Light weight steam turbine blade

A steam turbine comprising:

• a) a stationary cylinder for containing a steam flow, and a rotor enclosed by said cylinder;
• and
• b) a row of blades, each of said blades having a root portion attached to said rotor and an airfoil portion, each of said airfoil portions having (i) a base portion and a tip portion defining an airfoil height therebetween., (ii) a leading edge and a trailing edge, (iii) pressure and suction surfaces extending between said leading edge and trailing edge and defining a thickness of said airfoil therebetween said pressure surface over at least a first portion of said airfoil height having a curvature undergoing an inflection at a location thereon, a first portion of said pressure surface disposed upstream of said inflection location and a second portion of said pressure surface disposed downstream of said inflection location, said curvature in said pressure surface first portion being opposite to said curvature in said pressure surface second portion, each of said airfoils having transverse sections disposed radially outward from said root by distances equal to 25%, 50% and 75%, respectively, of said height of said airfoil, and each of said airfoils being defined by the following parameters having approximately the values indicated below, all angles being expressed in degrees:
• ______________________________________ 25% 50% 75% Percent Height Section Section Section ______________________________________ Width (cm) 4.6 4.1 3.6 Pitch/Width Ratio 1.24 1.46 1.78 Pitch/Cord Ratio 0.85 0.86 0.87 Stagger Angle 46.4 53.8 60.5 Max Thickness/Cord 0.24 0.18 0.10 Camber Angle 101 81.2 62.4 Exit Opening (mm) 14.0 15.3 17.0 Inlet Metal Angle 65.1 85.1 105.0 Inlet Included Angle 50.7 55.7 43.8 Suction Surface Turning Angle 12.6 14.8 19.8 ______________________________________

A steam turbine comprising:

• a) a stationary cylinder for containing a steam flow, and a rotor enclosed by said cylinder;
• and
• b) a row of blades, each of said blades having a root portion attached to said rotor and an airfoil portion, each of said airfoil portions having (i) a base portion and a tip portion defining an airfoil height therebetween, (ii) a leading edge and a trailing edge, (iii) pressure and suction surfaces extending between said leading edge and trailing edge and defining a thickness of said airfoil therebetween, said pressure surface over at least a first portion of said airfoil height having a curvature undergoing an inflection at a location thereon, a first portion of said pressure surface disposed upstream of said inflection location and a second portion of said pressure surface disposed downstream of said inflection location, said curvature in said pressure surface first portion being opposite to said curvature in said pressure surface second portion, each of said airfoils having transverse sections disposed radially outward from said root by distances equal to 25%, 50% and 75%, respectively, of said height of said airfoil, and said pressure surface having a curvature at said 25%, 50% and 75% sections as follows, the locations 0% through 100% referring to distances by which each respective locatiuon is displaced from said trailing edge along said pressure surface expressed as a percentage of the total distance along said pressure surface from said trailing edge to said leading edge:
• ______________________________________ Pressure Surface Curvature, mm.sup.-1 (.times. 10.sup.-2) 25% 50% 75% Location Section Section Section ______________________________________ 0% 0.16 0.20 0.17 10% 0.15 0.20 0.17 20% 0.37 0.38 0.26 30% 0.48 0.48 0.38 40% 0.87 0.74 0.41 50% 1.36 1.51 0.76 60% 4.44 2.14 1.76 70% 5.62 3.07 2.56 80% 3.54 4.32 3.30 90% 0.68 0.86 0.47 100% -1.81 -3.53 -2.37 ______________________________________

In a steam turbine, a row of blades, each of said blades having a root portion and an airfoil portion, each of said airfoil portions having:

• a) a base portion and a tip portion defining an airfoil height therebetween;
• b) a leading edge and a trailing edge;
• c) pressure and suction surfaces extending between said leading edge and trailing edge and defining a thickness of said airfoil therebetween;
• d) transverse sections disposed radially outward from said root by distances equal to 25%, 50% and 75%, respectively, of said height of said airfoil, said pressure surface having a curvature at said base and tip portions and at said 25%, 50% and 75% sections as follows, the locations 0% through 100% referring to distances by which each respective location is displaced from said trailing edge along said pressure surface expressed as a percentage of the total distance along said pressure surface from said trailing edge to said leading edge:
• ______________________________________ Presure Surface Curvature, mm.sup.-1 (.times. 10.sup.-2) Base 25% 50% 75% Tip Location Section Section Section Section Section ______________________________________ 0% 0.22 0.16 0.20 0.17 0.04 10% 0.22 0.15 0.20 0.17 0.03 20% 0.25 0.37 0.38 0.26 0.18 30% 0.82 0.48 0.48 0.38 0.20 40% 1.32 0.87 0.74 0.41 0.31 50% 3.38 1.36 1.51 0.76 0.43 60% 5.10 4.44 2.14 1.76 0.50 70% 4.79 5.62 3.07 2.56 0.64 80% 3.41 3.54 4.32 3.30 0.70 90% 2.08 0.68 0.86 0.47 1.07 100% 0.40 -1.81 -3.53 -2.37 1.53 ______________________________________