Charging Sequence System And Process

Abstract

Each container in a bank of containers is individually charged with a gas in the order of the highest residual pressure remaining in the containers at the time charging is initiated. Gas withdrawal from the containers begins with the container at the lowest beginning pressure.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. Ser. No. 34,966, filed May 6, 1970.

Description

BACKGROUND OF THE INVENTION

The present invention relates in general to the art of charging and withdrawing gas from containers. More specifically, the present invention relates to a charging system and process which effects sequential charging of a group of containers beginning with the container having the highest residual pressure before charging and ending with the container having the lowest residual pressure, and which effects sequential withdrawal beginning with the container having the lowest pressure before withdrawal commences and ending with the container having the highest pressure.

In the fight against air pollution it has become known that natural gas is an ideal fuel for internal combustion engines. This fuel substantially reduces the emission level of the pollutants of carbon monoxide, oxides of nitrogen and hydrocarbons over the emission levels experienced by gasoline.

Natural gas for use as a fuel in internal combustion engines can be stored in vehicles as a gas in suitable containers, often referred to as tanks or bottles. Typically, presently available tanks are rated at 2,265 p.s.i. at standard temperature conditions.

Obviously, the natural gas tanks in a vehicle must be recharged from time to time. The time to recharge tanks when a natural gas compressor is used alone is often too great for orderly refueling. As a consequence, it is necessary to augment compressor charging in some cases by the use of a storage bank of containers maintained, whenever possible, at some limiting high pressure. However, during large refueling demands on a refueling system it is not always possible to maintain the storage bank of containers at their maximum rated pressure.

Obviously, at any time it is highly desirable to charge a vehicle's natural gas tanks to the highest pressure possible within a given period of time.

SUMMARY OF THE INVENTION

The present invention is directed to a charging system which will effect a rapid charging of a vehicle's natural gas tanks to the maximum pressure commensurate with the capacity of the fueling system and the short time requirements required for the efficient fueling of vehicles. In a more specific embodiment, the present invention contemplates the withdrawal of gas from the system for the maximum charging of the tanks.

More specifically, the present invention provides a process and system which employs at least two storage containers or vessels which are sequentially charged in the order of the highest residual pressure existing in a container before charging commences.

A specific form of the present invention contemplates a source of pressurized gas which may include a compressor, a series of containers to be charged, and sequence fill and transfer valve means for each container. The sequencer valve means each has a fill position and a transfer position. Means is provided for maintaining each sequencer valve means in its fill position and in communication with its container below a predetermined pressure, typically the rated pressure of the containers. Means is also provided for each sequencer valve means to change the valve's position from its fill position to its transfer position in response to the predetermined pressure existing in its associated container and to then establish communication between a downstream valve and the gas source. Means is also provided to prevent gas communication between a container and the source of pressurized gas when another container is being charged.

In a more specific form, the system of the present invention contemplates that each sequencer valve means control of flow of gas from the source of pressurized gas to succeeding containers in a series of containers by preventing gas communication beyond the valve means admitting to gas flow to its container. This may be done by connecting the source of gas to the containers in series through the sequencer valve means and providing each sequencer valve means with means for preventing gas flow downstream from it when it is admitting to gas flow into its container.

It is preferred that the means for maintaining each of the valves in its fill position until a predetermined pressure is reached be temperature compensated in order that utilization of available container volume be maximized. In greater detail, it is preferred that the temperature within a container being charged control the predetermined pressure to compensate for variations in container temperature owing to such factors as ambient temperature. Thus on a warm day where the density of a given amount of gas is low but its pressure relatively high, the predetermined pressure would be higher than the rated pressure of the container. Conversely, on a cold day for a given amount of gas, the predetermined pressure would be lower than the rated pressure of the container. This is detailed in copending application Ser. No. 34,966 of which this application constitutes a continuation-in-part.

The present invention also contemplates the selective charging of other vessels or containers from the storage containers by charging from the storage container having the lowest beginning pressure initially and ending at the storage container having the highest beginning initial pressure.

