| 主权项 |
1. A pressure-independent flow rate controller assembly, comprising:
a flow inlet and a flow outlet through which fluid flows, wherein fluid pressure at the flow inlet is an inlet pressure (P1) and the fluid pressure at the flow outlet is an outlet pressure (P3); an interior chamber with first and second chamber portions and a balance channel adjacent to the second chamber portion; an intermediate passageway interconnecting the flow outlet to the first chamber portion; a spring-biased piston slideably disposed in the interior chamber and having first and second piston portions axially spaced apart from each other by an intermediate space therebetween, wherein fluid is blocked from moving relative to the piston between the first chamber portion and the intermediate space and from moving relative to the piston between the intermediate space and the second chamber portion, and wherein the pressure of the fluid in the intermediate space being substantially at the outlet pressure (P3); a first throttling assembly having a first throttling seat with a throttling channel that receives fluid substantially at the inlet pressure (P1), the throttling channel configured to direct fluid toward the first chamber portion, and the first throttling assembly having a first throttling member coupled to the first chamber portion and to the piston, the first throttling member having an end portion shaped to mate with the throttling seat, the end portion having a first area against which fluid at the inlet pressure (P1) acts, the first throttling member being movable relative to the throttling seat to allow the fluid to flow into the first chamber portion, wherein fluid in the first chamber portion and in the intermediate passageway is at an intermediate pressure (P2) less than the inlet pressure (P1) and greater than the outlet pressure (P3), and wherein the intermediate passageway is in fluid communication with the second chamber portion and fluid in the second chamber portion is at the intermediate pressure (P2); a balance member coupled to the piston and having a fluid-acting surface with an area substantially equal to the first area of the end portion of the first throttling member, wherein fluid at the inlet pressure (P1) acts on the fluid acting surface to balance the fluid pressure acting on the end portion of the first throttling member; an adjustable restriction assembly configured to allow the fluid from the intermediate passageway to flow at a selected constant flow rate toward the flow outlet at the outlet pressure (P3), wherein the selected constant flow rate is independent of a pressure differential between the outlet pressure (P3) and the inlet pressure (P1); and a second throttling assembly configured to receive the flow of fluid from the adjustable restriction assembly, the second throttling assembly having second throttling member coupled to a spring biased piston and having a second throttling seat configured to receive the flow of fluid from the adjustable restriction assembly in an under-then-over trim configuration. |
