Internal combustion engine with cooled exhaust gas recirculation and energy recovery

Abstract

Internal combustion engine (1) with - at least one cylinder, - an intake system (3) for supplying air to at least one cylinder, - an exhaust gas discharge system (2) for the discharge of exhaust gases, - an exhaust gas recirculation (4) comprising at least one recirculation line (4a), wherein at least one cooler (5) and at least one actuating element (7) for adjusting a predefinable quantity of exhaust gas to be recirculated are provided in the at least one recirculation line (4a), and - at least one cooler (5) equipped with a phase change material (5a), wherein the phase change material (5a) exists as either a liquid phase or a solid phase depending on the material temperature and stores heat as the material temperature increases and releases stored heat as the material temperature decreases, characterized in that the internal combustion engine is arranged to additionally heat exhaust gas extracted from the exhaust gas discharge system (2) as it flows through the cooler (5) and to supply it via the intake system (3) to the at least one cylinder of the unfired internal combustion engine (1).

Description

[0001] The invention relates to an internal combustion engine with - at least one cylinder, - an intake system to supply at least one cylinder with air, - an exhaust gas removal system for the removal of exhaust gases, and - an exhaust gas recirculation system comprising at least one recirculation line, wherein at least one cooler and at least one actuator for adjusting a predefinable quantity of exhaust gas to be recirculated are provided in the at least one recirculation line.

[0002] An internal combustion engine of the type mentioned is used as a motor vehicle drive and is described, for example, in European patent application EP 2 952 706 A1, in German patent DE 10 2017 102 104 B3, in German patent application DE 10 2008 044 711 A1, and in European patent application EP 2 025 912 A1. Within the scope of the present invention, the term "internal combustion engine" refers to diesel and gasoline engines, but also to hybrid internal combustion engines, i.e., internal combustion engines operated with a hybrid combustion process, as well as hybrid drives that, in addition to the internal combustion engine, comprise at least one further torque source for driving a motor vehicle, for example, an electric machine that can be connected to or is connected to the drive of the internal combustion engine and which delivers power instead of or in addition to the internal combustion engine.

[0003] In the development of internal combustion engines, constant efforts are made to minimize fuel consumption. Furthermore, a reduction in pollutant emissions is pursued in order to comply with future emission limits.

[0004] Internal combustion engines are increasingly being equipped with turbocharging, which is primarily a method of increasing performance by compressing the intake air required for the combustion process. This allows a larger mass of intake air to be supplied to each cylinder per combustion cycle. As a result, the fuel mass and thus the mean effective pressure can be increased.

[0005] Supercharging is a suitable means of increasing the power output of an internal combustion engine without changing its displacement, or of reducing the displacement while maintaining the same power output. In either case, supercharging leads to increased power output per unit volume and a more favorable power-to-weight ratio. If the displacement is reduced, the load spectrum can be shifted towards higher loads, resulting in lower specific fuel consumption, under the same vehicle conditions. Supercharging an internal combustion engine therefore supports efforts to minimize fuel consumption, i.e., to improve the engine's efficiency.

[0006] A suitable transmission design can also enable downspeeding, which further reduces specific fuel consumption. Downspeeding takes advantage of the fact that specific fuel consumption is generally lower at low engine speeds, especially under higher loads.

[0007] With targeted turbocharging design, advantages can also be achieved in terms of exhaust emissions. For example, with suitable turbocharging, nitrogen oxide emissions from diesel engines can be reduced without compromising efficiency. At the same time, hydrocarbon emissions can be favorably influenced. Carbon dioxide emissions, which correlate directly with fuel consumption, also decrease with lower fuel consumption.

[0008] To comply with future emission limits, further measures are necessary. A key focus of development work is the reduction of nitrogen oxide emissions, which are particularly relevant for diesel engines. Since the formation of nitrogen oxides requires not only excess air but also high temperatures, one approach to reducing nitrogen oxide emissions involves using combustion processes with lower combustion temperatures.

[0009] Exhaust gas recirculation (EGR), i.e., the recirculation of combustion gases from the exhaust side to the intake side, is a promising approach, as nitrogen oxide emissions can be significantly reduced with an increasing exhaust gas recirculation rate. The exhaust gas recirculation rate x AGR is determined to x AGR - m AGR / (m AGR + m Frischluft ), where m AGR the mass of recirculated exhaust gas and m FrischluftThis refers to the supplied fresh air. The oxygen provided via exhaust gas recirculation must be taken into account, if applicable.

[0010] To achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates may be required, on the order of x AGR The recirculation rate can be approximately 60% to 70% or more. Such high recirculation rates require cooling of the recirculated exhaust gas, which lowers the exhaust gas temperature and increases its density, allowing a larger mass of exhaust gas to be recirculated. Consequently, exhaust gas recirculation systems are regularly equipped with a cooler. The exhaust gas recirculation system of the internal combustion engine, which is the subject of the present invention, also features cooling, i.e., at least one EGR cooler, which has a coolant jacket that facilitates heat transfer between the exhaust gas and the coolant.

[0011] Problems can arise when introducing the recirculated exhaust gas into the intake system if the temperature of the recirculated hot exhaust gas decreases and condensation forms.

