Pressure load fluctuations of sector plates in a tri-sector rotary air preheater

Abstract

A tri-sector rotary air preheater installed in a 350 MW generating unit was investigated to clarify the fluctuating pressure loads acting on the sector plates and their influence on sealing performance. A three-dimensional transient computational fluid dynamics model was developed using an anisotropic porous-medium representation of the regenerative matrix, the shear stress transport k – ω turbulence model and a sliding-mesh method. Pressure distributions were analysed under the 350 MW condition, while pressure time histories and peak-to-trough amplitudes were compared at 350, 300 and 280 MW. The results show that the fluctuations arise from the coupling between inter-passage pressure differences and periodic rotor-compartment switching. The dominant fluctuation period is approximately 1.25 s and remains nearly unchanged with unit load. The primary-air-side sector plate exhibits the largest fluctuation amplitude, whereas the secondary-air-side sector plate shows the smallest amplitude and may temporarily experience negative area-weighted average gauge pressure. The time-averaged simulated outlet-duct static pressures agree with field measurements within a maximum relative error of 6.91%. These results provide pressure-load information for sealing optimisation and air-leakage-reduction design in rotary air preheaters.