Patent Application
20220154630
The present invention relates to the field of gas inlet devices for an internal combustion engine. The present invention relates in particular to gas inlet devices capable of generating an aerodynamic movement of gases in the cylinder of the engine.
This type of engine generally comprises at least one cylinder, a piston sliding in this cylinder in a reciprocating rectilinear movement, means for admitting an oxidant, means for exhausting burnt gases, a combustion chamber, and injection means for injecting a fuel.
As is generally acknowledged, when designing an engine, the constraints regarding performance and pollutant emissions are becoming increasingly strict and it is therefore necessary to find novel solutions for increasing the final efficiency of the engine.
Increasing the efficiency of the combustion is therefore a key factor in limiting pollutant emissions for the same or better performance. To do that, it is of the utmost importance that all of the fuel present in the combustion chamber is used by an oxidant comprising for example air at ambient pressure, supercharged air, or a mixture of air (supercharged or otherwise) and of recirculated burnt gases.
Specifically, it is necessary for the carbureted mixture (oxidant/fuel) in the combustion chamber to be as homogeneous as possible.
In addition, in order to ensure good efficiency as well as a good rate of combustion, it is desirable to have a high level of turbulence, and more specifically a high level of turbulent kinetic energy, at the moment of ignition of the carbureted mixture and during the course of the combustion that follows.
This high level of turbulence can be achieved by using specific inlet aerodynamics: swumble. This type of aerodynamics is characterized in that the macroscopic movement of the carbureted mixture is a compound of swirl (a rotary movement of the gases in the cylinder about a vertical cylinder axis) and of tumble (a rotary movement of the gases in the cylinder along a longitudinal engine axis).
Swirl, which is a macroscopic movement of rotation of the carbureted mixture about an axis collinear with the axis of the cylinder, is characterized in that it is maintained well during the course of the inlet process and more specifically during the piston upstroke. This is a macroscopic aerodynamic movement which is generally used for compression-ignition internal combustion engines where there is a good way of homogenizing the carbureted mixture.
Tumble is likewise a macroscopic rotational movement of the carbureted mixture, but about an axis that is, overall, perpendicular to the axis of the cylinder. It has the particular feature of transforming into microscopic aerodynamic movements which create turbulence during the piston upstroke. This is a macroscopic aerodynamic movement which is generally used for controlled-ignition internal combustion engines where there is a good way of obtaining a suitable rate of combustion. Furthermore, this movement is fairly sensitive to the geometry of the combustion chamber and also to the valve-lift law both in terms of its spread and in terms of the maximum height of valve lift.
Using swumble provides the benefit of the advantages of both of the aerodynamic structures detailed hereinabove, and therefore provides the benefit of excellent homogenization and of a better rate of combustion thanks to a higher level of turbulence during the compression phase than is observed with the best current controlled-ignition engines.
Various technical solutions have been developed for achieving these turbulent flows in the cylinder.
A first solution is described notably in U.S. Pat. No. 6,606,975. This solution consists in controlling a flap positioned in the inlet port to generate turbulence. That patent also features the notion of swumble at light load. Such a solution is complex and detrimental to the filling of the cylinder.
A second solution is described notably in U.S. Pat. No. 5,056,486. That solution proposes a definition of asymmetric inlet ports capable of generating complex aerodynamics. However, that solution requires a phase-shifting of the openings of the inlet valves, and proves detrimental at high load.
A third solution is described notably in patent applications DE10128500 and EP1783341. That solution allows complex aerodynamics to be generated using passive or active appendages in the inlet port. In both instances, these appendages limit the filling of the cylinder with gas. In addition, the active appendages require control, making the solution complex.
A fourth solution is described notably in patent applications US 2008/0149063, JP 2010-261314 and US 2012160198. That solution consists in generating aerodynamic movements of the gas in the cylinder using masks positioned at the end of the inlet port. However, in order to obtain a swumble-type aerodynamic movement of the gas, it would appear necessary to use two masks per inlet port, or to use special valve-lift laws, making this solution complex. In addition, the masks used limit the filling of the cylinder with gas.