A preferred form of the sequencer valve means of the present invention contemplates the combining of the sequencer fill and transfer valve and a transfer sequencer valve. A valve spool for the fill and transfer sequencer valve is disposed in a bore of a housing for translation between a fill position and a transfer position. Inlet means to the bore is provided from an outlet means from the bore of the next sequencer valve upstream and from the source of gas for the first valve. The spool in the fill position masks the outlet means but communicates the particular valve's container with the inlet port. In the transfer position, the spool prevents communication from the inlet port to the container but allows communication through the valve to the next subsequent sequencer valve's inlet. The position of the spool is determined by pressure on a reference pressure side thereof and on a side in direct communication with its associated container such that when container pressure reaches the predetermined value it overcomes the effect of the reference pressure and any biasing means to shift the spool to the transfer position.

On the withdrawal side of each valve a draw and bypass spool is provided, the position of which between a draw position and a bypass position is determined by its container pressure and a reference pressure. The reference pressure is the pressure of the tanks receiving gas from the container and, preferably, a biasing spring. In the bypass position of each valve, the valve's container is out of communication with the tanks but the tanks are in communication with the next upstream valve, or the source of gas in the case of the last valve. In the draw position of each valve, upstream valves are out of communication with the tanks but the container for the particular valve is in communication with the tanks. As a consequence, the lowest pressure containers will exhaust first.

These and other features, aspects and advantages of the present invention will become more apparent from the following description, appended claims and drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow sheet illustrating the charging and withdrawal system and process of the present invention; and

FIG. 2 is a view of the preferred sequential fill limiter and discharge valve assembly of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The system of the present invention will be described initially with reference to FIG. 1. In this Figure, a natural gas compressor 10 is illustrated. This compressor may be of any well known forms and obviously compresses gas from a source at relatively low pressure to some predetermined pressure for discharge into a line 12. A bank of containers or bottles consisting of containers 14, 16 and 18 are in communication with line 12 through respective sequential fill and discharge valves 20, 22 and 24. The containers are connected in series through their respective sequential fill and discharge valves both for their charging and discharge. Each container can, of course, be replaced by two or more containers.

In the embodiment illustrated and for reasons to become apparent subsequently, when there is not enough time to bring all the containers up to rated pressure between withdrawals, container 14 will always have a residual pressure before charging in excess of the residual pressure in containers 16 and 18. Similarly, container 16 will have a residual pressure before charging in excess of the pressure existing in container 18. Of course, if there is sufficient charging time between withdrawals, all the containers will be at the same pressure. But for purposes of this discussion it will be assumed that there is insufficient time to bring all the containers up to their rated pressure before withdrawal to a vehicle's gas storage tanks.

Sequential fill and discharge valve 20 for container 14 controls the flow of gas to downstream containers 16 and 18 such that when container 14 is being charged no gas passes past valve 20 to the downstream containers.

Conversely, during withdrawal of gas from the containers, sequential fill and discharge valve 24 prevents discharge of gas from containers 14 and 16 until the gas in container 18 is effectively exhausted. The same is true of sequential fill and discharge valve 22 which prevents the withdrawal of gas from container 14 until container 16 is effectively exhausted.

To accomplish these ends, each of the valves 20, 22 and 24 has a fill side and a withdrawal side indicated in FIG. 1 for the fill side by reference numerals 20a, 22a and 24a, and for the withdrawal side by reference numerals 20b, 22b and 24b.

The fill side of valves 20 and 22 are in series gas communication through a line 26. As will become apparent subsequently, line 12 from the compressor leads directly to the withdrawal side of valve 20 so that when valve 20 is in its draw position gas from the compressor will pass through the valve and through a line 27 to the inlet side of the valve. The fill side of valves 22 and 24 are in series gas communication through a line 28.

The withdrawal sides of valves 20 and 22 are in series gas communication through a line 30, and the withdrawal sides of valves 22 and 24 are in series gas communication through a line 32. The withdrawal side of valve 24 leads to the vehicle tanks to be charged through a line 34.

The system illustrated in FIG. 1 has a transfer valve 36 in line 34 emanating from the withdrawal side of valve 24 for the initiation of gas withdrawal from the containers.

The fill side of each valve has a fill position and a transfer and off position. Each valve has a valving element, such as a spool, which is positionally responsive to a reference pressure and the particular valve's container pressure such that when the reference pressure exceeds the container pressure the valve is in its fill position and gas can enter the container. When the container pressure exceeds the reference pressure, the particular valve will go to its transfer and off position. In the transfer position a valve admits to gas flow downstream from it and stops gas flow to its associated container. When valve 24 is in its transfer position, gas is recycled through a line 37 back to the compressor inlet, or to a pressure switch which stops the compressor, at the option of the user. In FIG. 1, the reference pressure is supplied by reference pressure vessels 38, 40 and 42 through lines 44, 46 and 48 for valves 20, 22 and 24, respectively. Gas communication from and to valves 20, 22 and 24 to and from containers 14, 16 and 18 is through lines 50, 52 and 54, respectively.

