Axial compressor
An axial compressor includes a plurality of stator vanes attached to an inner surface of a casing defining an annular flow path and a plurality of rotor blades attached to a rotating rotor defining the annular flow path. A flow path is defined between a pressure surface of a stator vane and a suction surface of a stator vane, the vanes being circumferentially adjacent to each other, or between a pressure surface of a rotor blade and a suction surface of a rotor blade, the blades being circumferentially adjacent to each other. The flow path is formed so that a throat portion at which a flow path width is minimized is provided on the upstream side of 50% of an axial chord length.
1. An airfoil designing method in which an axial compressor includes a plurality of stator vanes attached to an inner surface of a casing defining an annular flow path and a plurality of rotor vanes attached to a rotating rotor defining the annular flow path, and a flow path is defined between a pressure surface of a stator vane and a suction surface of a stator vane, the vanes being circumferentially adjacent to each other, or between a pressure surface of a rotor blade and a suction surface of a rotor blade, the blades being circumferentially adjacent to each other, the method comprising the steps of:
adopting a design index on the downstream side of a throat portion at which a width of the flow path is minimized, the design index including a dimensionless value by a ratio of an axial distance and a corresponding reference value, the axial distance being a distance between a point where an equal-pressure line intersects the pressure surface and another point where the equal-pressure line intersects the suction surface; and
designing so that the equal-pressure line approximates a line in a direction perpendicular to a flow along the pressure surface by reducing the axial distance.
2. The airfoil designing method according to claim 1 , wherein different design index values are added to create a two dimensional cross-sectional profile of a given stator vane.
3. The airfoil designing method according to claim 2 , wherein the two dimensional cross-sectional profile of the given stator vane is calculated in accordance with the following expression:
F (objective)=α( F 1 / F 1— base)+β( F 2 / F 2— base)+γ( F 3 / F 3— base),
where F 1 is a shape factor, F 2 is a peak mach number, F 3 is an axial distance of the equal-pressure line, and α, β, γ are weigh factors.
4. The airfoil designing method according to claim 3 , wherein the F(objective) is minimized to obtain a high performance profile.