Arrangement with a fuel tank having at least two compartments

Abstract

Arrangement (1) in a motor vehicle with a fuel tank (2) for storing at least two different types of fuel, wherein the tank (2) is divided into at least a first compartment (3) and a second compartment (4) each with variable volume, the first compartment (3) being assigned to a first type of fuel and the second compartment (4) being assigned to a second type of fuel, and the two compartments (3, 4) being separated from each other by a membrane (5), wherein the position of the membrane (5) within the tank (2) can be changed, further comprising a gas switching valve (11), a pressure relief valve (14), at least one pressure sensor (12) and an internal combustion engine (10) with at least one cylinder (21), each having an injector for liquid or gaseous fuel.

Description

[0001] The invention relates to an arrangement with a fuel tank having at least two compartments for storing at least two different types of fuel in a motor vehicle, as well as a method for operating an internal combustion engine.

[0002] A number of fuels are known for operating internal combustion engines. Liquefied petroleum gas (LPG) is frequently used in modern internal combustion engines because, among other things, it is inexpensive relative to its volume, its combustion produces low emissions, and its combustion noise level is relatively low.

[0003] Document DE 31 47 792 A1 describes a fuel tank for storing two different fuel types, in which a first compartment stores gas and a second compartment stores gasoline, and the compartments are separated from each other by a position-adjustable membrane. Document DE 37 14 401 A1 describes membrane containers for mineral oil products made of a film material.

[0004] However, injecting LPG into the combustion chamber of an internal combustion engine cylinder requires high pressure. Traditionally, high-pressure pumps located between the tank and the internal combustion engine are used to generate the necessary pressure. However, these pumps are expensive, energy-intensive to operate, and require space. Therefore, the challenge is to supply LPG to an internal combustion engine in a manner that is more advantageous than the state of the art.

[0005] This object is achieved by an arrangement with a fuel tank having the features according to claim 1. Further advantageous embodiments and refinements of the invention emerge from the auxiliary and dependent claims, the figures and the exemplary embodiments.

[0006] A first aspect of the invention relates to an arrangement in a motor vehicle having a fuel tank for storing at least two different types of fuel, wherein the tank is divided into at least a first compartment and a second compartment, each with a variable volume, the first compartment being assigned to a first type of fuel and the second compartment to a second type of fuel, and the two compartments being separated from one another by a membrane, wherein the position of the membrane within the tank can be changed.

[0007] The fuel tank is advantageous because the second fuel can be charged with a high pressure, which can exert a corresponding pressure on the first fuel through the membrane.

[0008] The membrane consists of a suitable material with a layer thickness that allows for flexible behavior depending on the pressure exerted on the membrane. Preferably, the membrane in the tank is a flexible film. With regard to the properties of the membrane or film, "flexible" means that its shape can be changed, so that, for example, volume changes in the first compartment cause pressure on the other side, and vice versa. Thus, in addition to changing the position of the membrane, changing the shape of the membrane can contribute to exerting pressure.

[0009] Furthermore, the first compartment is preferably intended for a liquid fuel, and the second compartment is preferably intended for a gaseous fuel. Gaseous fuel can advantageously be subjected to a pressure higher than the ambient pressure, whereupon it can exert a corresponding pressure on the second fuel via the flexible film. Particularly preferably, liquefied petroleum gas (LPG) is provided as the first fuel, and compressed natural gas (CNG) is provided as the second fuel.

[0010] The second compartment of the tank can be filled at a pressure of up to 200 bar. The second compartment can also be filled at a lower or higher pressure.

[0011] The arrangement further comprises a gas switching valve, a pressure limiting valve, at least one pressure sensor and an internal combustion engine with at least one cylinder, each of which has an injector for liquid or gaseous fuel.

[0012] A second aspect of the invention relates to a method for operating an internal combustion engine with a fuel from a tank in an arrangement according to the invention, comprising the steps: - Adjusting the membrane separating the first compartment from the second compartment by means of the coil so that the membrane is moved towards the second compartment, - Filling the first compartment of the tank with a liquid fuel at ambient pressure, - Filling the second compartment of the tank with a gaseous fuel until the pressure in the first compartment is at least 150 bar, - introducing the liquid fuel to an injection device of a cylinder under the pressure exerted by the gaseous fuel in the second compartment on the liquid fuel in the first compartment.