[0012] Firstly, condensation can form when the recirculated hot exhaust gas in the intake system comes into contact with and mixes with cooler fresh air. The exhaust gas cools down, while the temperature of the fresh air rises. The temperature of the mixture of fresh air and recirculated exhaust gas, i.e., the temperature of the combustion air, is lower than the exhaust gas temperature of the recirculated exhaust gas. As the exhaust gas cools, liquids previously present in gaseous form in the exhaust gas or combustion air, especially water, can condense if the dew point of a component of the gaseous combustion air stream is reached. This leads to condensation in the free combustion air stream, with impurities in the combustion air often serving as the starting point for the formation of condensate droplets.

[0013] Secondly, condensation can form when the recirculated hot exhaust gas or combustion air hits the inner wall of the intake system, since the wall temperature is usually below the dew point of the relevant gaseous components.

[0014] Condensate and condensate droplets are undesirable and lead to increased noise emissions in the intake system, potentially damaging the impeller blades of a compressor wheel in a turbocharger or exhaust gas turbocharger located in the intake system. The latter is associated with a reduction in the compressor's efficiency.

[0015] Regarding the problem of condensation described above, an EGR cooler can also be effective and helpful. Cooling the recirculated exhaust gas has the advantageous effect that the condensate forms not in the intake system, but already during recirculation, and can be separated during this process.

[0016] A disadvantage of current EGR coolers is that the usable exhaust gas energy, i.e., the heat that can be extracted from the exhaust gas in the cooler using coolant, is only regularly available and usable when exhaust gas is recirculated. If exhaust gas recirculation is deactivated, so that no exhaust gas is recirculated, the energy of the hot exhaust gas often remains unused. If this exhaust gas energy could be used without restriction, i.e., recovered as part of an energy recovery system, further efficiency improvements could be achieved in the internal combustion engine.

[0017] The energy from the hot exhaust gas could, for example, be used to reduce friction and thus the fuel consumption of the internal combustion engine. Rapidly warming the engine oil using exhaust heat, especially after a cold start, could be beneficial in this regard. Rapid heating of the engine oil during the warm-up phase of the internal combustion engine leads to a correspondingly rapid decrease in the oil's viscosity and thus to a reduction in friction and frictional power, particularly in the oil-lubricated bearings, such as the crankshaft bearings.

[0018] The oil could, for example, be actively heated using a heating device. A coolant-operated oil cooler can be repurposed during the warm-up phase and used to heat the oil.

[0019] In principle, rapid heating of the engine oil to reduce friction can also be promoted by rapid heating of the internal combustion engine itself, which in turn is supported, i.e. forced, by ensuring that as little heat as possible is extracted from the internal combustion engine during the warm-up phase.

[0020] Therefore, in a liquid-cooled internal combustion engine, it can also be beneficial to supply heat to the engine cooling coolant, especially during the warm-up phase or after a cold start. Exhaust gas energy could be used to heat the engine cooling coolant.

[0021] German patent application DE 10 2008 020 408 A1 describes an internal combustion engine in which exhaust gas energy can be utilized even when no exhaust gas is recirculated, i.e., extracted from the intake system and fed into the exhaust system. The recirculation line can be selectively connected to either the intake system and / or the exhaust system downstream of the EGR cooler using a control valve that also serves as the EGR valve. Even with exhaust gas recirculation deactivated, when no exhaust gas is being recirculated, the energy of the hot exhaust gases can be used for energy recovery. The recovered energy is used either to heat the engine oil more quickly after a cold start, thereby reducing friction, or to heat the vehicle cabin.

[0022] A disadvantage of current EGR coolers is that they are not designed for effective energy recovery, but rather primarily for cooling the exhaust gas – i.e., the cooling effect alone. The cooler must be able to handle all exhaust gas volumes recirculated during the operation of the internal combustion engine. Particular attention must be paid to the maximum amount of exhaust gas to be recirculated and cooled. The wide range of exhaust gas volume recirculated results in highly variable pressure conditions across the cooler. The pressure differential across the cooler changes noticeably depending on the amount of exhaust gas recirculated, to such a significant degree that it must be considered when controlling or adjusting the recirculation rate. This interaction leads to a certain degree of dynamics and necessitates a correspondingly complex and sophisticated control system for the exhaust gas recirculation.

[0023] In light of the above, the object of the present invention is to provide an internal combustion engine according to the preamble of claim 1 in which the exhaust gas energy can be used more effectively than according to the prior art and which is further improved with regard to exhaust gas recirculation.

[0024] This task is solved by an internal combustion engine with - at least one cylinder, - an intake system to supply at least one cylinder with air, - an exhaust gas removal system for the removal of exhaust gases, and - an exhaust gas recirculation system comprising at least one recirculation line, wherein at least one cooler and at least one actuating element for adjusting a predefinable quantity of recirculated exhaust gas are provided in the at least one recirculation line, characterized in that - at least one cooler is equipped with a phase change material, wherein the phase change material exists either as a liquid phase or as a solid phase depending on the material temperature and stores heat as the material temperature increases and releases stored heat as the material temperature decreases.

[0025] In the internal combustion engine according to the invention, at least one cooler of the exhaust gas recirculation is equipped with a phase change material, and several coolers can also be prepared with this material.

[0026] The phase-change material extracts heat from the hot exhaust gas that passes through the cooler, thus serving as an additional thermal sink and also as an energy storage medium. This means that the cooler equipped with phase-change material according to the invention can extract more energy from the exhaust gas than a conventional cooler using only the coolant. This offers advantages with large volumes of exhaust gas, which occur at high engine speeds or loads, and especially with high exhaust gas temperatures, which occur at high loads.

