DE102013200630A1 - Method for operating engine system with internal combustion engine for motor car, involves introducing compressed air from compressed air source to end of exhaust stroke and prior to beginning of combustion cycle - Google Patents

Abstract

The method involves operating an internal combustion engine (2) in a two-stroke operation with directly consecutive combustion and exhaust strokes. A fuel-air mixture is ignited in a combustion chamber (31) of a cylinder (3) of the engine in a combustion cycle. Combustion exhaust gases are expelled by a compression movement of a piston (32) in the cylinder from the combustion chamber in an exhaust stroke. Compressed air is introduced from a compressed air source (11) to an end of the exhaust stroke and prior to the beginning of the combustion cycle. Independent claims are also included for the following: (1) an apparatus for operating an engine system (2) an engine system (3) a computer program comprising a set of instructions for operating an engine system.

Description

Technical area

The present invention relates to internal combustion engines, in particular internal combustion engines with air supply from a pressure vessel.

State of the art

Conventional internal combustion engines are typically operated in four-stroke operation, with two of the power strokes relating to the intake of fresh air into the combustion chamber and the compression of the intake fresh air to provide the fresh air in the cylinder at a desired pressure and in a desired amount.

Furthermore, two-stroke internal combustion engines are known, which have some advantages compared to four-stroke internal combustion engines. For example, the displacement / power ratio is significantly higher in two-stroke internal combustion engines, which makes them both lighter in weight and lower in cost.

However, two-stroke internal combustion engines also have significant drawbacks because their emission levels are very poor, especially because the amount of air in the cylinder can be poorly controlled, flushing losses occur and oil is present in the fresh air.

Disclosure of the invention

According to the invention a method for operating an internal combustion engine with an air supply from a pressure vessel according to claim 1 and the device, the motor system and the computer program product according to the independent claims are provided.

Further advantageous embodiments of the present invention are specified in the dependent claims.

According to a first aspect, there is provided a method of operating an engine system having an internal combustion engine with a source of pressurized air, wherein the internal combustion engine is operated in a two-stroke mode with immediately consecutive combustion and exhaust strokes, by injecting in the combustion stroke an air / fuel mixture in a combustion chamber of a cylinder the internal combustion engine is ignited and in the exhaust stroke combustion exhaust gases are ejected by a compression movement of a piston in the cylinder from the combustion chamber, wherein at the end of the exhaust stroke and before the beginning of the combustion cycle compressed air from a compressed air source is admitted.

One idea of the above method of operation is to provide a compressed air source for providing compressed air, such. As a pressure vessel to use to provide the required for the combustion process of fuel in the cylinders of the engine fresh air under pressure. There is provided an operating method in which, if provided by the compressed air source, a sufficient air pressure, the intake and compression strokes of the four-stroke operation is dispensed with and the cylinders are instead operated in a two-stroke operation. Instead of the conventional intake stroke, immediately after the exhaust stroke of combustion exhaust gas, pressurized fresh air is introduced into the cylinder, and then fuel is injected, so that immediately after the exhaust stroke, a combustion stroke may follow. In this way, the internal combustion engine can be operated in a two-stroke operation.

Furthermore, it can be provided that the internal combustion engine is only operated in two-stroke operation when the compressed air source provides compressed air at a pressure which is higher than a predefined pressure threshold value.

In particular, the internal combustion engine may be operated in a four-stroke operation with an intake stroke for drawing in fresh air and a compression stroke for compressing the intake fresh air when the compressed air source provides compressed air at a pressure less than the predetermined pressure threshold. If, in other words, the air pressure provided by the compressed air source drops below the predetermined pressure threshold value, the operation of the internal combustion engine can be switched back to a four-stroke operation so that the inflow of air into the cylinders is assisted by an intake stroke and the necessary pressure is provided by the compression stroke ,

According to one embodiment, it can be provided that the changeover between the two-stroke operation and the four-stroke operation is performed only after the exhaust stroke.

Further, during the exhaust stroke, an air valve of the cylinder may be opened, with the introduction of pressurized air into the cylinder beginning before the exhaust valve is closed.

