FR2887584A3 - Intake system for e.g. diesel engine, has intake ducts with ports, where ports are shifted radially with respect to central axis of combustion chamber to control variation of swirl level for same speed of internal combustion engine - Google Patents

Abstract

The system has intake ducts (1, 1`) with ports (7, 7`) opening into a combustion chamber (9), where the opening is controlled by inlet valves. The ports are diametrically opposite with respect to a central axis of the combustion chamber. Two seal valves (6, 6`) disposed in the ducts vary the aerodynamic level such as swirl level, associated to each duct. The ports are shifted radially with respect to the axis of the chamber for controlling the variation of the swirl level for the same speed of an internal combustion engine. An independent claim is also included for a combustion method for an internal combustion engine using an intake system.

Description

Aerodynamic intake system

  The invention relates to the field of intake systems for an internal combustion engine whose mixture of air and fuel has a high level of aerodynamics. More particularly it is a system for generating a tourbillon said swirl axis adjacent to that of the cylinder, the swirl level being adapted to the engine speed and variable.

  The level of swirl is the ratio between the speed of rotation of the air inside the cylinder and the speed of rotation of the motor shaft. The higher the level of swirl, the more the mixture in the combustion chamber of the engine is homogeneous. The homogeneity of the mixture provides better combustion and therefore better performance and less pollution. The swirl, however, involves consequences at the level of admission. Indeed, when an air vortex is created in the intake manifold, the permeability decreases. The permeability that makes it possible to quantify the efficiency of a valve lift law, in percentage, compared to an ideal law, for which the valve would open instantaneously, is directly a function of the flow rate of the air. The air flow for a swirling flow is indeed less than for a rectilinear flow. Thus when the permeability decreases the engine receives a smaller amount of air, knowing that the higher the level of swirl increases, the more the permeability decreases. There is a compromise to be found so that we have at the same time a good permeability and a good level of swirl, the level of swirl must be adjusted according to the engine speed to have a low level of swirl at low speed and a low swirl level at high speed.

  There are engine systems with two dual intake ducts combined with two exhaust ducts and two spark plugs. In this device, the two accesses of the exhaust ducts are diametrically opposed, according to a diameter and the two accesses of an intake duct are positioned symmetrically with respect to the two other accesses of the other intake duct, according to a plane of vertical symmetry, the plane of symmetry comprising the central axis of the combustion chamber and the diameter in which the exhaust ducts are opposite. Such a device is described in particular by patent IT1245678.

  However, this patent does not teach variation of the swirl for the same engine speed. It is therefore not possible to control the swirl level.

  There are engine systems having an intake duct dividing in two and opening into the combustion chamber by two diametrically opposed inlet openings. Such a device is described in particular by the patent US6267096. However, this patent does not teach swirl variation for the same engine speed or control of the swirl level. In addition, the structure described in this patent has a right angle elbow for one of the intake ducts, which implies a pressure drop, due to the disturbances of the air flow appearing at the level of the duct. the right angle in the conduit.

  There are systems with two diametrically opposed intake ducts and two diametrically opposed exhaust ducts. Such a device is described in particular by patent JP57062926. However this patent does not teach variation of the swirl for the same engine speed nor the control of the level of swirl.

  The present invention therefore aims to overcome several disadvantages of the prior art by creating an assembly in an internal combustion engine to have a swirling air flow, during admission, along an axis close to that of the cylinder, the swirling effect being optimized by the structure of the intake system and the swirl level being variable for the same engine speed.

  This objective is achieved thanks to an optimized and variable aerodynamic intake system associated with a combustion chamber, comprising at least two intake ducts, each having an access, opening into the combustion chamber, of which the opening is controlled at least by an intake valve, the two access ports of the inlet ducts being diametrically opposed, characterized in that it comprises means for disturbing the air flow of at least one intake duct and that the accesses of the intake ducts are offset radially with respect to the center of the combustion chamber.

  According to another feature, the accesses of the intake ducts in the combustion chamber are placed as close as possible to the periphery of the combustion chamber so that there is a functional clearance between the periphery of the combustion chamber. and the periphery of the access ports, allowing the lift of the intake valves.

  According to another feature, the airflow disruption means are two shutter valves each disposed in an intake duct, upstream of the access to the combustion chamber.

  According to another feature, the opening and closing devices of the intake ducts each comprise at least one intake valve and the means of disruption of the air flow are achieved by a variable lift of the intake valves.

  According to another particularity, the intake system is coupled with two exhaust ducts opening into the combustion chamber by two ports, the opening of which is each controlled by an exhaust valve, the access of the exhaust ducts being diametrically opposed.

  According to another feature, the axis joining the center of the accesses of the exhaust ducts forms a right angle with the axis joining the center of access of the intake ducts.