The withdrawal side of each valve has a container bypass position and container draw position. In the container draw position for a given valve, gas can be drawn from that valve's container. In the bypass position for a given valve, gas cannot be withdrawn from its container but only from a container upstream from it, or in the case of valve 20, from compressor 10. To effect this type of operation each valve has a second valving element such as a spool, which is positionally responsive from its draw position to its bypass position when container pressure drops below a given value relative to the pressure in the tanks being charged. Conversely, each valve shifts from its bypass position to its draw position when its container pressure exceeds a given value relative to the pressure in the tanks being charged The withdrawal side of each of the valves 20, 22 and 24 is in pressure communication with the tanks being charged through parallel branch lines 56, 58 and 60, respectively, all of which are connected to the tanks being charged downstream of transfer valve 36 through a common line 62.

With reference to FIG. 2, a more detailed depiction of sequential fill and discharge valve 22 is presented. This valve is identical in construction to valves 20 and 24 and is connected into the system illustrated in FIG. 1 identically, save for minor details to be described subsequently.

In general, valve 22 has a housing 64 having aligned bores 66 and 68 which receive fill limiter and transfer spool 70 and a draw and bypass spool 72. Spool 70 is in fill side 22a and spool 72 is in transfer side 22b. The fill side of the valve will be initially described.

Line 26 from valve 20 opens into bore 66 for incoming gas and, as such, constitutes an inlet line for the valve. Line 28 also opens into the bore for outgoing gas to valve 24 and, as such, constitutes an outlet line from the valve. A chamber 74 midway between the fill and transfer side of the valve is in communication with container 16 through line 52. A reference pressure chamber 76 is in pressure communication with reference pressure vessel 40 through line 46.

Spool 70 is generally cylindrical and has an annular, relatively elongated flow channel 78 bounded by lands 80 and 82 for communicating inlet line 26 with outlet line 28 when the pressure in chamber 74 is sufficient to overcome the pressure in reference chamber 76. An axial passage 84 in spool 70 opens into chamber 74 and is in communication with an annular channel 86 through one or more radial passages 88. Channel 86 is in communication with inlet line 26 in the fill position of the valve, which is the position illustrated in FIG. 2.

Means are provided to prevent axial gas flow between the lands of the spool and the wall of the bore such as a pair of O-rings 90 on either axial side of channel 78 and a pair of O-rings 92 on either axial side of channel 86.

The reference pressure chamber, as previously mentioned, is in direct communication with reference pressure vessel 40. The latter vessel is in thermal communication with container 16. As such, the pressure in the reference pressure chamber is determined by the temperature of gas within container 16. Because the gas in the reference pressure chamber line 46 and vessel 40 constitutes a closed system, the reference pressure in the chamber is a direct function of temperature. As a consequence, when the temperature in container 16 is relatively high, so will be the pressure in reference pressure chamber 76. The converse is also true.

The pressure in vessel 40, acting in chamber 76, is such that during charging spool 70 will shift to its transfer position when the pressure exerted on it from container 16, acting in chamber 74, reaches a predetermined value of, say, 2,265 p.s.i. at 70.degree. F.

On the withdrawal side of the valve, spool 72 is capable of translation in bore 68 between a draw position and a bypass position. The position illustrated in FIG. 2 is the draw position. Line 32 opens into a transfer chamber 94 and is in direct communication through this chamber with chamber 74 and container 16 when spool 72 is in its draw position. Line 30 opens into bore 68 and emanates from the transfer chamber of valve 20.

One end of spool 72 sees the pressure in the tanks being charged through line 58 which opens into a reference pressure chamber 96. In addition, a biasing spring 98 is disposed to act between an end of housing 64 and spool 72 and exerts predetermined biasing pressure on the spool of, say, 50 p.s.i., which tends to move the spool to its bypass position.

Spool 72 has an annular bypass channel 100 disposed to bridge the distance between line 30 and a line 101 in the draw position and between lines 30 and 32 to communicate the two in the spool's bypass position. Line 101 is blocked in each valve except in valve 20 where it is shown by reference numeral 27. Line 27 leads to the part of valve 20 corresponding to line 26 in FIG. 2. Again, O-rings are provided to prevent leakage of gas from or to the channel along the interface between the spool and the wall of bore 68. These O-rings are indicated by reference numerals 102, 104 and 106 and are disposed in lands 108, 110 and 112, respectively.

