FR2948728A1 - METHOD FOR CONTROLLING THE FLOW OF AN INTAKE FLUID FOR AN INTERNAL COMBUSTION ENGINE AND ENGINE FOR IMPLEMENTING SAID METHOD - Google Patents

Abstract

The invention relates to a method for controlling the flow of an intake fluid for an internal combustion engine comprising at least one inlet pipe (6) for admitting said fluid with a curved end portion (A) opening into a cylinder engine (1), an injection means (14) for an additional fluid, the curved end portion (A) being shaped to impart to the intake fluid a swirling motion (T) base in the next engine cylinder (1) a main axis of rotation (YY) substantially perpendicular to that of the driving cylinder (1), characterized in that the additional fluid is injected through at least one outlet section (13) disposed upstream of the end portion ( A) curve, with a predetermined injection speed, so as to modify the intensity of the vortex movement (T) basic by a disturbance of the boundary layer of the intake fluid. The invention also relates to an engine for implementing said method.

Description

A method of controlling flow of an intake fluid for an internal combustion engine and engine for carrying out said method.

TECHNICAL FIELD OF THE INVENTION The invention relates to internal combustion engines, and more particularly to the control of combustion air intake.

Technological background Since the constraints on European and international standards on pollutant and greenhouse gas emissions are becoming more and more severe, it is more important than ever to look for new ways to limit emissions at the source of the emissions. internal combustion engines. At the heart of this problem, the combustion system and its environment (aerodynamics, injection system ...) must meet new challenges in terms of efficiency and control.

In the case of internal combustion engines, this efficiency is strongly influenced by better control of the preparation of the mixture and the aerodynamic structures of the flow. Combustion, its tolerance to highly diluted or poor mixtures and the reduction of exhaust emissions are then directly related to the ability to control these processes.

To arrive at such results, it is known to generate a strong turbulence in the combustion chambers. To do this, a tumbling vortex movement is created in the driving cylinder, the main axis of rotation of which is substantially perpendicular to that of the driving cylinder, or a so-called swirling swirling movement whose axis of rotation is substantially around the axis of rotation. longitudinal axis of the engine cylinder.

Many devices have been proposed to create and / or intensify these swirling movements.

Among these devices, document FR2761406 discloses a direct injection internal combustion engine comprising an intake manifold for bringing a flow of combustion air into a combustion chamber. The intake manifold is shaped geometrically to print, by the forced guidance of the combustion air flow in the curved end portion of the intake manifold, a swirl-like swirl motion in the engine cylinder. The intake manifold further comprises a device for supporting the formation of the swirling motion. Said device comprises, on the one hand, the injection into the combustion air stream of an additional incoming air flow. Alternatively, the device may also include suction of an additional outgoing air stream. The additional air flows are supplied by air supply ducts and distributed in a plurality of partial flows through inlet orifices and outlet orifices arranged in the form of a ring around the periphery of the intake duct. inlet ports being approximately opposite the outlet ports, remote from the intake valve, in the curved end portion of the intake manifold. The additional incoming and outgoing air flows are supplied to the orifices by respective air supply ducts and the control of the flow rates of these additional air flows passing through the ducts is effected by control flaps mounted in said ducts. .

The deviation of the combustion air flow is obtained by virtue of the fact that the vector resulting from the directions of the additional fluid flows in the intake manifold is oriented in the direction of the swirling motion to be generated. The additional flows are brought to the side of the combustion air flow which is placed at the rear with reference to the direction of the swirling motion. Thus, the resulting vector of the directions of the additional fluid flows is oriented so as to intensify and support, by printing an additional kinetic moment, the rotational movement of the combustion air flow.

However, on the one hand, such a device for controlling the flow rate by adjustment flap, does not allow precise quantitative regulation of the flow rates of the injected additional flows. On the other hand, such a control means by adjustment flap does not make it possible to regulate the intensity of the precise swirling movement because it is not able to follow the variations of the operating points with a short response time. .

In addition, this device is dedicated to the amplification of a swirling air movement around the longitudinal axis of the so-called swirl cylinder, the document FR2761406 does not propose an embodiment and says nothing concerning the controlling a tumble-type swirling air movement about a main axis of rotation substantially perpendicular to that of the engine cylinder.

The invention aims to overcome the aforementioned drawbacks by proposing a new process capable of finely and reactively controlling a tumbling vortex movement.

