Total gas meter using speed of sound and velocity measurements
View Patent ↗An apparatus is provided for measuring total gas content of a fluid flowing through a process line. The apparatus comprises a bleed line in fluid communication with the process line for bleeding a portion of the fluid from the process line at a bleed line pressure that is lower than the process line pressure. A speed of sound propagating through the fluid in the bleed line is determined and is, in turn, used to determine a gas volume fraction of the fluid in the bleed line. In one aspect, the total gas content of the fluid flowing through the process line is calculated as a function of the gas volume fraction of the fluid in the bleed line and a velocity of the fluid in the bleed line. In another aspect, the velocity of the fluid in the bleed line is adjusted to be approximately equal to a predetermined velocity. In yet another aspect, dissolved gas in the process fluid 13 is released before the gas content measurement point by applying a high intensity ultrasonic field to the fluid 13.
1. An apparatus for measuring total gas content of a fluid flowing through a process line at a process line pressure, the apparatus comprising:
a bleed line in fluid communication with the process line for bleeding a portion of the fluid from the process line at a bleed line pressure that is lower than the process line pressure;
a device for determining a speed of sound propagating through the fluid flowing through the bleed line; and
at least one signal processor configured to:
determine a gas volume fraction of the fluid in the bleed line using the speed of sound,
determine the total gas content of the fluid flowing through the process line using the gas volume fraction of the fluid in the bleed line and a velocity of the fluid in the bleed line, and
provide an output signal indicative of the total gas content of the fluid flowing through the process line.
2. The apparatus of claim 1 , wherein the total gas content of the fluid flowing through the process line is determined using the equation:
GVF
input
=
1
1
+
1
-
GVF
insitu
(
α
v
liq
+
v
bubble
v
liq
)
GVF
insitu
.
3. The apparatus of claim 1 , wherein the at least one signal processor determines the velocity of the fluid in the bleed line using the output signals from an array of sensors.
4. The apparatus of claim 1 , wherein the velocity of the fluid in the bleed line is adjusted to be approximately equal to a predetermined velocity.
5. The apparatus of claim 4 , wherein the velocity of the fluid in the bleed line is adjusted by at least one of: a size of the bleed line and a flow control device in fluid communication with the bleed line.
6. The apparatus of claim 1 , wherein the at least one signal processor determines an amount of dissolved gas in the fluid flowing through the process line as a difference between a gas volume fraction of the fluid flowing through the process line and the total gas content of the fluid flowing through the process line.
7. The apparatus of claim 1 , wherein the device for determining the speed of sound includes:
an array of sensors disposed at different axial locations along a length of the bleed line, the array of sensors being configured to provide an output signal indicative of acoustic pressure disturbances in the fluid flowing through the bleed line at the different axial locations.
8. An apparatus for measuring total gas content of a fluid flowing through a process line at a process line pressure, the apparatus comprising:
a bleed line in fluid communication with the process line for bleeding a portion of the fluid from the process line at a bleed line pressure that is lower than the process line pressure and at a bleed line velocity that is approximately equal to a predetermined velocity;
a device for determining a speed of sound propagating through the fluid flowing through the bleed line; and
at least one signal processor configured to:
determine the total gas content of the fluid flowing through the process line as a gas volume fraction of the fluid in the bleed line using the speed of sound, and
provide an output signal indicative of the total gas content of the fluid flowing through the process line.
9. The apparatus of claim 8 , wherein the velocity of the fluid in the bleed line is adjusted by at least one of: a size of the bleed line and a flow control device in fluid communication with the bleed line.
10. The apparatus of claim 8 , wherein the velocity of the fluid in the bleed line is adjusted in response to a sensed velocity in the bleed line.
11. The apparatus of claim 8 , wherein the at least one signal processor determines an amount of dissolved gas in the fluid flowing through the process line as a difference between a gas volume fraction of the fluid flowing through the process line and the total gas content of the fluid flowing through the process line.
12. The apparatus of claim 8 , wherein the device for determining the speed of sound includes:
an array of sensors disposed at different axial locations along a length of the bleed line, the array of sensors being configured to provide an output signal indicative of acoustic pressure disturbances in the fluid flowing through the bleed line at the different axial locations.
13. The apparatus of claim 8 , wherein the predetermined velocity is at least five times greater than an estimated bubble velocity.
14. A method for measuring total gas content of a fluid flowing through a process line at a process line pressure, the method comprising:
bleeding a portion of the fluid from the process line at a bleed line pressure that is lower than the process line pressure;
determining a speed of sound propagating through the fluid flowing through the bleed line;
determining a gas volume fraction of the fluid in the bleed line using the speed of sound; and
determining the total gas content of the fluid flowing through the process line using the gas volume fraction of the fluid in the bleed line and a velocity of the fluid in the bleed line.
15. The method of claim 14 , wherein the total gas content of the fluid flowing through the process line is determined using the equation:
GVF
input
=
1
1
+
1
-
GVF
insitu
(
α
v
liq
+
v
bubble
v
liq
)
GVF
insitu
.
16. The method of claim 14 , further comprising:
sensing acoustic pressure disturbances in the fluid flowing through the bleed line at different axial locations along the bleed line to provide signals indicative of the sensed acoustic pressure disturbances; and
using the signals indicative of the sensed acoustic pressure disturbances to determine the speed of sound propagating through the fluid flowing through the bleed line.
17. The method of claim 16 , further comprising:
determining the velocity of the fluid in the bleed line using the signals indicative of the sensed acoustic pressure disturbances.
18. The method of claim 14 , further comprising:
adjusting the velocity of the fluid in the bleed line to be approximately equal to a predetermined velocity.
19. The method of claim 14 , further comprising:
determining an amount of dissolved gas in the fluid flowing through the process line as a difference between a gas volume fraction of the fluid flowing through the process line and the total gas content of the fluid flowing through the process line.
20. A method for measuring total gas content of a fluid flowing through a process line at a process line pressure, the method comprising:
bleeding a portion of the fluid from the process line at a bleed line pressure that is lower than the process line pressure and at a bleed line velocity that is approximately equal to a predetermined velocity;
determining a speed of sound propagating through the fluid flowing through the bleed line; and
determining the total gas content of the fluid flowing through the process line as a gas volume fraction of the fluid in the bleed line.
21. The method of claim 20 , wherein the velocity of the fluid in the bleed line is adjusted by at least one of: a size of the bleed line and a flow control device in fluid communication with the bleed line.
22. The method of claim 20 , wherein the velocity of the fluid in the bleed line is adjusted in response to a sensed velocity in the bleed line.
23. The method of claim 20 , further comprising:
determining an amount of dissolved gas in the fluid flowing through the process line as a difference between a gas volume fraction of the fluid flowing through the process line and the total gas content of the fluid flowing through the process line.
24. The method of claim 20 , further comprising:
sensing acoustic pressure disturbances in the fluid flowing through the bleed line at different axial locations along the bleed line to provide signals indicative of the sensed acoustic pressure disturbances; and
using the signals indicative of the sensed acoustic pressure disturbances to determine the speed of sound propagating through the fluid flowing through the bleed line.
25. The method of claim 20 , wherein the predetermined velocity is at least five times greater than an estimated bubble velocity.