Powertrain provided with optimized LPG injection system

Abstract

The invention relates to a powertrain (1) with indirect LPG injection, comprising a cylinder crankcase (2) on which is mounted a cylinder head (3) comprising at least two intake ducts (4) each leading into a cylinder (8); the powertrain comprises at least two LPG intake manifolds leading into an intake duct (4). According to the invention, the free end of each intake manifold (25, 26, 27, 28, 29) is placed within the intake duct (4) through which LPG is released, and the free end comprises dispersion means (30, 35, 39) for releasing LPG within a larger area of the intake duct (4), the size of which is larger than the size of the cross-section of the intake manifold (25, 26, 27, 28, 29).

Description

[0001] The present invention relates to a powertrain equipped with an optimized LPG gas injection system (LPG is an acronym for Liquified Petroleum Gas).

[0002] More particularly, the present invention relates to a powertrain of a vehicle with indirect LPG gas injection, mainly comprising a spark-ignition engine of the supercharged or naturally aspirated type. The powertrain comprises a cylinder block on which a cylinder head is mounted, the cylinder head having formed therein intake ducts leading to the cylinders. The cylinder head has a so-called "intake" face on which an intake manifold is fixed for directing air and / or gas to the intake ducts formed in the cylinder head and connected to the cylinders, and a so-called "exhaust" face on which an exhaust manifold is fixed for recovering the combustion exhaust gases produced in the cylinders of the engine. The intake air and / or gas is directed to the intake manifold, before being compressed when passing through a compressor, which can constitute the compression stage of a turbocharger for example, when the engine is of the supercharged type.

[0003] To improve the efficiency and performance of the powertrain, the compressed intake air needs to be cooled before entering the cylinders of the engine. Therefore, in the intake circuit, a cooling stage is installed upstream of the cylinder head, taking into account the direction of flow of the intake air. The cooling stage comprises for example a W-CAC type (Water Charged Air Cooler) gas / water heat exchanger through which the hot compressed air passes, transferring part of its heat to water or coolant. The heat exchanger is placed in a housing which extends downstream taking into account the direction of flow of the intake air, with a fixing flange forming a chamber with the recesses of the cylinder head for example. The chamber constitutes a plenum of the intake manifold.

[0004] The powertrain with indirect LPG gas injection comprises an LPG gas intake duct in the intake circuit. The injection is usually performed in the intake duct formed in the cylinder head upstream of the cylinders. Therefore, the LPG gas injection duct is drilled from the intake face of the cylinder head, opening obliquely into the intake passage. Thus, the LPG gas is mixed with the intake air before being introduced into the cylinder, the introduction being controlled by the intake valve. Each cylinder is defined by a cylindrical side wall, a piston and a lower wall of the cylinder head.

[0005] The FR-A1-3112575 publication discloses a gas injection rail carrying at least one tubular metal sleeve adapted to contain a fuel and to supply a fuel injector, more particularly of the LPG gas type. The liquid gas is contained in a tank and is sent to a pressure regulator. It is then delivered to the intake of the engine through the injection rail connected to the injectors, the injection end of each injector opening into an intake passage formed in the hot engine cylinder head. However, the injection end is not specifically designed to precisely direct the LPG gas into the intake duct formed in the cylinder head.

[0006] The power assembly of the invention has an indirect LPG gas injection system in the intake ducts located upstream of the cylinders, which comprises a precisely controlled guide.

[0007] The subject of the invention is a power assembly with indirect LPG gas injection, comprising: a cylinder block on which a cylinder head is mounted; said cylinder head comprising at least two intake ducts, each intake duct opening into a cylinder and serving to supply LPG gas to said cylinder; an intake manifold located upstream of said intake ducts and resting against the cylinder block; and an LPG gas supply circuit comprising a rail provided with at least two injectors, each injector extending by means of a tube which is fixed to the intake manifold and opens into the intake duct.