[0027] The cooler equipped with phase-change material according to the invention has a further significant advantage over conventional coolers. The phase-change material can, when needed, feed the energy extracted from and stored in the exhaust gas back into the exhaust gas, thus additionally heating the exhaust gas.

[0028] An advantageous effect of this cooler capability is that, for example, the cooling of the unfired internal combustion engine during overrun can be prevented or slowed down. According to the invention, exhaust gas extracted from the exhaust system is additionally heated as it flows through the cooler and fed to the cylinders of the unfired internal combustion engine via the intake system, thereby at least counteracting cooling. When restarting or re-firing the internal combustion engine, the operating temperature is reached more quickly than usual, resulting in advantages in efficiency and reduced pollutant emissions.

[0029] Furthermore, advantages arise when switching off the internal combustion engine, for example when parking the vehicle. When restarting the engine, faster warm-up can be achieved, particularly by heating the intake air using recirculated exhaust gas, which in turn improves efficiency and reduces pollutant emissions.

[0030] This effect will become increasingly important, as one concept for reducing fuel consumption involves switching off the internal combustion engine when there is no immediate power demand, instead of continuing to run it at idle (start-stop strategy). In practice, this means that at least when the vehicle is stationary, the internal combustion engine is switched off, i.e., out of operation, i.e., unfired.

[0031] Another application is stop-and-go traffic, such as that which occurs in traffic jams on highways and rural roads. In urban traffic, stop-and-go traffic is no longer the exception, but rather the rule, due to the existing and poorly coordinated traffic light systems and the increased volume of traffic.

[0032] The exhaust gas energy recovered in the radiator using the coolant can be used during the warm-up phase or after a cold start to heat the engine oil of the internal combustion engine, thereby reducing friction. In a liquid-cooled internal combustion engine, the exhaust gas energy can be used to heat the engine cooling coolant, thus accelerating the engine's warm-up process. Both measures improve or increase the efficiency of the internal combustion engine.

[0033] The at least one EGR cooler of the internal combustion engine according to the invention is designed both for effective cooling and for energy recovery, i.e., the utilization of the exhaust gas energy. Both aspects are taken into account according to the invention.

[0034] The internal combustion engine according to the invention thus solves the problem underlying the invention, namely to provide an internal combustion engine according to the preamble of claim 1 in which the exhaust gas energy can be used more effectively than according to the prior art and which is further improved with regard to exhaust gas recirculation.

[0035] The at least one return line of the exhaust gas recirculation according to the invention can belong to a low-pressure EGR or a high-pressure EGR.

[0036] Several coolers – for example, arranged in parallel – can be provided, which can be switched on successively and used to cool the recirculated exhaust gas. In this way, the cooling capacity of the EGR cooling system, or the number of EGR coolers, can be adapted to the volume of exhaust gas to be cooled. This has several advantageous effects.

[0037] The pressure gradient across a single cooler changes less during operation of the cooler, because the amount of exhaust gas to be cooled or handled by this cooler varies less.

[0038] At lower recirculation rates, a cooler can be used to cool the recirculated exhaust gas according to the invention. If the amount of recirculated and cooled exhaust gas then increases, another cooler can be activated – for example, when a predefined amount of exhaust gas is exceeded – to cool the exhaust gas and contribute to cooling the recirculated exhaust gas. Depending on the number of EGR coolers provided, for example, if three, four, or more coolers are provided, activation can occur multiple times or successively. The control or adjustment of the recirculation rate reacts less dynamically.

[0039] Advantageous are internal combustion engine designs in which the radiators form an integral structural unit. A pre-assembled module that includes the radiators and constitutes the entire cooling unit simplifies the assembly of the exhaust gas recirculation system and the internal combustion engine as a whole, thereby also reducing costs.

[0040] Engine designs in which the coolers are separate, individual units can also be advantageous. Following a modular principle, different exhaust gas recirculation systems or different internal combustion engines can then be implemented using individual coolers.

[0041] Advantageous are embodiments of the internal combustion engine in which turbocharging is provided. Reference is made to the advantages and explanations already mentioned in connection with turbocharging.

[0042] A cooler according to the invention must have at least one cavity or at least one container for receiving the phase-change material. A cavity or container for receiving the phase-change material could be formed as an integral part of the cooler during a manufacturing process. The cooler could have a modular design, with a cavity being formed during assembly that receives the phase-change material.

[0043] A cavity could be formed by encasing the actual cooler in a casing, creating a cavity between the cooler and at least one spaced-apart casing element, in which phase-change material is contained. The cooler, enlarged by the casing, then encompasses the container for holding the phase-change material.

[0044] For the reasons mentioned above, embodiments of the internal combustion engine are advantageous in which the at least one cooler has at least one cavity for receiving the phase change material.

[0045] Advantageous are embodiments of the internal combustion engine in which the at least one cavity is formed at least also using formwork elements.

[0046] The at least one cooler is preferably not a casting into which the at least one cavity is incorporated as an integral component during the casting process. Rather, a cooler is preferably a system constructed – for example, from sheet metal – in which the at least one cavity is formed during assembly using spaced-apart formwork elements.

[0047] Further advantageous embodiments of the internal combustion engine are discussed in connection with the dependent claims.

[0048] Advantageous are embodiments of the internal combustion engine in which the at least one cooler has at least one coolant jacket for energy recovery, which serves for heat transfer between the exhaust gas and the coolant.

