Method and apparatus for multiple-channel dispensing of natural gas

• US 5,653,269 A
• Filed: 06/07/1995
• Issued: 08/05/1997
• Est. Priority Date: 06/27/1991
• Status: Expired due to Fees

• Current Assignee: Natural Fuels Corp.
• Original Assignee: Natural Fuels Corp.
• Inventors: Miller, Charles E., Lopez, John T., Waers, John F., Magin, James A., Custer, Randal L.
• Primary Examiner(s): JACYNA, J CASIMER
• Application Number:
  US08/472,991
• Time in Patent Office: 790 Days
• Field of Search: 141/2-4, 141/18, 141/21, 141/83, 141/94, 141/95, 141/98
• US Class Current: 141/4
• CPC Class Codes: F17C 13/02 Special adaptations of indicating, measuring, or monitoring equipment measuring in general G01
• CPC Class Codes: F17C 2205/0332 Safety valves or pressure relief valves
• CPC Class Codes: F17C 2205/0335 Check-valves or non-return valves
• CPC Class Codes: F17C 2205/035 Flow reducers
• 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 2223/013 liquid
• CPC Class Codes: F17C 2223/033 Small pressure, e.g. for liquefied gas
• CPC Class Codes: F17C 2223/036 Very high pressure (>80 bar)
• CPC Class Codes: F17C 2227/044 by purging
• CPC Class Codes: F17C 2250/043 Pressure
• CPC Class Codes: F17C 2250/0439 Temperature
• CPC Class Codes: F17C 2250/0636 Flow or movement of content
• CPC Class Codes: F17C 2260/022 Avoiding overfilling
• CPC Class Codes: F17C 2260/042 Reducing risk of explosion
• CPC Class Codes: F17C 2265/065 for refueling vehicle fuel tanks
• CPC Class Codes: F17C 2270/0139 Fuel stations
• CPC Class Codes: F17C 5/007 for individual gas tanks or containers, e.g. in vehicles filling with liquid fuel not under pressure, B60S5/02, B67D7/00
• CPC Class Codes: Y10T 137/1987 With additional diverse control

Abstract

A supply plenum connected to a source of compressed natural gas (CNG) and a control valve assembly for selectively turning on the flow of CNG through a sonic nozzle and out through a dispensing hose assembly. Pressure and temperature transducers connected to the supply plenum measure the stagnation pressure and temperature of the CNG and the ambient temperature, and a pressure transducer fluidically connected to the vehicle tank via the dispensing hose assembly monitors the pressure of the CNG in the vehicle tank. An electronic control system connected to the pressure and temperature transducers and to the control valve assembly calculates a vehicle tank cut-off pressure based on the ambient temperature and on the pressure rating of the vehicle tank that has been pre-programmed into the electronic control system, calculates the volume of the vehicle tank and the additional mass of CNG required to increase the tank pressure to the cut-off pressure, and automatically turns off the CNG flow when the additional mass has been dispensed into the vehicle tank. The electronic control system also determines the amount of CNG dispensed through the sonic nozzle based on the upstream stagnation temperature and pressure of the CNG and the length of time the CNG was flowing through the sonic nozzle.

Claims

1. Apparatus capable of dispensing and measuring quantities of natural gas into a plurality of separate tanks, comprising:

a plenum that is of sufficient size to contain a volume of the natural gas being dispensed in substantially stagnant pressure condition;

a first conduit connecting said plenum in fluid flow relationship to a first tank;

a second conduit connecting said plenum in fluid flow relationship to a second tank;

a first valve positioned in said first conduit, said first valve being selectively openable and closeable to selectively allow or prevent flow of natural gas from said plenum to said first tank;

a second valve positioned in said second conduit, said second valve being selectively openable and closeable to selectively allow or prevent flow of natural gas from said plenum to said second tank;

a first sonic nozzle positioned in said first conduit, said first sonic nozzle having a first converting section that starts in said plenum and converges to a first throat that has a cross-sectional area for choking flow of natural gas from said plenum at sonic velocity, and a first diverging section that diverges from said first throat;

