EP3140528A2

EP3140528A2 - Two-stroke combustion engine of an automotive vehicle with twisted intake ports

Info

Publication number: EP3140528A2
Application number: EP15788646.6A
Authority: EP
Inventors: Laurent Delahaye; Frédéric JUSTET; Pascal Tribotte
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2014-05-05
Filing date: 2015-03-26
Publication date: 2017-03-15
Also published as: WO2015170020A2; WO2015170020A3; FR3020656B1; FR3020657A1; FR3020656A1

Abstract

The invention relates to a two-stroke thermal engine comprising at least one axial cylinder (12) having a bore (14) which slidably receives at least one piston (16) and has a plurality of lower peripheral ports (34) capable of being opened or closed by the moving piston (16), which ports are substantially hexahedral in shape, are each defined in the peripheral wall (30) by quadrilateral surfaces (36, 38, 58, 60), comprising upper surfaces (36, 38) which are defined by edges (40, 42, 46, 48), referred to as gas directing edges, characterised in that the gas directing edges (40, 42) of the upper surface (36) form angles (α4ο, α42) with a radial direction (R), which angles are oriented in a first direction and are within a first angular range, and in that the gas directing edges (46, 48) of the lower surface form angles (α46, α4β) with the radial direction (R), which angles are oriented in a second direction, which is opposite the first, and are within a second angular range.

Description

"Two-stroke automotive engine with twisted intake lights"

The invention relates to a two-stroke engine of a motor vehicle.

The invention more particularly relates to a two-stroke engine of a motor vehicle, comprising at least one axial cylinder comprising a bore which slidably receives at least one piston which defines with the walls of said bore a combustion chamber, said cylinder having a wall of substantially transverse upper end which receives at least one exhaust valve and at least one fuel injector, and a peripheral wall which has a lower part in which are arranged a plurality of peripheral lights, which open into the bore and are suitable to be opened or closed by the piston in motion to allow or prohibit the admission of air into the combustion chamber, each light being of substantially hexahedral shape, and being delimited in the peripheral wall by quadrilateral shaped faces which comprise at least one less one upper face and one lower face extending substantially perpendicular to the axial direction of the bore, whose so-called gas orientation edges extend along the thickness of the wall of the cylinder.

Many examples of motors of this type are known. In such a two-stroke engine, of the so-called "equi-current" or "uniflow" type, the flue gases from the combustion chamber are discharged from said chamber via at least one valve, or preferentially via two valves which are arranged in the substantially transverse upper end wall of the combustion chamber. When the lights at the bottom of the cylinder open following the descent of the piston, the intake air is introduced into the chamber by the lights and it just push the burnt gases to evacuate through said valves.

During this phase, the flow of the intake air follows a swirling aerodynamic profile which is also known as "swirl", and which is determined by an angle of entry which is formed between the general direction of lights and the radial direction.

When the piston rises, it gradually closes the lights. The exhaust also closes. The injection is controlled at this time.

Depending on the intensity of the swirling flow, the fuel jet injected can be strongly deflected.

Thus, if the angle of entry of the lights is too small, which corresponds to a vortex movement of reduced intensity, the intake air enters substantially radially in the cylinder and is distributed in a mushroom shape leaving gas burned at the periphery. This does not allow a good scan of the cylinder. The jet of fuel, when it extends substantially along the axis of the combustion chamber and concentrates around this axis without integrating homogeneously to the intake air.

Conversely, if the angle of entry of the lights is too high, that is to say, if one directs too tangentially the lights, the swirling flow or "swirl" is too violent the air of admission is distributes in a bowl shape inside the cylinder. The jet of fuel can under certain conditions touch the wall of the cylinder, which is undesirable because it then occurs a wetting phenomenon of the wall which opposes a good vaporization of the fuel.

One solution is to modulate the intensity of the swirling flow by twisting the lights, the intensity swirling flow being determined by the progressive closing of the light by the piston during its ascent. For this purpose, the invention proposes a motor of the type described above, characterized in that the direction of orientation of the upper face forms with the radial direction an angle which is oriented in a first determined direction, and in that the direction of orientation of the lower face forms with the radial direction an angle which is oriented according to a second determined direction opposite to the first determined direction, to provide a twisted light adapted to steer the intake air differently as and when as the piston rises, to homogenize the mixture.