[0049] Advantageous are embodiments of the internal combustion engine in which a first return line is provided, in which a first cooler is arranged and which can be connected upstream of the first cooler to the exhaust gas removal system and downstream of the first cooler to the intake system using at least one actuating element.

[0050] In this context, advantageous are embodiments of the internal combustion engine in which the first return line downstream of the first cooler can be selectively connected to the intake system and / or the exhaust system using at least one actuating element.

[0051] According to the above embodiment, the exhaust energy of the hot exhaust gas can also be used when exhaust gas recirculation is deactivated, by means of the first cooler, which can be selectively connected downstream to the intake system and / or the exhaust gas discharge system, for which purpose at least one actuating element serves, with which the exhaust gas lines can be switched accordingly, namely connected to the exhaust gas discharge system.

[0052] Even with exhaust gas recirculation deactivated, heat can be transferred from the exhaust gas to the coolant and the phase change material of the first cooler. The coolant flowing through the first cooler carries away the heat from its interior and makes it available for a specific use, while the phase change material stores the heat extracted from the exhaust gas, thereby increasing the efficiency of the internal combustion engine. In this way, the exhaust energy inherent in the exhaust gas can be utilized.

[0053] Advantageous are embodiments of the internal combustion engine in which the first return line branches off from the exhaust gas removal system by forming a first node and leads into the intake system by forming a second node.

[0054] In this context, advantageous are embodiments of the internal combustion engine in which a first actuating element is provided in the first return line at the second node.

[0055] The first actuator acts as an EGR valve and, when exhaust gas recirculation is activated, serves to adjust the recirculation rate, i.e., the amount of exhaust gas recirculated via the first recirculation line. The use of a combination valve located at the second junction allows for the measurement of the recirculated exhaust gas volume and, simultaneously, the throttling of the intake fresh air volume.

[0056] Such a combination valve could, for example, be a flap that can be pivoted around an axis running perpendicular to the fresh air flow in such a way that, in a first end position, the front of the flap blocks the intake system and simultaneously opens the return line, and in a second end position, the back of the flap covers the return line and simultaneously opens the intake system. An additional valve body, connected to the flap and thus mechanically coupled, either opens or closes the return line. While the flap serves to adjust the amount of air supplied via the intake system, the valve body regulates the amount of exhaust gas recirculated.

[0057] In this context, embodiments of the internal combustion engine are also advantageous in which an exhaust gas line is provided, which branches off from the first return line downstream of the first cooler by forming a third node and leads into the exhaust gas discharge system by forming a fourth node.

[0058] In this context, embodiments of the internal combustion engine in which a second actuating element is arranged at the fourth node are advantageous.

[0059] The second actuator can be used to connect the first cooler downstream to the exhaust system. In this case, the first cooler does not cool recirculated exhaust gas. Instead, it cools exhaust gas that has been extracted from the exhaust system and is being reintroduced into it. This means that the first cooler serves only for energy recovery, i.e., for utilizing the energy inherent in the exhaust gas.

[0060] Advantageous are embodiments of the internal combustion engine in which the second actuating element is a 3-way valve that has three line connections and three switching positions.

[0061] Advantageous are embodiments of the internal combustion engine in which the fourth node is located downstream of the first node in the exhaust gas discharge system.

[0062] In this embodiment, the exhaust back pressure upstream of the fourth node and thus also at the inlet to the exhaust gas recirculation can be specifically increased by adjusting the second actuating element towards the closing position.

[0063] This increases the driving pressure differential across the cooler. The exhaust gas is deprived of an escape route around the cooler, meaning it becomes more difficult to bypass it.

[0064] To generate the required pressure differential, an additional shut-off element can be provided upstream of the exhaust gas recirculation inlet in the intake system in order to reduce the pressure downstream of the shut-off element on the inlet side.

[0065] Advantageous are embodiments of the internal combustion engine in which at least one compressor, which can be driven by means of an auxiliary drive, is arranged in the intake system.

[0066] The advantage of a compressor driven by an auxiliary drive, i.e., a supercharger, compared to an exhaust gas turbocharger, is that the supercharger can always generate and provide the required boost pressure, regardless of the operating condition of the internal combustion engine. This is particularly true for a supercharger that is electrically driven by an electric motor and therefore independent of the crankshaft speed.

[0067] According to current technology, increasing power output using exhaust gas turbocharging across all engine speed ranges is difficult. A significant drop in torque is observed below a certain engine speed. This torque drop becomes understandable when considering that the boost pressure ratio depends on the turbine pressure ratio and / or turbine power. Reducing the engine speed results in a lower exhaust gas mass flow and thus a lower turbine pressure ratio and / or turbine power. Consequently, the boost pressure ratio also decreases at lower engine speeds. This is equivalent to a drop in torque.

[0068] However, embodiments of the internal combustion engine can be advantageous in which at least one exhaust gas turbocharger is provided, comprising a turbine arranged in the exhaust system and a compressor arranged in the intake system. In an exhaust gas turbocharger, a compressor and a turbine are arranged on the same shaft. The hot exhaust gas stream is fed to the turbine and expands within it, releasing energy and causing the shaft to rotate. The energy transferred from the exhaust gas stream to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor forces and compresses the intake air, thereby supercharging the cylinders. Advantageously, an intercooler is provided downstream of the compressor in the intake system, which cools the compressed intake air before it enters the at least one cylinder.The cooler lowers the temperature and thus increases the density of the intake air, so the cooler also contributes to better cylinder filling, i.e., a greater air mass. In a sense, compression occurs through cooling.

