Flow regulating control valve and method for regulating fluid flow

#This invention relates generally to the field of fluid flow and, more specifically, to a flow regulating control valve and method for regulating fluid flow.

#Fluid valves are used extensively in industry for many applications. An example is the use of fluid valves in heat exchanging systems in buildings for heating or cooling purposes. In many applications, it is often desirable to maintain a constant flow rate through a fluid valve despite fluctuations that may occur in the pressure of the upstream or downstream fluid. It is also desirable in some instances to be able to adjust the flow rate through a valve.

#Some prior valves achieve a constant flow by attempting to maintain a constant differential pressure across a control orifice by allowing the differential pressure to act on a piston opposed by an elastic member of nearly constant force. The motion of said piston controls the size of a throttling restriction, which is placed downstream of the control orifice. A consequence of this is that an edge of the piston adjacent the throttling restriction is acted upon by the downstream pressure, which is lower than either of the pressures affecting the intended regulation. This lower pressure tends to cause the throttling restriction to close further than it should for proper regulation, resulting in a lower flow than intended. The dynamic forces arising from the flow of the fluid tend to further lower the pressure acting on the throttling restriction due to Bernoulli's principle. The error becomes greater as the total pressure differential across the device increases. This phenomenon is referred to as “sag” and various attempts have been made to limit its effect. Such previous attempts, however, have worked correctly only for a particular flow rate, as is the case of the special pattern of openings disclosed in U.S. Pat. No. 4,080,993 entitled In-Line Flow-Control Valve, to Charles F. Lind.

#For a more complete understanding of the invention, and for further features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is a block diagram of a flow regulating control valve having a throttling orifice positioned upstream from a control orifice according to one embodiment of the present invention;

#FIG. 2A is a cross-sectional view of one embodiment of the flow regulating control valve in FIG. 1 illustrating a piston in a first position;

#Example embodiments of the present invention and their advantages are best understood by referring now to FIGS. 1 through 5B of the drawings, in which like numerals refer to like parts.

#FIG. 1 is a block diagram of a flow regulating control valve 100 according to one embodiment of the present invention. Control valve 100 receives fluid from an upstream region 102 and transports it to a downstream region 104. Control valve includes a throttling orifice 108, a control orifice 110, and an intermediate region 103 disposed between the throttling orifice 108 and control orifice 110. Although not explicitly illustrated in FIG. 1, control valve 100 includes other components, as described in greater detail below. Any suitable fluid flows in the direction of arrow 106 from upstream region 102 to downstream region 104.

#According to the teachings of the present invention, throttling orifice 108 is positioned upstream from control orifice 110 as opposed to prior control valves that have the control orifice upstream from the throttling orifice. Both throttling orifice 108 and control orifice 110 are described in greater detail below. However, generally, throttling orifice 108 is adapted to dynamically change in size in response to a change in a pressure of a fluid in upstream region 102, and control orifice 110 is set to a predetermined size to regulate a flow rate of the fluid flowing through control valve 100. A reduction in pressure due to velocity of fluid through throttling orifice 108 may be used to balance the higher pressure in upstream region 102. Having throttling orifice 108 positioned upstream from control orifice 110 addresses the deleterious effects of the pressure of the fluid in downstream region 104 on the control of the flow rate of the fluid, as described below. Such an effect is known conventionally as “sag.” Some embodiments of the present invention may also reduce the risk of cavitation because a larger pressure drop across throttling orifice 108 occurs before a smaller pressure drop across control orifice 110.