  According to another feature, at least one intake duct opens into the combustion chamber in a direction tangent to the wall of the combustion chamber.

  According to another feature, at least one intake duct opens into the combustion chamber in a helical path.

  According to another feature, the angle formed by the shutter valves relative to the axis of the duct is controlled by first means and second control means control the variable lift of the valves according to the speed.

  According to another particularity, above a determined high speed, the first means control the angle of the valves to 0 and the second means controls the raising of the valves to the maximum.

  According to another feature, below a low speed determined first means control the angle of the valves at a maximum determined angle and the second means control the raising of the valves to a minimum.

  According to another feature, a combustion method for an internal combustion engine using an intake system according to the invention comprises a scanning cycle.

  The invention, its characteristics and its advantages will appear more clearly on reading the description made with reference to FIG. 1 representing a view from above of the accesses of the intake ducts and of the accesses of the exhaust ducts in the cylinder head.

  The invention will now be described with reference to FIG. 1. The cylindrical combustion chamber (9) has two access ports (7, 7 ') of intake ducts (1, 1') and two access ports (8). , 8 ') exhaust ducts (2, 2'). The accesses (7, 7 ', 8, 8') are made in the cylinder head (3, 3 ') which closes the combustion chamber. Opening or closing of the ports (7, 7 ') of the intake ducts (1, 1') and the ports (8, 8 ') of the exhaust ducts (2, 2') are carried out respectively by the intake and exhaust valves. An injector (4) optionally located inside the combustion chamber allows a direct injection of fuel and a glow plug, in the case of a diesel engine, or ignition, in the case of a gasoline engine is located possibly inside the combustion chamber. The injector (4) and the spark plug (5) have a position close to that of the center of the axis of the combustion cylinder and are fixed in the cylinder head (3, 3 ').

  The two accesses (7, 7 ') of the ducts (1, 1') for admission into the combustion chamber (9) are of the same shape and diametrically opposite with respect to the central axis of the combustion chamber (9). . The distance (J) between the access (7, 7 ') of an intake duct (1, 1') and the periphery of the combustion chamber (9) is a minimum one such that the valve closes the access (7, 7 ') of the duct (1, 1') intake can rise, according to its normal operation. The rotation of the air inside the combustion cylinder (9), also called the combustion chamber (9), is caused by the injection of air at its periphery. The center of the vortex being about the axis of the cylinder, the effect of swirl caused by the admission of air will be all the more important that the intake opening will be located at the periphery of the cylinder.

  The symmetrical position of the accesses (7, 7 ') of the intake ducts contributes to making the air vortex symmetrical by acting symmetrically on the fluid inside the combustion chamber (9). These two structural features contribute to the creation of an air swirl, called swirl, having an axis closest to that of the combustion chamber (9).

  The position of the accesses (7, 7 ') of the inlet ducts (1, 1') creates a given swirl level at a given engine speed. In order to vary the swirl level for the same engine speed, flaps (6, 6 ') are introduced into the intake ducts (1, 1'), the position of the flaps (6, 6 ') being adjustable. . The valves (6, 6 ') shutters positioned tangentially to the air flow do not create a disturbance. The more the angle of separation of this tangential position increases, the greater the disturbance created will be important. A position separated from the tangential position is shown in dotted lines, the tangential position of the shutter (6, 6 ') being shown in solid lines. It is therefore possible to vary the swirl level for the same engine speed. For low engine speeds, requiring a lower intake of air volume, the homogeneity of the mixture of air and fuel will be increased by the addition of a disturbance, in order to have a better combustion giving a better performance and a less polluting effect. Conversely, the more shutoff valves (6, 6 ') each have a position close to the position tangential to the flow, shown in solid line, the greater the permeability will be important. A high permeability will be set for a high engine speed to promote air supply. The purpose of this adjustment is therefore not to disturb the flow of air in order to introduce a maximum of air into the combustion chamber (9).

  In another embodiment, the intake system includes a swirl level variation device provided by an adjustable valve control for varying the advance of the valves. The use of a variable lift system of the intake valves has the effect of affecting the permeability. The permeability is directly related to the lift height of the valves. The air passes so much less well that the valves are not open and there is then a drop in permeability. This type of operation is adopted for low engine speeds because they do not require a large air intake and the low lift of the valves causes, at the intake opening, an additional disturbance of the air flow of admission. So we have a more disturbed air flow and therefore a higher level of swirl, the mixture of air and fuel is then more homogeneous. In the case of a high engine speed requiring a large supply of air, the opening of the valves is increased, or even brought to the maximum. It is necessary to have a large air intake for which the level of swirl will be decreased, but allowing to have a higher permeability. Thus for a very high engine speed will have a valve lift set to the maximum.

