A combustion chamber structure for an internal combustion engine includes a recessed portion formed in a pent roof of a cylinder head on an upstream side of a tumble flow with respect to a spark plug.

To accurately evaluate combustion stability in consideration of the effect of the trend even at the time of the transient operation. The present invention is configured to have a combustion energy calculation unit that calculates a combustion energy W_t of one combustion cycle in an internal combustion engine, a trend calculation unit that calculates a trend Tr of change in the combustion energy W_t calculated by the combustion energy calculation unit in a plurality of the combustion cycles, and a combustion stability judgment unit that judges combustion stability based on the combustion energy W_t in the plurality of combustion cycles and the trend Tr of change calculated by the trend calculation unit.

A spark ignition internal combustion engine includes: intake and exhaust valves disposed at a ceiling part of a combustion chamber; and a fuel injection valve including a tip end portion including injection holes, and being structured to inject fuel through the injection holes toward a crown of a piston, wherein the tip end portion of the fuel injection valve is arranged in a region of the ceiling part surrounded by the intake and exhaust valves. A fuel injection control includes: determining a tip end portion fuel temperature directly or indirectly, which is a temperature of fuel at the tip end portion of the fuel injection valve; and setting a fuel injection timing advanced, in response to a condition that the tip end portion fuel temperature is higher than a temperature threshold value, wherein the temperature threshold value relates to flash boiling of fuel at the injection holes.

Among all combinations of two injection holes, in a combination in which when the injection holes are offset such that their central axes are coincident with each other in inlet openings, an inter-injection hole angle formed by the central axes is minimized, the inter-injection hole angle between the two injection holes is represented as yamin[deg], taper angles, which are formed by the respective contours of the injection hole inner walls in the cross sections along the virtual planes including the central axes of the two injection holes that allow the inter-injection hole angle to be minimized, are represented as a1 and a2[deg], and when fuel is injected from the injection holes, average pressure of the fuel in the fuel passage is represented as P[Mpa], and the injection holes are formed so as to satisfy a relationship: amina1+a2+0.5P.sup.0.6.

In a compression-ignition engine having a two-stage cavity, the distribution ratio between fuel for an upper cavity and fuel for a lower cavity is maintained even when the operational state of the engine changes. A piston of the engine includes a lower cavity, an upper cavity, and a lip portion therebetween. A controller causes a main injection and at least one pilot injection to be executed when the engine operates in a first state and a second state in which the load is lower than the load in the first state. The fuel spray is distributed to the lower cavity and the upper cavity. The controller sets the timing of the pilot injection(s) so that the distribution ratio of the fuel spray of the pilot injection(s) for the lower cavity is higher when the engine operates in the first state than when in the second state.

Various systems are provided a piston for an engine. The piston has a piston crown, which includes a plurality of protrusions for enhancing mixing in a combustion chamber. As one example, a piston crown includes a plurality of protrusions extending outward from a top surface of the piston crown and spaced apart from one another around a circumference of the piston crown, each protrusion of the plurality of protrusions increasing in height and decreasing in width as the protrusion extends outward from a central axis of the piston crown.

An in-cylinder injection engine includes: a cylinder head that includes a gasket surface stacked on a seating face of a cylinder block and defines a combustion chamber between a piston and a ceiling surface gradually receding from an imaginary plane including the gasket surface in going toward a center of the cylinder head; two intake ports disposed side by side and opened in the ceiling surface of the cylinder head; and a fuel injection valve mounted to the cylinder head and having an injection port facing the combustion chamber at a position between an opening of the intake port and the gasket surface. The intake port is formed to have a shape of introducing an airflow laterally into the combustion chamber along the imaginary plane. Accordingly, the in-cylinder injection engine can reduce attachment of injected fuel to a wall surface of a cylinder bore.

The present invention relates to a combustion chamber of a combustion engine. The combustion chamber comprises a single intake valve (2), a single exhaust valve (3), a fuel injector (5) and two plugs (4). According to the invention, the combustion chamber is substantially elliptical (6) and the components of the combustion chamber are arranged as follows: valves (2, 3) are located at the ends of the major axis (8) of ellipse (6), plugs (4) are located close to the minor axis (9) of ellipse (6), fuel injector (5) is located on the periphery of ellipse (6) between intake valve (2) and a plug (4).

The deterioration of combustion due to condensed water flowing into a cylinder is suppressed as much as possible. A control apparatus for an internal combustion engine is applied to an internal combustion engine which includes a fuel injection valve that directly injects fuel into a cylinder and a spark plug. The internal combustion engine is constructed so that the fuel goes to the spark plug. The control apparatus comprising a controller configured to: predict whether condensed water flows into the cylinder during an intake stroke; and carry out first injection control to perform fuel injection in a predetermined period of time within a period of time which is after closure of an exhaust valve and before the condensed water flows into the cylinder, and second injection control to perform fuel injection in a compression stroke before ignition, if an inflow of the condensed water into the cylinder is predicted.

Methods and systems are provided for a fuel injector. In one example, a system comprises an injector spool valve having a fuel outlet shaped to flow fuel to different portions of a nozzle inlet based on an actuation of the injector spool valve, thereby adjusting a fuel injection angle of a fuel injection.