Claims:We Claim:
1. A fuel heating system (100) comprising:
-an air reservoir (102) to store air under pressure
-a vortex tube (104) connectable to said air reservoir 102 through a valve 106 to receive pressurized air; said vortex tube 104 having a cold end 108 and a hot end (110); said cold end 108 supplying cold air and said hot end (110) supplying hot air;
-a heat exchanger (112) whose first end is connected to hot end (110) of said vortex tube (104); said heat exchanger (112) being in contact with fuel in a fuel tank (116) thereby heating the fuel in the fuel tank (116)
2. A fuel heating system (100) according to claim 1, wherein said valve (106) is an electronically controlled valve
3. A fuel heating system (100) according to claim 1, wherein said valve (106) is an open-close valve
4. A fuel heating system (100) according to claim 1, wherein second end of said heat exchanger (112) is connected to an intake path (114) of an engine
5. A fuel heating system (100) according to claim 1, wherein said valve (106) is opened by an ECU (118) when said fuel is to be heated
6. A fuel heating system (100) according to claim 5, wherein said valve (106) is closed by said ECU (118) when temperature of said fuel is above a threshold
7. A fuel heating system (100) according to claim 1, wherein said cold end 108 is connectable to heat exchanger (112) after disconnecting hot end (110) from heat exchanger (112)
8. A fuel heating system (100) according to claim 1, wherein said hot end (110) and said cold end 08 may be connected to two separate heat exchangers disposed in said fuel tank.
9. A fuel heating system (100) according to claim 1, wherein said hot end (110) has a second valve to allow hot air through heat exchanger
10. A fuel heating system (100) according to claim 1, wherein said cold end (108) has a third valve to allow cold air through heat exchanger
11. A fuel heating system (100) according to claim 1, wherein said second and third valves are controlled by said ECU (118)
12. A method to heat fuel in a fuel tank (102), said method comprising the steps:
- reading the temperature of said fuel
- opening a valve (106) if temperature of said fuel is below a threshold, thereby allowing compressed air to flow into a vortex tube (104) to heat said fuel
- closing said valve (106) if the temperature of said fuel exceeds said threshold
, Description:Field of the invention
[0001] This invention relates to the field of fuel supply systems for internal combustion engines. The invention in particular is related to heating of fuel before supplying it to internal combustion engines.

Background of the invention

[0002] Heating the fuel to supply to an internal combustion for better cold start is known in prior arts. When the temperature of the fuel is low, the atomization of fuel air mixture does not happen optimally and hence the combustion may be affected. In some cases where cold temperatures are observed, the engine may not start immediately.

[0003] To over-come the problem of cold start of an engine, one solution may be to heat the fuel before supplying it to the engine. The US patent 5558069 discloses an apparatus and method for cooling or heating fluids, such as fuel in a fuel system. The apparatus in the said prior art has two heat exchangers for heating or cooling the fuel before supplying it to the engine. If the fuel is cold, then it is passed through a path where hot air exchanges heat with the fuel thereby heating the fuel. If the fuel is hot, then it is passed through another path where cold air exchanges heat with the fuel thereby cooling the fuel.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates a fuel heating system

Detailed description of the embodiments

[0006] Shown in fig. 1 is a fuel heating system 100 according to one of the embodiments of the invention. The fuel heating system 100 shown in fig. 1 comprises an air reservoir 102 to store air under pressure; a vortex tube 104 connectable to said air reservoir 102 through a valve 106 to receive pressurized air. The vortex tube 104 has a cold end 108 and a hot end 110. The cold end 108 supplies cold air and the hot end 110 supplies hot air. The hot end 110 of the vortex tube 104 is connected to a heat exchanger 112. The other end of the heat exchanger 112 may be connected to an intake path 114 which supplies air to an engine. The heat exchanger passes through the fuel in the fuel tank 116.

[0007] The invention also proposes a method to heat fuel in a fuel tank 116. The method comprising the steps: reading the temperature of the fuel; if the temperature of the fuel is below a threshold, then opening the valve 106 thereby allowing compressed air to flow into the vortex tube 104 to heat said fuel; closing the valve 106 if the temperature of the fuel exceeds said threshold.

