Compressed Gaseous Fuel System

Abstract

Apparatus for enabling a conventional vehicle to be operated on a compressed gaseous fuel, characterized by a high degree of safety with features such as concentrating the high pressure portion of the apparatus into a section that is located outside of the passenger compartment for safety; employing a remote indicating fuel gauge that does not have a fuel connection inside the passenger compartment; employing double regulators with respective relief valves vented to a safe area; employing special factory-tested high pressure assemblies, and employing an excess flow shut-off valve for blocking flow in the event of a line failure. Also disclosed are specific embodiments such as employing a single stage compensated high pressure regulator for uniform performance until the container of compressed gaseous fuel is substantially empty; and parallel connected containers for increased range.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus for enabling a conventional internal combustion engine to operate on a compressed gaseous fuel. More particularly, this invention relates to apparatus for enabling a vehicle employing an engine that is normally operated on a conventional fuel to operate on a compressed gaseous fuel; and, in specific embodiments, is directed at safety features that are primarily useful where the vehicle has a passenger compartment, even if only for the driver.

2. Description of the Prior Art

Internal combustion engines have been operated on conventional fuel such as gasoline or diesel fuel for a relatively long time. Moreover, the internal combustion engines have been converted to operate on hydrocarbon fuels having shorter length molecules; such as, liquified petroleum gases or propane. Additionally, internal combustion engines have been operated at remote field locations on low pressure natural gas or methane. Experience with these remote engines indicates that the pollutant content of the exhaust gases is much less when the engine is operated on natural gas than when operated on the longer chain hydrocarbon molecules such as employed in gasoline. With the advent of concern over polluting our atmosphere, there has been increased interest in the use of short hydrocarbon molecules as the fuel for the internal combustion engine, since these molecules result in fewer contaminating free radicals spewed in the atmosphere in the exhaust gases from the engine.

For example, it has been found that an internal combustion engine such as run in a pick-up truck has exhaust gases that are remarkably free of the more objectionable pollutants; such as, hydrocarbon free radicals and even the nitrogen containing pollutants like the brown nitrous oxide which is a constituent of the smog-type haze in the larger cities. The reason for the observed low content of the pollutants is not exactly clear but the low content makes desirable the use of compressed gaseous fuel such as compressed natural gas, comprising the short hydrocarbon molecules like methane.

One of the objectionable features of the prior art attempts to employ methane was the absence of adequate safety features. This was due primarily to the fact that the internal combustion engines were operated in remote locations away from the more populous areas in powering gas compressors or the like that did not have passengers associated therewith. It is sociologically imperative that any system, or apparatus, which would allow converting a vehicle to operate on compressed gaseous fuel incorporate safety factors to compensate for the increased hazards of which the general public may not be fully aware.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, partly schematic, illustrating one embodiment of this invention employed on a conventional pick-up truck.

FIG. 2 is a more detailed side elevational view, also partly schematic, of the embodiment of FIG. 1.

FIG. 3 is a graph of the flow rate versus pressure to illustrate desirable performance characteristics of an embodiment of this invention.

FIG. 4 is a front elevational view of a fuel gauge means for monitoring the quantity of the fuel in accordance with one embodiment of this invention.

FIG. 5 is a side elevational view, partly cut away, illustrating elements of the embodiment of FIG. 4.

FIG. 6 is a schematic diagram illustrating the remote fuel indicator in accordance with an embodiment of this invention.

FIG. 7 is a side elevational view of a high pressure section containing several cylinders of compressed gaseous fuel for increased range, in accordance with another embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS:

Referring to FIGS. 1 and 2, the apparatus 11 is illustrated installed in a vehicle such as a pick-up truck 13 employing a conventional engine 15. By conventional engine is meant an internal combustion engine that runs on a conventional fuel such as gasoline, diesel fuel, or the like. The apparatus 11 comprises the major elements or subassemblies of at least one container 17, high pressure assembly 19, including fill connection 21, fuel gauge means 23 for monitoring the quantity of the compressed gaseous fuel in the container 17, and high pressure regulator 25, medium pressure relief valve 27, on-off valve 29, low pressure regulator 31, gas-air mixer 33, and on-off valve 35 for turning off conventional fuel when the compressed gaseous fuel is being employed. As illustrated, the container 17, the high pressure assembly 19, the fill connection 21, the fuel gauge means 23, and the high pressure regulator 25 are arranged in a high pressure section 37 that is located rearwardly of the passenger comparatment 39 for safety. In FIGS. 1 and 2, the high pressure section 37 is illustrated as being installed in the pick-up bed portion of a pick-up truck 13. In an automobile, the high pressure section is customarily located in the truck, outside of the passenger compartment and out of sight.

