Method and system for controlling a supercharged internal combustion engine configured to manage retention and desorption of liquid water in a cooler

Abstract

In a method (100) for controlling a supercharged internal combustion engine (10), a mass of liquid water (M_eau) retained in real time on an inner wall of a heat exchanger (30) receiving a mixture of outside air and recycled burned gas is estimated, a difference in mass of water (ΔM_eau) between the mass of liquid water (M_eau) and a predetermined critical mass of liquid water (MC) is determined, and if the absolute value of the difference (abs(ΔM_eau)) is less than a threshold value (S), the maximum mass of water that can be retained by the heat exchanger (30) is managed by reducing an EGR rate (Tx_EGR) by controlling an EGR control valve (38c) and / or by reducing a flow rate (Q_WCAC) of cooling fluid passing through the heat exchanger (30) by controlling a pump configured to circulate the cooling fluid in the heat exchanger (30), and / or by increasing a temperature (T_WCAC) of the cooling fluid in the heat exchanger (30).

Description

[Technical Field]

[0001] The present invention relates to the field of internal combustion engines, and more particularly to the field of supercharged internal combustion engines, whether gasoline or diesel.

[0002] More specifically, the present invention relates to reducing condensation in charge air coolers. [Background technology]

[0003] Typically, supercharged internal combustion engines are equipped with a charge air cooler and a low-pressure exhaust gas recirculation (EGR) circuit that allows burnt gases from combustion to be drawn into the intake system and reintroduced upstream of the supercharger.

[0004] These inert gases allow an increase in the total mass of gases admitted to the combustion chamber in gasoline engines, thereby reducing the need for reduced intake manifold pressure to manage the air charge, thereby limiting pumping losses and improving combustion, while in primarily diesel engines, partial reinjection of burnt gases reduces combustion temperatures, essentially reducing nitrogen oxide emissions.

[0005] However, the use of a low-pressure EGR circuit can lead to problems with water condensation in the engine's intake system. This water typically results from the humidity of the outside air resulting from the fresh air intake and / or from water vapor contained in the exhaust gases recirculated by the low-pressure EGR circuit.

[0006] This condensation can then lead to: - Emission of liquid water droplets upstream of the compressor and premature wear of the compressor wheels. - Water accumulation at low points in the intake circuit, leading to corrosion problems, for example in the charge air cooler or EGR cooler. -Icing in the intake system under harsh environmental conditions, either during the operating phase or during engine cooling at standstill. A slow, gradual buildup of frost can then lead to ice buildup. When the ambient temperature rises above 0°C, this ice transforms into liquid, which can in turn cause corrosion or premature wear of the compressor wheels. This water can also be drawn into the engine, especially during engine start-up, and can damage it.

[0007] Furthermore, during operating phases that favor water condensation, water vapor contained in the mixture of fresh air and EGR gases tends to condense in the intake circuit and particularly on surfaces of the charge air cooler, for example due to environmental conditions such as high ambient humidity and / or low ambient temperature or due to engine operation.

[0008] This water can become trapped in the cooler and become detached, which can impair or even extinguish engine combustion.

[0009] Patent Document 1 proposes a method for controlling the EGR circuit valve using a humidity sensor to prevent condensation in the intake circuit. According to this method, intake humidity is measured, the mole fraction of water vapor contained in the intake air is determined, the water vapor pressure in the EGR circuit is determined, and the EGR valve is opened to allow EGR gas to flow when the water vapor in the EGR circuit is less than the saturated water vapor pressure in the EGR circuit. This document also proposes a modification in which the flow rate of refrigerant in the EGR cooler is increased before the EGR valve is opened.

[0010] Patent Document 2 also proposes a method for increasing the recirculation flow rate of the EGR exhaust gas when the estimated amount of condensate accumulated in the EGR cooler exceeds a threshold. The estimated amount of accumulated condensate is estimated as a function of the amount of evaporative condensate using a condensation model. This document proposes a modification to increase the flow rate of the coolant in the EGR cooler.

[0011] However, the effect of these measures is to limit the flow of liquid water into the engine or even the flow of water trapped in the EGR cooler as a result of stabilized conditions, and none of these measures are suitable for unstable, i.e., transient, engine operation.

[0012] Therefore, these measures do not provide an effective solution to the problem of water accumulation in the charge air cooler, which may experience a sudden release of water following a sudden increase in the flow rate of the mixture of air and EGR gases drawn in by the engine in response to a full load demand, for example when the driver presses the accelerator pedal. This sudden release of liquid water into the combustion chamber can lead to flameout, i.e., loss of torque production or misfire, which may ultimately damage the engine or some of its associated components, such as the depollution catalyst. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] US Patent Application Publication No. 2020 / 0182204 [Patent Document 2] US Patent Application Publication No. 2014 / 0102428 Summary of the Invention

[0014] There is a need for improved management of liquid water retention and desorption within the intake circuit, and more particularly within the charge air cooler of a supercharged air internal combustion engine.

[0015] It is therefore an object of the present invention to provide a method and engine control system configured to manage the accumulation and desorption of liquid water in a charge air cooler.

[0016] The object of the invention is to provide a method for controlling an internal combustion engine having at least one cylinder, a fresh air intake manifold supplied with fresh air by a pipe equipped with a flow meter, a compressor, a turbocharger and a heat exchanger or charge air cooler downstream of the compressor and upstream of the intake manifold.

[0017] The engine also comprises, from upstream to downstream along the direction of flow of the burnt gases, an exhaust circuit comprising an exhaust manifold, a turbocharger turbine and a system for decontaminating the combustion gases of the engine, and a circuit for partial recirculation of exhaust gases to the intake, starting at a point on the exhaust circuit downstream of the turbine and in particular downstream of the system or part thereof of the gas decontamination system, and opening into the fresh air supply pipe upstream of the turbocharger compressor, the partial EGR recirculation circuit comprising an EGR control valve.

[0018] During processing, the mass of liquid water retained on the inner walls of the heat exchanger in real time is estimated, the difference in mass of water between the mass of water and a predetermined critical mass of liquid water is identified, and if the absolute value of the difference is less than a threshold value, the maximum mass of water that can be retained by the heat exchanger is managed by reducing the EGR rate by controlling an EGR control valve, and / or by reducing the flow rate of cooling fluid passing through the heat exchanger by controlling a pump configured to circulate the cooling fluid in the heat exchanger, and / or by increasing the temperature of the cooling fluid in the heat exchanger.

[0019] The treatment thus solves the problem of gradual condensation of liquid water in the charge air cooler, avoiding both the risk of rapid desorption and extinguishing of engine combustion.

[0020] Generally, control methods for supercharged internal combustion engines are designed to manage the accumulation and desorption of liquid water within the charge air cooler.

