Research On Generation Mechanism Of Low Frequency Noise Radiated From Heat Recovery Steam Generator

With the widely application of gas-steam combined cycle power plant, the noise control of the boundary noise has become a hotspot in the research field of industrial noise. Current research focus on optimizing the layout of the whole power plant and using sound barrier and sound insulation cover to isolate the sound source of the power plant. The Heat Recovery Steam Generator(HRSG) of power plant is the main object of noise control due to its large acoustic radiation area and high stack. However, researches on the mechanism of low frequency noise radiated from HRSG are relatively few, and the conclusions are not consistent. This study would investigate the sound source identification method of HRSG and the simulation method of the vortex noise among heat exchanger tubes.On the basis of measurement of the combined cycle generator, a sound source identification method combining on-site measurement with numerical simulation has been adopted. Sound transmission loss of the wall and the cavity was calculated to estimate the noise in HRSG and the gas-turbine exhaust noise respectively. Spectra analysis was applied to identify the main sound source in HRSG.Adopting proper simplification of the modeling process, numerical simulation was carried out to analyze the non-stationary flow field and sound field in the heat exchanger tube array to investigate the feature of the vortex noise with hybrid computation method, which was comprised of CFD method based on Large Eddy Simulation(LES) and acoustic analogy by using Ffowcs Williams-Hawkings equation. The correctness of the sound source identification and the effectiveness of this method was verified by comparing the simulation results with the measurement.In order to control the low frequency noise in HRSG, a double-sided perforated sound absorption barrier and a mixed-parameter double-sided perforated plate muffler was designed.The geometry of the heat exchange tube was optimized.As shown in the research, the vortex noise of heat exchanger tube array is the main sound source of low frequency noise in HRSG. The identification method combining on-site measurement with numerical simulation is fast and effective. Simplification process and numerical methods are proper to accurately simulate the vortex noise and applicable to engineering practice. More targeted methods can be used for noise reduction of HRSG according to the research results.