FR3069578A1 - TWO-STROKE INTERNAL COMBUSTION ENGINE CYLINDER - Google Patents

Abstract

The object of the invention is a two-stroke equilibrium scanning internal combustion engine cylinder (1) which includes a first row of upper openings (4) positioned above a second row of lower openings. (4), and the upper (4) and lower (5) openings have a horizontal and / or vertical orientation angle. The invention also relates to an engine which comprises one or more cylinders (1).

Description

The present invention relates to the field of two-stroke internal combustion engines with equicurrent scanning (or uniflow in English). In this type of engine, the admission of fresh gas is carried out through lights (or openings) arranged in the lower part of a cylinder (also called jacket), the opening of which is controlled by a piston, and the exhaust of the burnt gases is effected by orifices located in the upper part of the cylinder so that the flow is oriented axially during a scanning phase, that is to say when the intake and the exhaust are simultaneously open. The invention relates more particularly to the cylinders constituting this type of engine.

Cylinders are known comprising lights made in the lower part of the cylinder, as visible in FIG. 1 which represents a state of the art known in the field. These lights have the function of ensuring a filling of fresh gas (such as oxidizer) and they have here a twisted shape which has the effect of generating an axial rotation movement of the gases in order to control the distribution of the gases in the cylinder. , to control the sweeping (process of exchange of the burnt gases by fresh gases) of the burnt gases and to allow an optimal fuel / oxidant mixture in order to obtain a combustion whose performance will be optimal.

However, it has been found that, for two-stroke engines comprising twisted lights, the sweep and charge rates, respectively characterizing the capacity for evacuating the burnt gases and trapping the fresh gases, are low, which is detrimental to engine performance.

In order to improve the efficiency of the engine, document DE754166A is also known which describes a two-stroke combustion engine comprising lights positioned in the lower part of the cylinder. The cylinder here comprises two rows of superimposed lights. The upper row includes lights which are oriented from the bottom of the cylinder upwards and tangentially to the cylinder so as to induce an axial rotational movement of the gases and the lower lights are oriented in the radial direction of the cylinder so as to allow the filling of fresh gas (like oxidizer for example).

In the same way as above, the sweeping and load rates of the motor remain low in the case of these motors. The combustion is not optimal and the engine efficiency is low. In addition, the separation of the two rows of lights by a strip induces on the one hand a reduction in the surface area owing to the strip and on the other hand, limits the mechanical longevity of the assembly due to the friction of the segments induced by the axial displacement of the piston in the cylinder.

In order to overcome the drawbacks mentioned above, a first aspect of the invention therefore consists in developing a cylinder for an engine containing a piston whose scanning is improved by optimal scanning of the burnt gases, good filling of the gases and moderation. of the axial rotational movement of the gases in the cylinder.

To this end, the invention relates to a cylinder of an internal combustion two-stroke engine with equicurrent scanning, said cylinder comprises:

- a peripheral wall which rises along an axis of revolution so as to form a cylindrical jacket in which a piston slides,

- A first circular row of at least two upper openings positioned above a second circular row of at least two lower openings and separated from said upper openings by a bar, and said upper and lower openings pass through the peripheral wall of the cylinder , each opening being composed of an intake section comprising a center, a gas outlet section comprising a center and a junction channel connecting said sections, oriented along a first relative direction axis for the upper opening and along a second relative direction axis for the lower opening, said relative direction axes extend from the center of the inlet section to the center of the outlet section.

The invention is more particularly characterized in that the first relative direction axis forms a first horizontal orientation angle with a plane P2 and the second relative direction axis forms a second horizontal orientation angle with a plane P3, so that the junction channels of the upper openings and the lower openings are oriented horizontally, said planes P2 and P3 intersect on the one hand the axis of revolution of the cylinder and on the other hand the center of the respective intake section of the gas.

The effect of having a horizontal angle for the upper openings makes it possible to generate an axial rotational movement in the flow in order to promote mixing during the combustion phase. This also makes it possible to ensure the scavenging of the burnt gases near the jacket and to ensure the horizontality and the flatness of the interface separating the fresh gases from the gases burnt during the scavenging. The effects of the horizontal angle of the lower openings are to moderate the axial rotational movement generated by the upper row, and thus to ensure the filling of fresh gases.