Thus, the gas orientation edges of the upper face form with the radial direction angles which are oriented in a first determined direction and which are each within a first predetermined angular range, and in that the orientation edges of gas of the lower face form with the radial direction angles which are oriented in a second determined direction opposite to the first determined direction, and which are each included in a second predetermined angular range, to provide a twisted light adapted to direct the air d admission differently as the descent and the rise of the piston, in order to homogenize the mixture.

According to other features of the invention:

the angle according to the first direction of orientation is comprised in a first angular range determined between 25 and 45 degrees,

the angles in the second direction of orientation are in a given angular range between 10 and 35 degrees in the second determined direction opposite to the first determined direction,

- Thus, the first angular range is between 25 and 45 degrees in the first determined direction and the second angular range is between 10 and 35 degrees in the second determined direction opposite the first determined direction, the upper face is concave facing the lower face,

the lower face is convex facing the upper face,

the upper and lower faces are substantially planar,

the upper / lower face is slightly inclined relative to the plane orthogonal to the axis of the cylinder by an angle of less than 10 °,

the upper face and the lower face are joined together by means of a lateral face extending substantially along the axis of the cylinder and the upper / lower face is joined to the lateral face by a fillet,

- the radius of the fillet is between 1mm and 3mm,

the distance between the lower face and the upper face is between 5 and 20% of the stroke of the piston.

the angle of orientation of at least one edge of the upper face of the light and the angle of orientation of the edge facing the associated lower face form a determined minimum angular difference which is able to conform to the substantially vertical side face of the light which is delimited by said two edges in a portion of divergent conduit oriented towards the inside of the cylinder.

Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 is a perspective ghost view of a cylinder of an engine according to the state of the art;

FIG. 2 is a phantom view of the fuel injection into a cylinder of the engine of FIG. 1 subjected to a reduced vortex flow; FIG. 3 is a phantom view of the fuel injection into a cylinder of the engine of FIG. 1 subjected to a high swirling flow;

FIG. 4 is a phantom view of the cylinder of the engine of FIG. 1 comprising lights whose entry angle is reduced;

FIG. 5 is a phantom view of the cylinder of the engine of FIG. 1 comprising lights whose entrance angle is high;

- Figure 6 is a detailed perspective view of the lights of a cylinder according to a state of the art;

FIG. 7 is a detailed perspective view of the lights of a cylinder according to the invention

- Figure 8 is a sectional view of the upper part of the lights along the line 8-8 of Figure 7;

- Figure 9 is a sectional view of the lower part of the lights along the line 9-9 of Figure 7;

FIG. 10 is a phantom view of the distribution of the supply air in a cylinder of the engine according to the invention;

FIG. 11 is a phantom view of the injection of fuel into a cylinder of the engine according to the invention;

In the following description, like reference numerals designate like parts or having similar functions.

FIG. 1 shows a part 10 of a two-stroke engine of a motor vehicle produced according to a state of the art.

In known manner, the portion 10 of the heat engine comprises at least one axial cylinder 12 having a bore 14 which slidably receives at least one piston 16 which is visible here an upper face 18.

The piston 16 delimits with the walls of the bore 14 a combustion chamber 20 in the cylinder 12. In known manner, the cylinder 12 has a substantially transverse upper end wall 22 which receives at least one seat 24 of a valve (not shown), a bore 26 for an injector (not shown) and a thread of a candle ignition 28.

Furthermore, the bore 14 has a peripheral wall 30 in a lower portion 32 of which are arranged a plurality of peripheral lights 34 which open into the bore 14 and which can be opened or closed by the piston 16 in function its upward or downward position to allow or prohibit the admission of air into the combustion chamber of the cylinder 12 through said slots 34.

Each lumen 34 is of hexahedral shape and is delimited in the peripheral wall of the cylinder 12 by faces which are substantially quadrilateral shaped.

Thus, the faces comprise at least one upper face 36 and one lower face 38 which extend substantially perpendicular to the axial direction "A" of the bore 14, and corresponding edges 40, 42 of the upper face 36 and 44 , 46 of the lower face 38 extend along the thickness of the wall of the cylinder 12, as shown in FIG.

In known manner, it is possible to envisage several conformations of the hexahedral lights 34.

By convention, the hexahedral lights 34 are oriented relative to a radial direction "R" which extends from the axis "A" of the cylinder 14.

