An apparatus is disclosed that includes a fluid inlet in fluid communication with a valve assembly, the valve assembly structured to selectively permit the flow of a motive fluid from the fluid inlet to a fluid driven motor, wherein the valve assembly further includes a first plunger including a plurality of axially extending fluid channels, wherein the plunger is selectively movable by an actuator in a manner such that as the plunger is displaced farther away from a closed position, the number of axially extending fluid channels placed in fluid communication with the fluid inlet increases, and wherein the axially extending fluid channels permit the flow of the motive fluid from the fluid inlet to the fluid driven motor.