There is at least one container 17; and, preferably, a plurality. For example, as illustrated in FIG. 7, there may be seven or more containers 17 for increased range of the vehicle. Any suitable high pressure container that is designed to hold the desired pressure of the compressed gaseous fuel may be employed. In a preferred form of construction, methane cylinders are employed. The container may hold, for example, compressed gaseous fuel up to 2,200 pounds per square inch gauge (psig). For example, regulatory agencies such as the Department of Transportation specify acceptable cylinder pressures for respective vehicles.

The high pressure assembly 19 comprises high pressure fittings 40; for example, fittings to match the CGA (Compressed Gas Association) 350 methane connection on the methane cylinders. The high pressure assembly illustrated comprises a high pressure manifold including respective conduit means such as tubing 41 which may be of stainless steel; and fittings such as cross 43, FIG. 2, at least the interior half of fill connection 21, check valve 47, fuel gauge means 23, high pressure regulator 25, high flow shut-off valve 87, on-off valve 29, and the respective adapter fittings 48 for connecting the tubing 41 to the container-matching fittings 40. Because of the need for safety, the high pressure assembly 19 is preferably factory assembled and tested for leaks before it is released to be sold or used.

The fill connection 21 is connected into the high pressure assembly 19 for refilling the container 17 with the gaseous fuel. The fill connection 21 may comprise any convenient, sealing, connect-disconnect fitting. For additional safety, at least check valve means are disposed on both sides of the connect-disconnect fitting. The check valve means are operable to permit flow into the high pressure assembly when the connect-disconnect fitting is connected; and to prevent flow from the free ends of the connect-disconnect fitting when disconnected. For example, a conventional quick-connect fitting having respective bayonet and receiving connector portions may be employed. In the conventional quick-connect fitting, the check valves therein may be moved to the open position when the bayonet is inserted into the receiving connector portion for connection; but are moved to the closed position when the bayonet is removed so as to prevent flow from the disconnected ends, as might occur when the connection is broken; thereby reducing fire hazard and the like. A check valve 47, FIGS. 2 and 7, is also provided to permit flow in one direction, as indicated by the arrow 53 so as to enable filling the containers, but to prevent flow in the opposite direction. This check valve 47 is includes to prevent reverse flow when the quick-connect halves are coupled and a second vehicle at lower tank pressure is connected to a fill system; this prevents partial emptying of the first vehicle. If desired, a single valve such as valve 55, FIG. 7, may be provided to prevent flow outwardly from the manifold of the high pressure assembly, or, as illustrated in FIG. 2, the respective valves 57 on each respective cylinder may be employed to control the flow from the cylinders.

