Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
  • F02B25/14—Engines characterised by using fresh charge for scavenging cylinders using reverse-flow scavenging, e.g. with both outlet and inlet ports arranged near bottom of piston stroke
  • F02B25/16—Engines characterised by using fresh charge for scavenging cylinders using reverse-flow scavenging, e.g. with both outlet and inlet ports arranged near bottom of piston stroke the charge flowing upward essentially along cylinder wall opposite the inlet ports

Definitions

• the present invention relates to a method and a device for scanning a two-stroke internal combustion engine cylinder, with piston driven by a reciprocating rectilinear movement, of the self-supercharging type by post-filling effect, in which the distribution of each cylinder is exclusively ensured by the piston in cooperation with the intake lights-intake ducts group and with the exhaust lights-exhaust ducts group, the intake lights group being discovered longer by the piston as the group of exhaust lights, and two-stroke engine provided with such a sweep.
• the subject of the invention is essentially a method and a device for adjusting the flow for the temporary counter-sweeping of the burnt gases in the intake ducts during the pre-exhaust phase preceding the opening of the lights.
• Post-filling is therefore understood to mean the introduction of an additional air charge into the cylinder, after sweeping and closing the exhaust orifices.
• purging air the purging agent intended for the renewal of the burnt gases from the cylinder, whether it be pure air or any other oxidant-fuel mixture.
• Engines of the aforementioned type are already known, in particular such a two-stroke engine, consisting of at least one group of two cylinders, the operating cycles of which are set relative to one another at 180 of crankshaft angle , in which the energy of the pre-exhaust gases of one cylinder is used to carry out the post-filling of the other cylinder, is described in FR-A-2 346 558 or its equivalent CH-A-593 420 of this applicant, and shown in Figures 1 to 5 of this publication.
• a preferred version of the device for implementing this process is the subject of a co-application in PCT form from the inventor under the N ° PCT / FR 88/00155 published under the n ° W0 88/08073 .
• the actual optimal volume of the sweeping conduits must naturally be greater than the theoretical optimal volume to avoid any risk of post-filling with burnt gases, but as little as possible, otherwise the self-supercharging potential will deteriorate on the one hand ( decrease in the pressure level reached in said conduits, if the energy supplied by the pre-exhaust gases is distributed over too large a volume) and on the other hand the efficiency of the engine (loss of expansion in the cylinder increased without beneficial effect on the increase in post-filling thus obtained),
• a main aim of the invention is to propose a global technical solution to the problems posed by simultaneously satisfying all of the requirements mentioned above.
• Another objective of the invention is to keep the advantages described in the two above-mentioned patents CH-A-593 420 ( twin-cylinder) and FR-87 04757 (single-cylinder) to the maximum.
• the main object of the invention is also to solve the new technical problem consisting in providing a solution allowing, in the context of self-supercharging by post-filling, to use an inverted loop while eliminating the inherent drawbacks to this reverse loop cited by VENEDIGER.
• the present invention solves for the first time this new technical problem in a manner which is completely non-obvious to those skilled in the art by overcoming the prejudices thereof relating to the use of a reverse loop and to positioning. from the lower edge of the intake light to the bottom dead center.
• An additional objective is to organize a large turbulence field ensuring a good mixture of air and fuel, with a view to the combustion phase, at all loads and all engine operating speeds, while avoiding in addition the particular case of the spark ignition engine any loss of fuel from the exhaust.
• the invention provides, according to a first aspect, a method of scanning a two-stroke internal combustion engine cylinder, with self-supercharging by post-filling effect, in which the distribution of each cylinder is exclusively ensured by the piston in cooperation with the intake lights-intake ducts group, hereinafter referred to as the intake group, and with the exhaust lights-exhaust ducts group, hereinafter referred to as the exhaust group, the intake lights being discovered by The piston longer than the exhaust lights, comprising a post-filling phase in an essentially closed environment, All of the air arriving at the cylinder entering through the intake group, characterized in that the air flows are directed sweep from the intake group so that they meet at an impact point located on the upper wall of the cylinder located above the exhaust lights, to perform a so-called inverted loop, then pressing on the head of the cylinder, then on the wall of the cylinder diametrically opposite to the exhaust ports, and finally on the head of the piston before reaching the exhaust ports; and the intake lights are placed relative to the cylinder
• the method according to the invention is characterized in that a front for separating the burnt gases is produced with the sweeping air substantially perpendicular to the line of the centers of the intake ducts.
• the engine is not refrigerated, and in particular the intake ducts at low loads.