[0021] Liquid water is -Condensation of a mixture of outside air and EGR gases on the inner walls of the charge air cooler, - evaporation of liquid water deposited on the inner walls of the charge air cooler, and -Flow rate of the mixture of fresh air and EGR gas through the charge air cooler provided that there is a balance between

[0022] The process according to the invention makes it possible to strike a balance between these different perspectives.

[0023] The step of estimating the mass of water makes it possible to determine the mass of water that the heat exchanger can temporarily store without desorption towards the combustion chamber.

[0024] Reducing the flow rate of cooling fluid through the heat exchanger has the effect of increasing the temperature of the inner walls of the heat exchanger, thus promoting the evaporation of water trapped on the walls, and increasing the temperature of the mixture of air and EGR gas passing through the heat exchanger, thereby increasing the evaporation rate of water trapped in the heat exchanger.

[0025] The temperature of the cooling fluid flowing through the heat exchanger can be increased by a controlled calorostat which determines, among other things, whether or not liquid should be circulated in the radiator in order to increase the temperature of the heat exchanger walls.

[0026] Advantageously, the step of estimating the mass of liquid water retained on the inner wall of the heat exchanger in real time comprises: - estimating the mass flow rate of water vapour contained in the input fresh air as a function of the input fresh air temperature, the air flow rate and an estimate of the ambient relative humidity, the ambient relative humidity being obtained for example either by a humidity rate sensor located in the intake circuit, e.g. in a flow meter or external to the vehicle or by a weather service, in particular if the vehicle is a so-called "connected" vehicle; estimating the mass flow rate of water vapor contained in the exhaust gas as a function of the fresh air flow rate, the injected fuel flow rate, the average composition of the fuel, and the richness of the combustion; estimating a mass flow rate of water vapor in the EGR partial recirculation duct as a function of the mass flow rate of water vapor contained in the exhaust gas and the EGR rate; estimating a mass flow rate of water vapor contained in a mixture of fresh air and EGR burned gases upstream of the air compressor as being equal to the sum of the mass flow rate of water vapor contained in the fresh air intake and the mass flow rate of water vapor in the EGR duct; - estimating the mass flow rate of liquid water condensing on the inner wall of the heat exchanger as a function of the mass flow rate of water vapor contained in the mixture of fresh air and EGR burnt gases upstream of the air compressor, the temperature of the inner wall, and the value of the boost pressure, the temperature of the inner wall being obtained, for example, by measuring the temperature of the coolant flowing through the heat exchanger via one or more sensors arranged upstream and / or downstream of the heat exchanger; estimating the mass of liquid water retained on the surface of the inner wall of the heat exchanger as a function of the difference in mass flow rate between the mass flow rate of liquid water condensing on the inner wall of the heat exchanger and the mass flow rate of evaporated water in the heat exchanger, the mass flow rate being determined as a function of the temperature of the gas passing through the heat exchanger and the mass flow rate of the engine; Equipped with.

[0027] For example, engine mass flow is dependent on air flow, fuel flow, and EGR rate.

[0028] For example, the step of estimating the mass of liquid water includes receiving the time integral value of the difference in mass flow rate between the mass flow rate of liquid water condensing on the inner wall of the heat exchanger and the mass flow rate of evaporated water in the heat exchanger.

[0029] The time integral of the mass flow difference is permanently saturated at a predetermined maximum limit corresponding to the maximum mass of liquid water that can be stored in the heat exchanger given the current volumetric flow rate of gas passing through the heat exchanger.

[0030] Depending on the geometry of the heat exchanger, its inclination and the gas-side material that makes up its exchange surfaces, each value of the current, i.e., instantaneous, gas flow rate through the heat exchanger determines the maximum limit, i.e., maximum mass, of liquid water that can be retained in the heat exchanger, which can be characterized.

[0031] For example, to determine the maximum limit, a dry heat exchanger is weighed, the volume normally covered by the flow of the air and EGR gas mixture through the heat exchanger is completely filled with water, the heat exchanger is placed on a test bench and ventilated with a constant flow of air until the water it contains is mechanically drained without waiting for the water to evaporate, and the heat exchanger is then weighed to estimate the mass of water it held.

[0032] Advantageously, the step of estimating the mass of liquid water retained in real time comprises a step of estimating the volumetric flow rate of the engine as a function of the temperature of the gases passing through the heat exchanger, and the maximum limit is determined as a function of said volumetric flow rate.

[0033] Advantageously, during the step of determining the difference in mass of water between the mass of water and the critical mass of liquid water, the critical mass of water is determined, defined as the minimum mass of water that, if it reaches the combustion chamber, will result in extinguishing of combustion, and a subtraction is performed between the mass of water and the critical mass of water.

[0034] The critical mass of water corresponds to the mass of water that would pose a risk of extinguishing combustion if a desorption event were to occur, e.g., a sudden increase in the airflow introduced by the engine following a demand for acceleration, were to occur, e.g., if this were to reduce the maximum limit, i.e., maximum mass, of liquid water that can remain in the heat exchanger.

[0035] The critical mass of water can be estimated by testing on a stationary engine test bench by injecting increasing masses of liquid water into the cylinder inlet and measuring the internal combustion pressure. The maximum allowable mass of liquid water per individual combustion cycle and per cylinder is then estimated, as well as the maximum allowable mass of liquid water for the engine, taking into account its dynamics.

[0036] For example, the reduction in the EGR rate setting may be applied continuously, i.e., as a maximum limit that must not be exceeded throughout engine use, or may be applied once for a set period of time, to reduce the mass of liquid water retained on the inner walls of the heat exchanger in real time.

[0037] For example, the reduction in the flow rate of cooling fluid passing through the heat exchanger may be continuous, i.e., applied as a maximum limit that must not be exceeded throughout engine use, or may be applied only once for a specific period of time, in order to reduce the mass of liquid water retained on the inner walls of the heat exchanger in real time.

[0038] For example, the increase in temperature of the flow of cooling fluid passing through the heat exchanger may be applied continuously, i.e., as a maximum limit that must not be exceeded throughout the entire use of the engine, or may be applied only once for a specific period of time, in order to reduce the mass of liquid water retained on the walls of the heat exchanger in real time.

[0039] In an embodiment in which the motor vehicle is a hybrid vehicle having a heat engine and at least one electric motor, managing the maximum mass of water that can be retained in the heat exchanger comprises controlling the speed and torque of the electric motor to increase the flow rate taken into the heat engine so as to expel the film of water retained on the walls of the heat exchanger at a given point.

[0040] According to a second aspect, the invention relates to an electronic control unit for an internal combustion engine comprising at least one cylinder, a fresh air intake manifold supplied with fresh air by a pipe provided with a flow meter, a compressor, a turbocharger and a heat exchanger downstream of the compressor and upstream of the intake manifold.

