HK1064431B - Compressed natural gas dispensing system - Google Patents

Description

Compressed natural gas distribution system

Technical Field

The present invention relates generally to natural gas, and more particularly to natural gas fuel delivery systems.

Background

Compressed Natural Gas (CNG) locomotives require dedicated fueling delivery systems. One such system is disclosed in us patent 5,884,675 and consists of a plurality of cylinders each having an axially movable piston, a pair of inlets and an outlet. The cylinders are filled with CNG at a remote location and then transported to a fueling station. Hydraulic fluid is pumped from a reservoir into one end of each cylinder at the fueling station. The hydraulic fluid displaces a piston in each cylinder, forcing the CNG through an outlet at the other end of the cylinder. CNG flows through hoses into the locomotive to be refueled. Each group of cylinders is provided with an accumulator downstream of the outlet. When the cylinder is completely emptied of CNG, the pressure in the accumulator returns each piston to its original position, forcing the hydraulic fluid out of the cylinder and back into the reservoir.

Although this system is an improvement over other CNG delivery systems, it still has a number of disadvantages. Each cylinder has a movable piston and openings at both ends, which is expensive to manufacture.

Summary of The Invention

A Compressed Natural Gas (CNG) fueling system has a hydraulic fluid reservoir containing a hydraulic fluid, a pump, and a reversible flow valve. Hydraulic fluids are a class of fluids that are difficult to mix with CNG. The fueling system also includes a plurality of cylinders containing CNG. Each cylinder is fitted with a fitting in an opening at one end thereof. The joint contains a hydraulic fluid valve (port) and a gas valve (gas valve). The tube extends from the hydraulic fluid valve inside the cylinder up to a point near the other end of the cylinder. The other end of the steel cylinder is closed.

Hydraulic fluid is pumped from the reservoir at the fueling station through the hydraulic fluid valves in each cylinder, displacing the CNG in each cylinder, and forcing the CNG out through the valves of each cylinder. During fueling, the hydraulic fluid pumped from the reservoir is required to maintain the cylinder pressure at 3600 psi. When the sensor detects that the cylinder is completely emptied of CNG, the reversible flow valve reverses direction, allowing hydraulic fluid to flow back into the reservoir. After the cylinder is emptied of hydraulic fluid, the cylinder is disconnected and then refilled with CNG.

Brief Description of Drawings

FIG. 1 is a schematic flow diagram of a compressed natural gas fueling system constructed in accordance with the present invention.

FIG. 2 is an enlarged side cross-sectional view of one of the cylinders of FIG. 1.

Fig. 3 is an enlarged partial side cross-sectional view of the cylinder of fig. 2, revealing a fitting mounted in one end of the cylinder.

FIG. 4 is an enlarged side cross-sectional view of one of the cylinders of FIG. 1, showing another embodiment of the present invention.

Fig. 5 is an enlarged side sectional view of the tracer disk installed in the cylinder of fig. 4 according to the present invention.

Fig. 6 is an enlarged portion of the cylinder of fig. 4.

Detailed description of the preferred embodiments

Referring to fig. 1, a Compressed Natural Gas (CNG) fueling system 10 is shown. The fueling system 10 is divided into a control section 12, a transfer section 14 and a fueling section 16. The control section 12 includes a control panel (not shown). The control section 12 also includes a hydraulic fluid reservoir 18 containing hydraulic fluid. Hydraulic fluids are liquids that are difficult to mix with CNG, such as synthetic hydrocarbon hydraulic oils. One suitable class of fluids is the synthetic lubricating oils manufactured by O' Rourke Petroleum Products, Houston, Texas under the trade designation "Low Vapor 68".

The reservoir 18 is provided with an outlet pipe 20 leading to a hydraulic fluid pump 22. The pump 22 has an outlet pipe 24 leading to reversible flow valves 26, 28, 30. A pressure gauge 32 monitors the pressure in the pump outlet tube 28. A relief valve 34 is provided in the pump outlet tube 28 to prevent pressures above 3600psi by venting over-compressed fluid back into the reservoir 18. A check valve 36 in the pump outlet line 24 allows hydraulic fluid to flow from the pump 22 to the flow valves 26, 28, 30. A return line 38 extends from the flow valves 26, 28, 30 to the reservoir 18. The return line 38 carries a separator 40 which removes any entrained CNG from the hydraulic fluid. The sensor 42 detects any entrained CNG and then transmits a signal to the control panel in the presence of CNG. The separation device 44 releases any entrained CNG from the reservoir 18. The reservoir 18 also has an indicator 46, preferably a float indicator, which tracks the level of fluid in the reservoir. The indicator 46 is connected to a transmitter 48 which provides a signal to the control panel if the level of fluid in the reservoir 18 reaches a specified lower or upper level.