The fuel gauge means 23 is screwed into cross 43 and includes a pressure responsive element such as bourdon tube 51, FIGS. 5 and 6, in fluid connection with the container for monitoring the pressure therein. Any high pressure gauge may be employed as fuel gauge means 23 as long as it is commensurate with the range of pressure employed in the containers 17. Preferably, the fuel gauge means 23 includes, also, a remote indicating gauge 59, FIG. 6, that may be emplaced in the passenger compartment to read the quantity of fuel. For safety, no line containing the gaseous fuel should be run into the passenger compartment, so the remote indicating gauge 59 must operate without directly sensing the pressure. It has been recognized that the running of lines with the combustible gaseous fuel into the passenger compartment is undesirable, particularly where the fuel is at super atmospheric pressure. Several states have enacted statutes prohibiting employing any direct reading pressure gauges, with the attendant pressurized fuel lines, in the passenger compartment. As illustrated in FIGS. 1, 2 and 6, the pressure responsive element such as the bourdon tube 51 in the fuel gauge means 23 is disposed adjacent the container 17 and outside the passenger compartment. Preferably, the gauge encompassing the bourdon tube 51 will also have a direct reading dial and pointer thereon to facilitate monitoring the amount of fuel and the quantity that is filled when fuel is added via the fill connection 21, without requiring continually adverting to the remote fuel indicator 59 in the passenger compartment. In the preferred form in which the remote indicating fuel gauge 59 is employed, a transducing means 61 is employed for converting the pressure into a continuous, single-valued transmissible signal which the remote indicating fuel gauge 59 can use to effect a visual display of the quantity of the fuel in response to the signal. As illustrated, the transducing means 61 comprises a magnet 63 that is carried by a pointer 65, FIGS. 4 and 5; a potentiometer 67; and a power source such as battery 69 that is electrically connected serially with the potentiometer 67. As illustrated, the potentiometer 67 is a circular potentiometer. The circular potentiometer 67 is disposed above the magnet 63 and has a potentiometer wiper 71 that is magnetically coupled with the magnet 63 carried by pointer 65. Consequently, the potentiometer wiper 71 will follow the pointer 65. The potentiometer wiper 71 is electrically conductive and has a brush that wipes along the circular resistor 73 of the circular potentiometer 67. As the potentiometer wiper 71 assumes a predetermined position, a unique voltage output is effected. Expressed otherwise, the voltage output is a function of the position of potentiometer wiper 71 on the potentiometer resistor 73. The remote indicating fuel gauge 59 comprises a galvanometer type instrument such as a voltmeter that is responsive to the voltage and is calibrated to read the voltage as a proportion of a full container of the gaseous fuel.

The high pressure regulator 25 is connected into the high pressure assembly 19 and directly with the valve 57 of cylinder 17, FIG. 2, for regulating a dowstream pressure; such as, through on-off valve 29; to a medium pressure. Preferably, the high pressure regulator 25 is a single stage compensated regulator for uniform performance until the container 17 is substantially empty, as illustrated in FIG. 3. Therein, the flow rate, in standard cubic feet per hour (scfh); and, consequently, engine performance; is a flat curve 75 regardless of the pressure of the gaseous fuel in the container 17, FIG. 2, until the container 17 gets below the differential pressure necessary for proper flow of fuel and operation of the low pressure regulator 31. This low pressure denotes a substantially empty container 17. Better maximum speed results from such flat curves. A desirable single stage compensated regulator is described and claimed in copending application Ser. No. 827,711, entitled "Single Stage, Compensated Pressure Regulator," inventor Ray R. Zimmer, filed May 26, 1969, assigned to the assignee of this invention. The medium pressure may range from several psi to as high as 150 psi.

The medium pressure relief vlave 27 is connected with the downstream side of the high pressure regulator 25 for venting the gaseous fuel at pressures greater than a preset maximum. The medium pressure relief valve 27 has a means such as a covered screw (not shown) for altering the preset maximum. Any conventional medium pressure relief valve may be employed as long as its range of preset maximum pressures is commensurate with the medium pressure desired in the conduit means 77 conveying the gaseous fuel to the engine 15. While the medium pressure relief valve 27 may be vented directly to the atmosphere in an open pick-up bed, it is preferred that it be vented, as via conduit means 79, to a safe place such as at the rear of the vehicle. The conduit means 79 is shown in dashed lines in FIG. 2. The conduit means 79 is necessary when the high pressure section 37 is emplaced in the trunk of a vehicle, in order to prevent the build up of explosive gases in the trunk in the event of pressure relief.

The on-off valve 29 is interposed in the conduit means 77 for preventing or permitting flow of the compressed gaseous fuel to the engine 15. Preferably, the on-off valve 29 is a solenoid operated on-off valve. Such on-off valves are conventional. Preferably also, the on-off valve 29 is connected with the downstream side of the high pressure regulator 25 so that it may have a relatively less expensive low pressure body instead of requiring a body that is structurally strong enough to withstand the high pressure of the compressed gaseous fuel in the high pressure assembly 19. As illustrated, the on-off valve 29 is a solenoid operated valve having a solenoid 81 that is electrically connected with ground and via conductor 83 with a switch 85 located inside of of the passenger compartment 39. The switch 85 may comprise a three position toggle switch effecting, in two of the positions, respective on and off operation of the solenoid 81. Conventionally, the switch 85 will be connected through a master switch such as the ignition switch so that the operation of the switch 85 is not necessary each time the engine is started or stopped.