[0008] According to the invention, the free end of each tube for injecting LPG gas is placed in the intake duct, the free end comprising a dispersion device to enable the LPG gas to be injected in the enlarged area of the intake duct, the dimensions of which are greater than the cross-sectional dimensions of the tube. Such a dispersion device aims to eliminate certain angular dispersion phenomena associated with the structure of the tube and its mounting on the intake manifold. Generally, these tubes are in a curved form and can therefore inject the LPG gas with a certain dispersion into the intake duct. The LPG gas injected by the tube is no longer injected in the form of a directed jet, but in the form of a dispersed and therefore wider jet, which makes it possible to homogenize the spatial distribution of the LPG gas flow in the intake duct. Since the dispersion device is placed at the end of each tube, the LPG gas will enter the cylinder more efficiently, thus improving the efficiency and performance of the power assembly. The power assembly according to the invention comprises an intake circuit which can comprise a compressor and means for cooling the compressed air. The intake manifold can deliver the compressed and cooled air to the cylinders of the power assembly via the intake ducts. The LPG gas is injected into the intake ducts simultaneously with the air, the LPG gas coming from a gas circuit parallel to the air circuit passing through the supply ducts. The tubes are rigid, preferably made of steel. The air / LPG gas mixture entering each cylinder is controlled by at least one intake valve.

[0009] According to a particularly advantageous feature of the invention, each intake duct ends in two distinct and separate intake subducts; the free end of each tube is placed in the intake duct in the upstream region of said two intake subducts and in the central region of said intake duct, to enable the dispersion device to supply LPG gas to said two intake subducts. This dispersion device placed at the free end of the tube makes it possible to inject the LPG gas uniformly into said two intake subducts, thus avoiding the accumulation of LPG gas in one of said two intake subducts, which has the significant risk of causing the LPG gas to flow back into the intake duct.

[0010] According to a possible feature of the application, the dispersion device is a piece fixed to the free end of each tube and comprises a main channel and two secondary channels in fluid communication with the main channel, each secondary channel being intended to supply a specific intake sub-pipe with LPG gas. The main channel is intended to extend the tube, both secondary channels originating from the main channel and being oriented so that they can supply both sub-pipes uniformly. The piece comprising the main channel and the two secondary channels acts as a relay piece, making it possible to direct and orient the flow of LPG gas emitted by the tube without affecting the flow rate of the gas. The two secondary channels can be curved or rectilinear. They can also have the same or different cross sections. Preferably, the main channel and the two secondary channels are cylindrical. They can:

[0011] - be implemented by different sub-pipes branching off from the tube, or

[0012] - be hollowed out in a solid piece, in which case the piece corresponds to a LPG gas dispensing nozzle.

[0013] According to a possible feature of the application, the main channel is provided on a continuous portion of the tube, the two secondary channels originating from the main channel while being oriented towards the two sub-pipes of the intake pipe. The main channel is upstream of the two secondary channels, the term "upstream" being used relative to the direction of flow of the LPG gas in the tube. In other words, the LPG gas flows through the main channel first, then enters the two secondary channels. Thus, the flow of gas reaching the main channel is divided into two distinct flows by the presence of the two secondary channels.

[0014] According to a possible feature of the application, the two secondary channels extend from the main channel while diverging from each other. In this way, the two secondary channels are not parallel to each other and each points towards a specific intake sub-pipe. In other words, one secondary channel points towards one intake sub-pipe and the other secondary channel points towards the other intake sub-pipe.

[0015] According to a possible feature of the application, the two secondary channels form an angle between them, the angle being between 30° and 70°. The angle depends in particular on the relative position of the two intake sub-pipes with respect to each other.

[0016] According to a possible feature of the application, the angle formed between the two secondary channels is equal to 50°.

[0017] According to a possible feature of the application, the two secondary channels each have a constant cross section, and the cross section of one secondary channel is different from the cross section of the other secondary channel.

[0018] According to a possible feature of the application, each tube has a straight section at the end of which the dispersion device is fixed, the length of the straight section being comprised between 5 and 15 mm. This straight section allows the homogenization of the gas flow in the tube just before entering the main channel, then the separation of the flow into two gas flows due to the presence of the two secondary channels of the dispersion device.

[0019] According to an alternative embodiment of the power assembly of the application, the dispersion device is constituted by a conical end section, the inlet end of which has the same cross-section dimensions as the free end of the tube, and at least one dimension of the outlet end of which is greater than the dimension of the inlet end, the inlet end allowing the connection of the conical end section to the tube. Thus, for example, if the inlet end is circular, the outlet end can be, for example, elliptical, with the major axis greater than the diameter of the inlet end and the minor axis less than or equal to this diameter. The outlet end of the conical end section can have any shape, the key being that it promotes the dispersion of the LPG gas in a given direction and in an enlarged area.

[0020] The power assembly of the application has the advantage of being more efficient and of better performance than the prior art power assembly, thanks to the ingenious addition of dispersion devices at the free end of the LPG gas supply tubes of the intake duct. It also has the advantage of providing additional functions thanks to the presence of these dispersion devices, while the overall dimensions remain equivalent to those of the prior art power assembly. Finally, it has the advantage of easily adapting to various variants by simply reconfiguring the LPG gas dispersion devices located at the end of the tubes.