• the invention relates, according to a second aspect, to a device for scanning a two-stroke internal combustion engine cylinder, with self-supercharging by post-filling effect in which the distribution of each cylinder is exclusively ensured by a piston.
• a device for scanning a two-stroke internal combustion engine cylinder driven by an alternating rectilinear movement, in cooperation with a group of intake lights-intake ducts, hereinafter referred to as intake group, and with a group of exhaust lights-exhaust ducts, hereinafter referred to as exhaust group, the intake lights of which are discovered longer by the piston than the exhaust lights, comprising post-resurfacing means in an essentially closed environment, the intake group serving as the sole air intake channel for the cylinder , characterized in that the intake unit is arranged relative to the cylinder so that the purge air flows from the intake lights meet in a impact point located on the upper wall of the cylinder above the exhaust lights, to perform a so-called reverse loop; and the altitude of the lower edge of the intake lights is
• this device is characterized in that the intake ducts are inclined at an elevation angle relative to the cylinder so as to produce a front for separation of the burnt gases with L sweeping air substantially perpendicular to the line of the centers of the intake ducts.
• the invention also relates to an engine equipped with such a device, or implementing the method previously stated.
• FIG. 1a, 1b schematically show, in vertical axial section, a cylinder of a two-stroke engine whose intake and exhaust ports are arranged symmetrically with respect to the plane of symmetry of scanning so as to achieve the classic Schn ⁇ rle loop of prior art;
• FIG. 2 shows schematically a view similar to Figure 1, but of a device according to the invention for implementing the method according to the invention
• FIG. 3 shows a cross-sectional view of the device according to the invention of Figure 2, which comprises a single group of two intake lights and a single group of a single exhaust light, according to one embodiment currently preferred;
• - Figure 4 shows a folded half-section view of the vertical plane parallel to the axis of the cylinder containing the main direction vector of the gas flow from the intake duct shown in Figure 3 by arrow 30;
• - Figure 5 shows another view in vertical section passing through the arrows 30 of Figure 3, allowing to see the two intake ducts arranged symmetrically with respect to the exhaust ducts, forming the subject of Figure 3 and represents the beginning of the pre-exhaust by showing the gas separation front;
• FIG. 6 shows an embodiment of an engine equipped with two cylinders set at 180 °
• FIGS. 7a, 7b show an alternative embodiment of the piston with a local reduction to the right of one of the two intake ports.
• the cylinder 1 comprises at least two intake ports 2 and at least one exhaust port 3, the lower edge of the intake port is located conventionally at the bottom dead center (PMB), which also coincides with the lower edge of the exhaust port.
• the exhaust port is arranged in a wall of the cylinder substantially opposite to the wall of the cylinder towards which the flows of purge air coming from the intake conduits 2 converge.
• the cylinder 10 comprises a group of intake lights 12a, 12b and intake ducts 14a, 14b (intake group) that can be seen in Figures 2 to 5, and a group of exhaust ports 16 and exhaust ducts 18 (exhaust group).
• intake group a group of intake lights 12a, 12b and intake ducts 14a, 14b
• exhaust group a group of exhaust ports 16 and exhaust ducts 18
• the intake lights 12a, 12b are arranged laterally in the cylinder 10 relative to the exhaust lights 16 so that the intake lights 12a, 12b are exposed by the piston 22 longer than the exhaust lights 16.
• the intake group (12a, 12b; 14a, 14b) is arranged relative to the cylinder (10) so that the purge air flows from the intake lights (12a, 12b) meet at a point impact located on the upper wall (10a) of the cylinder (10) above the exhaust ports (16), to perform a so-called inverted loop; and the altitude (A) of the lower edge of the intake ports (12a, 12b) is arranged sufficiently high in the cylinder (10) relative to the altitude (B) of the upper edge of the exhaust ports (16 ) to substantially completely eliminate any possibility of intersection of the air flows entering the cylinder (10) with the burnt gases leaving the cylinder (10) during the path between the entry points of the purge air flows and their point of impact.
• the altitude (A) of the lower edge of the intake lights (12, 12b) is located in the vicinity or above the altitude (B) of the upper edge of the exhaust lights (16).
• the intake ducts 14a, 14b of each pair are arranged laterally symmetrically with respect to a plane of scanning symmetry which substantially coincides with the longitudinal plane of symmetry of the cylinder passing through the exhaust ports.
• the intake ports 12a, 12b and the exhaust ports 16 are arranged symmetrically with respect to the abovementioned scanning plane of symmetry which here coincides substantially with the longitudinal plane of symmetry passing through the exhaust port 16.