The conduit means 77 effects a closed passageway for the transmission of the gaseous fuel from the high pressure regulator 25 to the gas-air mixer 33 on the engine. The conduit means 77 necessarily incorporates the requisite conventional fittings for connection with the elements interposed therein; for example, the on-off valve 29; a high flow shut-off valve 87, if emplaced therein; and the low pressure regulator 31. The conduit means 77 may comprise pressure tubing 89 and a flexible hose 91 for carrying the respective medium and low pressures. For example, the tubing 89 may be nylon tubing reinforced with steel mesh and covered for protection, or metallic tubing such as steel, copper or aluminum.

The low pressure regulator 31 is interposed into the conduit means 77 downstream of the on-off valve 29. The low pressure regulator 31 reduces the medium pressure to a low pressure for feeding to the gas-air mixer 33. The low pressure may range from a few inches of water to a few psi, depending upon the type of gas-air mixer 33 employed.

To add an additional safety feature, we have resorted to a low pressure relief valve that is connected with the downstream side of the low pressure regulator to vent the gaseous fuel in the event the low pressure becomes greater than a second preset maximum. This protects the gas-air mixer 33 as well as other low pressure components of the system. We employ a low pressure relief valve that is connected into the body of the low pressure regulator 31. Such low pressure relief valves are conventional and need not be described in detail herein.

The gas-air mixer 33 is connected; for example, via a conventional carburetor 93; with the intake manifold of the engine 15, and with the hose 91. The gas-air mixer 33 has means for admixing a combustion supporting gas such as air with the gaseous fuel. Any of the conventional gas-air mixers may be employed. We have found the gas-air mixer supplied commercially by Impco to be satisfactory.

The on-off valve means 35 is interposed in a line supplying the conventional fuel for stopping the flow of the conventional fuel to the engine when the gaseous fuel is being employed. Preferably, the on-off valve means 35 comprises a solenoid operated on-off valve having solenoid 95 for effecting the on-off operation. The solenoid 95 is connected with ground and via conductor 97 with fuel control switch 85. The solenoid 95 operates conversely to solenoid 81 such that the flow of conventional fuel is stopped when the flow of the gaseous fuel is started or the flow of conventional fuel is started when the flow of gaseous fuel is stopped. Any of the conventionally operable solenoid-operated valves may be employed. The pressure that the body of the valve is designed to withstand will be determined by the type of fuel being employed. Ordinarily, where gasoline and diesel fuel are being employed, a low pressure body is adequate to withstand the pressure of the conventional fuel pump.

We have found it advantageous from a safety standpoint to provide an excess flow shut-off valve, such as high flow valve 87 for blocking the flow in the event there is a failure at some point in the flow path of the compressed gaseous fuel. For example, if tubing 89 were ruptured, the excess flow valve 87 would close and prevent the flow of the gaseous fuel which would otherwise result. The excess flow valves are conventional and are commercially available. Ordinarily, they comprise a check valve means such as a ball or poppet that is held in a predetermined position, as by suitable biasing means, but which is operated into a shut position against a seat to stop the flow as long as the rate of flow tends to be above a predetermined maximum. The predetermined maximum is responsive to pressure differential. The high flow shut-off valve 87 is located downstream of the high pressure regulator 25 for constant inlet pressure. Since the details of the excess flow shut-off valve are not being claimed, per se, and are commercially available, there is no need to supply the well-known details thereof.

