Method to Determine the Mass of Air Trapped in Each Cylinder of an Internal Combustion Engine

A method to determine the mass (m) of air trapped in each cylinder (3) of an internal combustion engine (1);

• wherein the internal combustion engine (1) comprises a number of cylinders (3), each connected to an intake manifold (4), from which it receives fresh air through at least one respective intake valve (5), and to an exhaust manifold (6), into which it introduces the exhaust gases produced by the combustion through at least one respective exhaust valve (7);
• and wherein the intake valves (5) and/or the exhaust valves (7) are controlled so as to change the timing thereof;
• the method comprises:
• determining, based on a filling model using measured and/or estimated physical quantities, a value for a first group of reference quantities including:
• P pressure measured for the engine cycle inside the intake manifold (4);
• n speed of rotation of the internal combustion engine (1);
• OFF mass of gases produced by the combustion in the previous work cycle and present inside the cylinder (3);
• IVC closing delay angle of the intake valve (5);
• determining, based on said filling model, the actual inner volume (V) of each cylinder (3) as a function of the speed (n) of rotation of the internal combustion engine (1) and of the closing delay angle (IVC) of the intake valve (5);
• and
• determining the mass (m) of air trapped in each cylinder (3) as a function of the first group of reference quantities and of the actual inner volume (V) of each cylinder (3) through the following equation:
• m=P*V−OFF [5];
• calculating the mass of gases (OFF) produced by the combustion in the previous work cycle and present inside the cylinder (3), in case the pressure of the intake manifold (4) exceeds the pressure in the exhaust manifold (6), through the following equation:
• OFF=PEXH*VCC/(R*TEXH)−MEXH_SCAV [16]
• PEXH pressure of the gas flow in the exhaust;
• TEXH temperature of the gas flow in the exhaust;
• VCC volume of the combustion chamber of the cylinder (3);
• MEXH_SCAV residual mass of exhaust gases present inside the combustion chamber of the cylinder (3) and directly directed towards the exhaust manifold (6) through the respective exhaust valve (7);
• and
• R constant of the mixture of fresh air and/or exhaust gases.