Double-walled tube for delivering high-pressure fuel and fuel system of internal combustion piston engine

Abstract

The invention relates to a double-walled tube (10) for conveying high-pressure fuel, comprising a first tube (402) forming a fluid flow channel (404) within the first tube and a second tube (406) arranged coaxially around the first tube, in which the double-walled tube (10) comprises at least two rings of the double-walled tube (10) around an axis and the double-walled tube (10) comprises a variable pitch.

Description

TECHNICAL FIELD

[0001] The invention relates to a double-walled pipe for conveying high-pressure fuel according to the preamble of claim 1, comprising a first pipe forming a fluid flow passage within said first pipe and a second pipe arranged coaxially around said first pipe.

[0002] The invention relates to a fuel system of an internal combustion piston engine according to the preamble of the second independent claim. BACKGROUND

[0003] Fuel combustion in internal combustion engines requires high injection pressure of the fuel in order to achieve efficient combustion resulting in low emissions. As a consequence, fuel needs to be supplied at high pressure, which sets high requirements to the fuel delivery pipes. The engine tends to vibrate when in operation and the fuel flowing in the fuel delivery pipes is also subjected to pressure pulsations. Due to typical engine behavior, vibrations in a relatively high frequency range are common. This in turn creates a risk of the fuel delivery pipes vibrating. Vibrations are detrimental as they also increase the fatigue of the pipe material over time. Another problem is that when the engine is installed in a marine vessel, oscillations at a relatively low frequency are common due to the nature of the vessel motion on a rough sea surface.

[0004] There is an increasing need for large internal combustion engines, such as marine and power plant engines, which can be operated using other types of fuel than conventional liquid fuels, such as light fuel oil or heavy fuel oil. The alternative fuel can be a liquid fuel, such as methanol or ammonia, or a gaseous fuel, such as natural gas or hydrogen.

[0005] The use of alternative fuels helps to reduce carbon dioxide and other emissions from the engine. However, the use of alternative fuels also presents many challenges. For example, the leakage of gaseous fuels presents a more serious safety risk than the leakage of liquid fuels with a high flash point. Also, some fuels, such as methanol, can be more toxic than conventional fuels, such as light fuel oil.

[0006] In many cases, the use of alternative fuels results in the need for additional safety measures. A common safety measure to address the risk of fire and vapour poisoning is to use double-walled pipes to deliver the fuel and to house the high-pressure supply unit inside a dedicated ventilated room or compartment. In this way, the high-pressure fuel supply becomes too bulky to be placed on the engine and needs to be placed outside the engine. Given the nature of the motion of marine engine vessels, it is also necessary to develop fuel pipes that comply with safety standards in addition to being able to withstand the relative motion between the engine and the connection point of the external high-pressure fuel system.

[0007] It is known, for example from the publication US10157690B2, to wind a pipe into a spiral, wherein the pipe is provided with spiral sections for obtaining the possibility of expanding the length and direction of the pipe through such spiral sections.

[0008] EP2878804A1 discloses a fluid damper comprising a tubular member having a fluid flowing within it. The tubular member is shaped to be flexible and provides a degree of freedom to disperse hydraulic waves propagating in said tubular member. The shape of the tubular member can be a helical spring, or a serpentine made of a series of U-shaped sections or V-shaped, or square, or sinusoidal or other shapes or any combination of said shapes.

[0009] US3245431A discloses an extendable, coiled fluid transfer line device for transferring actuating fluid used, for example, between relatively movable parts of a mechanism.

[0010] US3402743A discloses a pipe for carrying fluid under pressure having a helical section which allows oscillation along the helical axis and pivotal movement in a plane perpendicular to the helical axis. One of the ends of the helix extends inwards to its axis and then outwards on the axis so that there is only a simple stress even when the end is connected to a pivotally oscillating member.

[0011] US8038178B2 discloses a high pressure fuel pipe construction for internal combustion engines, for example direct injection engines. To dampen the vibrations of the fluid conduit, the fluid conduit also preferably comprises a ring between its ends. A damper made of an elastic material, such as an elastomer material, is then attached to the ring.

