DE102017122759A1 - Method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine, comprising the steps of: providing a fuel (2) converting a portion of the fuel into a matched fuel (7) during operation of the internal combustion engine, the adjusted fuel (7) having a lower ignitability as the unchanged fuel (2) - supply of the adjusted fuel (7) to a cylinder (1) of the internal combustion engine supply of unchanged fuel (2) to the cylinder (1) of the internal combustion engine, in particular for triggering the ignition, wherein the supply of unchanged Fuel (7) is supplied to the cylinder during the compression stroke of the adjusted fuel in the cylinder, - driving a piston (9) of the internal combustion engine through the ignition. The invention further relates to a corresponding internal combustion engine and a control unit.

Description

The application relates to a method for operating an internal combustion engine. These are externally or self-ignited internal combustion engines with at least one cylinder. In the cylinder is a piston, which is driven by the ignition of a fuel-air mixture.

State of the art

Such internal combustion engines are widely used. As far as thermodynamically possible high efficiencies are achieved especially with diesel engines. However, this is usually accompanied by increased emissions of soot particles and nitrogen oxides. These have to be removed from the exhaust gas with a complex exhaust gas purification system.

In many cases, fuels - often referred to as fuels in connection with internal combustion engines - are vaporized and / or converted in order to achieve efficient and low-emission combustion.

From the DE 10 2010 012 945 A1 a device for the evaporation of liquid fuels is known. In this case, a central air supply is provided, which is permeable to air axially and radially. A catalyst system is arranged concentrically around the air supply at least over part of its length. Concentric around it a buffer zone is arranged around which in turn an absorbent material for fuel distribution is arranged concentrically.

From the DE 34 42 628 A1 It is known to feed a lean mixture into a cylinder of an internal combustion engine and introduce a richer mixture or fuel at the end of compression. This then allows the ignition.

From the WO 2017/085301 A1 For example, a method of adjusting the ignition property of a fuel using a unit having at least one distribution zone, at least one oxidation zone, and at least one conversion zone is known. In the distribution zone, which has a distribution structure, fuel is distributed, oxidized in the oxidation zone at least a portion of the fuel with at least one oxidizing agent on at least one catalyst on a catalyst support and fed in the conversion zone, at least a portion of the distributed fuel and / or another Fuel is thermally and / or catalytically converted. The method is characterized in that the ignition of the fuel is adjusted by the molar ratio of oxygen contained in the oxidizing agent to the oxygen required for complete oxidation of the fuel present, and / or the pressure in the unit and / or the residence time and / or the temperature ,

From the US 2005/0011486 A1 It is known to convert part of the fuel during operation of an internal combustion engine to produce a more volatile fuel. The converted fuel is used to ignite the unconverted fuel.

From the WO 2004/036015 A1 a HCCI engine is known in which a portion of the fuel is catalytically converted. Among other things, by choosing the ratio of converted fuel, unconverted fuel and air, the combustion timing is adjusted depending on engine parameters.

Object of the invention and general solution

Object of the present invention is to provide a method to operate an internal combustion engine such that on the one hand a high efficiency is achieved and on the other hand, low pollutant emissions. The invention also relates to a control unit designed for carrying out the method and to an internal combustion engine with a conversion unit.

It was recognized that for this purpose a method for operating an internal combustion engine with the following steps makes sense:

First, a fuel is to be provided. Different fuels are conceivable. Thus, the fuel can be selected from the group diesel, gasoline, and fuels with additives, power-to-fuel fuels (such as Fischer-Tropsch fuels, oxymethylene ethers, methyl formates, dimethyl carbonates), alcohol, especially ethanol, ethers, ketones , Biofuels (octanol, biodiesel), propane, butane, methane, etc. as well as blends and mixtures. This list should make it clear that a variety of fuels is conceivable.

In practice, the provision of fuel means that the fuel is routed from a tank provided in the rule to the internal combustion engine. More specifically, the part of the fuel to be converted is first to be led to a conversion unit in which the ignition property can be adjusted / changed. The modified fuel has different ignition characteristics than the original fuel. The changed fuel is mixed with the combustion air. The ignition characteristic is changed so that it comes to no premature ignition during compression. The fuel-air mixture is then ignited via a diesel direct injection or via a spark plug.

