Gas supply system for a gas engine.
The present invention relates to a gas supply system for a gas engine, comprising a double-walled pipe with an inner and an outer pipe for the supply of fuel gas to the cylinder units of the engine, where said double wall provides an outer, longitudinally running annular space along the whole length of the pipe and where the fuel gas is transported in the inner pipe.
A gas engine has normally a relatively large pipe for fuel gas along the engine (for V-type engines two pipes are used) . From this pipe a smaller pipe, possibly flexible, runs into each cylinder unit. In addition, there is normally a pipe along the engine for the pre-chamber gas (for V-type engines two pipes are used) . A smaller pipe also runs from this pipe into each cylinder unit. On engines supplied to power production on land these pipes are produced by welding and soldering.
A new market for the gas engine industry over the last years is ships with gas as fuel. This is a new market due to the regulations for release of exhausts, changes in charges and the building of an infrastructure for the filling of gas. When one places a gas engine in a ship it will be subjected to the regulations related to company classification and from the authorities. One of these requirements is that all gas pipes shall be double-walled, where the inner wall is used to carry gas to the engine and the outer pipe is used to detect any leaks from the inner pipe. This can possibly be carried out by a through- flow of air with a gas sensor in the system or a
pressurised inert gas system. The space between the inner and the outer pipes must be the same along the whole
length of the main pipe and out to every run to the cylinders. This is the case for the main gas and the pre- chamber gas.
The natural way to make these double-walled pipes is by welding. This is very difficult, time consuming and expensive. The welds on the inner pipe are the most important and these must also be controlled thoroughly. T get the pipe welded and controlled is difficult. In addition the pipes must be held in position toward the brackets on the engine block. These must be solid, machined constructions to be able to withstand the vibrations from the engine in the block and gas pipe. Because of this the brackets are expensive.
A fuel supply system is known from US 4,149,568 A for an engine with a double-walled pipe with an inner and an outer pipe for the supply of fuel to the cylinder units o the engine. The double wall shown in the patent document provides an outer, longitudinally running annular space along the whole length of the pipe and where the fuel is transported in the inner pipe.
Furthermore, reference is made to GB 2281111A, US
5,927,762 A and US 5,401,064 A where all the documents show double-walled pipes that are divided into sections, and that between said sections a coupling piece is placed to join the sections. Furthermore it is described in the documents that the coupling piece is internally open and comprises one or more channels to connect the
longitudinally running annular spaces between respective sections, and a boring to bring out the fuel or gas from the inner pipe and through an outlet.
Consequently it is an object of the present invention to provide a safe gas supply system for a gas engine, and which gives a simple and less labour demanding solution for the production, fitting and dismantling of pipes.
Said objects are reached with the system given in the independent claim 1, in that the double-walled pipe along the gas engine is divided into sections between respective cylinders where a coupling piece is inserted between said sections to add on to the sections, and that the coupling piece is open internally and comprises one or more
channels to connect the longitudinally running annular space between respective sections and a boring to bring out the fuel gas from the inner pipe and through an outlet of the respective cylinder units.
Alternative embodiments are given in the dependent claims.
A channel in the outlet can be connected to the channel that links the longitudinally running annular space and be formed as a through-going annular space from one or more borings .
The channel can be shaped as an annular space or borings that run through the coupling piece, and the mouth of the channel can comprise one or more gaskets that lie against the outer pipe and one or more gaskets that lie against the inner pipe.
Said annular space can be braced by one or more support points .
The boring for taking out the fuel gas in the inner pipe can run through one of said support points and through the outlet .
In a further variant of the invention the coupling piece on one or both sides can be fitted with a removable coupling flange for connecting and disconnecting a pipe section. The coupling flange can comprise one or more channels to link the longitudinally running annular space between respective sections. Furthermore, the coupling flange can comprise one or more channels that are
connected with the channel of the coupling piece.
Correspondingly, the mouth of the channel can comprise one or more gaskets that lie against the outer pipe and one or more gaskets that lie against the inner pipe.
In a further variant of the invention a pipe for the supply of a pre-chamber gas to the cylinder units of the engine can be arranged inside the inner pipe. Gas from the pipe can flow through a boring in an outlet in the
coupling piece and to the cylinder unit of the engine.