[0021] Three preferred embodiments of the power assembly of the application are described in detail below with reference to the following figures:

[0022] Figure 1 is a partial side view of a prior art power assembly.

[0023] Figure 2 is a perspective view of a prior art power assembly.

[0024] Figure 3 is a side view of a region of a prior art power assembly comprising the intake cooling device.

[0025] Figure 4 is a perspective view of a region of a prior art power assembly, showing the LPG gas supply tubes.

[0026] Figure 5 is a side view of the intake duct of a prior art power assembly, showing the angular dispersion of the LPG gas ejected by the supply tubes in a first direction.

[0027] Figure 6 is a Figure 5 top view of the intake duct shown, showing the angular dispersion of the LPG gas ejected by the supply tubes in a second direction.

[0028] Figure 7Side view of the LPG gas supply pipe for the first embodiment of the power assembly of the application.

[0029] Figure 8 For Figure 7 Front view of the LPG gas supply pipe.

[0030] Figure 9 Perspective view of a zone of the first embodiment of the power assembly of the application, showing the positioning of the LPG gas supply pipe.

[0031] Figure 10 Sectional view of the end of the LPG gas supply pipe in the second embodiment of the power assembly of the application.

[0032] Figure 11 Perspective view of the LPG gas supply pipe for the third embodiment of the power assembly of the application.

[0033] The power assembly 1 of the application is preferably a power assembly with indirect LPG gas injection. In the non-limiting example shown in the attached figures, we assume that the power assembly 1 comprises three supercharged cylinders 8, for example supercharged by means of a turbocharger. However, it could also be a naturally aspirated engine.

[0034] With reference to Figure 1 , Figure 2 and Figure 3 , the power assembly 1 of the application comprises a cylinder block 2 on which a cylinder head 3 is mounted, inside which an intake duct 4 is formed. The cylinder head 3 has:

[0035] - an intake face 5, to which an intake manifold 6 is fixed, which is adapted to direct air and / or LPG gas towards the intake duct 4;

[0036] - an exhaust face 7, to which an exhaust manifold (not shown in the figures) is fixed, which is used to recover the combustion exhaust gases produced by the combustion in the cylinders 8 of the power assembly.

[0037] The intake air and / or gas from the intake circuit of the power assembly 1 is directed towards the intake manifold 6, before which it has been compressed by means of a compressor, which for example can constitute the compression stage of a turbocharger.

[0038] With reference to Figure 3To improve the efficiency and performance of the power assembly 1, the intake air is cooled after being compressed by the compressor and before entering the three cylinders 8 of the power assembly 1. Therefore, a cooling stage 9 is provided in the intake air circuit upstream of the cylinder head 3, according to the direction of flow of the intake air. This cooling stage 9 comprises for example a W-CAC type (Water Charged Air Cooler) air / water heat exchanger through which the hot compressed air transfers part of its heat to water or coolant. This heat exchanger is housed in a housing 10 which extends downstream according to the direction of flow of the intake air, with a fixed flange which forms a chamber with a recess of the cylinder head 3 for example. This chamber constitutes a plenum chamber of the intake manifold.

[0039] The power assembly 1 with indirect LPG gas injection comprises an LPG gas supply circuit which opens into the intake duct 4 of the cylinder head 3 so that the LPG gas mixes with the air before the mixture enters the three cylinders 8.

[0040] With reference to Figure 2 and Figure 4 , the LPG gas supply circuit of the power assembly according to the prior art schematically comprises a distribution rail 11 supplied with LPG gas from a tank, on which three injectors 12, 13, 14 are fixed, each extending through a supply pipe 15, 16, 17. These three supply pipes 15, 16, 17 are supported by an upper edge 18 of the intake manifold 6. Thus, the LPG gas stored in the tank first flows through the distribution rail 11, then through the three injectors 12, 13, 14, and then through the three supply pipes 15, 16, 17. These supply pipes 15, 16, 17 are designed as rigid cylindrical pipes, the cross section of which remains constant over the entire length.

[0041] With reference to Figure 4 and Figure 5 , the supply pipes 15, 16, 17 each open into the upstream region 48 of the intake duct 4. Each supply pipe 15, 16, 17 is curved and ends with a straight pipe section 19 which is inclined with respect to the longitudinal axis of the intake duct 4. This straight pipe section 19 causes the supply pipe 15, 16, 17 to inject the LPG gas into the upstream region 48 of the intake duct 4 in the same direction as the air passing through the intake duct 15, 16, 17, but at an angle thereto. In this way, the mixture of air and LPG gas will enter each cylinder 8 of the power assembly 1.