According to a further aspect, an apparatus for operating an engine system with an internal combustion engine with a compressed air source is provided. The apparatus is adapted to operate the internal combustion engine in a two-stroke operation To operate immediately successive combustion and exhaust cycles by in the combustion stroke, a fuel / air mixture is ignited in a combustion chamber of a cylinder of the internal combustion engine and in the exhaust stroke combustion exhaust gases are ejected by a compression movement of a piston in the cylinder from the combustion chamber, and to the end of the exhaust stroke and before commencing the combustion stroke, to introduce compressed air from a compressed air source.

• – mindestens einen Zylinder mit einem Brennraum zum Durchführen einer Verbrennung eines Kraftstoff-/Luftgemischs;
• – eine Druckluftquelle zum Bereitstellen von komprimierter Frischluft;
• – jeweils mindestens ein Luftventil pro Zylinder zum Einlassen von komprimierter Frischluft aus dem Druckbehälter in den Brennraum des Zylinders; und
• – die obige Vorrichtung.

In another aspect, an engine system having an internal combustion engine is provided, comprising:

• - At least one cylinder with a combustion chamber for carrying out combustion of a fuel / air mixture;
• - A compressed air source for providing compressed fresh air;
• - Each at least one air valve per cylinder for admitting compressed fresh air from the pressure vessel into the combustion chamber of the cylinder; and
• - The above device.

According to a further aspect, a computer program is provided which is adapted to carry out all the steps of the above method.

Brief description of the drawings

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

1 a schematic representation of an engine system with an internal combustion engine, the air is supplied via a pressure vessel; and

2 a flowchart illustrating a method for operating the engine system of 1 ,

Description of embodiments

1 shows a schematic representation of an engine system 1 with an internal combustion engine 2 (In the embodiment shown, a gasoline engine), of which by way of example a cylinder 3 is shown. The engine system 1 serves for example for operating a (not shown) motor vehicle. The cylinder 3 includes a combustion chamber 31 , which at one end by a movable piston 32 is completed.

At one the piston 32 opposite cylinder head 33 is an ignition device 5 provided in a combustion stroke in the combustion chamber 31 of the cylinder 3 to ignite located fuel / air mixture and thereby an expansion movement of the piston 32 to effect.

Furthermore, a fuel injection valve 6 provided to fuel directly into the combustion chamber 31 of the cylinder 3 inject. In an exhaust stroke following the combustion stroke becomes an exhaust valve 7 in the cylinder head 33 opened and combustion exhaust gas via a Abgasabführungsabschnitt 8th pushed out.

Via an air valve 10 becomes the internal combustion engine 2 Fresh air is supplied from a pressure vessel 11 is removed. The pressure vessel 11 serves as a source of compressed air and is located in an area of the motor vehicle that has an ambient temperature or a temperature that is significantly lower than the temperature near the engine. The pressure vessel 11 may be formed, for example, of metal and / or of a fiberglass and / or composite material. In particular glass fiber material has the advantages of low weight and high pressure resistance.

Due to the pressure difference between the pressure vessel 11 and the combustion chamber 31 of the cylinder 3 the air flows when opening the air valve 10 in the combustion chamber 31 and relaxes here. This will make the cylinder 3 cooled as the expanding air cools.

The control of the air valve 10 , the ignition device 5 , the fuel injection valve 6 and the exhaust valve 7 via a control unit 15 , The control of the internal combustion engine 2 is essentially similar to the control of a conventional internal combustion engine, with only the opening of the air valve 10 for admitting a certain amount of air is made so that a predetermined, z. B. a possible stoichiometric, combustion of the air / fuel mixture in the combustion chamber 31 of the cylinder 3 can be done.

The dimension of the amount of fresh air to be injected into the combustion chamber can be determined by providing opening times for the air valves 10 be made, the control unit 15 about one on the pressure vessel 11 arranged pressure and temperature sensor 9 corresponding state variables in the pressure vessel 11 record and from this the appropriate opening times of the air valves 10 can determine.

