MONITORING AN ENGINE BY MEANS OF CYLINDER PRESSURE SENSORS, PREFERABLY IN LEAN GAS ENGINES WITH A FLUSHED PRECHAMBER

Abstract

A method for operating an internal combustion engine, in particular a gas engine, preferably a lean gas engine, which has at least one cylinder, in order to improve the combustion process, a prechamber is provided for igniting a mixture in a main chamber. A pressure curve is detected by a pressure sensor in the main chamber dependent on a crank angle, and the quantity of supplied fuel is controlled or regulated for each individual cylinder using a fuel metering device and the pressure sensor dependent on a desired output and/or a desired torque and/or a desired rotational speed of the internal combustion engine.

Claims

1-13. (canceled)

14. A method for operating an internal combustion engine which has at least one cylinder, comprising the steps of: providing a prechamber for igniting a mixture in a main chamber; determining a pressure gradient by a pressure sensor in the main chamber in a manner that is dependent on a crank angle; and controlling or regulating a supplied quantity of fuel into the prechamber and/or into the main chamber for each individual cylinder with aid of the pressure sensor in a manner dependent on a desired power output and/or a desired torque and/or a desired rotational speed of the internal combustion engine.

15. The method according to claim 14, including flushing the prechamber during every cycle, and introducing a fuel for ignition into the prechamber via a prechamber valve.

16. The method according to claim 15, wherein the fuel is gas.

17. The method according to claim 14, wherein the pressure sensor is an indicator quartz, a sensor with strain gage technology, or an optical sensor.

18. The method according to claim 14, including evaluating a pressure gradient for appearance of a gradient peak in a rising branch of the pressure gradient.

19. The method according to claim 18, wherein the pressure gradient is of heat release rate or combustion profile.

20. The method according to claim 14, including determining a temperature in an unburned region of a two zone model to define a gap from a knock threshold and/or a prediction of knocking behavior.

21. The method according to claim 14, wherein adaptive pilot control and/or regulation of an air ratio takes place.

22. The method according to claim 14, wherein adaptive pilot control and/or regulation of an ignition time takes place.

23. The method according to claim 14, wherein adaptive pilot control and/or regulation of an introduced volume of the prechamber gas valve takes place.

24. The method according to claim 14, wherein the pressure sensor is a piezoresistive sensor, the method including integrating a pressure signal from the sensor to detect a quartz defect.

25. The method according to claim 14, including dividing the combustion chamber into two zones for a pressure gradient analysis, namely into an unburned and a burned zone, and using temperature in the unburned zone to derive a knock interval for a current cycle at an operating point.

26. The method according to claim 14, including equalizing a plurality of cylinders by setting an air ratio via a prechamber gas valve in the prechamber.

27. The method according to claim 14, including carrying out an automatic check of the engine and/or the pressure sensor by comparing a cumulative heat release rate with a predetermined value.

28. The method according to claim 25, including determining an indicated mean pressure from the pressure gradient, and calculating an effective power output of the internal combustion engine with consideration of a predetermined frictional power, and making these available to a controller for executing protective measures.

29. The method according to claim 14, wherein the engine is a gas engine.

30. The method according to claim 29, wherein the engine is a lean gas engine.

Description

[0025] One preferred embodiment of the invention will be explained by way of example using a drawing, in which, in detail:

[0026] FIG. 1 shows a diagrammatic vertical section through a cylinder,

[0027] FIG. 2 shows a diagrammatic view of the cylinder head according to the viewing direction II-II in FIG. 1,

[0028] FIG. 3 shows a standardized heat release rate of a cylinder pressure indication system,

[0029] FIG. 4 shows the profile of the integrated heat release rate, and

[0030] FIG. 5 shows the standardized profile of a temperature measurement in the unburned zone, plotted against the crank angle.

[0031] FIG. 1 shows by way of example a vertical section through a cylinder of an internal combustion engine. FIG. 2 shows a diagrammatic view of the cylinder head according to the viewing direction II-II in FIG. 1.

