Mitigation Method for Pressure Fluctuations Induced by Acoustic Resonance

Multi-stage pumps used for boiler water supply of thermal power plants have large capacity and pressure. Fluctuations may cause vibration and noise in pumps, piping systems, and surrounding structures. Lots of studies have been conducted on the pressure fluctuation phenomenon of turbopump piping systems. Some of the factors are the rotor-stator interaction, a resonance between the fluid in the pipe and, excitation source and resonance between structure and pump operation. Besides, studies on mitigation method for pressure fluctuations have been conducted. Inserting orifice to add damping, adjusting the length of pipe to change resonance frequency and, installing resonator to mitigate a specific frequency. However, these studies have not quantified the solution to the pressure fluctuations, so further research is needed to elucidate the causes and establish countermeasures quantitatively. In this study, pressure fluctuations due to acoustic resonance are generated by using a speaker. An orifice, a bent tube, and a branch pipe are installed at the node and antinode of the secondary pressure standing wave in the pipe, and the effects on the standing wave are observed. Moreover, the mitigation method for the pressure standing wave is established by performing a sweep test. Numerical analysis is conducted by AMESim to validate the results of experiment. It is clarified that by inserting the orifice at the appropriate position of a standing wave, pressure fluctuations are mitigated. In the case of branch pipe, pressure fluctuations are effectively mitigated by inserting it having appropriate pipe length and boundary condition.