System and method for measuring flow

• US 7,150,201 B2
• Filed: 12/15/2004
• Issued: 12/19/2006
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Celerity Incorporated (ICHOR Holdings, Ltd.)
• Inventors: Lu, Shiliang, Tison, Stuart A.
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US11/012,750
• Publication Number:
  US 20060123920A1
• Time in Patent Office: 734 Days
• Field of Search: 738/610.1, 731/95, 731/96, 731/97, 731/98
• US Class Current: 73/861
• CPC Class Codes: G01F 7/005 by measuring pressure or differential pressure, created by the use of flow constriction

Abstract

One embodiment of the present invention can comprise a primary flow measurement system, a secondary flow measurement system in fluid communication with the primary flow measurement system and a control coupled to the primary flow measurement system and the secondary flow measurement system. The controller can comprise a processor and a memory accessible by the processor. The processor can execute computer instructions stored on the memory to calculate a flow rate using the primary flow measurement system, in a first mode of operation, and calculate the flow rate using the secondary flow measurement system, in a second mode of operation. The computer instructions can be further executable to switch between the first mode of operation and the second mode of operation based on a predefined parameter.

Claims

1. A system of determining a flow rate of a fluid comprising:

a constant volume chamber;

a sonic nozzle in fluid communication with the constant volume chamber;

one or more valves configured to direct a flow of a fluid to the constant volume chamber and the sonic nozzle;

sensors configured to read one or more parameters of the fluid; and

a controller coupled to the sensors configured to receive measurements from the sensors, the controller comprising;

a processor;

a memory accessible by the processor, the memory storing a set of computer instructions comprising instructions executable by the processor to;

in a first mode of operation, calculate the flow rate as fluid accumulates in the constant volume chamber; and

in a second mode of operation, calculate the flow rate as the fluid flows through the sonic nozzle; and

switch between the first mode of operation and the second mode of operation after a delay to allow the constant volume chamber to equilibrate.

2. The system of claim 1, wherein, in the first mode of operation, the flow rate is calculated based on the change in pressure over time of the fluid.

3. The system of claim 2, wherein the flow rate is approximately calculated according to

4. The system of claim 1, wherein, in the second mode of operation, the flow rate is calculated based on a fluid pressure.

5. The system of claim 4, wherein, in the second mode of operation, the flow rate is approximately calculated according to

6. The system of claim 1, wherein, in the second mode of operation, the flow rate is calculated based on a fluid density.

7. The system of claim 6, wherein, in the second mode of operation, the flow rate is approximately calculated according to

8. The system of claim 1,

wherein said one or more valves are further configured to regulate the flow through the system;

and

wherein the computer instructions further comprise instructions executable to control said one or more valves to regulate the flow.

9. The system of claim 8, wherein said one or more valves comprise:

a first valve downstream of the constant volume chamber; and

a second valve downstream of the sonic nozzle.

10. The system of claim 1, wherein the flow rate comprises a mass flow rate.

11. The system of claim 1, wherein the flow rate comprises a volumetric flow rate.

12. The system of claim 1, wherein the computer instructions are executable to switch between the first mode of operation and the second mode of operation based on a predefined parameter.

13. The system of claim 1, wherein the sonic nozzle is a variable orifice sonic nozzle.

14. A method of determining a flow rate of a fluid comprising:

for a first mode of operation, calculating the flow rate as fluid accumulates in a constant volume chamber for a first range of flow rates; and

for a second mode of operation, calculating the flow rate as the fluid flows through a sonic nozzle;

delaying to allow the constant volume chamber to equilibrate; and

switching between the first mode of operation and the second mode of operation.

15. The method of claim 14, wherein, in the first mode of operation, the flow rate is calculated based on the change in pressure over time of the fluid.

16. The method of claim 15, wherein, in the first mode of operation, the flow rate is approximately calculated according to

17. The method of claim 14, wherein, in the second mode of operation, the flow rate is calculated based on a fluid pressure.

