Method and apparatus for accurately measuring volume of gas flowing as a result of differential pressure

• US 4,646,940 A
• Filed: 05/16/1984
• Issued: 03/03/1987
• Est. Priority Date: 05/16/1984
• Status: Expired due to Term

• Current Assignee: Northern Indiana Public Service Company (NiSource Incorporated)
• Original Assignee: Northern Indiana Public Service Company (NiSource Incorporated)
• Inventors: Rusk, Terrance P., Salmons, David W., Kramer, Robert A.
• Primary Examiner(s): Rolla, Joseph J.
• Assistant Examiner(s): HUPPERT, MICHEAL
• Application Number:
  US06/610,742
• Time in Patent Office: 1,021 Days
• Field of Search: 222/1, 222/3, 222/14, 222/52, 222/54, 222/59, 73/861.01, 73/861.02, 137/486, 137/487.5, 141/192, 141/197, 141/39, 141/5
• US Class Current: 222/1
• CPC Class Codes: F17C 13/025 having the pressure as the parameter
• CPC Class Codes: F17C 2205/0326 electrically actuated
• CPC Class Codes: F17C 2221/033 Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
• CPC Class Codes: F17C 2223/0123 gaseous, e.g. CNG, GNC
• CPC Class Codes: F17C 2223/036 Very high pressure (>80 bar)
• CPC Class Codes: F17C 2250/0426 Volume
• CPC Class Codes: F17C 2250/0434 Pressure difference
• CPC Class Codes: F17C 2250/0443 Flow or movement of content
• CPC Class Codes: F17C 2250/0636 Flow or movement of content
• CPC Class Codes: F17C 2260/024 Improving metering
• CPC Class Codes: F17C 2260/025 Reducing transfer time
• CPC Class Codes: F17C 2265/065 for refuelling vehicle fuel tanks
• CPC Class Codes: F17C 2270/0178 Cars
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/50 Correcting or compensating means
• CPC Class Codes: G01F 15/04 of gases to be measured
• CPC Class Codes: G01F 7/005 by measuring pressure or differential pressure, created by the use of flow constriction

Abstract

A method of accurately measuring volume of gas flowing through a conduit as a result of differential pressure of the gas within the conduit is disclosed. The method comprises determining flow of the gas through the conduit, and terminating flow of the gas through the conduit when the differential pressure is a preselected value. The gas flow and the resulting determination of gas volume are preferably referenced to standard temperature and pressure. Also disclosed is an apparatus for effecting the method.

Claims

1. A method of accurately measuring volume and terminating transient flow of compressed natural gas flowing turbulently as a gas through a conduit including an orifice plate to fill a vehicle fuel tank as a result of differential pressure of said gas within said conduit across said orifice plate, said compressed natural gas transiently flowing very rapidly at the start of a filling operation and slowing as said fuel tank approaches full, comprising:

determining flow of said gas through said conduit at repeating short time intervals from the start of flow through measurement of differential pressure across said orifice plate; and

terminating flow of said gas through said conduit when said differential pressure is a preselected value equal to substantially 1-2 inches of water pressure, said gas volume being referenced to a predetermined temperature and pressure.

2. The method as set forth in claim 1 wherein each short time interval is on the order of two seconds.

3. An apparatus for accurately measuring volume and terminating transient flow of compressed natural gas flowing turbulently as a gas through a conduit to fill a vehicle fuel tank as a result of differential pressure of said gas within said conduit comprising means including at least one storage tank providing a supply of compressed natural gas, a conduit connected to said supply means, means for connecting said conduit to a vehicle fuel tank for filling said tank with compressed natural gas, said compressed natural gas transiently flowing very rapidly at the start of a filling operation and slowing as said fuel tank approaches full, means for determining flow of said gas through said conduit including means providing an orifice in said conduit, differential pressure transducer means connected to said conduit across and relatively close to said orifice;

flow computer means connected to said differential pressure transducer means and repetitively measuring the differential pressure across said orifice at short time intervals, and valve means in said conduit downstream of said orifice providing means connected to said flow computer means for terminating flow of said gas through said conduit when said differential pressure is a preselected value, said gas volume being referenced to a predetermined temperature and pressure.

4. Apparatus as set forth in claim 3 wherein the pressure differential is recomputed on the order of substantially every two seconds.

5. Apparatus as set forth in claim 4 wherein said flow computer means closes said valve when the differential pressure is equal to substantially 1-2 inches of water.

6. Apparatus as set forth in claim 3 wherein said flow computer means closes said valve when the differential pressure is equal to substantially 1-2 inches of water.

7. Apparatus as set forth in claim 3 wherein the differential pressure transducer means comprises a high pressure differential transducer means and a low pressure differential transducer means connected in parallel with one another to said conduit across said orifice.