Experimental investigation on the second dominant frequency of supersonic steam jet condensation oscillation and its propagation characteristic

Highlights: • The second dominant frequency is generated by detached steam bubble oscillation. • The frequency value of supersonic steam increases with the design pressure ratio. • Experimental correlation and theoretical calculation could obtain its frequency. • Energy amplitude rises from low to high design pressure ratio with steam mass flux. • Energy propagation characteristic of second dominant frequency is derived. - Abstract: Submerged steam jet condensation is widely applied in the industry, and the condensation oscillation during the condensation process is highly related to the safe operation of devices. The first dominant frequency has been frequently studied; thus this study focuses on the characteristic of the second dominant frequency of supersonic steam condensation oscillation. Results show that the second dominant frequency is generated by the oscillation of the detached steam bubble. The frequency value of the supersonic steam is lower than that of the sonic steam, and increases with the design pressure ratio. Two different methods, namely, experimental correlation and theoretical calculation, are proposed to obtain the second dominant frequency. Moreover, its propagation characteristic is investigated under different operation conditions. An energy peak, which corresponds to the position where the steam bubble separates, always appears. The energy amplitude peaks at a low design pressure ratio when the steam mass flux is not larger than 600 kg·m⁻²·s⁻¹, and it peaks at a high design pressure ratio when the steam mass flux increases. A theoretical method is established to obtain the second dominant frequency energy distribution, and its effectiveness is verified against experimental results. Furthermore, owing to the barrier effect of steam plume, the upstream deviation is slightly higher than the downstream deviation.