Method for operating an air-breathing engine

1. A method for operating an air-breathing engine, comprising the steps of:

injecting a mass flow of atomized liquid in the form of a liquid mist into an air intake duct of the engine;

determining, using a measuring apparatus arranged in or on the intake duct downstream of the location of the injection of the liquid, at least: the size of the liquid drops of the liquid mist, the concentration of the liquid drops of the liquid mist, or both;

inputting the measured values into a control system of the injection apparatus used; and

carrying out actions on a control of the injection apparatus used for injecting the liquid as a function of the measured values.

2. The method as claimed in claim 1 , wherein at least one measured actual value is adjusted to a desired value and/or to a desired value range by suitable control actions on the control of the liquid injection apparatus.

3. The method as claimed in claim 2 , wherein the desired value and/or the desired value range are defined so as to be variable.

4. The method as claimed in claim 1 , wherein the admission pressure of the liquid is altered as a function of the measured values, and the admission pressure is increased in the event of a negative desired value/actual value deviation in the measured drop size and/or the admission pressure is reduced in the event of a positive desired value/actual value deviation in the drop size.

5. The method as claimed in claim 1 , wherein the pressure of a gas used to atomize the liquid is altered as a function of the measured values, and the pressure of the gas is increased in the event of a negative desired value/actual value deviation in the drop size and/or reduced in the event of a positive desired value/actual value deviation in the drop size.

6. The method as claimed in claim 1 , wherein the geometry of nozzles used for the atomization is altered as a function of the measured values, with the cross section of the atomizer opening of the nozzles being reduced in size in the event of a negative desired value/actual value deviation in the drop size and increased in size in the event of a positive desired value/actual value deviation in the drop size.

7. The method as claimed in claim 6 , wherein, to adjust the atomizer opening cross section, conical inner bodies are introduced to a different distance into the atomizer opening.

8. The method as claimed in claim 1 , wherein nozzles and/or nozzle groups are selectively switched on and/or off as a function of the measured values.

9. The method as claimed in claim 8 , wherein, in the event of a control deviation in the measured drop size, nozzles and/or nozzle groups are selectively switched on and/or off, with the number of nozzles being reduced in the event of a negative desired value/actual value deviation in the drop size and/or nozzles and/or nozzle groups being selectively switched on in the event of a positive desired value/actual value deviation in the drop size.

10. The method as claimed in claim 8 , wherein, in the event of a control deviation in the measured drop size, a switching takes place between nozzles and/or nozzle groups with different atomizer properties, with a switch to nozzles for finer atomization taking place in the event of a negative desired value/actual value deviation in the drop size and/or a switch to nozzles for less fine atomization taking place in the event of a positive desired value/actual value deviation in the drop sizes.

11. The method as claimed in claim 1 , wherein the drop concentration is measured at a plurality of locations in the intake duct, and nozzles and/or nozzle groups arranged at different positions are switched on and/or off in order to achieve a predetermined desired concentration profile, which is an at least approximately even distribution of the drops over the cross section of the intake duct.

12. The method as claimed in claim 1 , wherein additives for influencing the surface tension are metered in prior to the injection as a function of the measured drop size of the liquid to be injected, and the metering takes place such that the surface tension drops in the event of a negative desired value/actual value deviation in the drop size and the metering takes place such that the surface tension rises in the event of a positive desired value/actual value deviation in the drop size.

13. The method as claimed in claim 1 , wherein the liquid injection is switched off in the event of a threshold value for the drop size being exceeded and/or in the event of an excessive deviation in a measured concentration profile over the cross section of the intake duct.

14. The method as claimed in claim 1 , wherein measured values are recorded at a plurality of measurement positions in the intake duct over the cross section of the intake duct.

15. The method as claimed in claim 1 , wherein the measured values are recorded using an integrating measurement method which delivers mean values over a certain measurement field.

16. The method as claimed in claim 15 , wherein a plurality of measured values are recorded simultaneously, and a local resolution of the measured values is reconstructed using tomographic methods.

17. The method as claimed in claim 1 , wherein an optical measurement method, which is a scattered light and/or transmitted light measurement, is used for determining, for the injected liquid mist, at least one of the drop concentration, the injected drop size, and the distribution range of the drop size.

18. The method as claimed in claim 1 , wherein an image evaluation method is used for determining, for the injected liquid mist, at least one of the drop concentration, the drop size, and the distribution range of the drop size.

19. The method as claimed in claim 1 , wherein the injected mass flow of liquid is kept constant during the action on the control.