EP1861598A2

EP1861598A2 - Device for accelerating a turbocharging unit at low speeds of a reciprocating engine and reciprocating engine comprising same

Info

Publication number: EP1861598A2
Application number: EP06726100A
Authority: EP
Inventors: Jean Frédéric Melchior
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-03-22
Filing date: 2006-03-17
Publication date: 2007-12-05
Also published as: FR2883601A1; WO2006100370A3; FR2883601B1; WO2006100370A2; US20080066466A1

Abstract

The invention concerns a device for accelerating a turbocharging unit at low speeds of a reciprocating engine (1) operating in accordance with a four-stroke cycle and comprising at least one cylinder (1a) equipped with at least one intake valve (2) connected to an intake manifold (3) and with at least one exhaust valve (4) connected to an exhaust manifold (5), said turbocharging unit comprising at least one turbocharger (10) including an air compressor (11) feeding the intake manifold (3) and a radial turbine (12) fed by the exhaust manifold (5) and driving the compressor (11). The device comprises an aerodynamic ejector (20) drawing a propellant stream on the exhaust gases of the engine (1) and a stream driven on the air delivered by the compressor (11) and forming a mixed stream which feeds the turbine (12) of the turbocharging unit.

Description

Device for accelerating a turbocharger unit at low speeds of an alternating motor and reciprocating engine comprising such a device.

The present invention relates to a device for accelerating a turbocharging unit at low revolutions of an alternating engine operating on a four-stroke cycle, and an alternating engine equipped with such an acceleration device of the turbocharger unit. .

The invention also relates to methods of accelerating a turbocharger unit at low speeds of an alternating engine operating in a four-cycle cycle.

Turbocharged four-stroke diesel engines, such as those described in French patent applications 03 03 728 and 05 01 156 in the name of the Applicant, are characterized by a high-pressure turbocharger group adapted for a lower rotational speed. at their minimum speed of use for the purpose of recycling a flue gas flow under all operating conditions of the engine. The turbocharger unit tuning speed is the rotational speed of the engine where the gas pressure upstream of the turbine of the turbocharger unit crosses the air pressure downstream of the compressor of this turbocharger unit.

The turbocompression groups known hitherto are but adapted to engines of small motor vehicles such as, for example of the order of 1500 cm ³ . In fact, the miniaturization of the turbocharger groups finds its limits for a rotor diameter close to 30 mm. For such a dimension, no variable geometry can be envisaged without seriously compromising the isentropic compression and expansion efficiencies.

Over-sizing of high-pressure turbocharger units is particularly disadvantageous for engines equipped with a particulate filter, especially when it is arranged upstream of the turbine of said turbocharger unit. Indeed, in this case, the high pressure turbine does not benefit from the pressure waves to accelerate from the idle speed of the engine. In addition, no gas flow can be recycled to the intake of the engine at very low speed to limit emissions of NOX nitrogen oxide and maintain the catalyst temperature of the particulate filter.

The automakers have, to improve the acceleration of the turbocharger group at low engine speeds, undersized the turbine of this turbocharging unit and associated this turbine to a discharge valve or a variable section valve. But, the undersizing of the turbine is limited by the maximum power of the engine.

The manufacturers of turbocharger units have also proposed an electric or hydraulic drive of the turbocharger at low operating speeds of the engine. But, this expensive solution is not powerful enough for high boost rates.

The method described in French Patent Application No. 03 03 728 also in the name of the Applicant makes it possible to solve this problem for engines having a displacement greater than 1900 cm ³ .

The object of the present invention is to solve this problem by proposing a device capable of generating a flow rate of recycled flue gases at lower speeds than the adaptation speed and of accelerating the high pressure turbocharger unit without having the compressor of this group pumped out. said schemes.