Furthermore, an annular space channel or boring in the outlet can be connected to the first channel.
The coupling piece can comprise an internally open
protrusion to which the pipe for the pre-chamber gas is arranged in. The pipe can be divided into sections that, in the main, correspond to said sections between the cylinder units, and the protrusion can comprise gaskets to receive respective sections.
For all variants the inner pipe at the end of a section can extend further out than the outer pipe, whereby the outwardly extending end of the inner pipe is set up to close between the channel in the coupling piece and the internal run for the fuel gas. Furthermore, the coupling
piece can be cast in one piece, and comprise a fastening bracket for the pipes.
The invention shall now be described in more detail with the help of the enclosed figures, in which:
Figures 1 and 2 show an outline of several pipe sections composed of coupling pieces according to the invention .
Figure 3 shows a section along A-A in figure 1.
Figures 4 and 5 show a section along B-B and C-C, respectively, in figure 3.
Figure 6 shows a section along D-D in figure 5.
Figure 7 shows a section of an alternative coupling flange for the coupling piece according to the invention.
Figure 8 shows a section along A-A in figure 7.
Figures 9 and 10 show an outline of several pipe sections composed of coupling pieces according to a further variant of the invention.
Figure 11 shows a section along A-A in figure 9.
Figures 12 and 13 show a section along B-B and C-C, respectively, in figure 10.
Figure 14 shows a section along D-D in figure 13.
Figure 15 shows a section along E-E in figure 10. A gas engine is regarded to be known to a person skilled in the arts and is therefore not explained further in the application. Essential aspects and technical features in connection with the present invention of a gas engine are explained in more detail below. Furthermore, it shall be mentioned that although the expression gas engine is used, this does not necessarily mean that the present gas supply system is only directed towards a free standing gas engine but can also be used on an engine set up to be both gas driven and be driven by other fuel types, i.e. a so called
dual fuel engine, as the gas supply system will be alike, regardless .
As the figures 1-3 show, the present gas supply system comprises several sections 12 of double-walled pipes 10, where the sections are linked together with the help of respective coupling pieces 14. The double-walled pipe 10 comprises an internally open pipe 10b with an internal boring 28 for the fuel gas that is to be supplied to the cylinder units of the engine. An outer pipe 10a is
arranged around the inner pipe 10b so that it forms a longitudinally running annular space. As mentioned
previously, the annular space is used to detect any leaks from the inner pipe, for example, by a through-flow of air with a gas sensor in the system, or a pressurised inert gas system.
From prior art the pipe for the supply of fuel gas
typically runs a whole length of the engine block and is fastened with several brackets, normally adjoining the protrusions of the cylinder units. In the present
invention the double-walled pipe 10 is divided in sections 12 and joined with the help of several coupling pieces 14. The length of each section 12 is adapted to the distance between the cylinder units and the breadth of the coupling piece. The advantage with the present invention is that one avoids the use of welding as the pipe sections will be simple pieces of pipe with no welds. Furthermore, the coupling piece can be cast in one body and formed so that the annular space between the inner and the outer pipe is carried through to the next section. Another advantage is that the coupling piece can also be used as a fastening bracket for the double-walled pipe 10. An example of a fastening bracket 50 is shown in figure 2.
The coupling piece 14 shall now be explained in more detail with reference to the figures 3-6, which show different sections of the coupling piece 14. The coupling piece 14 is open internally and comprises a boring 20 to lead the fuel gas from the inner pipe 10b and out through an outlet 22. The gas is then led further through
additional double-walled pipes (not shown) and to the cylinder unit. To bring the annular space further between the outer pipe 10a and the inner pipe 10b the coupling piece 14 is comprised of at least one channel 16 that runs through the coupling piece. The channel 16 is preferably made with an angular space form, but can also be formed in other alternative ways. As the figures show, the coupling piece 14 comprises several support points 26 to strengthen the channel 16 in relation to the inner boring 28. The boring 20 to lead out fuel gas preferably runs through one of these support points 26.
