DE102018200034A1 - Water injection device of an internal combustion engine - Google Patents

Abstract

The invention relates to a water injection device (1) and an internal combustion engine (100) comprising the water injection device (1). The water injection device (1) comprises a water tank (90) for storing water, at least one first water injector (2) and optionally a second water injector (3) for injecting the water, a control device (4) which is set up, the first water injector ( 2) and the second water injector (3), wherein the first water injector (2) is arranged to inject water in the flow direction (a) of combustion air in a suction pipe (21) downstream of a combustion air compressor (5) into the combustion air, and wherein the second water injector (3) is arranged to inject water directly into a combustion chamber (20) or into the suction pipe (21) at a position in the flow direction (A) downstream of the first water injector (2).

Description

State of the art

The present invention relates to a water injection device of an internal combustion engine and such an internal combustion engine.

Due to increasing demands on reduced carbon dioxide emissions, internal combustion engines are increasingly being optimized with regard to fuel consumption. However, known internal combustion engines can not be operated optimally in terms of consumption at operating points with high load, since the operation is limited by knock tendency and high exhaust gas temperatures. A possible measure to reduce the tendency to knock and to lower the exhaust gas temperatures is the injection of water. There are usually separate water injection systems available to allow the water injection. For example, from the WO 2014/080266 A1 a water injection system for an internal combustion engine with exhaust gas recirculation, in which the water is injected into the mass flow of the exhaust gas recirculation.

A problem with known water injection systems which inject water exclusively into a suction pipe or directly into a combustion chamber is the large amount of water required to achieve the desired effects. Due to incomplete evaporation of water after the injection, for example, adjacent components are wetted by water. Although the wetted components are cooled, but the cooling effect is reduced to the combustion air. Thus, very high amounts of water must be injected in order to evaporate enough water and to be able to use the positive effects of water injection.

Disclosure of the invention

The water injection device of an internal combustion engine according to the invention with the features of claim 1 has the advantage that an optimized evaporation of injected water in combustion air water is achieved and the required amount of water is reduced. This is achieved by a water injection device of an internal combustion engine comprising a water tank for storing water, at least a first water injector and a second water injector for injecting the water, and a control device configured to control the first water injector and the second water injector. The first water injector is configured to inject water downstream of a combustion air compressor into the combustion air. Considered is a flow direction of the combustion air in a suction pipe. In particular, the injection may occur near or immediately downstream of the combustion air compressor, in a region where the combustion air has a high temperature due to the compression in the combustion air compressor. The combustion air compressor may be, for example, a compressor of a turbocharger. The second water injector is configured to inject water directly into a combustion chamber or into the suction pipe at a position in the flow direction of the combustion air downstream of the first water injector. In particular, the injection can take place by means of the second water injector in the suction pipe immediately upstream of the combustion chamber. The injection of the water with the first water injector downstream of the combustion air compressor has a particularly advantageous effect on maximizing the mass fraction of water in the combustion air. After leaving the combustion air compressor, the combustion air has a high temperature, which may be above 80 ° C., for example. Thus, in comparison to the injection at a farther downstream position, in particular immediately upstream of the combustion chamber, where the combustion air has low temperatures, a much faster evaporation of the injected water and also an increased capacity of water in the combustion air is possible. The amount of water to be injected, in order to achieve a certain cooling of the combustion air by evaporation of the water, is thus considerably reduced. If necessary, additional water is injected by means of the second water injector for a further increase in the amount of water in the combustion air.

The dependent claims show preferred developments of the invention.

Particularly preferably, the water injection device further comprises at least one sensor for determining a moisture content and / or a temperature of combustion air in the intake manifold after the injection of the water by means of the first water injector. In this case, the control device is set up to control the first water injector such that the combustion air has a moisture content of 100% relative humidity after the injection of the water. By determining the moisture content of the combustion air and a corresponding control of the water injector by means of the control device, a maximum possible amount of water can be injected and evaporated into the combustion air in a particularly efficient manner. For example, it is also possible to provide additional sensors. Thus, temperature sensors can be used to measure the temperatures of the water, the combustion air before the injection of water, the combustion air upstream of the combustion chamber and / or the environment. By means of Control device can be calculated from these temperatures, for example, the moisture content of the combustion air and the required amount of water to be injected for a relative humidity of 100% after injection.

