Abstract: An impeller for a turbine includes a conical body having a wider end, a narrower end and an outside surface, a front end surface connected to the wider end of the conical body, a back end surface connected to the narrower end of the conical body, and a plurality of helical grooves disposed in the outside surface of the conical body wherein the helical grooves decrease in depth from the wider end to zero depth near the narrower end.