The subject of the invention is therefore a device for accelerating a turbocharger unit at low speeds of an alternating engine operating on a four-stroke cycle and comprising at least one cylinder provided with at least one connected intake valve. to an intake manifold and at least one exhaust valve connected to an exhaust manifold, said turbocharger unit comprising at least one turbocharger having an air compressor supplying the intake manifold and a fed radial turbine by the exhaust manifold and driving the compressor, characterized in that it comprises an aerodynamic ejector removing a propellant flow on the exhaust gas of the engine and a flow driven on the air delivered by the compressor and forming a mixed flow which feeds the turbine of the turbocharger unit. According to other features of the invention:

the ejector comprises a mixer formed by the turbine feed volute extended upstream with respect to the flow direction of the mixed flow, by a substantially rectilinear portion of sufficient length to homogenize the mixture between the propellant flow and the driven flow,

the substantially rectilinear portion of the mixer is extended upstream by a substantially conical coaxial portion with an apex angle of between 20 and 40 ° communicating with the exhaust manifold, the ejector comprises a cylindrical tube whose outer wall is provided, at one of its ends, with a conical portion intended to cooperate with the conical portion of the mixer, said tube being displaceable coaxially with said mixer so that the conical portions form an annular convergent nozzle of variable speed propellant flow, - the cylindrical tube is slidably mounted in a guide formed in the wall of the exhaust manifold and communicates with the outlet of the compressor via a non-return valve preventing the flow of burnt gases from the exhaust manifold to the compressor, - the nozzle section varies between the inlet section of the scroll of the turbine and one-third of said entrance section,

the cylindrical tube is integral, at its end opposite to that provided with the conical portion, with a control piston slidably mounted in a cylinder which determines, on one side of the piston, a first chamber subjected to the pressure of the delivered air; by the compressor and, on the other side of this control piston, a second chamber comprising a spring acting on said piston, said air pressure delivered by the compressor tending to open the nozzle of ejector and the force of the spring tending to close this nozzle, and

the second chamber communicates with a vacuum pump to modify or neutralize the spring force,

the turbocharger unit comprises a second turbocharger comprising a turbine permanently communicating with the an exhaust manifold and a compressor communicating permanently with the intake manifold and the compressor communicates with the intake manifold via a non-return valve.

The invention also relates to an alternating engine operating in a four-stroke cycle and comprising a turbocharger unit, characterized in that it comprises an acceleration device of the turbocharging unit at low engine speeds, as previously mentioned. .

The invention also relates to a method for accelerating a turbocharger unit at low speeds of an alternating engine operating in a four-stroke cycle and comprising an acceleration device of said turbocharging unit as previously mentioned, characterized in that it consists in closing the nozzle of the aerodynamic ejector.

The invention also relates to a method for accelerating a turbocharger unit at low speeds of an alternating engine operating in a four-stroke cycle and comprising a turbocharger group acceleration device as previously mentioned, and a flue gas recycling duct, characterized in that it consists in obstructing said recycling duct, the nozzle nozzle section of the ejector being fixed. The invention also relates to a method of accelerating a turbocharging unit at low speeds of an alternating engine, said group comprising two turbochargers, characterized in that it consists of:

- between the idling speed and an engine N1 where the intake pressure P2 reaches the desired value according to the burned fuel flow, to maintain the relief valve, the non-return valve and the nozzle closed so that the engine is supplied with air by the only compressor of the turbocharger driven by the turbine of this turbocharger which receives all the gases burned in the engine, and

between this regime N1 and a regime Nt where the discharge pressure of the compressor of the turbocharger reaches the admission pressure

P2, to maintain this inlet pressure P2 at its set point by the progressive opening of the nozzle, the relief valve and the anti-tamper valve. return remaining closed so that the engine is supplied with air by the only turbocharger compressor driven by the turbine which receives only a fraction of the gases burned in the engine whose complement feeds the turbine by the aerodynamic ejector which drives the compressor discharging exclusively into the turbine via said aerodynamic ejector.

Other features and advantages of the invention will become apparent from the description which follows and with reference to the appended drawings, in which:

- Figure 1 is a diagram of a cylinder of an alternating engine equipped with an acceleration device of a turbocharger group to a turbocharger,

FIG. 2 is a diagram of a variant of a cylinder of an alternating material equipped with a device for accelerating a turbocharger group to a turbocharger; FIG. 3 is a diagram of a cylinder of a an alternating engine equipped with a turbocharger unit with two turbochargers according to the state of the art, and

- Figure 4 is a diagram of a cylinder of an alternating engine equipped with a turbocharger group with two turbochargers and equipped with an acceleration device of a two-turbocharger turbocharging unit.

In the figures, there is shown schematically a motor 1 which comprises at least one cylinder 1a provided with at least one intake valve 2 connected to an intake manifold 3 and at least one exhaust valve 4 connected to an exhaust manifold 5. This engine 1 operates in a four-stroke cycle, preferably without crossing the valves 2 and 4, to prevent direct communication between the intake manifold 3 and the exhaust manifold 5.

