Abstract:
A vehicle fuel delivery system for liquid fueled vehicles including a vehicle housing a pressure vessel for receiving, discharging and containing fuel. The vehicle fuel delivery system includes fuel lines for communicating fuel to the pressure vessel, and fuel lines for communicating fuel from the pressure vessel to a fuel delivery device. The vehicle fuel delivery system always maintaining positive fuel pressure throughout the delivery system.

Description:
[0001]    This application claims priority from U.S. provisional 61/515,037 filed on Aug. 4, 2011 under the title FUEL DELIVERY SYSTEM AND METHOD by Stephen John Fenton. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present device relates to fueling systems, devices and methods and in particular relates to fueling systems for engine powered vehicles including aircraft, land vehicles and marine operated power craft. 
       BACKGROUND OF THE INVENTION 
       [0003]    Vapor lock is an unacceptable condition which can occur in liquid fuel powered engines. Most liquid fuels must be converted to a gas with vapor-like qualities within an engine&#39;s combustion cylinder in order to enable a planned, timed, burning of the fuel. It is possible under certain conditions, that the fuel transformation from liquid to gas vapor can occur before it is intended, causing technical problems to occur with the entire fuel transfer and propulsion system. This can be a problem for any liquid fueled combustion engine but is particularly a problem in aircraft which are exposed to very high G forces, large temperature variations, and large altitude variations, such as in unmanned aerial vehicles or UAV&#39;s. Therefore this specification will use a UAV as the example vehicle throughout since the technical problem can be very severe in this type of vehicle. 
         [0004]    Most UAV systems are designed to transfer liquid gas, not vapor. The conversion of fuel from liquid to gas vapor must occur when required but not before. During fuel transfer processes from bulk ground storage through to the combustion chamber inlet in the engine, liquid fuel is susceptible to vapor formation. Once vapor is formed in a liquid fuel during transfer within a propulsion system, there is a danger that the volume of vapor will cause the carburetor or fuel injection pump to fail due to vapor lock which can ultimately cause the engine to malfunction. Unintended vapor formation can also cause other fuel system components and elements to fail with similar net result. When the volume of vapor reaches levels the propulsion system cannot manage, the vapor must be contained, broken down, eliminated or expelled before the fuel presents to the running engine. If enough quantity of unwanted vapor is in the fuel system during a UAV mission, it can result in catastrophic engine failure. This is due to vapor lock which could occur at various points in the fuel system with fuel injection or carburetion engine feed. 
         [0005]    In addition to the original vapor problem, vapor will tend to collect at the highest point within a closed circuit fuel container system. When, for example, 1 mm to 3 mm diameter vapor bubbles are able to naturally gather, they can present to the engine in a larger bubble than the system can digest. Different liquid fuel compositions can reduce inappropriate vapor creation, however vapor occurs with common fuels as required temperature ranges and altitude limits increase. 
         [0006]    UAV Fuel Tank System Options 
         [0007]    The two most common fuel storage options for the UAV&#39;s include wet tanks and bladder systems. Both approaches are currently being used in the industry and have benefits and disadvantages. 
         [0008]    Wet Tank Advantages Over the Closed Bladder System
       1. Wet tank based fuel systems enable the operator to fuel by simple pouring methods.   2. Wet tank based fuel systems have inherent vapor elimination at least in the fuel storage area of the system. Any vapor in the fuel storage on the vehicle will rise to the top of the liquid and disappear.       
 
         [0011]    Closed Loop Bladder Tank Advantages Over the Wet Tank System
       1. Bladder tanks limit the sloshing of fuel that occurs in the wet tank system.   2. Bladder tanks enable the fuel to present to the engine regardless of attitude without the need for any sophisticated pickup systems required in the wet tank.   3. Bladders limit the possibilities of a spark causing an explosion as the ambient air does not mix with the fuel as it does in a wet tank.   4. As the bladders do not have air with the fuel, they do not require the expense of wicking anti-explosion fibrous foam.   5. Bladders can enable longer flights when the fuel level is low without as much chance of engine starvation.       
 
         [0017]    To the inventor&#39;s knowledge, all UAV&#39;s using liquid fuels include at least one fuel pump with an inlet that “pulls” and an outlet that “pushes” somewhere on the air vehicle and/or on the ground station. Most liquid fueled vehicles include a “push-pull” fuel pump somewhere. 