[0042] With reference to Figure 6The upstream region 48 of each intake duct 4 extends two independent and substantially parallel intake sub-ducts 20, 21, which open into the corresponding cylinder 8 of the power assembly 1. The cross section of each of the two intake sub-ducts 20, 21 is smaller than the cross section of the upstream region 48, which can be the same or different within the same intake duct 4.

[0043] With reference to Figure 1 and Figure 6 , a plurality of passages 22 are formed on the cylinder head 3, so that each passage opens into one end of the intake sub-ducts 20, 21 of each intake duct 4. These passages 22 are designed to each house an intake valve 23, 24 for regulating the flow of the mixture of air and LPG gas circulating in the intake duct 4 towards the corresponding cylinder 8. These intake valves 23, 24 are controlled in such a way that they can only assume two positions: a closed position, in which they prevent the flow of the mixture of air and gas towards the target cylinder 8; and an open position, in which they allow the passage of said mixture. Thus, as shown in Figure 6 , the ends of the two intake sub-ducts 20, 21 of each intake duct 4 are each crossed by a gas valve 23, 24.

[0044] With reference to Figure 5 and Figure 6 , the existing supply pipes 15, 16, 17 have the drawback that the LPG gas they spray has a significant angular dispersion, mainly due to their structure and to the fact that they are fixed to the upper edge 18 of the intake manifold 6. This angular dispersion can reach a range of ± 7° in the vertical plane (as shown in Figure 5 ) and in the horizontal plane (as shown in Figure 6 ). Such angular dispersion is unacceptable, since it can cause the formation of accumulation zones of the mixture of air / LPG gas in the upstream region 48 of the intake duct 4, which can cause the backflow of said mixture towards the intake manifold 6.

[0045] To better control the injection conditions of the LPG gas at the outlet of the supply pipes 15, 16, 17, the power assembly of the present application comprises supply pipes 25, 26, 27, 28, 29, each of which has at the end a dispersion device, so that it is possible to inject the LPG gas into the enlarged region of the intake duct 4.

[0046] With reference to Figure 7 , Figure 8 and Figure 9, According to a first embodiment of the powertrain according to the application, the dispersion means take the form of a nozzle 30 comprising a main central channel 31 and two secondary channels 32, 33 extending from said main central channel 31. The two secondary channels 32, 33 are located downstream of the main central channel 31 and originate from said main central channel 31 and diverge from each other, with respect to the direction of flow of the LPG gas in the supply pipes 25, 26, 27. The main central channel 31 and the two secondary channels 32, 33 are rectilinear, and preferably the two secondary channels 32, 33 form an angle of 50° between them. The nozzle 30 is mounted on the straight end section 34 of each supply pipe 25, 26, 27, so that the main central channel 31 is entirely continuous with the straight end section 34 and so that the two diverging secondary channels 32, 33 are inclined with respect to said straight end section 34. Once the nozzle 30 has been mounted on the supply pipes 25, 26, 27, it makes it possible to inject the LPG gas into the upstream zone 48 of the intake duct 4 in two different directions forming an angle of 50° between them.

[0047] With reference to Figure 10 , According to a second embodiment of the powertrain according to the application, the dispersion means take the form of a nozzle 35 consisting of a solid compact piece in which a main central channel 36 and two secondary channels 37, 38 extending from said main central channel 36 are formed. The two secondary channels 37, 38 are located downstream of the main central channel 36 and originate from said main central channel 36 and diverge from each other, with respect to the direction of flow of the LPG gas in the supply pipe 28. The main central channel 36 and the two secondary channels 37, 38 are rectilinear, and preferably the two secondary channels 37, 38 form an angle of 50° between them. The nozzle 35 is mounted on the supply pipe 28 so that the main central channel 36 is entirely continuous with the supply pipe 28 and so that the two diverging secondary channels 37, 38 are inclined with respect to said supply pipe 28. Once the nozzle 35 has been mounted on the supply pipe 28, it makes it possible to inject the LPG gas into the upstream zone 48 of the intake duct 4 in two different directions forming an angle of 50° between them.