• the intake ducts 14a, 14b are disposed laterally inclined with respect to the cylinder, at an elevation angle p mentioned in FIG. 4, so that the front separating the burnt gases with the scavenging air is substantially perpendicular at the Line of centers of each intake duct 14a, 14b, as shown in Figure 5.
• groups of intake ducts 14a, 14b are provided, arranged in pairs, each pair being able to have a different inclination, so that the meeting point of the flows of all the pairs is at an altitude. substantially identical.
• the half-angle of arrow t- Preferably, the half-angle of arrow t-.
• the angle ⁇ associated with each pair of intake ports 12a, 12b is between approximately 45 and approximately 135.
• the angle ⁇ is advantageously between approximately 70 ° C. and 110 ° C.
• this device comprises a single group of two intake ports 12a, 12b and a single group of a single exhaust port 16, or two exhaust ports 16.
• FIG. 2 a distinction has been made between the different fluids present by representing the burnt pre-exhaust or exhaust gases by solid circles, and the purge intake air by bubbles.
• the intermediate positions of the gas separation front have been shown in dashed lines and in continuous lines the front F of the position actually represented.
• arrow 13 represents the movement of circulation of the sweeping air in the chamber according to the so-called reverse loop.
• angles of elevation ⁇ and of half-arrow ⁇ - of the main vectors (30) of the intake ducts with respect to the cylinder can vary within certain limits as a function of the reference position
• each group of intake ducts 14a, 14b leads to a group of lights located below the bottom dead center (PMB) as described and shown with particular reference to Figures 1b; 5a, 5b; 6a, 6b of the PCT application WO 88/08073 of the applicant incorporated here by reference. These lights are placed in intermittent communication either with the intake source, or with a storage chamber provided inside the piston, this solution being called single cylinder.
• PMB bottom dead center
• FIG. 6 represents an alternative embodiment of an engine equipped with the twin-cylinder solution of the type described in CH-593 420, with the device according to the invention which is the subject of the preceding figures 2 to 5, limited here by simplification to a module of two cylinders 10A, 10B, set at 180, equipped with two intake ducts 14a, 14b and two exhaust ducts 30a, 30b each leading to the light 16a, 16b.
• the cutting of this engine is carried out perpendicular to the axis of each cylinder.
• the scanning symmetry planes of the two cylinders are merged and pass, as mentioned previously, through the two axes 32a, 32b of the cylinders 10A, 10B.
• the invention makes it possible to satisfy all of the aims referred to in points 1 to 12 at the start of the description and in particular in point 10, concerning the minimum center distance enabling a maximum displacement to be achieved in a given size.
• each pair of intake lights has a light (12a) on one side of the aforementioned scanning plane of symmetry which is discovered longer by the piston than the light (12b) located on the other side of this plane of symmetry. It follows that it is possible to create at the end of the post-filling period, in each cylinder, a vortex with an axis parallel to that of the cylinder.
• Figures 7a, 7b show an alternative embodiment of a piston 22 with a local reduction 40 of the edge 38 to the right of one of the two intake ports to cause delayed closure of this light relative to the other light in order to create the vortex represented by the arrow T.
• the engine is not cooled at low loads by interrupting the engine cooling circuit and in particular the supply channels including the intake ducts, while we refrigerate since Intermediate loads up to Maximum load by opening the refrigeration circuit.
• the absence of refrigeration at low loads makes it possible to raise the temperature of the intake air by virtue of its heating by the walls of the intake ducts 14a, 14b themselves heated by the pre-exhaust gases.
• the rise in temperature of the intake gases increases their volume and produces a decrease in the volume of residual exhaust gases in the cylinder, which favorably influences the minimum flammability threshold of the purge air-residual gases mixture mainly in the case of spark ignition engines.
• the part of the intake conduits 12a, 12b opening into the cylinder 10 is provided to be substantially perfectly cylindrical, which greatly facilitates the production of the shapes and the precision of their geometry.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)
• Characterised By The Charging Evacuation (AREA)
• Lubrication Details And Ventilation Of Internal Combustion Engines (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1988
  • 1988-03-25 FR FR8804002A patent/FR2629131A1/fr not_active Withdrawn
• 1989
  • 1989-03-24 EP EP89904084A patent/EP0444027B1/de not_active Expired - Lifetime
  • 1989-03-24 DE DE68915776T patent/DE68915776T2/de not_active Expired - Fee Related
  • 1989-03-24 WO PCT/FR1989/000139 patent/WO1989009328A1/fr not_active Ceased
  • 1989-03-24 JP JP1503758A patent/JP2707344B2/ja not_active Expired - Lifetime

Non-Patent Citations (1)

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