Method for operating an internal combustion engine having a feed line for feeding in an air mixture and having an exhaust line

A method for operating an internal combustion engine (10), the internal combustion engine (10) having a feed line (14) for feeding an air mixture into the internal combustion engine (10), the feed line (14) having a first section (27) at a comparatively low pressure, a compressor (22) for compressing the air mixture fed in, and a second section (29) at a comparatively high pressure arranged in series in the feed direction, the internal combustion engine (10) having an exhaust line (12) for discharging exhaust gas from the internal combustion engine (10), the exhaust line (12) having a section (43) in which the exhaust gas is at a comparatively low pressure, and the internal combustion engine (10) having an exhaust gas recirculation system (50) which recirculates into the first section (27) of the air feed (14) at least part of the exhaust gas which flows through the section (43) of the exhaust line (12) at the comparatively low pressure, and the recirculated part of the exhaust gas and fresh air fed in forming the air mixture flowing through the feed line (14), characterized in that a first mass flow (71) of the recirculated part of the exhaust gas is determined by means of the following steps:

• (a) determining a second mass flow (72) flowing through the compressor (22);
• (b) determining a third mass flow (70) of the fresh air fed in;
• and
• (c) determining the first mass flow (71) by subtracting the third mass flow (70) determined in step (b) from the second mass flow (72) determined in step (a).