CAD2D3D

1 什么是阀门流量系数（Cv）？

Valve Flow Coefficient (Cv) is a valve’s capacity for a liquid or gas to flow through it.
阀门流量系数（Cv）是指液体或气体流过阀门的能力。

It is technically defined as “the volume of water at 60°F (in US gallons) that will flow through a valve per minute with a pressure drop of 1 psi across the valve.”
流量系数Cv的定义：在60°F（以美国加仑计）下，阀门上的压降为1 psi 时，每分钟流过阀门的水的体积。

In simpler terms, the larger the opening in a valve, the larger the Cv. As a valve is opening, the Cv increases until the valve is fully open, where it reaches its highest possible Cv, or 100% open Cv.
简单地说，阀中的开口越大，Cv越大。当阀门打开时，Cv增加，直到阀门完全打开，在那里它达到其最高可能的Cv，或100%打开Cv。

流量系数Cv实例

Below is a Valve Cv chart showing flow curves for two different valves: a 2-inch and 3-inch Kimray back pressure regulator.
下面是一个阀门Cv图表显示两个不同的阀门流量曲线：2英寸和3英寸Kimray背压调节器。

As the stem opens, the Cv increases.随着阀杆打开，Cv增加。

The maximum Cv for the 2-inch regulator is 47, while the maximum for the 3-inch regulator is 117.
2英寸调节器的最大Cv为47，而3英寸调节器的最大Cv为117。

We recommend you select a valve for which the Cv falls between 20% and 80% open stem travel.
我们建议你选择的阀门Cv值落在20%~80%阀杆行程之间。

For example例如：

If you used our valve sizing calculator and came up with a Cv value of 14, you would want to choose the 2-inch valve because in the 3-inch valve, 14 would fall outside of the recommended range. 
如果您使用我们的阀门通径计算器得出的Cv值为14，您会希望选择2英寸阀门，因为在3英寸阀门中，14将超出推荐范围。

If you calculated a Cv value of 47, you would want to choose the 3-inch valve because in the 2-inch, 47 would fall outside of our recommended range. 
如果您计算的Cv值为47，您将希望选择3英寸阀，因为在2英寸中，47将超出我们的推荐范围。

If you calculated a Cv of 35, it falls in the range for both valves. In this case we would recommend the 3-inch because it falls closer to the middle of the flow curve.
如果计算出的Cv为35，则其福尔斯在两个阀的范围内。在这种情况下，我们会推荐3英寸，因为它福尔斯下降更接近中间的流量曲线

2 HOW TO SIZE A CONTROL VALVE 如何确定调节阀的尺寸？

1）The first question you need to ask when valve sizing is “What is my pressure?”
当阀门选型时，您需要问的第一个问题是“我的压力是多少？”

2）THE IMPORTANCE OF CALCULATED Cv
计算CV的重要性

参考文献：https://kimray.com/training/what-valve-flow-coefficient-cv