         [0018]    We performed extensive experimental development and in-house testing with Mogas and Avgas in fuel-recommended temperatures. We learned that vapor was being created, or was always in danger of being created whenever a negative pressure was acting on the fuel during any transfer process. This issue became more troublesome with even minor differences in transfer altitude of the fuel supply, pump and fuel tank or bladder. During fueling processes to de-fuel and fuel a miniature UAV, the vehicle, bladder, pump and supply all needed to be in a pre-specified plane. If the fuel source was below the pump by two or three feet, more negative pressure was required of the pump to get the fuel transferred. This process would cause increasing likelihood of vapor formation. There may be some systems which include portions of the concept of pushing fuel or putting positive pressure to act on a bladder, but always have a fuel pump somewhere that not only pushes, but also pulls fuel to move it in some point of the design. 
         [0019]    Wet tanks and bladder-style fuel tanks are the two main options for UAV&#39;s today. Bladders have some technical advantage for use on UAV&#39;s as they enable better unhampered fuel flow to the engine regardless of the aircraft attitude. Bladder systems also enable the engine to run closer to empty that one would risk with a wet tank. Wet tanks also allow sloshing of the fuel that can cause foaming and bubbles to occur. The wet tanks have the chronic issue of danger from explosion due to a spark. There are requirements to use a fibrous anti-spark sponge-like material included in wet tanks to limit the explosion potential. Bladders have issues with flow capabilities when a standard push-pull fuel pump is used to get at the fuel and present it to the engine and to evacuate the fuel bladder after a mission. 
         [0020]    The usual configuration of a bladder system in the UAV industry is to pull the fuel with the pump from the fuel bladder and then push it to the engine. Placing the push-pull pump closer to and preferably in the bladder with the fuel, will decrease vapor creation. However, that same bladder located pump would be susceptible to vapor creation if it was also used to fill the same bladder. 
         [0021]    Fuel bladder manufacturers have been working on flow assisting internal piccolo tubes, wire wraps, mesh and other methods to ensure the fuel flow continues as the bladders are collapsing during the engine run-cycle. However, these flow assisting designs are costly, add weight, bulk and require an increased volume of fuel that must be in the bladder but will never be used to fuel the engine. The volume inside a flow assisting piccolo tube for example will hold fuel that cannot get to the engine. This is dead weight that must be flown on every mission. The best option for fuel-flow assisting bladder design is to simply to use an embossed bladder material. With embossed bladder film, no other flow assisting designs are required as the flow is inherent to the embossed film. However, as each bladder system (regardless of flow enhancing design) gets low with fuel, there is a danger of fuel starvation (reduced flow) and ever increasing in vapor creation. Various altitudes and temperature ranges all acting on the fuel bladder steadily increase vapor formation issues and can become unmanageable. 
       SUMMARY OF THE INVENTION 
       [0022]      1 . A vehicle fuel delivery system for liquid fueled vehicles comprising:
       a) a vehicle housing a pressure vessel for receiving, discharging and containing fuel;   b) a refueling means for pushing fuel under pressure to the pressure vessel for refueling the pressure vessel;   c) a pressure means for pushing fuel under pressure from the pressure vessel to a fuel delivery device for subsequent burning of the fuel;   d) wherein the vehicle fuel delivery system always maintains a positive fuel pressure throughout the delivery system.         
         [0027]    Preferably wherein the pressure means includes a vehicle housed gas compressor for pushing fuel from the pressure vessel to the fuel delivery device under a head of gaseous pressure. 
         [0028]    Preferably wherein the gas being air. 
         [0029]    Preferably wherein the refueling means for pushing fuel under pressure to the pressure vessel for refueling the pressure vessel and for receiving fuel from the pressure vessel under pressure during defueling. 
         [0030]    Preferably wherein the refueling means further includes a fueling station external to the vehicle for selectively pushing fuel into the pressure vessel under a head of gaseous pressure. 
         [0031]    Preferably wherein the fueling station for selectively pushing fuel into the pressure vessel or for receiving fuel from the pressure vessel for defueling the pressure vessel. 
