Numerical investigations on the aerodynamic influence of eroded leading-edge geometry on boiler fan performance

Axial fans handling high temperatures or corrosive gases in power stations are exposed to erosion phenomena that result in increased surface roughness or modifications of blade section shapes. Erosion results in the reduction of blade chord and effective camber, thus altering the turning flow and the actual blade load. Consequently, aerodynamic performance gradually reduces, and in some circumstances reduces drastically as the rotor's structural integrity is undermined. The present paper investigates the influence of leading edge geometry in a high pressure boiler fan designed for forced-draft application in coal fired power plant. To this end, a comparative analysis considers: (i.) the datum blade section, (ii.) a modified blade. The datum blades represent the original blade geometry. The modified blade represents eroded blade geometry, as measured after in-service operation including suction and pressure side wear. The study concludes with (iii.) a re-shaped blade. The authors carried out the simulations using an in-house developed multilevel parallel, finite element RANS solver, with the adoption of non-isotropic turbulence closure. The authors investigated rotor aerodynamics by comparing the pressure fields and the boundary layer development on the blade suction surfaces that limit the pressure rise and flow turning.