Numerical and Experimental Study on Mechanism of Low Frequency Noise from Heat Recovery Steam Generator

The low frequency noise from heat recovery steam generator (HRSG) makes dominant contribution to the noise on the boundary of plant, which generation mechanism is investigated in this presentation. The non-stationary flow field and aeroacoustic noise is studied with hybrid numerical simulation, which is comprised of CFD method based on Large Eddy Simulation (LES) and acoustic analogy by using Ffowcs Williams-Hawkings equation. Models of cylindrical tube, fin-tube and tube array are established respectively to investigate the feature of vortex noise. The results of numerical simulation are compared with the acoustic intensities measured at the site. It can been understood from the simulation that the flow passing through the heat exchanger tube will induce vortex shedding, which results in the low frequency noise in HRSG. The vortex noise of a cylindrical tube lead to the obvious characteristic tone frequency as same as the vortex shedding frequency, but the spiral fin reduces the characteristic frequency and sound level. For the tube array of heat exchanger, due to the enhanced interaction of the flow field among tubes, the vortex noise is narrowband noise with some bandwidth. More targeted methods can be used for noise reduction of HRSG according to the research results.