DE102019114932A1 - Method for an internal combustion engine with an exhaust gas turbocharger and exhaust gas turbocharger system, in particular for an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine with an exhaust gas turbocharger, the exhaust gas turbocharger (2) being able to be driven with the aid of an additional drive (21), and with a charge air cooler (8) in an intake line (4) of the internal combustion engine (1) for Cooling of the charge air to be supplied to the internal combustion engine (1) is arranged, and wherein the exhaust gas turbocharger (2) has a rotor (27) comprising a turbine wheel (16) which is non-rotatably connected to a compressor wheel (18) by means of a shaft (17) , wherein the turbine wheel (16) in a flowable exhaust gas guide section (5) of the exhaust gas turbocharger (2), the compressor wheel (18) in a flowable fresh air guide section (3) of the exhaust gas turbocharger (2) and the shaft (17) in a bearing section (28) of the Exhaust gas turbocharger (2) are stored. According to the invention it is provided that - a geometric compression ratio of the internal combustion engine (1) is decoupled from an effective compression ratio, the effective compression ratio being smaller than the geometric compression ratio, - exhaust gas emerging from the internal combustion engine (1) completely in the full operating range of the internal combustion engine (1) applied to the turbine wheel (16), and a boost pressure of the internal combustion engine (1) can be raised so that a pressure in the cylinder (12) corresponding at least to the geometric compression ratio is achieved with the inlet and outlet channels (13, 14) of the internal combustion engine (1) closed . The invention also relates to an exhaust gas turbocharger system (26) for, in particular, an internal combustion engine.

Description

The invention relates to a method for an internal combustion engine with an exhaust gas turbocharger of the type specified in the preamble of patent claim 1 and an exhaust gas turbocharger system, in particular for an internal combustion engine according to patent claim 11.

It is known that highly charged internal combustion engines in particular have a tendency to knock. This means that due to correspondingly high temperatures in conjunction with corresponding pressures, uncontrolled combustion takes place in a cylinder of the internal combustion engine. This so-called knocking can be avoided with the aid of various measures, but this usually goes hand in hand with a loss of performance of the internal combustion engine.

According to the prior art, an internal combustion engine is equipped with an exhaust gas turbocharger for this purpose, an exhaust gas turbocharger system having the exhaust gas turbocharger having an additional drive for accelerating a running gear of the exhaust gas turbocharger. To avoid a deterioration in the response behavior of the rotor, the exhaust gas turbocharger is designed to be as small as possible in terms of its throughput. So that there is no risk of clogging, especially in the middle and upper load ranges of the internal combustion engine, a bypass channel of the exhaust gas turbocharger, which is used to bypass the turbine wheel fluidically, is opened. This represents a loss of efficiency of the internal combustion engine with the exhaust gas turbocharger, since exhaust gas from the internal combustion engine is passed unused past the exhaust gas turbocharger.

The object of the present invention is to provide a method for an internal combustion engine with an exhaust gas turbocharger which reduces the aforementioned disadvantages during operation of the internal combustion engine. Another object is to specify an exhaust gas turbo charger system that is particularly suitable for the method.

This object is achieved by a method for an internal combustion engine with an exhaust gas turbocharger with the features of claim 1. The further object is achieved with an exhaust gas turbocharger system with the features of claim 11. Advantageous configurations with expedient and non-trivial developments of the invention are specified in the remaining claims.

The invention relates to a method for operating an internal combustion engine with an exhaust gas turbocharger, wherein the exhaust gas turbocharger can be driven with the aid of an additional drive, and wherein a charge air cooler for cooling the charge air to be supplied to the internal combustion engine is arranged in an intake line of the internal combustion engine. The exhaust gas turbocharger has a rotor which has a turbine wheel which is connected in a rotationally fixed manner to a compressor wheel with the aid of a shaft. The turbine wheel is mounted in an exhaust gas routing section of the exhaust gas turbocharger that can be flowed through, the compressor wheel is mounted in a fresh air routing section of the exhaust gas turbocharger through which flow can flow, and the shaft in a bearing section of the exhaust gas turbocharger. According to the invention, a geometric compression ratio of the internal combustion engine is decoupled from an effective compression ratio, the effective compression ratio being smaller than the geometric compression ratio, and exhaust gas emerging from the internal combustion engine completely pressurizes the turbine wheel, and a boost pressure of the internal combustion engine can be increased so that it corresponds at least to the geometric compression ratio Pressure in the cylinder can be achieved with the inlet and outlet channels of the internal combustion engine closed. The advantage is that with the help of this method an efficient internal combustion engine can be brought about, the entire exhaust gas mass flow of which, or in other words the exhaust gas, is guided completely via the turbine wheel. This is provided in the entire operating range of the internal combustion engine. With the help of the adaptation of the boost pressure of the internal combustion engine, it is possible to realize a certain power of the internal combustion engine, even with a reduced boost pressure provided by the exhaust gas turbocharger, which corresponds to an output of an internal combustion engine designed according to the prior art, which has a knocking tendency.