The invention therefore relates to a flow control method of an intake fluid for an internal combustion engine comprising at least one intake manifold of said fluid with a curved end portion opening into a driving cylinder, means for injection of an additional fluid, the curved terminal portion being shaped to impart to the intake fluid a basic swirling motion in the engine cylinder along a main axis of rotation substantially perpendicular to that of the engine cylinder, characterized in that the additional fluid is injected, through at least one outlet section disposed upstream of the curved terminal portion, with a predetermined injection speed, so as to modify the intensity of the basic swirling motion by a disturbance of the boundary layer of the intake fluid. Indeed, the principle here is not to seek to print an additional kinetic moment to the intake fluid entering the engine cylinder by a driving effect as in the prior art, which requires a high additional air flow , but to generate a small disturbance which by its natural amplification will have an impact on the entire flow of the intake fluid. The control of the swirling motion according to the invention is therefore done here with less effort.

Moreover, the invention may comprise one or more of the following characteristics: the intake fluid flowing into the intake manifold with a determined speed of flow, the intensity of the basic swirling motion is reduced for a ratio between the injection speed and the flow rate of the intake fluid below a critical threshold. Indeed it has become apparent that the relationship between the flow rate of the intake fluid and the injection speed is decisive in the control of vortex movement.

on the other hand, the intensity of the basic vortex movement is increased for a ratio between the injection speed and the flow rate of the intake fluid greater than the critical threshold. - The injection speed is adapted during a running cycle of the engine. Indeed, especially during the intake phase, the flow rate of the intake fluid entering the engine cylinder is variable. By adjusting the injection speed, this makes it possible not to disturb the flow when it is not necessary or to control the intensity of the disturbance by adjusting the injection speed to the state of the flow.

Furthermore, the subject of the invention is also an internal combustion engine comprising at least one intake manifold with a curved end portion opening into a driving cylinder, the curved end portion being shaped to impart to the intake fluid a swirling movement. base in the engine cylinder along a main axis of rotation substantially perpendicular to that of the engine cylinder, means for injecting an additional fluid, means for controlling and calculating the injection means as a function of engine operating points , characterized in that it comprises at least one outlet section disposed upstream of the curved end portion through which the additional fluid is injected.

In addition, the motor implements the method of the invention.

Preferably, the engine operating parameters are chosen from at least one of the following parameters: the engine speed, the engine load, these two parameters are in fact of first order in the control of the swirling motion.

the output sections can in particular be circular with a diameter of between 0.5 and 1 mm, in order to obtain micro-jets making it possible to generate high injection speeds for low airflows and to target the disruption of the injection fluid flow at the injection point at the boundary layer.

the outlet sections are distributed in a plane perpendicular to the flow of the intake fluid and separated by a distance of between 1 and 5 times the diameter of said outlet sections. This arrangement makes it possible to generate one or more disturbances at the periphery of the tubing, in the boundary layer.

the exit sections may be rectangular with a width of between 0.4 and 2 mm and a length of between 1 and 10 times the width of said exit sections. This arrangement makes it possible to create a continuous disturbance on a portion of the periphery of the tubing.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which: - Figure 1 is a representation schematic of an internal combustion engine with an air jet flow control device. - Figure 2 is a schematic representation of the flow lines of the intake fluid into the intake manifold without additional air injection. - Figure 3 is a schematic representation of the flow lines of the intake fluid in the intake manifold with an additional air injection into the boundary layer having the effect of making the current lines re-stick. FIG. 4 is a schematic representation of the flow lines of the intake fluid in the intake manifold with an additional air injection into the boundary layer having the effect of massively loosening the current lines. - Figure 5 is a schematic representation of distribution of outlet sections in the intake manifold. - Figure 6 is a detail of the geometric parameters for circular output sections. - Figure 7 is a detail of the geometric parameters for rectangular output sections. FIG. 8 is a detail of the geometrical parameters for rectangular outlet sections in incidence with the main direction of the flow. - Figure 9 is a schematic representation of an additional air injection with a blow angle in a plane passing through a diameter of the tubing. - Figure 10 is a schematic representation of an additional air injection with a blow angle in a plane perpendicular to the flow of the intake fluid.