The transfer section 14 contains 50, 52, 54 sets of high pressure accumulators 56. 50. 52, 54 each contain an equal number of cylinders 56, which are also of the same size. As shown in fig. 2, each cylinder 56 has a housing 58 and an interior cavity 60. The cavity 60 of each cylinder 56 is filled with compressed CNG 62 prior to delivery to the fueling station. Each cylinder 56 also has a first end 64 and a second end 66. The second end 66 is closed. The first end 64 has an opening 68 through which a nipple 70 extends. As shown in fig. 3, the connector 70 contains a hydraulic fluid trap 72 and a valve 74. A hollow tube 76 extends within the interior chamber 60 from the hydraulic fluid valve 72 to a position adjacent the second end 66 and functions to direct hydraulic fluid 78 into the interior chamber 60.

Referring back to fig. 1, the hydraulic fluid valves 72 of each cylinder 56 of the groups 50, 52, 54 are connected together side-by-side by a fluid manifold 80. The reversible flow valves 26, 28, 30 are located between the pump 22 and the fluid manifold 80. Each fluid manifold 80 has a manually-carried shut-off valve 82. 50. The valves 74 of each cylinder 56 of the respective groups 52, 54 are connected together side-by-side by a gas manifold 84. 50. 52, 54 also have a relief valve 86, a flare valve 88 and manually-actuated shut-off valves 90, 92 in parallel downstream of the damper 74. The relief valve 86 prevents pressures above 3600psi by venting excess compressed CNG away from the cylinder 56. The flare valve 88 allows CNG to be bled from any of the 50, 52, 54 groups when the 50, 52, 54 groups require maintenance or repair. Manual loading of the shut-off valves 90, 92 enables isolation of any 50, 52, 54 group under whatever circumstances. Check valve 94 allows CNG to flow downstream from gas manifold 84 to hose 96. Check valve 98 allows CNG to flow upstream from hose 96 back to gas manifold 84. A flow control valve 100 and a manual load shutoff valve 102 are located in hose 96.

The fueling section 16 contains at least one fueling station 104. Each fueling station 104 has a manually-carried shut-off valve 106 and a filter unit 108. The filtration unit 108 removes any entrained hydraulic fluid from the CNG stream prior to dispensing the CNG. The filter unit 108 is provided with a test plug 110 for detecting the presence of hydraulic fluid in the filter unit 108.

In operation, the plurality of banks 50, 52, 54 are discharged one bank at a time. If the stack 50 is discharged first, the manually-carried shut-off valves 82, 90 of the stack 50 are opened and the manually-carried shut-off valve 92 of the stack 50 is closed. The configuration of the reversible flow valve 26 allows downstream flow from the pump 22 to the stack 50. Hydraulic fluid is pumped from the reservoir 18 through the pump 22 into the fluid manifold 80, through the fluid gate 72 and into the cylinder 56, the pressure in the cylinder 56 being maintained at 3600psi as the CNG is dispensed. As shown in fig. 2, hydraulic fluid 78 flows through hollow tube 76 into cylinder 56 at the end opposite connector 70. The hydraulic fluid 78 is in direct contact with the CNG 62 at the interface 112, but is not mixed with the CNG 62. CNG 62 flows out of cylinder 56 through valve 74, gas manifold 84, check valve 94 and hose 96 to fueling station 16. The flow control valve 100 limits the pressure in the hose 96 to 3600 psi.

When the stack 50 is substantially empty of CNG, the level of hydraulic fluid in the reservoir 18 may have reached a prescribed lower limit level, which is sensed by the float indicator 46. The transmitter 48 transmits a signal to the control panel. The manually-carried shut-off valves 82, 90 of the stack 50 are closed and the manually-carried shut-off valve 92 of the stack 50 is opened. The configuration of the reversible flow valve 26 allows upstream flow from the fluid manifold 80. CNG in hose 96 flows back into cylinder 56 through check valve 98. The residual CNG in the cylinder 56 forces the hydraulic fluid out of the cylinder 56. The hydraulic fluid is returned to the reservoir 18 through a return conduit 38. A separator 40 in the return line 38 removes any CNG entrained in the hydraulic fluid.

After substantially all of the hydraulic fluid has been discharged from the cylinder 56, the level of hydraulic fluid in the reservoir 18 may have reached a prescribed upper limit level, which is detected by the float indicator 46. The transmitter 48 transmits a signal to the control panel. The manual load shutoff valves 82, 90 of the group 52 are opened and the manual load shutoff valve 92 of the group 52 is closed. The configuration of the reversible flow valve 28 allows downstream flow to the stack 52. Group 52 begins dispensing CNG in the same manner as group 50.

