The invention relates to a power production unit including at least one first convergent pipe (11) and an engine (2), the first pipe (11) including an inlet (110) operationally supplied with a fluid moving in an accelerated manner within the first pipe to an outlet (111) of said first pipe (11), and the engine (2) being set up on the outlet (111) of the first pipe (11) and being designed so as to recover at least a fraction of the kinetic energy of the fluid flow passing through the outlet (111) of the first pipe (11). According to the invention, the engine (2) is a positive displacement engine wherein the entire fluid flow, passing through the outlet (111) of the first pipe (11), passes through the positive displacement engine.