In FIG. 1, the engine 1 is supercharged by a turbocharger unit comprising a turbocharger generally designated by the reference 10 and comprising an air compressor 11 supplying the intake manifold 3 and a radial turbine 12 fed by the collector. exhaust 5 and driving the compressor 11 by mechanical means shown schematically in the figure by the dash line 13. The engine 1 is also equipped with a duct 6 for recycling burnt gases, also called EGR conduit, and provided with a adjustment valve 7, commonly called EGR valve. The engine 1 is equipped with an acceleration device of the turbocharger unit at low speeds of this engine and which comprises an aerodynamic ejector generally designated by the reference 20.

In a general manner and as will be described later, the aerodynamic ejector 20 takes a propulsive flow on the exhaust gas of the engine 1 and a flow driven on the air delivered by the compressor 11 and forms a mixed flow which feeds turbine 12 of the turbocharger 10.

The aerodynamic ejector 20 comprises a mixer 21 which is, in the exemplary embodiment shown in FIG. 1, formed by the supply volute of the turbine 12. This mixer 21 is extended upstream with respect to the direction of rotation. flow of the flow mixed by a substantially straight portion 22 which has a length sufficient to homogenize the mixture between the propellant flow and the driven flow of the aerodynamic ejector 20. This substantially rectilinear portion 22 is extended by a substantially conical coaxial portion 23 of which the Angle at the apex is for example between 20 and 40 °. The portion 23 communicates with the exhaust manifold 5.

In the embodiment shown in Figure 1, the ejector 20 also comprises a cylindrical tube 24 which forms an inner conduit 25 and whose outer wall is provided at one of its ends 24a with a conical portion 24b intended to cooperate with the conical portion 23 of the mixer 20.

The cylindrical tube 24 is slidably mounted in a guide 26 which has an inner section of shape conjugated to the outer wall of the cylindrical tube 24. This cylindrical tube 24 is displaceable coaxially with the mixer 21 so that the conical portions, respectively 23 and 24b, form an annular converging nozzle 30 of variable section for accelerating the propellant flow. The cylindrical tube 24 communicates with the outlet of the compressor 11 via a bypass duct 31 via a nonreturn valve 32 which prevents the flow of flue gases from the exhaust manifold 5 to the compressor 11. For this , the non-return valve 32 is associated with a spring 33 whose restoring force tends to apply the valve 32 against its seat 32a to close the bypass duct 31.

The cylindrical tube 24 has at its end 24c opposite to that provided with the conical portion 24b, a control piston 35 slidably mounted in a cylinder 36 determining on one side of the piston 35, a first chamber 37 subjected to the pressure of the air delivered by the compressor 11 through the bypass conduit 31 and, on the other side of the control piston 35, a second chamber 38 having a spring 39 acting on the piston 35. The air pressure delivered by the compressor 11 and passing through the bypass duct 31 tends to open the nozzle 30 by moving through the piston 35, the cylindrical tube 24 while the force exerted by the spring 39 on the piston 35 tends to close this nozzle 30.

In the embodiment shown in Figure 1, the second chamber 38 communicates via a pipe 40 with a vacuum pump, not shown, which allows, in some cases to change or neutralize the force of the spring 39 The section of the nozzle 30 preferably varies between the turbine scroll inlet section 12 and the third of said inlet section.

The four-stroke engine without crossing valves is capable of generating a flue gas flow proportional to its speed and the density of the gases in the intake manifold 3. The pressure of the gases discharged by the engine 1 at a given speed depends only on the section of the exhaust port in this case, the distributor of the turbine 12.

To accelerate the compressor 11, the turbine 12 must receive a gas flow whose total pressure and / or the total temperature are greater than that of the air flow delivered by the compressor 11. The flow delivered by the compressor 11, equal to the flow that passes through the turbine 12, must also be greater than the pumping rate where the operation is unstable. To the regime of idle, the flow sucked by the engine 1 is below this minimum flow and the discharge pressure of the burnt gases is negligible given the oversizing of the turbine 12.

