Technical field

[001 ] The present invention relates to a fuel supply arrangement for an internal combustion engine according to the preamble of claim 1 .

[002] The present invention relates also to a method of filtering fuel in a fuel supply arrangement of an internal combustion engine.

Background art

[003] Typically, a fuel system of an internal combustion engine is equipped with a low pressure fuel convey line, a fuel filter section and a high pressure fuel convey line. The low pressure fuel convey line is provided with a feed pump for pumping fuel from a fuel source into the fuel convey line and transfer the fuel to the engine. The fuel is generally filtered in the filter section in the low pressure fuel convey line and then fed into the high fuel convey line wherein the high-pressure pump pressuriz- es the filtered fuel to a predetermined pressure. Extremely low particle contents in fuel supply are required to achieve desired lifetime for fuel injection equipment components. Stringent filtering requirements tend to lead very short filter change intervals.

[004] DE 102012018504 A1 discloses a fuel delivery module of a com- mon rail fuel injection system. The module comprises a fuel strainer, a fine fuel filter, a valve device and a fuel feed pump which is arranged between the fuel strainer and the fine fuel filter along flow direction. [005] US 2014/0174407 A1 discloses a fuel supply system that includes a feeder fuel circuit configured to i) convey a first fuel in a direction of a mixing tank via a first pump device proceeding from a first fuel tank for a first fuel type, or ii) convey a second fuel in the direction of the mixing tank via the first pump device proceeding from a second fuel tank for a second fuel type, and a booster fuel circuit configured to convey fuel via a second pump device proceeding from the mixing tank in a direction of at least one marine diesel engine. The booster fuel circuit has an automatic fine filter positioned upstream of or downstream of the at least one marine diesel engine and in the booster fuel circuit, respectively.

[006] US 2009/0145403 A1 discloses a fuel supply system having a fuel filter installed downstream of feed pump. The fuel supply system includes a priming pump, a feed pump, a fuel filter disposed downstream of the feed pump, a return path, and a return valve. In case the pressure of the fuel between the feed pump and the fuel filter exceeds a first set pressure, the return valve is set to a first open position to open the return path to return the fuel from downstream to upstream of the feed pump. In case the pressure of the fuel, as fed by the priming pump, exceeds a second set pressure, the return valve is set to a second open position to open the return path to direct the fuel, as fed by the priming pump, to upstream of the fuel filter to prime the fuel filter directly.

[007] An object of the invention is to provide a fuel supply arrangement for an internal combustion engine in which the filter lifetime is extended so as to extend the filter change interval.

Disclosure of the Invention

[008] An object of the invention is met by a fuel supply arrangement for an internal combustion engine comprising a fuel convey line extending from a fuel source to the engine, which fuel convey line comprising a first pump for pumping the fuel from the fuel source into a first fuel path and feeding the fuel from the first fuel path to a second fuel path, the first fuel path is provided with a first filtration section, the second fuel path is provided with a second pump for pressurising filtered fuel to a predeter- mined pressure. It is characteristic to the invention that the first fuel path is provided with a return line leading back to the fuel source downstream from the first filtration section so that the first fuel path forms a circulation path via the first filtration section, and that the second fuel path is arranged to deliver the fuel from the first fuel path to the engine and that the second fuel path is provided with a second filtration section.

[009] This provides a fuel supply arrangement for an internal combustion engine which fuel filtering performance is considerably improved. The fuel is filtered in a more efficient way compared to the prior art solu- tions. In addition, the fuel supply arrangement provides an extended filter change interval. Therefore, desired common rail fuel injection element component lifetimes are advantageously met.

[0010] According to an embodiment of the invention, the first filtration section comprises a first filter and a second filter, which second filter is arranged downstream the first filter and upstream the second fuel path. Directions downstream and upstream herein refers to fuel flow direction when flowing from the fuel source into the first fuel path and continuing its flow into the second fuel path.

[001 1 ] According to an embodiment of the invention, the first filter is arranged to filter out particles from fuel having a first particulate size and the second filter is arranged to filter out particles having a second particulate size which second particulate size is smaller than the first par- ticulate size. [0012] According to an embodiment of the invention, the first filter is arranged on a suction side of the first pump being arranged between the fuel source and the first pump. [0013] According to an embodiment of the invention, the second filtration section is arranged to filter out particles having a third particulate size, which third particulate size is smaller than the second particulate size.

[0014] According to an embodiment of the invention, the second filtration section is provided with two filter elements: a third filter and a fourth filter arranged in parallel with respect to each other.