Further, a conversion of a portion of the fuel into a matched fuel during operation of the internal combustion engine is provided, wherein the adjusted fuel has a lower ignitability than the unmodified fuel. The statement that this is done during operation of the internal combustion engine, should not rule out that, for example, before the start of the operation of the internal combustion engine is already started with the conversion, the conversion even in short breaks - such as a standing at the traffic light motor vehicle - or a short Period of time after the shutdown of the engine continues to operate. However, it should be differentiated from the dual-fuel technology in which, for example, in a refinery from a fuel an adapted fuel is produced and two tanks for the internal combustion engine, ie a tank for adjusted fuel and a tank for unchanged fuel, are provided. The dual-fuel technology is well known and numerous publications confirm that this can reduce emissions. As a rule, two separately entrained fuels of different fuel properties are used. According to the invention, only a single fuel is carried along to solve the problem. In addition to more logistical considerations that make refueling and carrying two fuels difficult, especially in a motor vehicle, there is still a significant technical consideration. In the conversion, the fuel is usually not only converted, but also evaporated. It is therefore - if you want to avoid consuming and energy-consuming compression - due to the high volume of the gaseous fuel - not possible to store the converted fuel in a motor vehicle to a significant extent. Therefore, the conversion must be done during operation of the internal combustion engine.

In the present case, a conversion, in particular a catalytic conversion, of the fuel is set. This is a difference from the one mentioned above DE 34 42 628 A1 , The success of the pollutant reduction seems to be mainly due to the conversion.

It should also be noted that in this case a conversion into a fuel with a lower ignitability is provided. The above described approach of US 2005/0011486 A1 may be beneficial in many cases. However, it has been found that the objective pursued "low pollutant emissions and high efficiency" can be successfully achieved with this approach.

Furthermore, a supply of the adjusted fuel to a cylinder of the internal combustion engine has to take place. For the sake of clarity, there is always talk of a cylinder. Of course, the method is usually used in internal combustion engines with multiple cylinders. Since the same thing happens in all cylinders, at least with regard to the present invention, the representation of further cylinders is omitted here.

Likewise, a supply of unchanged fuel to the cylinder of the internal combustion engine, in particular for triggering the ignition, to take place. It is therefore possible to operate the internal combustion engine so that no or an unsatisfactory ignition would take place without the supply of unchanged fuel. This also enables the efficient and low-emission ignition. The ignition can also be done by an ignition electrode (spark ignition).

The supply of unchanged fuel to the cylinder takes place during the compression phase in the cylinder. The injection time of the unchanged fuel is chosen so that an optimized operation in terms of emissions and consumption takes place. In particular, if no ignition device is present and thus the ignition is to be triggered solely by the supply of the unchanged fuel, this results from the usual operation of the internal combustion engine, in which the ignition takes place when the piston is in the "upper" range. In the common representations and the usual mounting position, this is actually the top, although this is often technically advantageous, but not mandatory. Nevertheless, should be spoken of the upper range. Accordingly, the point at which the piston changes its direction of movement, commonly referred to as top dead center.

As usual, the driving of a piston of the internal combustion engine is effected by the ignition.

In another embodiment, the conversion of the unmodified fuel into at least two batches of the adjusted fuel that differ in their ignitability occurs, but the ignitability of the two batches is always lower than the ignitability of the unmodified fuel. Thus, a first matched fuel with low ignitability and a second matched fuel with higher ignitability are provided.

Furthermore, a supply of the first adjusted fuel to a cylinder of the internal combustion engine has to take place. Likewise, a supply of the second adapted fuel to the cylinder of the internal combustion engine, in particular for triggering the ignition, to take place.

It is therefore possible to operate the internal combustion engine so that no or an unsatisfactory ignition would take place without supply of the second adapted fuel with higher ignition capability. This also enables the efficient and low-emission ignition. The ignition can also be done by an ignition electrode (spark ignition).

The supply of the second adjusted fuel to the cylinder takes place during the compression phase in the cylinder. The injection timing of the second adjusted fuel is chosen to provide optimized operation in terms of emissions and consumption. In particular, if no ignition device is present and thus the ignition should be triggered solely by the supply of the second adjusted fuel, this results from the usual operation of the internal combustion engine, in which the ignition takes place when the piston is in the "upper" range.

As usual, the driving of a piston of the internal combustion engine is effected by the ignition.

In most embodiments, no change to the internal combustion engine is required to perform the method except for the unit for converting the fuel. In a classically operated diesel engine, the combustion air is compressed and diesel injected at the end of the compression. If in the present case adapted fuel, which is normally in gaseous form, is mixed with the combustion air and supplied to the cylinder, and likewise injected diesel at the end of the compression - admittedly in a smaller amount, since already adapted fuel has been introduced into the cylinder - then the same internal combustion engine can be used be used. Only the control has to be adjusted, but this can be done by an update of the engine control software. This implies that by a manageable retrofitting, namely the installation of a unit for converting the fuel into a matched fuel and an update of the engine control software, the inventive method can be performed.

