Internal combustion engine
An internal combustion engine includes a combustion chamber, a fuel injector injecting fuel into the combustion chamber, a cylinder, a piston having a crown and reciprocating in the cylinder, the crown being exposed to the combustion chamber, and an ignition delay enhancer prolonging an ignition delay of a fuel-air mixture in the combustion chamber. A ceramic member is disposed on at least a fuel injection port, to which fuel is injected from the fuel injector, of the crown of the piston.
1. An internal combustion engine, comprising:
a combustion chamber;
a fuel injector injecting fuel into the combustion chamber;
a cylinder;
a piston having a crown and reciprocating in the cylinder, the crown being exposed to the combustion chamber; and
an ignition delay enhancer prolonging an ignition delay of a fuel-air mixture in the combustion chamber,
wherein the crown of the piston includes a ceramic member and an aluminum alloy base, the ceramic member is disposed on a position to which at least fuel is injected from the fuel injector, and the aluminum alloy base is disposed on a position to which fuel is not injected from the fuel injector,
the crown of the piston has a cavity defining part of the combustion chamber, the fuel injector injecting fuel to the cavity,
the ceramic member is disposed on at least a portion of the crown of the piston, the portion facing the cavity, and
an overhang ratio that defines a boundary between the ceramic member and the aluminum alloy base ranges from 0.57 to 0.96, the overhang ratio being represented by the ratio d 1 /d 2 where d 1 is a diameter of the boundary between the ceramic member and the aluminum alloy base on a top surface of the crown of the piston and d 2 is a maximum diameter of the boundary between the ceramic member and the aluminum alloy base in a radial direction of the piston.
2. The internal combustion engine according to claim 1 , wherein the ceramic member is combined with the aluminum alloy base constituting the piston.
3. The internal combustion engine according to claim 2 , wherein the ceramic member is combined with the aluminum alloy base constituting the piston by mechanical coupling, junction, shrink fitting, press fitting, or enveloped casting.
4. The internal combustion engine according to claim 3 , wherein the ceramic member is formed by die molding, cold isostatic pressing, extrusion molding, injection molding, slip casting, or gel casting.
5. The internal combustion engine according to claim 1 , wherein the ceramic member on the crown of the piston comprises a material having a thermal conductivity of 30 W/mK or less.
6. The internal combustion engine according to claim 5 , wherein the ceramic member on the crown of the piston comprises a material having a thermal conductivity of 20 W/mK or less.
7. The internal combustion engine according to claim 1 , wherein the ceramic member on the crown of the piston comprises silicon nitride, SiAlON, stabilized zirconia, or a mixture containing at least one of these materials.
8. The internal combustion engine according to claim 1 , wherein the ignition delay enhancer performs exhaust gas recirculation (EGR) for recirculating part of exhaust gas after combustion in the combustion chamber into intake air to prolong an ignition delay of a fuel-air mixture in the combustion chamber.
9. The internal combustion engine according to claim 8 , wherein the ignition delay enhancer keeps an EGR rate of 15% or more in recirculation of exhaust gas.
10. The internal combustion engine according to claim 1 , wherein the ignition delay enhancer keeps a compression ratio of 17 or less by controlling reciprocation of the piston to prolong an ignition delay of a fuel-air mixture in the combustion chamber, the compression ratio being the ratio of the maximum volume to the minimum volume of the combustion chamber.
11. The internal combustion engine according to claim 1 , wherein the ignition delay enhancer advances or delays a fuel injection timing such that a main heat generation takes place after a main fuel injection in the combustion chamber to prolong an ignition delay of a fuel-air mixture in the combustion chamber.
12. The internal combustion engine according to claim 1 , comprising a supercharger supercharging intake air into the combustion chamber.
13. An internal combustion engine, comprising:
a combustion chamber;
a cylinder;
a piston having a crown and reciprocating in the cylinder, the crown being exposed to the combustion chamber; and
an ignition delay enhancer prolonging an ignition delay of a fuel-air mixture in the combustion chamber,
wherein a ceramic member is disposed on the crown of the piston and a ceramic member is disposed on at least a part of a cylinder liner,
the ceramic member on the cylinder liner and the ceramic member on the crown of the piston comprise different materials, and
the ceramic member on the cylinder liner comprises a porous material having interconnected pores.
14. The internal combustion engine according to claim 13 , wherein the cylinder liner is disposed on an inner surface of the cylinder, the cylinder liner facing an outer surface of the piston, and
the ceramic member on the cylinder liner facing the crown of the piston.
15. The internal combustion engine according to claim 14 , wherein the ceramic member on the cylinder liner comprises silicon nitride, alumina, mullite, SiAlON, stabilized zirconia, silica, or a mixture containing at least one of these materials.