[0032] The air/gas mixture 3 of a gas engine is burned in a main chamber 4. The cylinder 1 forms the outer lower boundary of the main chamber 4, the side walls are formed by the cylinder liner 23 which encloses the cylinder, and the cylinder head 24 (FIG. 2) closes the main chamber at the top. A mixture of air and gas flows through the inlet pipes 25 in a manner controlled by inlet valves 27 into said combustion chamber of the main chamber 4. After the ignition and combustion, the exhaust gas then leaves the combustion chamber 4 through the outlet pipes 26 (FIG. 2) in a manner which is controlled by way of the outlet valves 28.

[0033] The ignition device 29 (shown in FIG. 1) with its prechamber 5 serves to ignite the mixture, into which prechamber 5 an injection volume is as a rule injected into the prechamber 5 for ignition by way of an injection valve 30 as a prechamber valve 10 for ignition purposes. The introduction of the gas into the prechamber preferably takes place at a gas pressure level of up to 10 bar at the gas exchange bottom dead center. A high pressure gas injection in the compression stroke is also possible at pressures of up to 300 bar.

[0034] As soon as the gas mixture has ignited in the prechamber 5, ignition jets 31 leave the ignition openings 32 of the prechamber 5. The ignition jets then ignite the mixture 3 in the main chamber 4, which mixture 3 is situated and compressed in said main chamber 4.

[0035] In addition, a pressure sensor 7 for monitoring the main chamber 4 is arranged in the cylinder head, which pressure sensor 7 measures the pressure gradient 6 in a manner which is dependent on the crank angle 8. An indicator quartz 11 is used as pressure sensor 7, which indicator quartz 11 measures the pressure gradient 6 (shown in FIG. 3) in a manner which is dependent on the crank angle KW, and is fed as a signal for evaluation to a controller (not shown).

[0036] FIG. 3 shows a standardized heat release rate of this type or else heat release profile 6 which is obtained from the pressure gradient by means of heat release rate analysis. A profile peak 12 can be clearly seen in the rising branch 13 of the heat release rate 6, which profile peak 12 can be attributed to the ignition in the prechamber. Conclusions can be made from the position of the profile peak 12 with respect to the pressure maximum 33 about the dynamics of the combustion operation in the main chamber 4. The heat release rate 6 corresponds to the amount of heat dQ which is produced by way of the combustion.

[0037] The graph which is shown in FIG. 4 represents the integral of the heat release rate shown in FIG. 3 plotted against the crank angle. It therefore corresponds to the overall output or produced amount of heat of one individual ignition. The combustion sequence is concluded as soon as the cumulative combustion profile 34 ends horizontally. If the cumulative combustion profile 34 does not reach a horizontal discontinuation at the end, but rather the profiles 35 which are shown using interrupted lines, it is to be concluded herefrom that the pressure sensor 7 and/or the indicator quartz 11 are/is defective and/or there is another fault in the engine. These artefacts 35 are illustrated in FIG. 4 using interrupted lines.

[0038] FIG. 5 shows the temperature profile in the unburned zone from the two zone model. The temperature of the unburned zone Tu. The temperature of the knock threshold is indicated by a horizontal line 36. The maximum of the measured temperature 37 is at a gap 14 from said knock threshold 36. The controller can make a conclusion about the inherent reserves of the combustion process therefrom and/or avoid knocking states.

[0039] As soon as a load increase requirement is reported to the engine or to the controller by the operator or by the generator, the control unit determines the knock gap as a temperature difference, or takes a value from a preceding determination which is determined via deliberate approaching of the knock limit, or a value which corresponds to a methane number which is predetermined by the controller. The controller then causes the enrichment of the mixture up to the knock limit. This corresponds to the maximum permissible temperature in the unburned zone. In this way, the most satisfactory response behavior of the engine to load increase requirements can be achieved.