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Rotary pressure exchanger (RPE) is a kind of liquid energy recovery equipment based on the positive-displacement principle. The key component of RPE is rotor with plurality of ducts around axis. The liquid piston formed in ducts transfers energy and controls mixing rate. The theoretical model of mass transportation in ducts during mixing process was set up based on experiments. By numerical simulation, the formation process of liquid piston is discussed, and the main factors affecting the liquid piston performance are analyzed. The computation results illustrate that flow rate and rotary speed have more effects on the formation and movement of liquid piston. And the liquid piston has the capability of self-adjust with the variation of flow rate and rotary speed of rotor, with which the purity of pressurized fluid can be guaranteed and the highest volumetric efficiency of duct can be reached. [ABSTRACT FROM AUTHOR]

A numerical model was built and a series of numerical simulations of methane-air explosions were carried out in a long closed pipe which was 104 mm in inner diameter and 2 400 mm in length. The model was based on the large eddy simulation for turbulence modeling and the premixed combustion for calculating chemical reaction. The simulated pressures and total explosion time were in good agreement with experimental results. It is found that, after ignition, flame darts forward firstly, then the flame speed decreases sharply. Tulip flame appears during explosion and its formation is related to the interaction of vortices in the middle section and near walls. The vortices near walls moves backward after tulip flame, which is an important factor to the transform from laminar to turbulence combustion. The numerical results reveal the characteristics of flame propagation and flow field during gas explosion in such pipe. [ABSTRACT FROM AUTHOR]

As one of the main producers and consumers of pesticides in the world, China has historically used large quantities of organochlorine pesticides, such as DDT and HCH. Rice is a staple food crop in Shanghai, where the Qingpu and Chongming districts are two important rice planting areas. This study detected the residue levels of 24 organochlorine pesticides (OCPs) in rice samples collected from Qingpu and Chongming in Shanghai. The composition and health risk of OCPs in rice samples were investigated. The results revealed that DDTs and HCHs were the main OCPs in rice from the study area. The mean levels of 24 OCPs residues in rice from Qingpu and Chongming were 6.53 ng·g -1 and 4.70 ng·g -1 , respectively. The analyses of all the target compounds met the China National Food Safety Standard. The concentrations of 4,4-DDE and β -HCH were the highest in rice from Qingpu, while 2,4-DDT and β -HCH were the main components in rice from Chongming. Source analysis showed that dicofol and lindane might be still used recently in some areas of Shanghai. The health risk assessment results indicated that there was no obvious risk to human health by eating rice from Shanghai based on the OCPs studied.