[0069] The advantage of an exhaust gas turbocharger compared to a turbocharger driven by an auxiliary drive is that an exhaust gas turbocharger utilizes the exhaust energy of the hot exhaust gases, while a turbocharger obtains the energy required for its drive directly or indirectly from the internal combustion engine and thus, at least as long as the drive energy does not come from energy recovery, adversely affects, i.e. reduces, the efficiency.

[0070] If it is not a turbocharger driven by an electric machine, i.e., electrically driven, a mechanical or kinematic connection for power transmission between the turbocharger and the internal combustion engine is regularly required, which also adversely affects or determines the packaging in the engine compartment.

[0071] To counteract a drop in torque at low engine speeds, internal combustion engine designs with at least two exhaust gas turbochargers are particularly advantageous. Reducing the engine speed results in a smaller exhaust gas mass flow and thus a lower boost pressure ratio.

[0072] By using multiple exhaust gas turbochargers, for example several exhaust gas turbochargers connected in series or parallel, the torque characteristics of a turbocharged internal combustion engine can be noticeably improved.

[0073] To improve the torque characteristics, in addition to at least one exhaust gas turbocharger, another compressor can also be provided, namely either a turbocharger driven by an auxiliary drive or a compressor of another exhaust gas turbocharger.

[0074] In this context, embodiments of the turbocharged internal combustion engine can be advantageous in which at least one return line leads downstream of the compressor into the intake system.

[0075] In a so-called high-pressure EGR system, the exhaust gas is introduced into the intake system downstream of the compressor. To provide or ensure the necessary pressure differential between the exhaust gas discharge system and the intake system for recirculation, the exhaust gas is preferably and regularly extracted from the exhaust gas discharge system upstream of the turbine in the case of an exhaust gas turbocharger. High-pressure EGR has the advantage that the exhaust gas does not pass through the compressor and therefore does not require any exhaust aftertreatment, such as in a particulate filter, before recirculation. Deposits in the compressor, which could alter the compressor's geometry, particularly the flow cross-sections, and thus reduce its efficiency, are not a concern.Condensation, if it occurs at all, takes place downstream of the compressor, which also heats the supplied charge air during compression and thus prevents or counteracts condensation.

[0076] However, embodiments of the turbocharged internal combustion engine can also be advantageous in which at least one return line leads upstream of the compressor into the intake system.

[0077] When operating an internal combustion engine with exhaust gas turbocharging and simultaneously using high-pressure EGR, a conflict can arise if the recirculated exhaust gas is taken from the exhaust gas discharge system upstream of the turbine and is no longer available to drive the turbine.

[0078] Increasing the exhaust gas recirculation rate simultaneously reduces the exhaust gas flow fed into the turbine. This reduced exhaust gas mass flow through the turbine results in a lower turbine pressure ratio, which in turn lowers the boost pressure ratio, equating to a lower compressor mass flow. In addition to the decreasing boost pressure, compressor operation may also be affected, particularly regarding the surge line. Furthermore, negative consequences can arise concerning pollutant emissions, such as increased soot formation in diesel engines during acceleration.

[0079] For this reason, concepts are needed that ensure sufficiently high boost pressures while simultaneously maintaining high exhaust gas recirculation rates. One solution is the so-called low-pressure EGR, which recirculates exhaust gas into the intake system that has already passed through the turbine. To achieve this, the low-pressure EGR system extracts exhaust gas from the exhaust system downstream of the turbine and preferably directs it upstream of the compressor into the intake system to create the pressure differential between the exhaust system and the intake system required for recirculation.

[0080] The exhaust gas recirculated via low-pressure EGR is mixed with fresh air upstream of the compressor. The resulting mixture of fresh air and recirculated exhaust gas forms the charge air, which is fed to the compressor and compressed. The compressed charge air is preferably cooled in a charge air cooler downstream of the compressor.

[0081] Since exhaust gas passes through the compressor, it is preferably subjected to exhaust gas aftertreatment downstream of the turbine. Low-pressure EGR can also be combined with high-pressure EGR.

[0082] For the reasons already mentioned, embodiments of the turbocharged internal combustion engine in which at least one return line branches off upstream of the turbine from the exhaust gas discharge system can therefore be advantageous.

[0083] Advantageous are embodiments of the turbocharged internal combustion engine in which the turbine of a planned exhaust gas turbocharger has a variable turbine geometry, allowing for further adaptation to the operation of the internal combustion engine by adjusting the turbine geometry or the effective turbine cross-section. Adjustable guide vanes are arranged in the turbine inlet area to influence the flow direction. Unlike the rotor blades of the rotating impeller, the guide vanes do not rotate with the turbine shaft.

[0084] If the turbine has a fixed, unchanging geometry, the guide vanes are not only stationary but also completely immobile in the inlet area, i.e., rigidly fixed, if a guide vane system is even provided. With a variable geometry, however, the guide vanes are indeed stationary but not completely immobile; they can rotate around their axis, allowing the flow towards the rotor blades to be influenced.

[0085] By adjusting the turbine geometry, it is possible to influence the exhaust gas pressure upstream of the turbine, thus influencing the pressure differential between the exhaust gas removal system and the intake system, and therefore the recirculation rate of the high-pressure EGR.