[0041] The engine further comprises, from upstream to downstream along the direction of flow of the burnt gases, an exhaust circuit comprising an exhaust manifold, a turbocharger turbine and a system for decontaminating the combustion gases of the engine, and a circuit for partial recirculation of exhaust gases at the intake section, starting at a point on the exhaust circuit downstream of the turbine, in particular downstream of the gas decontamination system or part of the gas decontamination system, and opening into the fresh air supply pipe upstream of the turbocharger compressor, said partial EGR recirculation circuit comprising an EGR control valve.

[0042] The electronic control unit includes an engine control system, a module for estimating in real time the mass of liquid water retained on the inner wall of the heat exchanger; a module for determining the difference in mass of water between the mass of water and a predetermined critical mass of liquid water; a module for managing the maximum mass of water that can be retained by the heat exchanger, configured to reduce the EGR rate by controlling an EGR control valve, reduce the flow rate of the cooling fluid through the heat exchanger by controlling a pump configured to circulate the cooling fluid in the heat exchanger, and / or increase the temperature of the cooling fluid in the heat exchanger, when the absolute value of the difference in the mass of the water is less than a threshold value; Equipped with.

[0043] Typically, the control system of a supercharged internal combustion engine is configured to manage the accumulation and desorption of liquid water within the charge air cooler.

[0044] Advantageously, the module for estimating the mass of liquid water retained on the inner walls of the heat exchanger in real time is configured to estimate the mass flow rate of water vapor contained in the incoming fresh air as a function of the temperature of the incoming fresh air, the air flow rate obtained by the flow meter and an estimate of the ambient relative humidity, the ambient relative humidity being obtained either by a humidity rate sensor located in the intake circuit, for example in the flow meter, or external to the vehicle or by a weather service, particularly if the vehicle is a so-called "connected" vehicle.

[0045] Advantageously, the module for estimating the mass of trapped liquid water is also configured to estimate the flow rate of water vapor contained in the exhaust gas as a function of the fresh air flow rate, the injected fuel flow rate, the average composition of said fuel and the richness of combustion, and therefrom to infer the mass flow rate of water vapor in the EGR duct as a function of said flow rate of water vapor contained in the exhaust gas and the EGR rate.

[0046] Advantageously, the module for estimating the mass of trapped liquid water is also configured to estimate the mass flow rate of water vapor contained in the mixture of fresh air and EGR burnt gases upstream of the air compressor by summing the mass flow rate of water vapor contained in the fresh air intake and the mass flow rate of water vapor in the EGR duct.

[0047] Advantageously, the module for estimating the mass of accumulated liquid water is also configured to estimate the mass flow rate of liquid water condensing on the inner wall of the heat exchanger as a function of the mass flow rate of water vapor contained in the mixture of fresh air and burnt gases upstream of the air compressor, the temperature of the inner wall and the boost pressure value, the temperature of the inner wall being obtained, for example, by measuring the temperature of the refrigerant flowing through the heat exchanger by one or more sensors arranged upstream and / or downstream of the heat exchanger.

[0048] Advantageously, the module for estimating the mass of trapped liquid water is also configured to estimate the engine mass flow rate as a function of the air flow rate, the fuel flow rate, and the EGR rate, and therefrom to deduce an estimate of the mass of water evaporated in the heat exchanger and an estimate of the engine volumetric flow rate as a function of the temperature of the gases passing through the heat exchanger.

[0049] For example, the module for estimating the mass of retained liquid water is also configured to estimate the mass of liquid water retained on the surface of the inner wall of the heat exchanger as the integral value of the difference between the mass flow rate of liquid water condensing on the inner wall of the heat exchanger and the mass flow rate of water evaporated within the heat exchanger.

[0050] Advantageously, the integral is permanently saturated at a maximum limit corresponding to the maximum volume of liquid water that can be stored in the heat exchanger given the current volumetric flow rate of gas passing through the heat exchanger.

[0051] The water mass estimation module is used to identify the mass of liquid water that the heat exchanger can temporarily retain without desorption towards the combustion chamber.

[0052] This trapped liquid water mass becomes more critical when the ambient humidity is high, the EGR rate is high, the boost pressure is high, the temperature of the cooling fluid passing through the heat exchanger is low, and the flow rate of the mixture of air and EGR gases passing through the heat exchanger and into the combustion chamber is low.

[0053] Advantageously, the management module is configured to control various actuators of the internal combustion engine when the absolute value of the difference in water mass is below a threshold value, i.e. when a desorption phenomenon occurs, for example when a sudden increase in the airflow injected by the engine occurs, for example following a request for acceleration, and the mass of trapped liquid water comes too close to the critical mass of water, posing a risk of extinguishing combustion.

[0054] According to another aspect, the invention relates to a motor vehicle comprising an electronic control unit as described above.

[0055] Other objects, features and advantages of the present invention will become apparent from the following description, given by way of non-limiting example only, made with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0056] [Figure 1] 1 shows a highly schematic example of the construction of an internal combustion engine of a motor vehicle equipped with a control unit comprising a control system according to the invention; [Figure 2] 3 shows a curve illustrating the progression of the maximum mass of liquid water that can be retained in the heat exchanger as a function of the engine volumetric flow rate. [Figure 3]2 shows an overview of a control process according to the present invention, which is carried out by the control system of FIG. 1. [Figure 4] The mass estimation step of the process of FIG. 3 is shown in detail. DETAILED DESCRIPTION OF THE INVENTION

[0057] 1 shows a schematic diagram of a spark-ignition internal combustion engine 10, which may be a gasoline-powered engine, particularly for a motor vehicle, but which may alternatively be a diesel engine.

[0058] These architectures are provided by way of example and are not limiting to the only configurations to which the control of an engine according to the present invention is applicable.

[0059] In the illustrated example, the internal combustion engine 10 includes, in a non-limiting manner, three cylinders 12 in line, a fresh air intake manifold 14, an exhaust manifold 16, and a turbocompression system 18.

[0060] The cylinders 12 are supplied with air via an intake manifold 14, or intake distributor, which is itself supplied by a pipe 20 provided with an air filter 22 and a compressor 18b of a turbocharger 18 of the engine 10.

[0061] Each cylinder 12 is supplied with fuel, for example gasoline.

[0062] In a known manner, the turbocharger 18 basically comprises a turbine 18a driven by the exhaust gases and a compressor 18b mounted on the same axis or shaft as the turbine 18a and compressing air distributed by an air filter 22 in order to increase the amount of air (mass flow) injected into the cylinders 12 of the engine 10. The turbine 18a may be of the "variable geometry" type, i.e. the turbine wheel is fitted with variable tilt blades in order to modulate the amount of energy obtained from the exhaust gases and therefore the charging pressure.

[0063] The heat exchanger 30 is arranged after the outlet of the compressor 18b, which is fitted to the fresh air supply pipe 14a of the intake manifold 14.

[0064] The internal combustion engine 10 therefore comprises an intake circuit Ca, an exhaust circuit Ce and a fuel injection circuit (not shown).