It is an object of the invention to overcome these disadvantages, by means of an inlet device able, in a simple way, to obtain good engine performance, notably with significant turbulent energy and a stable swumble-type aerodynamic structure of the gas. In order to do that, the present invention relates to a gas inlet device for a cylinder of an internal combustion engine. The gas inlet device comprises an inlet port, an inlet valve, a calibration of the inlet valve, means for forming a tumble-type aerodynamic movement of the gas within the cylinder, and a mask. Furthermore, the intersection between the inlet port and the calibration is along a straight line not parallel to the plane of the firing face. This inclination allows the generation of an aerodynamic movement of the swirl type in the cylinder, which combines with the tumble to form an aerodynamic movement of the swumble type. In addition, the mask is oriented in the same way as the end of the inlet port, encouraging the aerodynamic movement of the gas in the cylinder.
The invention relates to a gas inlet device for a cylinder of an internal combustion engine, said gas inlet device comprising an inlet port, at least one inlet valve positioned within said inlet port, at least one calibration of said inlet valve positioned at one end of said inlet port and facing toward the firing face of said cylinder, means for deflecting said gas to generate an aerodynamic movement of said gas within said cylinder about an axis substantially perpendicular to the axis of said cylinder, at least one mask partially obstructing said end of said inlet port opening into said cylinder, wherein, on the intrados of said inlet port, the intersection between said inlet port and said calibration forms a straight-line segment supported by a rectilinear generatrix forming an angle α of between 5 and 45° with respect to a plane parallel to said firing face of said cylinder and passing through a point of intersection between said inlet port and said calibration. A midplane of said mask forms an angle γ about the axis of said valve with respect to the midplane of said inlet port, such that γ=α+/−5°.
According to one embodiment, the angle γ is defined by γ=α+/−2°, and preferably the angle γ is substantially equal to the angle α.
According to one implementation, said angle α is between 5 and 20°, and preferably between 8 and 15°.
According to one aspect, said means for generating an aerodynamic movement of the gas within said cylinder about an axis substantially perpendicular to the axis of said cylinder consist of the shape of said inlet port, notably by means of a half-pipe shape and/or of a convergence of the bore section of said inlet port, and/or an inclination of said inlet port.
According to one feature, said inlet port comprises two gas outlets leading to said cylinder and two inlet valves.
According to one option, said mask has substantially the shape of a portion of an annulus of which the centre is positioned on the axis of said inlet valve.
Advantageously, said annulus portion extends over an angular range δ of between 150 and 200°, preferably between 160 and 180°, and preferentially substantially 170°.
Advantageously, the height of said mask is between 2 and 4 mm, preferably between 2.8 and 3.2 mm, and is preferentially substantially equal to 3 mm.
As a preference, the fillet radius connecting said mask to said cylinder is between 1 and 3 mm, and is preferentially substantially equal to 2 mm.
Furthermore, the invention relates to an internal combustion engine comprising at least one cylinder provided with at least one inlet device according to one of the preceding features, with at least one exhaust device, and with fuel-injection means.
Other features and advantages of the device according to the invention will become apparent on reading the description below of non-limiting embodiments, with reference to the appended figures described below.
The present invention relates to a gas inlet device for a cylinder of an internal combustion engine.
The gas inlet device comprises:
The lower plane of the cylinder head (of the internal combustion engine) orthogonal to the axis of the cylinder is referred to as the firing face or combustion face. The calibration of the valve is inserted into the lower plane of the cylinder head so as to supply the cylinder with gas.
According to the invention, the inlet device is formed in such a way that, on the intrados of said inlet port, the intersection between the inlet port and the calibration of the valve forms a straight-line segment supported by a rectilinear generatrix forming an angle α of between 5 and 45° with respect to a plane parallel to the firing face and passing through a point of intersection between the inlet port and the calibration of the valve. The lower face of the inlet port (when the inlet port is in its operational position) is referred to as the intrados of the inlet port. Thus, the intersection (which is a straight-line segment) of the lower face of the inlet port with the valve calibration is inclined with respect to a plane parallel to the firing face. This inclination allows the gas entering the calibration and, especially, entering the cylinder to be deflected. This deflecting of the gas forms an aerodynamic movement of the gas within the cylinder in a direction parallel to the axis of the cylinder, in other words a swirl-type aerodynamic movement of the gas. This inclination may translate to a rotation of the inlet port at its end (the end of the inlet port is therefore twisted), which encourages the swirl-type aerodynamic movement of the gas. In addition, this embodiment allows a swirl-type aerodynamic movement to be imparted to the gas without any special appendage of the mask, flap or blade type. In addition, the architecture of these inlet devices imposes no additional constraint regarding installing it in a cylinder head of a single-cylinder or multi-cylinder internal combustion engine.
