Blade for a water current turbine rotor, water current turbine comprising such a blade, associated water current turbine and method for producing such a blade

A rotor for a marine turbine, the rotor comprising:

• an inner ring;
• an outer ring;
• and
• at least one blade extending in a radial direction between the inner ring and the outer ring, the at least one blade comprising:
• an outer surface;
• an inner surface;
• a leading edge;
• and
• a trailing edge,
• wherein the leading edge is an edge of the blade extending generally in the radial direction and positioned upstream following a direction of the water flowing along the blade, and the trailing edge is another edge of the blade opposite the leading edge and positioned downstream following the direction of the water flowing along the blade,
• wherein at least one portion of the blade presenting, in a transverse section according to a cross section, a profile comprising a thick part and a thin part, wherein the cross section is perpendicular to the radial direction, the thick part and the thin part are each with a maximum thickness in a direction that is perpendicular to the outer surface, the maximum thickness of the thick part being at least four times greater than the maximum thickness of the thin part, and
• wherein a length of a curve of the thin part is between 0.1 times a length of a cord between the leading edge and the trailing edge and 0.9 times the length of the cord inclusive.

A method for manufacturing a blade for a rotor of a marine turbine, the blade extending in a radial direction and including an outer surface, an inner surface, a leading edge, and a trailing edge, wherein the leading edge is the edge of the blade extending generally in the radial direction and positioned upstream following a direction of the water flowing along the blade, the trailing edge is the edge of the blade opposite the leading edge and positioned downstream following the direction of the water flowing along the blade, the method comprising:

• calculating, for every point of the leading edge, a profile of the blade in a transverse section according to cut cross section passing through the point of the leading edge 06)-and perpendicular to the radial direction;
• and
• manufacturing the blade according to the calculated profile,
• wherein calculating the profile of the blade comprises:
• choosing a first intermediate point along a predetermined curve of an outer surface, the first intermediate point being distinct from a first end and a second end of the predetermined curve of the outer surface;
• determining a first portion of a curve of an inner surface, via a symmetry calculation, with respect to a straight line passing through the first intermediate point and the first end of the predetermined curve of the outer surface, of the portion of the predetermined curve of the outer surface between the first end and the first intermediate point inclusive;
• deleting a section of the first portion of the curve of the inner surface between the first intermediate point and a second intermediate point inclusive, positioned along the first portion in order to obtain a first shortened portion;
• and
• of determining a second portion of the curve of the inner surface by connecting the second intermediate point to the second end via a geometric line,
• wherein the first shortened portion and the second portion forming a the curve of the inner surface, and the profile is formed by the predetermined curve of the outer surface and the curve of the inner surface.