[0065] The intake circuit Ca includes the following components arranged from upstream to downstream along the airflow direction: - air filter 22, i.e., wind box; a flow meter 24 arranged in the intake pipe 20 downstream of the air filter 22. The flow meter 24 is configured to measure the actual value of the flow rate of air entering the engine 10. The flow meter 24 measures only the flow rate of fresh air. For example, an intake valve 26 equipped with a position sensor (not shown). a compressor 18b of the turbocharger 18 configured to compress to low pressure air taken from the outside atmosphere and optionally recycled exhaust gases, as will be explained below; - Throttle box 28, i.e. the valve for admitting gas to the engine. a heat exchanger 30 configured to cool the intake gases corresponding to the mixture of fresh air and recycled gases after their compression in the compressor 18b; -Intake manifold 14.

[0066] The heat exchanger 30 is here a "supercharged" intake gas cooler, corresponding to a water-filled air cooler. Hereinafter, the terms "heat exchanger 30" and "charge air cooler 30" refer to the same element, which may alternatively be an air-to-air cooler.

[0067] The exhaust circuit Ce comprises, from upstream to downstream in the direction of flow of burnt gases: -Exhaust manifold 16. a turbine 18a of a turbocharger 18 configured to extract energy from the exhaust gases passing through it, said expansion energy being transferred via a common shaft to a compressor 18b for compression of the intake gases. - A system 40 for decontaminating combustion gases from the engine.

[0068] The exhaust manifold 16 collects the exhaust gases produced by the combustion and discharges them to the outside via an exhaust gas duct 30 opening onto the turbine 18a of the turbocharger 18 and via an exhaust line 36 attached downstream of the turbine 18a.

[0069] As a non-limiting example, the engine combustion gas pollution removal system 40 comprises a first device 42 having a three-way catalytic converter 42a, which is associated with a proportional first oxygen sensor 43a mounted upstream of the first pollution removal device 42, i.e., upstream of the catalytic converter 42a.

[0070] In a manner known per se, the first upstream oxygen sensor 43a is generally used in a closed loop to adjust the richness of the air-fuel mixture in the engine around a set value, for example the value 1, which corresponds to a stoichiometric air-fuel mixture. By "richness" is meant the ratio of fuel mass flow to air mass flow divided by the ratio of fuel mass flow to air mass flow at a stoichiometric ratio.

[0071] Furthermore, a second oxygen sensor 43b, for example of the binary or proportional type, is most often mounted downstream of the first decontamination device 42 so as to be able to correct the setpoint of the richness regulation loop described above, in particular for the purpose of adjusting the amount of oxygen stored inside the first decontamination device 42. However, the presence of this second downstream sensor is not essential to the implementation of the invention.

[0072] The gas decontamination system 40 also comprises a second device 44, in this case a particulate filter, and an exhaust pipe 45 attached to the outlet of the second pollution prevention device 44 and opening to the outside. The gas decontamination system 40 may also include a third oxygen sensor 43c, for example of the binary type, attached downstream of the second device 44, for example for diagnostic purposes.

[0073] As shown, the engine 10 includes a circuit 38 for partial recirculation of exhaust gases to the intake side, known as an "EGR" circuit.

[0074] This circuit 38, here a low pressure exhaust gas recirculation circuit referred to as "EGR BP", starts at a point in the exhaust line 36, here in the exhaust pipe 45, downstream of the turbine 18a, in particular in the case of FIG. 1 downstream of the gas decontamination system 40, and returns the exhaust gases to a point upstream of the compressor 18b of the turbocharger 18, in particular downstream of the inlet valve 26, in the fresh air supply pipe 20.

[0075] Alternatively, although not shown, the low-pressure exhaust gas recirculation circuit may originate at the outlet of the turbine 18a or downstream of only a portion of the gas decontamination system 40, for example, between the first and second decontamination devices 42, 44.

[0076] As shown, the recirculation circuit 38 includes an EGR gas cooler 38a, a filter 38b, and a "V EGR BP" control valve 38c configured to regulate the flow rate of low-pressure exhaust gas along the direction of recirculated gas flow. The "V EGR BP" valve 38c is located downstream of the cooler 38a and upstream of the compressor 18b.

[0077] By way of example and not limitation, the engine is associated with a fuel circuit comprising fuel injectors (not numbered) that inject gasoline directly into each cylinder from, for example, a fuel tank 50 .

[0078] The engine may include, but is in no way limited to, a fuel vapor purge circuit 60 including a reservoir 62 or fuel vapor tank 62 for receiving fuel vapor from fuel tank 50, an actuated pump 64 connected downstream of reservoir 62, and a purge solenoid valve 66 connected downstream of pump 64. Purge solenoid valve 66 is connected to the engine intake side downstream of flow meter 24.

[0079] The engine comprises an electronic control unit ECU comprising a control system 70 configured to control various elements of the internal combustion engine, in particular the EGR rate Tx_EGR, the flow rate Q_WCAC of cooling fluid (water in the case of an air-to-water heat exchanger) passing through the heat exchanger 30 and the temperature T_WCAC of the cooling fluid in the heat exchanger 30.

[0080] The control system 70 receives data collected or estimated by sensors at various locations on the engine.

[0081] Control system 70 may also receive other data, such as temperatures or other pressures at various locations within the engine.

[0082] The control system 70 comprises a module 72 for estimating the mass of liquid water M_eau retained on the inner walls of the heat exchanger 30 in real time.

[0083] The module 72 for estimating the mass M_eau of liquid water retained in real time on the inner walls of the heat exchanger 30 is configured to estimate the mass flow rate Q_M_vapeur_A of water vapor contained in the incoming fresh air as a function of the temperature T_air of the incoming fresh air, the air flow rate Qair obtained by the flow meter 24 and an estimate H of the ambient relative humidity, the latter being obtained either by a humidity rate sensor located in the intake circuit Ca, for example in the flow meter 24 or external to the vehicle or by a weather service, particularly if the vehicle is a so-called "connected" vehicle.

[0084] The module 72 is also configured to estimate the mass flow rate Q_M_vapeur_E of water vapor contained in the exhaust gases, or more precisely the mass flow rate Q_M_vapeur_E of water vapor contained in the total flow rate of combustion gases released by the engine before a portion is withdrawn to be recycled to the intake side, as a function of the fresh air flow rate Qair, the injected fuel flow rate Qcarb, the average composition of said fuel carb and the richness of the combustion, and to deduce therefrom the mass flow rate Q_M_vapeur_EGR of water vapor in the EGR duct 38 as a function of said mass flow rate Q_M_vapeur_E of water vapor contained in the exhaust gases and the EGR rate Tx_EGR.

