Apparatus and method for volume and mass estimation of a multiphase fluid stored at cryogenic temperatures

Patent metadata

Field	Value
Publication number	US-9513155-B2
Application number	US-201414226650-A
Country	US
Kind code	B2
Filing date	Mar 26, 2014
Priority date	Sep 27, 2011
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

An apparatus and method estimate fluid mass in a cryogenic tank that holds a multiphase fluid comprising a liquid and a vapor. The apparatus comprises a level sensor, a pressure sensor and a computer. The level sensor provides a parameter representative of a level of the liquid. The pressure sensor provides a pressure signal representative of vapor pressure inside the cryogenic tank. The computer is operatively connected with the level sensor and the pressure sensor to receive the parameter and the pressure signal, and is programmed to determine the level from inputs comprising the parameter, to calculate a first volume of the liquid from inputs comprising the level, and to calculate a first mass of the liquid from inputs comprising the first volume and the pressure signal.

First claim

What is claimed is:

1. A method of estimating fluid mass in a cryogenic tank that holds a multiphase fluid comprising a liquid and a vapour, wherein the liquid has a density and the vapour has a pressure, the method comprising steps of:
employing a capacitance-type level sensor to provide a parameter representative of a level of the liquid in the cryogenic tank;
measuring the vapour pressure inside the cryogenic tank;
adjusting respective parameters representative of a capacitance of an empty level and a capacitance of a full level of the capacitance-type level sensor as a function of the vapour pressure;
measuring a parameter representative of the actual capacitance of the capacitance-type level sensor;
calculating the level of the liquid in the cryogenic tank as a function of the parameters representative of the capacitance of the empty level, the capacitance of the full level, and the actual capacitance of the capacitance-type level sensor;
calculating a first volume of the liquid as a function of the level of the liquid in the cryogenic tank; and
calculating a first mass of the liquid from inputs comprising the first volume and the density of the liquid.

2. The method of claim 1 , wherein the fluid is a fuel for combustion in an internal combustion engine in a vehicle, the method further comprising a step of estimating a fuelling range for the vehicle from the first mass.

3. The method of claim 1 , wherein the step of employing the capacitance-type level sensor comprises sub-steps of:
providing a pair of spaced apart conductors, the spaced apart conductors being disposed within the cryogenic tank and forming in part a capacitor; and
calibrating the capacitance-type level sensor at least once prior to first introduction of the cryogenic liquid in the cryogenic tank, wherein calibrating the capacitance-type level sensor comprises steps of:
applying a measuring signal to the capacitor;
measuring a parameter representative of a dry capacitance of the capacitor in a dry state, a first dielectric having a first dielectric constant being disposed between the spaced apart conductors in the dry state;
estimating the parameter representative of the capacitance of the empty level in the cryogenic tank, a second dielectric having a second dielectric constant being disposed between the spaced apart conductors at the empty level, the parameter representative of the capacitance of the empty level being estimated based on the parameter representative of the dry capacitance and a first ratio of dielectric constants comprising the first dielectric constant and the second dielectric constant; and
estimating the parameter representative of the capacitance of the full level in the cryogenic tank, a third dielectric having a third dielectric constant being disposed between the spaced apart conductors at the full level, the parameter representative of the capacitance of the full level being estimated based on the parameter representative of the dry capacitance and a second ratio of dielectric constants comprising the first dielectric constant and the third dielectric constant.

4. The method of claim 3 , wherein the second dielectric is the vapour and the third dielectric is the liquid.

5. The method of claim 3 , wherein the step of calibrating further comprises a sub-step of calculating the second dielectric constant and the third dielectric constant as a function of the vapour pressure.

6. The method of claim 1 , wherein the step of calculating the level of the liquid in the cryogenic tank comprises a sub-step of interpolating the level of the liquid in the cryogenic tank between the empty level and the full level based on the actual capacitance of the capacitance-type level sensor.

7. The method of claim 1 , wherein the step of calculating the first volume comprises a sub-step of employing a mathematical relationship between the level of the liquid in the cryogenic tank and the first volume.

8. The method of claim 1 , wherein the step of calculating the first volume comprises a sub-step of employing an empirical relationship between the level of the liquid in the cryogenic tank and the first volume.

9. The method of claim 1 , wherein the step of calculating the first mass comprises
estimating the density of the liquid from inputs comprising the vapour pressure.

10. The method of claim 9 , wherein the step of estimating the density comprises a sub-step of employing a mathematical relationship between the vapour pressure and the density.

11. The method of claim 9 , wherein the step of estimating the density comprises a sub-step of employing an empirical relationship between the vapour pressure and the density.

12. The method of claim 9 , wherein the density is estimated from inputs comprising a speed of propagation of acoustic waves through the liquid.

13. The method of claim 9 , wherein the step of estimating the density comprises sub-steps of:
(i) estimating a composition of the liquid; and
(ii) estimating the density based on the composition of the liquid.

14. The method of claim 1 , wherein the step of calculating the first mass comprises a sub-step of estimating a composition of the liquid.

15. The method of claim 14 , wherein the step of estimating the composition comprises a sub-step of employing a fluid composition sensor.

16. The method of claim 14 , wherein the step of estimating the composition comprises a sub-step of estimating a methane composition.

17. The method of claim 1 , further comprising a step of calculating a second mass of the vapour, a total fluid mass being the sum of the first mass and the second mass.

18. The method of claim 17 , wherein the fluid is a fuel for combustion in an internal combustion engine of a vehicle, the method further comprising a step of estimating fuelling range for the vehicle from the total fluid mass.

19. The method of claim 17 , wherein the step of calculating the second mass comprises sub-steps of:
(i) calculating a second volume occupied by the vapour;
(ii) estimating a density of the vapour; and
(iii) estimating the second mass based on the second volume and the density.

20. The method of claim 19 , wherein the step of estimating the density comprises a sub-step of calculating the density as a function of the vapour pressure.

21. The method of claim 19 , wherein the step of estimating the density comprises sub-steps of:
(i) estimating a composition of the vapour; and
(ii) estimating the density based on the composition of the vapour.

22. The method of claim 1 , wherein the fluid is natural gas.

23. An apparatus for estimating fluid mass in a cryogenic tank that holds a multiphase fluid comprising a liquid and a vapour, the apparatus comprising:
a capacitance-type level sensor capable of providing a parameter representative of a capacitance of the capacitance-type level sensor;
a pressure sensor capable of providing a pressure signal representative of vapour pressure inside the cryogenic tank; and
a computer operatively connected with the capacitance-type level sensor and the pressure sensor to receive the parameter and the pressure signal, and being programmed to:
determine vapour pressure inside the tank as a function of the pressure signal;
adjust respective parameters representative of a capacitance of an empty level and a capacitance of a full level of the capacitance-type level sensor as a function of the vapour pressure;
calculate a level of the liquid in the cryogenic tank as a fun

Assignees

• Westport Power Inc

Inventors

• Harper Gregory C
• Batenburg Gregory A
• Schranz Paul S

Classifications

• G01F23/30 Primary

  by floats · CPC title

• F17C2221/033

  Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG · CPC title

• F17C2250/0417

  with electrical means · CPC title

• G01F23/14

  by measurement of pressure · CPC title

• G01F25/00

  Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume · CPC title