MXPA99010379A - Liquefied petroleum gas fuel system and method - Google Patents

Abstract

A fuel supply system and method for reducing the pressure in the fuel tank for a liquefied petroleum gas fuel supply system in which fuel is returned to the tank. Return fuel is cooled by heat transfer devices in the return line in line and in the tank.

Description

CONDENSER FOR FUEL INJECTION SYSTEMS Field of Invention This invention relates to a fuel injection system for liquefied petroleum gas, and more particularly to a system and method for cooling the return fuel in such systems.

Background of the Invention The systems that supply liquefied petroleum gas ("LPG") fuel are known, for example as shown in the Requests for U.S. Patent No. 5,291,869; ,325,838; and 5,423,303. Such systems typically include a number of specialized fuel injectors that receive the fuel from the high pressure tank. A fuel line connected in line with a series of injectors is often used to deliver the fuel supply to the injectors. In many systems, the non-injected fuel is returned Ref: 032055 to the fuel tank. This is usually done to take care of the fuel supply as cold as possible, particularly where you try to inject LPG in liquid form instead of gaseous form.

One approach to injecting LPG without allowing it to vaporize is to pump high volumes of supply and return the fuel. In this way, the fuel supply spends very little time near the heat machine compartment where it is vaporized. Another approach is to employ a refrigeration cycle as described in the Patent Applications identified above. The evaporation of the returned fuel is used to cool the fuel supply, thus keeping it in liquid form.

A problem with vaporized LPG back to the fuel tank is that it can increase the tank pressure substantially over the vapor pressure of the liquid in the tank. If the steam does not condense before the tank pressure limit is exceeded, the relief valve can release LPG vapor into the atmosphere. This is both insecure and undesirable to good temper.

What is needed is a means of cooling the return fuel in the LPG systems so that the high fuel tank pressures that may occur are reduced.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a system and method of supplying LPG fuel is provided.

In one aspect of the system, the LPG system includes a plurality of fuel injectors operating connected to a fuel conduit. The fuel conduit is a communication fluid with the fuel supply and return lines. Both the fuel conduit and the injectors comprise an installation for cooling the fuel supply with the return fuel. A condenser in the return line cools the return fuel In another aspect of the invention, the LPG fuel supply system comprises a plurality of fuel injectors in fluid communication with the fuel supply and return lines. The return fuel line includes a mechanism to cool the return fuel.

In the method of the present invention, a liquefied petroleum gas fuel supply system is provided, comprising a plurality of fuel injectors in fluid communication with a fuel supply line and a return fuel line. The vaporous fuel is produced in the return fuel line by the absorption of heat. The vaporous fuel is then cooled in the return fuel line before introducing the fuel into the fuel tank.

These and other advantages and descriptions of novelty characterizing the invention are placed with particularity in the appended claims to this. However, for a better understanding of the invention and its advantages, reference is made to the drawings forming an additional part thereof, and to the additional descriptive matter in which a preferred embodiment of the invention is illustrated and described.

Brief Description of the Figures Figure 1 is a schematic diagram of a system in accordance with the present invention; Y Figure 2 is a cross-sectional view of capacitors in accordance with the present invention.

Detailed Description of the Preferred Modalities.

Referring now to the drawings, where similar numeration designates similar parts of the total of the figures, a fuel supply system 10 is shown to provide LPG to an internal combustion engine 12. US Patent Applications Nos. 5,291,869 ("869 patent"). "LIQUEFIED PETROLEUM GAS FUEL SUPPLY SYSTEM PETROLEUM GAS FUEL SUPPLY SYSTEM", 5,325,838 ("patent 838") "PETROLEUM GAS FUEL INJECTOR" LIQUEFIED FUEL INJECTOR, and 5,423,303 ( "patent 303"), "FUEL DUCT FOR INTERNAL COMBUSTION MACHINES" ("FUEL RAIL FOR INTERNAL COMBUSTION ENGINE") are also incorporated for reference and may be referred to as appropriate for this purpose.

The system 10 includes a fuel conduit 14 that delivers fuel to a plurality of fuel injectors 16. Although a fuel conduit is shown in the preferred embodiment, one is not necessary within the principles of the invention. For example, the branched separate supply lines of a main supply line may deliver the fuel for the injector to seal in parallel.

In the preferred embodiment, both the fuel conduit 14 and the injector 16 include facilities for cooling the supply of fuel with return fuel, such as those described in the "* 869 patent generally, and more specifically in the '303 patent for the fuel pipeline and the? 838 patent for the fuel injector.These installations involve the evaporation of the return fuel in close proximity to the fuel supply to extract heat from the fuel supply.Thus, the LPG supply is maintained in the liquid form to be injected then It is not necessary, however, for the fuel conduit or the injectors having these a refrigeration cycle, as well as other means in which the liquid LPG for injection can be executed.

The main problem of the present invention is directed to the high tank pressures that result when the hot LPG is returned to the fuel tank 18. Under the present regulations in the United States, the maximum allowed tank pressure is 312 psi. A pressure release valve (not shown) may open this maximum pressure if it is reached.

The return fuel is heated in this passage through the machine compartment by the machine itself. It can also be heated if a cooling cycle such as that in the preferred embodiment is employed. If the return line is a route under the frame, machine, transmission, exhaust pipe or radiator, you can also tend to absorb the heat from them. The problem is more pronounced at high ambient and machine temperatures and at low fuel levels.

With reference to Figures 1 and 2, a system and method for addressing this problem will be described. In addition to the fuel injectors 16 and the fuel conduit 14 described above, the system 10 includes a fuel pump 20, a supply line 22 and a return line 24. As is generally the case, a control unit machine 26 control injectors 16.

