Device and method for estimating a flow of gas in an enclosure maintained at reduced pressure in relation to the gas

• US 10,281,304 B2
• Filed: 11/06/2013
• Issued: 05/07/2019
• Est. Priority Date: 11/06/2012
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: Leroy, Arnaud, Cros, Stephane
• Primary Examiner(s): Nguyen, Tan T.
• Application Number:
  US14/440,264
• Publication Number:
  US 20150276443A1
• Time in Patent Office: 2,008 Days
• Field of Search: 702 47, 702138, 702140
• CPC Class Codes: G01F 1/50 Correcting or compensating means
• CPC Class Codes: G01N 15/0826 and measuring fluid flow rate, i.e. permeation rate or pressure change

Abstract

Method for estimating a gas flow in an enclosure maintained in a low pressure regimen relative to the gas, including:

• • measuring, as a function of time, a gas flow J_measurement in the enclosure, and
  • estimating values of the parameters A and B iteratively implemented by decreasing an estimation error based on a difference between J_estim(t) and J_measurement,
  • and wherein, when J_measurement corresponds to a pressure rise of the gas in the enclosure, J_estim(t) is calculated according to the equation:

$J_{\mathrm{estim}}\left(t\right)=2A\sum _{n=1}^{n\mathrm{ma}x}{\left(\frac{B}{\pi \left(t-\mathrm{OffX}\right)}\right)}^{\frac{1}{2}}\exp \left(\frac{-2{\left(n+1\right)}^2}{4B\left(t-\mathrm{OffX}\right)}\right)+\mathrm{OffY}$

• • and when J_measurement corresponds to a pressure decrease of the gas in the enclosure, J_estim(t) is calculated according to the equation:

$J_{\mathrm{estm}}\left(t\right)=P_{\mathrm{init}}-2A\sum _{n=1}^{n\mathrm{ma}x}{\left(\frac{B}{\pi \left(t-\mathrm{OffX}\right)}\right)}^{\frac{1}{2}}\exp \left(\frac{-{\left(2n+1\right)}^2}{4B\left(t-\mathrm{OffX}\right)}\right)+\mathrm{OffY}$

• • FIG. 1.

Claims

1. A method for estimating a permeation of a gas barrier layer, comprising:

providing a permeameter including first and second chambers separated from each other by the gas barrier layer, wherein the first chamber is filled with at least one gas and the second chamber is maintained in a low pressure regimen relative to said at least one gas;

providing a mass spectrometer in the second chamber of the permeameter;

measuring, by the mass spectrometer, an evolution of a partial pressure of the at least one gas in the second chamber as a function of time;

calculating, by processing circuitry, a gas flow J_measurement in the second chamber based on the measured partial pressure of the at least one gas in the second chamber;

estimating, by the processing circuitry, values of parameters A and B iteratively implemented by decreasing an estimation error based on a difference between an estimation of the gas flow J_estim(t) and the measured gas flow J_measurement, wherein

when the measured gas flow J_measurement corresponds to a pressure rise of the at least one gas in the second chamber, the estimation of the gas flow J_estim(t) is calculated according to the equation;

2. The method according to claim 1, wherein the at least one gas is selected from water vapor, oxygen, one of the water or oxygen isotopes, helium, hydrogen, or a mixture of at least two of said gases.

3. The method according to claim 1, wherein estimating the values of the parameters A and B includes at least an implementation of the following steps of:

a₁) choosing initial values of the parameters A and B;

b₁) calculating the estimation of the gas flow J_estim(t);

c₁) calculating the estimation error;

d₁) when the estimation error is positive, decreasing the value of the parameter A and/or the value of the parameter B, and when the estimation error is negative, increasing the value of the parameter A and/or the value of the parameter B,

wherein the implementation of steps b₁) to d₁) is successively repeated several times until a stabilization of the estimated values of the parameters A and B is achieved.

4. The method according to claim 3,

wherein step c₁) includes the implementation of the following steps of:

dividing J_estim(t) and J_measurement into several parts such that each of these parts corresponds to J_estim(t) and J_measurement for a time interval distinct from the time intervals of the other parts;

for each of the parts of J_estim(t) and J_measurement, calculating a parameter

5. The method according to claim 3, wherein the stabilization of the estimated values of the parameters A and B is achieved when the values of the parameters A and B include at least first six digits, in scientific notation, identical to those of the values of the parameters A and B obtained during the previous implementation of steps b₁) to d₁).

6. The method according to claim 1, wherein the values of the parameters A and B are decreased or increased by a variable pitch the value of which depends on previous decreases or increases in the values of the parameters A and B.