As shown in Figures 6, 8 and 9, the radial direction R extends radially from the axis A of the cylinder and passes through the hexahedral light through the center of the outlet of said light in the bore 14 of the cylinder.

Indeed, it is conventionally allowed to orient the hexahedral lights 34 at an angle "a" determined by relative to the radial direction "R" so as to cause, during the admission of air through said windows 34, a vortex movement also known under the name "Swirl", the intensity of which depends on the angle determined. This vortex flow is intended to drive the burnt gases in the combustion chamber 20 towards the seats 24 of the valves to allow the escape of said flue gas.

When the piston 16 is sufficiently raised and closed the peripheral lights 34, the compression of the air previously admitted into the combustion chamber 20 begins.

Simultaneously, during this compression phase occurs an injection of fuel from the injector associated with the piercing 26, which makes it possible to form a fuel mixture inside the combustion chamber by mixing the injected fuel with the fuel. air admitted.

The injection of the fuel mixture occurs, therefore, in a flow of air subjected to vortex movement or "Swirl".

The quality of the injection directly depends on the intensity of the vortex movement of the air within the combustion chamber 20.

Thus, as illustrated in FIG. 2, a jet of fuel 50 pulverized in a vortex movement of reduced intensity associated with a reduced "a" angle extends substantially in the axial direction "A" in a central zone of the chamber. 20 of combustion.

In contrast, a fuel jet 51 sprayed in a high intensity swirling motion associated with a high angle "α" is generally subject to a deflection which tends to contact the walls 30 of the bore 14, thereby which is detrimental to the quality of the fuel mixture.

Indeed, there is then a wetting phenomenon of the wall 30 of the bore 14, which causes the condensation of fuel droplets on the walls 30 of the bore 14 and thus a change in the stoichiometric proportions of the mixture which adversely affect its good inflammation.

Furthermore, the orientation of the lights 34 also directly affects the distribution of the fresh air that is admitted into the combustion chamber 20.

As illustrated in Figure 4, for a reduced angle value "a", the admission of air through the slots 34 is substantially radially and results in a formation within the chamber 20, of air in the form of a mushroom 52.

On the contrary, when the angle "a" is relatively high as shown in Figure 5, which corresponds to a vortex movement of high intensity, the intake air is distributed in the form of a bowl 54.

Thus, the angle "a", is more or less important depending on the intensity of the swirling motion that it is desired to create inside the chamber 20.

However, none of the two previously mentioned configurations makes it possible to obtain an optimal distribution of the intake air within the chamber 20.

The invention overcomes this disadvantage by providing lights 34 whose orientation is variable.

The lights 34 known in the state of the art comprise edges 40, 42, 46, 48 whose angle "a" orientation is substantially identical from one edge to the other.

The orientation of a light 34 can be differentially characterized by the angle formed by the direction of orientation of each upper face 36 or lower 38 with the radial direction "R".

Thus, it is possible to differentially characterize the orientation of a light 34 by the angle formed between the edges 40, 42 of the upper face 36 or the edges 46, 48 of the face lower 38 with the radial direction "R" on a plane orthogonal to the axis A of the cylinder, as shown in Figures 8 and 9.

The invention proposes lights 34 whose direction of orientation of the upper face 36 with respect to the radial direction "R" is different from that which forms the direction of orientation of the lower face with the radial direction "R", to provide a twisted light 34 adapted to steer the intake air differently as the rise of the piston 16.

Thus, the invention proposes lights 34 whose orientation is variable, that is to say, said lights 34 said twisted angles "cuo", " ₄ 2 ^M orientation of the edges 40, 42 of the upper face 36 and angles "α ₄ 6 ^Μ ," had "edges 46, 48 of the lower face 38 are different so as to channel differently the intake air during admission, the piston 16 closing engine progressively during its ascent said lights 34 and thus promoting the distribution of intake air and its orientation differentially depending on the portion of the light 34 through which the air flow.

For this purpose, the invention proposes a motor of the type described above, characterized in that the direction of orientation of the upper face 36 forms with the radial direction "R" an angle α ₄ ο, α ₄ 2 which is oriented according to a first predetermined direction, and in that the orientation direction of the lower face 38 forms with the radial direction "R" at an angle α ₄ 6, ₄ α 8, which is oriented along a second predetermined direction opposite to the first predetermined direction, to provide a twisted light 34 adapted to steer the intake air differently as the rise of the piston 16, in order to homogenize the mixture.