[0086] For the reasons already mentioned, embodiments of the turbocharged internal combustion engine in which at least one return line branches off downstream of the turbine from the exhaust gas discharge system can also be advantageous.

[0087] In this context, advantageous embodiments of the turbocharged internal combustion engine are those in which at least one exhaust aftertreatment system is provided in the exhaust system between the turbine and the at least one branching return line. Since exhaust gas passes through the compressor, it is preferably subjected to exhaust aftertreatment downstream of the turbine.

[0088] Advantageous are embodiments of the internal combustion engine in which a particulate filter is provided as an exhaust aftertreatment system for the aftertreatment of the exhaust gas.

[0089] To minimize soot emissions, a regenerative particulate filter is used, which filters and stores the soot particles from the exhaust gas. These soot particles are then intermittently burned off during the filter's regeneration process. Without catalytic assistance, the temperatures required for regenerating the particulate filter are approximately 550°C. Therefore, additional measures are regularly employed to ensure filter regeneration under all operating conditions.

[0090] The filter regeneration process introduces heat into the exhaust gas, increasing the exhaust gas temperature and thus the exhaust gas enthalpy. At the filter outlet, an energy-rich exhaust gas is therefore available, which can be used in the manner according to the invention.

[0091] It can also be advantageous to use a turbocharged internal combustion engine in which an oxidation catalyst is provided as an exhaust aftertreatment system for the aftertreatment of the exhaust gas.

[0092] Although oxidation of unburned hydrocarbons and carbon monoxide in the exhaust system occurs even without additional measures at sufficiently high temperatures and with adequate oxygen levels, these reactions quickly cease due to the rapidly decreasing exhaust gas temperature downstream and the consequent rapid reduction in reaction rate. Therefore, catalytic reactors are used, which, through the use of catalytic materials, ensure oxidation even at low temperatures. If nitrogen oxides also need to be reduced, this can be achieved in a gasoline engine by using a three-way catalytic converter.

[0093] Oxidation is an exothermic reaction, whereby the released heat increases the temperature and thus the enthalpy of the exhaust gas. A more energy-rich exhaust gas is therefore available at the outlet of the oxidation catalyst. In this respect, the provision of an oxidation catalyst is particularly useful and advantageous with regard to the utilization of exhaust gas energy according to the invention.

[0094] Advantageous are embodiments of the internal combustion engine in which a bypass line is provided to bypass the at least one cooler, which bridges the EGR cooler and with which the exhaust gas recirculated via exhaust gas recirculation can be introduced into the intake system by bypassing the cooler.

[0095] It can be advantageous to bypass the EGR cooling system, for example, to prevent additional heat from being introduced into the engine's liquid cooling system. This approach is particularly useful if the engine's liquid cooling system is already under heavy load, such as at full throttle. If exhaust gas recirculation is used for engine braking, it is also beneficial to return the hot exhaust gas uncooled.

[0096] Advantageous are embodiments of the internal combustion engine in which liquid cooling is provided to form engine cooling.

[0097] Advantageous are embodiments of the internal combustion engine in which the at least one cylinder head of the internal combustion engine is equipped with at least one coolant jacket integrated in the cylinder head to form liquid cooling.

[0098] Liquid cooling proves particularly advantageous in turbocharged engines, as the thermal load on turbocharged engines is significantly higher compared to conventional internal combustion engines. If the cylinder head has an integrated exhaust manifold, it is subject to a higher thermal load than a conventional cylinder head equipped with an external manifold. This places increased demands on the cooling system.

[0099] In this context, advantageous are embodiments of the internal combustion engine in which the liquid cooling has a cooling circuit that includes at least one exhaust gas recirculation cooler.

[0100] If at least one EGR cooler is integrated into the engine cooling circuit, many components and assemblies required to form a circuit generally only need to be provided in a single version, since these can be used for both the cooling circuit of the EGR cooler and that of the engine cooling, which leads to synergies and cost savings, but also results in a weight saving.

[0101] Preferably, only one pump for circulating the coolant and one container for storing the coolant are provided. The heat transferred to the coolant by the internal combustion engine and the EGR cooling system can be extracted from the coolant in a common heat exchanger.

[0102] The exhaust gas energy or heat absorbed by the coolant in the EGR cooling system can also be used more easily in this way, for example to heat the internal combustion engine or the engine oil.

[0103] The invention is described below using an exemplary embodiment and in accordance with the Fig. 1, Fig. 2, Fig. 3 and Fig. 4 described in more detail. This shows: Fig. 1 schematically the first embodiment of the internal combustion engine including exhaust gas recirculation in a first operating mode, Fig. 2 schematically the first embodiment of the internal combustion engine including exhaust gas recirculation in a second operating mode, Fig. 3 schematically the first embodiment of the internal combustion engine including exhaust gas recirculation in a third operating mode, and Fig. 4 schematically the first embodiment of the internal combustion engine including exhaust gas recirculation in a fourth operating mode.

[0104] Fig. Figure 1 schematically shows a first embodiment of the internal combustion engine 1 including exhaust gas recirculation 4.

[0105] The internal combustion engine 1 has an intake system 3 to supply the cylinders with charge air and an exhaust system 2 to remove the exhaust gases from the cylinders.