[0085] The module 72 is also configured to estimate the mass flow rate of water vapor Q_M_vapeur_Ca contained in the mixture of fresh air and EGR burned gases upstream of the air compressor 18b as equal to the sum ΣQ_M of the mass flow rate of water vapor Q_M_vapeur_A contained in the fresh air intake and the mass flow rate of water vapor Q_M_vapeur_EGR in the EGR duct 38.

[0086] The module 72 is also configured to estimate the mass flow rate Q_M_WCAC of liquid water condensing on the inner wall of the heat exchanger 30 as a function of the mass flow rate Q_M_vapeur_Ca of water vapor contained in the mixture of fresh air and EGR burnt gases upstream of the air compressor 18b, the temperature T_WCAC of the inner wall, and the boost pressure value Psuralim, the temperature T_WCAC being obtained, for example, by measuring the temperature of the coolant flowing through the heat exchanger 30 by one or more sensors arranged upstream and / or downstream of the heat exchanger 30.

[0087] The module 72 is also configured to estimate the engine mass flow rate Q_M as a function of the air flow rate Qair, the fuel flow rate Qcarb and the EGR rate Tx_EGR, and from there to infer an estimate of the flow rate of water evaporated in the heat exchanger 30 Q_M_eau_evap and an estimate of the engine volumetric flow rate Q_V as a function of the temperature of the gases passing through the heat exchanger 30 T_gaz_WCAC.

[0088] The module 72 is also configured to estimate the mass M_eau of liquid water remaining on the surface of the inner wall of the heat exchanger 30 as being equal to the time integral ∫ΔQ_M of the difference between the mass flow rate Q_M_WCAC of liquid water condensing on the inner wall of the heat exchanger 30 and the mass flow rate Q_M_eau_evap of water evaporating within the heat exchanger 30.

[0089] The time integral value ∫ΔQ_M is permanently saturated at a maximum limit M_eau_max corresponding to the maximum mass of liquid water that can be retained in the heat exchanger 30 given the volumetric flow rate of gases (air and EGR gas) passing through the heat exchanger 30.

[0090] Depending on the geometry of the heat exchanger 30, its inclination, and the gas-side material that makes up its exchange surfaces, the maximum mass of liquid water that can be stored by the heat exchanger 30 can be characterized as a curve that is a decreasing function of the volumetric flow of gas passing through the heat exchanger 30. In normal operation, when all of the intake gas volumetric flow that is subsequently compressed in the compressor 18b is cooled, this flow volumetric flow merges with the engine volumetric flow Q_V.

[0091] To determine the maximum mass of liquid water that can be stored in the heat exchanger, M_eau_max, the heat exchanger 30 is weighed dry, the volume normally traversed by the air and EGR gas mixture is completely filled with water, the heat exchanger 30 is placed on a test bench, and the heat exchanger 30 is ventilated with a constant flow of air until the water it contains is mechanically drained without waiting for the water to evaporate. The heat exchanger 30 is then weighed to estimate the mass of water it has retained. This mass corresponds to the maximum mass of liquid water that can be stored, M_eau_max, for the constant air flow rate under consideration.

[0092] From this, we can infer a curve similar to that shown in Figure 2, where the horizontal axis represents the volumetric flow rate Q_V through the heat exchanger and the vertical axis represents the maximum mass of liquid water M_eau_max that can be stored in the heat exchanger.

[0093] Note that, strictly speaking, this is a decreasing curve. For example, as the volumetric flow rate Q_V increases from a value Q_V(A) corresponding to point A on the horizontal axis in FIG. 2 (where the mass M_eau of retained liquid water is not necessarily saturated by the maximum mass M_eau_max of retained liquid water) to a value Q_V(B) corresponding to point B on the horizontal axis in FIG. 2, a mass of water corresponding to the difference between the mass M_eau of retained liquid water in real time corresponding to point A and the maximum mass M_eau_max(B) of liquid water corresponding to the volumetric flow rate at point B is released downstream of the heat exchanger. In particular, when the flow rate increases rapidly to the maximum engine flow rate Q_V(Pmax), which is the value at the full load point at the maximum power of the engine represented by point Pmax in FIG. 2, the maximum mass M_eau_max of liquid water retained in the heat exchanger decreases very sharply to the maximum mass M_eau_max(Pmax) of retained liquid water at the point of maximum power Pmax. This release of liquid water becomes dangerous when the amount released becomes greater than or too close to the critical mass of liquid water that could extinguish the combustion.

[0094] A module 72 for estimating the liquid water mass M_eau is used to determine the mass of water that the heat exchanger 30 can temporarily store without desorption towards the combustion chamber.

[0095] This mass of trapped liquid water becomes more critical when the ambient humidity is high, the EGR rate is high, the boost pressure is high, the temperature of the cooling fluid passing through the heat exchanger 30 is low, and the flow rate of the mixture of air and EGR gases passing through the heat exchanger 30 and into the combustion chamber is low.

[0096] Indeed, the mass of liquid water trapped on the interior walls of the heat exchanger 30 is not a problem as long as it remains trapped, but becomes problematic following a strong and rapid increase in the flow rate of the air and EGR gas mixture through the heat exchanger 30, such as in connection with a high load demand associated with a downshift, accelerator pedal depression, etc., which results in an increase in torque and speed, and the trapped liquid water then rapidly detaches from the walls of the heat exchanger 30 and is introduced into the combustion chamber of the engine.

[0097] The control system 70 also includes a module 74 for determining the difference in water mass ΔM_eau between the liquid water mass M_eau and a critical mass MC of liquid water corresponding to the minimum mass of water that would extinguish the combustion if it reached the combustion chamber too quickly.

[0098] The critical mass of water MC corresponds to the mass of water that would pose a risk of extinguishing the combustion if a desorption event were to occur, for example, if there were a sudden increase in the airflow introduced by the engine following a demand for acceleration.

[0099] The critical mass of water, MC, can be estimated by testing on a stationary engine test bench by injecting increasing masses of liquid water into the cylinder and measuring the combustion pressure, which allows the indicated torque to be estimated, and the maximum allowable mass of liquid water per combustion cycle and per cylinder, corresponding to poor combustion, can be inferred.

[0100] The critical mass of water MC for the engine can then be estimated by knowing the engine dynamics, ie the duration and therefore the number of combustion cycles required to reach the maximum power point.

[0101] The control system 70 also includes a module 76 for managing the maximum mass of liquid water that can be retained by the heat exchanger 30. The management module 76 is configured to control various actuators of the internal combustion engine when the absolute value abs(ΔM_eau) of the difference ΔM_eau is less than a calibratable threshold S. This corresponds to the following: the mass of releasable liquid water, which corresponds to the difference between the mass of liquid water retained in real time M_eau and the maximum mass of liquid water that can be retained at the maximum power point M_eau_max(Pmax), becomes equal to the critical mass of water MC or, taking into account a safety margin, becomes too close to the critical mass of water MC, which poses a risk of extinguishing the combustion in the event of a desorption phenomenon, for example, in the event of a sudden increase in the airflow injected by the engine following a request for acceleration to maximum engine power.

