INTERNAL COMBUSTION ENGINE WITH ONE COOLING CIRCUIT FOR DUAL FLOW MODULE

Description

Technical field of the invention

[0001] The present invention relates to an internal combustion engine of a motor vehicle.

[0002] The present invention relates more particularly to the field of cooling systems for internal combustion engines, in particular the cooling of the intake gases of a motor vehicle thermal engine.

[0003] It relates more particularly to a cooling system for an internal combustion engine, said cooling system comprising a heat exchanger connected to two high-temperature gas circulation circuits, in particular compressed air and burnt gases, and in which a heat transfer fluid circulates. State of the art

[0004] As is known, a motor vehicle equipped with a thermal engine comprises an air intake circuit for bringing fresh air, generally captured at the front of the vehicle and then filtered using an air filter, to the thermal engine.

[0005] Said thermal engine may also include a recirculation circuit for burnt gases which are captured from an engine exhaust line, i.e. downstream of the engine combustion chambers, and returned to the engine intake while being mixed with fresh air.

[0006] As is known, a heat engine may include a supercharging system to increase the performance of said engine. The supercharging system includes an air compression stage before it is admitted into the engine to be mixed with fuel. This compression stage may, for example, be associated with a turbine stage to together form a turbocharger or be an electric compression module.

[0007] To improve the efficiency of the said heat engine, the fresh air is compressed as it passes through the compression stage, which causes an increase in its temperature, which is likely to reduce the efficiency of the engine.

[0008] It is therefore known to pass the compressed air after the compression stage and upstream of the engine into a cooling stage commonly called a "precooler" which is formed by an air-water exchanger. In said exchanger, the air circulates in contact, for example, in tubes housed in a chamber in which circulates cooling water from an engine cooling circuit. The cooling circuit can, for example, pass through the engine to also cool parts of the engine brought to high temperature, such as the cylinder block and the cylinder head, the cooling water then taking on calories, and then through a radiator to allow said calories to be removed and evacuated. The circulation of the cooling water is carried out using a water pump driven by the heat engine or by an electric water pump.

[0009] The purpose of recirculating burnt gases to the intake is to reduce the emission of pollutants generated by combustion. Thus, burnt gases can be returned from the exhaust, i.e., downstream of combustion in the cylinders, to the engine's intake ducts. The gases are called recirculated gases. They are at high temperature and can be cooled before being reintroduced into the engine's intake. There are different types of recirculated burnt gases: high-pressure recirculated gases taken from the exhaust system upstream according to the direction of flow of the gases from pollution control devices such as a catalyst or nitrogen oxide (NOx) trap. Generally, the high-pressure recirculated burnt gases are taken directly from an exhaust manifold attached to an exhaust face of the cylinder head, on the lateral side opposite the intake face and are then sent to the intake ducts or into the intake manifold. low-pressure recirculated burnt gases taken from the exhaust system and in a known manner after a pollution control device. The low-pressure recirculated burnt gases are therefore taken downstream of an exhaust device and returned to the engine intake

[0010] As is known, the recirculated gases are cooled before being mixed with fresh or compressed air.

[0011] The invention relates to the cooling of compressed air and the cooling of recirculated gases.

[0012] Document US2011 / 0139133 describes an internal combustion engine that is equipped with a special cooling system. During a cold start of the engine, this "cooling" system is used to warm the engine using the heat released by the burnt gases.

[0013] To achieve this, the cooling system includes a heat exchanger that circulates a heat transfer fluid around the recirculated gas circuit, allowing the heat transfer fluid to recover some of the heat from the burnt gases. The heat transfer fluid then circulates around the cylinders and releases some of the recovered heat to them.

[0014] Document FR3079880-A1 proposes a heat exchanger for cooling high-pressure recirculated gases and a heat exchanger for cooling compressed air upstream of the heat engine's intake ducts.