The loading of the pressure vessel 11 with compressed air via a compressor 12 which is either electric motorized by means of an electric motor 13 or can be driven by another source of energy. The compressor 12 sucks over an air filter 16 Fresh air, compresses them and passes the compressed fresh air through a cooling device 17 for cooling the compressed fresh air into the pressure vessel 11 ,

By the compression of the fresh air in the pressure vessel 11 remove the resulting compression heat, the pressure vessel 11 continue with a cooling device, eg. B. with cooling fins, be provided. As a result, the heat generated there is dissipated into the environment.

Depending on the size of the pressure vessel 11 its additional use for an air conditioner can be provided, since the air conditioning valve 18 from the pressure vessel 11 Exhausted air cools due to their expansion and thus would be suitable for cooling the passenger compartment of a motor vehicle.

In the present embodiment, the compressor 12 continue via a Stirling engine 19 operated, the temperature difference between the exhaust side of the engine 2 and the environment uses a mechanical drive of the compressor 12 to effect.

The Stirling engine 19 includes two air cylinders 22 . 24 , each using a connecting rod with a drive wheel 20 are connected. A first air cylinder 22 is near the exhaust removal section 8th arranged there to absorb the heat of the combustion exhaust gas. The heat of the combustion exhaust gas is preferably added to the combustion exhaust via cooling fins 21 in the exhaust discharge portion 8th withdrawn and the first air cylinder 22 of the Stirling engine 19 fed.

By the heat removed from the combustion exhaust gas expands in the first air cylinder 22 located air volume and exerts a force on a first connecting rod 25 out, with the drive wheel 20 is driven. During a compression movement of the piston 32 in the first air cylinder 22 is the heated air through a regenerator 23 in a second air cylinder 24 pressed, which is remote from the motor and is thus in an environment with ambient temperature.

As the operating speeds of a Stirling engine 19 compared to that of the compressor 12 For the compression of fresh air required speed are low, a suitable translation must be provided to those of the Stirling engine 19 increase the speed provided.

The one from the first air cylinder 22 in the second air cylinder 24 transported air has a high temperature and becomes in the second air cylinder 24 , which may be provided in accordance with cooling fins, cooled, whereby the pressure in the cylinder chamber decreases and so a corresponding movement of the piston 32 of the second air cylinder 24 causes. This movement is via a second connecting rod 27 on the drive wheel 20 transfer.

Regarding the operation of the Stirling engine 19 In essence, reference is made to the prior art and is omitted herein to a more detailed description.

The use of the temperature of the combustion exhaust gas leads to no increased exhaust back pressure and thus causes no loss of efficiency during operation of the internal combustion engine 2 ,

Should have the compression performance of the Stirling engine 19 is not provided to maintain a pressure in the pressure vessel 11 sufficient, so can the electric motor 13 be switched on. This also applies to the warm-up operation of the internal combustion engine 2 in which there is insufficient temperature difference to the operation of the Stirling engine 19 is available.

The pressure vessel 11 represents a reservoir for all cylinders 3 of the internal combustion engine 2 dar. The volume of the pressure vessel 11 is preferably in proportion to the combustion chamber volume of the cylinder 3 of the internal combustion engine 2 chosen big. Preferably, the volume of the pressure vessel should be 11 at least 10 times the total maximum combustion chamber volume of all cylinders 3 be. The air pressure inside the pressure vessel 11 should be during operation of the internal combustion engine 2 at least 10 bar, preferably 20 bar, to allow a sufficiently fast intake of fresh air into the cylinder 3 to reach. It can be provided, the air pressure in the pressure vessel 11 to adapt to the respective requested load.

Alternatively or in addition to the Stirling engine 19 can also drive other power sources for the compressor 12 can be used, such as a turbine for converting the exhaust gas enthalpy of the combustion exhaust gas, as used for example in an exhaust gas driven supercharger (turbocharger).

The first air cylinder 22 of the Stirling engine 19 is to the Abgasabführungsabschnitt 8th coupled, wherein in the Abgasabführungsabschnitt 8th Heat conduction fins are provided to receive the heat of the combustion exhaust gas and the first air cylinder 22 be forwarded. By suitable shaping of the heat conduction fins and by a catalytic coating, the function of the catalyst with the function of heat transfer to the first air cylinder 22 of the Stirling engine 19 be combined.