The inclination at an angle α of between 5 and 45° allows the generation of a swirl-type aerodynamic movement of the gas. Below 5°, the inclination is not sufficient to have a significant influence on the aerodynamic movement of the gas in the cylinder. Above 45°, the geometry of the inlet port is complex and difficult to achieve.
By combining tumble-type and swirl-type aerodynamic movements of the gas, the gas inlet device according to the invention allows a swumble-type aerodynamic movement of the gas in the cylinder, providing the benefits of excellent homogenization and a better rate of combustion thanks to a higher level of turbulence during the compression phase than is observed with the best current controlled-ignition engines.
According to one aspect of the invention, the bore section of the inlet port may have a shape that is substantially rectangular, with rounded corners. In that case, the intersection of the inlet port and the calibration of the valve is formed by four edge corners: one on the intrados, one on the extrados, and two on the lateral sides.
According to one example of this embodiment, the rectangular bore section of the inlet port at the intersection with the valve calibration is inclined with respect to the direction of the firing face. In other words, none of the edge corners of the rectangular bore section is parallel or perpendicular to a plane parallel to the firing face.
According to the invention, a midplane of the mask forms a non-zero angle γ about the axis of the valve with respect to the midplane of the inlet port, such that the angle γ can be defined by the relationship: γ=α+/−5°. In the present application, X+−Y (where X and Y are positive numbers) means a range centred on the value X, which range is between the values X−Y and X+Y (including endpoints). Thus, the mask is oriented in a similar way to the end of the inlet port, thus encouraging the aerodynamic movement of the gas in the cylinder. This approach results in gains in turbulent kinetic energy in the vicinity of top dead centre, and the stability of the structure of the aerodynamic movement of the gas in the cylinder is improved in comparison with a mask-free inlet device provided with means for generating swumble-type aerodynamic movement of the gas. In addition, this arrangement imposes no additional constraint regarding installing it in a cylinder head of the engine, making it possible in a simple way to obtain an aerodynamic movement of the gas in the cylinder. A plane which sections the mask into two identical parts and which contains the axis of the inlet valve is referred to as a midplane of the mask. The midplane of the mask may be its plane of symmetry. A plane which sections the inlet port into two substantially identical parts and which contains the axis of the inlet valve is referred to as a midplane of the inlet port.
According to one implementation of the invention, the angle γ can be defined by γ=α+/−2°. As a preference, the angle γ may be substantially equal to the angle α. These preferred values allow optimization of the gains in turbulent kinetic energy and in stability of the aerodynamic movement of the gas, thanks to greater similarity between the orientation of the mask and the orientation of the end of the inlet port.
The gas is an oxidant or a carbureted mixture (in the case of indirect injection), and may notably comprise air at ambient pressure, supercharged air, a mixture of air (supercharged or otherwise) and of burnt gases.
According to one embodiment of the invention, the angle α may be between 5 and 20°, and preferably between 8 and 15°. These angular ranges allow optimization of the swirl-type aerodynamic movement of the gas, and thus optimization of the swumble-type combined aerodynamic movements of the gas.
According to one implementation of the invention, the gas-deflecting means consist solely of the shape of the inlet port. Thus, there is no active or passive element to impede the passage of the gas through the inlet port.
According to a first exemplary embodiment, the gas-deflecting means may comprise a half-pipe shape on the lower profile of the inlet port. This half-pipe shape may be obtained by varying the concavity of the lower profile of the inlet port. The half-pipe shape encourages separation of the flow of gas from the walls of the inlet port and directs the flow toward the upper part of the inlet port and therefore toward the upper part of the cylinder so as to maximize the tumble-type aerodynamic movement of the gas.