In other words, the invention proposes a motor having lights 34 whose edges 40, 42 of gas orientation of the upper face 36 form with the radial direction angles "α ₄ ο", "a ₄ 2 ^M which are oriented according to a certain first sense and which are each included in a first predetermined angular range and in that the edges 46, 48 of the lower face 38 form with the radial direction "R" angles _"4 6 ^M," had "which are oriented in a second direction determined opposite to the first determined direction and which each are within a second angular range determined to provide a twisted light 34 adapted to steer the intake air differently as the rise of the piston 16.

This configuration has been shown in particular in FIGS. 7 to 9.

In FIGS. 7 to 9, the references "cuo" and "a ₄ 2 ^M " have been assigned to the angles formed between the respective edges 40 and 42 of the upper face 36 of the slot 34 and the radial direction "R", and the references _"4 6, had" the angles formed between the edges 46 and 48 of the lower face 38 of the light 34 and the radial direction "R".

In this configuration, the angles "cuo, α ₄ 2 ^Μ are, therefore, in accordance with the invention, oriented in a first determined direction, here for example the clockwise direction, as shown in FIG. 8, while the angles" α ₄ 6 ^Μ , "eue" respective edges 46 and 48 of the lower face 38 of the light 34 are oriented in the counterclockwise direction, as shown in Figure 9.

In the preferred embodiment of the invention, the angle α ₄ ο, α ₄ 2 in the first direction of orientation is within a first angular range determined between 25 and 45 degrees.

Furthermore, the angles α ₄ 6, α ₄ 8 in the second direction of orientation are in a defined angular range between 10 to 35 degrees in the second determined direction opposite to the first determined direction.

Thus the first angular range associated with orientation angles "cuo, α ₂ April ^Μ edges 40 and 42 of the upper face 36 of the lumen 34 is between the values of 25 and 45 ° relative to the radial direction "R" in the first direction determined.

The second angular range associated with angles of orientation _"4 6 ^M," had "of the edges 46 and 48 of the underside 38 of the lumen 34 is between the angular values of 10 and 35 ° relative to the radial direction "R" counter-clockwise opposite to the first determined direction.

This configuration makes it possible, as illustrated in FIG. 10, to propose a distribution 56 of the admission air which is substantially uniform since it results from an orientation of the air through the lights 34 which varies progressively as and as the descent and then the rise of the piston 16 and the shutting of the lights 34.

Indeed, when the piston 16 rises, it firstly channels the air through the entirety of the lights 34 and it shuts off little or no said lights 34. The air admitted is oriented substantially by the four edges 46, 48 of the lower face 38 and 40, 42 of the upper face 36.

Then, when the piston 16 rises, the lower portion of each lumen 34 is closed and the air is almost oriented only by the edges 40, 42 of the upper face 36 of the light 34 which are more steeply inclined than the lower edges 46, 48 of the lower face 38 of the light 34.

The result is substantially the combination of two swirling motions, a reduced swirling motion as caused by a substantially radial inlet, and a high swirling motion as produced by a substantially tangential orientation.

The distribution 56 of the air is therefore perfectly uniform in the combustion chamber.

As illustrated in FIG. 11, a fuel jet 59 made under these conditions within the combustion chamber 20 extends in the axial direction so uniformly but more amply in the chamber 20 than the fuel jet 50 carried out in a reduced vortex movement which has been shown previously with reference to FIG. 2. The fuel jet 59 also does not have the irregularities of distribution of the fuel mixture 51 injected in a high vortex movement as previously shown in FIG.

In the preferred embodiment of the invention which has been shown in FIG. 7, the upper 36 and lower 38 faces are substantially planar.

This configuration is not limiting of the invention. Alternatively (not shown) the upper face 36 is concave and facing the lower face 38. Similarly, the lower face can be convex and facing the upper face.

The upper face 36 and / or the lower face 38 may be slightly inclined relative to a plane orthogonal to the axis A of the cylinder 12 by an angle (not shown) less than 10 °.

