Hui Zhao

High-pressure differential liquid-solid two-phase flow is widely used in the chemical industry, energy, and power fields. In this study, a multistage segmental throttling orifice pressure-reducing pipe was developed to address the bridging risk and erosion challenges associated with batch slag discharge in coal gasification. Ultrasonic technology was used to evaluate the erosion distribution inside the pipe and to establish the erosion mechanism. The research results demonstrate a rapid increase in the pressure drop of the pressure-reducing pipe with a rising flow rate, indicating its high-pressure drop characteristics. However, after the experiment was conducted for 30 h, the pipe failed at 5.56 m3/h operating conditions and the pressure drop performance of the pressure-reducing pipe was significantly decreased as erosion time increased. The pipe structure experiences severe deformation, expansion, and formation of pits due to impact, which exacerbated erosion and led to more complex erosion behavior.

A series of novel phenomena emerges when the coaxial airflow rapidly blows over the quasi-solid paste jet surface, leading to the direct solid-like exfoliation breakup of protrusions on the side face and the liquid-like tensile breakup on the end face. The experimental findings unequivocally demonstrate that the vertical protrusion formation on the side face under high gas velocity serves as a precursor to the subsequent exfoliation breakup, while the tensile breakup is a consequence of axial elongation of the protrusions at the junction between the side and end faces. A crucial step in interpreting the exfoliation breakup is to discern the individual force competition at the jet interface. As gas velocity increases, the radial shear force maintains stronger than the axial drag force and becomes the dominant factor. After the formation of protrusions, the airflow component directly impacts the upper surface of the protrusion in a vertical manner and causes it to fracture similar to the cutting off of a rod-shaped solid. During tensile breakup, the protrusions on the end face develop into liquid threads, which rotate and elongate under axial airflow drag and reflux, ultimately leading to the breakup. Mathematical force models are established to elucidate this intriguing phenomenon observed in the experiments. This study of quasi-solid pastes in airflow will expand the new understanding of the interaction between gas, liquid, and solid states.

The addition of aluminum particles to a gel propellant has garnered attention through its potential for enhancing fuel properties. In order to enhance the energy performance of gel propellants, it is imperative to prepare gel propellants with high concentrations of aluminum. However, high-concentration aluminum-containing gels encounter two challenges. First, the combustion process leads to the agglomeration of aluminum particles, resulting in incomplete combustion. Additionally, elevated concentrations of aluminum particles increase the viscosity of the gel, impeding its atomization process and, subsequently, affecting combustion efficiency. These aforementioned issues pose practical obstacles for the application of high-concentration aluminum-containing gel propellants. In this research, a high-concentration aluminum-containing gel formulation was supplemented with nanocarbon powder. By investigating the impact of nanocarbon on various properties of the gel, its potential for addressing the above issues was analyzed. The investigation into the combustion performance of aluminum-containing gel blended with carbon powder revealed that the addition of 10 wt % nanocarbon powder to the gel system leads to a significant increase in the volumetric calorific value of the gel propellant by 21.21%. This enhancement not only improves the energy performance but also addresses the issue of incomplete combustion associated with aluminum. The rheology experiments conducted on gels demonstrate that the addition of nanocarbon powder results in an increased viscosity of the gel at lower shear rates, thereby enhancing its ability to withstand external disturbances during storage. Furthermore, this incorporation also enhances the gel's shear thinning properties, leading to a significant reduction in viscosity at higher shear rates and facilitating easier atomization of the gel system. In summary, the incorporation of nanocarbon powder can optimize the storage, atomization, and combustion processes of the gel, offering a straightforward and efficient approach to enhance the practical performance of metallized gel propellants.

With the improvement of chip performance, the requirements for cleaning the surface of silicon wafers are becoming higher. However, due to equipment and technology, it is difficult to observe the complex motion processes of particles at the microscopic scale. In this paper, an in situ dynamic visualization experiment on the cleaning of Polystyrene Latex (PSL) on the surface of silicon wafers is carried out by using a high-speed camera and image processing software. The mechanical behavior of PSL particles in fluid was investigated on a microscopic scale, and the trajectory and force of the polystyrene particles on the surface of the wafers were visualized, which provided a new perspective for understanding the complex cleaning process. Theoretical models were developed to explain the motion characteristics of the particles by calculating parameters such as van der Waals force, surface tension, and trailing force, and these models provide a theoretical basis for optimizing the cleaning process. There are four particle motion modes in the fluid: (1) interface capture, where the particles on the surface of silicon wafer are trapped by gas–liquid interface under surface tension; (2) particle collision, where the particles captured by the water film collide with the particles on the wafer surface to make the latter leave the silicon wafer; (3) jump attachment, where the particles jump and attach to the surface of the particle group under the action of lift; and (4) wall surface movement, where the particles start up under the action of water flow and then leave the silicon wafer quickly.

Jet entrainment has a significant impact on the performance and longevity of coaxial atomizers. This study aims to investigate the entrainment characteristics of fluids with different rheological properties under coaxial gas–liquid jets through rheological experiments and high-speed flow visualization techniques. As the airflow velocity increases, the liquid jet exhibits non-entrained, entrained, and over-entrained modes. We found that only in the over-entrained mode does the entrained fluid come into contact with the nozzle outlet. The transition conditions for each mode are determined and plotted in a dimensionless map of We-Oh. A “bulge” structure on the surface of the liquid column at the nozzle outlet was observed within a specific gas velocity range, and its formation mechanism and characteristics were investigated. Theoretical models for two critical gas velocities were obtained by analyzing “initial entrainment” and “full entrainment” states in recirculation zones using total pressure conservation theory. The proposed model demonstrates its applicability to three distinct fluid media, namely, guar gum gel, glycerol, and water, exhibiting excellent agreement with the corresponding experimental results.