[0048] With reference to Figure 11 , According to a third embodiment of the powertrain according to the application, the dispersion means take the form of a tapered end section 39 of the supply pipe 29. The end section 39 has an inlet end 40 of the same size as the size of the cross section of the supply pipe 29 and an outlet end 41 of which at least one dimension is greater than the size of said inlet end 40. The inlet end 40 is located upstream of the outlet end 41 and makes it possible to connect the tapered end section 39 to the supply pipe 29. Thus, for example, if the inlet end 40 is circular, the outlet end 41 can be, for example, elliptical, with a major axis greater than the diameter of the inlet end 40 and a minor axis less than or equal to this diameter. The outlet end 41 of the tapered end section 39 can be of any shape, the key being that it makes it possible to promote the dispersion of the LPG gas into the corresponding intake duct 4.

[0049] The dispersion devices 30, 35, 39 arranged at the end of each supply pipe 25, 26, 27, 28, 29 allow a better distribution of the LPG gas within each intake duct 4, thus enabling a uniform supply of this gas to the two sub-ducts 20, 21. In this way, it is possible to prevent the formation of accumulation zones of LPG gas in the upstream region 48 of the intake duct 4, which would cause the mixture of air / LPG gas to flow back into said intake duct 4.

Claims

1. Powertrain (1) with indirect LPG gas injection, comprising: Cylinder block (2) on which a cylinder head (3) is mounted, the cylinder head having at least two intake ducts (4) each opening into a cylinder (8) and intended to supply the cylinder (8) with LPG gas; an intake manifold (6) upstream of the intake ducts (4) and resting against the cylinder block (2); and an LPG gas supply circuit comprising a rail (11) provided with at least two injectors (12, 13, 14) each extending a supply pipe (15, 16, 17, 25, 26, 27, 28, 29) fixed to the intake manifold (6) and opening into the intake duct (4); characterized in that the free end of each supply pipe (25, 26, 27, 28, 29) is placed inside the intake duct (4), the LPG gas being injected through the supply pipe; and in that the free end comprises a dispersion device (30, 35, 39) to enable the LPG gas to be injected in an enlarged zone of the intake duct (4), the dimensions of the intake duct being greater than the cross-sectional dimensions of the supply pipe (25, 26, 27, 28, 29).

2. The powertrain of claim 1, wherein, The end of each intake duct (4) is in two distinct and separate intake sub-ducts (20, 21), and the free end of each supply pipe (25, 26, 27, 28, 29) is placed in a zone (48) inside the intake duct (4) upstream of the two intake sub-ducts (20, 21) and in a central zone of the intake duct (4) to enable the dispersion device (30, 35, 39) to supply the two intake sub-ducts (20, 21) with LPG gas.

3. The powertrain of claim 2, wherein, The dispersion device (30, 35) is a component fixed to the free end of each supply pipe (25, 26, 27, 28) and comprises a main channel (31, 36) and two secondary channels (32, 33, 37, 38) in fluid communication with the main channel (31, 36), each of the secondary channels (32, 33, 37, 38) being intended to supply a corresponding intake sub-duct (20, 21) with LPG gas.

4. The powertrain of claim 3, wherein, The main channel (31, 36) is provided to be continuous with the supply pipe (25, 26, 27, 28), and the two secondary channels (32, 33, 37, 38) originate from the main channel (31, 36) while being directed towards the two intake sub-ducts (20, 21) of the intake duct (4).

5. The powertrain of claim 4, wherein, The two secondary channels (32, 33, 37, 38) extend from the main channel (31, 36) and diverge from each other.

6. The powertrain of claim 5, wherein, The angle formed between the two secondary channels (32, 33, 37, 38) is between 30° and 70°.

7. The powertrain of claim 6, wherein, The angle formed between the two secondary channels (32, 33, 37, 38) is 50°.

8. The powertrain of any one of claims 3-7, wherein, The two secondary channels (32, 33, 37, 38) each have a constant cross-section, and the cross-section of one of the secondary channels is different from the cross-section of the other secondary channel (32, 33, 37, 38).

9. The powertrain of any one of claims 3-8, wherein, Each feed pipe (25, 26, 27, 28) has a straight pipe section (34) to which the dispersion device (30, 35) is fixed at the end, and the length of which is 5 mm to 15 mm.

10. The powertrain of claim 1, wherein, The dispersion device is made up of a conical end section (39) having an inlet end (40) of the same size as the size of the cross section of the feed pipe (25, 26, 27, 28) and at least one dimension of an outlet end (41) of which is greater than the size of the inlet end (40), and the inlet end (40) is capable of connecting the conical end section (39) to the feed pipe (25, 26, 27, 28).

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