The adjustment of the boost pressure of the internal combustion engine does not necessarily have to take place with the aid of the exhaust gas turbocharger. This could also be done by an additional, for example, mechanical compressor.

In one embodiment of the method according to the invention, the boost pressure is increased by increasing a speed of the shaft, the increase being implemented with the aid of the additional drive via an operatively connected coupling of the same to the shaft. Thus, no further device has to be provided to achieve the intended boost pressure, but the additional drive that is already provided can be used in particularly speed-reduced operating points of the exhaust gas turbocharger to increase its delivery rate.

In particular, the additional drive is an electric motor, which is preferably accommodated between the fresh air guide section and the bearing section in order to reduce a thermal load on the drive.

In a further advantageous embodiment, excess rotational energy of the shaft is fed into an energy-absorbing unit in the middle to upper load and speed ranges. The advantage is that the additional drive acts as a generator and, in particular, can supply a battery of the internal combustion engine with energy, as a result of which a further fuel-reduced internal combustion engine can be implemented with the method according to the invention.

To achieve the highest possible charge of the internal combustion engine, it has been shown to be advantageous to cool the charge air provided by the exhaust gas turbocharger before it enters the internal combustion engine, the charge air in particular being cooled in a charge air cooler which is arranged in an intake line of the internal combustion engine.

Closing times of the inlet valves in a range between 20 and 70 ° CA after or before a bottom dead center of a piston of the internal combustion engine have proven to be particularly favorable for achieving an efficient internal combustion engine.

With the method according to the invention, a further increase in the efficiency of the internal combustion engine can be brought about by regulating a flow to the turbine wheel. In other words, the exhaust gas flow directed to the turbine wheel is adapted with regard to its thermodynamic state by preferably regulating a flow cross section upstream of the turbine wheel, in particular directly in front of the turbine wheel. The regulation is preferably brought about with the aid of an adjustable diffuser. The adjustable diffuser is characterized by a plurality of guide vanes arranged rotatably over a circumference of the turbine wheel, whereby an effective flow cross section can be varied upstream of the turbine wheel.

To further reduce emissions and further increase the efficiency of the internal combustion engine, the method according to the invention provides for exhaust gas recirculation of exhaust gas flowing from the exhaust gas routing section upstream of the fresh air routing section, the recirculated exhaust gas being compressed in the fresh air routing section and cooled upstream of the internal combustion engine.

A second aspect of the invention relates to an exhaust gas turbocharger system, in particular for an internal combustion engine, having an exhaust gas turbocharger free of flow, comprising a flow-through exhaust gas duct section with a turbine wheel rotatably arranged in the exhaust gas duct section, a flow-through fresh air duct section with a compressor wheel rotatably arranged in the fresh air duct section, and a bearing section which has a turbine wheel the compressor wheel rotatably connects the shaft rotatably. An additional drive is designed to support a rotation of the shaft. Furthermore, a return duct is provided, which branches off at one end downstream of the turbine wheel from an outlet section of the exhaust gas turbocharger system and at the other end upstream of the compressor wheel opens into an inlet section of the exhaust gas turbocharger system. The advantage of the exhaust gas turbocharger system according to the invention is that, particularly at operating points of the exhaust gas turbocharger with a low air flow rate, exhaust gas flowing via the exhaust gas duct section can be at least partially conveyed into the fresh air duct section so that a desired boost pressure of the exhaust gas turbocharger can be provided. As a result, an internal combustion engine having the exhaust gas turbocharger system according to the invention can be operated with reduced consumption and emissions in particular. The advantage of a further reduction in consumption and emissions of the internal combustion engine arises when an exhaust gas cleaning unit is arranged downstream of the turbine wheel in the outlet section, since the recirculated exhaust gas can thus be fed to the fresh air duct section in a purified manner.

