Centrifugal pumps as turbines (PATs) are widely used in chemical engineering for recycling the abundant energy from high-pressure fluid. The operation of PATs is significantly affected by their upstream conditions, which are not steady (i.e., with a constant flow rate) in reality, thus, research on the flow mechanism of PATs under transient conditions should be considered of higher importance. In this study, a numerical model of a PAT was developed by employing the sliding mesh method to describe turbine rotation, and a user-defined function (UDF) for characterizing transient flow conditions. Corresponding experiments were also conducted to provide validation results for the simulation, and the simulation results agreed well with the experimental outcomes. The instantaneous characteristic curves under the current working conditions were obtained for different transient flow rates. The results show that the turbine’s efficiency is significantly affected by transient flow conditions. In particular, a rapid increase (large time derivative) of flow rate results in a large energy dissipation at the turbine outlet, and therefore, the turbine efficiency decreases. In addition, as the flow rate increases, the hydrodynamic force on the impeller, and the pressure fluctuation amplitude in the volute first decrease and then increase, reaching the minimum near the design flow rate. The current study provides a reliable and precise approach for the estimation of hydrodynamic performance of fluid machinery under transient flow conditions.

In coal-fired power plants, most of the working fluids used in a mid–low-temperature flue gas waste heat recovery system (FGWHRS) are low-temperature boiler supply air or condensate water in the flue gas condenser. This is prone to cause low-temperature corrosion, as the system temperature is lower than the acid dew point of the flue gas. In this study, an experimental apparatus was set up at the entrance of the desulfurization tower of a 330 MW unit in Xinjiang, China, which uses the technology of high-temperature boiler feed water (above 80 °C) to recover the waste heat of mid–low-temperature flue gas. The heat exchange performance of the mid–low-temperature FGWHRS was evaluated under different working conditions, and the optimal input parameters of the system for each considered working condition are given based on the analysis. It was found that the low-temperature corrosion in the system could be avoided using this technology. To eliminate low-temperature corrosion, the lowest temperature for the inlet water was predicted to be 69 °C in our study via curve fitting based on the experimental data. The results could provide a theoretical basis and engineering guidance for determining the best heat recovery strategy of mid–low-temperature FGWHRS.

Rotor spinning is an open-end spinning method that uses air as the medium to transform the fibers into yarn. Nowadays, the properties of its final product—yarn—such as yarn strength and yarn twist, are not satisfied due to the fiber morphology, which greatly depends on the distribution of the massive fibers in the rotor spinning unit (RSU). In this paper, theoretical analysis is given to describe the trajectory of fiber on the slide wall. A numerical study is performed with the massive fibers being simplified into granules to study their distribution characteristics in the RSU. According to our numerical results, the forming process of the fibrous ring is discussed and the effects of two variables, the rotor speed and the angle of the slide wall, on the distribution of fiber granules were also studied. The simulation results indicate that the fiber granules are not evenly distributed during their transport in the fiber transport channel (FTC) and they tend to accumulate on the upper and lower edge of the FTC. The distribution of fiber granules in the groove (fibrous rings) is closely related to the rotor speed. The higher the rotor speed, the longer and thinner the fibrous ring. The distribution of fiber granules on the slide wall is related to the angle of the slide wall such that a smaller angle leads to a scattered distribution on the slide wall, while a larger angle tends to bring a concentrated one. The simulation results show good agreements with our experimental results.

In this study, a Eulerian Wall Film (EWF) model and a discrete phase model (DPM) are applied to simulate the phenomenon of droplet re-entrainment in a baffle demister. The primary objective was to design a new hook plate and evaluate its influence on the performance. The results show that the phenomenon of droplet re-entrainment occurs owing to the separation and stripping of the liquid film at the corner of the demister. Moreover, the liquid film strips at the areas where the local velocity is quite high near the wall of the demister. With the installation of the hook, the removal efficiency increased from 68.4% to 87.2% at 3 m/s inlet velocity. When the inlet velocity was increased to 6 m/s, the removal efficiency reached 96.7%, indicating that the existence of the hook plate further improved the efficiency of the demister, whereas the pressure loss of the system also increased.

This paper designs flow-through components based on empirical formulas. It examines the solid–liquid two-phase flow characteristics of coarse particles in a novel deep-sea multistage mining pump using a Computational Fluid Dynamics-Discrete Element Method model. The flow characteristics and variation patterns of the cascade end faces between different stages under various particle sizes are investigated, along with the local flow and particle motion characteristics within the flow channels. Additionally, the effect of varying coarse particle sizes on the wear behavior of the flow-through components is examined. This study contributes to reducing wear during particle transport, improving the efficiency and stability of coarse particle transport, and supporting the development of solid–liquid two-phase flow theory for coarse particles.

The air-jet loom is widely used in the textile industry and the main nozzle is one of its key components. In this paper, the influence of some parameters, including the input air pressure and the structure of nozzle core and its internal diameter, on the internal flow field of the main nozzle is analyzed. Then the optimized structure of the main nozzle is proposed from the perspective of fluid dynamics. In the present simulations, the realizable $\text{k}-\varepsilon$ model is applied to model the internal flow field of the main nozzle. The results show that the velocity in the annular throat reaches supersonic. Moreover, the pressure at the end of the nozzle core is the lowest in the main nozzle. It is also shown that the input air pressure has little effect on the axis velocity in Zone B, but on the other hand, has a great influence on the near-wall velocity field and the axis velocity in Zone C. In addition, an optimized structure of the nozzle core is proposed in this paper. It is found that with the proposed structure, the velocity boundary layer near the wall of Zone B in the accelerating tube can be well improved, and rapid diffusion of airflow in this area can be avoided. These help increase the moving speed of the weft yarn. Last but not least, we also show that decreasing of the internal diameter of the nozzle core improves the axis velocity of the weft accelerating tube. However, it brings a stronger turbulence at the same time.