[0015] The document proposes that both the recirculated gas and mixed air inlets face the engine's exhaust side, resulting in a compact but less efficient cooling system. Furthermore, the very high gas temperatures, particularly the temperature of the recirculated burnt gases, can cause the coolant to boil, which can damage or even destroy the heat exchanger.

[0016] Document US2015 / 167595A1 discloses an engine with a common intercooler for intake air and recirculated gases.

[0017] The aim of the invention is to remedy these problems and one of the objects of the invention is a cooling unit for a motor vehicle heat engine which comprises an engine block and two intake lines for recirculated air and gas which pass through said unit before admission into the engine block, said cooling unit allows optimal cooling of the recirculated air and gas in a reduced footprint. Presentation of the invention

[0018] The present invention relates to a heat engine according to claim 1.

[0019] Advantageously, the cooling casing comprises two coolant circulation branches which are parallel and in opposite directions to provide a reduced size of said casing with optimal cooling efficiency. Indeed, the path of the coolant allows for a maximum heat exchange surface with the air or hot gases with a reduced size.

[0020] The direction of the coolant flow is parallel to the circulation of the recirculated gases in the cooling sump and in the same direction in order to obtain a reduced exchange and avoid problems of boiling of the liquid.

[0021] According to other characteristics of the invention: the circulation of the coolant passes consecutively from a first cooling stage to the second cooling stage.

[0022] Advantageously, the two cooling stages are passed through in series by the coolant to control the cooling efficiency. This allows each cooling stage to be optimally arranged to obtain the best cooling efficiency for each recirculated air and gas circuit. the recirculated gas cooling stage is arranged downstream according to the direction of flow of the coolant in the crankcase.

[0023] Advantageously, the cooling of the recirculated gases follows the cooling of the fresh air in order to reduce the temperature differential between the coolant temperature and the recirculated gas temperature and to control the boiling of the liquid. the first cooling branch of the compressed air is connected to the second cooling branch of the recirculated gases by an intermediate distribution chamber. Advantageously, the casing comprises an intermediate distribution chamber arranged between the two circulation branches of the coolant in order to homogenize the temperature of the liquid between the two stages and control the cooling. the first cooling branch of the compressed air is connected to an inlet chamber 34a shaped to water the first branch.

[0024] Advantageously, the coolant enters via an inlet chamber shaped to direct the flow of liquid along the axis of the first cooling branch and allow watering of said first branch. the second recirculated gas cooling branch is connected to an outlet chamber shaped to collect and direct to the outlet the liquid flow from the second cooling branch.

[0025] Advantageously, the exit of the coolant from the casing is facilitated by an outlet chamber shaped to collect the flow of liquid from the second cooling branch and direct it towards the outlet port of the casing. the circulation of recirculated gases in the cooling stage is rectilinear.

[0026] Advantageously, the circulation of the recirculated gases through the cooling stage is rectilinear or substantially so as to reduce the pressure losses in the circulation of said gases. the circulation of compressed fresh air in the cooling stage is rectilinear.

[0027] Advantageously, the circulation of the compressed air through the cooling stage is rectilinear or substantially rectilinear to reduce the pressure losses of the air circulation and facilitate obtaining the cooling stage. the circulation of the compressed fresh air is parallel to the circulation of the coolant in the compressed air cooling stage.

[0028] According to the invention, the circulation of the compressed fresh air is parallel to the circulation of the coolant in the compressed air cooling stage in order to obtain the best efficiency of the cooling of the compressed air, the length of the path of the compressed air is then substantially equal to the length of the path of the coolant and therefore allows an optimal exchange between the air and the liquid. the circulation of compressed air is in the opposite direction to the circulation of the coolant.

[0029] According to the invention, the circulation of air parallel to and in the opposite direction to the circulation of the coolant in the cooling stage allows optimal cooling of the compressed air through an optimal exchange coefficient and a maximum exchange length. the casing comprises a coolant inlet and outlet arranged at a first end of the casing opposite the second end at which the distribution chamber is arranged.