DETAILED DESCRIPTION In FIG. 1 is presented an internal combustion engine comprising at least one cylinder 1 of longitudinal axis XX, closed in the upper part by a cylinder head 2. Inside this cylinder is housed a piston 3 which makes it possible to delimit a combustion chamber 4 formed by the side wall of the cylinder 1, the part of the yoke 2 facing the piston 3 and the upper part of said piston 3 and inside which is admitted a fluid to achieve the combustion of a fuel mixture. The engine also comprises intake means 5, generally carried by the cylinder head 2, which comprise at least one intake manifold 6 opening through an orifice 7 in the combustion chamber 4.

At the orifice 7 is further inserted in the cylinder head 2, a valve seat 8 whose central bore corresponds to the orifice 7 and which is used with an intake valve of which only the general axis 9 is shown in Figure 1 for reasons of clarity. The intake manifold 6 has an end portion A of curved tubing whose concavity is opposite to the cylinder. The intake manifold 6 thus comprises a lower surface 10 close to the cylinder and an extrados 11 opposite the lower surface.

In addition, the engine comprises exhaust means, of which only the general center line 12 is shown in FIG. 1 for the sake of clarity, which makes it possible to evacuate the flue gases contained in the combustion chamber 4.

The conformation curves the end portion A of the intake manifold makes it possible to introduce the intake fluid into the combustion chamber 4 in such a way that this fluid has a circular base movement T around an axis of rotation YY which is substantially perpendicular to that XX of the engine cylinder. This swirling motion is better known by the term tumble.

The fluid admitted into the combustion chamber 4 may as well be a supercharged or non-supercharged air introduced through the pipe 6 to be then mixed with a fuel that a fuel-based fuel mixture mixed with supercharged air or not, possibly added with recirculated flue gas.

Preferably, the intake manifold 6 comprises at least one outlet section 13, upstream of the curved end portion A, through which an additional fluid is injected. Advantageously, the additional fluid is, for reasons of simplicity, air.

The outlet sections 13 are connected to at least one injection means 14 of an additional fluid, preferably of the fluidic micro-actuator type capable of generating an air flow. Such a micro-actuator 14 is advantageously a device belonging to the known family of microsystems or MEMS (for the acronym of Micro Electro Mechanical Systems). With reduced size, such micro-actuators can advantageously be arranged at the outlet of the intake manifold 6. Indeed, conventional mechanical solutions do not allow in particular to meet the constraints of space, low energy consumption and low production cost.

The air jets can be generated collectively, a micro-actuator 14 feeding all the output sections 13. The air jets can also be generated more individually, a micro-actuator 14 feeding each output section 13 or a part of the sections of exit 13.

It is expected that the operation of the micro-actuator 14 is controlled by a control and calculation means 15. The control and calculation means may be an electronic control unit also called ECU.

Figure 2 is a visualization of the flow lines 17 of the intake fluid flowing into the intake manifold, without additional air flow, so without flow control. The intake fluid flows in the direction of the arrow F. In the rectilinear portion 18, the streamlines are substantially parallel, including near the wall of the tubing. At the passage of the fluid in the end portion A of the tubing, on the intrados side 10, the streamlines near the wall of the tubular take off to form a swirl zone 19. In this case, the swirling motion T base is imposed by the geometric conformation of the intake manifold 6.

FIG. 3 shows a visualization of the flow lines 17 of the intake fluid flowing into the intake manifold with a flow rate U0, with an additional flow of injected air, on the lower side 10, with a flow rate U; not; in the rectilinear portion 18, at the injection point 20, upstream of the curved end portion A of the tubing 6.

According to the invention, the purpose of injecting air jets is to obtain an interaction with the boundary layer L of the flow in order to modify its properties. Indeed, it appeared that a small disturbance of the boundary layer L was sufficient to significantly modify the flow downstream of said disturbance. The term "boundary layer" refers to the slowed-down fluid layer in the vicinity of the wall of the pipe 6. This boundary layer L has a variable thickness depending on whether the flow is laminar or turbulent and has an order of magnitude of one millimeter.

The operating principle is therefore not here to seek to print at the injection point 20 an additional pulse to all of the intake fluid entering the combustion chamber 4, which requires an air flow rate additional important and therefore a voluminous and bulky actuator 14. The operating principle here is to print at the boundary layer L a small initial disturbance which, developing naturally, will ultimately impact the entire flow of the intake fluid. Indeed, opening into the boundary layer L, the additional air jet is at the origin of contra-rotating longitudinal vortices which develop in the tubing 6, downstream of the injection point 20.