In the device of the invention shown in FIG. 1, the compressor 11 delivers in parallel in the intake circuit of the engine 1 and in the bypass duct 31 which supplies the turbine 12 directly. Thus, this turbine 12 is supplied simultaneously by the air coming from the bypass duct 31 and by the burnt gases discharged by the engine 1.

In the device according to the invention, the engine 1 is used as a compressed gas generator which propels a portion of the air flow delivered by the compressor 11 into the turbine feed volute 12 by means of the aerodynamic ejector 20. The hot gases accelerated by the nozzle 30 of this aerodynamic ejector communicate their momentum to the air delivered by the bypass duct 31 by means of the ejector 20 whose mixer 21 feeds the volute of the turbine 12. section of the nozzle 30 of the ejector 20 is adjustable which allows to control the ratio between the flow of propellants and the gas flow of the entrained air. The section of the nozzle 30 may be set in operation between a minimum value which allows the acceleration of the turbocharger unit and the desired flue gas recirculation flow rate at idle and the normal supply section of the turbine 12 of this group of turbines. turbocharging.

For idle operation, the nozzle 30 is set to its minimum section. The control valve 7 is open and adjusts the flow rates of recycled hot gases to dispose in the cylinder 1a of the amount of air just needed to burn the flow of maintenance fuel idling and an admission temperature as high as possible to limit noise and unburnt combustion. The richness is preferably regulated by the control computer of the engine 1. Under these conditions, the intake pressure in the intake manifold 3 is close to the atmospheric pressure and the exhaust pressure in the exhaust manifold 5 is slightly above atmospheric pressure. To increase the air pressure delivered by the turbocharger unit without changing the idling speed of the engine 1, simply close the control valve 7 without changing the section of the nozzle 30. The pressure in the exhaust manifold 5 increases as well as the speed of the jet emitted by the nozzle 30 which causes a flow of air through the bypass duct 31 to which it transfers its momentum in the mixer 21. The total pressure upstream of the turbine 12 being greater than the pressure delivered by the compressor 11, the latter accelerates to a maximum speed when the control valve 7 is closed. The engine 1 and supercharged at its idle speed, is likely to deliver torque to accelerate the vehicle.

When the engine 1 accelerates to reach the speed of adaptation, the nozzle 30 of the ejector 20 must be progressively opened up to the normal supply section of the turbine 12 to limit the pressure of the gases in the collector. 5. The percentage of air entrained to the turbine 12 then decreases to zero and the check valve 32 closes to prohibit a reflux of hot gas to the outlet of the compressor 11. This maneuver is regulated by the spring 39 which is supported on a face of the piston 35, the other face is subjected to the pressure delivered by the compressor 11. The calibration and the stiffness of the spring 39 fix the accessible air pressure levels in this control mode. This mode of regulation can be modified or neutralized by putting the chamber 38 which comprises the spring 39 in communication with a vacuum pump by a solenoid valve controlled three ways, not shown. The gradual opening of the nozzle 30 of the ejector 20 may be accompanied by a partial opening of the control valve 7 to maintain the recycled gas content to a desired value. Between the idle speed and a regime equal to twice the adaptation regime, the device according to the invention makes it possible to maintain a high rate of recycled gases and / or to deliver a high torque.

Preferably, the control valve 7 controls the recycled gas content and the nozzle 30 of the ejector 20 actuated by the piston 35 controls the wealth of combustion of the engine. An advantage of the device according to the invention is the control of the intake temperature which makes it possible to exploit reduced compression ratios in cold weather. Another advantage of the device according to the invention is the engine brake obtained by the simultaneous closing of the control valve 7 and the nozzle 30 of the aerodynamic ejector 20.

At each lift of the accelerator pedal driver, the nozzle 30 can close and the control valve 7 can open to supply the engine 1 with hot gases so as not to cool the after-treatment devices of the engines. exhaust gas.

If the driver wants to slow down the vehicle by pressing the brake pedal, it can firstly close the control valve 7 to increase the exhaust against pressure and create engine braking. The kinetic energy of the vehicle is then used to drive the turbocharger unit 10 and allows instant recovery after the deceleration.

The invention allows many engine operation control strategies that are familiar to those skilled in the art.