Between the pressure vessel 11 and the second air cylinder 24 of the Stirling engine 19 as well as between the internal combustion engine 2 and the first air cylinder 22 of the Stirling engine 19 can be a thermal insulation 28 be provided to ensure that the pressure vessel 11 and the second air cylinder 24 of the Stirling engine 19 not by the waste heat of the internal combustion engine 2 to be heated.

The compressor 12 can be designed as an isothermal compressor, is compressed at the sucked fresh air and provided under elevated pressure at the same temperature as before. The isothermal compressor converts heat generated during compression of the fresh air into mechanical energy, for example by using the Stirling engine 19 , In this case, the heat generated by the compression of the intake fresh air becomes the first air cylinder 22 fed so that the extra heat energy from the compression to drive the compressor 12 is available again.

The compressed air is compressed higher than it is for the target pressure of the pressure vessel 11 is required. Thus, a higher temperature difference is achieved between a cold and a hot source, wherein a turbine converts the pressure difference between the intermediate state of the compressed air and the target pressure into mechanical energy. Ultimately, the isothermal compressor works in a similar way to other types of compressors.

The operation of the engine system described above 1 will be described below in connection with the flowchart of 2 explained in more detail.

In step S1, it is first queried which pressure in the pressure vessel 11 prevails as compressed air source. Is the pressure in the pressure vessel 11 higher than a predetermined pressure threshold value (alternative: yes), the method is continued with step S2. Otherwise (alternative: No), the method is continued with step S4.

In step S2, the internal combustion engine 2 operated in two-stroke operation. In this case, after the exhaust stroke for discharging the combustion exhaust gases is dispensed with an additional intake and the compression of the intake air. In the meantime, that of the pressure vessel 11 provided compressed air in a predetermined amount under a sufficient pressure in the cylinder 3 let in, so that to provide the fuel / air mixture before the ignition no further compression of the fuel / air mixture in the cylinder 3 is required. In this case, immediately after the injection process near the top dead center of the piston movement in the cylinder 3 an ignition in the cylinder 3 done and the combustion cycle to be performed. After passing through the bottom dead center by the piston movement in the cylinder 3 The combustion gases can be expelled and, as soon as the piston 32 in the cylinder 3 Coming closer to top dead center, compressed air can be re-injected into the cylinders 3 are introduced, followed by injecting fuel. The conventional four-stroke operation of the internal combustion engine 2 can thus be interrupted and instead a two-stroke operation can be ensured, which leads to a significant improvement in the efficiency of the internal combustion engine 2 can lead.

The onset of the two-stroke operation is preferably carried out after an exhaust stroke in a previous four-stroke operation, in which with the exhaust valve open 7 the combustion exhaust gases are emitted. After closing the exhaust valve 7 near the top dead center of the piston 32 is then compressed air in the cylinder 3 taken in and injected simultaneously or subsequently fuel to form a fuel / air mixture.

The inflow time for the compressed air can vary and a scavenging effect can be used when the inflow of compressed air occurs, while the exhaust valve in question is 7 is opened. Thereby, the combustion exhaust gases can be introduced by the inflow of the pressurized fresh air in the Abgasabführungsabschnitt 8th be ejected. This will give a complete air filling of the cylinder 3 achieved, which in particular in a very good dynamic behavior of a run in two-stroke internal combustion engine 2 shows.

After switching to the two-stroke operation, in step S3, the pressure in the pressure vessel 11 be queried. It is found that the pressure in the pressure vessel 11 falls below the predetermined pressure threshold (alternative: Yes), the method is continued with step S4. Otherwise (alternative: no), the program jumps back to step S2.

It is found that the pressure in the pressure vessel 11 is not sufficient, so in step S4, the internal combustion engine 2 operated in conventional four-stroke operation. This is at the end of the exhaust stroke at the beginning of the intake stroke, ie as soon as the piston 32 at top dead center, air over the air valve 10 in the cylinder 3 let in (with the exhaust valve closed 7 ). The remaining pressure of the introduced air supports the suction movement of the piston 32 ,

After the intake stroke, the corresponding air valve 10 closed and now in the cylinder 3 air is further compressed in a compression stroke. The air valve 10 assumes the role of the intake valve in a conventional internal combustion engine in this mode. The operation of the exhaust valve 7 in the combustion and exhaust stroke corresponds to the function in the conventional four-stroke operation of the internal combustion engine.