a second sonic nozzle positioned in said second conduit, said second sonic nozzle having a second converging section that starts in said plenum and converges to a second throat that has a cross-sectional area for choking flow of natural gas from said plenum at sonic velocity, and a second diverging section that diverges from said second throat;

natural gas pressure supply means connected in fluid flow relationship to said plenum for supplying natural gas to said plenum under sufficient pressure to cause the natural gas to flow at sonic choked velocity in said first sonic nozzle when said first valve is open and to cause the natural gas to flow at sonic choke velocity in said second sonic nozzle when said second valve is open;

a timer that is capable of measuring time that said first valve is open and that is capable of measuring time that said second valve is open;

pressure measuring means in the plenum for measuring stagnant pressure of the natural gas in said plenum when the first valve is open and when the second valve is open;

temperature measuring means in the plenum for measuring temperature of the natural gas in said plenum when the first valve is open and when the second valve is open; and

microprocessor means connected to said timer means, to said pressure measuring means, and to said temperature measuring means for;

(i) calculating quantity or natural gas dispensed through said first conduit by multiplying the time that the first valve is actuated to open times mass flow rate m of natural gas flowing through said first throat, when this m is determined according to the formula;

##EQU5## where C_d is the nozzle discharge coefficient for said first sonic nozzle, k is a constant depending on ratio of specific heat and gas constant of the natural gas, A is the cross-sectional area of the first throat, p₁ is the stagnation pressure of the natural gas in the plenum measured by said pressure measuring means, and T₁ is the temperature of the natural gas in the plenum measured by said temperature measuring means; and

(ii) calculating quantity of natural gas dispensed through said second conduit by multiplying the time that the second valve is open times mass flow rate m'"'"' of natural gas flowing through said second throat, where m'"'"' is determined according to the formula;

##EQU6## where C_d '"'"' is the nozzle discharge coefficient for said second nozzle, k is a constant depending on ratio of specific heat and gas constant of the natural gas, a'"'"' is the cross-sectional area of the second throat, p₁ is the stagnation pressure of the natural gas in the plenum measured by said pressure measuring means, and t₁ is the temperature of the natural gas in the plenum measured by said temperature measuring means.

2. The apparatus of claim 1, including a first valve controller that actuates said first valve to open and close and a second valve controller that actuates said second valve to open and close, said timer being connected to said first valve controller to measure the time that the first valve is open, and said timer being connected to said second valve controller to measure the time that the second valve is open.

3. A method of dispensing and measuring a first quantity of natural gas into a first tank and also dispensing and measuring a second quantity of natural gas into a second tank, comprising the steps of:

connecting a supply of natural gas to a plenum that is of sufficient size to maintain substantially stagnant pressure while the natural gas flows through the plenum to the first tank and to the second tank;

connecting a first conduit between said plenum and said first tank, with said first conduit containing a first sonic nozzle with a first converging section that starts at a first mouth in said plenum and converges to a first throat that has a cross-sectional area a and then diverges, such that natural gas can flow from said plenum, through said first conduit, including through said first sonic nozzle, to the first tank;

connecting a second conduit between said plenum and said second tank, with said second conduit containing a second sonic nozzle with a second converging section that starts at a second mouth in the said plenum and converges to a second throat that has a cross-sectional area A'"'"' and then diverges, such that natural gas can flow from said plenum, through said second conduit, including through said second sonic nozzle, to the second tank;

flowing natural gas from the natural gas supply source, through the plenum, and into said first mouth of said first sonic nozzle for a time t and under sufficient pressure to produce sonic velocity choked flow of natural gas in said first throat, and flowing natural gas from the natural gas supply source, through the plenum, and into said second mouth of said second sonic nozzle for a time t'"'"', at lease part of which time t'"'"' is concurrent with the time t and under sufficient pressure to produce sonic velocity choked flow of natural gas in said second throat;

measuring the respective times t and t'"'"', measuring stagnation pressure p₁ in the plenum as the natural gas flows through the plenum, and measuring temperature T₁ of the natural gas as the natural gas flows through the plenum;

determining the quantity of natural gas dispensed into the first tank by multiplying the time t times mass flow rate m of the natural gas flowing in the first throat, which m is determined by the formula;

