Application of MCST method to design the blade leading edge in axial compressors

A blade leading edge spike flow can usually be found on the condition that the discontinuous curvature curves between blade leading edge and blade surface, which is a common result of design the blade with separate curves of blade leading edge and blade surface in traditional blade design procedure. However, in recent, many researchers found that strong leading edge spike might cause significant detrimental effect on blade performance. In order to weaken or even eliminate the leading edge spike flow, blade leading edge should be designed carefully to connect with the blade surface with a smooth curvature change. In the present paper, a novel blade leading edge curve design method, named as CST ("class function/shape function" transformation technique) method, was improved for compressor blade design. Shape function in the hyperbolic form was put forward to ensure radius and thickness of the leading edge can meet the requirements of the engineering manufacturing under the premise of continuous curvature. By using the aforementioned blade leading edge redesign method, a series of compressor blade profiles were designed with curvature-continuous blade leading edge. The designed operating Mach number ranged from 0.5 to 1.1. And then, the aerodynamic characteristics of each blade profile were analyzed by numerical method. The simulation results showed that after the redesign of blade leading edges, when the inlet Mach number less than 0.85, the useful blade incidence range can increase about 2 degree, and minimum blade profile loss can decrease about 8%. Finally, the profiles of an inlet stage in a transonic axial-compressor were regenerated by using the modified CST method. The numerical simulation results showed that, compared to the prototype, the compressor peak efficiency increased nearly 1.5 points, and the pressure ratio increased about 2%.