DE102009046120A1 - Method for humidifying intake air of combustion engine, particularly diesel engine, involves determining humidity of intake air, where liquid is injected into intake air depending on humidity of intake air - Google Patents

Abstract

The method involves determining the humidity of the intake air, where a liquid is injected into the intake air depending on the humidity of the intake air. The liquid is used as water. A part of the exhaust gas of the combustion engine is mixed to the intake air.

Description

The present invention relates to a method and apparatus for humidifying the intake air of an internal combustion engine. The invention further relates to an internal combustion engine.

Legislative emission legislation for diesel engines makes it necessary to significantly reduce nitrogen oxide emissions for diesel engines. Aftertreatment with respect to nitrogen oxides is expensive, maintenance-intensive, not always reliable and cost-intensive for the respective owner or customer. In addition, additional, complex components are required, for example, for a post-injection of fuel, carbamide (urea) or the like. Sometimes it is necessary for the machine to run in a separate operating area while the aftertreatment or regeneration processes take place.

Nitrogen oxide emissions are a direct result of the combustion process. This means that by reducing nitrogen oxide production during combustion, aftertreatment processes can be reduced and optimized. Conceivable are also compromises, for example between the fine dust emission and the nitrogen oxide emissions. For example, a higher particulate matter emissions could be accepted in favor of lower nitrogen oxide emissions.

In EP 1 076 169 A2 An apparatus for humidifying the intake air of internal combustion engines having a turbocharger will be described. The apparatus comprises humidifying means through which the inlet air and humidifying fluid flow and contact each other. The humidifying device is arranged in the flow direction of the intake air upstream of the compressor of the turbocharger.

In WO 95/23268 There is described a method and associated apparatus in which the intake air of turbocharged diesel engines is humidified. In this way, the NOx content in the exhaust gas is reduced. In this case, a moistening device is used, which is flowed through by the intake air and water, wherein the intake air is compressed before moistening by the compressor of the turbocharger.

In DE 102 04 181 C1 discloses a reciprocating internal combustion engine with at least one turbocharger and a downstream intercooler and with a device for supplying water for NOx reduction. This large quantities of water can be introduced with low construction costs and space. For this purpose, a device for injecting water in the form of finely atomised droplets into the charge air is arranged between the turbocharger and the intercooler, and a control device which controls at least the values of the pressure and the temperature of the charge air and regulates the injected water quantity so that the dew point temperature of the Water in the charge air is not undershot.

In DE 199 02 349 A1 a description is given of a water injection quantity control system for an engine with fuel and water injection, which is characterized in that the water injection quantity is regulated in dependence on the running state of the engine and the operating state of the exhaust gas recirculation system.

Against this background, it is a first object of the present invention to provide an advantageous method for humidifying the intake air of an internal combustion engine. A second object of the present invention is to provide an advantageous apparatus for humidifying the intake air of an internal combustion engine. Furthermore, a third object of the present invention is to provide an advantageous combustion engine.

The first object is achieved by a method for humidifying the intake air of an internal combustion engine according to claim 1. The second object is achieved by a device for humidifying the intake air of an internal combustion engine according to claim 10. The third object is achieved by an internal combustion engine according to claim 14. The dependent claims contain further advantages of embodiments of the invention.

The inventive method for moistening the intake air of an internal combustion engine is characterized in that the humidity of the intake air is determined and a liquid is injected into the intake air depending on the humidity of the intake air. The inventive injection of liquid into the intake air as a function of the humidity of the intake air, the nitrogen oxide emission is effectively reduced by the varying humidity of the ambient air is taken into account. Preferably, water can be used as the liquid.

Furthermore, at least a part of the exhaust gas of the internal combustion engine can be added to the intake air. In this case, the liquid can be injected into the intake air as a function of the amount and / or the humidity of the admixed exhaust gas. In this way, by taking into account the varying environmental conditions, in particular the varying humidity of the admixed exhaust gas, an effective Nitrogen oxide reduction achieved. Advantageously, at least part of the exhaust gas of the internal combustion engine can be admixed with the intake air and the liquid can be injected into the intake air after admixing the exhaust gas. In this way, the required amount of liquid can be determined depending on the characteristics of the intake air and the admixed exhaust gas.

Preferably, a maximum of 25 grams of liquid per kilogram of intake air can be injected into the intake air. In the case of exhaust gas recirculation preferably a maximum of 25 grams of liquid per kilogram of a mixture of intake air and admixed exhaust gas can be injected into the mixture of intake air and admixed exhaust gas. In particular, a maximum of 15 grams of liquid per kilogram of intake air can be injected into the intake air or a maximum of 15 grams of liquid per kilogram of the mixture of intake air and admixed exhaust gas are injected into the mixture of intake air and admixed exhaust gas. A significant effect is already achieved when a maximum of 8 grams of liquid per kilogram of intake air can be injected into the intake air or a maximum of 8 grams of liquid per kilogram of a mixture of intake air and admixed exhaust gas can be injected into the mixture of intake air and admixed exhaust gas. Limiting the amount of injected moisture in the upward direction is advantageous, since a very high liquid intake causes a comparatively low nitrogen oxide reduction (see below) 1 ).