##EQU7## where C_d is a discharge coefficient for the first sonic nozzle and k is a constant depending on ratio of specific heat and gas constant of the natural gas; and

determining the quantity of natural gas dispensed into the second tank by multiplying the time t'"'"' times mass flow rate m'"'"' of the natural gas flowing in the second throat, which m'"'"' is determined by the formula;

##EQU8## where C_d '"'"' is a discharge coefficient for the second nozzle and k is a constant depending on the ratio of specific heat and gas constant of the natural gas.

4. Apparatus capable of dispensing and measuring quantities of natural gas into a tank, comprising:

a plenum that is of sufficient size to contain a volume of the natural gas being dispensed in substantially stagnant pressure condition;

a first conduit connecting said plenum in fluid flow relationship to a tank;

a valve positioned in said conduit, said valve being selectively openable and closeable to selectively allow or prevent flow of natural gas from said plenum to said tank;

a sonic nozzle positioned in said conduit, said sonic nozzle having a converging section that starts in said plenum and converges to a throat that has a cross-sectional are for choking flow of natural gas from said plenum at sonic velocity, and a diverging section that diverges from said throat;

natural gas pressure supply means connected in fluid flow relationship to said plenum for supplying natural gas to said plenum under sufficient pressure to cause the natural gas to flow at sonic choked velocity in said sonic nozzle when said valve is open;

a timer that is capable of measuring time that said valve is open;

pressure measuring means in the plenum for measuring stagnant pressure of the natural gas in said plenum when the valve is open;

temperature measuring means in the plenum for measuring temperature of the natural gas in said plenum when the valve is open; and

microprocessor means connected to said timer means, to said pressure measuring means, and to said temperature measuring means for calculating quantity of natural gas dispensed through said conduit by multiplying the time that the valve is actuated to open times mass flow rate m of natural gas flowing through said throat, where this m is determined according to the formula;

##EQU9## where C_d is the nozzle discharge coefficient for said sonic nozzle, k is a constant depending on ratio of specific heat and gas constant of the natural gas, a is the cross-sectional area of the throat, p₁ is the stagnation pressure of the natural gas in the plenum measured by said pressure measuring means, and T₁ is the temperature of the natural gas in the plenum measured by said temperature measuring means.

5. The apparatus of claim 4, including a valve controller that actuates said valve to open and close, said timer being connected to said valve controller to measure the time that the valve is open.

6. A method of dispensing and measuring a quantity of natural gas into a tank, comprising the steps of:

connecting a supply of natural gas to a plenum that is of sufficient size to maintain substantially stagnant pressure while the natural gas flows through the plenum to the tank;

connecting a conduit between said plenum and said tank, with said conduit containing a sonic nozzle with a converging section that starts at a mouth in said plenum and converges to a throat that has a cross-sectional area A and then diverges, such that natural gas can flow from said plenum, through said conduit, including through said sonic nozzle, to the tank;

flowing natural gas from the natural gas supply source, through the plenum, and into said mouth of said sonic nozzle for a time t and under sufficient pressure to produce sonic velocity choked flow of natural gas in said throat;

measuring the time t, measuring stagnation pressure p₁ in the plenum as the natural gas flows through the plenum, and measuring temperature T₁ of the natural gas as the natural gas flows through the plenum; and

determining the quantity of natural gas dispensed into the tank by multiplying the time t times mass flow rate m of the natural gas flowing in the throat, which m is determined by the formula;

##EQU10## where C_d is a discharge coefficient for the first sonic nozzle and k is a constant depending on ratio of specific heat and gas constant of the natural gas.