To cool and / or regulate the recirculated exhaust gas quantity, it is advantageous to form an exhaust gas cooling unit and / or a control element in the return duct after the turbine wheel and upstream of the compressor wheel, the control element being integrated into the exhaust gas cooling unit in a further advantageous embodiment of the exhaust gas turbocharger system. A compact exhaust gas turbocharger system can thus be made available.

• 1 in einer schematischen Darstellung eine Verbrennungskraftmaschine mit einem elektrisch unterstützten Abgasturbolader gemäß dem Stand der Technik, und
• 2 in einer schematischen Darstellung eine erfindungsgemäße Verbrennungskraftmaschine mit einem elektrisch unterstützten Abgasturbolader.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and with reference to the drawing. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination, but also in other combinations or on their own, without the scope of the Invention to leave. Show it:

• 1 in a schematic representation an internal combustion engine with an electrically assisted exhaust gas turbocharger according to the prior art, and
• 2 in a schematic representation an internal combustion engine according to the invention with an electrically assisted exhaust gas turbocharger.

An internal combustion engine with an exhaust gas turbocharger system designed according to the prior art 26th has an exhaust gas turbocharger 2 on, which has a flow-through fresh air guide section 3 in an intake manifold 4th the internal combustion engine 1 and an exhaust gas guide section through which a flow can flow 5 in an exhaust tract 6th the internal combustion engine 1 having arranged. Downstream of the exhaust gas routing section 5 is an exhaust gas cleaning unit 19th in the exhaust tract 6th positioned.

The fresh air duct section 3 is in the intake manifold 4th upstream of a throttle valve 7th positioned, with between the fresh air guide section 3 and the throttle 7th a charge air cooler 8th for cooling the exhaust gas turbocharger 2 compressed charge air is provided. Upstream of the fresh air duct section 3 is in the intake manifold 4th an air filter 9 arranged.

The internal combustion engine 1 has four cylinders in the exemplary embodiment presented 12th on which in a crankcase 10 the internal combustion engine 1 are trained. The crankcase 10 is a cylinder head 11 the internal combustion engine 1 assigned, in the flow-through inlet channels 13th are formed, with two inlet channels 13th to a cylinder 12th belong. Furthermore, the cylinder head 11 Through-flow outlet channels 14th on, taking each cylinder 12th two outlet channels 14th assigned. The number of inlet ports is a matter of course 13th and / or the number of outlet channels 14th as well as the number of cylinders 12th in particular according to a desired power and / or a desired torque of the internal combustion engine 1 selectable.

Every inlet port 13th and each exhaust port 14th is a closing element 15th assigned, which is designed in the present embodiment in the form of a poppet valve. To bring about a desired map of the load and speed of the internal combustion engine 1 show the closing elements 15th so-called timing and strokes. That the intake port 13th associated closing element 15th is an intake valve and that of the exhaust port 14th associated closing element 15th is an exhaust valve.

One in the exhaust gas routing section 5 rotatably arranged turbine wheel 16 is using a shaft 17th with one in the fresh air duct section 3 rotatably arranged compressor wheel 18th non-rotatably connected, creating a so-called running gear 27 is trained. The wave 17th of the running gear 27 is in one between the exhaust gas guide section 5 and the fresh air guide section 3 arranged storage section 28 rotatably recorded.

The turbine wheel 16 gets through via the exhaust ducts 14th flowing exhaust gas of the internal combustion engine 1 set in rotation, with the help of the shaft 17th the compressor wheel 18th is also set in rotation and thus the charge air is sucked in and compressed.

The exhaust gas routing section 5 is with a bypass channel to bypass the turbine wheel 16 executed, which in particular in an upper load and / or speed range of the internal combustion engine 1 is opened so that exhaust gas at the turbine wheel 16 can be passed by. That is, the exhaust gas turbocharger 2 the prior art is designed according to a so-called wastegate charger.

So in all operating points of the internal combustion engine 1 a desired charge air charge can be achieved is the exhaust gas turbocharger 2 as an electrically assisted exhaust gas turbocharger 2 formed, with an electric motor 21st the wave 17th drives. The electric motor 21st can also be used to feed energy into an energy source 22nd , for example. A motor vehicle battery.