         [0032]    Preferably wherein the pressure means for pushing fuel under pressure from the pressure vessel to a fuel delivery device for subsequent burning of the fuel, and for pushing fuel under pressure to the refueling means. 
         [0033]    Preferably wherein the pressure means includes control valves for selectively pushing fuel to a fuel delivery device or to push fuel to a fueling station to defuel the pressure vessel under a head of gaseous pressure thereby always maintaining positive fuel pressure. 
         [0034]    Preferably wherein the pressure means includes a vehicle housed gas compressor for selectively pushing fuel from the pressure vessel to the fuel delivery device under a head of gaseous pressure or to the fueling station under a head of gaseous pressure for defueling the pressure vessel. 
         [0035]    Preferably wherein the fueling station further includes a control module and a tank assembly, the tank assembly housing fuel under a head of gaseous pressure, the fueling station for selectively pushing fuel into the pressure vessel to refuel the pressure vessel or to receive fuel from the pressure vessel into the tank assembly during defueling. 
         [0036]    Preferably wherein the pressure vessel includes a bladder for containing the fuel, wherein the bladder expands and contracts as fuel is received and discharged. 
         [0037]    Preferably wherein the pressure vessel includes a gas reservoir wherein the gas in the reservoir is pressurized to force fuel under a head of gaseous pressure out of the bladder. 
         [0038]    Preferably wherein the pressure vessel includes an air port in communication with the gas reservoir for receiving and discharging gas there through. 
         [0039]    Preferably wherein the pressure vessel includes a fuel port in communication with the bladder for receiving and discharging fuel there through. 
         [0040]    Preferably wherein the pressure vessel includes a bladder pressure vessel for receiving, discharging and containing fuel. 
         [0041]    Preferably wherein the pressure vessel includes a hyper G pressure vessel for receiving, discharging and containing fuel. 
         [0042]    Preferably wherein the vehicle is an aircraft. 
         [0043]    Preferably wherein the vehicle is an unmanned aerial vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]    With the intention of providing demonstration of the characteristics of the device or method, an example is given below, without any restrictive character whatsoever, with reference to the corresponding figures, of a preferred embodiment of the device and method as follows; 
           [0045]      FIG. 1  schematically represents a fuel delivery system in accordance with the present concept. 
           [0046]      FIG. 2  schematically represents fueling a plane using a fueling station in accordance with the present concept. 
           [0047]      FIG. 3  schematically represents defueling an aircraft using a fueling station in accordance with the present concept. 
           [0048]      FIG. 4  schematically depicts tank assemble pressurization during vehicle fueling. 
           [0049]      FIG. 5  schematically depicts tank assembly venting for vehicle defueling. 
           [0050]      FIG. 6  schematically depicts venting of the vehicle pressure vessel during vehicle fueling. 
           [0051]      FIG. 7  schematically depicts pressure vessel pressurization during vehicle defueling. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0052]    The present concept a fuel delivery system shown generally as  100  is shown in  FIG. 1 . 
         [0053]    Fuel delivery system  100  includes the following major components namely vehicle fuel delivery system  202  and fueling station  104 . 
         [0054]    Referring first of all to fueling station  104  it includes the following major components namely tank assembly  106  which is connected to a control module  108 . 
         [0055]    Tank assembly  106  includes a pickup tube  114  for delivery of fuel  110  and also a level sensor  112  for measuring the level of fuel  110  within tank assembly  106 . 
         [0056]    Control module  108  is connected to tank assembly  106  with a number of air lines  107  and electrical lines  109 . 
         [0057]    The interior of control module  108  not shown includes a number of components including compressors, pressure sensors, differential pressure sensors, solenoid valves, pilot valves, manifold for distributing air and directional control valves. 
         [0058]    The fueling station  104  is connected to the vehicle fuel delivery system  202  via a first quick connect  116  and a second quick connect  118 . 
         [0059]    First quick connect  116  communicates to vehicle fuel delivery system with a refueling fuel line  262 . 
         [0060]    Second quick connect  118  communicates to vehicle fuel delivery system  202  through a refueling air line  264 . 
         [0061]    Referring now to the vehicle fuel delivery system shown generally as  202  includes vehicle pressure vessel which may be of the type shown as hyper G pressure vessel  204  or bladder pressure vessel  206  or wet tank vessel  208 . The present fuel delivery system  100  can be adapted to work with any one of the above three mentioned fuel pressure vessels. 