[0015] According to an embodiment of the invention, the second filtration section is arranged upstream the second pump.

[0016] According to an embodiment of the invention, the first filter is a strainer and it is arranged to filter out particles greater than 0.5 mm.

[0017] According to an embodiment of the invention, that the second filter is an automatic back flushing filter and it is arranged to filter out particles greater than 20 μιτι.

[0018] According to an embodiment of the invention, the first filtration section is provided with a conduit from the second filter to an external tank so as to discharge at least a portion of particles blocked by the first filtration section.

[0019] According to an embodiment of the invention, the third filter is a fine filter and it is arranged to filter out particles greater than 2 μιη.

[0020] According to an embodiment of the invention, the return line is provided with a valve. The valve is arranged to prevent fuel to flow from the fuel source via the return line into the first fuel path. According to an embodiment of the invention, the valve is a relief valve. [0021 ] According to an embodiment of the invention, a control system is arranged to control circulation of at least the portion of fuel back from the first fuel path into the fuel source based on the engine's load conditions.

[0022] According to an embodiment of the invention, a flow rate capacity of the first pump is 2 - 3 greater than a flow rate capacity of the second pump. [0023] According to an embodiment of the invention, the first fuel path is provided with a by-pass line having an inlet between the fuel source and the first filter and an outlet between the first pump and the second filter, and that the by-pass line comprises a pump. This pump is arranged to pump fuel from the fuel source into the first fuel path to be filtered in the second filter of the first filtration section.

[0024] Another object of the invention is met by a method of filtering fuel in a fuel supply arrangement of an internal combustion engine, the method comprising steps of 1 ) pumping fuel with a first pump from a fuel source to a first fuel path, 2) filtering fuel in the first fuel path in a first filtering section thus forming filtered fuel and 3) feeding a first portion of the filtered fuel from the first fuel path to a second fuel path, 4) filtering the first portion of fuel in the second fuel path in a second filtering section and 5) pressurizing the first portion of filtered fuel in the second fuel path to a predetermined pressure with a second pump and 6) circulating at least a second portion of filtered fuel from the first path back to the fuel source.

[0025] This provides an efficient method to filter fuel. In addition, due to the circulation via the first filtration section, it enhances the lifetime of the second filtration section. This way the filter change interval in the second filtration section is extended. Furthermore, extremely tight filtration requirements are met. [0026] According to an embodiment of the invention, the method comprises steps of feeding the first portion of the filtered fuel from the first fuel path to a second fuel path and circulating a second portion of the fil- tered fuel back to the fuel source.

[0027] According to an embodiment of the invention, the method comprises steps of filtering out particles in the first fuel path in two preceding steps i) filtering out particles having a first particulate size and ii) filtering out particles having a second particulate size which second particulate size is smaller than the first particulate size.

[0028] According to an embodiment of the invention, the method comprises steps of filtering out particles in the first fuel path in two preceding steps i) filtering out particles greater than 0.5 mm and ii) filtering out particles greater than 20 μιτι.

[0029] According to an embodiment of the invention, the method comprises steps of discharging at least a portion of particles blocked by the first filtration section from the first fuel path to an external tank.

[0030] According to an embodiment of the invention, the method comprises steps of filtering out particles in the second fuel path comprising steps of filtering out particles having a third particulate size, which third particulate size is smaller than the second particulate size.

[0031 ] According to an embodiment of the invention, the method comprises steps of filtering out particles greater than 2 μιη in the second fuel path.

[0032] According to an embodiment of the invention, the method comprises steps of controlling feeding of the first fuel portion from the first fuel path to the second fuel path based on the engine's load conditions. [0033] According to an embodiment of the invention, the method comprises steps of controlling circulation of at least the portion of fuel back from the first fuel path into the fuel source based on the engine's load conditions.

Brief Description of Drawings

[0034] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates a fuel supply arrangement of an internal combustion engine according to the first embodiment of the invention,

Figure 2 illustrates a fuel supply arrangement of an internal combustion engine according to the second embodiment of the invention,

Figure 3 illustrates a fuel supply arrangement of an internal combustion engine according to the third embodiment of the invention.