This is a crucial aspect, as many vehicles powered by diesel engines produce inadmissible and undesirable pollutant emissions. The present invention allows a solution of the problem with reasonable effort.

In one embodiment, the choice of the ratio between the unchanged fuel and the adjusted fuel depends on the operating state of the internal combustion engine. Thus, the combustion can be optimized. For example, it may make sense at low power to convert relatively less fuel in order to inject enough unchanged fuel to trigger the ignition.

From the above-mentioned WO 2004/036015 A1 While it is known that by choosing the ratio of converted to unconverted fuel, the ignition timing can be affected. However, there is no teaching from the supply of the unchanged fuel to do so. In the present case, moreover, the ignition time is determined considerably from the time of supply of the unchanged fuel, unless the ignition device is performed by an additional ignition device.

In an important embodiment, the method is operated in such a way that a minimization of pollutant emissions, in particular the emission of fine dust and / or nitrogen oxides, and / or fuel consumption is achieved. There are often conflicting goals between the goals of reducing fuel consumption and reducing pollutant emissions.

Thus, high combustion temperatures are advantageous for high efficiency. High combustion temperatures are also favorable to reduce the formation of soot particles. However, high combustion temperatures also favor the formation of nitrogen oxides. This example is intended to show that it is usually not possible to minimize pollutant emissions and fuel consumption by, for example, aiming for the minimization of a pollutant without taking into account other pollutants and fuel consumption. It is rather an optimization taking into account all relevant parameters. The reduction of carbon dioxide emissions is presently not mentioned as a goal, since this is achieved anyway by reducing fuel consumption. It should be noted that the reduction of fuel consumption in the present case is not the focus, since the efficiency is often largely optimized. A currently pressing problem is pollutant emissions, which according to current findings lead to non-negligible health problems.

In one embodiment, the adjusted fuel is mixed with the combustion air to a charge gas. By supplying the charging gas into the cylinder of the internal combustion engine, the supply of the adjusted fuel takes place. After conversion, the fuel is usually present in gaseous form. Therefore, it is possible to introduce the adjusted fuel together with the combustion air. This often leads to improved mixing of adapted fuel and combustion air. Improved by this Mixture formation can be reduced within the engine, the harmful soot and NOx emissions. This also allows an unchanged structure of the cylinder. The combustion air must be supplied in any case. In this respect, no change in the structure of the cylinder is required.

In one embodiment, the timing of the supply of the unchanged fuel relative to the position of the piston in the cylinder is selected depending on the operating state of the internal combustion engine. As already mentioned, it is clear that the ignition must take place when the piston is in the "upper" range, that is, the mixture to be ignited, whatever it is, is compressed.

The optimum exact ignition timing is also dependent on the operating state of the internal combustion engine. Therefore, it makes sense to take into account not only the position of the piston in the cylinder but also the operating state of the internal combustion engine.

In one embodiment, an ignition device, in particular a spark plug, is provided for ignition. Although the ignition can be satisfactorily triggered by the injection of unchanged fuel, it may sometimes be helpful to provide an ignition device. Although many types of ignition devices, such as ignition lasers and the like are conceivable, as a rule, a spark plug is suitable.

In one embodiment, the conversion of fuel into the adjusted fuel is such that the adjusted fuel has desired properties depending on the operating condition of the internal combustion engine. For example, at high power of the internal combustion engine in which more fuel is to be burned in a single ignition to provide a corresponding energy, the fuel can be converted accordingly, that even with a fuel-rich charge gas by the compression no auto-ignition.

It should be mentioned at this point, however, that the converted fuel can also have the same properties in all operating states. So it makes sense in any case, the internal combustion engine to operate so that the mixture of adapted fuel and combustion air by the compression does not ignite itself. But it is also sufficient to fulfill this condition, so that it often does not depend exactly on how the ignitability of the fuel looks in detail. However, this should not be said that a conversion of the fuel into matched fuel that is dependent on the operating state of the internal combustion engine would be completely superfluous.

The invention also relates to a control unit designed to control an internal combustion engine with the above-described method. As already explained above, in many cases the unchanged internal combustion engine can be used. Accordingly, only minor modifications to the control unit are usually required. As a rule, a reprogramming is sufficient. Of course, a device for controlling the unit for converting the fuel into adapted fuel is also required.

