To ensure proper preservation, seamless capsules must be completely dried, which is achieved through a process in the drum. However, it is difficult to observe the changes in the capsules during the drying process in real-time. To address this, FLUENT and DEM coupled calculations are utilized to simulate the heat and mass transfer of the capsules during drying. The results demonstrate that the coupled model accurately predicts the drying time of the capsules under certain conditions, capturing the movement and interaction of particles and flow field inside the drum. During the drying process, air is unable to effectively enter the drum, resulting in the ineffective formation of convection in the drying environment and reduced drying efficiency. Based on the simulation results, subsequent optimization of the movement of the capsules in the drum, design of the air inlet, and improvement of convective mass transfer efficiency can be achieved, leading to an optimized drying process through adjustments to the drying conditions.

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To elucidate the relationship between the gas-liquid two-phase flow pattern and performance in a centrifugal pump, this study investigates the energy and transient characteristics of the pump under various inlet gas volume fraction (IGVF) and liquid flow rate (LFR) through visualization testing. The results indicate that at the nominal flow rate, the critical gas content for transitioning between different flow patterns increases with the LFR. At lower flow rate, the transition from gas pocket flow (GPF) to gas-liquid separation flow (GLSF) shows the most significant gradient change in critical gas content. At higher flow rate, the transition from bubbly flow (BF) to GPF exhibits the most significant gradient change in critical gas content. When the flow regime is BF at the nominal flow rate, additional gas entry leads to a decrease in pump head and efficiency, accompanied by periodic changes in pressure fluctuation. When the flow pattern shifts to GPF, additional gas entry similarly decreases pump head and efficiency. Notably, pump head decreases significantly at the IGVF of 3.1% and 3.9%, with reductions of 52.8% and 69.0%, respectively. Unlike BF, pressure fluctuation does not exhibit apparent periodicity. Under the condition of IGVF = 1.0%, as the flow regime transitions from BF to GPF, increasing the LFR results in a decrease in pump head and an increase in efficiency, along with an increase in the peak value of pressure fluctuation. When the flow regime in the pump is BF, both pump head and efficiency decrease with increasing LFR, leading to a decrease in the peak value of pressure fluctuation. Notably, when the LFR increases to 35 m³/h, the continuous increase in IGVF results in a maximum reduction in pump head and efficiency of 35.56% and 20.04%, respectively.

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Centrifugal pumps are the core pressure boosting unit of urban water supply systems. With the proposal of the dual carbon strategy, there is an urgent need to reduce the energy consumption of centrifugal pumps in water supply systems. Therefore, we use a control method based on the line of proportional pressure, which effectively reduces the head of centrifugal pumps under low flow conditions and achieves a high energy saving of the system. Moreover, we set up a water supply testing system, and apply two control methods, including the constant pressure method and the proportional pressure control method, to regulate the pump and valve. After that, we compared and analysed the comprehensive energy consumption of the system under different control strategies. The results illustrate that proportional pressure control can save more than 58% energy in theory at flow of 1.3 m3/h, and the system controllable flow range is up of 1.3 m3/h. The proportional pressure control has wider high efficiency working flow range than the constant pressure control, it can achieve a higher pump efficiency at minimum flow of 2.5 m3/h, while the constant pressure control is at minimum flow of 3.4 m3/h.

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In this study, cavitation tests and cavitation CFD analysis were conducted to elucidate the mechanism of head reduction when cavitation occurs in a closed-type single blade centrifugal pump. In addition, the hydraulic loss during the cavitation process was evaluated, and the relationship with the vortex structure in the impeller in the point of no pressure change and at the head drop point was investigated. As a result, the vortex generated in the impeller was larger at the head drop point than in the point of no pressure change, and impeller loss, in particular, increased. Vortices are generated in the impeller at the head drop point due to cavitation on the shroud side of suction surface near the blade inlet. Cavitation and the vortices generated due to cavitation were found to be the cause of increased impeller loss. As a result, it is possible to effectively improve the cavitation performance of the pump by suppressing the vortices that cause head reduction and the cavitation that induce these vortices.

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An underground turbine generator is a safe and reliable power supply equipment of high precision, high reliability, and long life in mine and other mine drilling measurement instruments. Because of the current problems of low output power and high energy loss of underground turbine generators in general, a set of coalmine underground turbine generators is initially designed by modeling the turbine with CREO software and numerical calculation with ANSYS CFX software, the optimal hydraulic model was determined by considering multiple factors in rotor and stator geometry size, taking the output power as the objective function and optimizing it by using orthogonal experimental method. By comparing the downhole turbine generator model before and after optimization, it was found that the optimized flow line distribution and pressure distribution were well improved. At the same time, the work capacity of the drilling fluid on the turbine was improved. Among them, the output power is positively correlated with the hub ratio, stator inlet angle, and distance between the stator and rotor. On the contrary, it negatively correlated with the rotor number. This conclusion has important guiding significance for optimizing the hydraulic performance of underground turbine generators.

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The strong noise produced by centrifugal pump during operation will do harm to the health of workers and pump group. In order to realize the low noise operation of centrifugal pump, researchers add bionic structure to the blade to realize the centrifugal pump noise reduction. At present, in the research of centrifugal pump noise reduction, pit bionic structure and sawtooth bionic structure are the most reprlesentative. Pit structure is for broadband noise reduction, sawtooth structure is for discrete noise reduction. From a macro perspective, if the two bionic structures are coupled, it is likely to bring greater noise reduction. Therefore, in this paper, sawtooth structure is installed on the trailing edge of the pitted blade, and the internal flow field and sound field of the bionic blade are studied, and the influence of the coupling bionic structure on the external characteristics, acoustic amplitude-frequency characteristics and flow field structure of the centrifugal pump is analyzed. The results show that the coupling bionic structure is greatly affected by the sawtooth structure, which makes the pit structure lose the original broadband noise reduction effect, and the two noise reduction mechanisms are different, which makes the pit and sawtooth structure incompatible.

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