Detailed Description of Drawings [0035] Figure 1 depicts schematically a fuel supply arrangement 10 for an internal combustion engine 100 comprising a fuel convey line 12 extending from a fuel source 14 to the engine 100. According to an embodiment of the invention, the fuel source 14 is a fuel tank or a so-called day tank. The fuel convey line 12 comprises a first fuel path 18 and a second fuel path 20. The first fuel path 18 and the second fuel path 20 are arranged in flow communication with each other and arranged one after another in the fuel flow direction. Therefore, at least a portion of the fuel from the first fuel path 18 may be introduced to the second fuel path 20. [0036] The first fuel path 18 is provided with a first pump 16 and a first filtration section 30. The second fuel path 20 is provided with a valve element 60, a second filtration section 50 and a second pump 22. The first pump 16, the first filtering section 32, the second filtering section 50 and the second pump 22 are arranged in series in the fuel convey line 12. The second fuel path 20 leads to a fuel injector or fuel injectors 90 of the engine 100. Figure 1 illustrates schematically only one fuel injector 90. Each of fuel injector 90 injects the fuel into a combustion chamber of a cylinder of the engine (not shown in figures).

[0037] The fuel convey line 12 comprises the first pump 16 coupled with the first fuel path 18 for pumping the fuel from the fuel source 14 into the first fuel path 18. The first pump 16 is arranged to the first fuel path 18 downstream the fuel source 14 and is called as a feed pump. According to an embodiment of the invention, the first pump 16 is an electronically driven pump coupled with an electric motor. [0038] The first filtration section 30 is coupled to the first fuel path 18 of the fuel convey line 12 downstream of the first pump 16 in a direction from the fuel source 14 to the engine 100. The direction from the fuel source 14 to the engine 100 refers to a direction of fuel flow from the fuel source 14 into the first fuel path 18 continuing its flow towards the sec- ond fuel path 20. The first filtration section 30 coupled to the first fuel path 18 of the fuel convey line 12 is provided with a filter element 32. Fuel filter elements need to be maintained at regular intervals. According to an embodiment of the invention the filter element 32 is an automatic filter, which is arranged to automatically regenerate or maintain the filtra- tion capacity of the filter element. The automatic filter is arranged to filter out particles greater than 20 μιτι. The automatic filter uses a so-called surface filtration technology meaning that the particles larger than a filtering grade of the filter deposit on an upstream side surface of the filter. [0039] Specifically, the first fuel path 18 is provided with a return line 24 leading back to the fuel source 14. The return line 24 is arranged downstream the first filtration section 30. The return line 24 has an inlet 26 at the first fuel path 18 and outlet 28 at the fuel source 14. The inlet 26 is connected to the convey line 12 upstream the second filtration section 50. The first fuel path 18, the return line 24 and the fuel source 14 forms a circulation path 40. Advantageously, the fuel is filtered by the first filtra- tion section 30 during the circulation via the circulation path 40. In addition, this provides pre-cleaning of the fuel in the fuel source 14.

[0040] The return line 24 illustrated in Figure 1 is provided with a valve 66. Advantageously, the valve 66 is a pressure relief valve. When the pressure in the first fuel path 18 increases at or above a predetermined pressure, the valve 66 opens a flow communication from the first fuel path 18 to the return line 24. Unfiltered fuel from the fuel source 14 is prevented to flow via the return line 24 into the second fuel path 22. At least a portion of fuel from the first fuel path 18 is returned back into the fuel source 14 via the return line 24. When the pressure in the first fuel path 18 remains at or above the predetermined limit, there is substantially constant fuel circulation via the first fuel path 18 and the return line 24 that is via the circulation path 40. This provides pre-cleaning for the fuel source 14 i.e. a fuel tank or alike.

[0041 ] The second fuel path 20 is provided with the valve element 60 arranged downstream the first filtration section 30. The valve element is used for controlling the fuel flow from the fuel source 14 and from the first fuel path 18 into the second fuel path 20. When the valve element 60 is closed, fuel circulates in the circulation path 40 comprising the first fuel path 18 and the return line 24 and the fuel source 14. When the valve element 60 is open, the fuel is allowed to flow from the first fuel path 18 into the second fuel path 20 towards the second filtration section 50 and the second pump 22 arranged downstream the second filtration section 50 in the second fuel path 20. [0042] Advantageously, the circulation via the circulation path 40 enhances the filtration and extends the changing interval of the filter element 52 of the second filtration section 50. That is because only the fuel consumed by the engine 100 is going through the second filtration sec- tion 50. Less dirt is attached to the filter element 52 of the second filtration section 50 due to the circulation via the first filtration section 30.