According to 2 trained internal combustion engine 1 , which can be operated with a method according to the invention, has an exhaust-gas turbocharger system according to the invention 26th on, its turbine wheel 16 cannot be bypassed. In other words, that in the exhaust gas routing section 5 inflowing exhaust gas completely via the turbine wheel 16 to be led. This is therefore applied from the internal combustion engine 1 Exiting exhaust gas completely covers the turbine wheel 16 . In other other words, that means that the exhaust gas turbocharger 2 Is executed free of flow. For this there is a need for the turbine wheel 16 to be made correspondingly large, so in particular no charge change of the internal combustion engine 1 , hindering exhaust gas back pressure upstream of the exhaust gas routing section 5 arises. In other words, this means that the exhaust gas back pressure in one work cycle of the internal combustion engine 1 must not be too high, otherwise an uncontrolled backflow of exhaust gas into the cylinder may occur 12th with the exhaust valve open 15th he follows.

It is also a return channel 23 provided, which is downstream of the exhaust gas purification unit 19th from the exhaust tract 6th branching off and between the air filter 9 and the fresh air guide section 3 in the intake manifold 4th is formed opening out. In the return channel 23 are an exhaust gas cooler 24 and downstream of the exhaust gas cooler 24 a rule element 25th intended. With the help of the control element 25th becomes the one from the exhaust tract 6th The amount of exhaust gas flowing back is adjusted and into the intake line 4th guided. The return channel 23 is at one end downstream of the turbine wheel 16 from an exit section 29 of the exhaust gas turbocharger system 26th branching off and at the other end upstream of the compressor wheel 18th in an entry section 30th of the exhaust gas turbocharger system 26th converging trained.

Because of the compared to the so-called wastegate charger of the exhaust gas turbocharger system 26th according to the prior art, which via a bypass channel 20th to bypass the turbine wheel 16 and this in particular in the middle and upper load range of the internal combustion engine 1 is open, larger turbine wheel 16 of the exhaust gas turbocharger system according to the invention 26th is a mass moment of inertia of the exhaust gas turbocharger 2 also larger compared to the mass moment of inertia of the wastegate charger. This means that to achieve the same torques at the same speeds of the internal combustion engine 1 the drive of the shaft 17th by the electric motor 21st needs to be raised.

The method according to the invention, which is for the internal combustion engine 1 in thermodynamic coupling with the bypass-free exhaust gas turbocharger 2 is provided, is characterized in that the inlet valve 15th not as usual in the range of approx. 5-10 ° CA after or before a bottom dead center of a piston of the cylinder 12th closes, but in particular at least 20 ° CA after or before the bottom dead center of the piston. This reduces compression in the cylinder 12th present charge and accordingly is a geometric compression ratio of the internal combustion engine 1 of an effective compression ratio of the internal combustion engine 1 decoupled. The geometric compression ratio is characterized by the commonly known relation of the top dead center and the bottom dead center of the piston in the cylinder 12th out. The effective compression ratio, however, which is fundamentally smaller than the geometric compression ratio, has the point of the piston at the time of closing of the inlet valve instead of the bottom dead center 15th on. An example for decoupling the geometric compression ratio from the effective compression ratio is described above. A decoupling could also be achieved, for example, with the aid of control times of the exhaust valves or by changing the piston stroke.

With the aid of the decoupling, a combustion temperature of the charge that occurs during a working cycle can be reduced, so that, for example, uncontrolled burns, which can lead to so-called knocking, are prevented. However, there are no losses in terms of torque, respectively. the performance of the internal combustion engine 1 compared to one with the exhaust gas turbocharger system 26th internal combustion engine charged according to the prior art 1 occur is that of the exhaust gas turbocharger 2 charge air to be conveyed by increasing a speed of the shaft 17th to increase and preferably this downstream of the fresh air guide section 3 to cool. Thus the temperature of the cargo is in the cylinder 12th reduced, but the mass of the charge remains constant at every operating point compared to the prior art. This leads to a reduced temperature in the cylinder 12th , whereby the tendency to knock is eliminated.

As the increase in the speed of the shaft 17th cannot be achieved with the help of the exhaust gas and its enthalpy, is an additional drive 21st , preferably in the form of an electric motor to increase the speed of the shaft 17th intended. This happens in the lower load and speed range of the internal combustion engine 1 to a greater extent than in the upper load and speed range, in which it is particularly in the uppermost load and speed range of the internal combustion engine 1 is not a need. On the contrary, it could be in the upper load and speed range of the internal combustion engine 1 the electric motor 21st can be used as a generator and energy in, for example, a battery of the internal combustion engine 1 feed in.

Because the exhaust gas turbocharger 2 Is executed without bypassing, an efficiency of the internal combustion engine 1 by adjusting the timing of the intake and / or exhaust valves 15th can be increased significantly. The dynamic disadvantages of the exhaust gas turbocharger system according to the invention 26th are thereby due to the additional drive 21st compensated. The additional drive 21st is preferably between the bearing section 28 and the fresh air guide section 3 arranged to provide thermal decoupling from the shaft, especially at high speeds 17th hot exhaust gas routing section 5 bring about and achieve simple assembly in production.