[0013] The advantages of the method according to the invention correspond to the advantages of the arrangement according to the invention.

[0014] Preferably, the pressure on the liquid fuel in the second compartment is set to up to 200 bar.

[0015] Furthermore, it is preferred if the pressure on the liquid fuel depends on the volume ratio of the first compartment to the second compartment.

[0016] Furthermore, it is preferred if the internal combustion engine is operated with the gaseous fuel when the liquid fuel in the first compartment has been consumed.

[0017] The invention is explained in more detail with reference to the figures. They show: Fig. 1 a schematic arrangement with an embodiment of the arrangement according to the invention. Fig. 2 a flowchart of an embodiment of the method according to the invention.

[0018] In Fig. 1 shows an arrangement 1 with a fuel tank 2. The tank 2 has a cuboid shape and is defined by the outer walls. The shape of the tank 2 can also be designed differently, for example, depending on the respective vehicle. The tank 2 is made of a material conventionally used by those skilled in the art for tanks, e.g., a metal. The tank 2 has a first compartment 3 and a second compartment 4. The two compartments 3, 4 are separated from each other by a membrane 5, e.g., a flexible film 5.

[0019] The membrane 5 can be made of any suitable material, e.g., a polymer. The membrane 5 can also comprise different materials. It is essential that the film is impermeable to gaseous and liquid fuels stored in the compartments 3, 4. The membrane 5 comprises a material layer with a thickness that allows for the desired flexibility. The shape of the membrane 5 is shown in the illustration of Fig. 1 is bent slightly upwards, in the direction of the first compartment 3, but it can also be bent in the direction of the second compartment 4, or more or less perpendicular to the outer walls of the tank 2. Furthermore, the membrane 5 can be changed in its shape by appropriate pressure due to its flexibility.

[0020] The position of the membrane 5 within the tank can also be changed. For this purpose, the membrane 5 is mechanically connected to a coil 6. The coil 6 is, for example, an actuator designed to move the membrane 5 into different positions. Certain steps can also be preset to which the membrane 5 is adjusted.

[0021] The first compartment 3 of tank 2 is intended for a gaseous fuel, particularly natural gas (CNG). The second compartment 4 of tank 2 is intended for a liquid fuel, particularly liquefied petroleum gas (LPG). For this purpose, compartments 3 and 4 are each connected by lines (not shown) through which the fuels are filled into the corresponding compartments.

[0022] In the arrangement 1, a first line 7 leads from the first compartment 3 to an internal combustion engine 10. A second line 8 leads from the second compartment 4 to the internal combustion engine 10. Both lines 7, 8 open via a gas switching valve 11 into a common third line 9, through which the respective fuel is forwarded to the internal combustion engine 10. The gas switching valve 11 has two switching positions, wherein in the Fig. In the switching position shown in Figure 1, the first line 7 is open and the second line 8 is closed, so that LPG is supplied to the internal combustion engine 10. In the other possible switching position, the second line 8 is opened, while the first line 7 is closed, so that CNG is supplied to the internal combustion engine 10.

[0023] Pressure sensors 12 and temperature sensors 13 are arranged in the first line 7, the second line 8, and the third line 9. More sensors than those shown can also be present at various positions in the lines. A pressure relief valve 14 is arranged in the second line 8 to regulate the pressure. The pressure relief valve 14 is designed to limit the pressure of the CNG, which is in the range of 20-200 bar when the CNG flows from the second compartment 4 into the second line 8, to approximately 16 bar.

[0024] Furthermore, the first line 7 and the second line 8 are connected to each other via a fourth line 15, in which a spring-loaded check valve 16 is located. The fourth line 15 is only used when the LPG reaches a pressure equivalent to that of the CNG during operation. During the subsequent switchover from LPG to CNG, the fourth line 15 ensures that a mixture of LPG and CNG can flow into the cylinders.

[0025] In the illustrated arrangement, the internal combustion engine 10 has four cylinders 21 arranged in series. A different number of cylinders 21 may also be present, and / or the cylinders 21 may also be arranged in a different manner. The cylinders 21 each have LPG injectors 22 designed to inject liquid fuel, and CNG injectors 23 designed to inject gaseous fuel.