According to one aspect of the invention, the first horizontal orientation angle is between 20 ° and 60 ° and the second horizontal orientation angle is between -20 ° and 0 °. In an alternative embodiment of the angles, the first horizontal orientation angle can be between -20 ° and -60 ° while the second horizontal orientation angle can be between 20 ° and 0.

Choosing these values results in optimal scanning. These values can be set in connection with the characteristic dimensions of the cylinder and / or the vertical angles mentioned below.

According to one aspect of the invention, the relative axis of direction of the upper openings forms with a plane P1 transverse to the width of the cylinder a first angle of vertical orientation and the relative axis of direction of the lower openings forms with the plane P1 a second angle of vertical orientation so that the junction channel of the upper or lower openings is directed upwards or downwards from the cylinder.

Thus the fact that the junction channel of the openings of the upper row is oriented vertically has the effect of allowing the scavenging of the burnt gases. The fact that the junction channel of the openings in the lower row is directed towards the top of the cylinder has the effect of ensuring the filling of the cylinder.

According to one aspect of the invention, the first angle of vertical orientation is between -5 ° and -30 ° and the second angle (Θ2) of vertical orientation is between 5 ° and 30 °.

In an alternative embodiment of the angles, the first angle of vertical orientation can be between 5 ° and 30 ° while the second angle of vertical orientation can be between -5 ° and -30 °.

The choice of these values has the effect of generating an optimal sweeping of the gases burned in the cylinder and of ensuring an optimal filling of the cylinder.

According to one aspect of the invention, the inlet section of the upper opening has a height H1 and the outlet section of the upper opening has a height H1 'which can be 10 to 30% less than the height H1 so as to have a convergent shape of the upper opening without having a restrictive nature of the invention.

The shape of the upper opening is convergent so as to push back the minimum flow area at the end of the junction channel.

According to one aspect of the invention, the inlet section of the lower opening has a height H2 and the outlet section of the lower opening has a height H2 'which can be, without limitation, from 10 to 30 % at height H2 so as to have a convergent shape of the lower opening.

In the same way as above, the shape of the lower opening can be convergent so as to push back the minimum flow area at the end of the junction channel.

According to one aspect of the invention, the bar separating the two rows of lights is contained in the wall of the cylinder and comprises a recess which runs from the inside of the cylinder towards the outside of the latter over a length L so to obtain an internal section of a height H3 on the internal side of the bar.

The bar separating the lower and upper rows is chambered so as to avoid friction of the segments on the bar and to simplify lubrication. In addition, this increases the surface area of the flow and thus improves the permeability of the lights.

According to one aspect of the invention, the height H1 is between 20 and 30% of a total height H defined by the addition of H1, H2 and H3, the height H2 is between 60 and 70% of the total height H , and the height H3 of the bar is approximately 10% of the total height H.

A second aspect of the invention also relates to a two-stroke internal combustion engine with equal current scanning which comprises at least one cylinder as described above.

The advantage of having an engine comprising such cylinders is that it has improved performance.

Brief presentation of the figures

Other characteristics and advantages of the device according to the invention will appear on reading the description below of a non-limiting example of embodiment, with reference to the appended figures and described below.

FIG. 1 illustrates a cylinder known in the state of the art,

FIG. 2 is a perspective view of the bottom of the cylinder according to an embodiment of the invention,

FIG. 3 is a side sectional view along two planes P2 and P3,

FIG. 4 is a front view of the interior of the bottom of the cylinder according to an embodiment of the invention,