Furthermore, it is particularly advantageous if the first water injector is set up to inject water counter to the flow direction of the combustion air. By relative to an injection in the direction of flow greater relative movement of the injected water and the combustion air to each other a quick and complete evaporation of the water is favored.

Preferably, the control device is set up to control the first water injector such that the injection of the water takes place continuously. In this case, a particularly simple control of the water injector is possible. The amount of water to be injected can be controlled, for example, by a variation of a water pressure upstream of the water injector.

Preferably, the control device is set up to control the first water injector such that the injection of the water takes place discontinuously. In this case, for example, several injections can be distributed evenly. This makes it possible to further reduce the amount of water to be injected.

Furthermore, the invention relates to an internal combustion engine, in particular of a motor vehicle, with a combustion air compressor and a water injection device. In this case, the first water injector may be configured to inject water downstream of the combustion air compressor, for example a compressor of a turbocharger of the internal combustion engine, into the combustion air. The second water injector may be configured to inject water at a position downstream of the first water injector into a suction pipe, or directly into the combustion chamber.

It is considered particularly advantageous if the internal combustion engine further comprises a charge air cooler, wherein the first water injector is arranged to inject water between the combustion air compressor and the intercooler. The injection of water between the combustion air compressor and intercooler has a particularly favorable effect on an efficient cooling of the combustion air through the water evaporating during the injection. In addition, by injecting the water into the hot combustion air downstream of the combustion air compressor and upstream of the charge air cooler, it is particularly advantageously possible to inject and evaporate just as much water that a relative humidity of 100% is present after cooling in the charge air cooler.

Particularly preferably, the first water injector is arranged to inject water into a first intake manifold between the combustion air compressor and the intercooler. The second water injector is arranged to inject water into a second intake manifold between the intercooler and a combustion chamber or directly into the combustion chamber. The operation of the internal combustion engine is particularly efficient due to two effects. On the one hand, a better cooling of the combustion air before entry into the combustion chamber can be achieved by the optimized evaporation of the water by the injection with the first water injector. Furthermore, by a high relative humidity of the combustion air, the total mass fraction of water in the combustion air and thereby the charge mass in the combustion chamber can be increased. This increases the efficiency of the internal combustion engine and the temperature load of the components at high loads decreases.

Preferably, the internal combustion engine further comprises a return line. The return line connects the intercooler with the water tank, for the return of condensed water in the intercooler. As a result, excess water, which can no longer be absorbed by the water-saturated combustion air, can be reused. Thereby, the efficiency of the water injection device and thus the internal combustion engine can be further increased.

list of figures

• 1 eine vereinfachte schematische Ansicht einer Brennkraftmaschine mit einer Wassereinspritzvorrichtung gemäß einem Ausführungsbeispiel der Erfindung.

In the following the invention will be described with reference to an embodiment in conjunction with the figure. In the figure, functionally identical components are each identified by the same reference numerals. Showing:

• 1 a simplified schematic view of an internal combustion engine with a water injection device according to an embodiment of the invention.

Embodiment of the invention

The 1 shows an internal combustion engine 100 with a water injection device 1 and a combustion air compressor 5 according to an embodiment.

Combustion air flows in the flow direction A from the combustion air compressor 5 , which compresses the combustion air, in a first Saugrohrstrecke 11 , In the first intake manifold 11 is in the combustion air water by means of a first water injector 2 injected. The first water injector 2 is arranged such that the injection of the water takes place counter to the flow direction A of the combustion air.

By compressing the combustion air in the combustion air compressor 5 has this in the first Saugrohrstrecke 11 a very high temperature. This effectively vaporizes the injected water. Thus, a large amount of water can be injected without the water being in a liquid state.

After the injection of the water, the combustion air flows into a charge air cooler 6 where it is cooled, and then in a second intake manifold 12 , The first and the second intake manifold 12 form a suction tube in the embodiment 21 , which injects the combustion air into a combustion chamber 20 the internal combustion engine 100 passes. In the second intake manifold 12 there is a throttle 15 to regulate the combustion chamber 20 flowing combustion air.

By means of a second water injector 3 will add more water to the second intake manifold 12 at a position downstream of the intercooler 6 and immediately upstream of the combustion chamber 20 injected. This allows the total amount of water in the combustion air in the combustion chamber 20 be further increased.