[0106] The internal combustion engine 1 is equipped with an exhaust gas turbocharger 6 for the purpose of turbocharging, which comprises a turbine 6b arranged in the exhaust gas discharge system 2 and a compressor 6a arranged in the intake system 3.

[0107] Furthermore, an exhaust gas recirculation system 4 is provided with a first recirculation line 4a, which branches off from the exhaust gas discharge system 2 downstream of the turbine 6b at a first junction 2a and flows into the intake system 3 upstream of the compressor 6a at a second junction 3a. A first actuator 7 is provided at the second junction 3a. The first actuator 7 is a combination valve 7a, which serves to adjust the recirculated exhaust gas quantity, i.e., the recirculation rate, and thus also to deactivate the exhaust gas recirculation system 4.

[0108] A cooler 5 is arranged in the first return line 4a. The cooler 5 has a coolant-carrying coolant jacket, which serves for heat transfer between the exhaust gas and the coolant and is fluidically connected or connectable to the engine cooling system 12. Using the coolant, the exhaust gas can be cooled and exhaust gas energy can be recovered or utilized.

[0109] The first cooler 5 is equipped with a phase change material 5a. Depending on the current material temperature, the phase change material 5a exists either as a liquid phase or as a solid phase, stores exhaust gas heat as the material temperature increases, and releases this stored heat back to the exhaust gas flowing through the cooler 5 as the material temperature decreases.

[0110] Therefore, the phase change material 5a can extract heat from the hot exhaust gas in one operating mode during cooling and act as an energy storage medium, and in another operating mode, it can release the stored energy back into the exhaust gas during heating. The cooler 5 equipped with phase change material 5a can extract more energy from the exhaust gas than conventional coolers and, furthermore, can introduce additional heat into the exhaust gas as needed.

[0111] A further exhaust gas line 11 is provided, which branches off from the first return line 4a downstream of the first cooler 5 by forming a third node 10 and flows into the exhaust gas discharge system 2 by forming a fourth node 2b.

[0112] The fourth node 2b is located downstream of the first node 2a in the exhaust system 2. A second actuator 8, designed as a 3-way valve 8a (i.e., with three line connections and three switching positions), is located at the fourth node 2b. This actuator connects the first return line 4a downstream of the first cooler 5 to the exhaust system 2 via the further exhaust line 11 and the fourth node 2b, or disconnects the further exhaust line 11 from the exhaust system 2.

[0113] In individual cases, the second actuating element 8 can serve as a throttling element to adjust, in particular increase, the exhaust pressure upstream in the exhaust system 2, which also increases the driving pressure gradient across the first cooler 5.

[0114] Consequently, the first cooler 5 can be used to cool recirculated exhaust gas, but also, when exhaust gas recirculation 4 is deactivated, for energy recovery. In the case of the Fig. In the first operating mode shown in Figure 1, the two actuators 7 and 8 are set such that both the recirculated exhaust gas is cooled and energy is recovered from the exhaust gas, which is taken from the exhaust gas discharge system 2 at the first node 2a and reintroduced into the exhaust gas discharge system 2 at the fourth node 2b. The following sections describe the process using the... Fig. 2 to 4 further operating modes explained.

[0115] Fig. Figure 2 schematically shows the first embodiment of the internal combustion engine 1 including exhaust gas recirculation 4 in a first operating mode. It is intended only as a supplement to Fig. 1 will be carried out, which is why reference is made to it. Fig. 1. The same reference symbols were used for the same parts or components.

[0116] In the second operating mode, the second actuator 8 disconnects the further exhaust gas line 11, and thus the first return line 4a along with the first cooler 5, from the exhaust gas discharge system 2. The first return line 4a, however, is connected to the intake system 3. The first and second actuators 7 and 8 are switched and set accordingly. The first cooler 5 cools only the recirculated exhaust gas.

[0117] Fig. Figure 3 schematically shows the first embodiment of the internal combustion engine 1 including exhaust gas recirculation 4 in a third operating mode. It is intended only as a supplement to the Fig. 1 and Fig. 2 will be carried out, which is why, incidentally, reference is made to the Fig. 1 and Fig. 2. The same reference symbols were used for the same parts or components.

[0118] In the third operating mode, the first actuator 7 disconnects the first return line 4a from the intake system 3. The second actuator 8 connects the further exhaust gas line 11, and thus the first return line 4a along with the first cooler 5, to the exhaust gas discharge system 2. The first cooler 5 does not cool any recirculated exhaust gas, but only exhaust gas that is extracted from the exhaust gas discharge system 2 at the first junction 2a and reintroduced into the exhaust gas discharge system 2 at the fourth junction 2b. The first cooler 5 therefore serves exclusively for energy recovery. The first and second actuators 7 and 8 are switched and set accordingly.

[0119] Fig. Figure 4 schematically shows the first embodiment of the internal combustion engine 1 including exhaust gas recirculation 4 in a fourth operating mode. It is intended only as a supplement to Fig. 2 will be carried out, which is why reference is made to: Fig. 2. The same reference symbols were used for the same parts or components.

[0120] In the fourth operating mode, the first and second actuators 7, 8 are as in Fig. Engine 2 is switched on or set. However, internal combustion engine 1 is out of operation, i.e., unfired.

[0121] The energy stored in the phase change material 5a of the cooler 5 is fed into the exhaust gas, which is taken from the exhaust gas discharge system 2 via return line 4a and introduced into the intake system 3, in order to additionally heat the exhaust gas and to prevent or slow down the cooling of the unfired internal combustion engine 1.

