Variable orifice rotary control valve

A rotary control valve is provided. The valve includes a valve body having a first valve member with a first volute formed therein, wherein the first volute further includes a plurality of flow channels of varying diameter or a single flow channel having a generally smooth gradient from large to small diameter; and a second valve member in close proximity to or in direct contact with the first valve member with a second volute formed therein, wherein the second volute further includes a plurality of flow channels of varying diameter or a single flow channel having a generally smooth gradient from large to small diameter. The first and second volutes cooperate with one another to form an orifice between the first and second valve members, and the diameter of the orifice is variable based on the positions of the individual flow channels relative to one another. Also included are means for axially rotating the first and second valve members in opposite directions relative to one another for varying the size of the orifice formed between the valve members.