Claims (14)

Method for operating an internal combustion engine with an exhaust gas turbocharger, the exhaust gas turbocharger (2) with the aid of an additional Drive (21) can be driven, and wherein a charge air cooler (8) for cooling the charge air to be supplied to the internal combustion engine (1) is arranged in an intake line (4) of the internal combustion engine (1), and wherein the exhaust gas turbocharger (2) has a running gear (27 ), comprising a turbine wheel (16) which is non-rotatably connected to a compressor wheel (18) with the aid of a shaft (17), the turbine wheel (16) in an exhaust gas guide section (5) of the exhaust gas turbocharger (2) through which a flow is possible, the compressor wheel ( 18) are mounted in a flow-through fresh air duct section (3) of the exhaust gas turbocharger (2) and the shaft (17) in a bearing section (28) of the exhaust gas turbocharger (2), characterized in that - a geometric compression ratio of the internal combustion engine (1) from an effective Compression ratio is decoupled, the effective compression ratio being smaller than the geometric compression ratio - from the internal combustion engine ne (1) exiting exhaust gas in the full operating range of the internal combustion engine (1) fully acts on the turbine wheel (16), and - a boost pressure of the internal combustion engine (1) can be raised so that a pressure in the cylinder (12) that corresponds at least to the geometric compression ratio when the inlet is closed - And outlet channels (13, 14) of the internal combustion engine (1) is achieved. Procedure according to Claim 1 , characterized in that the boost pressure takes place by increasing a speed of the shaft (17), the increase taking place with the aid of the additional drive (21) via an operatively connected coupling of the same to the shaft (17). Procedure according to Claim 2 , characterized in that the additional drive (21) is an electric motor. Procedure according to Claim 2 or 3 , characterized in that in the middle to upper load and speed ranges, excess rotational energy of the shaft (17) is fed into an energy-absorbing unit. Method according to one of the preceding claims, characterized in that the charge air provided by the exhaust gas turbocharger (2) is cooled before it enters the internal combustion engine (1). Procedure according to Claim 5 , characterized in that the charge air is cooled in a charge air cooler (8), the charge air cooler (8) in particular being arranged in an intake line (4) of the internal combustion engine (1). Method according to one of the preceding claims, characterized in that closing times of the inlet valves (15) are in a range between 20 and 70 ° CA after or before a bottom dead center of a piston of the internal combustion engine (1). Method according to one of the preceding claims, characterized in that a flow control of the turbine wheel (16) takes place. Procedure according to Claim 8 , characterized in that the regulation is brought about with the help of an adjustable guide apparatus. Method according to one of the preceding claims, characterized in that exhaust gas is recirculated from exhaust gas flowing out of the exhaust gas routing section (5) upstream of the fresh air routing section (3), the recirculated exhaust gas being compressed in the fresh air routing section (3) and cooled upstream of the internal combustion engine (1) . Exhaust gas turbocharger system, in particular for an internal combustion engine, having an exhaust gas turbocharger (2) free of flow, comprising an exhaust gas duct section (5) through which a flow can flow and a turbine wheel (16) rotatably arranged in the exhaust gas duct section (5), a fresh air duct section (3) which can flow through and a fresh air duct section (3) which is rotatable arranged compressor wheel (18), and a bearing section (28) which rotatably accommodates a shaft (17) connecting the turbine wheel (16) to the compressor wheel (18) in a rotationally fixed manner, and an additional drive (17) to support rotation of the shaft (17). 21), and with a return duct (23) which branches off at one end downstream of the turbine wheel (16) from an outlet section (29) of the exhaust gas turbocharger system (26) and at the other end upstream of the compressor wheel (18) into an inlet section (30) of the exhaust gas turbocharger system ( 26) opens out. Exhaust gas turbocharger system Claim 11 , characterized in that downstream of the turbine wheel (16) in the outlet section (29) an exhaust gas cleaning unit (19) through which a flow can flow is arranged. Exhaust gas turbocharger system Claim 11 or 12th , characterized in that an exhaust gas cooling unit (24) and / or a control element (25) is formed in the return duct (23) after the turbine wheel (16) and upstream of the compressor wheel (18). Exhaust gas turbocharger system Claim 13 , characterized in that the control element (25) is integrated into the exhaust gas cooling unit (24).

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