According to a second exemplary embodiment (which may be combined with the first exemplary embodiment), the gas-deflecting means may comprise a convergence of the bore section in the vicinity of the calibration of the valve. In other words, the bore section of the inlet port decreases toward its end closest to the calibration of the valve. This convergence causes an acceleration of the gas flow which is beneficial for the filling with and aerodynamic movement of the gas.
According to a third exemplary embodiment (which may be combined with the first and/or second exemplary embodiment), the gas-deflecting means may comprise an inclination of the inlet port. This inclination of the inlet port may be defined by an angle of the tangent to the point of intersection of the inlet port with the calibration of between 0 and 45°. This inclination may be coupled to the gradient of the upper part of the combustion chamber of the cylinder. The inclination of the inlet port enables the flow of gas entering the cylinder to be inclined in order to form a tumble-type aerodynamic movement of the gas. For example, optimization of the tumble-type aerodynamic movement of the gas may be achieved by tangency between the angle of the inlet port and the angle of the gradient of the upper part of the combustion chamber.
According to one embodiment of the invention, the mask may have substantially the shape of a portion of an annulus of which the centre is situated on the axis of the inlet valve. This shape provides a compromise between the filling of the cylinder and the aerodynamic movement of the gas in the cylinder. By masking part of the bore section of the inlet port for low inlet-valve valve lift, the aerodynamic movement of the gas in the cylinder is initiated without excessively penalizing the filling, because the valve lift is low. Once the inlet-valve valve lift is greater, the mask is no longer operative and there is therefore maximum filling with an already-initiated aerodynamic movement of the gas in the cylinder which can then develop. Advantageously, the inside diameter of the annulus may correspond substantially to the diameter of the calibration of the valve. Advantageously, the annulus portion may extend over an angular range of between 150 and 200°, preferably between 160 and 180°, and may preferentially be equal to 170°. These angular ranges allow the aerodynamic movement of the gas leaving the inlet port to be oriented so as to optimize the aerodynamic movement of the gas in the cylinder.
According to one embodiment option of the invention, the height of the mask may be between 2 and 4 mm, preferably between 2.8 and 3.2 mm, and may preferentially be substantially equal to 3 mm. These ranges of values allow a good compromise for initiating the aerodynamic movement of the gas in the cylinder without penalizing the filling of the cylinder.
Advantageously, the fillet radius connecting the mask to the roof of the cylinder may be between 1 and 3 mm, and may be substantially equal to 2 mm. This then avoids isolated zones in the combustion chamber (cylinder). In addition, angular shapes would be disadvantageous to combustion in the cylinder.
According to one aspect of the invention, the gas inlet device may be of siamese type. In other words, the inlet port has a single inlet and two outlets leading into the cylinder, each of the outlets comprising an inlet valve and an inlet valve calibration. Each outlet has the angular features defined to form a swumble-type aerodynamic movement of the gas. This type of inlet device, suitable for cylinders provided with two inlet valves, simplifies the design of the intake plenum (the intake plenum is the volume upstream of the inlet ports). In addition, each outlet has a mask, oriented according to the features defined in the present application.
The inlet device 1 further comprises means for deflecting the gas to generate an aerodynamic movement of the gas within the cylinder in a direction perpendicular to the axis of the cylinder (tumble-type aerodynamic movement of the gas). These gas-deflecting means comprise a convergence 8 of the bore section of the inlet port 5 in the vicinity of the calibration 6 of the valve. This convergence 8 corresponds to a reduction in the bore section in the vicinity of the valve calibration 6. In addition, the gas-deflecting means comprise a half-pipe 9 formed on the lower profile of the inlet port 5 by a variation in the concavity of the lower profile of the inlet port 5. Furthermore, the gas-deflecting means comprise the inclination of the inlet port 5 which is defined by the tangent to the point of intersection 7 of the inlet port 5 with the calibration 6, and with respect to a direction AA. This figure features a straight line FF belonging to the plane of the firing face, and the direction AA is parallel to the straight line FF.