The return fuel is cooled in the preferred mode by line capacitors 28 and tank 30 on return line 24. As shown in Figure 2, capacitors 28, 30 have external 32 and internal 24 fins to assist the heat transfer. These are made of extruded aluminum.

It is preferable to locate them, to the capacitor line 28, and much more possibly to the return line 24, away from the heat under the frame. The cooling air can then assist in the removal of heat from the return fuel in the condenser 28. If necessary, through the pipeline or other means, the air can be forced to cross the outer fins 32 to further increase the cooling. It is also necessary to thermally insulate the return line 24, such as by surrounding it with rubber foam.

The on-line capacitor 30 is immersed in the fuel tank 18 to a terminal end of the return line 24. The condenser 30 is placed below the fuel level in the tank so that the heat can be transferred to the liquid fuel. It is preferred to mount at the bottom of tank 18 to maximize exposure. The condenser 30 is raised by the legs 36 to this distal end 38 and has a plurality of ventilation holes 40 for the return fuel to enter the fuel in the tank 18. By this installation, the gaseous fuel tends to cool the full length of the condenser 30 before exiting the near distal end 38. Covering the ventilation holes through the tank 18 reduces the location of the heat that may otherwise occur. Ventilation holes 40 are also preferably small, on the order of 0.000762 to 0.002032 centimeters in diameter (.03-.08 inches in diameter), preferably 0.001524 centimeters (.06 inches), to create small bubbles that condense rapidly. The total flow area through the vent holes 40 is preferably twice the cross sectional area of the return line 24 to minimize the back pressure. Although the vent holes 40 are shown approximately in a horizontal quadrant of the condenser 30, it may be preferred that it be in the low position to improve the flow.

The principle of cooling with a liquid can also be applied, for example, by cooling in line with water or other liquid that is not combustible.

Where both line 28 and tank 30 capacitors are used as described herein, a cooling of the order of 200-500 watts or greater is obtained. It depends on whether one or both may need dependents in the cooling needs of the particular system. The type and number of heat transfer devices and their size, shape and installation may also vary within the principles of the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers.

Having described the invention as above, the content of the following is claimed as property.

Claims (19)

t what. Claims

1. A fuel supply system for providing liquefied petroleum gas to an internal combustion engine, characterized in that it comprises: (a) a plurality of fuel injectors in fluid communication with a fuel supply line communicating with a fuel tank tibie ( b) a fuel return line; and (c) a condenser in fluid communication with the fuel return line, placed in the fuel tank, and comprising: (i) an elongated body having a passage therethrough to return the fuel back to the tank made out of fuel; and (ii) a plurality of ventilation holes spaced along the length of the body and communicating with the passageway; (iii) the ventilation holes being inclined relative to the horizontal of the length such that the gaseous fuel may first tend to exit into the ventilation holes close to the distal end of the passage.

2. The supply system according to claim 1, characterized in that the condenser has external fins to transfer the heat of the return fuel.

3. The fuel supply system according to claim 1, characterized in that it has external fins to transfer the heat of the return fuel.

4. The fuel supply system according to claim 1, characterized in that the condenser is mounted close to the bottom of the fuel tank.

5. The fuel supply system in accordance with rei indication 1, characterized in that the passage is a straight passage starting at the proximal end of the body and ending at the distal end.

6. The fuel supply system of. according to claim 5, characterized in that the distal end of the body is raised relatively to the proximal end, thereby tilting the ventilation holes.

7. The fuel supply system according to claim 1, characterized in that the ventilation holes have a relative height constant to the body and passage.

8. The fuel supply system according to claim 1, characterized in that the ventilation holes are around between 0.000762 and 0.002032 centimeters in diameter (0.030 and 0.080 inches in diameter).

9. The fuel supply system according to claim 1, characterized in that the total area of the ventilation holes is greater than two times the cross-sectional area of the fuel return line.

10. The fuel supply system according to claim 1, characterized in that the ventilation holes are arranged on opposite sides of the body close to the average height of the passage.

11. An apparatus for condensing the return fuel in a fuel tank, characterized in that it comprises: (a) an elongated body having a passage therebetween in fluid communication with the return fuel line; and (b) a plurality of ventilation holes positioned along the length of the body and in communication with the passageway; (c) the passage and the ventilation openings being constructed and arranged in such a way that the gaseous fuel tends to come out of the ventilation holes close to the disteal end of the passage j e first.

12. The apparatus according to claim 11, characterized in that it also includes external fins longitudinally extended along the body, arranged relatively to the ventilation holes in such a way that the gaseous fuel bubbles out of the ventilation holes traveling along the fins before rising upwards in the tank.

13. The apparatus according to claim 11, characterized in that it also includes internal fins radially extended in the passage of the body.

14. The apparatus according to claim 11, characterized in that the passage is a straight passage starting at the proximal end of the body and ending at the distal end.

15. The apparatus according to claim 14, characterized in that the distal end of the body rises relatively to the proximal end, thereby tilting the ventilation holes.

16. The apparatus according to claim 11, characterized in that the ventilation holes are at a relative height constant to the body and passage.

17. The apparatus according to claim 11, characterized in that the ventilation holes are around between 0.000762 and 0.002032 centimeters in diameter (0.030 and 0.080 inches in diameter).

18. The apparatus according to claim 11, characterized in that the total area of the ventilation holes is greater than twice the cross-sectional area of the fuel return line.

19. The fuel supply system according to claim 1, characterized in that the ventilation holes are arranged on opposite sides of the body close to the average height of the passage.