Spool 72 shifts to its bypass position when the pressure in the tanks being charged and biasing spring 98 is sufficient to overcome the pressure within container 16 acting in chamber 74.

The differences in the system connections for valves 20 and 24 over those for valve 22 will now be described.

For valve 24, line 34 leads from the valve at the same location that line 32 leaves valve 22 but goes directly to the tanks being charged. Line 37 leads either to a compressor shutdown device of the compressor inlet to control the compressor when all tanks are filled. In other words, envisioning valve 22 as valve 20 during withdrawal, the compressor will be in direct communication with line 26 through line 30, channel 100 and line 101. With this communication, the compressor directly charges the vehicle's tanks. When the pressure in container 14 approaches vehicle tank pressure, the spool of valve 20 corresponding to spool 72 will move to the bypass position dropping container 14 out of fluid circuit. However, compressor 10 will still be in communication with the vehicle's tanks through channel 100 and line 26 (the latter corresponding to line 32 in FIG. 2).

For valve 20, the compressor is connected through line 12 to the part corresponding to line 30 in FIG. 2 so that when all available gas has been transferred from container 14 to the vehicle being charged, the movement of the spool of valve 20 corresponding to spool 72 will connect the compressor directly to the vehicle. During this final filling mode no gas will be placed in the storage tanks.

The filling sequence of containers 14, 16 and 18 will now be described. Typically, the pressure in the containers will progressively decrease from container 14 to container 18 before the beginning of filling and each container will be below its filled pressure. In this condition, the fill limiter and transfer spool of valve 20 corresponding to spool 70 of valve 22 will be in its fill position. Since no vehicle is connected at the outlet of valve 24, all withdrawal valves will be in the draw position. The compressor is then connected through lines 12 and 27 to container 14. Communication with containers downstream of valve 20 is not possible because the fill limiter and transfer spool of valve 20 prevents communication with downtream valves by blocking line 26. When the pressure in container 14 is sufficient to overcome the pressure in the reference chamber of the valve, the spool will be forced to its transfer position, and lines 12 and 26 will be in communication with one another. At this time, container 16 will begin to be filled and container 14 will be out of communication with the compressor 10. The same sequence of events will progressively occur for containers 16 and 18.

So long as container 18 has more pressure than the vehicle to be charged, withdrawal will begin with container 18. The draw and bypass spool of valve 24 for this container will be in its draw position. In the draw position, container 18 will communicate with the tanks in the vehicle through the transfer chamber of that particular valve and line 34. When the pressure in the tanks of the vehicle and the pressure in container 18 approach one another, the biasing spring of valve 24 and tank pressure will force the draw and bypass spool to its bypass position and gas transfer to the tanks of the vehicle will switch to container 16. The same sequence of events occurs in changing from container 16 to container 14.

In the event that container 18 should have less pressure than the vehicle to be charged at the beginning of withdrawal, container 16 will transfer its gas first, followed by container 14. As previously mentioned, valve 20 admits to direct communication between the tanks of the vehicle being charged and the compressor.

The present invention provides a charging system and process which, by charging storage containers having the highest beginning residual pressure first, maximizes the filling of vehicle tanks because the charging sequence maximizes available container pressure. The system and process of the present invention also maximizes vehicle tank filling by drawing from the container having the lowest beginning pressure, then progressively shifting to containers having gas under higher pressure. This again assures the effective maximum utilization of the filling force afforded by container pressure. Thus, for a given capacity charging system the fill time for vehicles using compressed gas is maximized.

The present invention has been specifically described with reference to its presently preferred embodiment. The spirit and scope of the appended claims should not, however, necessarily be limited to the foregoing description. For example, while the invention has been described with reference to the charging of the fuel tanks of vehicles using natural gas, the invention has utility in other environments.

Claims

What is claimed is:

1. A system for sequentially filling containers with a gas in the order of their highest starting pressure and for sequentially withdrawing gas from the containers in the order of their lowest starting pressure comprising:

a. a source of pressurized gas;

b. a series of containers C.sub.1 through C.sub.N , N being at least two;

c. means for each container for communicating each container successively and individually beginning with container C.sub.1 and ending with container C.sub.N with the source of gas until a predetermined charging pressure for each container is reached; and

d. means for each container for withdrawing gas from the system to a delivery point by communicating each container successively and individually beginning with container C.sub.N and ending with container C.sub.1 with the delivery point, the means being operative to prevent communication with each container beginning with container C.sub.N and ending with container C.sub.1 upon the occurrence of a predetermined withdrawal pressure differential between each container and the delivery point.

