Numerical and Theoretical Investigations Concerning the Continuous-Surface-Curvature Effect in Compressor Blades

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. OPEN ACCESSEnergies 2014, 7 8151

Computational methods for investigation of surface curvature effects on airfoil boundary layer behavior

“…Point P sk is the point connecting resultant line y1 (from the thickness distribution) to the main part of the airfoil y2, corresponding to curvature point C1s, as in Figure 2(d). The suction side construction line can be of the form: y(x) ¼ Ax 2 þ Bx þ C, and the thickness distribution y t can be expressed as: where functions k 11 , k 12 , k 13 , and k 14 are exponential polynomials, similar to k 1 and k 2 as explained in the subsection of TE design. These exponential functions have increasing importance when approaching the end points P s1 and P sk of line segment y1.…”

“…12 To eliminate unnecessary local changes of surface curvature, surface curvature distribution becomes one of the key factors in the design of high-efficiency airfoils and blades. [13][14][15] Siddappaji et al 16 developed a parametric 3D blade design tool for turbomachinery, and they used the definition of splines to modify the blade shapes and obtain the desired blade model. In their research, the curvature as well as the slope-of-curvature distributions of the blade surface are both continuous due to the application of the splines.…”

“…Massardo et al 19,20 used streamline curvature distribution calculations to determine the 3D variation of inlet and outlet flow angles for axial-flow compressor design and improved the compressor efficiency. Based on surface curvature distribution, Song et al 13,21 showed that improving the curvature continuity at the leading-edge blend point of a compressor blade improved performance by helping to eliminate the separation bubble. They also proved that the main surface curvature continuity improves blade performance.…”

Surface curvature effects on the tonal noise performance of a low Reynolds number aerofoil

“…Korakianitis et al proposed a design method [20] to optimize aerofoils by ensuring continuous distributions of curvature and gradient-of-curvature along the surfaces, and showed that the aerodynamic and heat transfer performance strongly depended on curvature and gradient-of-curvature distribution. Based on surface curvature distribution, Song et al [21] showed that continuous curvature distribution at the LE blending position of a compressor blade improves performance by helping to eliminate the separation bubble.…”

Performance Analysis of a Compressor Leading Edge without Pressure Spike at High Subsonic Speed

“…They reduced the total pressure loss by 10 %. Song et al [7] carried out RANS and LES simulations for circular, elliptical and continuous curvature compressor leading edge geometries. Under consideration of the simulation results, they tried to give a theoretical explanation for the pressure spike occurrence due to a curvature discontinuity.…”