The water injection device 1 further comprises a control device 4 which is set up, the two water injectors 2 . 3 to control. In particular, the amount of water to be injected in each case by means of the control device 4 controlled.

The first water injector 2 is controlled so that the injection of the water takes place continuously.

The control device 4 is also equipped the first water injector 2 depending on measured values of sensors 7 . 8th . 9 . 10 to control. These are the in 1 shown embodiment temperature sensors. A first sensor 7 detects the temperature of the combustion air downstream of the combustion air compressor 5 and even before the injection of water. A second sensor 8th detects the temperature of the combustion air in the direction of flow A to the intercooler 6 and in front of the throttle 15 , Continue to capture a third sensor 9 the water temperature in a water tank 90 , which stores the water to be injected, and a fourth sensor 10 an ambient temperature.

By means of the control device 4 can thus be determined and controlled based on the temperatures exactly the desired amount of water to be injected. In this case, the first water injector 2 be controlled so that the combustion air at the entrance of the intercooler 6 has a relative humidity of 100%. In this case condenses due to the cooling effect of the intercooler 6 a portion of the water vapor in the combustion air within the intercooler 6 to water. The condensed water is in a return line 95 which is a valve 93 has, of the intercooler 6 to the water tank 90 recycled. A pump is not required because due to the compression of the combustion air in the combustion air compressor 5 a pressure gradient from the intercooler 6 to the water tank 90 is present.

Furthermore, it is preferably also possible for the first water injector 2 be controlled so that just as much water is injected that in the flow direction A immediately downstream of the intercooler 6 a relative humidity of the combustion air of 100% is present, with no water in the intercooler 6 condensed.

Provision of water to the two water injectors 2 . 3 done with a water pump 91 , which by means of the control device 4 is controlled. The water pump 91 is inside the water tank 90 arranged. Furthermore, in the water tank 90 a filter 92 arranged for filtering the water. By arranging these parts inside the water tank 90 results in a particularly space-saving and easy to install configuration of the water injection device 1 ,

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

• WO 2014/080266 A1 [0002]

Claims (9)

Water injection device of an internal combustion engine, comprising: a water tank (90) for storing water, at least a first water injector (2) and a second water injector (3) for injecting the water, a control device (4) which is set up to control the first water injector (2) and the second water injector (3), - wherein the first water injector (2) is adapted to inject water with respect to a flow direction (A) of combustion air in a suction pipe (21) downstream of a combustion air compressor (5) in the combustion air, and - Wherein the second water injector (3) is arranged to inject water directly into a combustion chamber (20) or in the suction pipe (21) at a position in the flow direction (A) downstream of the first water injector (2). Water injector after Claim 1 , further comprising at least one sensor (7) for determining a moisture content and / or a temperature of combustion air in the suction pipe (21) after the injection of the water by means of the first water injector (2), wherein the control device (4) is arranged, the first water injector (2) to control such that the combustion air after the injection of the water has a moisture content of 100% relative humidity. Water injection device according to one of the preceding claims, wherein the first water injector (2) is adapted to inject water preferably opposite to the flow direction (A) of the combustion air. Water injection device according to one of the preceding claims, wherein the control device (4) is arranged to control the first water injector (2) such that the injection of the water takes place continuously. Water injection device according to one of Claims 1 to 3 wherein the control device (4) is arranged to control the first water injector (2) in such a way that the injection of the water takes place discontinuously. Internal combustion engine comprising a combustion air compressor (5) and a water injection device (1) according to one of the preceding claims. Internal combustion engine after Claim 6 further comprising an intercooler (6) arranged downstream of the combustion air compressor (5) in the direction of flow (A) of the combustion air in the intake manifold (21), the first water injector (2) being arranged to supply water between the combustion air compressor (2). 5) and the charge air cooler (6) to inject into the combustion air. Internal combustion engine after Claim 7 wherein the first water injector (2) is arranged to inject water into a first draft pipe line (11) between the combustion air compressor (5) and the charge air cooler (6), and the second water injector (3) is arranged to introduce water into a second one Intake manifold (12) between the charge air cooler (6) and a combustion chamber (20) or inject directly into the combustion chamber (20). Internal combustion engine according to one of Claims 7 or 8th further comprising a return line (95), the return line (95) connecting the charge air cooler (6) to the water tank (90) for returning water condensed in the charge air cooler (6).

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