When the engine 1 is equipped with a flue gas recirculation duct 6 also called EGR duct, as shown in FIG. 2, the efficiency of the device according to the invention can be improved by heating the air supplying the ejector Via a conduit 31. A solution described in FIG. 2 is to place a heat exchanger

51 air / gas burned at an intersection of the conduit 31 and the duct 6. Generally, the duct 6 comprises a gas / water refrigerant 52 and a bypass duct 53 of said refrigerant. The exchanger 51 is in this case placed upstream of the refrigerant 52 and the bypass duct 53. Referring now to Figures 3 and 4, there will be described another application of the acceleration device of the turbocharger unit.

In addition to accelerating the compressor at low engine speeds, the acceleration device according to the invention is particularly advantageous in a sequential turbocharging unit which comprises two turbines and two compressors which are connected in parallel to relax the exhaust gases and compress the engine intake air. In such a configuration, the first turbocharger which comprises a turbine and a compressor, operates alone between the idle and an intermediate regime called Nt transition regime from which the second turbocharger which also comprises a turbine and a compressor, cooperates with the first to ensure the air supply of the engine. The activation of the second turbocharger, which poses problems similar to the acceleration at low revs, occurs at each revving and stopping occurs at each descent into regime. In urban or sport driving, the frequency of these transitions can be high and impose a difficult control of gas flow control valves.

In Figures 3 and 4, the common members of the previous embodiment have been designated by the same references.

FIG. 3 shows a known type of engine which comprises an intake duct 3 and an exhaust duct 5 and which is supercharged by a turbocharger unit comprising two turbochargers, respectively 60 and 70, each comprising a compressor , respectively 61 and 71, and a turbine, respectively 62 and 72.

The compressor 61 draws air into the atmosphere to discharge it permanently into the intake manifold 3 and the turbine 62 permanently communicates with the exhaust manifold 5 which feeds it with hot gases which it rejects towards the 'atmosphere. The compressor 71 draws air into the atmosphere to discharge it into the intake manifold 3 via a non-return valve 110. The turbine 72 communicates with the exhaust manifold 5 via a supply valve 8 controlled by an actuator δi.

The exhaust manifold 5 is provided with a discharge valve 9 to the atmosphere controlled by an actuator 91 and the intake manifold 3 is provided with a discharge valve 100 in the atmosphere located upstream of the valve 110 and controlled by an actuator 101. Between the idle speed and a regime N1, the valves and the valves 8, 9, 10 and 11 are closed and the entire exhaust flow feeds the turbine 62 which accelerates the compressor 61 to the P2 intake pressure desired. Between the N1 regime and a higher transition rate Nt, the air flow increases at constant pressure P2 gradually opening the discharge valve 9. The Nt regime must be sufficient for the engine 1 to suck up after the transition, a flow of air greater than the sum of the pumping rates of the two compressors, respectively 61 and 71. If the two compressors 61 and 71 are identical and the turbocharger 60 is adapted in the vicinity of the pumping line, the Nt regime is therefore higher at 2 N1.

From the Nt regime, the valve 8 opens to supply the turbine 72 while the discharge valve 9 closes to maintain the pressure P2. The compressor 71 accelerates rapidly by delivering through the regulated relief valve 10 to avoid pumping.

When the pressure of the compressor 71 reaches the pressure P2, the valve 11 opens, the relief valve 10 closes and the two compressors

61 and 71 share the air flow of the engine 1 in proportion to the section of the turbines 62 and 72. The relief valve 9 then resumes the regulation of the pressure P2 for the revs greater than Nt.

Since all these operations must take place in a few tenths of a second, the management of the actuators and the control of the actuators themselves, which manage the chronology of the operations, are of great complexity.

The purpose of the acceleration device according to the invention is to simplify the process of actuating the compressor 71 of the second turbocharger 70 and to make it contribute to the engine air flow from a lower Nt regime to the Nt regime. of the engine according to the state of the art previously described with respect to FIG.

The engine 1 equipped with the acceleration device of a turbocharger unit according to the invention is shown in FIG. 4.

The configuration of this engine is identical to the configuration of the engine shown in Figure 3 with the exception of the turbine supply circuit 72 of the second turbocharger 70 and the compressor discharge circuit 71 of the turbocharger to the valve against back 110. This turbine 72 is powered by an aerodynamic ejector 20 whose propellant flow is taken from the exhaust gas from the exhaust manifold 5 and whose driven flow is taken at the discharge of the compressor 71 through the conduit 31. This ejector aerodynamic 20 is identical to that described with respect to the first embodiment shown in Figure 1 except that the variable nozzle 30 can close completely and tightly and that the pressure acting on the control piston 35 of the nozzle 30 is not the discharge pressure P21 of the compressor 71, but that P2 of the compressor 61.

