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Turbocharging technology is the second milestone in the development of internal combustion engine, which has become an inseparable part of engine technology and has a significant impact on the power and economy of internal combustion engine. The switching valve is a key component in the sequential turbocharging system, which plays a key role in realizing the energy distribution of the parallel turbocharger, the pressure ratio with different engine conditions, the flow regulation and the matching of the full working conditions. In order to explore the influence of different driving torque, gas pressure and temperature on the switching valve of the pressurization system, the steady-state statics and thermal-structural coupling simulation of the switching valve at room temperature were carried out by ANSYS Workbench software. Based on the central composite design method and Kriging method, the size combination and multi-objective response surface optimization model of 15 groups of switching valve design variables are obtained. Under the same conditions, the multi-objective genetic algorithm is used for simulation calculation. The results show that the deformation of the switching valve mainly occurs on the valve plate and the valve shaft under different driving torque and temperature, and it is symmetrically distributed. The distribution of deformation, stress, contact pressure and friction stress of the switching valve under different driving torques are the same. With the increase of driving torque and temperature, the deformation, stress, contact pressure and friction stress of the switching valve increase gradually, and the temperature effect is the most obvious. Compared with the original design size, the optimized structure size can effectively reduce the contact pressure of the switching valve and significantly improve the service life of the switching valve. [ABSTRACT FROM AUTHOR]

In this study,16 kinds of priority PAHs listed by US Environmental Protection Agency (USEPA) were selected as research objects.Ten soil samples collected from a coal fired power plant in southwest of China were analyzed by gas chromatography-mass spectrometry (GC-MS) to determine the contents of PAHs.Based on the analysis of the characteristics of PAHs and its variation,the source of soil PAHs in coal fired power plant was determined by the method of pollutant source analysis.The results showed that 16 PAHs were detected in the soil of the plant,and the contents of 16 PAHs were 4 706~12 175 μg/kg.Average content of PAHs were 7 436 μg/kg.Compared with other regions in China and abroad,the PAHs in the soil of the power plant are seriously polluted.The content of PAHs in soil showed the trend of decreasing firstly and then increasing with the increase of distance in general.The content of PAHs increased sharply at the sampling point of 600 m,and the variation of PAHs with different ring number and ∑16PAHs was in good agreement.The variations of contents of ∑16PAHs in different layers of soils were different,but the tendency reduced at first,then increase and then decrease.The content of ∑16PAHs reached the highest at 200 m of sampling sites.The analytical solutions of the ratio method show that the PAHs in the soil of the power plant mainly came from oil source and coal combustion.The results of principal component analysis show that the contribution of PAHs coal combustion source in the soil of power plant is 67.93%,and the contribution of traffic source is 21.74%.

In this study, 16 polycyclic aromatic hydrocarbons (PAHs) optimally controlled by the U.S. Environmental Protection Agency (EPA) were investigated. Three representative coal-fired power plants were selected as the research areas in Bijie, Guizhou Province, and 24 soil samples were collected totally from power plants at different depths and at different distances from the point pollution sources (plants). The physicochemical properties and microbial characteristics of the soil from the three power plants were also studied. The results showed that 16 PAHs were detected in all soils of the three power plants, with total concentrations ranging from 0.2 to 12.2 mg kg−1, and that PAHs in the soils were mainly 2, 3 rings with percentages ranging from 42% to 82%. The proportions of low molecular weight (LMW) PAHs were higher near the contaminated plants. Moreover, since they were easily dispersed further away with atmospheric transfer, the proportions of lighter LMW PAHs were also higher far from the point source, while the proportions of heavier high molecular weight (HMW) PAHs were higher at some distance from the point source. In addition, the distribution patterns of PAHs in the soil at different depths were slightly different because the microbial activity in the surface soil at each sampling site was greater than that in the deeper soil, and the leaching behavior of each compound was different. Finally, based on the principal component analysis (PCA) method, coal combustion is not the only source of PAHs in soils from power plants, and vehicle emissions cannot be negligible. [ABSTRACT FROM AUTHOR]