The unstable cavitation flow and the dynamic characteristics of oil-gas multiphase pumps usually lead to vibration, noise, and even pump damage. The multiphase flow mixture model and the full cavitation model were used to simulate the transient flow and dynamic features of the pump. The results show that cavitation changes the inflow conditions, aggregates the unstable flow, and generates large pressure pulsations. It also accelerates the variation frequency of axial force and intensifies the uneven distributions of internal flow and circumferential pressure. Both the radial force on the impeller and its variation amplitude are enlarged. Understanding the characteristics of unsteady excitation induced by cavitation can provide references for studying the mechanism of vibration and noise in multiphase pumps.

The flow inside axial-flow type multi-phase pumps is unstable at the conditions of high-speed and high gas volume fractions. The transient dynamic characteristics induced by the unstable flow will lead to pump vibration. Using the standard k–ε turbulence model, the standard wall equation, and the structured grid division technology, the transient dynamic characteristics of the pump at different gas volume fractions were computed by the SIMPLEC algorithm. The axial force and radial force on the pump were calculated by applying integral to the surface area of the computational domain. The results show that the pressurizing performance of the impeller degrades, the dynamic reaction on the blades decreases, while the force acting on the hub increases with the increasing of gas volume fractions. If the gas volume fraction reaches to a certain value, the direction of axial force on the multi-phase pump will change. The radial forces on the first- and last-stage impellers are non-uniformly distributed, and the pressure fluctuation is obvious, while the radial forces on the second-stage impeller and guide vanes are uniformly distributed, and the fluctuation amplitude is small. With the increasing of gas volume fractions, the radial forces on various components decrease gradually.

With the rapid development of the takeout food industry in recent years, the amount of non-degradable wastes such as packing boxes and plastic bags are increasing day by day, which leads to severe waste of resources and pollution of environment. How to deal with the takeout packaging wastes have become a new problem of online ordering and also an important subject of social sustainable development. The construction of a recycling industry chain is an important measure to achieve the recycling of takeout packaging wastes. But this process involves many stakeholders, such as the government, takeout enterprises, package manufacturers and consumers. The cognition and decision of these stakeholders play a decisive role in the construction of the recycling industry chain. An evolutionary game model was established to analyze the effects of different decision behaviours of stakeholders on the construction of the recycling industry chain. And then the MATLAB software was used to dynamically simulate the game system. The results show that in the absence of government intervention, the proportion of the initial decision of consumers and enterprises determines whether the evolutionary game system can converge to the ideal state or not, meanwhile the consumers and enterprises have benign interaction effect in the process of constructing the recycling industry chain; in the case of government intervention, the evolution results of the game system will always reach to the ideal state, and the evolution speed is greatly increased. In the end, the countermeasures and suggestions to optimize the decision behaviours of various stakeholders were provided from the perspective of the government behaviour.

With the use of RNG k-ε turbulence model, SIMPLEC algorithm and CFD software, the turbulent flow in an axial flow impeller was numerically simulated in the clear water (single-phase) and the sandy water (solid-liquid two-phase) conditions. The distributions of solid concentration, velocity and pressure on the impeller of an axial flow pump were analyzed at the same particle diameter but different volume concentrations in sandy water. And these distributions were comparatively analyzed under the clear water and the sandy water conditions. According to the simulation results, the axial pump impeller will be damaged more easily and quickly in sandy water than in clear water. And the area more prone to damage on the axial flow impeller is predicated. The predicted vulnerable parts in an axial flow impeller are consistent with that in actual projects. This study shows that the numerical simulation results are the same as the actual situation, and it has guiding significance for the wear design of the axial flow pump. DOI: http://dx.doi.org/10.5755/j01.mech.24.3.13854