[0012] US7228846B2 discloses an apparatus for damping pressure pulsations and attenuating noise transmission in a fuel supply system. The apparatus includes a first end in fluid communication with a fuel supply line, a second end in fluid communication with a manifold, and a body coupled in fluid communication with the first end and the second end. The body includes a tube helically disposed about a central axis.

[0013] Thus, these can provide at least some remedy to the vibrations, but there is a need for improved damping of vibrations in fuel supply lines of internal combustion engines.

[0014] It is an object of the present invention to provide a double-walled pipe for transporting high pressure fuel, in which the damping of vibrations is significantly improved compared to prior art solutions. SUMMARY

[0015] The object of the present invention can be substantially met as disclosed in the independent claims and in the other claims dependent on the more detailed description of different embodiments of the invention.

[0016] A double-walled tube for conveying high-pressure fuel according to the invention comprises a first tube forming a fluid flow channel inside the tube and a second tube arranged coaxially around the first tube, further comprising at least two loops of the double-walled tube around an axis, wherein the double-walled tube comprises segments with a variable pitch.

[0017] In this way, the double-walled tube forms a spiral which provides a double-walled tube that effectively attenuates vibrations in the double-walled tube. When the pitch is variable, it is not constant, but it has a varying pitch between the two ends of the double-walled tube. Providing a coiled double-walled tube with a variable pitch interferes with the natural frequency phenomenon due to the continuous variation of the pitch. Having a continuously varying pitch helps to reduce the peak oscillation amplitude in the double-walled tube, which is usually caused by the natural frequency of the component.

[0018] According to an aspect of the invention, the pitch varies in a continuous manner, preferably in a linear manner.

[0019] There is a space between the first tube and the second tube, which is essentially an annular space, so the tube combination is referred to as a double-walled pipe. The double-walled tube with continuously varying variable pitch spiral segments according to the invention is particularly advantageous for transferring high-pressure fuel to an internal combustion piston engine, as it effectively attenuates vibrations caused by the natural frequency of the engine when in operation.

[0020] According to an aspect of the invention, the double-walled tube comprises at least three segments, said at least three segments having a first segment with an average first pitch, a second segment with an average second pitch, and a third segment with an average first pitch.

[0021] According to an aspect of the invention, the second segment is between the first segment and the third segment. In other words, the first segment and the third segment can be referred to as end segments, and the second segment can be referred to as an intermediate segment, wherein the end segments have a common average pitch that deviates from the average pitch of the intermediate segment.

[0022] According to an aspect of the invention, the average second pitch is greater than the average first pitch.

[0023] According to an aspect of the invention, the double-walled tube is in the form of a spiral, and the first segment, the second segment and the third segment are arranged between a fourth segment and a fifth segment, the fourth segment and the fifth segment having a zero pitch.

[0024] According to an aspect of the invention, the second segment is between the first segment and the third segment, and the first segment is provided with a linearly increasing pitch having a first slope, the second segment comprises a portion with a linearly decreasing pitch having a second slope and a portion with a linearly increasing pitch having a third slope, and the third segment is provided with a linearly decreasing pitch having a fourth slope.

[0025] Preferably, the average first pitch of the first section is equal to the average third pitch of the third section, the average second pitch is greater than the average first pitch, and the third section is arranged between the fourth section and the fifth section, the fourth section and the fifth section having zero pitch.

[0026] As fuel feeding double-wall tube, the double-wall tube is preferably designed to withstand a peak pressure of more than 2000 bar, designed to withstand a temperature of more than 100°C and / or made of steel.

[0027] According to an aspect of the invention, the ring forms a constant diameter spiral around the central axis.

[0028] According to an aspect of the invention, the double-wall tube has a start point, an end point and a midpoint, wherein the variable pitch between the midpoint and the start point and the pitch between the midpoint and the end point are symmetrical.

[0029] According to an aspect of the invention, the double-wall tube has a start point, an end point and a midpoint, wherein the variable pitch between the midpoint and the start point and the pitch between the midpoint and the end point are symmetrical.

[0030] When the fuel supply device comprising a high-pressure fuel pump unit capable of raising the fuel pressure to a required fuel admission pressure is external to the engine, for example in a ventilated and fireproof compartment, an improved safety of the fuel handling is achieved.