[0030] According to the invention, the casing comprises coolant inlet and outlet ports arranged at one end opposite the other end at which the distribution chamber is arranged, thus forming a path of maximum length for the coolant in the two cooling stages.

[0031] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments of the invention given as non-limiting examples and represented in the appended drawings, in which: [ Fig. 1 ] is a schematic view of an air and gas circuit of a heat engine. [ Fig. 2 ] is a schematic view of a cooling casing according to the invention. [ Fig. 3 ] is a schematic top sectional view of the cooling casing.

[0032] In the following description, identical reference numerals designate identical parts or parts having similar functions.

[0033] As known, according to the figure 1 , a thermal engine 50 of a motor vehicle comprises an intake circuit 10 which brings fresh air or a mixture of air and gas to the intake of the engine block 51. The air and the gases are then introduced into combustion chambers, each chamber is delimited by a cylinder, a chamber roof defined in a cylinder head and a piston sliding along the axis of the cylinder.

[0034] The so-called fresh air is generally captured from the front of the motor vehicle. It is directed into the fresh air intake circuit 11 which passes successively through an air filter 12, a compression stage 14 and a cooler 16. The compression stage can be formed by an electric or mechanical compressor, or a compressor connected to a turbine, the assembly being known as a turbocharger 13.

[0035] As the air passes through compression stage 14, it is heated. The temperature may have increased by a few dozen degrees (around 50°C), which is likely to reduce the engine's efficiency.

[0036] To improve the efficiency of said heat engine, the compressed fresh air passes into a cooling stage 16 arranged upstream of the engine block, which is commonly called a “precooler”. The “precooler” is formed by an air-water exchanger.

[0037] In said exchanger 16, the air circulates in contact, for example, in tubes housed in a chamber in which water-based coolant circulates, coming from a cooling circuit of the engine. The cooling circuit can pass, for example, through the engine to also cool parts of the engine brought to high temperature, such as the cylinder block and the cylinder head, the cooling water then being loaded with calories, and then through a radiator to allow said calories to be removed and evacuated. The circulation of the cooling water is carried out by means of a water pump driven by the heat engine or by an electric water pump (not shown).

[0038] To reduce pollutant emissions generated by combustion in the engine, it is known to return burnt gases from the exhaust to the intake of the said engine. The burnt gases are called recirculated gases. They are mixed with fresh air before being introduced into the engine.

[0039] Burnt gases can be returned from the exhaust, i.e. downstream of combustion in the cylinders, to the engine's intake ducts. They are at high temperature and need to be cooled before being reintroduced into the engine's intake. There are different types of recirculated burnt gases or EGR gas for "Exhaust Gas Recirculation": high-pressure recirculated gases taken from the exhaust system upstream according to the direction of flow of the gases from pollution control devices such as a catalyst or nitrogen oxide (NOx) trap. Generally, these gases are taken directly from an exhaust manifold attached to an exhaust face of the cylinder head and are then sent to the intake ducts or into an intake manifold. low-pressure recirculated burnt gases taken from the exhaust system and in a known manner after a pollution control device. The low-pressure recirculated burnt gases are therefore taken downstream of an exhaust device and returned to the engine intake

[0040] The recirculated gases are at high temperature and therefore need to be cooled before being introduced into the engine. They pass through a recirculated gas cooler 18.

[0041] The invention proposes to group the compressed air exchanger 16 with the recirculated gas exchanger 18 in a cooling unit 100 comprising a single cooling casing 19 as shown in figure 2 .

[0042] The cooling casing therefore includes: a coolant circuit 30 with an inlet orifice 31 and an outlet orifice 32, which are preferentially connected to the cooling circuit of the engine 50. The two orifices 31, 32 are arranged at the same first end 19a of the casing 19. a cooling stage 20 of the compressed air with an air inlet 21 and an air outlet 22 diametrically opposed. The cooling casing 19 is substantially parallelepipedal in shape, the air inlet 21 is for example via a lateral face 21' and the air outlet 22 is via the opposite lateral face 22'.