7. The method according to claim 1,

wherein the estimation of the values of the parameters A and B is implemented several times by considering, at each of these estimations, different values of the parameter OffX and/or the parameter OffY, and

wherein final values of the parameters A and B are chosen as being those for which a global error between the measured gas flow J_measurement and the estimation of the gas flow J_estim(t) is minimum among all the steps of estimating the values of the parameters A and B implemented.

8. The method according to claim 1, wherein,

when a global error between the measured gas flow J_measurement and the estimation of the gas flow J_estim(t) reaches a minimum value at an instant t_x and is higher than this minimum value after t_x, a new estimation of values of parameters A_x and B_x, corresponding to the parameters A and B for t>

t_x, is implemented,

the values of the parameters A_x and B_x are iteratively estimated by decreasing an estimation error based on a difference, for t>

t_x, between the estimation of the gas flow J_{estim_X}(t) calculated based on the estimated values of the parameters A_x and B_x and the measured gas flow J_measurement from which is subtracted the estimation of the gas flow J_estim(t) for t<

t_x, with X an integer higher than 1, and

the previously calculated parameters A and B are designated A₁ and B₁.

9. The method according to claim 1, wherein the measured gas flow J_measurement is obtained from a measurement of a change over time of the partial pressure of the at least one gas in the second chamber.

10. The method according to claim 9, wherein,

during the implementation of the steps of measuring the gas flow J_measurement and estimating the values of the parameters A and B, the gas barrier layer is saturated with gas, and

the measured gas flow J_measurement corresponds to the pressure decrease of the at least one gas in the second chamber of the permeameter.

11. The method according to claim 10, further including,

after estimating the values of the parameters A and B, calculating a stabilized gas flow J∞

such that J∞

=A·

B, or

when an estimation of the values of the parameters A_x and B_x is implemented, calculating stabilized gas flows J∞

_x such that J∞

_X=A_X·

B_X.

12. The method according to claim 9 further comprising:

depressurizing the first chamber and the second chamber relative to the at least one gas;

firstly implementing the method for estimating the gas flow such that a measured gas flow, designated J_{degas_measurement}, corresponds to the pressure decrease of the at least one gas in the second chamber;

calculating an estimation of a gas flow J_{degas_estim}(t) from the last values of the parameters A and B previously estimated during the first implementation of the method for estimating the gas flow;

introducing the at least one gas into the first chamber such that the partial pressure of the at least one gas in the first chamber is higher than the partial pressure of the at least one gas in the second chamber; and

secondly implementing the method for estimating the gas flow such that the measured gas flow J_measurement, corresponds to the pressure rise of the at least one gas in the second chamber, and during which the estimation of the values of the parameters A and B is performed by decreasing the estimation error based on a difference between an estimation of the gas flow J_{perm_estim}(t) and another gas flow J_{perm_measurement} such that J_{perm _measurement}=J_measurement−

J_{degas_estim}(t).

13. The method according to claim 12, wherein,

when a global error between the measured gas flow J_{degas_measurement} and the estimation of the gas flow J_{degas_estim}(t) is lower than a value of a first threshold Y_{lower_degas}, the estimation of the gas flow J_{degas_estim}(t) is subtracted from the values of the measured gas flow J_measurement during the second implementation of the method for estimating the gas flow, and

when the global error between the measured gas flow J_{degas_measurement} and the estimation J_{degas_estim}(t) is higher than the value of a second threshold Y_{upper_degas}, a last measured value of the gas flow J_{degas_measurement} or an average of several last measured values of the gas flow J_{degas_measurement} is subtracted from the values of the measured gas flow J_measurement during the second implementation of the method for estimating the gas flow.

14. The method according to claim 12, further including,

after estimating the values of the parameters A and B during the second implementation of the method for estimating a gas flow, calculating a stabilized gas flow J∞

such that J∞

=A·

B, or

when an estimation of the values of the parameters A_x and B_x is implemented during the second implementation of a method for estimating a gas flow, calculating a stabilized gas flows J∞

_x such that J∞

_X=A_X·

B_X.

15. A device for estimating a permeation of a gas barrier layer, the device comprising:

a permeameter including first and second chambers separated from each other by the gas barrier layer, wherein the first chamber is filled with at least one gas and the second chamber is maintained in a low pressure regimen relative to said at least one gas;

a mass spectrometer provided in the second chamber of the permeameter; and

processing circuitry configured to

calculate a gas flow J_measurement in the second chamber based on a partial pressure of the at least one gas in the second chamber measured by the mass spectrometer as a function of time,

estimate values of parameters A and B iteratively implemented by decreasing an estimation error based on a difference between an estimation of the gas flow J_estim(t) and the measured gas flow J_measurement, wherein

when the measured gas flow J_measurement corresponds to a pressure rise of the at least one gas in the second chamber, the estimation of the gas flow J_estim(t) is calculated according to the equation;