Flow rate means the speed of the flow obtained by the ratio between the volume flow rate and the passage section of the flow. In the case illustrated in FIG. 3, the ratio between the injection speed U; nj and the speed of the flow Uo is less than a critical threshold Sc. The effect of the additional air flow is here to enable pick up the power lines. Indeed, the disappearance of the swirl zone 19 visible in FIG. 2 and a substantially parallel hold of the current lines in the terminal portion A of the curved pipe are observed. Thus, a portion of the current lines 17 being folded towards the intrados 10 of the intake manifold 6, the intensity of the swirling movement T (FIG. 1) is reduced.

FIG. 4 shows a visualization of the current lines 17 of the intake fluid flowing in the intake manifold with a flow rate Uo, with an additional flow of injected air, on the intrados side 10, with a flow rate U; nj in the rectilinear portion 18, at the injection point 20, upstream of the curved end portion A of the tubing 6. In this case, the ratio between the injection speed U; nj and the speed of the injection flow Uo is greater than the critical threshold Sc. In this case, the effect of the additional flux is here to accentuate the takeoff of the current lines with respect to the case without the addition of additional flux illustrated in FIG. 2. Immediately upstream of the point d injection forms a vortex 21 which acts as an obstacle to the current lines. The intake fluid is thus deviated massively in the direction of the extrados 11 of the tubing. It should be noted, however, that despite the presence of this vortex 21, the flow in the curved end portion A of the tubing does not present a swirl zone 19 as illustrated in FIG. 2. Thus, a portion of the stream lines 17 being deflected towards the upper surface 11 of the intake manifold 6, the intensity of the swirling motion T (FIG. 1) of determined base tumbler imposed by the geometric conformation of the intake manifold 6 is increased.

Advantageously, the critical threshold Sc is between 3 and 8. Indeed, tests have shown that for a ratio between the injection speed U; nj and the flow velocity Uo of the order of 3, a while for a ratio between the injection speed Uinj and the flow velocity Uo of the order of 8, a free separation is ensured.

Advantageously, the ECU 15 comprises a map 16 containing, as a function of engine operating parameters, the different values of injection speed U; nj of additional air flow to be injected. Preferably, the engine operating parameters are chosen from at least one of the following parameters: the engine speed N, the engine load C.

Such mapping 16 may be carried out beforehand on engine bench or by numerical simulation and then stored in the ECU 15.

Figure 5 illustrates an example of distribution of outlet sections 13 in the intake manifold 6, in a row on the side of the intrados 10 of said manifold, perpendicular to the flow of the intake fluid. However, it is possible to arrange the outlet sections 13 over the entire perimeter of the tubing 6 and thus have the possibility, as needed, of generating air jets at the appropriate locations along the perimeter of the tubing 6. It can also be provided to intensify the disturbance of the boundary layer by arranging the outlet sections 13 in several successive rows substantially perpendicular to the flow of the intake fluid in order to impact the boundary layer L over a larger area, always in upstream of the terminal portion A curve of the intake manifold 6.

FIG. 6 shows a detail of the geometry of the output sections 13. The geometrical parameters of the output sections 13 are intrinsic to the system and must be defined a priori at the time of engine design. However, as an indication, for an intake pipe 6 for an automobile combustion engine having a diameter of magnitude of 2 cm upstream of the intake valve, advantageously, the outlet sections 13 are circular and have a diameter D between a few hundred microns and a few millimeters and preferably between 0.5 mm and 1 mm.

Advantageously, the outlet sections 13 distributed along a plane YOZ (shown schematically in FIG. 10) perpendicular to the flow of the intake fluid and are separated by a distance De, determined here by the distance between the centers of two sections of output 13 successive, between 1 and 5 times the diameter D of the output section.

Figures 7 and 8 show variants based on rectangular outlet sections 13 of length Lo and width la. Preferably, according to this geometry of exit sections 13, the dimensions of the width la are between 0.4 and 2 mm for Lo lengths of exit sections 13 of the order of 0.1 to 10 times the width of the width. . In addition, as illustrated more particularly in FIG. 8, the outlet sections 13 can be arranged in incidence, that is to say with a major axis forming an angle α with respect to the principal direction of the materialized flow. by the arrow F.