According to the embodiment shown in FIG. 4, the cylinder

36 determines on one side of the piston 35, a first chamber 38 subjected to the reference pressure Pr and, on the other side of this piston 35, a second chamber 381 subjected to the pressure P2, the chamber 37 remaining subjected to the pressure P21.

To prevent the discharge valve 9 from opening before the nozzle 30 is completely open, the supply duct 913 of the chamber 910 includes a shut-off valve 914 which opens only when the nozzle 30 is on its side. opening stop. In this embodiment, the supply valve 8 of the turbine 72 and the anti-pumping valve 100 of the compressor 71 of FIG. 3 are replaced by the aerodynamic ejector 20 and its non-return valve 32.

An example of a regulating device is shown in FIG. 4.

A reference pressure Pr is established in an enclosure 12 fed by the intake manifold 3 where the intake pressure P2 prevails by means of a pressure reducing valve 121 controlled by a control computer of the engine.

This chamber 12 communicates with the chambers 38 and 91 of the control actuators of the nozzle 30 and the discharge valve 9 to add to the springs 39 and 912, a variable setting force.

An operating mode of the plant shown in Figure 4 is described below during an acceleration of the engine. Between the idle and a N1 regime, the relief valve 9, the valve 110 and the nozzle 30 are closed and the entire exhaust stream feeds the turbine 62 which accelerates the compressor 61 of the turbocharger 60 to reach the pressure d desired P2 admission. Between the N1 regime and a Nt ₁ regime the air flow rate increases at constant intake pressure P2 by progressively opening the nozzle 30 which supplies the turbine 72. The turbocharger 70 accelerates progressively and the compressor 71 of this turbocharger 70 flow without pumping into the turbine 72 through the check valve 32 and the aerodynamic ejector 20. The pressure in the intake manifold 3 is equal to the desired inlet pressure P2 downstream of the check valve back 110 and equal to a pressure P21 lower than this intake pressure P2 upstream. Between the idle and the Nt regime, only the compressor 61 provides the air supply of the engine.

When the speed reaches Nt _1, the pressure P21 reaches the inlet pressure P2 and the non-return valve 110 opens. The compressor 71 begins to participate in the engine air supply.

Beyond the Nt regime, the nozzle 30 continues to open to regulate the intake pressure P2 until it is fully open. The contribution of the compressor 71 to the motor supply increases. At the end of the opening of the nozzle 30, the static pressure at its outlet crosses the inlet pressure P2 and the non-return valve 32 closes. The compressor 71 then ceases to flow into the ejector 20.

The transition being effected, the compressors 61 and 71 share the air flow and the intake pressure P2 is regulated by the relief valve 9.

An advantage of the invention lies in the progressiveness of the actuation of the turbocharger 70.

Another advantage is the reduction of the Nt transition regime. Indeed, no pressurized fluid is discharged to the atmosphere as in the installation according to the state of the art shown in Figure 2 where the relief valve 9 and the check valve 110 cooperate to avoid pumping. of the compressor 71 of the turbocharger 70. The flow of enthalpy required for to drive the two compressors 61 and 71 to their pumping rate, is therefore reached for a lower speed.

Furthermore, for each torque applied to the engine corresponds a quantity of fuel and an amount of air proportional to the intake pressure P2 desired to burn with a wealth determined by the mapping stored in an engine control computer.

The position of the accelerator pedal that requires a motor torque, orders this calculator intake pressure P2 regardless of the speed. According to a simple embodiment of the invention, the computer acts only on the pressure reduction valve 121 supplied by the intake pressure P2 to establish in the chamber 12 a reference pressure Pr variable with the position of said pedal accelerator. The spring 39 of the actuator of the nozzle 30 and the spring 912 of the actuator of the discharge valve 9 are calibrated so that, when this reference pressure Pr is equal to atmospheric pressure, said nozzle 30 and the valve of discharge 9 open for the minimum desired inlet pressure P2.

To prevent the discharge valve 9 from opening before the nozzle 30 is fully open, the supply duct 913 of the chamber 910 includes the shutter valve 914 which opens only when the nozzle 30 is on its opening stop.