It will also be noted that, advantageously, the angle of orientation "α ₄ ο, has ₄ 2 ^M of at least one stop 40, 42 of the upper face 36 of the light 34 and the angle" a ₄ 6, had The orientation of the stop 46, 48 facing the associated lower face 38 preferably forms a determined minimum angular deviation which is adapted to conform to the substantially vertical lateral faces 58, 60 of the light 34, which are determined by said 40, 46, on the one hand and, 42, 48, on the other hand, as shown in Figure 7, in a portion of divergent duct facing the inside of the cylinder.This configuration makes it possible to promote the diffusion of the air inside the combustion chamber.

Thus, the choice of a minimum angular distance determined between the angles of orientation "cuo" and _"4 ^6M two superposed edges 40, 46 and / or between the orientation angles" α ^Μ _{April 2,} "had of two superimposed edges 42, 48 make it possible to form at least one vertical lateral face 58 and or a vertical lateral face 60 in the form of a portion of divergent duct directed towards the inside of the cylinder 14, which improves the diffusion of air inside the combustion chamber 20.

The rising level of fresh air makes it possible to no longer trap the burnt gases that are thus drawn towards the valves. The evacuation of flue gases is therefore done automatically.

It will be understood that each vertical side 58, 60 extending substantially along the axis A of the cylinder 12 thus joins the upper face 36 and the lower face 38. For this purpose, the upper and lower faces 36, 38 are each attached to the lateral faces by fillets 59. The radius of such a fillet 59 is between 1mm and 3mm.

The best dimensioning of the lights 34 will be obtained with a distance between the lower face 38 and the upper face 36 between 5 and 20% of the stroke of the piston 16.

The invention thus makes it possible to advantageously favor fresh gas filling and evacuation of the flue gases from a two-cycle type engine comprising peripheral lights 34.

Claims

A two-stroke engine of a motor vehicle comprising at least one axial cylinder (12) having a bore (14) which slidably receives a piston (16),

said cylinder (12) having a peripheral wall (30) having a lower portion (32) in which a plurality of peripheral lumens (34) are provided, which open into the bore (14) and are adapted to be opened or closed by the piston (16) moving to allow or prohibit the admission of air into the cylinder (12),

each lumen (34) being oriented by a radial direction extending radially from the axis (A) of the cylinder and passing through the center of the outlet of said lumen into the bore, and delimited in the peripheral wall (30) by a upper face (36) and a lower face (38) vis-à-vis delimited by radial edges (40, 42, 46, 48) extending in directions of orientation substantially orthogonal to the axial direction (A) of the cylinder (12),

characterized in that the direction of orientation of the radial edges of the upper face (36) forms with the radial direction (R) on a plane orthogonal to the axial direction (A) of the cylinder an angle (α ₄ ο, α ₄ 2 ) which is oriented in a first predetermined direction, and in that the orientation direction of the radial edges of the lower face (38) forms with the radial direction (R) on said plane orthogonal to the axial direction of the cylinder an angle ( α ₄ 6, α ₄ β) which is oriented in a second determined direction opposite the first determined direction, to provide a twisted light (34) adapted to direct the intake air differently as the piston rises (16) to homogenize the mixture.

2. Heat engine according to claim 1, characterized in that the angle (α ₄ ο, α ₄ 2) in the first direction of orientation is within a first angular range determined between 25 and 45 degrees.

3. Thermal engine according to any one of claims 1 or 2, characterized in that the angles (α ₄ 6, α ₄ β) in the second direction of orientation are within a defined angular range between 10 to 35 degrees in the second determined sense opposite to the first determined direction.

4. Thermal engine according to any one of claims 1 to 3, characterized in that the upper face (36) is concave facing the lower face (38).

5. Heat engine according to any one of claims 1 to 4, characterized in that the lower face (38) is convex facing the upper face (36).

6. Heat engine according to any one of claims 1 to 3, characterized the upper (36) and lower (38) are substantially planar.

7. Heat engine according to claim 6, characterized in that the upper face (36) / lower (38) is slightly inclined relative to the plane orthogonal to the axis (A) of the cylinder (12) of an angle less than 10 °.

8. Heat engine according to claim 7, characterized in that the upper face (36) and the lower face (38) are joined together by means of a lateral face extending substantially along the axis (A) of the cylinder (12) and in that the upper (36) / lower (38) face is joined to the lateral face by a fillet.

9. Heat engine according to claim 8, characterized in that the radius of the fillet is between 1mm and 3mm.

10. Heat engine according to any one of claims 1 to 9, characterized in that the distance between the lower face (38) and the upper face (36) is between 5 and 20% of the stroke of the piston (16). .