[0043] Preferably, the path of the compressed air in the cooling stage 20 is rectilinear to reduce the pressure losses in the circulation of the compressed air. The compressed air can be directed into tubular and rectilinear passage ducts which join the air inlet 21' to the air outlet 22'. a recirculated gas cooling stage 25 with an inlet 26 and an outlet 27 of said gases diametrically opposed.

[0044] Preferably, the path of the recirculated gases in the cooling stage 25 is rectilinear and along the largest dimension of the parallelepiped of the casing 19. The inlet of the recirculated gases 26 is for example via a lateral face 26' and the outlet of the gases 27 is via the opposite lateral face 27'. The recirculated gases are directed into tubular and rectilinear passage conduits which join the inlet of the gases 26 to the air outlet 27 along the largest dimension of the casing 19.

[0045] According to the figure 3 , the circuit 30 of the coolant inside the casing 19 has a U shape.

[0046] A liquid inlet orifice 31 is located at a first end 19a of the casing. Said orifice is extended towards the outside of the casing for an inlet nozzle connected to the engine cooling circuit. Said inlet orifice 31 opens inside the casing into an inlet chamber 34a shaped to allow optimal watering of a first cooling branch 33. Said inlet chamber may comprise for example a curvature or a deflector to direct the coolant along the axis of the first branch 33. Said first cooling branch 33 extends from the first end 19a of the casing towards the second end 19b opposite along the largest dimension of the casing 19. The first branch 33 opens into a distribution chamber 34b which extends transversely to the first branch 33. Said distribution chamber is arranged at the second end 19b opposite the casing 19.The distribution chamber is shaped to collect the liquid and substantially homogenize the characteristics of the liquid before returning to a second cooling branch 35. Said distribution chamber also has a curvature or a deflector to direct the cooling liquid towards the second cooling branch, in particular along the axis of the second branch 35, allowing the second cooling branch to be watered.

[0047] According to the invention, said distribution chamber is made up of the following consecutive portions, according to the direction of flow of the cooling liquid: a first collection portion with, for example, a reduction in the fluid passage section to form a convergent, a second transverse portion having a constant fluid passage section and a third diffusion portion with, for example, an increase in the passage section. Said three portions make it possible to avoid recirculation of the liquid and to improve the circulation of the liquid by avoiding zones of zero speed of said liquid.

[0048] The second cooling branch 35 is parallel to the first branch 33. The coolant circulates in this second branch 35 in the opposite direction to that in the first branch 33, from the distribution chamber 34b to an outlet chamber 34c which is connected with the outlet orifice 32, then returning to the first end 19a of the casing 19.

[0049] The outlet chamber 34c is also shaped to collect the liquid arriving from the second branch and direct it towards the outlet orifice 32. To do this, said outlet chamber has a curvature or a deflector to direct the flow of coolant.

[0050] It should be noted that the curvatures of the inlet chambers 34a, distribution chamber 34b and outlet chamber 34c are all directed towards the inside of the casing.

[0051] Each of said first and second branches 33, 35 may be a longitudinal chamber in which the conduits of compressed air and recirculated gas are bathed respectively.

[0052] According to a preferred embodiment of the invention, the recirculated gas cooling stage 25 is arranged downstream, in the direction of circulation of the cooling liquid, of the compressed air cooling stage 20.

[0053] In this way, the coolant passes first into the compressed air cooling stage 20 and is therefore not heated by exchanges with the recirculated gases. The temperature differences between the coolant and the compressed air therefore remain sufficient to have a significant heat exchange.