After switching to the four-stroke operation, in step S5, the pressure in the pressure vessel 11 be queried. It is found that the pressure in the pressure vessel 11 falls below the predetermined pressure threshold (alternative: Yes), the method is continued with step S2. Otherwise (alternative: No), a return is made to step S4.

In another embodiment, instead of an air valve 10 also two or more than two more air valves 10 per cylinder 3 be provided. This allows efficient partial load operation by operating only one air valve 10 (at each closed further air valves) can be achieved. This increases the life of both or all air valves 10 and reduces the required actuation energy. Furthermore, by operating only a portion of the air valves 10 the air turbulence can be increased, resulting in a more homogeneous fuel / air mixture in the combustion chamber of the cylinder 3 leads. At the same time, at full load by controlling and corresponding opening of all air valves 10 a larger amount of compressed air into the cylinders 3 be introduced. The through the several air valves 10 Reduced redundancy increases the reliability of the internal combustion engine 2 clear.

Claims (10)

Method for operating an engine system ( 1 ) with an internal combustion engine ( 2 ) with a compressed air source ( 11 ), wherein the internal combustion engine ( 2 ) is operated in a second cycle operation with immediately successive combustion and exhaust strokes, by in the combustion stroke, a fuel / air mixture in a combustion chamber of a cylinder ( 3 ) of the internal combustion engine ( 2 ) is ignited and combustion exhaust gases in the exhaust stroke by a compression movement of a piston in the cylinder from the combustion chamber ( 31 ), whereby compressed air from a compressed air source ( 11 ) is admitted to the end of the exhaust stroke and before the start of the combustion stroke. Method according to claim 1, wherein the internal combustion engine ( 2 ) is only operated in two-stroke operation when the compressed air source ( 11 ) Provides compressed air at a pressure higher than a predetermined pressure threshold. Method according to claim 2, wherein the internal combustion engine ( 2 ) is operated in a four-stroke operation with an intake stroke for sucking in fresh air and a compression stroke for compressing the intake fresh air when the compressed air source ( 11 ) Provides compressed air at a pressure lower than the predetermined pressure threshold. The method of claim 3, wherein the change between the two-stroke operation and the four-stroke operation is performed only after the exhaust stroke. Method according to one of claims 1 to 4, wherein during the exhaust stroke an air valve ( 10 ) of the cylinder ( 3 ), wherein the admission of compressed air into the cylinder ( 3 ) begins before the exhaust valve ( 7 ) is closed. Device for operating an engine system with an internal combustion engine ( 2 ) with a compressed air source ( 11 ), wherein the device is designed to operate the internal combustion engine ( 2 ) operate in a two-stroke operation with immediately successive combustion and exhaust strokes, by in the combustion stroke a fuel / air mixture in a combustion chamber ( 31 ) of a cylinder ( 3 ) of the internal combustion engine ( 2 ) is ignited and combustion exhaust gases in the exhaust stroke by a compression movement of a piston in the cylinder ( 3 ) from the combustion chamber ( 31 ) and compressed air from a compressed air source ( 11 ) at the end of the exhaust stroke and before the start of the combustion stroke. Engine system ( 1 ) with an internal combustion engine ( 2 ), comprising: - at least one cylinder ( 3 ) with a combustion chamber ( 31 ) for performing combustion of an air / fuel mixture; - a compressed air source ( 11 ) for providing compressed fresh air; - at least one air valve ( 10 ) per cylinder ( 3 ) for introducing compressed fresh air from the pressure vessel ( 11 ) in the combustion chamber ( 31 ) of the cylinder ( 3 ); and - an apparatus according to claim 6. Computer program which is set up to carry out all the steps of a method according to one of Claims 1 to 5. An electronic storage medium on which a computer program according to claim 8 is stored. An electronic control device comprising an electronic storage medium according to claim 9

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