Furthermore, the inlet device 1 comprises a mask 10. The mask 10 is placed in the valve calibration 6 to partially obstruct the outlet 3 of the inlet port 5. The mask 10 is defined by a height H and by a radius of curvature R with respect to the roof of the chamber of the cylinder. For the embodiment illustrated, the height H may be equal to 3 mm and the connecting fillet radius R may be equal to 2 mm.
In these figures, the straight line FF belongs to the plane of the firing face (which face is defined by the cylinder which has not been depicted), and the direction F′F′ is a straight line belonging to a plane parallel to the firing face FF passing through a point of intersection between the inlet port 5 and the calibration 6 of the inlet valve.
According to the prior art illustrated in the figure on the left, the intersection 7 between the inlet port 5 and the calibration 6 of the inlet valve is a straight-line segment coincident with the straight line F′F′.
By contrast, according to the invention illustrated in the figure on the right, the intersection 7 between the inlet port 5 and the calibration 6 of the inlet valve forms a straight-line segment supported by a rectilinear generatrix of axis YY inclined by an angle α with respect to the plane F′F′. This angle α is between 5 and 45°. It may be seen in the figure on the right that this inclination leads, in the vicinity of the connecting fillet, to a slight rotation of the inlet port 5, which has a substantially rectangular bore section. According to the invention, the angle α is connected to the angle γ illustrated in
The invention also relates to an assembly comprising a cylinder of an internal combustion engine and an inlet device according to one of the variants or combinations of variants described hereinabove.
In addition, the present invention relates to an internal combustion engine comprising at least one cylinder, each cylinder being provided:
According to one embodiment, the fuel-injection means may be direct-injection means, which means to say that the fuel-injection means are positioned directly in the cylinder.
Alternatively, the fuel-injection means may be indirect-injection means, which means to say that the fuel-injection means are positioned in the inlet device.
According to one implementation of the invention, the internal combustion engine is a controlled-ignition engine. In that case, the engine also comprises at least one spark plug to initiate combustion of the mixture of gas and fuel.
Alternatively, the internal combustion engine is a compression-ignition engine. In that case, the engine does not comprise any spark plug to initiate combustion of the mixture of gas and fuel.
The internal combustion engine may comprise a plurality of cylinders, notably 3, 4, 5 or 6 cylinders.
As a preference, the combustion engine may be an engine that has four valves per cylinder (two inlet valves and two exhaust valves).
According to one aspect of the invention, when the cylinders comprise two inlet ports, these two ports may be identical and parallel with respect to the midplane of the combustion chamber.
As a variant, the cylinders may be supplied with gas by a Siamese inlet device.
Furthermore, the present invention relates to the use of an internal combustion engine according to one of the variants or combinations of variants described hereinabove, operating on a Miller cycle or on an Atkinson cycle.
The Miller cycle is a thermodynamic cycle characterized by closure of the inlet valve or valves before the piston reaches bottom dead centre during the induction stroke. That allows greater amounts of work to be recovered, as well as allowing cooling of the admitted charge. The inlet device according to the invention is particularly suited to use in the so-called Miller cycle over an extended range of operation thanks to the generation of a swumble-type aerodynamic movement of the gas.
The Atkinson cycle is the standard thermodynamic cycle used in variable combustion engines.
The internal combustion engine according to the invention, which can be used in the field of mobile applications, such as the fields of road, maritime or aeronautical transport, or in the field of static installations, such as an electricity generator set.
It goes without saying that the invention is not limited to just these embodiments of the inlet device which have been described above by way of example, but rather encompasses all variants.
The features and advantages of the method according to the invention will become more clearly apparent on reading the following comparative example.
In this comparative example, a comparison is made between two inlet devices with identical means for generating a swumble-type aerodynamic movement and with masks in the shape of an annulus portion extending over an angular portion of 170°. In the first inlet device compared, the mask is oriented in accordance with the prior art (
| Number | Date | Country | Kind |
|---|---|---|---|
| 1904025 | Apr 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/058714 | 3/27/2020 | WO | 00 |