  The accesses (8, 8 ') of the exhaust ducts (2, 2') are made symmetrically with respect to the central axis of the combustion cylinder (9). The fact of having symmetrical duct access positions (1, 1 ', 2, 2') in the cylinder head (3, 3 ') allows a distribution of the intake ducts (1, 1') and of homogeneous exhaust (2, 2 ') at the cylinder head (3, 3'). On the other hand, during the exhaust phase carried out before the intake phase, a circular movement of the residual gas is created due to the exhaust through the ports (8, 8 ') of the conduits (2, 2'). exhaust made in the cylinder head (3, 3 ') symmetrically and diametrically opposite. In addition, the direction of the inlet ducts (1, 1 ') and the exhaust ducts (2, 2') is designed so that the vortices created during the intake and during the exhaust have a same direction of rotation. During the exhaust cycle, the swirling motion of the gas inside the combustion chamber is thus started in the same direction as the vortex created during the intake. It is possible by using this admission system combined or not with a symmetrical exhaust system as described above, to add a scan cycle to evacuate the volume of residual gas after combustion.

  The intake ducts (1, 1 ') are designed so that they do not have a salient angle. The airflow is controlled so that it can add a disturbance or not. At high speed, when the disturbance is removed in the intake duct (1, 1 '), there is no loss of load. In one exemplary embodiment, only one of the ducts or the two intake ducts have a shape whose extension is tangential to the wall of the combustion chamber. The inlet ducts may thus have a rectilinear shape, as shown in FIG. 1, or a curved or even helical shape. In another exemplary embodiment, one of the ducts or the two intake ducts have a helical shape and open into the combustion chamber non-tangentially to the wall of the combustion chamber although the access of the duct or conduits The inlet is located on the periphery of the combustion chamber.

  It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration, but may be modified within the scope defined by the scope of the appended claims, and the invention should not be limited to the details given above.

Claims (11)

-8 CLAIMS   An optimized and variable aerodynamic intake system associated with a combustion chamber (9) comprising at least two admission ducts (1, 1 '), each having an access (7 and 7' respectively). ), opening into the combustion chamber (9), the opening of which is controlled at least by an intake valve, the two ports (7, 7 ') of the inlet ducts (1, 1') being diametrically opposite. , characterized in that it comprises first means of variation of the aerodynamic level associated with each of the ducts (1, 1 ') of admission, made by a lifting variable height of the intake valves, and in that the accesses (7, 7 ') of the intake ducts (1, 1') are offset radially with respect to the center of the combustion chamber (9), to control the variation of the aerodynamic level for at least the same speed of the motor.   2. An intake system according to claim 1 characterized in that the accesses (7, 7 ') of the ducts (1, 1') for admission into the combustion chamber (9) are placed as close as possible to the periphery. of the combustion chamber (9) so that there is a functional clearance (J) between the periphery of the combustion chamber (9) and the periphery of the ports (7, 7 ') of the ducts (1, 1 ') intake, allowing the intake valves to operate.   3. intake system according to one of claims 1 to 2, characterized in that second means for varying the aerodynamic level are formed by two valves (6, 6 ') shutters each disposed in a conduit (1, respectively 1 ') inlet, upstream of the access (7, 7' respectively) to the combustion chamber (9).   4. intake system according to claim 3, characterized in that the intake system is coupled with two exhaust pipes (2, 2 ') opening into the combustion chamber (9) by two ports (8, respectively 8 ') whose opening is each controlled by an exhaust valve, the ports (8, 8') of the conduits (2, respectively 2 ') exhaust being diametrically opposed.   5. An intake system according to claim 4, characterized in that the axis joining the center of access (8, 8 ') of the ducts (2, 2') exhaust forms a right angle with the axis joining the access center (7, 7 ') of the ducts (1, 1') of admission.   6. An intake system according to claim 4 or 5, characterized in that at least one inlet duct (1, 1 ') opens into the combustion chamber (9) in a direction tangent to the wall of the chamber. (9) combustion.   7. An intake system according to one of claims 4 to 6, characterized in that at least one inlet duct (1, 1 ') opens into the combustion chamber (9) in a helical path.   8. intake system according to one of claims 4 to 7, characterized in that the angle formed by the valves (6, 6 ') shutters relative to the axis of the duct (1, respectively 1') is controlled by first and second control means control the variable lift of the valves depending on the speed.   9. An intake system according to claim 8, characterized in that above a determined high speed, the first means control the angle of the valves (6, 6 ') to 0 and the second means control the lift of the valves at most.   10. An intake system according to claim 8 or 9, characterized in that below a determined low speed the first means control the angle of the valves (6, 6 ') at a determined maximum angle and the second means control the valve lift to a minimum.   11. Combustion process for an internal combustion engine using an intake system according to one of claims 1 to 8, characterized in that it comprises a scanning cycle.