Methods and apparatus for pressure based mass flow ratio control

Patent metadata

Field	Value
Publication number	US-11940307-B2
Application number	US-202117342341-A
Country	US
Kind code	B2
Filing date	Jun 8, 2021
Priority date	Jun 8, 2021
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

A system and method for dividing a single mass flow into secondary flows of desired ratios to total flow. Each secondary flow line includes a pressure drop element, an absolute pressure sensor and a differential pressure sensor. The nonlinear relationship between flow and pressures can be transformed into a function of the absolute and differential pressures that has a linear relationship with the flow.

First claim

What is claimed is:

1. A system for dividing a 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 from the inlet with a secondary flow rate;
a pressure drop element in the flow path;
a valve configured to control the secondary flow rate based upon a control signal;
a pressure sensor upstream of the pressure drop element configured to provide a pressure signal representative of pressure at the pressure drop element; and
a differential pressure sensing element in communication with pressures upstream and downstream of the pressure drop element and configured to provide a differential pressure signal representative of differential pressure across the pressure drop element; and

a controller configured to calculate a secondary flow rate of each secondary flow line based upon the pressure signal and the differential pressure signal and further configured to generate the control signal to each valve to obtain a desired ratio of secondary flow rate to total flow rate, wherein the controller is configured to compute and control the ratio of each secondary flow rate according to the relationship,

r
i

=

Q
i

Q
t

=

Q
i

∑

j
=
1

N

⁢

Q
j

=

k
i

*

(

2
⁢

P

u
,
i

-

DP
i

)

*

DP
i

∑

j
=
1

N

⁢

k
j

*

(

2
⁢

P

u
,
j

-

DP
j

)

*

Dp
j

,

i
=
1

,
2
,

…
⁢

N
.

wherein r i is the ratio between each secondary flow rate Q and the inlet flow rate Q t , k is a constant, P u is the pressure signal representative of pressure at the pressure drop element, and DP is differential pressure signal representative of differential pressure across the pressure drop element.

2. The system of claim 1 wherein the differential pressure element comprises a diaphragm exposed at one face to the pressure upstream of the pressure drop element and exposed on an opposite face to the pressure downstream of the pressure drop element.

3. The system of claim 1 wherein the pressure sensor is upstream of the pressure drop element and the valve is downstream of the pressure drop element in each secondary flow line.

4. The system of claim 3 wherein the upstream pressure sensor of each flow line is a common pressure sensor shared by all secondary flow lines.

5. The system of claim 1 wherein the valve is positioned upstream of the pressure drop element.

6. The system of claim 5 wherein the pressure sensor is positioned between the valve and the pressure drop element.

7. The system of claim 1 wherein the pressure drop element is configured to create a linear response between the secondary flow rate and a function of the pressure at the pressure drop element and the differential pressure across the pressure drop element.

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

9. The system of claim 1 further comprising a temperature sensor configured to measure the temperature of the fluid in each secondary flow line.

10. A method of dividing a mass flow into secondary flows of desired ratios comprising:
receiving an inlet flow 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;
a pressure drop element in the flow path;
a valve configured to control the secondary flow rate based upon a control signal;
a pressure sensor upstream of the pressure drop element configured to provide a pressure signal representative of pressure at the pressure drop element; and
a differential pressure sensing element in communication with pressures upstream and downstream of the pressure drop

Assignees

• Mks Instr Inc

Inventors

• Ding Junhua

Classifications

• G01F1/372 Primary

  with electrical or electro-mechanical indication · CPC title

• G01F1/86

  Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure · CPC title

• G05D7/0652

  the plurality of throttling means being arranged in parallel · CPC title

• G05D11/132 Primary

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

• G05D7/0664

  the plurality of throttling means being arranged for the control of a plurality of diverging flows from a single flow (G05D7/0652 takes precedence; ratio control G05D11/13) · CPC title