PURPOSE: To utilize energy of fluid with high efficiency through concentration of lean flow velocity energy by a method wherein a high pressure chamber is arranged at an outer box of which a diffuser consists to blow in a boundary layer and a low pressure chamber is arranged to suck out a boundary layer.

CONSTITUTION: A diffuser 3 is arranged in the rear of a turbine 1 in an outer box 2. By utilizing suction force generated by decelerating flow velocity to a value at a part C and at a delivery port of a part D, the flow velocity at a suction port 4 of a part A is boosted by a part B and a turbine 1 is driven by current energy. A high pressure chamber 6 having an opening 5 is arranged at a the part A at the front of the outer box 2. By utilizing a high pressure by a stagnation effect in front of the outer box 2, a high velocity flow is blown off through a blowoff port 7 to a boundary layer growing on the surface of a diffuser 3 by means of a friction loss and a diffuser effect is improved. A low pressure chamber 9 having an opening 8 at a shoulder part near a position closer to the outside of the part A of the outer box 2.