Method of, and apparatus for, providing a gas mixture

Patent metadata

Field	Value
Publication number	US-9870007-B2
Application number	US-201314402465-A
Country	US
Kind code	B2
Filing date	May 23, 2013
Priority date	May 24, 2012
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

There is provided a gas mixer arrangement comprising a first gas source for supplying a first gas; a second gas source for supplying a second gas different from said first gas; first and second flow regulation devices for regulating the respective flow of the first gas and second gases from the first and second gas sources; a mixer; and an outlet. The mixer is located downstream of the first and second flow regulation devices and arranged, in use, to mix the first and second gases to provide a mixed gas to the outlet. The gas mixer arrangement further comprises a meter comprising a first sensor assembly operable to determine the average molecular weight of the mixed gas and including a high-frequency planar piezoelectric crystal oscillator in contact with the mixed gas, a second sensor assembly operable to determine the pressure of the gas downstream of one of the first or second flow regulation devices, and a controller operable, in response to the average molecular weight of the mixed gas and said gas pressure, to control automatically said first and second flow regulation devices to control the relative proportion of the first and second gases in said mixed gas and the pressure or mass flow rate of the mixed gas from the outlet.

First claim

The invention claimed is:

1. A gas mixer arrangement comprising:
a first gas source for supplying a first gas;
a second gas source for supplying a second gas different from said first gas; first and second flow regulation devices for regulating the respective flow of the first gas and second gas from the first and second gas sources;
a mixer; and
an outlet, the mixer being located downstream of the first and second flow regulation devices and arranged, in use, to mix the first and second gases to provide a mixed gas to the outlet, wherein the gas mixer arrangement further comprises a meter, the meter comprising:
a first sensor assembly positioned inline between the mixer and the outlet, operable to determine the average molecular weight of the mixed gas and including a high-frequency planar piezoelectric crystal oscillator in contact with the mixed gas in flow;
a second sensor assembly operable to determine the pressure of the gas downstream of one of the first or second flow regulation devices; and
a controller operable, in response to the average molecular weight of the mixed gas and said gas pressure, to control automatically said first and second flow regulation devices to control the relative proportion of the first and second gases in said mixed gas and the pressure or mass flow rate of the mixed gas from the outlet.

2. A gas mixer arrangement according to claim 1 , wherein the first and/or second flow regulation device comprises an electronic valve.

3. A gas mixer arrangement according to claim 1 , wherein the second sensor assembly comprises a second high-frequency planar piezoelectric crystal oscillator in contact with the first or second gas upstream of the mixer.

4. A gas mixer arrangement according to claim 1 , further comprising a third sensor assembly operable to determine the pressure of the gas downstream of the other of the first or second flow regulation devices.

5. A gas mixer arrangement according to claim 4 , wherein the third sensor assembly comprises a third high-frequency planar piezoelectric crystal oscillator in contact with the other of the first or second gas upstream of the mixer.

6. A gas mixer arrangement according to claim 1 , wherein the first sensor assembly further comprises a conduit through which the mixed gas flows in use, the conduit having a flow restriction orifice upstream of said outlet through which choked flow occurs in use, the flow restriction orifice dividing the conduit into an upstream portion upstream of said orifice and a downstream portion in communication with the outlet, wherein said piezoelectric crystal oscillator is located in said upstream portion, the first sensor assembly being further operable to measure the mass flow rate of mixed gas through said orifice.

7. A method of providing a mixture of gases in a relative proportion using a gas mixer arrangement, the gas mixture arrangement comprising a first gas source for supplying a first gas, a second gas source for supplying a second gas different from said first gas, first and second flow regulation devices for regulating the respective flow of the first gas and second gases from the first and second gas sources, a mixer located downstream of the first and second flow regulation devices, an outlet and first and second sensor assemblies, the first sensor assembly positioned inline between the mixer and the outlet and comprising a high-frequency planar piezoelectric crystal oscillator in contact with the mixed gas in flow, the method comprising:
a) receiving the first gas from the first gas source;
b) receiving the second gas from the second gas source;
c) mixing the first and second gases to form a mixed gas;
d) measuring a resonant frequency of the high-frequency planar piezoelectric crystal oscillator in contact with the mixed gas in flow;
e) determining, using the second sensor assembly, the pressure of the gas downstream of the first or second flow regulation device;
f) determining the average molecular weight of the mixed gas from said resonant frequency and said pressure measurement; and
g) automatically controlling, in response to said determined average molecular weight and said pressure measurement, said first and second flow regulation devices to control the relative proportion of the first and second gases in said mixed gas and the pressure or mass flow rate of the mixed gas from the outlet.

8. A method according to claim 7 , wherein the first and/or second flow regulation device comprises an electronic valve.

9. A method according to claim 7 , wherein the second sensor assembly comprises a second high-frequency planar piezoelectric oscillator and step e) comprises measuring a resonant frequency of the second high-frequency planar piezoelectric crystal oscillator in contact with the first or second gas upstream of the mixer.

10. A method according to claim 7 , wherein the gas mixer arrangement further comprises a third sensor assembly and the method further comprises, subsequent to step e)
h) determining pressure of the gas downstream of the other of the first or second flow regulation devices.

11. A method according to claim 10 , wherein the third sensor assembly comprises a third high-frequency planar piezoelectric crystal oscillator in contact with the other of the first or second gas upstream of the mixer and step h) comprises measuring a resonant frequency of the third high-frequency planar piezoelectric crystal oscillator in contact with the first or second gas upstream of the mixer.

12. A method according to claim 7 , wherein the first sensor assembly further comprises a conduit through which the mixed gas flows in use, the conduit having a flow restriction orifice upstream of said outlet through which choked flow occurs in use, the flow restriction orifice dividing the conduit into an upstream portion upstream of said orifice and a downstream portion in communication with the outlet, the method further comprising:
i) determining, from the resonant frequency, the mass flow rate of gas through said orifice.

Assignees

• Downie Neil Alexander
• Lee Thomas David Matthew
• Air Prod & Chem

Inventors

• Downie Neil Alexander
• Lee Thomas David Matthew

Classifications

• G05D11/139

  by measuring a value related to the quantity of the individual components and sensing at least one property of the mixture · CPC title

• G05D11/137

  by sensing the density of the mixture · CPC title

• G05D11/02 Primary

  Controlling ratio of two or more flows of fluid or fluent material · CPC title

• G05B15/00

  Systems controlled by a computer (G05B13/00, G05B19/00 take precedence; automatic controllers with particular characteristics G05B11/00) · CPC title

• B01F3/028

  Operations & Transport · mapped topic