An estimation device is applicable to a combustion system in which relative movement of a piston to a cylinder is lubricated with a lubricating oil. An estimation device includes a mixing acquisition unit and a piercing force estimation unit. The mixing acquisition unit acquires a mixing ratio of various components contained in a fuel injected into the combustion chamber. The piercing force estimation unit estimates a piercing force of the fuel injected into the combustion chamber according to the mixing ratio acquired with the mixing acquisition unit to manage reach of the fuel, which is injected into the combustion chamber of the internal combustion engine, at least one of the cylinder and the piston.

A cavity includes a lower-side cavity, an upper-side cavity, a first lip and a second lip. The upper-side cavity has a guide curved surface which extends along a circumference of a first imaginary circle in a section along a cylinder-axis direction, and the first lip has a curved surface which extends along a circumference of a second imaginary circle in a section along the cylinder-axis direction. An angle X which a cylinder axis makes with a common tangential line of the first imaginary circle and the second imaginary circle is set as 75<X<80. The guide curved surface is configured such that an angle Y of this guide curved surface which occupies at the circumference of the first imaginary circle is set as 80<Y<(180X).

A combustion control method in an engine of a vehicle, the method includes the following steps. A step of specifying a NOx concentration in an exhaust gas, when an EGR rate is out of a first reference range, and determining whether a value thereof falls within a predetermined second reference range; a step of, estimating a heat generation rate profile indicating crank angle dependency of a heat generation rate in the engine, when the NOx concentration is determined out of the second reference range; and a step of comparing a value of an index characterizing the estimated heat generation rate profile with a value of an index in an ideal heat generation rate profile specified from a driving condition of the vehicle and controlling a combustion condition in the engine based on a result.

A method for ascertaining whether a combustion process is being carried out in a cylinder of an internal combustion engine, it being decided whether or not the combustion process is present as a function of a relative angle between a characteristic signature of a variable characterizing a time curve of a state variable of the internal combustion engine and a specifiable crankshaft angle.

A control device for an internal combustion engine provided with a combustion control part successively performing at least first main fuel injection and second main fuel injection for causing premix charged compression ignition of fuel so that a pressure waveform showing a change of a rate of cylinder pressure rise over time becomes a two-peak shape and a peak ratio which is a ratio of a first peak value of a first peak of the pressure waveform and a second peak value of a second peak falls within a predetermined range. The combustion control part calculates the ignition delay time of the fuel injected by the second main fuel injection (second ignition delay time) and reflects the injection correction amount in the target injection amount of the second main fuel injection (second target injection amount) if an injection correction amount is set for the amount of fuel injected from the fuel injector and the second ignition delay time is less than a predetermined value.

A control device for an engine is provided, which includes a fuel injector attached to the engine, a spark plug disposed to be oriented into a combustion chamber, a swirl control valve provided in an intake passage, and a controller connected to the fuel injector, the spark plug, and the swirl control valve and configured to control the fuel injector, the spark plug, and the swirl control valve. The swirl control valve closes in a given operating state of the engine. The fuel injector injects fuel after the swirl control valve is closed, between intake stroke and an intermediate stage of compression stroke. The fuel injector injects the fuel after the first fuel injection. The spark plug performs the ignition after the second fuel injection so that the mixture gas starts combustion by flame propagation and then unburned mixture gas self-ignites.

A method of detecting knocking includes: an in-cylinder pressure obtaining step of obtaining an in-cylinder pressure of a cylinder of the internal combustion engine at a plurality of crank angles; a heat generation rate calculation step of calculating a heat generation rate of the cylinder at each of the plurality of crank angles; an in-cylinder pressure maximizing crank angle obtaining step of obtaining an in-cylinder pressure maximizing crank angle at which the in-cylinder pressure of the cylinder of the internal combustion engine is at a maximum value; a knock determination crank angle region decision step of deciding a knock determination crank angle region which is a region between a smaller crank angle smaller than the in-cylinder pressure maximizing crank angle by a first value and a larger crank angle larger than the in-cylinder pressure maximizing crank angle by a second value; a heat generation rate differentiation step of calculating a differential value of the heat generation rate in the knock determination crank angle region; and a first knocking determination step of determining knocking on the basis of the differential value of the heat generation rate calculated in the heat generation rate differentiation step.

A control device for a compression ignition engine is provided, which causes an injector to perform a pre-injection and a main injection, sets fuel injection timings of these injections so that an interval between a first peak of a heat release rate resulting from the combustion of fuel injected by the pre-injection and a second peak of the heat release rate resulting from the combustion of fuel injected by the main injection becomes an interval to make pressure waves caused by these combustions cancel each other out, and when an increase of an oxygen concentration of intake air supplied to a combustion chamber is detected, controls the injector to reduce the injection amount and retard the injection timing of the pre-injection compared with a case where the concentration increase is not detected under a condition that engine load and speed are the same.

An engine control system includes: a delay estimating unit configured to estimate a auto-ignition delay based on first parameters including a composition of fuel gas; a auto-ignition predicting unit configured to predict a auto-ignition timing based on the auto-ignition delay; a completion predicting unit configured to predict a combustion completion timing of the fuel gas; and an operation control unit configured to control an engine based on a result of comparison between the auto-ignition timing and the combustion completion timing.

According to one or more embodiments, an internal combustion engine may be operated by a method which includes one or more of passing a first fuel and a second fuel into an engine cylinder to form a fuel mixture, and combusting the fuel mixture with a spark plug to translate a piston housed in the engine cylinder and rotate a crank shaft coupled to the piston. The first fuel may comprise a greater octane rating than the second fuel. A target CA50 may correspond to a minimum in specific fuel consumption of the fuel mixture. The spark plug may initiate combustion at a time such that the internal combustion engine operates with an operational CA50 that is within 20 degrees of the target CA50.