In principle, it is advantageous if the amount of liquid to be injected is selected such that the intake air or a mixture of intake air and admixed exhaust gas after injection of the liquid has a moisture content between 13 g / kg and 25 g / kg, in particular between 15 g / kg and 20 g / kg, advantageously 16 g / kg.

The liquid may also be injected in dependence on the operating state of the internal combustion engine, in particular as a function of the running speed and / or the rotational speed and / or the torque. The internal combustion engine can be designed, for example, as a diesel engine.

The inventive device for humidifying intake air of an internal combustion engine comprises a nozzle for injecting a liquid into the intake air. The apparatus further comprises a sensor for determining the humidity of the intake air. With the aid of the device according to the invention, the method according to the invention can be carried out in particular.

The device according to the invention can also comprise a device for controlling the amount of liquid to be injected as a function of the humidity of the intake air. In addition, the internal combustion engine may comprise an intake air supply line and an exhaust gas recirculation supply line. In this case, the exhaust gas recirculation feed line can lead into the intake air supply line. The nozzle for injecting the liquid can be arranged downstream of the exhaust gas recirculation feed line with respect to the flow direction of the intake air. In this way, the liquid can be injected into a mixture of intake air and recirculated exhaust gas.

In addition, the device according to the invention may comprise an exhaust gas recirculation device and a device for controlling the amount of liquid to be injected in dependence on the amount of admixed exhaust gas and / or in dependence on the moisture of the admixed exhaust gas. Furthermore, the device according to the invention may comprise a device for controlling the amount of liquid to be injected as a function of the operating state of the internal combustion engine. In particular, it may comprise a device for controlling the amount of liquid to be injected as a function of the operating speed or the rotational speed and / or the torque of the internal combustion engine. In principle, the said device for controlling the quantity of liquid to be injected can be a device with the aid of which a control of the quantity of liquid to be injected depends on both the amount of admixed exhaust gas and / or the moisture of the admixed exhaust gas and the humidity of the intake air can be done depending on the operating state of the internal combustion engine. In this way, it is possible to achieve a constant humidity of the intake air or of the mixture of intake air and admixed exhaust gas and to influence and reduce the nitrogen oxide emission in a targeted manner.

The internal combustion engine according to the invention comprises a previously described device for humidifying intake air. The internal combustion engine according to the invention can be designed, for example, as a diesel engine. It basically has the same advantages as the previously described device for humidifying the intake air according to the invention.

Both the method according to the invention and the apparatus according to the invention and the internal combustion engine according to the invention render exhaust gas aftertreatment largely superfluous with respect to the nitrogen oxide emissions or reduce this at least considerably.

Further features, features and advantages of the present invention will be described in more detail below with reference to an embodiment with reference to the accompanying figures. The features described are advantageous both individually and in combination with each other.

1 shows an example of the dependence of nitrogen oxide emissions on the humidity of the intake air.

2 shows schematically the operation of an internal combustion engine according to the invention.

3 shows schematically the operation of a device for controlling the amount of liquid to be injected.

In the following, an embodiment of the present invention will be described with reference to FIGS 1 to 3 explained in more detail. The 1 shows the dependence of nitrogen oxide emissions on the humidity of the intake air. In the in the 1 The diagram shows the humidity of the intake air used in grams per kilogram (g / kg) on the x-axis. On the y-axis, the amount of nitrogen oxide (NO _x ) discharged is plotted in grams per hour (g / h). The specified trace 1 were measured at a certain speed and a certain load of the internal combustion engine used, in particular the engine used.

From the trace 1 shows that the nitrogen oxide output of just under 100 g / h at a moisture content of 8 g / kg can be reduced by doubling the moisture to 16 g / kg to less than 80 g / h. This corresponds to a reduction of nitrogen oxide emissions by about 20%. Nitric oxide lowering is indicated by an arrow 2 characterized.

Under test conditions, the humidity of the intake air during operation of an engine is typically kept constant at about 8 g / kg. From the 1 follows that even a doubling of the moisture to 16 g / kg causes a significant reduction in nitrogen oxide emissions. A further increase in humidity reduces nitrogen oxide emissions to a much lesser extent. In particular, the nitrogen oxide output can not be reduced proportionally with an increase in the intake air humidity. For example, at a moisture level of 40 g / kg, nitrogen oxide emissions are still around 55 g / kg. This means a reduction in nitrogen oxide emissions by about 45%, based on a nitrogen oxide output of just under 100 g / h at a humidity of 8 g / kg, with a five-fold increase in the humidity of the intake air.