In operation, the mechanical and electrical elements are installed to effect the system described hereinbefore and illustrated in the figures. The containers 17 are filled with the compressed natural gas to the desired pressure; for example, 2,200 psig. The high pressure connections are checked to ensure there are no leaks. The fuel control switch 85 is set for the conventional fuel; for example, the gasoline position; and the engine is started. Then, the lines and connections are checked for leaks at the on-off valve means 35. The engine is converted to run on gaseous fuel by positioning the fuel control switch 85 in another position and the engine started and the connections checked for any compressed gaseous fuel leaks. Smooth running of the engine on gaseous fuel is accomplished by adjusting the lean-rich adjusting screw of the gas-air mixer 33 to obtain a smooth idle. On the other hand, if the supply of compressed gaseous fuel becomes low, or it is desirable to run the engine on the conventional fuel for other reasons, the fuel control switch 85 is operated to the opposite position and transistion to the conventional fuel is smoothly made. If desired, the low pressure regulator may be preset to maintain from five to ten inches of water pressure on the compressed gaseous fuel. If natural gas is to be the only fuel used, the engine ignition timing may be set to 7.degree. to 10.degree. more advanced than the manufacturer's recommendations for the conventional fuel. For increased economy and performance, if natural gas is to be the prime fuel the spark plug gap setting should be decreased to half of the normal gap setting. The engine timing is set at the maximum recommended by the vehicle manufacturer if satisfactory operation is desired on both fuels.

The compressed gaseous fuel should be dried to have a dew point of at last -65.degree. Fahrenheit at 2,250 psig, because, otherwise, the large pressure drop between a filled container 17 and the medium pressure conduit means 77 lowers the temperature sufficiently to cause operational difficulties.

The materials of construction ordinarily employed in this art are adequate for use herein and no new exotic materials need be employed.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention.

Claims

1. In apparatus for enabling a vehicle engine normally employing a conventional fuel to operate on a second fuel, and normally including:

a fuel-air mixer connected with the intake manifold of said engine and with a low pressure regulator and having means for admixing a combustion supporting gas with said second fuel;

on-off valve interposed in a conduit means for carrying said second fuel to said vehicle engine; said conduit means being connected with said fuel-air mixer and with a pressure regulator;

low pressure regulator interposed in said conduit means downstream of said on-off valve for reducing upstream pressure to a low pressure in the range of from a few inches of water to a few pounds per square inch guage (psig) for supplying to said fuel-air mixer; and

on-off valve interposed in a fuel line supplying said conventional fuel for stopping flow of said conventional fuel to said engine when said second fuel is being employed; the improvement comprising:

a. a high pressure section located outside of the passenger compartment of said vehicle for safety, said high pressure section including:

i. at least one container of a compressed gaseous fuel under superatmospheric pressure; said compressed gaseous fuel serving as said second fuel; said container being capable of withstanding pressure in excess of 1,000 pounds per square inch gauge (psig); and

ii. a high pressure assembly connected with said container of compressed gaseous fuel; said high pressure assembly including a first high pressure fitting for said container of said compressed gaseous fuel; high pressure tubing connected to said first high pressure fitting; a second high pressure fitting connected to said tubing;

a fill connection connected with said second high pressure fitting and into the remainder of said high pressure assembly for refilling said container with said compressed gaseous fuel;

fuel gauge means connected responsively with said second high pressure fitting and into the remainder of said high pressure assembly for monitoring the quantity of said compressed gaseous fuel in said container;

and high pressure regulator connected with said second high pressure fitting and into the remainder of said high pressure assembly for regulating a downstream pressure to a medium pressure in the range of from several psig to 150 psig; and

b. medium pressure relief valve connected with the downstream side of said high pressure regulator for venting said gaseous fuel at pressures greater than a preset maximum; said medium pressure relief valve having means for altering said preset maximum; and

2. The apparatus of claim 1 wherein said high pressure regulator comprises

3. The apparatus of claim 1 wherein said high pressure assembly is

4. The apparatus of claim 1 wherein said fill connection includes a convenient, sealing connect-disconnect fitting and has check valve means disposed on both sides of the joint of said fill connection, said check valve means being operable to permit flow when said fitting is connected for filling said container and operable to prevent flow from either of the

5. The apparatus of claim 1 wherein a low pressure relief valve is connected with the downstream side of said low pressure regulator for venting said gaseous fuel at pressures above a second preset maximum low pressure; said low pressure relief valve having means for altering said