         [0062]    A vehicle such as an UAV will include on board an air compressor  260 , a check valve  266 , a pressurized air line  268 , a fuel delivery line  270 , a fuel delivery device  272  and eventually fuel for combustion  274 . 
         [0063]    By way of example only fuel delivery device  272  could be a fuel injection pump or a carburetor. 
         [0064]    Fuel for combustion  274  could be for example avgas or mogas, or diesel or JP8 fuels which are mixed with air and ready for combustion. 
         [0065]    The reader will note that vapour is undesirable until such time as the fuel is delivered by the fuel delivery device  272  and converts it into a fuel/air mixture ready for combustion  274 . Fuel for combustion  274  is normally in the form of a very fine mist or vapour, mixed with an oxidizer such as air. 
         [0066]    Referring now back to the vehicle pressure vessels which could either be a hyper G pressure vessel  204  and/or a bladder pressure vessel  206  and/or a wet tank vessel  208 . 
         [0067]    In the case that the vehicle includes a hyper G pressure vessel  204  this vessel has a fuel port  212  located on the upper portion, an air port  214  and gas reservoir  215  located on the lower portion a gas reservoir  215 , a linear piston  216  travelling within the pressure vessel  204 , a bladder  218  for containing the fuel  210  and a vapour collection area  220  near the top of fuel port  212 . 
         [0068]    The reader will note that using the hyper G pressure vessel  204  any vapour which does form during any of the fueling and/or defueling operations will be collected in the vapor collection area  220  and will be quickly eliminated from the system at the very beginning or start up of the engine of the vehicle. 
         [0069]    UAV&#39;s typically now have a bladder pressure vessel as depicted as  206  which includes fuel port  232  in communication with the interior of the fuel bladder  236  and air port  234  in communication with the space being a gas reservoir  217  between the hard or soft pressure vessel  238  and the fuel bladder  236  and a vapour collection area  240  near fuel port  232 . Fuel bladder  236  houses fuel  210  squeezed or compressed by the air pressure between the hard or soft pressure vessel  238  and the bladder  236 . 
         [0070]    Most land based vehicles use a wet tank vessel  208  which includes a fuel port  250  an air port  252  wherein the wet tank vessel  208  houses fuel  210 . This type of tank arrangement is normally unpressurized. 
         [0071]    Referring now to  FIG. 2  which schematically depicts the fuel flow between the fueling station  104  and aircraft schematically depicted as  301 . 
         [0072]    Referring now to  FIG. 2  which is showing pressurized vehicle fueling wherein fuel  110  communicates under pressure through refueling line  262  to aircraft  301  and air flows through refueling air line  264  into control module  108  for venting or for further distribution under pressure through tank assembly air pressure line  304  for pressurizing of fuel  110  within tank assembly  106 . 
         [0073]    Referring now to  FIG. 3  which schematically depicts defueling of an aircraft  301  using fueling station  104  wherein control module  108  produces air pressure which is communicated along refueling air lines  264  into the vehicle pressure vessel and forcibly pushes fuel  110  through refueling fuel line  262  back into tank assembly  106  wherein control module  108  provides for venting of air in tank assembly  106  through tank assembly air vent  312 . 
         [0074]    Referring now to  FIG. 4  which schematically depict pressurization of the tank assembly for vehicle fueling which includes tank assembly compressor  300 , check valve  302  communicating pressurized air through pressurized line  304  through first directional control valve  306  for pressurizing the tank assembly via tank assembly air  308 . In addition a second directional control valve  314  ensures that air is vented to atmosphere via vent line  312  and tank assembly vent  310 . 
         [0075]    Referring now to  FIG. 5  which schematically depicts a vented tank assembly for vehicle defueling in which a tank assemble compressor  300  includes a check valve  302  and a pressurized line  304  which vents to atmosphere. Tank assembly  106  in vented also to atmosphere via vent line  312  and tank assembly vent  312 . 
         [0076]      FIG. 6  schematically depicts what occurs within the vehicle pressure vessel  205  during fueling. 
         [0077]    In  FIG. 6  for example pressurized air line  268  is routed for venting through third directional control valve  410  and fourth directional control valve  412 . 