The 2 shows schematically the operation of an internal combustion engine according to the invention. The internal combustion engine comprises a motor 12 with an air intake 13 and an exhaust outlet 14 , The through the air intake 13 the engine 12 supplied air is first in the form of ambient air 3 through an intake air supply line 8th an air filter 4 fed. With the help of an air mass meter 10 the mass flow of the sucked ambient air is determined. Furthermore, with the help of a moisture sensor 29 determines the humidity of the intake ambient air.

The sucked ambient air is now using a compressor 5 compressed, then with the help of a cooler 6 cooled and over a valve 7 to the air intake 13 of the motor 12 directed. The flow direction of the ambient air through the air inlet 13 leading intake air supply 8th is by arrows 9 characterized.

The internal combustion engine according to the invention further comprises an exhaust gas recirculation system 19 , The exhaust gas recirculation system 19 includes an exhaust gas recirculation supply line 20 that the exhaust outlet 14 of the motor 12 with the air intake 13 of the motor 12 combines. In this case, the exhaust gas recirculation feed line opens 20 in the flow direction behind the valve 7 into the intake air supply line 8th one. The exhaust gas recirculation supply line 20 includes a valve 21 and a cooler 22 , Part of the exhaust outlet 14 of the motor 12 leaving exhaust gas is through the exhaust gas recirculation feed line 20 over the valve 21 and the radiator 22 in the flow direction 18 into the intake air supply line 8th initiated. In that area 23 in which the exhaust gas recirculation feed line 20 into the intake air supply line 8th opens, mix the intake air and the recirculated exhaust gas.

In the flow direction downstream of the junction of the exhaust gas recirculation feed line 20 into the intake air supply line 8th is a fluid nozzle 11 for injecting liquid, for example water, arranged in the mixture of intake air and recirculated exhaust gas. The humidified mixture of air and exhaust gas then flows in the direction of flow 16 the air intake 13 of the motor 12 , Then the engine 12 through the exhaust outlet 14 leaving exhaust gas flows for the most part in the flow direction 17 to a turbine 15 and drives them. Part of the exhaust gas, as already described above, through the exhaust gas recirculation feed line 20 the combustion process of the engine 12 redirected.

The 3 shows schematically the operation of a to the liquid nozzle 11 connected device for controlling the amount of liquid einzudüsenden. The device for controlling the amount of liquid to be injected comprises a device 26 to determine the setpoint of humidity. In the device for determining the desired value of the moisture 26 be the respective speed 24 and the respective torque 25 of the motor 12 fed. Subsequently, these values become the setpoint of the humidity 27 determined.

The humidity of the intake ambient air 3 is done with the help of the humidity sensor 29 determined. Furthermore, the amount of the exhaust gas recirculation system 19 recirculated exhaust gas 28 determined. From the recirculated exhaust gas amount and the humidity of the intake air is using a PT1-member 31 the actual value of the moisture 30 determined. Subsequently, the difference from the setpoint of humidity 27 and the actual value of the moisture 30 with the help of a differential element 32 educated. The difference thus determined 33 off setpoint 27 and actual value 30 The moisture is then removed by means of a PT1 element 34 filtered.

From the filtered difference 35 off setpoint 27 and actual value 30 The moisture is due to product formation 36 with the help of the air mass meter 10 determined air mass 37 the setpoint 38 determined for the amount of liquid to be supplied. From the determined setpoint for the amount of liquid to be supplied 38 is in a final step, taking into account the saturation 39 the actual amount of liquid to be injected 40 determined. The actual amount of liquid to be injected is then using the liquid nozzle 11 injected into the mixture of intake air and recirculated exhaust gas.

For example, a maximum of 25, advantageously a maximum of 15, preferably a maximum of 8, grams of liquid per kilogram of the mixture of intake air and admixed exhaust gas can be injected into the mixture of intake air and admixed exhaust gas. In principle, the amount of injected moisture should be limited to the top, since a very high fluid intake causes a comparatively low nitrogen oxide reduction (see 1 ). In particular, the amount of liquid to be injected, which may be, for example, water, be chosen so that the mixture of intake air and admixed exhaust gas after injection of the liquid moisture between 13 g / kg and 25 g / kg, in particular between 15 g / kg and 20 g / kg, preferably 16 g / kg.

Overall, with the help of the present invention, the fluctuating humidity of the ambient air can be effectively balanced. At the same time, by additionally humidifying the intake air, taking into account the operating state of the internal combustion engine and the exhaust gas recirculation, for example of the engine, the nitrogen oxide output is lowered to a constantly low level. The present invention has the particular advantage that a nitrogen oxide reduction of more than 10% can be achieved with minimal effort.

