Leading edge redesign of dual-peak type variable inlet guide vane and its effect on aerodynamic performance

Abstract

Recently, a new type airfoil for variable inlet guide vane (VIGV), featuring “dual-peak” surface velocity pattern at high incidence, is proposed and shows wide low-loss operation range. To further improve its performance, this paper researches the influence of leading edge (LE) thickness and shape on the loss level and surface velocity features of the “dual-peak” type airfoil. Firstly, a polynomial-based continuous-curvature leading edge design method was briefly introduced and used in the LE redesign of sample airfoils. Then, steady simulations based on Reynolds-Averaged Navier-Stokes method (RANS), carried out by commercial software CFX after grid independent study, were used to determine the aerodynamic performance, surface velocity distribution and boundary-layer behaviors of all research airfoils. Simulation results indicate that there exists an optimized range of LE relative thickness that can achieve lower airfoil loss level at high incidence condition. For Case 1 ( ${Ma}_{1\hspace{0.17em}\mathrm{D}}=0.45$ ) and Case 2 ( ${Ma}_{1\hspace{0.17em}\mathrm{D}}=0.60$ ), the optimized LE relative thickness range is $T_{\mathrm{LE}}=022\sim 0.32$ and $020\sim 0.30$ . The LE shape optimization can further reduce the maximum incidence condition loss coefficient with proportion up to 18% for airfoils with optimal LE thickness. Analysis of flow mechanism indicates that the optimized LE thickness and shape can reduce the suction spike height and subsequent adverse pressure gradient, therefore, decrease the LE separation scale and result in a lower loss coefficient. As an application, a dual peak VIGV with circular LE, presented in previous paper as the optimized VIGV, is redesigned in the LE portion according to the research findings and achieved 0.6 percent improvement in passage-averaged total pressure recovery coefficient $\sigma$ at extreme high stagger angle point and the low-loss operation range extends with about 5°, which confirms the effectiveness of the research findings in three-dimensional environment.