FIG. 5 is a sectional view of the cylinder of FIG. 4 along a plane P1,

FIG. 6 is a sectional view of the cylinder of FIG. 4 along a plane P1,

Detailed description of the invention

FIG. 2 represents, schematically and in a nonlimiting manner, a cylinder 1 (which may also be called a jacket) of a two-stroke internal combustion engine and with equicurrent scanning and more particularly the bottom part of cylinder 1. Conventionally this cylinder 1 is composed of a peripheral wall 3 which rises along an axis of revolution Δ over a certain distance which is a function of the dimensions of the engine. In some cases the peripheral wall 3 rises to a cylinder head (not shown) which closes the top of the cylinder 1 and which incorporates valves (not shown). Other cases can also arise such as that of opposite piston engines where the top of the cylinder is not closed by the cylinder head. The bottom of the cylinder 1 comprises a double row of converging lights (also called openings) inclined horizontally and / or vertically. The cylinder 1 incorporates within it a movable piston (not shown). FIG. 3 represents a sectional view, along two planes P2 and P3, of an upper opening 4 and of a lower opening 5. The sectional view along A-A 'is a side view in the plane P2 of one of the upper openings 4 of the upper row and can be viewed in the upper part of FIG. 3. The sectional view along B-B 'is a side view in the plane P3 of one of the lower openings 5 of the lower row and can be viewed in the lower part of FIG. 3. In connection with FIGS. 2 and 3, the wall 3 of the cylinder 1 comprises the upper 4 and lower openings 5. The upper 4 and lower 5 openings pass through the peripheral wall 3 of the cylinder 1. Each opening (4,5) is composed of an intake section 6 comprising a center C, a gas outlet section 7 comprising a center C 'and a junction channel 8 connecting said sections ( 6,7). It should be noted that the plane P2 is the plane which passes through the axis of revolution Δ of the cylinder 1 and through the center C of the intake section 6 of the upper opening 4 and the plane P3 is the plane which passes by the axis of revolution Δ of the cylinder 1 and by the center C of the inlet section 6 of the lower opening 5. The upper openings 4 are oriented along a first relative axis of direction XX ′. This relative direction axis stretches from the center C of the inlet section 6 to the center C ’of the outlet section 7 substantially parallel to the junction channel 8. It is specific to each upper opening 4. The lower openings 5 are, in turn, oriented along a second relative axis of direction Y-Y 'which stretches from the center C of their section 6 for admission to the center C' of their section 7 outlet and this substantially parallel to the channel 8 of junction of the lower openings 5. In the same way each lower opening 5 has its own direction axis.

Still in connection with FIGS. 2 and 3, the first row of openings comprises an alternation of upper openings 4 in the peripheral wall 3 of the cylinder 1 and each opening 4 is oriented along the relative axis of direction XX 'which his own. Below this first row of openings, the cylinder 1 comprises a second row of openings which also includes an alternation of lower openings 5 in the peripheral wall 3 of the cylinder 1 and which are oriented along the relative axis of direction Y -Y 'its own. In alternative embodiments, the number of upper 4 and lower 5 openings may be the same or the number of upper 4 openings may be greater or less than the number of lower 5 openings without thereby departing from the scope of the invention .

In the context of the invention, the relative axis of direction X-X ’of the upper openings 4 forms with a horizontal plane P1 a first angle (Θ1). This angle, called the vertical orientation angle, is chosen so that the channel 8 for joining the upper openings 4 is directed vertically in the cylinder 1, and more precisely towards the bottom of the cylinder 1. The plane P1 is a plane which is transverse to the width of the cylinder 1 and perpendicular to the axis of revolution Δ, as visible in FIGS. 3 and 4. The relative axis of direction Y-Y 'of the lower openings 5 forms with the plane P1 a second angle (Θ2) of vertical orientation so that the channel 8 for joining the lower openings 5 is also directed vertically and in particular towards the top of the cylinder 1.

In a nonlimiting exemplary embodiment, the first angle (Θ1) of vertical orientation is preferably between -5 ° and -30 ° and the second angle (Θ2) of vertical orientation is preferably between 5 ° and 30 °. Of course, these angles can vary depending on the number of upper 4 and lower 5 openings and are not limited to these angular ranges. In an alternative embodiment of the angles, the first angle (Θ1) of vertical orientation can be between 5 ° and 30 ° while the second angle (Θ2) of vertical orientation can be between -5 ° and -30 ° .

As shown in Figure 3, the intake section 6 of the upper opening 4 has a height H1. The outlet section 7 of the upper opening 4 has a height H1 ’. The height ΗΊ is 10 to 30% less than the height H1, which makes it possible to have a converging shape of the junction channel 8 and more particularly of the upper opening 4.

It is the same for the inlet section 6 of the lower opening 5 which has a height H2 which is 10 to 30% greater than the height H'2 of the outlet section 7 of the lower opening 5 and this always with the aim of having a convergent shape of the lower opening 5.

