System and method for measuring flow
View Patent ↗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.
1. A system for determining a flow rate of a fluid, comprising:
a primary flow measurement system;
a first flow passage to direct fluid from a fluid source to the primary flow measurement system;
a secondary flow measurement system in parallel with the primary flow measurement system;
a second flow passage to direct fluid from the fluid source to the secondary flow measurement system;
a controller coupled to the primary flow measurement system and the secondary flow measurement system, 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:
determine a flow rate using the primary flow measurement system; and
determine the flow rate using the secondary flow measurement system.
2. The system of claim 1 , wherein the set of computer instruction further comprise instructions executable to:
switch between a first mode of operation for determining the flow rate and a second mode of operation for determining the flow rate;
wherein in the first mode of operation the computer instructions are executable to determine the flow rate using the primary flow measurement system and in the second mode of operation to determine the flow rate using the secondary flow measurement system.
3. The system of claim 1 , wherein the primary flow measurement system is one of a constant volume system, a constant pressure system, or a gravimetric flow measurement system.
4. The system of claim 3 , wherein the secondary flow measurement system is one of a sonic nozzle system, a laminar flow meter, an ultrasonic flow meter, a coriolis flow meter, or a thermal mass flow meter.
5. A system of determining a flow rate of a fluid comprising:
a constant volume chamber;
a sonic nozzle in parallel 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 in the system; 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:
determine the flow rate based on the one or more parameters of the fluid as the fluid accumulates in the constant volume chamber; and
determine the flow rate as the fluid flows through the sonic nozzle.
6. The system of claim 5 , wherein the set of computer instruction further comprise instructions executable to:
switch between a first mode of operation for determining the flow rate and a second mode of operation for determining the flow rate;
wherein in the first mode of operation the computer instructions are executable to determine the flow rate as the fluid accumulates in the constant volume chamber and wherein in the second mode of operation the computer instructions are executable to determine the flow rate as the fluid flows through the sonic nozzle.
7. The system of claim 6 , wherein, in the first mode of operation, the flow rate is determined based on the change in pressure over time of the fluid.
8. The system of claim 7 , wherein, in the first mode of operation, the instructions are executable to determine the flow rate based on a change in pressure over time as the fluid accumulates in the constant volume chamber approximately according to
ⅆ
m
ⅆ
t
=
ⅆ
P
ⅆ
t
V
RT
.
9. The system of claim 6 , wherein, in the second mode of operation, the flow rate is determined based on a fluid pressure.
10. The system of claim 6 , wherein, in the second mode of operation, the flow rate is approximately determined according to
massflowrate
=
PA
γ
RT
RT
.
11. The system of claim 6 , wherein, in the second mode of operation, the flow rate is determined based on a fluid density.
12. The system of claim 11 , wherein, in the second mode of operation, the flow rate is approximately determined according to
massflowrate
=
ρ
A
γ
RT
.
13. The system of claim 6 , wherein the computer instructions further comprise instructions to delay determining the flow rate as the fluid flows through the sonic nozzle to allow the pressure in the constant volume chamber to equilibrate.
14. The system of claim 6 , wherein the computer instructions further comprise instructions executable to:
determine 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 determined according to the first mode of operation.
15. The system of claim 14 , wherein the cross sectional area of the sonic nozzle is approximately calculated according to
A
=
massflowrate
*
RT
P
γ
RT
.
16. The system of claim 14 , wherein the cross section area of the sonic nozzle is approximately calculated according to
A
=
massflowrate
ρ
γ
RT
.
17. The system of claim 6 , wherein the computer instructions further comprise instructions executable to:
determine 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 determined according to the first mode of operation.
18. The system of claim 17 , wherein the heat capacity ratio is approximately calculated according to
γ
=
(
RT
*
massflowrate
PA
)
2
RT
.
19. The system of claim 17 , wherein the heat capacity ratio is approximately calculated according to
γ
=
(
massflowrate
ρ
A
)
2
RT
.
20. The system of claim 5 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.
21. A method of determining a flow rate of a fluid comprising:
supplying fluid to a constant volume chamber;
supplying fluid to a sonic nozzle in parallel with the constant volume chamber;
for a first mode of operation, calculating the flow rate as fluid accumulates in the 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 the sonic nozzle for a second range of flow rates; and
switching between the first mode of operation and the second mode of operation.
22. The method of claim 21 , wherein, in the first mode of operation, the flow rate is calculated based on the change in pressure over time of the fluid.
23. The method of claim 22 , further comprising calculating the flow rate based on a change in pressure over time as the fluid accumulates in the constant volume chamber approximately according to
ⅆ
m
ⅆ
t
=
ⅆ
P
ⅆ
t
V
RT
.
24. The method of claim 21 , wherein, in the second mode of operation, the flow rate is calculated based on a fluid pressure.
25. The method of claim 24 , wherein, in the second mode of operation, the flow rate is approximately calculated according to
massflowrate
=
PA
γ
RT
RT
.
26. The method of claim 21 , wherein, in the second mode of operation, the flow rate is calculated based on a fluid density.
27. The method of claim 26 , wherein, in the second mode of operation, the flow rate is approximately calculated according to
massflowrate
=
ρ
A
γ
RT
.
28. The method of claim 21 , further comprising delaying calculating the flow rate as the fluid flows through the sonic nozzle to allow the pressure in the constant volume chamber to equilibrate.
29. The method of claim 21 , further comprising:
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.
30. The method of claim 29 , wherein the cross sectional area of the sonic nozzle is approximately calculated according to
A
=
massflowrate
*
RT
P
γ
RT
.
31. The method of claim 29 , wherein the cross sectional area of the sonic nozzle is approximately calculated according to
A
=
massflowrate
ρ
γ
RT
.
32. The method of claim 21 , further comprising:
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 the flow rate calculated according to the first mode of operation.
33. The method of claim 32 , wherein the heat capacity ratio is approximately calculated according to
γ
=
(
RT
*
massflowrate
P
A
)
2
RT
.
34. The method of claim 32 , wherein the heat capacity ratio is approximately calculated according to
γ
=
(
massflowrate
ρ
A
)
2
RT
.
35. The method of claim 21 , further comprising:
controlling one or more valves to regulate the flow to the constant volume chamber and the sonic nozzle.