2. The system claimed in claim 1 wherein:

a. the means for communicating each container C.sub.1 through C.sub.N.sub.-1 with the source of gas includes a fill and transfer valve for each of such containers, each such valve having a fill and transfer position, each valve in its fill position being in communication with its container, each valve in its transfer position being in series fluid circuit with the other valves and being out of communication with its container; and

b. the means for communicating each container with a delivery point includes a draw and bypass valve for each container, each such valve having a draw position and a bypass position, each valve in its draw position being in communication with its container, each valve in its bypass position being in series fluid circuit with the other valves, each valve being in its draw position until the predetermined withdrawal pressure differential between its container and the delivery point exists and in its bypass position thereafter.

3. The system for filling containers with a gas in sequential order claimed in claim 2 including means for the containers to establish the predetermined charging pressure as a direct function of the temperature of gas in the containers by each of the valving elements being responsive to its container pressure and the pressure in a closed gaseous system in thermal communication with the container such that the valving element is in its fill position until a predetermined differential between the container and the gaseous system exists whereupon the valving element moves to its transfer position.

4. The system claimed in claim 1 wherein:

a. the means for communicating each container C.sub.1 through C.sub.N.sub.-1 with the source of gas includes a fill and transfer valve for each of such containers, each fill and transfer valve having:

i. a valving element positionally responsive between a fill position and a transfer position,

ii. means for maintaining the valving element in its fill position until the predetermined charging pressure for the container is reached,

iii. means responsive to the predetermined charging pressure to maintain the valving element in its transfer position, and

iv. means for serially connecting the valve to the other fill and transfer valves and the source of gas such that in its fill position its container is in communication with the source of gas and out of communication with any downstream valves and in its transfer position its container is out of communication with the source of gas and the valve is in communication with the next succeeding downstream valve; and

b. the means for communicating each container with the delivery point includes a draw and bypass valve for each container, each draw and bypass valve having:

i. a valving element positionally responsive between a draw and a bypass position,

ii. means for maintaining the valving element in its draw position until the predetermined withdrawal pressure differential exists between its associated container and the delivery point,

iii. means responsive to the predetermined withdrawal pressure differential to maintain the valving element in its bypass position, and

iv. means for serially connecting the valve to the other draw and bypass valves and the delivery point such that in its draw position the container for the valve is in communication with the delivery point and out of communication with any upstream valves and in its bypass position its container is out of communication with the delivery point and the valve is in communication with any next proceeding upstream valve.

5. The system claimed in claim 4 wherein the means for maintaining each fill and transfer valve's valving element in its fill position includes

a closed gaseous system in thermal communication with the valve's container and having means responsive to the pressure within it to act on the valving element and bias the valving element towards its fill position.

6. The system claimed in claim 5 wherein the means responsive to the predetermined charging pressure to maintain each fill and transfer valve's valving element in its transfer position includes

means responsive to the valve's container pressure for acting on the valving element and biasing the element towards its transfer position.

7. The system claimed in claim 4 wherein means is included for communicating the source of pressurized gas with the delivery point when the predetermined withdrawal pressure differential between each container and the delivery point occurs.

8. The system for filling containers with a gas in sequential order claimed in claim 7 wherein:

each of the valving element maintaining means for the valves for containers C.sub.1 through C.sub.N includes means responsive to the pressure in a closed gaseous system in thermal communication with the containers, the predetermined pressure being a direct function of the temperature of the gas in the containers.

9. The system claimed in claim 1 wherein means is included for communicating the source of pressurized gas with the delivery point when the predetermined withdrawal pressure differential between each container and the delivery point occurs.

10. The system for filling containers with a gas in sequential order claimed in claim 1 wherein:

means is provided for each of the valves to communicate such valve with its container only until the pressure therein and the pressure of a gas in a closed gaseous system in thermal communication with such container reaches a predetermined differential.

11. The system claimed in claim 10 wherein means is included for communicating the source of pressurized gas with the delivery point when the predetermined withdrawal pressure differential between each container and the delivery point occurs.