[0026] In a method for operating the internal combustion engine 10 as shown in Fig.2, LPG is preferably used as fuel, and CNG as the means to generate the necessary pressure with which LPG is injected into the cylinders 21. In a first step S1, the diaphragm 5 is adjusted by the coil 6 in the direction of the second compartment 4. In a second step S2, the first compartment 3 of the tank 2 is filled with LPG at ambient pressure via a line (not shown). The possible filling quantity is determined by the position of the diaphragm 5, which determines the volumes of the compartments 3, 4. In a third step S3, CNG is filled into the second compartment 4 via a line (likewise not shown), the CNG being filled under pressure. CNG is filled in such a quantity until the pressure in the second compartment 4 is at least 150 bar. Preferably, the pressure in the second compartment 4 can be increased to up to 200 bar.In a fourth step S4, the LPG is supplied to each injection device 22 of the cylinders 21 under the pressure exerted by the CNG in the second compartment 4 on the LPG in the first compartment 3.

[0027] The pressure exerted by the gaseous fuel on the liquid fuel changes depending on the volumes of the compartments 3, 4. The more LPG is discharged from the first compartment 3, the smaller its volume becomes. At the same time, the volume of the second compartment 4 increases because the CNG expands, reducing the pressure of the CNG. However, the pressure remains high enough that LPG is discharged from the tank 2 at a sufficiently high pressure until the LPG is used up. When there is no more LPG, the gas switching valve 11 is switched so that the second line 8 is opened and CNG is directed to the cylinders 21, where it is injected into the cylinders by the CNG injectors 23. List of reference symbols 1 arrangement 2 tanks 3 first compartment 4 second compartment 5 Membran 6 coil 7 first line 8 second line 9 third line 10 internal combustion engine 11 Gas switching valve 12 Pressure sensor 13 Temperature sensor 14 Pressure relief valve 15 fourth line 16 Check valve 21 cylinders 22 LPG injection valve 23 CNG injection valve

Claims

[1] Arrangement (1) in a motor vehicle with a fuel tank (2) for storing at least two different types of fuel, wherein the tank (2) is divided into at least a first compartment (3) and a second compartment (4), each with a variable volume, the first compartment (3) being assigned to a first type of fuel and the second compartment (4) to a second type of fuel, and the two compartments (3, 4) being separated from one another by a membrane (5), wherein the position of the membrane (5) within the tank (2) can be changed, further comprising a gas switching valve (11), a pressure limiting valve (14), at least one pressure sensor (12) and an internal combustion engine (10) with at least one cylinder (21), each of which has an injector for liquid or gaseous fuel. [2] Arrangement (1) according to claim 1, wherein the membrane (5) is a flexible film. [3] Arrangement (1) according to claim 1 or 2, wherein the first compartment (3) is provided for a liquid fuel and the second compartment (4) is provided for a gaseous fuel. [4] Arrangement (1) according to claim 3, wherein liquefied petroleum gas is provided as the first fuel and natural gas is provided as the second fuel. [5] Arrangement (1) according to one of the preceding claims, in which the second compartment (4) can be filled with a pressure of up to 200 bar. [6] A method for operating an internal combustion engine (10) with a fuel from a tank in an arrangement according to any one of claims 1-5, comprising the steps: - Adjusting the membrane (5) separating the first (3) from the second compartment (4) by means of a coil (6) so that the membrane (5) is moved towards the second compartment (4), - filling the first compartment (3) of the tank (2) with a liquid fuel at ambient pressure, - filling the second compartment (4) of the tank (2) with a gaseous fuel until the pressure is at least 150 bar, - introducing the liquid fuel to an injection device (22) of a cylinder (21) under the pressure exerted by the gaseous fuel in the second compartment (4) on the liquid fuel in the first compartment (3). [7] Method according to claim 6, wherein the pressure in the second compartment (4) is set to up to 200 bar. [8] Method according to claim 6 or 7, wherein the pressure on the liquid fuel depends on the volume ratio of the first compartment (3) to the second compartment (4). [9] Method according to one of claims 6-8, wherein the internal combustion engine (10) is operated with the gaseous fuel when the liquid fuel in the first compartment (3) is consumed.

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