         [0078]      FIG. 7  schematically depicts the vehicle pressure vessel during defueling in which vehicle on-board compressor  260  supplies air under pressure to pressurized air line  268  thereby providing air pressure to vehicle pressure vessel  205  at air port  214 . 
         [0079]    The reader will note that by simply always pushing and never pulling fuel when moving it in any direction throughout the vehicle one can minimize the natural vapour creation factors in current designs. This approach is simple, less expensive in both overall design and unlocks several key advantages. 
         [0080]    Benefits of using the current fuel delivery system  100  which includes either a bladder pressure vessel  206  or a hyper G pressure vessel  204  are as follows. 
         [0081]    Firstly vehicle fuel delivery system  202  together with fueling station  104  which provides for fuel delivery system  100  eliminates the effects of altitude changes from acting directly against the fuel within the bladder. As a UAV flies higher altitude changes alone can cause the fuel in an unpressurized bladder to boil. This vapour is created without the need for any negative pressure pump forces assisting. The current system including a pressurized bladder and/or hyper G pressure vessel enables the UAV to fly higher and continue to run without vapour lock engine failure. 
         [0082]    Secondly flow assisting enhancements are not required within the pressurized bladder. This saves mass weight and manufacturing expense enabling a much simpler bladder layout. 
         [0083]    Thirdly the use of the fuel delivery system  100  allows for increased amount of fuel that can be on board due to savings in weight in other areas. 
         [0084]    In addition a simple less expensive oversized bladder design is always under positive pressure which is not possible with a standard push/pull type of pump system. Additionally the entire fuel load is able to be used during flight and drop off of fuel to the engine will not occur until the very last drop of fuel is fed to the engine and is always sent with the same flow rate throughout. 
         [0085]    There are other more subtle advantages to the present fuel delivery system  100  including that any vapour that is in the system would be supplied to the fuel injection or the carburetor with pressure behind it which would eliminate vapour lock as the fuel and vapour is pushed throughout the system. Any vapour take-up equipment currently required for all fuel transfer is almost entirely eliminated. Vapour is constantly and automatically being eliminated each time fuel transfers in any direction using this system. This is due to the fact that as fuel is transferred all bubbles naturally rise to the top, and are pushed out. 
         [0086]    The current system also eliminates ground station fuel transfer pumping failure at extremely high or extremely low temperatures due to cavitation and/or fuel compatibility issues. 
         [0087]    Fuel delivery system  100  also allows one to more quickly fuel and defuel without negative consequences. Standard current bladder system design include evacuation that requires the operator to pull the fuel out of a bladder after flight. 
         [0088]    This process itself causes vapour to form especially when the fuel is almost fully evacuated. The amount of vapour created will change with altitude and temperature. The main reason for defueling after mission in the current system is to get any air or vapour bubbles out for the next fuel fill cycle. Unfortunately the evacuation process itself creates vapour since once the bladder is almost empty with a negative pressure pump pulling the fuel out, vapour is created more quickly than at any other stage. This vapour almost inevitably cannot be completely eliminated and becomes the first thing to go into the vehicle during the refueling process. 
         [0089]    Finally it is easier and technically simpler to compress air to engage a mechanical spring or other mechanical device to in turn actuate a bladder and thereby move the fuel, than it is to pump fuel directly. Fuel delivery system  100  doesn&#39;t directly move fuel but creates and uses compressed air or simply releases a mechanical load to act on the fuel charge. This eliminates the need to handle the chemical effects of fuel at temperature and/or altitude. 
         [0090]    In addition to these benefits the hyper G pressure vessel  204  also includes further benefits that are currently not available for bladder pressure vessel  206 . 
         [0091]    For example hyper G pressure vessel  204  will eliminate sloshing and balance shifting of fuel regardless of the G&#39;s during launch or flight and regardless of the amount of fuel in the tank at any time. 
         [0092]    Secondly constant fuel feed rate is possible from the full fuel load condition to the last drop in the tank. 
         [0093]    Thirdly there is naturally vapour elimination in mitigation through the design of the hyper G pressure vessel  204  which potentially can be used on a stand-alone basis without the fueling station  104  and on any other type of powered vehicle in the air, on the land or in the sea. 
         [0094]    It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.