18. The method of claim 17, wherein, in the second mode of operation, the flow rate is approximately calculated according to

19. The method of claim 14, wherein, in the second mode of operation, the flow rate is calculated based on a fluid density.

20. The method of claim 19, wherein, in the second mode of operation, the flow rate is approximately calculated according to

21. The method of claim 14, further comprising:

controlling one or more valves to regulate the flow to the constant volume chamber and sonic nozzle.

22. The method of claim 14, wherein the flow rate comprises a mass flow rate.

23. The method of claim 14, wherein the flow rate comprises a volumetric flow rate.

24. A system of determining a flow rate of a fluid comprising:

a constant volume chamber;

a sonic nozzle in fluid communication with the constant volume chamber;

one or more valves configured to direct a flow of a fluid to the constant volume chamber and the sonic nozzle;

sensors configured to read one or more parameters of the fluid; and

a controller coupled to the sensors configured to receive measurements from the sensors, the controller comprising;

a processor;

a memory accessible by the processor, the memory storing a set of computer instructions comprising instructions executable by the processor to;

in a first mode of operation, calculate the flow rate as fluid accumulates in the constant volume chamber; and

in a second mode of operation, calculate the flow rate as the fluid flows through the sonic nozzle;

switch between the first mode of operation and the second mode of operation;

calculate the flow rate according to the first mode of operation in an overlap range of flow rates; and

calculate a cross sectional area of the sonic nozzle based on the flow rate calculated according to the first mode of operation.

25. The system of claim 24, wherein the cross sectional area of the sonic nozzle is approximately calculated according to

26. The system of claim 24, wherein the cross sectional area of the sonic nozzle is approximately calculated according to

27. A system of determining a flow rate of a fluid comprising:

a constant volume chamber;

a sonic nozzle in fluid communication with the constant volume chamber;

one or more valves configured to direct a flow of a fluid to the constant volume chamber and the sonic nozzle;

sensors configured to read one or more parameters of the fluid; and

a controller coupled to the sensors configured to receive measurements from the sensors, the controller comprising;

a processor;

a memory accessible by the processor, the memory storing a set of computer instructions comprising instructions executable by the processor to;

in a first mode of operation, calculate the flow rate as fluid accumulates in the constant volume chamber; and

in a second mode of operation, calculate the flow rate as the fluid flows through the sonic nozzle;

switch between the first mode of operation and the second mode of operation;

calculate the flow rate according to the first mode of operation in an overlap range; and

calculate a heat capacity ratio of the fluid based on the flow rate calculated according to the first mode of operation.

28. The system of claim 27, wherein the heat capacity ratio is approximately calculated according to

29. The system of claim 27, wherein the heat capacity ratio is approximately calculated according to

30. A method of determining a flow rate of a fluid comprising:

for a first mode of operation, calculating the flow rate as fluid accumulates in a constant volume chamber for a first range of flow rates; and

for a second mode of operation, calculating the flow rate as the fluid flows through a sonic nozzle;

switching between the first mode of operation and the second mode of operation;

calculating the flow rate according to the first mode of operation in an overlap range of flow rates; and

calculating a cross sectional area of the sonic nozzle based on the flow rate calculated according to the first mode of operation.

31. The method of claim 30, wherein the sonic nozzle is a variable orifice sonic nozzle.

32. The method of claim 30, wherein the cross sectional area of the sonic nozzle is approximately calculated according to

33. A method of determining a flow rate of a fluid comprising:

for a first mode of operation, calculating the flow rate as fluid accumulates in a constant volume chamber for a first range of flow rates; and

for a second mode of operation, calculating the flow rate as the fluid flows through a sonic nozzle;

switching between the first mode of operation and the second mode of operation

calculating the flow rate according to the first mode of operation in an overlap range; and

calculating a heat capacity ratio of the fluid based on a the flow rate calculated according to the first mode of operation.

34. The method of claim 33, wherein the heat capacity ratio is approximately calculated according to

35. The method of claim 33, wherein the heat capacity ratio is

approximately calculated according to