[0031] The invention provides, inter alia, the following general effects.

[0032] Placing a high-pressure, e.g. up to 2000 bar, fuel supply device external to the engine brings challenges in terms of relative movements between the engine fuel supply connection and the external fixation point, which are now solved by the invention.

[0033] The flexible high-pressure fuel double-wall tube with continuously variable pitch according to the invention avoids or at least minimizes inherent frequencies over a wide range. The double-wall tube according to the invention does not have a unique single specific inherent frequency, but has a variable inherent frequency.

[0034] In this context, a feature double-wall tube refers to the double-wall tube as an entity from one end thereof to the second end, or a section of the double-wall tube system, which can include other parts of the double-wall tube system attached to one or both ends of the double-wall tube, either integrally or in a removable manner, unless explicitly stated otherwise. A pitch is a positive number greater than zero, unless specifically stated otherwise.

[0035] The exemplary embodiments of the invention presented in this patent application should not be construed as limiting the applicability of the appended claims. The verb "comprising" is used in this patent application as an open limitation that does not exclude the presence of features not yet described. Unless expressly stated otherwise, the features described in the dependent claims may be freely combined with each other. Novel features considered to be characteristics of the invention are specifically set forth in the appended claims. Attached Figure Description

[0036] In the following description, the invention will be illustrated with reference to the accompanying exemplary schematic diagrams, wherein...

[0037] Figure 1 A double-walled pipe for conveying high-pressure fuel according to an embodiment of the present invention is shown.

[0038] Figure 2 It shows Figure 1 Front view of a double-walled tube.

[0039] Figure 3 It shows Figure 2 Sections II-III,

[0040] Figure 4 It shows Figure 3 Detail 4 in the text

[0041] Figure 5 A double-walled pipe for conveying high-pressure fuel according to an embodiment of the present invention is shown.

[0042] Figure 6 The fuel system of an internal combustion piston engine is shown, as well as

[0043] Figure 7 An example of the spacing in a double-walled tube is shown. Detailed Implementation

[0044] Figure 1 An embodiment of the invention is schematically depicted. The double-walled tube 10 is arranged to deliver high-pressure fuel from a high-pressure fuel source to a fuel-consuming device, such as an internal combustion engine in a ship or land-based power plant. (As in...) Figure 1 As disclosed herein, the double-walled tube 10 includes two semi-rings 14 of the double-walled tube surrounding an axis A. It is also clear that the double-walled tubes or rings have a spacing, meaning that the helix formed by the annular double-walled tubes has a height or pitch measured parallel to the axis A of the helix, which is a complete loop. Connecting portions 12 are provided at both ends of the double-walled tube 10 for attaching the double-walled tube to a double-walled tube system. The connecting portions 12 are formed by straight extensions of the double-walled tube. The connecting portions may include suitable bends to guide the ends of the connecting portions in a desired direction. Figure 2 A view of the double-walled tube 10 as seen from the front of the double-walled tube ring along axis A is disclosed. The double-walled tube 12 has an outer diameter D.o . refer to Figure 4 It shows Figure 3 Detail 4, namely the cross-section of the double-walled pipe, describes the double-walled pipe 10 as follows: The double-walled pipe 10 includes a first pipe 402 forming a fluid flow passage 404 inside the first pipe 402, and a second pipe 406 arranged coaxially around the first pipe 402. In the double-walled pipe 10, the inner pipe 402 for conveying fuel and the outer pipe 406 arranged coaxially around the inner pipe 402 form an annular leak space between the two pipes. The leak space collects fuel that may leak from the inner pipe 402 and allows for leak detection and relocation of leaked fuel to a safe location, such as a tank or outdoors. In the event of a leak and / or as a safety measure prior to maintenance, the inner pipe and the leak space can be purged using an inert gas, such as nitrogen.

[0045] The double-walled tubes are arranged in a circular ring, with the centerline of the double-walled tube 10 forming a diameter D. L The diameter depends on the relative movement between the ends of the double-walled tube, the number of rings, and the diameter of the double-walled tube. In this particular embodiment, the helical diameter D... L It can be defined as 20-35 × the outer diameter D of the double-walled pipe. o .

