PRESSURIZED LIQUID FUEL TANK SYSTEM AND VEHICLE INCLUDING SAME

Abstract

A pressurized liquid fuel tank system arranged to contain a first mass of liquid fuel such, as Dimethyl-Ether (DME) is provided. The system includes a first tank having a first volume, a second tank having a second, volume, a first conduit, between a top of the first tank and a top of the second tank, and a second conduit between the first tank and a bottom of the second tank, wherein a sum of the first volume and the second volume is designed to equal a sum of a first mass volume of the first mass of liquid fuel plus an expansion volume equal to at least 5% of the first mass volume. A vehicle with such a fuel tank system is also disclosed.

Claims

1. A pressurized liquid fuel tank system, the fuel tank system being arranged to contain a first mass of liquid fuel, comprising: a first tank having a first volume; a second tank having a second volume; a first conduit between a top of the first tank and a top of the second tank; and a second conduit between the first tank and a bottom of the second tank; wherein a sum of the first volume and the second volume is designed to equal a sum of a first mass volume of the first mass of liquid fuel plus an expansion volume equal to at least 5% of the first mass volume.

2. The pressurized liquid fuel tank system as set forth in claim 1, comprising a one-way pressure relief valve in the first conduit, the pressure relief valve only permitting flow from the first tank to the second tank through the first conduit when pressure in the first tank exceeds a first pressure.

3. The pressurized liquid fuel tank system as set forth in claim 1, comprising a valve in the second conduit and means for opening the valve when a liquid level in the first tank is below a point where the second conduit opens into the first tank.

4. The pressurized liquid fuel tank system as set forth in claim 3, wherein the opening means comprises at least one of a float and an electronic sensor in the first tank.

5. The pressurized liquid fuel tank system as set forth in claim 4, wherein the opening means comprises a controller linked to the float and arranged to send a signal to the valve when the liquid level is below the point where the second conduit opens into the first tank.

6. The pressurized liquid fuel tank system as set forth in claim 3, wherein the valve is a normally closed valve.

7. The pressurized liquid fuel tank system as set forth in claim 1, wherein the first mass volume is at least as large as the first volume and is greater than the second volume.

8. The pressurized liquid fuel tank system as set forth in claim 1, wherein the first mass volume is less than the first volume and is greater than the second volume.

9. The pressurized liquid fuel tank system as set forth in claim 1, wherein the second conduit extends to both of the first tank and the bottom of the second tank.

10. A vehicle comprising a pressurized liquid fuel tank system, the fuel tank system being arranged to contain a first mass of liquid fuel, comprising: a vehicle frame; and the pressurized liquid fuel tank system mounted on the frame, comprising a first tank having a first volume, a second tank having a second volume, a first conduit between a top of the first tank and a top of the second tank, and a second conduit between the first tank and a bottom of the second tank, wherein a sum of the first volume and the second volume is designed to equal a sum of a first mass volume of the first mass of liquid fuel plus an expansion volume equal to at least 5% of the first mass volume.

11. The vehicle as set forth in claim 10, wherein the frame comprises at least one rail, and the first tank and the second tank are mounted on the frame on opposite sides of the at least one rail.

12. The vehicle as set forth in claim 11, wherein the frame comprises at least two rails, and the first tank and the second tank are mounted to different ones of the at least two rails.

13. The vehicle as set forth in claim 10, wherein the frame comprises at least two rails, and the first tank and the second tank are mounted to different ones of the at least two rails.

14. The vehicle as set forth in claim 10, comprising a one-way pressure relief valve in the first conduit, the pressure relief valve only permitting flow from the first tank to the second tank through the first conduit when pressure in the first tank exceeds a first pressure.

15. The vehicle as set forth in claim 10, comprising a valve in the second conduit and means for opening the valve when a liquid level in the first tank is below a point where the second conduit opens into the first tank.

16. The vehicle as set forth in claim 15, wherein the valve is a normally closed valve.

17. The vehicle as set forth in claim 10, comprising a port for introducing a fueling nozzle into the first tank or a fill line for the first tank, a valve in the second conduit, and means for closing the valve when the fueling nozzle is introduced into the first tank or the fill line.

18. The vehicle as set forth in claim 10, comprising an engine fueled by DME in the fuel tank system, the engine being adapted to be turned on and off, a valve in the second conduit, and means for closing the valve when the engine is turned off.

19. The vehicle as set forth in claim 18, wherein the closing means is arranged, after closing the valve when the engine is turned off, to keep the valve closed when the engine is turned back on.

20. The vehicle as set forth in claim 10, wherein the second tank comprises a plurality of second tanks.

21. The vehicle as set forth in claim 20, wherein the first conduit comprises a plurality of first conduits between the top of the first tank and the tops of each of the plurality of second tanks.