[0122] The exhaust gas extracted from the exhaust system 2 is additionally heated as it flows through the cooler 5 and is fed to the cylinders of the unfired internal combustion engine 1 via the intake system 3, so that the operating temperature of the internal combustion engine 1 does not drop or drops less quickly. Reference sign 1 internal combustion engine 2 Exhaust gas discharge system 2a first junction 2b fourth junction 3 Intake system 3a second junction 4 Exhaust gas recirculation 4a Return line, first return line 5 radiators, EGR cooler, first radiator 5a Phase change material 6 exhaust gas turbochargers 6a Compressor of the exhaust gas turbocharger 6b Turbine of the exhaust gas turbocharger 7 first actuating element 7a Combination valve 8 second actuator 8a 3-way valve 9 Exhaust aftertreatment system 10 third junction 11 exhaust pipe 12 Engine cooling EGR Exhaust Gas Recirculation m AGR Mass of recirculated exhaust gas m Frischluft Mass of supplied fresh air or combustion air x AGR Exhaust gas recirculation rate

Claims

[1] Internal combustion engine (1) with - at least one cylinder, - an intake system (3) for supplying air to at least one cylinder, - an exhaust gas discharge system (2) for the discharge of exhaust gases, - an exhaust gas recirculation (4) comprising at least one recirculation line (4a), wherein at least one cooler (5) and at least one actuating element (7) for adjusting a predefinable quantity of exhaust gas to be recirculated are provided in the at least one recirculation line (4a), and - at least one cooler (5) equipped with a phase change material (5a), wherein the phase change material (5a) exists as either a liquid phase or a solid phase depending on the material temperature and stores heat as the material temperature increases and releases stored heat as the material temperature decreases, characterized by, that the internal combustion engine is designed to additionally heat exhaust gas extracted from the exhaust system (2) as it flows through the cooler (5) and to supply it via the intake system (3) to at least one cylinder of the unfired internal combustion engine (1). [2] Internal combustion engine (1) according to claim 1, characterized by , that the at least one cooler (5) for the purpose of energy recovery has at least one coolant jacket carrying coolant, which serves for heat transfer between the exhaust gas and the coolant. [3] Internal combustion engine (1) according to claim 1 or 2, characterized by , that a first return line (4a) is provided in which a first cooler (5) is arranged and which can be connected upstream of the first cooler (5) to the exhaust gas discharge system (2) and downstream of the first cooler (5) to the intake system (3) using at least one actuating element (7). [4] Internal combustion engine (1) according to claim 3, characterized by, that the first return line (4a) downstream of the first cooler (5) can be optionally connected to the intake system (3) and / or the exhaust system (2) using at least one actuator (7, 8). [5] Internal combustion engine (1) according to claim 3 or 4, characterized by , that the first return line (4a) branches off from the exhaust system (2) by forming a first node (2a) and leads into the intake system (3) by forming a second node (3a). [6] Internal combustion engine (1) according to claim 5, characterized by , that a first actuating element (7) is provided in the first return line (4a) at the second node (3a). [7] Internal combustion engine (1) according to claim 5 or 6, characterized by, that an exhaust gas line (11) is provided which branches off from the first return line (4a) downstream of the first cooler (5) by forming a third node (10) and leads into the exhaust gas discharge system (2) by forming a fourth node (2b). [8] Internal combustion engine (1) according to claim 7, characterized by , that a second actuating element (8) is arranged at the fourth node (2b). [9] Internal combustion engine (1) according to claim 7 or 8, characterized by , that the fourth node (2b) is located downstream of the first node (2a) in the exhaust system (2). [10] Internal combustion engine (1) according to any one of the preceding claims, characterized by , that at least one compressor which can be driven by means of an auxiliary drive is arranged in the intake system (3). [11] Internal combustion engine (1) according to any one of the preceding claims, characterized by, that at least one exhaust gas turbocharger (6) is provided, comprising a turbine (6b) arranged in the exhaust gas discharge system (2) and a compressor (6a) arranged in the intake system (3). [12] Internal combustion engine (1) according to claim 10 or 11, characterized by , that at least one return line (4a) leads downstream of the compressor (6a) into the intake system (3). [13] Internal combustion engine (1) according to claim 10 or 11, characterized by , that at least one return line (4a) leads upstream of the compressor (6a) into the intake system (3). [14] Internal combustion engine (1) according to any one of claims 11 to 13, characterized by , that at least one return line (4a) branches off upstream of the turbine (6b) from the exhaust gas discharge system (2). [15] Internal combustion engine (1) according to claim 13, characterized by , that at least one return line (4a) branches off downstream of the turbine (6b) from the exhaust gas discharge system (2). [16] Internal combustion engine (1) according to claim 15, characterized by , that at least one exhaust aftertreatment system (9) is provided in the exhaust system (2) between the turbine (6b) and the at least one branching return line (4a). [17] Internal combustion engine (1) according to claim 16, characterized by , that a particulate filter is provided as an exhaust aftertreatment system (9) for the aftertreatment of the exhaust gas. [18] Internal combustion engine (1) according to any one of the preceding claims, characterized by , that liquid cooling is provided for the formation of engine cooling. [19] Internal combustion engine (1) according to claim 18, characterized by that the liquid cooling system has a cooling circuit which includes at least one exhaust gas recirculation cooler (5) (4).

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