[0046] Turn now Figure 3 It shows Figure 2 Section III-III shows more clearly the double-walled tube 10 with variable spacing, having sections 16.1, 16.2, and 16.3. It should be noted that in... Figure 3The figure shows that the advance in the direction of axis A is half the length of the ring. The number of different segments can vary, such that there are at least three segments, having a first segment, a second segment, and a third segment, the first segment having an average first spacing, the second segment having an average second spacing, and the third segment having an average first spacing, or even more than three segments. In the embodiment shown in the figure, the double-walled tube 10 includes three segments 16.1, 16.2, and 16.3, having a first segment 16.1 with an average first spacing, a second segment 16.2 with an average second spacing, and a third segment 16.2 with an average third spacing. Preferably, the spacing varies dynamically in a linear manner between defined spacing points. In this embodiment, the second segment 16.2 is between the first segment 16.1 and the third segment 16.3, and the average first spacing 16.1' is equal to the average third spacing 16.3'. It can also be seen that the average second spacing 16.2' is smaller than the average first spacing 16.1' and the average third spacing 16.3'. Preferably, the double-walled tube further includes a fourth segment 16.4 and a fifth segment 16.5, which are located on both sides of the combined double-walled tube component including the first segment, the second segment, and the third segment, and have zero spacing. In other words, the first segment, the second segment, and the third segment are arranged between the fourth segment and the fifth segment.

[0047] The double-walled tube is configured to supply pressurized fuel to the engine, and therefore the double-walled tube has at least one of the following characteristics: the double-walled tube is designed to withstand peak pressures greater than 2000 bar, the double-walled tube is designed to withstand temperatures greater than 100°C, and the material of the double-walled tube or a section of the double-walled tube is steel.

[0048] Figure 5 A preferred embodiment of the invention is shown, wherein the double-walled tube has five sections and two semi-rings 14 in a helix (in Figure 3 (As shown in the image). Figure 5 In this context, the double-walled pipe is considered to be 100% of the length extending from point 1 to point 2, which are the starting point 1 and ending point 2 of the double-walled pipe 10. The straight connection 12 is not considered part of the helix. A midpoint 3 also exists in the pipe 10. The pipe length between midpoint 3 and starting point 1 is equal to the length between midpoint 3 and ending point 2.

[0049] At both ends of the double-walled tube 10, there are two sections, the fourth section 16.4 and the fifth section 16.5, indicated by denser dashed lines. Next to the fourth and fifth sections 16.4 and 16.5, there are the first and third sections 16.1 and 16.3, indicated by less dense dashed lines. Between the first and third sections 16.1 and 16.3, there is a second section 16.2, shown without shading. Exemplary spacing transitions and values ​​between specified helical curve points are shown in the table below (point-to-point spacing values). Here, a value of 900 degrees signifies two half-loops of the helix. The spacing as a function of the helix angle is... Figure 7 As shown, and as can be seen, the spacing varies in a continuously variable manner. More precisely, in this example, the spacing varies linearly between points 2 and 6, with different slopes between points 2 and 3; 3 and 4; 4 and 5; and 5 and 6, which is a preferred embodiment of the invention.

[0050]

[0051] It can be seen that, preferably, the variable spacing distribution along the length of the double-walled tube 10 is symmetrical between the midpoint and the starting point, and between the midpoint and the ending point. Furthermore, the first segment 16.1 is provided with a linearly increasing spacing with a first slope, the second segment 16.2 includes a portion with a linearly decreasing spacing (negative slope) with a second slope and a portion with a linearly increasing spacing with a third slope, and the third segment 16.3 is provided with a linearly decreasing spacing (negative slope) with a fourth slope. The fourth segment 16.4 and the fifth segment 16.5 have a constant zero spacing. Figure 7 In the equation, the absolute value of the first slope is equal to the absolute value of the fourth slope, and the absolute value of the second slope is equal to the absolute value of the third slope.