As there is a requirement that the annular space in the double-walled pipe 10 shall also be brought further to the cylinder units the outlet 22 can comprise an annular space-formed channel 18 or one or more borings that run to the through-going channel 16 between the sections 12. The channels 18 can, for example, be four borings in the coupling piece 14. Thus, the annular space-formed channel 18 at the outlet can be brought further through the additional double-walled pipe (not shown) and to the cylinder unit. The inner pipe 10b in the section 12 is preferably longer than the outer pipe 10a. In the fitting of a section 12 in the coupling piece 14 the section is inserted so that the inner pipe 10b ends up at an inner recess, in which one or more gaskets 24 are placed to seal against the pipe 10b. The inner recess and the gaskets 24 lie inside a mouth
opening of the channel 16 so that the outer side of the inner pipe 10b closes between the channel 16 and the inner boring 28 for the fuel gas. Outside the mouth opening of the channel 16 a
corresponding recess and one or more gaskets 24 are provided to seal against the outer pipe 10a. The mouth opening of the channel 16 can be curved such as the figures 3 and 6 show, or alternatively not be curved, and thereby connect the annular space in the double-walled pipe 10 to the preferably annular space-formed channel 16 in the coupling piece 14 and further to the next section 12. The gaskets 24 that can be used are, in the main, standard gaskets and are not explained in more detail.
With the use of the sections 12 and the coupling pieces 14 according to the invention a solution is provided that makes it possible to dismantle the double-walled pipe 10 such that a section 12 can be replaced in case of faults. However, it can be difficult to replace one section at a time, other than the end sections, as the sections lie against each other and are inserted into the coupling pieces. One solution to this problem is the use of a removable coupling flange. The figures 7 and 8 show a coupling flange 30 according to the invention. The flange 30 can be fitted to the coupling piece 14 on one or both sides, but normally it is sufficient with a flange on one side.
As the figures show the flange 30 is internally open and comprises an outer annular space-formed channel 16a which corresponds to, and is connected to, the channel 16 in the coupling piece 14. The mouth opening of the channel 16a
and the gaskets are correspondingly formed to the
description above so that the fastening of a section 12 is carried out in the same way. The flange 30 can be fitted to the coupling piece 14 in a known way with the help of bolts 32 that are screwed in, or fastened in any other known way. Gaskets can be arranged between the flange 30 and the coupling piece 14. It can also be considered as an alternative to use two flanges for the coupling together of sections 12, and two flanges put together can then replace one coupling flange and provide the same form and function .
As mentioned previously, a gas engine normally has, in addition to the pipe 10 for the fuel gas, a pipe along the engine for the pre-chamber gas. This pre-chamber gas pipe has the same requirements for a double wall and also runs to the cylinder units of the engine. A further variant of the invention is shown in the figures 9 to 15 and shows a solution where a pre-chamber gas pipe 40 is placed inside the double-walled pipe 10 for the fuel gas, such as shown in figure 11. With this solution there will be no
requirement that the pre-chamber gas pipe shall have a double wall, as the double-walled pipe 10 for fuel gas will take care of this.
The pre-chamber gas pipe 40 is correspondingly divided into sections as described above and is fitted, in the main, in the same way. For that reason the coupling piece 14 is fitted with an internally open protrusion or bead 44 which the sections of the pre-chamber gas pipe 40 are fitted to. In a similar way the protrusion 44 can comprise gaskets .
To distribute the pre-chamber gas to the cylinder units the coupling piece 14 comprises a second outlet 42, and as
in the embodiment shown, is mounted 90° displaced in relation to the first outlet 22 for the fuel gas. A boring 48 for the pre-chamber gas runs from the protrusion 44, and the pre-chamber gas pipe 40, and out through the outlet 42. Correspondingly, the boring 48 can run through one of the support points 26.
As mentioned, it is a requirement that the annular space shall also be carried further to the cylinder units, and the second outlet 42 can therefore comprise an annular space-formed channel 46 or one or more borings that run to the through-going channel 16 between the sections 12.
Thus, the annular space-formed channel 46 in the outlet 42 can run further through an additional double-walled pipe (not shown) and to the cylinder units.