Abstract: An exemplary aerofoil blade for an axial flow turbomachine has a radially inner platform region, a radially outer tip region, an axially forward leading edge, and an axially rearward trailing edge. The aerofoil blade has a pressure surface which is convex in a radial direction, and a suction surface which is concave in the radial direction. The axial width (W) of the aerofoil blade can vary parabolically between maximum axial widths (Wmax) at the platform and tip regions, respectively and a minimum axial width (Wmin) at a position between the platform region and the tip region.

Abstract: The disclosure relates to a multi-stage low-pressure steam turbine and a method for operating thereof. The steam turbine includes a last stage in which the leading edge of each vane of the last stage is skewed so as to form a W shaped K-distribution across the span of the vanes. This shape allows for efficient last stage operation at low last stage exit velocities. The disclosure includes a method for operating such a steam turbine at a last stage exit velocity between 125 m/s and 150 m/s.

Abstract: An exemplary axial flow steam turbine is disclosed which includes a motor, a turbine casing and at least first and second turbine stages, with the second turbine stage being located adjacent to and downstream from the first turbine stage. A radially outer static diaphragm ring of the second turbine stage includes an annular axial extension extending in an upstream axial direction and carrying a circumferential tip sealing device which cooperates with shrouds of a circumferential row of moving blades of the first turbine stage. An upstream end of the annular axial extension is axially spaced from a radially outer static diaphragm ring of the first turbine stage such that a circumferential passage is defined between the upstream end of the annular axial extension and the radially outer static diaphragm ring of the first turbine stage. Solid particles are diverted from steam flow by a circumferential passage during operation.

Abstract: An axial flow gas turbine comprises a turbine and a turbine exhaust section. The turbine comprises a turbine nozzle containing a low pressure turbine stage having an annular row of stator vanes (V2) followed in axial succession by an annular row of rotor blades (B2). The low pressure turbine stage is characterized by the following parameters: the ratio of vane airfoil pitch to vane airfoil axial width (P/W) at the root end of the vane airfoil (V2) is in the region of 1.0 to 1.2, preferably about 1.12; the ratio of blade airfoil pitch to blade airfoil axial width (P/W)at the root end of the blade airfoil (B2) is in the region of 0.6; the ratio of blade diameter at the tip end of the blade airfoil to blade diameter at the root end of the blade airfoil (blade tip/hub diameter ratio) is in the region of 1.6-1.8, preferably about 1.72; and the ratio of the axial length of the exhaust section to the blade airfoil height (L/H) is no greater than a value in the region of 4:1, preferably 3:1.

Abstract: A turbine stator vane for use in an axial flow gas turbine. The vane has an aerofoil, the pressure face of which is convex between platform and tip regions in a plane which extends both radially of the turbine and transversely of the general working fluid flow direction between the vanes. The trailing edge of the aerofoil is straight from platform to tip, and the spanwise convex and concave curvatures of the aerofoil pressure and suction surfaces respectively are achieved by rotational displacement of the aerofoil sections about the straight trailing edge. However, the axial width of the aerofoil is substantially constant over substantially all of the aerofoil radial height and the chord line at mid-height aerofoil sections is shorter than the chord lines in aerofoil sections at platform or tip regions. Reducing chord length at the mid-height region in this way lowers aerodynamic profile losses without unduly affecting vane performance.

Abstract: An axial flow gas turbine comprises a turbine and a turbine exhaust section. The turbine comprises a turbine nozzle containing a low pressure turbine stage having an annular row of stator vanes (V2) followed in axial succession by an annular row of rotor blades (B2). The low pressure turbine stage is characterized by the following parameters: the ratio of vane airfoil pitch to vane airfoil axial width (P/W) at the root end of the vane airfoil (V2) is in the region of 1.0 to 1.2, preferably about 1.12; the ratio of blade airfoil pitch to blade airfoil axial width (P/W)at the root end of the blade airfoil (B2) is in the region of 0.6; the ratio of blade diameter at the tip end of the blade airfoil to blade diameter at the root end of the blade airfoil (blade tip/hub diameter ratio) is in the region of 1.6-1.8, preferably about 1.72; and the ratio of the axial length of the exhaust section to the blade airfoil height (L/H) is no greater than a value in the region of 4:1, preferably 3:1.

Abstract: A turbine stator vane (41) for use in an axial flow gas turbine. The vane has an aerofoil the pressure face of which is convex between platform (45) and tip (46) regions in a plane (48) which extends both radially of the turbine and transversely of the general working fluid flow direction between the vanes. The trailing edge (43) of the aerofoil is straight from platform to tip, and the spanwise convex and concave curvatures of the aerofoil pressure and suction surfaces respectively are achieved by rotational displacement of the aerofoil sections about the straight trailing edge. However, the axial width (W) of the aerofoil is substantially constant over substantially all of the aerofoil radial height and the chord line at mid-height aerofoil sections (44) is shorter than the chord lines in aerofoil sections at platform or tip regions. Reducing chord length at the mid-height region in this way lowers aerodynamic profile losses without unduly affecting vane performance.

Abstract: The invention relates to the design of a fixed-blade assembly in an axial flow steam turbine and is based on the recognition that the design of the interfacing region (fillets) between the radial ends of the blades and the end-blocks to which they are attached or of which they form a part has a significant effect on stage efficiency. The invention recognizes an optimum fillet radius in the range 0.15-0.3 of the throat dimension between the trailing edge of one blade and the suction surface of an adjacent blade, and more particularly 0.20-0.50. The fillet configuration is advantageously applied to a turbine having blades which are of constant cross-section, are curved in the radial (height) direction and are convex from root to tip on its pressure face, the result being a considerable gain in stage efficiency.

Abstract: The invention relates to the design of (particularly) a fixed blade in an axial flow steam turbine. A conventional blade is of prismatic form with an aerofoil cross-section and extends radially between annular end blocks. The inventive blade is curved in the radial (height) direction, being convex from root to tip on its pressure face. The setting angle relative to the corresponding prismatic blade is therefore fine at the root and tip and coarse at the blade mid-height. The throat opening is thus reduced at root and tip and increased at mid-height so displacing some mass flow away from both lossy end wall regions. A considerable gain in the stage efficiency results. A further improvement results from providing an optimum corner fillet between the blades and end walls at the root and tip.