22. The vehicle as set forth in claim 20, comprising at least one first conduit between the top of the first tank and the top of at least one of the plurality of second tanks.

23. The vehicle as set forth in claim 20, comprising at least one second conduit between the first tank and the bottom of at least one of the plurality of second tanks.

24. The vehicle as set forth in claim 20, wherein the second conduit extends to both of the first tank and the bottom of the second tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The features and advantages of the present invention are well understood by reading the following detailed description in conjunction with the drawings in which like numerals indicate similar elements and in which:

[0015] FIGS. 1-4 are schematic views of a pressurized liquid fuel tank system according to aspects of the present invention, wherein fuel tanks are filled to different levels; and

[0016] FIG. 5 is a schematic view of a vehicle including a pressurized liquid fuel tank system according to an aspect of the present invention.

DETAILED DESCRIPTION

[0017] A pressurized liquid fuel tank system 21 according to an aspect of the present invention is shown in FIGS. 1-4. The fuel tank system 21 is arranged to contain a first mass of pressurized fuel 23L. For purposes of discussion, the pressurized liquid fuel tank system 21 and method according to the present invention will be described in connection with pressurized liquid Dimethyl Ether (DME), except where otherwise indicated, it being appreciated that the present invention is applicable to other types of pressurized liquid fuels.

[0018] The liquid DME 23L can expand in volume as temperature rises, and, DME vapor 23V will also typically occupy some volume of the fuel tank system, particularly as temperature of the liquid DME rises. The first mass volume of the first mass of liquid DME shall be considered to be equal to a volume or range of volumes of the first mass at typical temperatures and pressures at which DME is dispensed from conventional storage tanks or ranges of such temperatures and pressures. For purposes of the present discussion, it shall be assumed that the typical pressure is atmospheric pressure (at sea level) and the typical temperature is approximately 70 F. (21 C.), with ranges of pressure and temperature varying with climate in the particular geographical location, storage conditions, altitude, and other conditions that can affect the volume of DME. Today, many modern fuel dispensers include flow meters and temperature sensors for sensing the temperature of fuel being dispensed to make sure that the amount of fuel dispensed is corrected for the ambient temperature. Older systems relied on the weight of the fuel.

[0019] As seen in FIG. 1, the fuel tank system 21 includes a first tank 25 having a first volume V1 and a second tank 27 having a second volume V2. A first conduit 29 extends between a top of the first tank 25 and a top of the second tank 27. For purposes of the present discussion, the tops and of the first tank 25 and the second tank 27 can be considered to be any points on the tanks that are above the level LF1 and LF2 to which the tanks are intended to be filled with liquid DME so that the first conduit 29 will ordinarily be solely used for permitting gas flow between the first and second tanks. The tank 25 and 27 may, however, be filled above the levels LF1 and/or LF2, such as when liquid DME expands at elevated temperatures.

[0020] A second conduit 31 extends between the first tank 25 and a bottom of the second tank 27. The second conduit 31 may extend between the bottom of the first tank 25 and the bottom of the second tank 27, however, the second conduit is ordinarily intended to permit flow of liquid DME from the second tank to the first tank. To facilitate this flow of liquid DME, it can be desirable to have the second conduit 31 connect to the first tank 25 at some point 49 above, usually substantially above, the bottom of the first tank.

[0021] A sum of the first volume V1 and the second volume V2 is designed to equal a sum of a first mass volume of the first mass of liquid DME plus an expansion volume ordinarily equal to some percentage (for example, 5%) greater than the first mass volume when volume is filled to LF1. For DME, the expansion volume will typically be at least 15% of the first mass volume when volume is filled to LF1 and, for propane, at least 20%. In a particularly preferred embodiment, the expansion volume will equal 5-25% of the first mass volume and, more preferably, 15-20% of the first mass volume. The expansion volume should, of course, at least equal any percentage of the first mass volume that is required by any relevant statute or regulation.

[0022] The fuel tank system 21 can include a one-way pressure relief valve 33 in the first conduit 29. The pressure relief valve 33 ordinarily only permits gas and/or liquid flow from the first tank 25 to the second tank 27 through the first conduit 29 when pressure in the first tank exceeds a first pressure. The first pressure is typically a pressure selected so to provide a substantial safety factor between the first pressure and the bursting pressure of the first tank 25 and is, in any event, at least any safety factor that is required by any relevant statute or regulation. The first and second tanks 25 and 27 will ordinarily also be provided with separate conventional pressure relief valves (not shown) that will permit dumping of fuel or vapor outside of the fuel tank system in the event of over-pressure.