[0043] The second fuel path 20 is arranged to deliver the fuel from the first fuel path 18 to the engine 100 when the valve element 60 is open and the pressure in the second fuel path 20 is adequate. The second fuel path 20 leads to the fuel injectors 90. The second fuel path 20 is provided with the second filtration section 50 arranged downstream the valve element 60. The second filtration section 50 is external from the engine 100, which means that it can be removably attached to the fuel supply arrangement 10. The second filtration section 50 is provided with at least one filter element 52. Advantageously, the first filtration section 30 is arranged to filter bigger particles than the second filtration section 50. In other words, the second filtration section 50 is arranged to filter smaller particles that are allowed to flow through the first filtration section. Thus, the filter element 52 of the second filtration section 50 is called as a fine filter whereas the filter element 32 of the first filtration section 30 is called as a coarse filter. This provides a very efficient fuel filtering arrangement. The two phase filtering also extends the changing interval of the filter/filters arranged in the second filtration section 50.

[0044] According to an embodiment of the invention, the second filtration section 50 is arranged to filter out particles greater than 2 μιη. According to an embodiment of the invention, the second filtration section 50 is made out of glass fiber. Thus, the filter element 52 of the second filtration section uses a so-called depth filtration technology, meaning that particles are captured within the filter media. [0045] The second fuel path 20 of the fuel convey line 12 is also provided with the second pump 22 arranged downstream of the second filtration section 50. Thus the second filtration section 50 is advantageously arranged on a suction side of the second pump 22. By means of the sec- ond pump 22 the filtered fuel is pressurised to a predetermined pressure. From the second pump 22, the fuel is introduced to the fuel injectors 90 of the engine and further to the combustion chambers (not shown in Fig. 1 ). Figure 1 illustrates only schematically one fuel injector 90. It should be noted that there can be other components arranged between the sec- ond pump 22 and the fuel injector 90, such as a common rail, which are not shown for the sake of simplicity.

[0046] According to the invention, the fuel convey line 12 can be divided into two fuel convey lines: a low pressure fuel convey line and a high pressure fuel convey line. As these names indicate, the pressure is higher in the high pressure fuel convey line than in the low pressure fuel convey line. According to an embodiment of the invention, the second pump 22 is a so-called a high pressure pump that pressurizes the filtered fuel to the predetermined pressure and introduces fuel to the fuel injectors 90. The first fuel path 18 comprising the first pump 16 and the first filtration section 30, the return line 24, the valve element 60 and the second filtration section 50 are arranged in the low pressure fuel convey line upstream the second pump 22. [0047] According to an embodiment of the invention, the fuel supply arrangement 10 is provided with a control unit 80. The control unit 80 is arranged to control an operation of the first pump 16, an operation of the valve element 60 and an operation of the second pump 22. The fuel circulation in the circulation path 40 is controlled via the first pump 16 based on a fuel quantity demand downstream the second pump 22. According to an embodiment of the invention, the control unit 80 comprises instructions to circulate the fuel in the circulation path 40 based on the load of the engine.

[0048] According to another embodiment of the invention, the control unit 80 comprises instructions to circulate the fuel in the circulation path 40 based on the demand of the fuel flow via the second pump 22 to the fuel injectors 90. The circulation of fuel is based on the operational load conditions of the engine 100. According to an embodiment of the invention, a flow rate capacity of the first pump 16 is 2 - 3 greater than a flow rate capacity of the second pump 22. Therefore, it is possible to provide efficiently filtered fuel at different engine's loads.

[0049] Figure 2 illustrates schematically another embodiment of the fuel supply arrangement 10. Substantially same features are shown using the same reference numbers as in Figure 1 . However, the fuel supply arrangement 10 comprises a first filtration section 30 which comprises two filter elements: a first filter 34 and a second filter 32. The first filter 34 is arranged to the first fuel path 18 between the fuel source 14 and the first pump 16. Thus the first filter 34 is arranged upstream the second filter 32 in a direction from the fuel source 14 to the second pump 22 arranged in the second fuel path 20. The first filter 34 of the first filtration section 30 is arranged also on a suction side of the first pump 16. According to an embodiment, the first filter 34 is arranged to filter out particles having a first particulate size and the second filter 32 is arranged to filter out parti- cles having a second particulate size which second particulate size is smaller than the first particulate size. According to an embodiment of the invention, the first filter 34 is a so-called strainer. For example, the first filter filters out particles greater than 0.5 mm. According to an embodiment of the invention, the second filter 32 is an automatic back flushing filter. The first filtration section 30 is provided with a conduit 36 connected with the second filter 32 of the first filtration section 32 and leading from the first filtration section 30 to an external tank 38. Particles blocked by the second filter 32 of the first filtration section 30 are discharged to the external tank 38 via the conduit 36. The second filter 32 is arranged to flush the particles or other dirt filtered form the fuel to the external tank 38. According to an embodiment of the invention, the particles blocked by the second filter 32 of the first filtration section 30 are discharged to the fuel source 14, such as the day tank, instead of the external tank 38. This is indicated by the dashed line in the figure. In an embodiment of the invention, the second filter 32 is arranged to flush the particles or other dirt filtered from the fuel back to the day tank 14 via the conduit 36. When the particles blocked by the second filter 32 of the first filtration section 30 are discharged back to the fuel source 14, there is no need to have an external tank arranged in this embodiment.

