Abstract
Though the importance of curvature continuity on compressor blade performances has been realized, there are two major questions that need to be solved, i.e., the respective effects of curvature continuity at the leading-edge blend point and the main surface, and the contradiction between the traditional theory and experimental observations in the effect of those novel leading-edge shapes with smaller curvature discontinuity and sharper nose. In this paper, an optimization method to design continuous-curvature blade profiles which deviate little from datum blades is proposed, and numerical and theoretical analysis is carried out to investigate the continuous-curvature effect on blade performances. The results show that the curvature continuity at the leading-edge blend point helps to eliminate the separation bubble, thus improving the blade performance. The main-surface curvature continuity is also beneficial, although its effects are much smaller than those of the blend-point curvature continuity. Furthermore, it is observed that there exist two factors controlling the leading-edge spike, i.e., the curvature discontinuity at the blend point which dominates at small incidences, and the nose curvature which dominates at large incidences. To the authors’ knowledge, such mechanisms have not been reported before, and they can help to solve the sharp-leading-edge paradox.
Highlights
The design principles and methods for blade profiles have been studied over the years to improve fan or compressor efficiency, and improve the overall performance of gas turbine-based power plants and aeroengines
The traditional circular leading edge results in a large curvature discontinuity when it is blended with the main surface, which is thought to lead to a large spike in the pressure distribution on the profile and result in a narrow working range of the blade cascade
The conventional airfoil theory suggested that a sharp leading edge usually leads to a large spike in the pressure distribution on the profile and results in a narrow working range of the blade cascade, which can be seen from the criteria for leading-edge separation proposed by Tuck [5] and Elmstrom et al [6]
Summary
The design principles and methods for blade profiles have been studied over the years to improve fan or compressor efficiency, and improve the overall performance of gas turbine-based power plants and aeroengines. The conventional airfoil theory suggested that a sharp leading edge usually leads to a large spike in the pressure distribution on the profile and results in a narrow working range of the blade cascade, which can be seen from the criteria for leading-edge separation proposed by Tuck [5] and Elmstrom et al [6] It has been found paradoxically in experiments and numerical computations by several researchers that instead the sharpest leading edge has the widest working range [3,7], and it has been widely accepted that the elliptical leading edge helps to avoid the separation bubble, to reduce the profile loss and to enlarge the working range [1,2,8,9,10]. Theoretical analysis will be carried out to find deeper explanations for the above questions, which can support the numerical results
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