The first row of openings as well as the second row of openings are separated by a strip 9 visible in FIG. 3. The strip 9 is contained in the peripheral wall 3 of the cylinder and includes an opening, or recess, which runs from from the inside of the cylinder 1 towards the outside of the latter over a length L. Obviously, an internal section 10 appears on the inside of the bar 9. This section 10 has a height H3.

The recess is applied so as to avoid contact between the bar 9 and the segmentation on the one hand and to avoid a reduction in the surface area on the other hand.

The total height H of the opening device is given by the addition of H1, H2 and H3. The upper row has a height H1 of 20 to 30% of the total height H, the lower row has a height H2 of 60 to 70% of the total height H and the bar 9 separating the upper and lower rows has a height H3 of About 10% of the total height H.

The upper 4 and lower 5 openings also have a horizontal orientation which is shown in FIGS. 4 to 6. For this purpose, FIG. 4 represents a front view of the interior of the bottom of the cylinder which reveals the outlet sections 7 upper 4 and lower 5 openings and indirectly the internal section 10 of the bar 9 (not visible insofar as the latter is set back relative to the other sections (6,7)). Figures 5 and 6 are sections in the plane P1 of Figure 4. The openings 4 of the upper row are oriented tangentially so as to induce a movement of axial rotation (or swirl) to the flow in the cylinder 1 and the openings in the lower row 5 have a zero or negative horizontal angle so as to fill and moderate the swirl generated by the openings in the upper row 4.

For this purpose the first relative axis of direction X-X 'forms a first angle (a1), called horizontal orientation angle, with the plane P2, as visible in FIG. 5 which is a sectional view from above along C- C ′ in the plane P1 of FIG. 4 of the upper openings 4. This horizontal orientation angle is chosen so that the channel 8 for joining the openings is directed horizontally. In other words, the direction of the junction channel can be offset from the axis of revolution Δ of cylinder 1. The first angle (a1) of horizontal orientation is between 20 ° and 60 °.

The second relative axis of direction Y-Y 'forms a second angle (a2) of horizontal orientation with the plane P3, as visible in FIG. 6 which is a view in section from above along D-D' in the plane P1 of lower openings 5.

According to an exemplary embodiment, the second angle (a2) of horizontal orientation is between -20 ° and 0 °. The angular range can obviously be adjusted according to the number of lower openings 5. In an alternative embodiment of the angles, the first angle of horizontal orientation can be between -20 ° and -60 ° while the second angle horizontal orientation can be between 20 ° and 0.

The invention operates as follows: the gas exchange process, called sweeping, is characterized by almost simultaneous intake and exhaust phases where the gases burned in the cylinder 1 are pushed by the fresh gases from admission. The admission of fresh gas into cylinder 1 is ensured by the lower openings 5 of cylinder 1 which are successively uncovered and masked by the displacement of the piston.

As the upper openings 4 are oriented tangentially, there is an effect of axial rotational movement for the gases admitted to the flow in the cylinder 1 and as the lower openings 5 have a zero or negative horizontal angle, we have at the same time the filling of the cylinder 1 which is carried out and the axial rotational movement is attenuated and controlled. Also as the bar 9 separating the openings (4, 5) is hollowed out, the friction of the piston rings on the bar 9 is avoided and the flow area available to the admitted gases is maximized. The two types of openings (4,5) having a convergent shape, it is possible, in the engine operating process, to push back the minimum discharge surface at the end of the bar 9. The operation of such an engine is performs in three phases.

Firstly, the upper openings 4 are discovered and the fresh gases are admitted tangentially into the cylinder.

In a second step, the upper 4 and lower 5 openings are uncovered and a reduction in the axial rotation movement is obtained, a filling and an ascent of the interface separating the fresh gases from the burnt gases.

In a third step, only the upper openings 4 are discovered and there is then a return of the piston.

Such an engine thus has a more efficient scavenging of the burnt gases than the engines of the state of the art, in particular on the periphery of the cylinder 1.

By way of comparison, the scanning induced by the double rows of openings (4, 5) was compared by digital three-dimensional simulation of fluid mechanics with a design of the state of the art, which is represented in FIG. 1, and shows that the sweep is more efficient for the double rows of openings (4, 5) where the gas trapping and scavenging ratios are five points higher than for a state engine. art.

The upper 4 or lower 5 openings may be staggered or aligned with one another without affecting the quality of the scanning.