[0102] The management module 76 is configured to control various actuators of the internal combustion engine, in particular to limit the mass of water trapped in the heat exchanger 30 .

[0103] Thus, the management module 76 is configured to reduce the EGR rate setpoint Tx_EGR, in particular, to reduce the humidity, and therefore the liquid water, at the inlet of the heat exchanger 30. This reduction in the EGR rate setpoint may be continuous, i.e., applied as a maximum limit that should not be exceeded throughout engine use, or may be applied one-time for a set period of time, to reduce the mass of liquid water M_eau retained in real time on the inner walls of the heat exchanger 30.

[0104] The management module 76 is also configured to reduce the flow rate of the cooling fluid through the heat exchanger 30 by controlling a pump that supplies the cooling fluid. This has the effect of increasing the temperature T_WCAC of the inner walls of the heat exchanger 30, thus promoting evaporation of the water trapped on the walls, and increasing the temperature T_WCAC of the mixture of air and EGR gases passing through the heat exchanger 30, thereby increasing the evaporation rate of the water trapped in the heat exchanger 30.

[0105] This reduction in the flow rate of the cooling fluid passing through the heat exchanger 30 may be continuous, i.e., applied as a maximum limit that must not be exceeded throughout the entire use of the engine, or may be applied only once for a specific period of time, in order to reduce the mass of liquid water M_eau retained on the inner walls of the heat exchanger 30 in real time.

[0106] Finally, the management module 76 is also configured to increase the temperature of the cooling fluid circulating through the heat exchanger 30 in order to increase the temperature T_WCAC of the walls of the heat exchanger 30, in particular by means of a controlled calostat that determines whether or not the liquid should be circulated in the radiator.

[0107] If the motor vehicle is a hybrid vehicle equipped with an internal combustion engine and at least one electric motor, the management module 76 is configured to control the speed N and torque C of the electric motor to increase the flow rate taken in by the internal combustion engine so as to remove the water film accumulated on the walls of the heat exchanger 30.

[0108] The management module 76 is therefore configured to select one of the measures making it possible to limit the mass of water stored in the heat exchanger 30 depending on the conditions and operating point of the engine.

[0109] Thus, at low loads, when there is a need for intervention to reduce the mass of trapped water in real time and there is no need to reduce intake air temperature to limit knock or improve performance, priority may be given to, for example, increasing the temperature of the cooling fluid flowing through the heat exchanger 30. On the other hand, at high loads, it is preferable to reduce the EGR rate setpoint Tx_EGR in order to reduce intake air temperature to limit knock or improve performance. At low ambient temperatures and when there is no risk to the cooling circuit, for example, it is preferable to increase the temperature of the cooling fluid flowing through the heat exchanger 30, but at warm ambient (or engine) temperatures this measure is ruled out. It should be noted that each of these measures may be used individually or simultaneously.

[0110] The engine control process 100, shown in detail in FIG. 3, includes a step 102 in which the mass of water retained in the heat exchanger 30 is initialized.

[0111] The engine control method 100 also comprises a step 110 of estimating the liquid water mass M_eau retained on the inner walls of the heat exchanger 30 in real time, a step 125 of determining the water mass difference ΔM_eau between the water mass M_eau and a critical mass MC of liquid water corresponding to the minimum water mass that would result in combustion extinguishing if it were to reach the combustion chamber too quickly, and a step 130 of managing the maximum water mass that can be retained by the heat exchanger 30 if the absolute value abs(ΔM_eau) of the difference ΔM_eau is less than a threshold value S. During the step 130 of managing the maximum water mass that can be retained by the heat exchanger 30, various actuators of the internal combustion engine are controlled in order to limit the mass of water retained in the heat exchanger 30, as will be described below.

[0112] The step 110 of estimating the mass M_eau is shown in more detail in FIG.

[0113] Step 110 of estimating the mass M_eau of liquid water retained on the inner walls of the heat exchanger 30 in real time comprises step 111 of estimating the mass flow rate Q_M_vapeur_A of water vapor contained in the input fresh air as a function of the temperature T_air of the input fresh air, the air flow rate Qair obtained by the flow meter 24 and an estimate H of the ambient relative humidity, the latter being obtained by a humidity rate sensor located in the intake circuit Ca, for example in the flow meter 24 or external to the vehicle, or by a weather service, particularly if the vehicle is a "connected" vehicle.

[0114] Step 110 of estimating the mass M_eau also includes step 112 of estimating the mass flow rate Q_M_vapeur_E of the water vapor contained in the exhaust gas as a function of the fresh air flow rate Qair, the injected fuel flow rate Qcarb, the average composition of the fuel carb and the richness of combustion, taking into account the total flow rate of the combustion gases leaving the engine, and step 113 of estimating the mass flow rate Q_M_EGR of the water vapor in the EGR duct 38 as a function of the mass flow rate Q_M_E of the water vapor contained in the exhaust gas and the EGR rate Tx_EGR.

[0115] Step 110 of estimating the mass M_eau further comprises a step 114 of estimating the mass flow rate Q_M_vapeur_Ca of the mixture of fresh air and EGR burnt gases upstream of the air compressor 18b as being equal to the sum ΣQ_M of the mass flow rate Q_M_vapeur_A of the water vapor contained in the fresh air intake and the mass flow rate Q_M_vapeur_EGR of the water vapor in the EGR duct 38, calculated in step 115.

[0116] Step 110 of estimating the mass M_eau further comprises a step 116 of estimating the mass flow rate Q_M_WCAC of liquid water condensing on the inner walls of the heat exchanger 30 as a function of the mass flow rate Q_M_vapeur_Ca of the mixture of fresh air and burnt EGR gases upstream of the air compressor 18b, the temperature T_WCAC of the inner walls and the boost pressure value Psuralim, the temperature T_WCAC being obtained, for example, by measuring the temperature of the refrigerant flowing through the heat exchanger 30 by means of one or more sensors arranged upstream and / or downstream of the heat exchanger 30.

[0117] The step 110 of estimating the mass M_eau also comprises a step 117 of estimating the engine mass flow Q_M as a function of the air flow Qair, the fuel flow Qcarb and the EGR rate Tx_EGR, a step 118 of estimating the mass flow rate of water evaporated in the heat exchanger 30 Q_M_eau_evap as a function of said engine mass flow Q_M and of the temperature of the gases passing through the heat exchanger 30 T_gaz_WCAC, and a step 119 of estimating the engine volumetric flow Q_V as a function of said engine mass flow Q_M and of the temperature of the gases passing through the heat exchanger 30 T_gaz_WCAC.

