Dr Xueliang Zhu

A comprehensive understanding of the dynamic processes in sonochemical reactions is essential for providing theoretical support and practical guidance in ultrasonic industrial applications. The influence of acoustic factors (frequency and pressure amplitude) and external parameters (liquid height) on sonochemical activity were researched. The phenomenon of sonoluminescence (SL), sonochemiluminescence (SCL) and potassium iodide (KI) dosimetry were investigated at 114 different settings. The settings included electrical loading-power of 10, 20, 30, and 40 W, 10 frequencies ranging from 22 to 2000 kHz, and reactor volumes of 200, 300, and 400 ml. A new area selection image processing technique was used to conduct a systematically quantitative analysis of SL and SCL across a broader frequency range. The sonochemical activity could be categorised into three zones based on the ultrasonic frequency (22 to 2000 kHz): f < 200 kHz, 200 kHz ≤ f ≤ 1000, and 1000 kHz ≤ f ≤ 2000 kHz. The Pearson and Spearman correlation coefficients were used to discuss the correlation between SL, SCL, reactive oxidant species (ROS) and hydrogen peroxide yields. The findings indicate that the influence of liquid height on cavitation activity within the reactor is mostly manifested in the power density. The ultrasonic oxidation capacity (as indicated by the yield of ROS) exhibits a strong positive relationship with SL intensity. A divergence of correlation between SL and I3- yield was observed. There was a lack of correlation between sonochemical activities (e.g. SCL and ROS yield). The poor correlation highlighted the importance of consideration of chemical mechanisms and reaction locations with respect to the collapsing bubble.

Accidental releases of superheated liquids, such as liquefied petroleum or natural gases, are featured by depressurization across the outlet leading to liquid flashing within the upstream container and the downstream jet. In this work, dynamic behaviors of in-tank liquid with phase change throughout depressurized releases and the influence on the primary breakup of flashing jet were studied with an experimental 20 L tank. In-tank parameters (pressure, temperature, and liquid mass) and downstream jet morphology were characterized. A new nondimensional number (ηp), the ratio between the superheat levels of the saturated states corresponding to liquid temperature and pressure, was developed to describe the liquid's thermodynamic state under both release and ambient conditions. A thermodynamics-determined release rate model was established to characterize flow behaviors at the exit. Results showed a strong correlation between the initial ηp0 and key process parameters I (depressurization and release rates): I = aηp0b, where a and b are constants for a particular I. A ηp0-based criterion was derived to characterize in-tank release dynamics and thermodynamics: ηp0 

•Breakup regime of superheated liquid jet under depressurized release is examined.•Both thermal nonequilibrium and mechanical forces are involved as driving effects.•The coupling regime of the two driving effects during depressurization is explored.•Non-flashing, partially flashing, and fully flashing breakup modes are identified.•The interaction of the two driving effects is quantified by dimensionless analysis. Superheated liquid jets disintegrate into numerous droplets when released into the ambient with lower saturated pressure, driven by thermal nonequilibrium induced flashing and the accompanying mechanical forces. Such a phenomenon facilitates fuel atomization in energy utilization while posing a serious threat during accidental releases. In this work, the breakup and droplet formation of superheated liquid jets under depressurized releases were investigated with an experimental 20 L tank. A high-speed camera was utilized to characterize breakup behaviors. The interaction between thermodynamic and mechanical effects during depressurization was discussed based on linear stability analysis and bubble dynamics. Furthermore, the quantitative relationship between the two driving effects under different conditions was established using dimensionless and multiple regression analyses. Results show that the thermodynamic effect increases with the decreased mechanical effect during depressurization because of the increased energy of bubble burst, regardless of the external or internal flashing regime. Non-flashing, partially flashing, and fully flashing breakup modes are identified. The dimensionless and multiple regression analyses show that in addition to thermodynamic (Ja, ρv/ρl, Rp, and ηp) and mechanical (Wev and Oh) effects, the inhibition induced by the cooling effect (Pr and Ec) should not be overlooked. The quantitative expression among them agrees well with experimental data with R2=0.976.

Accidental superheated liquid emissions into the atmosphere yield two-phase releases. The resulting flashing jet, driven by thermal nonequilibrium and mechanical forces, breaks up into massive droplets, fostering beneficial conditions for fire, explosion, and toxic diffusion. In this work, a 20 L tank was built to examine two-phase flow behaviors during depressurized releases of superheated liquids via a high-speed camera and phase Doppler anemometry. Different breakup regimes of flashing jet and dimensionless groups that effectively represent thermodynamic (RpJa) and mechanical (WevOh) driving effects were determined. Based on the interaction between the two effects, quantitative criteria to distinguish different regimes were developed. The accompanying jet characteristics, including jet angle (θ), area fraction (fA), droplet diameter (dSMD), and droplet velocity (ud), and their relationship with jet breakup were revealed. Results show that non-flashing (NFB), partially flashing (PFB), and fully flashing (FFB) breakups coincide with RpJa(WevOh)1/7