LIST OF REFERENCE NUMBERS

1

Nitrogen oxide emissions depending on the humidity of the intake air

2

Difference of about 20%

3

ambient air

4

air filter

5

compressor

6

cooler

7

Valve

8th

Ansaugluftzuleitung

9

flow direction

10

Air flow sensor

11

fluid nozzle

12

engine

13

air intake

14

exhaust outlet

15

turbine

16

Flow direction of the mixture of air and exhaust gas

17

Flow direction of the exhaust gas

18

Flow direction of the exhaust gas

19

Exhaust gas recirculation system

20

Exhaust gas recirculation supply line

21

Valve

22

cooler

23

Mixture between air and exhaust gas

24

speed

25

torque

26

Device for determining the desired value of moisture

27

Setpoint of humidity

28

Exhaust gas recirculation rate

29

humidity sensor

30

Actual value of moisture

31

PT1

32

differential element

33

Difference between setpoint and actual value of humidity

34

PT1

35

filtered difference between setpoint and actual value of humidity

36

product formation

37

air mass

38

Setpoint for the amount of liquid to be supplied

39

Consideration of saturation

40

amount of liquid to be injected

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

• EP 1076169 A2 [0004]
• WO 95/23268 [0005]
• DE 10204181 C1 [0006]
• DE 19902349 A1 [0007]

Claims (15)

Method for humidifying the intake air of an internal combustion engine ( 12 ), characterized in that - the humidity of the intake air ( 3 ) and - a liquid as a function of the humidity of the intake air ( 3 ) is injected into the intake air. A method according to claim 1, characterized in that water is used as the liquid. A method according to claim 1 or 2, characterized in that at least a part of the exhaust gas of the internal combustion engine ( 12 ) the intake air ( 3 ) is added and the liquid in dependence on the amount and / or the humidity of the admixed exhaust gas in the intake air ( 3 ) is injected. Method according to one of claims 1 to 3, characterized in that at least a part of the exhaust gas of the internal combustion engine ( 12 ) is added to the intake air and the liquid is injected after admixing the exhaust gas in the intake air. Method according to one of claims 1 to 4, characterized in that a maximum of 25 g of liquid per kilogram of intake air ( 3 ) into the intake air ( 3 ) or a maximum of 25 g of fluid per kilogram of a mixture of intake air ( 3 ) and admixed exhaust gas into the mixture of intake air ( 3 ) and admixed exhaust gas are injected. A method according to claim 5, characterized in that a maximum of 15 g of liquid per kilogram of intake air ( 3 ) into the intake air ( 3 ) or a maximum of 15 g of fluid per kilogram of a mixture of intake air ( 3 ) and admixed exhaust gas into the mixture of intake air ( 3 ) and admixed exhaust gas are injected. A method according to claim 6, characterized in that a maximum of 8 g of liquid per kilogram of intake air ( 3 ) into the intake air ( 3 ) or a maximum of 8 g of fluid per kilogram of a mixture of intake air ( 3 ) and admixed exhaust gas into the mixture of intake air ( 3 ) and admixed exhaust gas are injected. Method according to one of claims 1 to 7, characterized in that the amount of liquid to be injected is chosen so that the intake air ( 3 ) or a mixture of intake air ( 3 ) and admixed exhaust gas after injection of the liquid has a moisture content between 13 g / kg and 25 g / kg. Method according to one of claims 1 to 8, characterized in that the liquid in dependence on the operating condition of the internal combustion engine ( 12 ) is injected. Device for humidifying intake air of an internal combustion engine ( 12 ), which has a nozzle ( 11 ) for injecting a liquid into the intake air ( 3 ), characterized in that the device comprises a sensor ( 29 ) for determining the humidity of the intake air ( 3 ). Apparatus according to claim 10, characterized in that it comprises means for controlling the amount of liquid to be injected as a function of the humidity of the intake air ( 3 ). Device according to claim 10 or 11, characterized in that the internal combustion engine ( 12 ) an intake air supply line ( 8th ) and an exhaust gas recirculation supply line ( 20 ), wherein the exhaust gas recirculation feed line ( 20 ) into the intake air supply line ( 8th ) and the nozzle ( 11 ) for injecting a liquid with respect to the flow direction ( 9 ) the intake air ( 3 ) downstream of the exhaust gas recirculation feed line ( 20 ) is arranged. Device according to one of claims 10 to 12, characterized in that it comprises an exhaust gas recirculation device ( 19 ) and means for controlling the amount of liquid to be injected in dependence on the amount of admixed exhaust gas and / or the humidity of the admixed exhaust gas and / or in dependence on the operating state of the internal combustion engine ( 12 ). Combustion engine ( 12 ), characterized in that it comprises a device according to any one of claims 10 to 13. Combustion engine ( 12 ) according to claim 14, characterized in that the combustion engine ( 12 ) is designed as a diesel engine.

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