Turbodrill

Abstract

A turbodrill comprises a housing in which there are fixed stators having blades forming a circular pattern and defining guide passages for the flow of drilling fluid fed by mud pumps, and a shaft mounted on a thrust bearing and having rotors fixed thereto, the blades of the rotors also forming a circular pattern and having the direction opposite to the stator blades so that the rotor rotates relative to the stator. The rotor and stator blades are shaped such a manner that an angle .theta. between the tangents to the middle line of the profile at the inlet and outlet edges of the blade determining the profile camber is selected in accordance with the relationship .theta. = 180.degree. - (from 4.5 to 7).alpha..sub.1, an angle .alpha..sub.2 between the line perpendicular to the axis of the pattern and the tangent to the middle line of the profile at the outlet edge of the blade is selected in accordance with the relationship .alpha..sub.2 = (from 3.5 to 6).alpha..sub.1, wherein .alpha..sub.1 is an angle between the line perpendicular to the axis of the pattern and the tangent to the middle line of the profile at the inlet edge thereof as measured in the direction towards the concave portion of the profile, and the ratio of maximum thickness '.DELTA.' of the blade profile to the chord '1' thereof is selected within the range .delta./1 = from 0.09 to 0.19.