Since the chamber 12 is in communication with the chambers 38 and 91 of the actuators respectively of the nozzle 30 and of the relief valve 9, this chamber 12 makes it possible to add to the springs 39 and 912 a variable setting force which modifies the threshold pressure regulator P2. Under these conditions the actuators of the nozzle 30 and the discharge valve 9 regulate the intake pressure P2 to the level programmed in the engine control computer regardless of the speed of the engine.

In the presence of a flue gas recirculation, the parameter corresponding to the intake pressure P2 will be replaced by the fresh air flow rate measured by a flowmeter located at the inlet of the engine upstream of the arrival of the recycled gases. During the slowdown phases, the different sequences in the reverse order.

Claims

1. Device for accelerating a turbocharger unit at low speeds of an alternating engine (1) operating in a four-stroke cycle and comprising at least one cylinder (1a) provided with at least one intake valve ( 2) connected to an intake manifold (3) and at least one exhaust valve (4) connected to an exhaust manifold (5), said turbocharger unit comprising at least one turbocharger (10, 70) comprising an air compressor (11, 71) supplying the intake manifold (3) and a radial turbine (12, 72) fed by the exhaust manifold (5) and driving the compressor (11, 71), characterized in that it comprises an aerodynamic ejector (20) taking a propulsive flow on the exhaust gases of the engine (1) and a flow driven on the air delivered by the compressor (11, 71) and forming a mixed flow which feeds the turbine (12, 72) of the turbocharger unit (10).

2. Device according to claim 1, characterized in that the ejector (20) comprises a mixer (21) formed by the turbine feed volute (12, 72) extended upstream, relative to the direction of circulation of the mixed flow, by a substantially straight portion (22) of sufficient length to homogenize the mixture between the propellant flow and the driven flow.

3. Device according to claim 2, characterized in that the substantially rectilinear portion of the mixer (21) is extended upstream by a portion (23) substantially coaxial conical angle at the apex of for example between 20 and 40 ° communicating with the exhaust manifold (5).

4. Device according to any one of claims 1 to 3, characterized in that the ejector (20) comprises a cylindrical tube (24) whose outer wall is provided at one (24a) of its ends, a conical portion (24b) intended to cooperate with the conical portion (23) of the mixer (21), said tube (24) being displaceable coaxially with said mixer (21) so that the two conical portions (23, 24b) form a nozzle (30) convergent annular variable section of the propeller flow acceleration.

5. Device according to claim 4, characterized in that the cylindrical tube (24) is mounted to slide tightly in a guide (26) arranged in the wall of the exhaust manifold (5) and communicates with the outlet of the compressor (11, 71) via a nonreturn valve (32) preventing the flow of exhaust gases from the exhaust manifold (5) to the compressor (10).

6. Device according to claim 4, characterized in that the section of the nozzle (30) varies between the inlet section of the volute (21) of the turbine (12, 72) and the third of said inlet section .

7. Device according to claim 4 or 6, characterized in that the cylindrical tube (25) is secured, at its end (24c) opposite to that provided with the conical portion (24b), a control piston (35). slidably mounted in a cylinder defining on one side of the piston (35), a first chamber (37) subjected to the pressure of the air delivered by the compressor (11, 71) and, on the other side of this piston of control (35), a second chamber (38) having a spring (39) acting on the piston (35), said pressure of the air delivered by the compressor (11, 71) tending to open the nozzle (30) of the ejector (20) and the force of the spring (39) tending to close this nozzle (30).

8. Device according to claim 7, characterized in that the second chamber (38) communicates with a vacuum pump to modify or neutralize the force of the spring (39).

9. Device according to any one of claims 1 to 8, said motor (1) being provided with a duct (6) for recycling flue gases, characterized in that an air / gas exchanger (51) is arranged to an intersection of the duct (6) and a bypass duct (31) communicating with the outlet of the compressor (11, 71).

10. Device according to claim 9, characterized in that it comprises a refrigerant (52) gas / water located downstream of the air / gas exchanger (51).

11. Device according to any one of claims 4 to 10, characterized in that the cylindrical tube (24) is movable to a total and sealed closure position of the nozzle (30).