The direction of the additional air flows may be adjusted to form, relative to the wall of the tubing 6, an angle 8 in a plane XOZ passing through the diameter of the tubing 6 as shown in Figure 9. The angle 8 may be between 0 and 180 °. However, preferably the angle 8 substantially forms a right angle with respect to the wall of the tubing 6.

The direction of the additional air flows can be further adjusted to form, relative to the wall of the tubing 6, an angle θ in a YOZ plane perpendicular to the flow (Figure 10). Advantageously, the direction of the additional air flows is substantially perpendicular to the wall of the tubing 6. The angle θ can be between 0 and 180 °. However, preferably the angle θ forms a substantially right angle with respect to the tangent to the wall of the tubing 6.

The position of the output sections 13 is a parameter to be taken into account in determining the effectiveness of the system and its integration. Indeed, depending on the engine and geometric constraints, we will integrate the output sections at a position Xj upstream of the curved portion of the tubing 6 (Figure 2) which will present the best compromise.

Advantageously, the additional air flows can be continuous or pulsed. Advantageously, the injection speed U; nj is adapted during a motor cycle and in particular during the intake phase. In fact, by adapting the injection speed U; nj to the speed Uo of the intake fluid in the tubing 6, the intensity of the disturbance at the injection point 20 is constantly monitored and consequently the intensity of the swirling motion T.

The invention has the advantage of allowing effective active control of the flow in the emission pipe 6 and the intensity of the swirling movement T by acting at a distance from the admission orifice 7 of the intake fluid, more judiciously upstream of the curved terminal portion A of the tubing 6, for an optimum effect on the swirling motion T from a low initial disturbance, which furthermore allows the installation of the fluidic micro-actuator (s) 14 in an area easier to instrument.

Claims (9)

Revendications1. A method for controlling the flow of an intake fluid for an internal combustion engine comprising at least one intake manifold (6) for said fluid with a curved end portion (A) opening into a driving cylinder (1), a means for injecting (14) an additional fluid, the curved end portion (A) being shaped to impart to the intake fluid a swirling motion (T) base in the engine cylinder (1) along a main axis of rotation (YY) substantially perpendicular to that of the driving cylinder (1), characterized in that the additional fluid is injected, through at least one outlet section (13) disposed upstream of the curved end portion (A), with a predetermined injection speed (A), so as to modify the intensity of the basic vortex movement (T) by a disturbance of the boundary layer (L) of the intake fluid. 2. Method according to claim 1, the intake fluid flowing into the intake manifold with a determined speed (Uo), characterized in that it reduces the intensity of the vortex movement (T) base for a ratio between the injection speed (Un) and the flow rate of the intake fluid (Uo) below a critical threshold (Sc). 3. Method according to claim 2, characterized in that it increases the intensity of the vortex movement (T) base for a ratio between the injection speed (U; n1) and the flow rate of the intake fluid. (Uo) greater than the critical threshold (Se). 4. Method according to one of the preceding claims, characterized in that the injection speed (Uni) is adapted during a running cycle of the engine. 5. Internal combustion engine comprising at least one inlet pipe (6) with a curved end portion (A) opening into a driving cylinder (1), the curved end portion (A) being shaped to print to the intake fluid a basic vortex movement (T) in the engine cylinder (1) along a main axis of rotation (YY) substantially perpendicular to that of the engine cylinder (1), means for injecting (14) an additional fluid, means (15) for controlling and calculating the injection means (14) as a function of engine operating points, characterized in that it comprises at least one outlet section (13) arranged upstream of the terminal portion (A) ) curve by which the additional fluid is injected and in that it implements the method according to one of claims 1 to 4. 6. Internal combustion engine according to claim 5, characterized in that the engine operating parameters are selected from at least one of the following parameters: the engine speed (N), the engine load (C). 7. Internal combustion engine according to claim 5 or 6, characterized in that the output sections (13) are circular with a diameter (D) between 0.5 and 1mm. 8. Internal combustion engine according to claim 7, characterized in that the outlet sections (13) are distributed in a perpendicular plane (YOZ) to the flow of the intake fluid and separated by a distance (De) included between 1 and 5 times the diameter (D) of said outlet sections (13). 9. Internal combustion engine according to any one of claims 5 or 6, characterized in that the outlet sections (13) are rectangular with a width (la) between 0.4 and 2 mm and a length (Lo) between 1 and 10 times the width (la) of said output sections (13).