6. The apparatus of claim 1 wherein said apparatus is installed in an automobile, said high pressure section is installed in the trunk of said automobile; and said medium pressure relief valve has a vent pipe that traverses to the exterior of said trunk and to a safe place for venting

7. The apparatus of claim 1 wherein an excess flow shut-off valve is incorporated into said apparatus for blocking flow from said high pressure assembly in the event there is a failure at some point that would otherwise vent said gaseous fuel at a rate greater than a predetermined

8. The apparatus of claim 1 wherein there are a plurality of containers of said compressed gaseous fuel and said high pressure assembly comprises a manifold interconnected with said plurality of containers; said containers

9. The apparatus of claim 1 wherein said fill connection has check valve means and a redundant check valve is interposed in the flow line to

10. In apparatus for enabling a vehicle engine normally employing a conventional fuel to operate on a second fuel, and normally including:

a fuel-air mixer connected with the intake manifold of said engine and with a low pressure regulator and having means for admixing a combustion supporting gas with said second fuel;

on-off valve interposed in a conduit means for carrying said second fuel to said vehicle engine; said conduit means being connected with said fuel-air mixer and with a pressure regulator;

low pressure regulator interposed in said conduit means downstream of said on-off valve for reducing upstream pressure to a low pressure in the range of from a few inches of water to a few pounds per square inch gauge (psig) for supplying to said fuel-air mixer; and

on-off valve interposed in a fuel line supplying said conventional fuel for stopping flow of said conventional fuel to said engine when said second fuel is being employed; the improvement comprising:

a. at least on container of a compressed gaseous fuel under superatmospheric pressure; said container being capable of withstanding pressure in excess of 1,000 pounds per square inch gauge (psig); said compressed gaseous fuel serving as said second fuel;

b. high pressure conduit and fittings connected with said container of gaseous fuel;

c. a fill connection connected with said high pressure conduit and fittings for refilling said container with gaseous fuel;

d. high pressure regulator for regulating a downstream pressure to a medium pressure in the range of from several psig to 150 psig; said high pressure regulator being connected at its upstream side with said high pressure conduit and fittings;

e. medium pressure relief valve connected with the downstream side of said high pressure regulator and said conduit means for venting said gaseous fuel at pressures greater than a preset maximum; said medium pressure relief valve having means for altering said preset maximum;

f. a gas-air mixer serving as said fuel-air mixer; and

g. fuel gauge means including:

i. a pressure responsive element in fluid communication with said container for monitoring pressure therein, said pressure responsive element being disposed adjacent said container and outside the passenger compatment of the vehicle; said pressure responsive element being a pressure gauge that displays the pressure adjacent said container also, facilitating monitoring during filling;

ii. transducing means for converting said pressure into a single-valued transmissible signal;

iii. remote indicator gauge means disposed in said passenger compartment and connected with said transducer means for effecting a visual display of

11. The apparatus of claim 10 wherein said pressure gauge has a pointer and said transducing means comprises a magnet that is carried by said pointer, a potentiometer that is disposed above said magnet; said potentiometer having as its potentiometer wiper an electrically conductive magnetic follower that is connected with a source of power, that is mounted for movement along substantially the same path as said pointer and freely mounted so as to follow the movement of said magnet on said pointer, and that effects a voltage output that is a function of the position of the magnetic follower on the potentiometer resistor; and said remote indicator gauge means comprises a galvanometer that is responsive to said voltage and is calibrated to read said voltage as a proportion of a full container

12. The apparatus of claim 10 wherein said pressure gauge has a pointer and said transducing means comprises a magnet that is carried by said pointer, a circular potentiometer that is disposed above said magnet; said circular potentiometer having as its potentiometer wiper an electrically conductive magnetic follower that is connected with a source of power, that is pivotally mounted for pivotal movement about substantially the same axis as said pointer and freely mounted so as to follow rotational movement of said magnet on said pointer, and that effects a voltage output that is a function of the position of the magnetic follower on the potentiometer resistor; and said remote indicator gauge means comprises a galvanometer that is responsive to said voltage and is calibrated to read said voltage as a proportion of a full container of said gaseous fuel.