<p>The hydrodynamic retarder has blades (2), carrying filler channels (7), which are made such that they narrow from the blade base (3) to the blade leading edge (5). A local thickening (8) for the filler channel is provided in the rear side of the blade in the region of the leading edge. The filler channels are provided in the stator blade wheel and they are also provided in the rotor blade wheel. The cross section of the channels can be circular or oval.</p>