Referring to fig. 4, 5 and 6, alternative embodiments of the present invention are shown. As shown in fig. 4, a tracer element 114 is mounted in the interior chamber 60 of the cylinder 56. The tracer element 114 is located substantially at the interface 112 of the CNG 62 and the hydraulic fluid 78. The tracer element 114 is a flat plate or disc having an opening 116 in the center that is slightly larger in diameter than the hollow tube 76. The tracer 114 also has an outer edge 118 with a diameter slightly smaller than the diameter of the lumen 60. The tracer element 114 is a soft, thin element of plastic or rubber that is impermeable to both the hydraulic fluid 78 and the CNG 62 and contains ferromagnetic powder. As shown in fig. 6, the probe of the detector 120 extends through the connector 70, which senses the proximity of the tracer element 114 and sends a signal to the control panel.

In operation, the banks 50, 52, 54 are discharged one bank at a time. If the stack 50 is discharged first, the manually-carried shut-off valves 82, 90 of the stack 50 are opened and the manually-carried shut-off valve 92 of the stack 50 is closed. The configuration of the reversible flow valve 26 allows downstream flow from the pump 22 to the stack 50. CNG 62 is forced out of the chamber 60 by the hydraulic fluid 78. As the amount of CNG 62 in the cavity 60 decreases, the interface 112 moves closer to the fitting 70. Because the tracer element 114 is not in contact with the hollow tube 76 or the cavity 60, the tracer element 114 can always be located at the interface 112, moving within the cavity 60 as the level of CNG 62 changes.

When the cylinder 56 is substantially empty of CNG 62, the tracer element 114 is located at a point in the stroke closest to the connector 70. The detector 120 detects the position of the tracer element 114 and transmits a signal to the control panel. The configuration of the reversible flow valve 26 allows upstream flow from the fluid manifold 80. CNG in hose 96 flows back into cylinder 56 through check valve 98. The residual CNG in the cylinder 56 forces the hydraulic fluid out of the cylinder 56. The hydraulic fluid is returned to the reservoir 18 through a return conduit 38. A separator 40 in the return line 38 removes any CNG entrained in the hydraulic fluid.

After substantially all of the hydraulic fluid has been discharged from the cylinder 56, the tracer element 114 will be at a point furthest from the adapter 70. The detector 120 detects the position of the tracer element 114 and transmits a signal to the control panel. The manual load shutoff valves 82, 90 of the group 52 are opened and the manual load shutoff valve 92 of the group 52 is closed. The configuration of the reversible flow valve 28 allows downstream flow to the stack 52. Group 52 begins dispensing CNG in the same manner as group 50.

It should be noted that in this alternative embodiment of the invention, the tracer element 114 and detector 120 function substantially the same as the float indicator 46 and transmitter 48. Thus, the float indicator 46 and transmitter 48 are not required in this alternative embodiment, but may be included if desired.

The present invention has many advantages. Because the present invention utilizes a hydraulic fluid that is not mixed with compressed natural gas, the cylinder is manufactured without the need for an internal piston or other device to keep the hydraulic fluid separate from the gas. Furthermore, because a piston is not required in the cylinder, fluid passages and valves may be provided in a fitting located at one end of the cylinder. The other end of the cylinder may be closed at this time. The cylinder has no internal piston and is closed at one end, so that the cost of manufacture is greatly reduced, and the cylinder is obviously more durable and has longer service life.

While the invention has been described in only two of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.

Claims (6)

1. A fuel delivery system for dispensing compressed natural gas into an external pressure vessel, comprising:

a reservoir with a pump suction line and a return line;

a hydraulic fluid contained in the reservoir;

at least one tank comprising an internal chamber containing compressed natural gas, a gas gate and a hydraulic fluid valve, each tank being in fluid communication with the gas stored in the internal chamber;

the hose is connected with the air valve and is used for connecting an external pressure container; and

a pump connected to the pump suction pipe for pumping the hydraulic fluid from the reservoir to the hydraulic fluid valve and then into physical contact with the gas stored in the internal chamber such that the pressure at the valve is maintained at a prescribed minimum as the gas flows from the valve through the hose and into the external pressure vessel;

a control valve that allows hydraulic fluid to return to the reservoir after all gas has been dispensed; and

a separation device that releases any gas entrained in the hydraulic fluid returned to the reservoir.

2. The fuel delivery system of claim 1, wherein the hydraulic fluid is of a type that does not mix with gas.

3. The fuel delivery system of claim 1, wherein the separation device is located in the reservoir.

4. The fuel delivery system of claim 1, wherein the separation device releases separated gas into an upper portion of the reservoir.

5. The fuel delivery system of claim 1, further comprising a metering valve in the reservoir that determines when a quantity of hydraulic fluid is pumped from the reservoir.

6. The fuel delivery system of claim 5, wherein the amount of hydraulic fluid is the same as the capacity of the tank.