[0054] The conduits or tubes for passing the recirculated gases in the cooling stage of said gases are parallel to the second branch 35 of circulation of coolant. The direction of circulation of the recirculated gases is the same as the direction of circulation of the coolant, that is to say from the second end 19b to the first end 19a of the casing 19 along the large dimension. The circulation of the recirculated gases 28 is therefore parallel and in the same direction as the circulation of coolant in the second branch 35. In this clever way, the heat exchanges between the recirculated gases and the coolant are less significant, which reduces the risks of boiling of said liquid. The circulation of the recirculated gases relative to the coolant is called "co-flow" in English or in the direction of the current.

[0055] The compressed air passage ducts or tubes are parallel to the first liquid circulation branch 33. However, the compressed air circulates in the opposite direction to the liquid in said first branch, that is to say, the compressed air circulates from the second end 19b towards the first end 19a of the casing, while the liquid circulates from the first end 19a towards the opposite second end 19b. The circulation of compressed air 23 is therefore parallel and in the opposite direction to the circulation of coolant in the first branch 33. The heat exchange coefficient is thus greater, which allows optimal cooling of the compressed air. The circulation of compressed air relative to that of the liquid is called "counter-flow" in English or counter-current.

[0056] The objective is achieved: the cooling unit 100 with the casing 19 housing the two cooling stages 20, 25 respectively of compressed air and recirculated gas is compact and makes it possible to avoid risks of boiling of the coolant while providing optimal cooling of the compressed air and the recirculated gases independently of each other.

Claims

1. Heat engine (50) for a motor vehicle comprising: - an engine block (51), - an air intake circuit (10) having a cooling unit (100) comprising a single cooling housing (19) in which coolant circulates and which is suitable for housing: - a fresh air cooling stage (20), - a high-pressure recirculated gas cooling stage (25), wherein the liquid path in the housing comprises two parallel and oppositely directed circulation branches (33,35), one of the two branches being parallel and co-directional with a circulation (28) of the recirculated gases in the recirculated gas cooling stage (25), the circulation of the compressed fresh air (23) is parallel to the circulation of the coolant (33) in the compressed air cooling stage, and the circulation of compressed air (23) is in the opposite direction to the circulation of the coolant (33) in the cooling stage (20), characterized in that the housing (19) comprises a coolant inlet port (31) and a coolant outlet port (32) arranged at a first end (19a) of the housing opposite a second end (19b) at which a distribution chamber (34b) is arranged, said distribution chamber consisting in particular of the following consecutive portions, according to the direction of flow of the coolant: - a first collection portion having in particular a reduction of the fluid passage cross-section to form a convergent region, - a second transverse portion with a constant fluid passage cross-section, and - a third diffusion portion having in particular an increase in the passage cross-section.

2. Engine (50) according to claim 1, characterized in that the circulation of the coolant (33,35) passes consecutively from a first cooling stage (20) to the second cooling stage (25).

3. Engine (50) according to claim 1 or 2, characterized in that the recirculated gas cooling stage (25) is arranged downstream of the compressed air cooling stage (20) in the direction of flow of the coolant in the housing.

4. Engine (50) according to any of claims 1 to 3, characterized in that the first cooling branch (33) for the compressed air is connected to the second cooling branch (35) for the recirculated gases by an intermediate distribution chamber (34b).

5. Engine (50) according to any of claims 2 to 4, characterized in that the first cooling branch (33) for the compressed air is connected to an inlet chamber (34a) configured to wet the first branch.

6. Engine (50) according to any of claims 2 to 5, characterized in that the second cooling branch (35) for recirculated gases is connected to an outlet chamber (34c) configured to collect the flow of liquid coming from the second cooling branch (35) and direct it towards the outlet (32).

7. Engine (50) according to any of claims 1 to 6, characterized in that the circulation (28) of the recirculated gases in the cooling stage (25) is rectilinear.

8. Engine (50) according to any of claims 1 to 7, characterized in that the circulation of the compressed fresh air (23) in the cooling stage (20) is rectilinear.