[0052] Figure 6 A fuel system 60 for an internal combustion piston engine 62 is shown. The fuel system 60 includes a fuel supply device 64, which includes, for example, a high-pressure pump or a generally high-pressure fuel source. High pressure means a pressure suitable for use as an injection pressure. The fuel supply device 64 is attached to a base 66 external to the engine. The base can be, for example, the hull of a marine vessel or a support structure connected to the hull. The fuel supply device 64 is provided with a first connector 68 for supplying a fuel supply double-walled pipe 10. The engine is provided with a fuel inlet device 70 having a second connector 72 for supplying the fuel supply double-walled pipe 10, wherein the fuel supply double-walled pipe 10 according to the invention is arranged between the first connector 68 and the second connector 75.

[0053] While the invention has been described by way of example with reference to embodiments currently considered to be the most preferred, it will be apparent to those skilled in the art that the basic ideas of the invention can be implemented in many ways as technology advances. Therefore, the invention and its embodiments are not limited to the examples and samples described above, but can be varied within the scope of the patent claims and their legal equivalents. When such a combination is technically feasible, the details mentioned in any of the foregoing embodiments can be used in conjunction with another embodiment.

Claims

1. A double-walled pipe (10) for conveying high-pressure fuel, the double-walled pipe comprising a first pipe (402) and a second pipe (406), wherein the first pipe forms a fluid flow channel (404) within the first pipe, and the second pipe is arranged coaxially around the first pipe, wherein, The double-walled tube (10) includes at least two rings around an axis, characterized in that the double-walled tube (10) includes segments with variable spacing.

2. The double-walled tube (10) according to claim 1, characterized in that, The double-walled tube (10) includes at least three sections (16.1, 16.2, 16.3), the at least three sections including a first section (16.1) having an average first spacing, a second section (16.2) having an average second spacing, and a third section (16.2) having the average first spacing.

3. The double-walled tube (10) according to claim 2, characterized in that, The second segment (16.2) is located between the first segment (16.1) and the third segment (16.3).

4. The double-walled tube (10) according to claim 3, characterized in that, The average second spacing is greater than the average first spacing.

5. The double-walled tube (10) according to any one of the preceding claims, characterized in that, The spacing varies continuously.

6. The double-walled tube (10) according to claim 5, characterized in that, The spacing varies linearly.

7. The double-walled tube (10) according to any one of the preceding claims, characterized in that, The first segment (16.1), the second segment (16.2) and the third segment (16.3) are arranged between the fourth segment (16.4) and the fifth segment (16.5), the fourth segment and the fifth segment having zero spacing.

8. The double-walled tube (10) according to any one of claims 1 to 5, characterized in that, The double-walled tube (10) has a starting point (1), an ending point (2), and a midpoint (3), wherein the variable spacing between the midpoint (3) and the starting point (1) and the spacing between the midpoint (3) and the ending point (2) are symmetrical.

9. The double-walled tube (10) according to claim 2, characterized in that, The first section (16.1) is provided with a linearly increasing spacing with a first slope, the second section (16.2) includes a portion with a linearly decreasing spacing with a second slope and a portion with a linearly increasing spacing with a third slope, and the third section (16.2) is provided with a linearly decreasing spacing with a fourth slope.

10. The double-walled tube (10) according to claim 1, characterized in that, The double-walled tube (10) is designed to withstand pressures greater than 2000 bar.

11. The double-walled tube (10) according to claim 1, characterized in that, The double-walled tube (10) is designed to withstand temperatures greater than 100°C.

12. The double-walled tube (10) according to claim 1, characterized in that, The ring forms a spiral of constant diameter around the central axis.

13. The double-walled tube (10) according to claim 1, characterized in that, The material of the double-walled tube (10) or a section of the double-walled tube (10) is steel.

14. A fuel system for an internal combustion piston engine, the fuel system comprising a fuel supply device attached to a base outside the engine, the device having a first connector for a fuel supply double-walled pipe (10), and a fuel inlet device in the engine having a second connector for the fuel supply double-walled pipe (10), wherein the fuel supply double-walled pipe (10) is arranged between the first connector and the second connector, characterized in that, The fuel supply double-walled pipe (10) system includes a double-walled pipe (10) according to any one of the preceding claims.

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