Self-igniting, mixture-compressing internal combustion engine and method for its operation

#The invention relates to a self-igniting, mixture-compressing internal combustion engine and to a method of operating same.

#DE 44 19 429, which is hereby incorporated by reference in its entirety, discloses an internal combustion engine that burns a gaseous fuel/air mixture, i.e. aerolized fuel, in a main combustion space, the said mixture being ignited from a combustion prechamber. The prechamber is connected to a high-pressure fuel-gas line and forms a fuel-rich mixture which self-ignites and, as a result of the further increase in pressure, flows over into the main combustion space where it burns completely and in the process ignites the compressed fuel/air mixture.

#It is an object of the invention to significantly reduce the proportion of fuel gas, which is injected in highly compressed form into the prechamber.

#In the drawings:

#FIG. 1 is a cross-sectional view of a partial internal combustion engine and insert in accordance with one embodiment of the present invention wherein a shield of the nozzle is substantially sleeve-like.

#FIG. 2 is a cross-sectional view of a partial internal combustion engine and insert in accordance with one embodiment of the present invention wherein a shield of the nozzle is substantially disk-like.

#Herein, the invention is explained in greater detail using an exemplary embodiment. Parts of an internal combustion engine designed according to the present invention are shown in FIG. 1. The customary devices for gas exchange and a piston, which are not shown in FIG. 1, are provided at the cylinder and combustion space. The cylinder head 5, into which an insert 1 is mounted, for example by screwing it in, is not shown i.e. is broken away. A prechamber 4 which is connected to the main combustion space 7 by preferably a plurality of passage openings 6 that are formed in the insert 1.

#Fuel gas is introduced at high pressure into the prechamber 4, forming a jet 8, through a nozzle 10, preferably a throttle pintle nozzle as used herein interchangeably. As a result of the characteristics of jet 8, the fuel gas can mix very intensively with the fuel/air mixture present in the prechamber 4 before it ignites on the hot surface of the glow plug tip 2a or self-ignites. The resultant rapid increase in pressure in the prechamber 4 ensures stable ignition of the relatively lean fuel gas/air mixture in the main combustion space 7. In addition to these advantages, preferably the throttle pintle nozzle 10 has a self-cleaning effect, thus carbon deposits are prevented at its ejection cross-section.

#The throttle pintle nozzle 10 is subjected to high thermal stresses because of the low internal cooling resulting from using fuel gas having a relatively low heat capacity and poor heat transfer compared to liquid fuels, and further because of the low amounts of fuel flushed through the nozzle 10. Thermal stresses can be reduced by providing a protective shield 9 which shields the throttle pintle nozzle 10 with respect to the prechamber 4 so that heat transfer from the prechamber 4 is reduced. The protective shield 9 preferably consists of a material with good thermal conductivity, such as copper, and is of disc-shaped or sleeve-shaped design. The sleeve-shaped protective shield 9 shown by way of example in the figure encloses the throttle pintle nozzle 10 in the front region. An opening for the ejection of the fuel gas is provided in the ejection region. This opening can be provided with a conical depression in order to avoid impeding the jet 8. In one embodiment, illustrated in FIG. 2, protective shield 9 is disk-shaped and is arranged only in the region of the ejection opening of the nozzle without the front region being shielded.