[0008] The air reservoir 102 stores the pressurized air. The pressurized air is supplied by the engine which is not shown in fig. The air under pressure is supplied to the inlet of the vortex tube 104. The air entering the vortex tube 104 travels inside and the hot air exits through the hot end 110 and the cold air exits through the cold end 108. As the function and construction of the vortex tube 104 is well known, the same is not described in this document. The valve 106 is disposed in between the air reservoir 102 and the inlet of the vortex tube 104. The valve 106 may be an electronic proportional valve. The valve 106 is operated by an electronic control unit ECU 118. Based on the temperature of the fuel, the ECU 118 opens the valve 106. The pressurized air enters the vortex tube 104 and passes through it, gets separated as hot air and cold air and exits at the hot and cold ends respectively.

[0009] The hot end 110 of the vortex tube 104 is connected to the heat exchanger 112. In one embodiment, the heat exchanger 112 may be submerged in the fuel in the tank 116. In another embodiment the heat exchanger 112 may be wrapped around the fuel pump which is submerged in the tank 116.

[0010] The valve 106 is connected to the ECU 118. A temperature sensor 120 which may be located in a fuel path, for example in a fuel filter, is connected to the ECU 118 to provide temperature of the fuel.

[0011] The ECU 118 continuously monitors the temperature of the fuel. If the temperature of the fuel is below a pre-defined threshold, then the valve 106 is opened by the ECU 118. The valve 106 is an electronic valve which may remain fully open or fully closed depending upon the control signal provided to it controlled by the ECU 118. Opening and closing of the valve 106 may be done by making the control signal high or low respectively. Once the ECU 118 makes the control signal high, the valve 106 opens and the air from the air reservoir 102 flows into the vortex tube104. The air gets separated as hot air and cold air and exits from hot and cold end respectively. The cold end 108 is exposed to the atmosphere, hence the cold air is released into the atmosphere. The hot air passes through the heat exchanger 112 which heats the fuel in the fuel tank 116. The hot air is guided towards intake path 114 through which air is supplied to the engine for combustion. The remaining heat from the heat exchanger heats the incoming air in the intake path and assists in combustion in the engine.

[0012] When the temperature of the fuel in the fuel tank 116 reaches the pre-defined threshold or if the fuel is already above pre-defined threshold, the ECU 118 closes the valve 106. This stops the flow of air from the air reservoir 102 to the vortex tube 104 thereby stopping the hot air to the heat exchanger 112. The valve 106 may be closed by the ECU 118 by making the control signal low.

[0013] The ECU 118 may be implemented as a standalone unit. It is also possible that the existing engine control unit which is already available in vehicles may be used to operate the valve 106.

[0014] The ECU 118 may comprise a microcontroller, memory and programs to operate the valve 106. The ECU 118 will have typical input interfaces and output interfaces to operate drive circuits, actuators to control the valve 106. As these input and output interfaces are commonly known, these are not explained in this document.

[0015] The invention has the advantage that the fuel is heated without need of having heaters in the fuel tank 116. This saves energy from the battery. The heating of the fuel assists in better starting of the engine under cold conditions.

[0016] The invention has the additional advantage that the hot air passing through the heat exchanger 112 is guided to intake path 114 of the engine thereby assisting the cold start of the engine.

[0017] In another embodiment, it is also possible that the hot air may be guided towards an exhaust path of the engine to heat the catalytic converter.

[0018] The invention uses simple components to heat the fuel to assist better starting of the engine in cold conditions.

[0019] It is possible that in some countries, the ambient temperature may be always higher and the fuel may be required to be cooled for optimum performance of the engine. Under this scenario, in another embodiment, the heat exchanger may be connected to the cold end of the vortex tube and the cold air is passed through the heat exchanger thereby reducing the temperature of the fuel. Optimum performance of the engine is defined as the condition where the engine generates maximum torque for a given amount of air and fuel mixture.

[0020] In another embodiment the hot and cold ends of the vortex tube may be connected to two different heat exchangers in the fuel tank and the fuel may be selectively heated or cooled by passing hot or cold air respectively. For this purpose additional valves, referred as second valve or third valve, may be needed to selectively pass either hot or cold air through the heat exchangers.