[0023] FIG. 1 shows the first tank 25 filled with DME liquid 23L and vapor 23V at a pressure below the pressure necessary to open the pressure relief valve 33 to the second tank 27. FIG. 2 shows the first tank 25 filled with DME liquid 23L and vapor 23V at a pressure sufficient to open the pressure relief valve 33 so that DME vapor enters the second tank 27. FIG. 3 shows the first tank 25 filled with DME liquid 23L that has expanded so as to flow through the pressure relief valve 33 and the first conduit 29 to the second tank 27, and where the entire volume of DME vapor has flowed to the second tank 27. FIG. 4 shows the first tank 25 after DME liquid 23L has been drawn off, such as by being consumed in an engine, and DME liquid 23L and vapor 23V are present in both the first and second tanks 25 and 27.

[0024] The first tank 25 is typically provided with a shut-off valve 4 in a fill line 47 to the first tank to prevent filling of the tank above the level LF1. The second tank 27 can also be provided with a shut-off valve (not shown) to prevent filling above the level LF2. In a presently preferred embodiment, no shut-off valve is required for the second tank 27 because preventing filling of the first tank 25 above the level LF1 will also prevent filling of the second tank above the level LF2 due to the presence of various structures such as one-way valves that can be provided so that fluid flow will ordinarily not be permitted from the first tank to the second tank. Additionally, the bottom of the second tank 27 can be vertically above the port 49 where the second conduit 31 connects to the first tank 25, and a valve 35 can be provided in the second conduit and can be closed when the liquid level in the first tank is above the port or above the bottom of the second tank to prevent liquid flow from the first tank to the second tank through the second conduit.

[0025] Means for opening and closing the valve 35 can be provided when a liquid level in the first tank 25 is below and above, respectively, a point or level L1 in the first tank of the port 49 where the second conduit opens into the first tank (or the bottom of the second tank 27). The valve 35 will ordinarily be a normally closed valve to avoid unintentionally permitting fluid flow from the first tank 25 to the second tank 27 otherwise than through the first conduit 29. The point or level L1 can be fairly high on the first tank 25, such as at about 80%-90% of the full level LF1, so that liquid in the second tank 27 will promptly drain from the second tank to the first tank 25. The point or level L1 will ordinarily be vertically even with or below the bottom of the second tank 27 to permit the second tank to drain into the first tank by gravity and by the force of vapor pressure in the second tank if its vapor pressure is higher than the first tank. A pump (not shown) may be provided to transfer the DME liquid from the second tank 27 to the first tank 25 if, for some reason, it was desired to mount the first tank higher than the second tank.

[0026] The opening and closing means can comprise a conventional structure such as a float 39 in the first tank 25 that is linked directly to the valve 35, such as by an arm or lever 41, to open the valve when the float is below the point or level L1 and close it when the float is above L1. The valve 35 will ordinarily be, but is not necessarily, an electric valve and the opening and closing means may further comprise a controller 43 that is linked mechanically, electrically, or by other suitable means, such as by radio or other detectable signals or forces, to the float 39 and that is arranged to send a signal to open the valve 35 in the second conduit 31 when the controller determines, by virtue of the position of the float, that the liquid level is below the point or level L1, and to close the valve 35 when the controller determines that the liquid level is above L1.

[0027] Means is also typically provided for opening and closing a fill valve 45 in a fill line 47 to the first tank 25 when the first tank is filled to the filled level LF1, and typically comprises the same opening and closing means for opening and closing the valve 35 in the second conduit 31 when the liquid level in the first tank is below and above, respectively, the point or level L1, such as a float 39 or a float in combination with the controller 43. When the first tank 25 is filled to the level LF1, the opening and closing means closes the fill valve 45 so that no additional fuel can be dispensed into the first tank 25 and, when the first tank is filled to a level below the level LF1, the opening and closing means opens the fill valve 45 to permit additional fuel to be dispensed into the first tank. Typically, but not necessarily, the level LF1 is set so that the fill valve 45 will close when there is a predetermined percentage, e.g., 5%, of the volume V1 of the first tank 25 that is unfilled. The fill line may, however, lead to both the first and the second tanks, and separate opening and closing means may be provided for both the first and second tanks, and may shut off the fill line to the first and second tanks at the same or at different times for each tank depending upon where the levels LF1 and LF2 are set for each tank.

[0028] In a presently preferred embodiment, the first tank 25 ordinarily functions as the main fuel tank while the second tank's 27 function is typically as an expansion volume to accommodate increased pressure and volume as temperature of the fuel in the fuel tank system 21 rises. In such an embodiment, the first mass volume can be at least as large as the first volume V1 of the first tank 25 or less than the first volume of the first tank, and the first mass volume is typically greater than the second volume V2 of the second tank 27.

