Methods and Apparatus for Pressure Based Mass Flow Ratio Control

Patent metadata

Field	Value
Publication number	US-2021263541-A1
Application number	US-202016800363-A
Country	US
Kind code	A1
Filing date	Feb 25, 2020
Priority date	Feb 25, 2020
Publication date	Aug 26, 2021
Grant date	—

Abstract

A system and method for dividing a single mass flow into secondary flows of a desired ratio. The system and method include paths for the secondary flows that include a laminar flow element and two pressure sensors. The nonlinear relationship between flow and pressure upstream and downstream of the laminar flow elements can be transformed into a function comprised of the upstream and downstream pressure that has a linear relationship with the flow. This transformation allows for flow ratio control applications using signals from pressure sensors even if there is no information the fluid species and the flow rate into the flow ratio controller.

First claim

What is claimed is:

1 . A system for dividing a single mass flow into secondary flows comprising:
an inlet configured to receive an inlet flow; secondary flow lines connected to the inlet, each secondary flow line including:
a flow path configured to carry a secondary flow with a secondary flow rate;
an upstream pressure sensor configured to provide an upstream pressure signal representative of an upstream pressure;
a downstream pressure sensor configured to provide a downstream pressure signal representative of a downstream pressure;
a pressure drop element in the flow path downstream from the upstream pressure sensor and upstream from the downstream pressure sensor configured to create a linear response between the secondary flow rate and a function of the upstream pressure and the downstream pressure; and
a valve configured to control the secondary flow rate based upon a control signal.
a controller configured to calculate a ratio of secondary flows based upon the upstream pressure signals and the downstream pressure signals and further configured to obtain a desired ratio of secondary flow rates by sending the control signal, based on the calculated ratio and the desired ratio of secondary flow rates, to the valves.

2 . The system of claim 1 wherein the pressure drop element is a laminar flow element.

3 . The system of claim 1 wherein the pressure drop element is a compressed laminar flow element.

4 . The system of claim 2 wherein the laminar flow element is one of an annulus, bundled tubes, corrugated plates, or multiple-layer plates.

5 . The system of claim 1 wherein the pressure drop element is a flow nozzle or orifice.

6 . The system of claim 1 further comprising a temperature sensor configured to measure the temperature of the inlet flow.

7 . The system of claim 1 wherein the valves are located in the flow path of the secondary flow lines upstream from the upstream pressure sensor.

8 . The system of claim 1 wherein the valves are located in the flow path of the secondary flow lines downstream from the pressure sensors.

9 . The system of claim 8 wherein a single pressure sensor is used as the upstream pressure sensor for all secondary flow lines.

10 . The system of claim 1 wherein the function of the upstream pressure and the downstream pressure is the following:
ƒ( Pu,Pd )= Pu 2 −Pd 2

where ƒ(Pu, Pd) is the function, Pu is the upstream pressure and Pd is the downstream pressure.

11 . The system of claim 1 wherein the secondary flow rates can be calculated by the following:
Q=k*ƒ ( Pu,Pa )
where Q is the secondary flow rate, ƒ(Pu, Pd) is the function of the upstream pressure and the downstream pressure, and k is a function of dimensions of the pressure drop element, fluid properties, and fluid temperature.

12 . The system of claim 11 wherein k=k(∈, d, L, mw, r, μ, T) where ∈, d, and L are the dimensions of the pressure drop element mw, r, and μ are the fluid properties, and T is the fluid temperature.

13 . The system of claim 1 wherein the secondary flow rates can be determined based on a 3D map composed of calibration points having variables Pu, Pd, and Q where Q is the secondary flow rate, Pu is the upstream pressure and Pd is the downstream pressure.

14 . A method for dividing a single mass flow into secondary flows of desired ratios, comprising;
receiving an inlet at an inlet; dividing the inlet flow into secondary flow lines connected to the inlet, each secondary flow line including:
a flow path configured to carry a secondary flow with a secondary flow rate;
an upstream pressure sensor configured to provide an upstream pressure signal representative of an upstream pressure;
a downstream pressure sensor configured to provide a downstream pressure signal representative of a downstream pressure;
a pressure drop element in the flow path downstream from the upstream pressure sensor and upstream from the downstream pressure sensor configured to create a linear response between the secondary flow rate and a function of the upstream pressure and the downstream pressure; and
a valve configured to control the secondary flow rate based upon a control signal.
determining, by a controller, a ratio of secondary flow rates based upon the upstream pressure signals, the downstream pressure signals; and obtaining a desired ratio of secondary flow rates by sending, by the controller, the control signal, based on the calculated ratio and the desired ratio of secondary flow rates, to the valves.

15 . The method of claim 14 wherein the pressure drop element is a laminar flow element.

16 . The method of claim 14 wherein the pressure drop element is a compressed laminar flow element.

17 . The method of claim 15 wherein the laminar flow element is one of an annulus, bundled tubes, corrugated plates, or multiple-layer plates.

18 . The method of claim 14 further comprising measuring the of the inlet flow using a temperature sensor.

19 . The method of claim 14 wherein a single pressure sensor is used as the upstream pressure sensor for all secondary flow lines.

20 . The method of claim 14 wherein the function of the upstream pressure and the downstream pressure is the following:
ƒ( Pu,Pd )= Pu 2 −Pd 2

where ƒ(Pu, Pd) is the function, Pu is the upstream pressure, and Pd is the downstream pressure.

21 . The method of claim 14 wherein the secondary flow rates can be determined by the following:
Q=k*ƒ ( Pu,Pa )
where Q is the secondary flow rate, ƒ(Pu, Pd) is the function of the upstream pressure and the downstream pressure, and k is a function of dimensions of the pressure drop element, fluid properties, and fluid temperature.

22 . The method of claim 21 wherein k=k(∈, d, L, mw, r, μ, T) where E, d, and L are the dimensions of the pressure drop element mw, r, and μ are the fluid properties, and T is the fluid temperature.

23 . The method of claim 14 further comprising creating a 3D map composed of calibration points having variables Pu, Pd, and Q where Q is the secondary flow rate, Pu is the upstream pressure and Pd is the downstream pressure and the controller determines the secondary flow rates can be determined based on the 3D map.

Assignees

• Mks Instr Inc

Inventors

• Ding Junhua

Classifications

• G05D11/132 Primary

  by controlling the flow of the individual components (G05D11/133 takes precedence) · CPC title

• G05D7/0682 Primary

  using a plurality of flow sources · CPC title

• G01F1/42 Primary

  Orifices or nozzles · CPC title