Compression-ignition internal combustion engine

1. An internal combustion engine, comprising

a control unit;

a combustion space formed between a piston and a cylinder head; and

a fuel injection device with an injection nozzle, which has a nozzle needle and a plurality of injection bores, wherein

the injection nozzle is arranged to inject fuel into the combustion space in the form of a plurality of fuel jets as at least one of a main injection, pre-injection and post-injection,

the nozzle needle is arranged to permit fuel injection selectively through at least two separate groups of said injection bores,

the control unit is programmed to control an operating stroke of the nozzle needle as a function of at least one of a piston position and an operating point of the internal combustion engine, and

the operating stroke of the nozzle needle is controlled by the control unit to form an unstable cavitating flow in the injection bores.

2. The internal combustion engine as claimed in claim 1 , wherein

each of the at least two separate groups of bores are arranged in the rows about a circumference of the injection nozzle, and

at least one row of bores has a fuel injection cone angle which is different from a fuel injection cone angle of a different row of bores.

3. The internal combustion engine as claimed in claim 2 , wherein

a first row of bores is activated during main injection and a second row of holes is activated during at least in of pre-injection and post-injection, and

the first row fuel injection cone angle is greater than the second row fuel injection cone angle.

4. The internal combustion engine as claimed in claim 1 , wherein a fuel injection pressure is set as a function of at least one of the piston position and the operating point.

5. The internal combustion engine as claimed in claim 1 , wherein the engine is configured to produce a gas swirl movement in the combustion space.

6. The internal combustion engine as claimed in claim 5 , wherein the nozzle needle is controlled to inject fuel in one of a continuous or an intermittent manner while the gas swirl movement is present in the combustion space, such that the injected fuel is laterally displaced relative to the fuel injection device by the swirl movement.

7. The internal combustion engine as claimed in claim 1 , wherein the operating stroke of the nozzle needle of the injection nozzle needle is controlled to provide an effective flow cross section between the nozzle needle and a nozzle needle seat amounting to about 0.8 to 1.2 times an effective flow cross section of the sum of all the injection bores.

8. The internal combustion engine as claimed in claim 1 , wherein the fuel injection cone angle of each injection bore is between 60° and 160°.

9. The internal combustion engine as claimed in claim 1 , wherein the operating stroke of the nozzle needle is set by one of a two-spring holder and a piezoelectric actuator.

10. The internal combustion engine as claimed in claim 1 , wherein the piston has a dish-shaped piston recess and a projection extending from a center of the piston recess toward the injection nozzle.

11. The internal combustion engine as claimed in claim 10 , wherein the piston recess has, starting from a radially outer region, a flat entry region with a low curvature and, from the region of a maximum recess depth, a greater curvature extending into the piston recess projection.

12. The internal combustion engine as claimed in claim 10 , wherein the piston recess projection has a cone angle in a range of 90° to 140°.