ICOPE-15-C052 The reduction of stator blades losses by chord spanwise parabolic variation in an IP steam turbine

抄録

Under the condition of settled stator blade vortex design, the blade chord variation along spanwise direction can significantly change the endwall losses, and possibly the profile loss in the mid-height section. One way to reduce these losses is by decreasing the relative pitch-chord ratio at the root and tip height region, and increasing it or keeping it the same from the original one at the mid-height region. This paper presents a CFD study where two different stator blade chord spanwise variation methods are applied to the stages of an IP steam turbine. The original one is of the traditional method where the stator blade chord remains constantly or increases linearly along blade height. While the new one has the characteristics as follows: the stagger angle and scale of the 2D profile geometry are changed compared with the original one; the variation of blade chord throughout the height of the blade is parabolic, with large chord in the endwall region, and small chord in the mid-height region; the 2D profile stagger angle on different section heights is changed from the original one to maintain the same blade vortex design; the blade number is slightly changed to satisfy the pitch-chord ratio requirements while keeping the section moduli and moments of inertia almost the same. The CFD calculation results show that, with the new design strategy, the stator endwall loss decreased significantly, and the profile loss in the mid-height section reduced slightly as well, compared with the original one.