[0050] Particles greater than the second particulate sizes are discharged to the external tank 38 from the fuel via the second filter 32 of the first filtration section 30.

[0051 ] The second filtration section 50 is arranged in the second fuel path 20. The second filtration section 50 is provided with the filter 52. The filter 52 of the second filtration section 50 is called in this embodiment as a third filter. The third filter 52 is arranged to filter out particles having a third particulate size, which third particulate size is smaller than the second particulate size. According to an embodiment of the invention, a filtering grade of the first filter is 0.5 mm and a filtering grade of the second filter is 20 μιτι. According to an embodiment of the invention, a filtering grade of the third filter is 2 μιη.

[0052] Similarly as in Figure 1 , the fuel supply arrangement 10 is provided with the control unit 80. The control unit 80 is arranged to control the operation of the first pump 16, the valve element 60 and the operation of the second pump 22. The operation of the first pump 16 and circulation of fuel in the circulation path 40 is controlled by the control unit 80 based on the engine's load demands and a demand for feeding fuel to the fuel injectors 90. In other words, filtered fuel flows via the second filtration section 50 on demand from the second pump 22 wherefrom the fuel is introduced to the fuel injectors 90. [0053] Figure 3 illustrates a third embodiment of the fuel supply arrangement 10. Substantially same features are shown using the same reference numbers as in Figure 1 and Figure 2. In this embodiment, the second filtration section 50 is provided with two filter elements: a third filter 52 and a fourth filter 54. The third filter 52 and the fourth filter 54 are arranged in parallel with respect to each other. The second fuel path 20 is arranged with two valve elements: a first valve 62 arranged upstream the third filter 52 and the fourth filter 54 and a second valve 64 arranged downstream the third filter 52 and the fourth filter 54. In other words, the third filter 52 and the fourth filter 54 are arranged parallel with each other between the first valve 62 and the second valve 64. The second valve 64 is arranged upstream the second pump 22.

[0054] According to an embodiment of the invention, the first valve 62 and the second valve 64 are three-way valves. The first valve 62 has one inlet end and two outlet ends. A first outlet end is opening to the third filter 52 and a second outlet end is opening to the fourth filter 54. The second valve 64 has two inlet ends and one outlet end. A first inlet end of the second valve 64 is opening to the third filter 52 and a second inlet end of the second valve 64 is opening to the fourth filter 54. The outlet end of the second valve 64 is opening to the second pump 22. The control unit 80 is arranged to control an operation of the first valve 62 and the second valve 64. Due to the fact that the third filter 52 and the fourth filter 54 are arranged parallel with respect to each other, cartridges of the filters can be changed efficiently even though the engine is running.

[0055] The return line 24, illustrated in Figure 3, is provided with a valve 66, a relief valve similarly to the embodiment of figure 1 . [0056] According to an embodiment the fuel supply arrangement 10 is provided with a by-pass line 70. The by-pass line 70 has an inlet 72 and an outlet 76. The inlet 72 of the by-pass line 70 is arranged to the first fuel path 18 between the fuel source 14 and the first filter 34. The outlet 76 of the by-pass line 70 is arranged at the first fuel path 18 between the first pump 16 and the first filtration section 30. The outlet 76 is located between the first pump 16 and the second filter 32 of the first filtration section 30. According to an embodiment of the invention, the by-pass line 70 is provided with a third pump 74. According to an embodiment of the invention, the third pump 74 is an engine driven pump. There is no need for electric control when using the engine driven pump due to the fact that while the engine is running the engine driven pump 74 is pumping. The fuel can be introduced into the by-pass line 70 in case there is no need to filter great amounts of the fuel with the first filter 34 such as strainer. The by-pass line 70 and the third pump 74 are optional and thus indicated with a dashed lines. The control unit 80 comprises instructions to operate the third pump 74 in the by-pass line 70. Advantageously, the embodiment shown in Figure 3 meets the present classification rules which require that two parallel conduits for feeding fuel to the engine must be arranged for redundancy.

[0057] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the invention, as defined in the appended claims. The details mentioned in connection with any embodi- ment above may be used in connection with another embodiment when such combination is technically feasible.