[0118] Step 110 of estimating the mass M_eau further includes step 120 of estimating the mass M_eau of liquid water remaining on the surface of the inner wall of the heat exchanger 30 as the time integral ∫ΔQ_M of the difference ΔQ_M between the mass flow rate Q_M_WCAC of liquid water condensing on the inner wall of the heat exchanger 30 and the mass flow rate Q_M_eau_evap of water evaporating within the heat exchanger 30. This difference ΔQ_M is calculated in step 121.

[0119] The time integral ∫ΔQ_M is saturated at a maximum limit M_eau_max calculated in step 122. The maximum limit M_eau_Max corresponds to the maximum mass of liquid water that can reside in the heat exchanger 30 given the volumetric flow rate Q_V of gas passing through the heat exchanger 30.

[0120] Depending on the geometry of the heat exchanger 30, its inclination and the gas-side material that makes up its exchange surface, the mass of water that can be retained by the heat exchanger 30 can be characterized as a function of the gas flow rate Q_V passing through the heat exchanger 30.

[0121] The specification of the maximum limit M_eau_Max has been described above and will not be repeated in the remainder of this description.

[0122] Step 110 of estimating the current liquid water mass M_eau makes it possible to identify the mass of water that the heat exchanger 30 can temporarily store without desorption into the combustion chamber.

[0123] The step 125 of determining the difference ΔM_eau between the mass of water M_eau and the critical mass MC of liquid water comprises a step 126 of determining the critical mass MC of water corresponding to the minimum mass of water that would extinguish the combustion if it arrived in the combustion chamber too quickly.

[0124] The critical mass of water MC corresponds to the mass of water that would risk extinguishing the combustion if a desorption phenomenon were to occur, for example, following a demand for acceleration, and a sudden increase in the airflow injected by the engine would result in a sudden increase in the engine volumetric flow Q_V up to the volumetric flow value at full load point at maximum engine power.

[0125] The determination of the critical mass MC of water is described above.

[0126] The step 125 of determining the difference ΔM_eau comprises a step 127 of subtraction between the mass of water M_eau and the critical mass MC of liquid water.

[0127] The step 130 of managing the maximum mass of water that can be stored by the heat exchanger 30 comprises a step 131 of determining one of the following options that make it possible to limit the mass of water stored in the heat exchanger 30 as a function of the engine conditions and operating point:

[0128] Thus, at low loads, when there is a need to intervene to limit the mass of trapped water in real time and there is no need to limit intake air temperature to limit knock or improve performance, priority may be given to, for example, increasing the temperature of the cooling fluid flowing through the heat exchanger 30. On the other hand, at high loads, it is preferable to reduce the EGR rate setpoint Tx_EGR in order to suppress the intake air temperature to limit knock or improve performance. At low ambient temperatures and when there is no risk to the cooling circuit, for example, it is preferable to increase the temperature of the cooling fluid flowing through the heat exchanger 30, but at warm ambient (or engine) temperatures this measure is ruled out. It should be noted that each of these measures may be used individually or simultaneously.

[0129] The step 130 of managing the maximum mass of water that can be retained by the heat exchanger 30 comprises a step 132 of reducing the EGR rate setpoint Tx_EGR in order to reduce the humidity, and therefore the liquid water, at the inlet of the heat exchanger 30. This reduction in the EGR rate setpoint may be continuous, i.e., applied as a maximum limit that should not be exceeded throughout engine use, or may be applied once for a set period of time, in order to reduce the mass of liquid water M_eau retained in real time on the inner walls of the heat exchanger 30.

[0130] The step 130 of managing the maximum mass of water that can be retained by the heat exchanger 30 comprises a step 133 of reducing the flow rate of the cooling fluid through the heat exchanger 30 by controlling a pump that supplies the cooling fluid. The effect of this is to increase the temperature T_WCAC of the inner walls of the heat exchanger 30, thus promoting evaporation of the water retained on the walls, and to increase the temperature T_WCAC of the mixture of air and EGR gases passing through the heat exchanger 30, which increases the evaporation rate of the water retained in the heat exchanger 30.

[0131] This reduction in the flow rate of the cooling fluid passing through the heat exchanger 30 may be continuous, i.e., applied as a maximum limit that must not be exceeded throughout the entire use of the engine, or may be applied only once for a specific period of time, in order to reduce the mass of liquid water M_eau retained on the inner walls of the heat exchanger 30 in real time.

[0132] Finally, the step 130 of managing the maximum mass of water that can be stored by the heat exchanger 30 comprises a step 134 of increasing the temperature of the cooling fluid circulating through the heat exchanger 30, in particular by means of a controlled calostat that makes it possible to determine whether or not liquid should be circulated in a radiator in order to increase the temperature T_WCAC of the walls of the heat exchanger 30.

[0133] If the motor vehicle is a hybrid vehicle equipped with a heat engine and at least one electric motor, step 130 of managing the maximum mass of water that can be retained by the heat exchanger 30 comprises step 135 of controlling the speed N and torque C of the electric motor to increase the flow rate taken in by the heat engine so as to remove the film of water retained on the walls of the heat exchanger 30.

[0134] Steps 132, 133 and 134 may be operated separately or simultaneously.

[0135] During step 130 of managing the maximum mass of water that can be retained by the heat exchanger 30, the EGR rate Tx_EGR, the flow rate Q_WCAC of the cooling fluid through the heat exchanger 30 and / or the temperature T_WCAC of the cooling fluid in the heat exchanger 30 can be controlled, and / or in the case of a hybrid vehicle, the speed N and torque C of the electric motor can be controlled, and these effects are cumulative.

[0136] The invention makes it possible to solve the problem of gradual condensation of liquid water in the charge air cooler in order to avoid the risk of both rapid desorption and extinguishing of engine combustion.

Claims

1. A method (100) for controlling an internal combustion engine (10) comprising at least one cylinder (12), an air intake manifold (14) to which air from the outside is supplied by a pipe (20) provided with a flow meter (24), a compressor (18b), a turbocharger (18), and a heat exchanger (30) downstream of the compressor (18b) and upstream of the air intake manifold (14), the internal combustion engine comprising, from upstream to downstream along the direction of flow of burned gases, an exhaust manifold (16), a turbocharger (18), a heat exchanger (30) downstream of the compressor (18b) and upstream of the air intake manifold (14). an exhaust circuit (Ce) comprising a turbine (18a) of a turbocharger (18) and a decontamination system (40) for the combustion gases of the internal combustion engine; and a partial recirculation circuit (38) for the exhaust gases at the intake, starting at a point in the exhaust circuit (Ce) downstream of the turbine (18a) and opening into the fresh air supply pipe (20) upstream of the compressor (18b) of the turbocharger (18), the partial recirculation circuit (38) comprising an EGR control valve (38c), A mass (M_eau) of liquid water retained on the inner wall of the heat exchanger (30) in real time is estimated; a difference in mass of water (ΔM_eau) between the mass of water (M_eau) and a predetermined critical mass of liquid water (MC) is determined; When the absolute value of the difference (abs(ΔM_eau)) is less than a threshold (S), the maximum mass of water that can be retained by the heat exchanger (30) is managed by reducing the EGR rate (Tx_EGR) by controlling the EGR control valve (38c), and / or by reducing the flow rate (Q_WCAC) of the cooling fluid passing through the heat exchanger (30) by controlling a pump configured to circulate the cooling fluid in the heat exchanger (30), and / or by increasing the temperature (T_WCAC) of the cooling fluid in the heat exchanger (30).

