure improvement method to reduce energy loss in the PRV. The governing equations for the internal flow numerical simulation include the continuity, momentum, energy and

2. Mathematical model

Continuity equation:

Momentum equation:

Energy equation:

The turbulent kinetic energy,

The effective turbulent viscosity,

The

For compressible flows, the gas law is as follows:

3. Mesh and boundary conditions

Then valve openings of 20%, 40%, 60%, 80% and 100% were analyzed. Taking the 60% opening as an example, Fig.

The flow field was divided into six parts: four parts were meshed with structured grid while the other two were meshed with unstructured grid. The mesh quality was rigorously checked for parameters such as skewness and aspect ratio. Grid independence was also checked (Fig.

For the 3D simulations, the boundary conditions were:

(a) Inlet: on this surface, the total pressure value was set to 1×10

(b) Outlet: on this surface, the static pressure value was set to 1×10

(c) Wall: except for the inlet, outlet and symmetry planes, other surfaces were wall surfaces. No-slip boundary condition was assumed.

An ideal compressible gas model was used and the energy equation was activated. According to the geometric parameters and physical properties of steam under working status, the Reynolds number is higher than 10

4. Results and discussion

In this work, different outlet pressure models were built to investigate the phenomenon of choked flow. Fig.

As the valve opening increases, the maximum point of the pressure gradient transfers from the valve plug to the orifice plate (Fig.

The steam pressure changes along the

Fig.

Based on the principles of fluid mechanics, when fluid passes through place such as the orifice plate where section suddenly narrows or expands, the flow direction changes and mechanical energy reduces. To solve this problem, we have improved the structure of the orifice plate: a cross section of gradual change is used instead of a section of sudden change, and the height of the orifice plate is increased.

Taking the 60% opening as an example, the improved streamline is shown in Fig.

Fig.

In the throttling components, the steam pressure decreases and density increases so, according to Eq. (

Because the superheated steam has to cool to saturated temperature before it releases evaporation enthalpy, the heat quantity of cooling to saturated temperature is small compared with the evaporation enthalpy of the saturated steam. Although superheated steam is convenient for transportation in a pipeline, it is rarely used in industrial processes of heat transfer. In practical applications, a temperature reducing device is usually arranged after the PRV.

With a high pressure ratio, choked flow occurs in the valve and steam flow is transonic.

The execution element valve plug and orifice plate could work together to play a throttling role and reduce steam pressure. When the opening is large, the effect of the orifice plate on throttling is more significant.

A mass of eddies exists in the cavity after the valve plug and the outlet cavity. The flow channel is blocked and part of the mechanical energy is consumed by those eddies. Especially at the perforated plate, the turbulent dissipation rate is relatively high.

By gradually changing the section and increasing the height of the orifice plate, the consumption of mechanical energy is reduced. To further improve the flow state, the size and number of the orifices could also be changed.

The internal steam is in a state of overheating and does not condense. But if the degree of superheating at the inlet is relatively small, condensation may appear in the valve. After the throttling process, the degree of superheating of the steam increases.

* Project (No. 2012C11018-1) supported by the Science and Technology Department of Zhejiang Province, China

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