In one embodiment, the control unit comprises a first module and a second module, wherein the first module is a known control unit for a known internal combustion engine and the second module is used to form the control unit for carrying out the above-described method. This modular design is particularly useful in retrofitting, such as in the above-described retrofitting of a motor vehicle with diesel engine. The first module can be the already existing control unit for the diesel engine, which merely has to be reprogrammed. The second module has the task to control the unit to convert a part of the fuel into adapted fuel. It makes sense to pass certain parameters such as power and speed of the internal combustion engine from the first module to the second module. Since these data are present anyway in the first module, this poses no problem.

• - einer Umwandlungseinheit um einen Teil des Brennstoffs in Brennstoff mit niedrigerer Zündwilligkeit umzuwandeln,
• - einer Einrichtung zur Zufuhr von angepasstem Brennstoff,
• - einer Einrichtung zur Zufuhr von Verbrennungsluft zum Zylinder, wobei die Einrichtung zur Zufuhr von angepasstem Brennstoff und zur Zufuhr von Verbrennungsluft zusammengefasst sein können;

ausgebildet das oben geschilderte Verfahren durchzuführen.The invention also relates to an internal combustion engine, in particular a diesel engine, with a device for supplying fuel to a cylinder,

• a conversion unit to convert part of the fuel into fuel with a lower level of ignition,
• a device for the supply of adjusted fuel,
• a means for supplying combustion air to the cylinder, wherein the means for supplying adapted fuel and for supplying combustion air may be combined;

trained to carry out the above-described method.

The internal combustion engine will not be described in more detail here, since this has already been done by the description of the method and the control unit.

In a particular embodiment, after the conversion, the converted fuel undergoes re-liquefaction, ie, the gaseous constituents, as described above mixed with the combustion air. The reliquefied fuel residue can either be mixed with the unchanged fuel or collected separately. In both cases, the reliquefied fuel residue is injected into the cylinder. In both cases, both the gaseous portion of the altered fuel and the reliquefied fuel residue have a lower ignitability than the unaltered fuel. The reliquefaction takes place via an adapted cooling unit.

list of figures

• 1 eine Darstellung eines Zylinders beim Ansaugen von Ladeluft mit einer Zufuhr von unverändertem und angepassten Brennstoff, Verbrennungsluft und einer Umwandlungseinheit für Brennstoff
• 2 den Zylinder bei der Kompression des Ladegases im Zylinder
• 3 den Zylinder nach der Zündung
• 4 den Zylinder bei der Abfuhr von Abgas

Based on figures further details will be explained. Show

• 1 a representation of a cylinder during the intake of charge air with a supply of unaltered and adjusted fuel, combustion air and a conversion unit for fuel
• 2 the cylinder during the compression of the charging gas in the cylinder
• 3 the cylinder after ignition
• 4 the cylinder in the removal of exhaust gas

1 shows a cylinder 1 , As fuel diesel is used, which through a fuel line 2 is funded by a tank, not shown. Most of the fuel goes through the pipe 3 to a conversion unit 4 guided. To the conversion unit 4 also gets air from the intake pipe 5 through an air branch line 6 guided. In the conversion unit 4 the diesel is being used by the air branch line 6 supplied air oxidized and converted. This will be a customized fuel 7 produced with lower ignitability than diesel, which is mixed with the air, so that charging gas 8th arises.

In the in 1 illustrated operating phase of the cylinder 1 a piston moves 9 downward. An outlet valve located at the top right 10 is closed while an upper left inlet valve 11 is open. This will be charging gas 8th So a homogeneous combustible mixture of adapted fuel 7 and combustion air 5 , in the cylinder 1 sucked.

At the in 4 The conversion unit described can be a device for the catalytic conversion of fuel, as described in the aforementioned WO 2017/085301 A1 is described.

The following 2 . 3 and 4 are to 1 largely identical, so that only the respective differences are described.

2 it shows 1 subsequent operating phase in which the piston 9 moved upwards. outlet valve 10 as well as inlet valve 11 are closed. This will be the charging gas 8th compressed. Due to the conversion in the conversion unit 4 achieved low ignitability by the compression no auto-ignition.

When the piston 9 arrived above, is through the fuel line 2 Diesel to an injector 12 guided and in the cylinder 1 injected. This causes the ignition.

As in 3 can be seen by the ignition and concomitant expansion of the piston 9 pressed down and thus power is transmitted to a crankshaft, not shown. It is understood that exhaust valve 10 as well as inlet valve 11 remain closed during this time.