[0029] A vehicle 101 comprising a DME fuel tank system 21 is shown in FIG. 5. In addition to the fuel tank system 21, the vehicle includes a vehicle frame 103. The DME fuel tank system 21 is mounted on the frame. The frame 103 comprises at least one rail 105, and the first tank 25 and the second tank 27 are mounted on the frame on opposite sides of the at least one rail. The frame 103 ordinarily comprises at least two rails 105 and 107. The first tank 25 and the second tank 27 (shown in phantom) can be mounted to different ones of the at least two rails. It is also possible to have both a second tank 27 mounted on the same rail as the first tank 25 and one or more additional tanks 27 mounted on another rail. It will be appreciated that the multi-tank fuel tank system 21 facilitates advantageous packaging arrangements for the fuel tanks that might not be available in a fuel tank system arranged to carry the same mass of fuel but that uses only a single, larger tank that provides for both the fuel volume and the expansion volume. Another embodiment (not shown) involves sharing of a single expansion tank with two main tanks for packaging convenience. The single expansion tank would have sufficient expansion volume for two main tanks. Use of a single expansion tank could facilitate preventing fuel being returned to either main tank from exceeding the full level, and could facilitate maintaining equal fuel levels in both main tanks.

[0030] In a presently preferred embodiment, the first tank 25 includes a port 51 that connects the first tank to a fill line 47 for introducing a fueling nozzle 109 into the first tank or into the fill line. Means for opening and closing the valve 35 in the second conduit 31 when the fueling nozzle 109 is removed from and introduced into the first tank 25 or the fill line 47 can be provided to ensure that only the first tank is able to be filled with liquid fuel. The opening and closing means can include structures such as a device 113 in the first tank 25 or the fill line 47 to detect the presence or absence of a fueling nozzle and send a signal to a controller 43 for closing or opening, respectively, the valve 35. For example, the device 113 might comprise a sensor that senses or a switch that closes when a fueling nozzle 109 is introduced into the first tank 25 or into the fill line 47 and physically contacting the sensor or switch and permits a signal to be sent to the controller 43 that causes the controller to close the valve 35, and that senses or opens when the fueling nozzle is removed to stop the sending of the signal to the controller and that causes the controller to open the valve. The valve 35 can be controlled by the arm of the float 39. When the first mass volume is at or above line L1, the valve 35 will be closed and, when the first mass volume is below L1, the valve 35 will be open. The control of the valve 35 based on the position of the float 39 can be performed by a mechanical control or via the controller 43. It will be appreciated that the level in the tank 25 can be measured by means other than a float, such as electronic sensors involving ultrasound, radar, or optical sensing.

[0031] In a presently preferred embodiment, the vehicle 101 includes an engine 115 fueled by DME in the fuel tank system 21. A feed line 117 extends from, typically, the first tank 25 to the engine 115 where, typically, some fuel is injected into cylinders (not shown) in the engine and some fuel is circulated through components of the engine to cool engine components and is then returned to the first tank through a return line 119. The engine 115 is adapted to be turned on and off by conventional means, such as by a key operated electronic control system 121. Means can be provided to automatically close the valve 35 in the second conduit 31 when the engine 115 is turned off to avoid unsafe filling of the fuel tank system, and to permit the valve 35 to open when the engine is turned on. The opening and closing means can comprise a controller 43 that receives a first signal from a key switch of the control system 121, such as an engine electronic controller unit (EECU) that indicates that the key has been turned to an ON position, and that sends a signal to the valve 35 to permit the valve to open, and that receives a different signal (e.g., no signal) when the key has been turned to an OFF position, and that sends a signal to the valve to close the valve. The opening and closing means can be arranged, after closing the valve 35 when the engine 115 is turned OFF to keep the valve 35 closed when the engine is turned back ON, at least until some other signal is provided to permit the valve to open, such as a signal that the level of fuel in the first tank 25 has fallen below the level L1.

[0032] As seen in FIG. 5, the second tank 27 can comprise a plurality of second tanks to further facilitate optimizing the packaging of the fuel tank system 21 on the vehicle. It multiple second tanks 27 and 27 (shown in phantom) and are provided, the first conduit may comprise a plurality of discrete first conduits between the top of the first tank 25 and the tops of each of the plurality of second tanks. Alternatively, as seen in FIG. 5, one first conduit 29 can be provided between the top of the first tank 25 and the top of one 27 of the plurality of second tanks, and a further conduit 29 (shown in phantom) can be provided between the top of the one of the plurality of second tanks and another one 27 of the plurality of second tanks. Similarly, at least one second conduit 31 can be provided between the first tank 25 and the bottom of at least one of a plurality of second tanks 27, i.e., the second conduit may comprise a plurality of discrete second conduits between the first tank and the bottoms of each of the second tanks or, as seen in FIG. 5, one second conduit 31 between the first tank and the bottom of one 27 of the plurality of second tanks and a further conduit 31 (shown in phantom) connecting the bottoms of the one second tank and other second tanks 27.

[0033] In the present application, the use of terms such as including is open-ended and is intended to have the same meaning as terms such as comprising and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as can or may is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

[0034] While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.