2. The step (110) of estimating the mass (M_eau) of the liquid water accumulated on the inner wall of the heat exchanger (30) in real time includes: a step (111) of estimating the mass flow rate of water vapor contained in the input ambient air (Q_M_vapour_A) as a function of the input ambient air temperature (T_air), the ambient air flow rate (Qair) and an estimate of ambient relative humidity (H); a step (112) of estimating the mass flow rate of water vapor contained in the exhaust gas (Q_M_vapour_E) as a function of the fresh air flow rate (Qair), the injected fuel flow rate (Qcarb), the average composition of the fuel (carb) and the richness of the combustion; a step (113) of estimating a mass flow rate (Q_M_vapeur_EGR) of water vapor in the partial EGR recirculation circuit (38) as a function of the flow rate (Q_M_vapeur_E) of the water vapor contained in the exhaust gas and the EGR rate (Tx_EGR); a step (114) of estimating a mass flow rate (Q_M_vapeur_Ca) of water vapor contained in a mixture of fresh air and EGR burned gases upstream of the compressor (18b) as being equal to the sum (ΣQ_M) of the mass flow rate (Q_M_vapeur_A) of the water vapor contained in the fresh air intake and the mass flow rate (Q_M_vapeur_EGR) of the water vapor in the EGR circuit (38); a step (116) of estimating a mass flow rate (Q_M_WCAC) of the liquid water condensing on the inner wall of the heat exchanger (30) as a function of a mass flow rate (Q_M_vapour_Ca) of the mixture of outside air and EGR burned gases upstream of the compressor (18b), a temperature (T_WCAC) of the inner wall, and a boost pressure value (Psuralim); a step (120) of estimating the mass (M_eau) of the liquid water remaining on the surface of the inner wall of the heat exchanger (30) as a function of a mass flow difference (ΔQ_M) between a mass flow rate (Q_M_WCAC) of the liquid water condensing on the inner wall of the heat exchanger (30) and a mass flow rate (Q_M_eau_evap) of evaporated water in the heat exchanger (30), the mass flow rate being determined as a function of a temperature (T_gaz_WCAC) of the gas passing through the heat exchanger (30) and a mass flow rate (Q_M) of the internal combustion engine; The method of claim 1 , comprising:

3. 3. The method of claim 2, wherein the step of estimating the mass of liquid water (M_eau) includes receiving a time integral value (∫ΔQ_M) of the mass flow difference (ΔQ_M) between the mass flow rate of the liquid water condensing on the inner wall of the heat exchanger (Q_M_WCAC) and the mass flow rate of the evaporated water in the heat exchanger (Q_M_eau_evap).

4. 4. The method of claim 3, wherein the time integral (∫ΔQ_M) of the mass flow difference (ΔQ_M) is permanently saturated at a predetermined maximum limit (M_eau_max) corresponding to the maximum mass of liquid water that can be retained in the heat exchanger (30) given a current volumetric flow rate of gas passing through the heat exchanger (30).

5. 5. The method of claim 4, wherein the step of estimating (110) the mass of liquid water retained in real time (M_eau) comprises a step of estimating (119) a volumetric flow rate (Q_V) of the internal combustion engine as a function of a temperature (T_gaz_WCAC) of gas passing through the heat exchanger (30), and the maximum limit (M_eau_max) is determined as a function of the volumetric flow rate (Q_V).

6. 6. The method according to claim 1, wherein during a step (125) of determining the difference in mass of water (ΔM_eau) between the mass of water (M_eau) and the critical mass of liquid water (MC), in a step (126) the critical mass of water (MC) is determined which corresponds to a minimum mass of liquid water that, if it reaches the combustion chamber, would result in extinguishing of combustion, and a subtraction is performed between the mass of water (M_eau) and the critical mass of water (MC).

7. 7. The method of claim 1, wherein the reduction of the EGR rate setpoint (Tx_EGR) is continuous or applied once for a predetermined period of time.

8. 8. The method of any one of claims 1 to 7, wherein the reduction in the flow rate of the cooling fluid through the heat exchanger (30) is continuous or applied once for a predetermined period of time.

9. 9. The method according to claim 1, wherein the motor vehicle is a hybrid vehicle equipped with a heat engine and at least one electric motor, and wherein the step of managing (130) the maximum mass of water that can be retained in the heat exchanger (30) comprises a step of controlling (135) the speed (N) and torque (C) of the electric motor to increase the flow rate of water sucked into the heat engine.

10. An electronic control unit (ECU) for an internal combustion engine (10), the internal combustion engine (10) comprising at least one cylinder (12), an air intake manifold (14) to which fresh air is supplied by a pipe (20) provided with a flow meter (24), a compressor (18b) of a turbocharger (18), and a heat exchanger (30) downstream of the compressor (18b) and upstream of the air intake manifold (14), the internal combustion engine comprising, from upstream to downstream along the direction of flow of burned gas, an exhaust manifold (16), a turbine (18a) of the turbocharger (18), and an exhaust circuit (Ce) comprising a decontamination system (40) for the combustion gases of the internal combustion engine; and a partial EGR recirculation circuit (38) for the exhaust gases at the intake section, starting at a point in the exhaust circuit (Ce) downstream of the turbine (18a) and opening into the fresh air supply pipe (20) upstream of the compressor (18b) of the turbocharger (18), the partial EGR recirculation circuit (38) comprising an EGR control valve (38c), the electronic control unit (ECU) comprising an engine control system (70), the engine control system (70) comprising: a module (72) for estimating the mass (M_eau) of liquid water retained on the inner wall of the heat exchanger (30) in real time; a module (74) for determining the difference in mass of water (ΔM_eau) between the mass of water (M_eau) and a predetermined critical mass of liquid water (MC); a module (76) for managing a maximum mass of water that can be retained by the heat exchanger (30), configured to reduce an EGR rate (Tx_EGR) by controlling the EGR control valve (38c) and / or reduce a flow rate (Q_WCAC) of the cooling fluid passing through the heat exchanger (30) by controlling a pump configured to circulate the cooling fluid in the heat exchanger (30) and / or increase a temperature (T_WCAC) of the cooling fluid in the heat exchanger (30), when the absolute value of the difference (abs(ΔM_eau)) is less than a threshold value (S); An electronic control unit comprising:

11. A motor vehicle comprising the electronic control unit according to claim 10.

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