Method for managing the relative humidity in the air path of an internal combustion engine equipped with a low pressure EGR system

An internal combustion engine comprising

• an intake line;
• an intake manifold connected to the intake line;
• an exhaust line;
• a Low Pressure EGR (LPE) conduit that fluidly connects the exhaust line to a connecting point of the intake line;
• and
• an Electronic Control Unit (ECU) configured to:
• determine an ambient specific humidity;
• calculate specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the specific humidity in the exhaust line and the ambient specific humidity;
• and
• calculate a relative humidity in said portion of the intake line, as a function of the specific humidity.

An apparatus for estimating a relative humidity in an intake line of an internal combustion engine provided with an intake manifold connected to the intake line, an exhaust line, and a Low Pressure EGR (LPE) conduit that fluidly connects the exhaust line to a connecting point of said intake line, said apparatus comprising:

• means for calculating specific humidity in the exhaust line, as a function of an O2 concentration in said exhaust line;
• means for determining an ambient specific humidity;
• means for calculating a second specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold, as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the specific humidity in said exhaust line and the ambient specific humidity;
• and
• means for calculating the relative humidity in said portion of the intake line, as a function of the specific humidity thereof.