4 finally shows the - after the ignition-related movement down - again moving piston 9 , with the exhaust valve open 10 and closed inlet valve 11 , Thus, the exhaust gas produced during ignition is via the exhaust pipe 13 dissipated. With suitable operation, this exhaust gas contains significantly fewer pollutants than the exhaust gas of a conventional diesel engine.

The in the 1 to 4 The section shown within the dashed area is constructed as in a conventional diesel engine. This makes it clear that a conventional diesel engine can be retrofitted with manageable effort.

LIST OF REFERENCE NUMBERS

1

cylinder

2

fuel supply

3

Fuel supply to the conversion unit

4

conversion unit

5

air supply

6

Air supply to the conversion unit

7

adapted fuel

8th

charged gas

9

piston

10

outlet valve

11

intake valve

12

injection

13

exhaust pipe

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010012945 A1 [0004]
• DE 3442628 A1 [0005, 0014]
• WO 2017/085301 A1 [0006, 0045]
• US 2005/0011486 A1 [0007, 0015]
• WO 2004/036015 A1 [0008, 0028]

Claims (12)

Method for operating an internal combustion engine with the following steps - Providing a fuel (2) Conversion of a portion of the fuel into a matched fuel (7) during operation of the internal combustion engine, wherein the adjusted fuel (7) has a lower ignitability than the unmodified fuel (2) - Supply of the adjusted fuel (7) to a cylinder (1) of the internal combustion engine - Supply of unchanged fuel (2) to the cylinder (1) of the internal combustion engine, in particular for triggering the ignition, wherein the supply of unaltered fuel (7) to the cylinder during the compression of the adjusted fuel in the cylinder, - Driving a piston (9) of the internal combustion engine by the ignition. Method according to Claim 1 , characterized in that the choice of the ratio between unchanged fuel (2) and adapted fuel (7) depends on the operating state of the internal combustion engine. Method according to one of the preceding claims, characterized in that the method is operated such that a minimization of pollutant emissions, in particular the emission of fine dust and / or nitrogen oxides, and / or the fuel consumption is achieved. Method according to one of the preceding claims, characterized in that the adapted fuel (7) with the intended combustion air (5) to a charging gas (8) is mixed and by supplying the charging gas (8) to the cylinder (1) of the internal combustion engine the supply of the adjusted fuel (7) takes place. Method according to one of the preceding claims, characterized in that the time of supply of the unchanged fuel (2) relative to the position of the piston (9) in the cylinder (1) is selected depending on the operating state of the internal combustion engine. Method according to one of the preceding claims, characterized in that for ignition an ignition device, in particular a spark plug is present. Method according to one of the preceding claims, characterized in that the conversion of fuel (2) into the adapted fuel (7) takes place such that the adapted fuel has desired properties depending on the operating state of the internal combustion engine. Method for operating an internal combustion engine with the following steps - Providing a fuel (2) Converting a portion of the fuel into a first adjusted fuel during operation of the internal combustion engine, wherein the first adjusted fuel (7) has a lower ignitability than the unmodified fuel (2) Converting a portion of the fuel into a second adjusted fuel with higher ignitability (7) than the first matched fuel during operation of the internal combustion engine, the second adjusted fuel (7) having a lower ignitability than the unmodified fuel (2), - Supply of the first matched fuel (7) with less ignition to a cylinder (1) of the internal combustion engine Supplying the second adjusted fuel (7) with higher ignition capability to the cylinder (1) of the internal combustion engine, in particular for triggering the ignition, the supply of the second adjusted fuel (7) to the cylinder occurring during the compression of the first adjusted fuel in the cylinder, - Driving a piston (9) of the internal combustion engine by the ignition. Control unit designed for controlling an internal combustion engine with a method according to one of the preceding claims. Control unit according to the preceding claim, characterized in that the control unit comprises a first module and a second module, wherein the first module is a known control unit for a known internal combustion engine and the second module is used by the control unit for carrying out the method according to any one of Claims 1 to 7 train. An internal combustion engine, in particular a diesel engine, with a device for supplying fuel (2) to a cylinder, a conversion unit (4) for converting a part of the fuel into fuel (7) with a lower ignition capability, - a device for supplying adapted fuel (7 , 8), - a device for supplying combustion air (5, 8) to the cylinder (1), wherein the means for supplying adapted fuel and for supplying combustion air may be combined; trained a method according to one of Claims 1 to 9 perform. Internal combustion engine according to Claim 10 , with a device for spark ignition of the mixture consisting of adapted fuel and / or unchanged fuel and combustion air.

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