In addition, the advantage of such a motor lies in the fact that the level of the axial rotation movement effect is adjustable and controllable by calibrating the angle of the upper openings 4, calibrating the heights of these same openings but also by calibrating the angle of the lower openings 5 as well as calibrating the heights of these same 5 lower openings.

It goes without saying that the invention is not limited to the sole embodiment of the openings, described above by way of example, on the contrary, it embraces all the variant embodiments.

Claims (9)

1) Cylinder (1) of a two-stroke internal combustion engine with equicurrent scanning, said cylinder (1) comprises: - a peripheral wall (3) which rises along an axis of revolution (Δ) so as to form a cylindrical jacket in which a piston slides, a first circular row of at least two upper openings (4) positioned above a second circular row of at least two lower openings (5) and separated from said upper openings (4) by a bar (9), and said upper (4) and lower (5) openings pass through the peripheral wall (3) of the cylinder (1), each opening (4,5) being composed of an intake section (6) comprising a center C, d 'a gas outlet section (7) having a center C and a junction channel (8) connecting said sections (6,7), oriented along a first relative axis of direction X-X' for l 'upper opening (4) and along a second relative direction axis Y-Y' for the lower opening (5), said relative direction axes (X-X ', Y-Yj stretch from the center Cde the intake section (6) at the center C ′ of the outlet section (7), characterized in that the first relative direction axis X-X 'forms a first angle (a1) of horizontal orientation with a vertical plane P2 and the second relative axis of direction YY' forms a second angle (a2) of horizontal orientation with a vertical plane P3, so that that the channels (8) joining the upper openings (4) and the lower openings (5) are oriented horizontally, said planes P2 and P3 intersect on the one hand the axis of revolution (Δ) of the cylinder (1) and d on the other hand the center Cde of the respective gas intake section (6). 2) Cylinder (1) of combustion engine according to claim 1, characterized in that the first angle (a1) of horizontal orientation is between 20 ° and 60 ° (respectively 20 ° and -60 °) and the second angle (a2) of horizontal orientation is between -20 ° and 0 ° (respectively 20 ° and 0 °). 3) Cylinder (1) of a combustion engine according to one of the preceding claims, characterized in that the relative axis of direction XX 'of the upper openings (4) forms with a plane P1 transverse to the width of the cylinder (1 ) a first angle (Θ1) of vertical orientation and the relative axis of direction Y-Y 'of the lower openings (5) forms with the plane P1 a second angle (Θ2) of vertical orientation so that the channel (8) junction of the upper (4) or lower (5) openings is directed respectively upwards and downwards from the cylinder (1). 4) Cylinder (1) of combustion engine according to the preceding claim characterized in that the first angle (Θ1) of vertical orientation is between -5 ° and -30 ° (respectively 5 ° and 30 °) and the second angle (Θ2) vertical orientation is between 5 ° and 30 ° (respectively -5 ° and -30 °). 5) cylinder (1) of combustion engine according to one of the preceding claims characterized in that the intake section (6) of the upper opening (4) has a height H1 and the outlet section (7) of the upper opening (4) has a height H1 '10 to 30% lower than the height H1 so as to have a convergent shape of the upper opening (4) which is directed towards the inside of the cylinder (1). 6) cylinder (1) of combustion engine according to one of the preceding claims characterized in that the intake section (6) of the lower opening (5) has a height H2 and the outlet section (7) of the lower opening (5) has a height H2 '10 to 30% lower than the height H2 so as to have a convergent shape of the lower opening (5) which is directed towards the interior of the cylinder (1). 7) Cylinder (1) of combustion engine according to one of the preceding claims characterized in that said strip (9) is contained in the peripheral wall (3) of the cylinder (1) and comprises a recess which runs from an inner side of the cylinder (1) to an outer side thereof over a length L so as to obtain an internal section (10) of a height H3 on the inner side of the bar (9). 8) Cylinder (1) of combustion engine according to claims 5 to 7 characterized in that the height H1 is between 20 and 30% of a total height H defined by the addition of H1, H2 and H3, the height H2 is between 60 and 70% of the total height H, and the height H3 of the bar (9) is approximately 10% of the total height H. 9) Two-stroke internal combustion engine with equal current scanning, characterized in that it comprises at least one cylinder (1) according to one of the preceding claims.