Internal combustion engine having adjustable linking of its engine units

A method for operating an internal combustion engine, the internal combustion engine comprising a plurality of engine units, each having:

• a working space, in which two rotary pistons are arranged so as to mesh with each other and thereby divide the working space into an in-flow region and an outflow region, wherein the rotary pistons are driven by fluid flowing through the working space;
• a closable inlet opening leading to the inflow region;
• and a closable exhaust gas outlet opening leading away from the outflow region;
• a feed-line pipe which is connected to the inlet openings, and an exhaust gas collection pipe which is connected to the exhaust gas outlet openings, so that the engine units are connected parallel to each other;
• and exhaust gas lines, each leading from an outflow region of one of the engine units to an inflow region of another of the engine units, producing a serial connection between the engine units, the method comprising:
• variably setting, in dependence upon a desired power output, how many of the engine units are operated as internal combustion engines,
• wherein the inlet opening of the respective engine unit is opened to the feed-line pipe, or as expansion engines,
• wherein the respective inlet opening remains closed, and the respective rotary pistons are driven instead by exhaust gas flowing in via one of the exhaust gas lines from another of the engine units.