Research on operational characteristics of coal power centrifugal fans at off-design working conditions based on flap-angle adjustment

Abstract

The coal power centrifugal fan (CF) is one of the most significant equipment in coal power plants, which usually works at off-design conditions according to the demand of electricity consumption. Consequently, the efficiency of CFs is far lower than the designed maximum efficiency under this condition, causing large amounts of potential energy wasted. A novel flap-angle adjustment (FAA) method is proposed to efficiently solve this problem in the CF system. This manuscript establishes a theoretical model of the flap-angle adjustable centrifugal fan (FAACF). The operating economy of FAACF at both design and off-design conditions is comprehensively studied. The internal flow mechanism of efficient operation is analyzed, which reveals the more stable flow state inside CF impellers at off-design conditions. By comparing with the traditional inlet guide vanes CF (IGVCF), the application of the FAA improves the energy efficiency of the CF system significantly. A wider high-efficiency range is obtained, which is superior to the IGVCF. The numerical results effectively reveal the mechanisms by which flow loss occurs in the FAACF at the outlet of blades. In particular, the energy-saving rate of the G4-73-11 type CF system based on the FAA can reach 20.4 % when the relative flow ratio decreases to 74 %, which proves the positive adjustment potential of energy efficiency and indicates great energy-saving benefits of the FAA application in the CF system.