Abstract
With recent advancements in the development of material and manufacturing technology, the leading edge geometry of turbomachine blades has attracted widespread attention. “Sharp” leading edges always have a better aerodynamic performance, though it is prone to deformations easily. Thus, flat plates and real compressor cascades with different leading edge deformations were investigated to study the influence, which is applicable for thin blades at low speeds. Different boundary layer characteristics, including the velocity profile, transition process, and loss, are compared. The results show that there are several kinds of contradictory influence mechanisms and that the final phenomenon is closely related to the condition of the original boundary layer. In low turbulence, with large and laminar separation, the deformations can suppress separation and decrease loss. In high turbulence, with short and transitional separation, deformations can promote the transition process and increase the loss. The sensitivities of different the original leading edge shapes are also compared. This indicates that a good design always has a better robustness at low turbulence values, while it is worse at high turbulence values. The cascade experiment and simulation show that the deformation influence is similar to flat plates and that it is enlarged near the hub, which affects the corner separation.
Highlights
For the sake of energy conservation and cost saving, the turbomachine blades should be improved in two aspects, namely, increasing the mechanical efficiency and prolonging the service life
WEDGE is a cut between the nose and a certain point at the leading edge surface
This means that deformations are more likely to happen
Summary
For the sake of energy conservation and cost saving, the turbomachine blades should be improved in two aspects, namely, increasing the mechanical efficiency and prolonging the service life. Norris [1] found in his case study of the Rolls Royce Trent 700EP that the profile loss was reduced by 30% and that the fuel was reduced by 1.3% with the blades’ circular leading edge updated by the ellipse. For the aero-engine or other turbomachines, the blade profile loss is mainly caused by the suction surface boundary layer, except for a large negative incidence. At the leading edge region, the velocity of the boundary layer outer edge increases and decreases because of the wall curvature [2]. This makes it very easy to cause separation and transition, which brings more loss [3]. The present study has involved several aspects, such as the leading edge shape, incidence, Reynolds number, free-stream turbulence, and Mach number
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