12. Device according to any one of claims 1 to 11, characterized in that the turbocharger unit comprises a second turbocharger (60) having a turbine (62) communicating in continuously with the exhaust manifold (5) and a compressor (61) permanently communicating with the intake manifold (3) and in that the compressor (71) communicates with the intake manifold (3) via the intermediate of a check valve (110).

13. Device according to claim 11 or 12, characterized in that it comprises means for creating a reference gas pressure Pr variable less than a desired intake pressure P2 and which is a function of the fuel mass injected at each motor cycle and possibly depending on other operating parameters of this engine.

14. Device according to claim 13, characterized in that said means is formed by an enclosure (12) connected to the intake manifold (3) in which the desired intake pressure P2 prevails, via a valve (121) pressure reduction controlled by the engine control computer.

15. Device according to any one of claims 7 and 12 to

14, characterized in that the second chamber (38) of the actuator of the nozzle (30) is fed by the reference pressure Pr which is added to the force of the spring (39) to close said nozzle (30), the force of the spring (39) being just sufficient to keep said nozzle (30) closed at the minimum desired inlet pressure P2.

16. Device according to any one of claims 10 to 15, characterized in that the exhaust manifold (5) comprises a discharge valve (9) to the atmosphere actuated, in the fully open position of the nozzle (30), by the inlet pressure P2 in a first chamber (910) to maintain the pressure in said chamber at a set value set by a spring (912) and the reference pressure Pr in a second chamber (911) .

17. A reciprocating engine operating in a four-stroke cycle and comprising a turbocharger unit, characterized in that it comprises an acceleration device of the turbocharger unit at low engine speeds, according to any one of the preceding claims.

18. A method of accelerating a turbocharger unit (10) at low speeds of an alternating motor (1) operating in a four-stroke cycle and comprising an acceleration device of said turbocompression unit (10) according to the invention. any of claims 1 to 8, characterized in that it comprises closing the nozzle (30) of the aerodynamic ejector (20).

19. A method of accelerating a turbocharger unit (10) at low speeds of an alternating motor (1) operating in a four-stroke cycle and comprising an acceleration device of the turbocharger unit (10) according to the invention. any one of claims 1 to 8, and a conduit (6) for recycling flue gases, characterized in that it consists in obstructing said recycling duct (6), the nozzle section (30) of the ejector ( 20) being fixed.

20. A method of accelerating a turbocharger unit (10) of an alternating motor (1) operating in a four-stroke cycle and comprising an acceleration device according to any one of claims 1 and 10 to 16, characterized in that it consists of:

- between the idling speed and a speed N1 where the intake pressure P2 reaches the desired value depending on the burned fuel flow, to maintain the discharge valve (9), the non-return valve (11) and the nozzle ( 30) closed so that the engine (1) is supplied with air by the single compressor (61) of the turbocharger (60) driven by the turbine (62) of this turbocharger (60) which receives all the burnt gases in the engine, and

between this regime N1 and a regime Nt where the discharge pressure of the compressor (71) of the turbocharger (70) reaches the inlet pressure P2, to maintain this intake pressure P2 at its set point by the gradual opening of the nozzle (30), the discharge valve (9) and the nonreturn valve (11) remaining closed so that the engine (1) is supplied with air by the single compressor (61) of the turbocharger (60) driven by the turbine (62) which receives only a fraction of the burnt gases in the engine whose complement feeds the turbine (72) by the aerodynamic ejector (20) which drives the compressor (71) discharging exclusively into the turbine ( 72) via said aerodynamic ejector (20).

21. A method according to claim 20, characterized in that, when the speed passes through the value of the Nt regime, the non-return valve (110) opens and the compressor (71) of the turbocharger (70) begins to participate in the system. supply of the motor (1).

22. The method of claim 20 or 21, characterized in that beyond the Nt regime, the nozzle (30) continues to open to maintain the inlet pressure P2 to its set point, the air supply of the engine by the compressor (71) increases.

23. The method of claim 20 or 21, characterized in that, before the nozzle (30) is fully open, the static pressure at the outlet of this nozzle (30) intersects the inlet pressure P2 and the check valve (32). ) closes, the entire flow of the compressor (71) then being directed to the intake manifold (3) of the engine (1).

24. A method according to any one of claims 20 to 23, characterized in that, when the nozzle (30) is fully open, the discharge valve (9) takes over to maintain the inlet pressure P2 at a value deposit.