Patent GB-792933-A (GB)
Title: Improvements in or relating to full admission impulse hydraulic turbines
IPC: F03B1/00
Filed: 1956-02-21
Abstract: 792,933. Hydraulic turbines. SOC. FINANCIERE D'EXPANSION COMMERCIALE ET INDUSTRIELLE SOC. ANON. SFINDEX. Feb. 21, 1956 [Feb. 22, 1955], No. 5403/56. Class 110 (3). A full admission impulse hydraulic turbine comprising an inlet conduit connected to a spiral casing leading to a distributer which has fixed guide vanes to impart a vortex flow to the operating medium and which diverts the medium in an axial direction on to the turbine rotor, the guide vanes passing through, with the minimum of clearance, an axially movable flow control means actuated by servomotor means, has an annular chamber formed between the control member and the turbine casing to which operating medium withdrawn from a point upstream of the distributer is supplied. Working medium supplied from a pipe 1 flows into a spiral casing 2 and from there into a distributer consisting of a fixed surface 3 having guide vanes 4 rigidly fixed to it and an axially displaceable member 5. The member 5 acts as a flow control member. The clearances between the vanes 4 and member 5 are a minimum so as to prevent leakage of fluid between them. The vanes 4 impart a vortex motion to the fluid which is then diverted in the axial direction so that the free annular flow 6 takes the form of a hyperboloid of revolution. A turbine cover 8 mounted on the casing 2 carries the turbine rotor bearing 9 and two servomotors 12 which actuate the control member 5 through push-rods 13. An annular chamber 11 is formed between the casing 2, cover 8 and member 5. The member 5 is provided with a seal where it contacts the cover 8 to prevent leakage. Operating medium taken from upstream of the guide vanes 4 is fed to the chamber 11 to balance the hydraulic load on the member 5. This medium may be passed into the chamber 11 through a passage 14 in the casing 2 or a groove 15 in the member 5. When the member 5 is in the closed position the walls of the distributer contact at the radius Vo, Fig. 2, and there is a clearance space between the walls of the distributer into which operating medium from the spiral casing may be fed. The hydraulic forces acting on the control member 5 may be varied by varying the relative values of the radii VO, V D  and the pressure in the chamber 11. When V O  > V D  the resultant force on the member 5 will be in the closing direction so that on failure of the control means, the member 5 will be closed. When VD>VO the resultant force on the member 5 will be in the opening direction. When the member 5 is in an operating position, the hydraulic load on the face of the member 5 will vary with the amount of conversion of energy in the vanes 5. It is therefore possible to arrange the values of the radii Vo, V D  so that on failure of the control means the member 5 moves to a position corresponding to the idling position of the turbine. To prevent leakage around the vanes 4 through the member 5, the part of the chamber 11 containing the blades may be separated from the remainder of the chamber by a partition or a seal provided around the blades. The member 5 may be operated by an annular servomotor arranged around the turbine shaft. In a modification the working medium is supplied to the chamber 11 by a pipe containing a control valve. This pipe may be connected at its upstream end either to the spiral casing 2, the inlet pipe 1 or the inlet pipe upstream of a shut-off valve. The member 5 may also be sealed with respect to the casing 2. The parts forming the outlet of the distributer may be removable to facilitate replacement or to adjust the turbine for a change in the working head.