Applied Mechanics and Materials Vol. 700

Abstract: Haze-fog has been a severe pollution weather phenomenon in China due to a large number of emissions of pollutants with the rapid development of economy. The areas burst haze are usually coincidence with high density of electricity transmission line corridor or power load areas, and so the pollution flashover accidents happen frequently. In this paper the haze pollution situations and factors contributing to haze are introduced, and the mechanisms of haze inducing and aggravating the pollution flashover accidents are explained by analyzing the temporal and spatial distribution of PM2.5 and size characteristics of dust deposited transmission. Moreover, the influences of haze on power transmission and transformation equipment external insulation are discussed with combining the simulation pollution flashover experiments of high conductivity fog.

Abstract: The numerical simulation of cavitation flow field in a Francis turbine runner with attached blades was conducted based on the no-slip mixture model in the Euler approach and the Singhal cavitation model. The RNG model after correcting viscosity and the pressure correction algorithm (SIMPLE) were supplemented. The distributions of the water-vapor volume fraction under non-design conditions were obtained. The results show that the method based on two-phase mixture model can be used to simulate the position and degree of cavitation flow in Francis turbine.

Abstract: In order to investigate the silt abrasion of modified trailing edge of stay vane in Francis turbine, the numerical simulation of trailing edge with different geometries were carried out based on the solid-liquid two-phase flow by means of Computation Fluid Dynamics. The results show that low solid volume fraction distributes on the chamfered surface of trailing edge, and high solid volume fraction distributes on the end of oblique surface. The smaller the modified angle is, the larger the distribution area of high solid volume fraction is, which show the trailing edge with smaller oblique angle may suffer from silt abrasion. Therefore, in order to solve the vibration caused by Karman vortex the trailing edge has to be sharpened, the oblique angle of trailing edge should not be too small. At end of trailing edge needs to ensure a certain thickness, especially the trailing edge near the lower ring can be thicker, which can meet the anti-abrasion requirements.

Abstract: According to the CFD numerical simulation of hydraulic turbine internal flow and simulation calculation of vortex and cavitation of draft tube, and in the three dimensional modeling and analysis of the draft tube elbow is found that commonly modeling methods are tedious process, there is more deviations, not conducive to modify the part size and flow over a smooth. This article proposes a projective modeling method to avoid some drawbacks of traditional methods; the modeling process is convenient and concise, easy to modify the local size, flow more smoothly, and achieve more accurate simulation process.

Abstract: In order to study the influence of intake temperature on the combustion characteristics of HCCI engine fueled with n-butanol, the 2nd cylinder of a water-cooled, naturally aspirated and double-cylinders diesel engine was converted into HCCI combustion mode. The cylinder pressure (P), rate of pressure rise (dp/dφ), heat release rate (dQ/dφ) and cycle-to-cycle variations (CCV) were compared and analyzed by bench tests under the conditions with different intake temperatures at engine speed of 1000r/min, excess air coefficient of 2.5. The experiment results show that the peak pressure (P_max), the peak rate of pressure rise and maximum heat release rate tend to rise and the peak arrives in advance with the increase of intake temperature. As the intake temperature rises, the coefficient of variation for P_max reduces and combustion stability increases.

Abstract: In this research, the traction inverter of coal winning machine installed on the plate that matched with water cooling, each plate cooled two inverters. Also, the inverter controlled by four quadrants. After calculated the conducting losses and the switching losses of the IGBT module, we analyzed the factors affecting the heat dissipation in the finite element analysis software CFX, the factors include the installation position of IGBT module, the thickness of inverter baseplate and different water flow rate. Comparing with the experiment results, verify the validity and practicability of the presented research method of heat dissipation system.

Abstract: As the city develops radiady, the natural gas is widely used nealy in every filed of people’s lives. During the pressure regulation, the phenomenon of ice jam, which can affect the normal utilization, happens. Heater can be regarded as one of the most important measures that prevents pipe from freezing occurring due to temperature drop caused by pressure regulation. Low-temperature radiant heater with tight structure is specifically designed for gad gate station. The heat transfer process of the gate station is analyzed. In the meantime, the mathematical model of radiant heater, which could be fitted for the gate station, is erected. At the same time, the influence of heat exchange size, radiant panel size and radiant efficiency, brought by tube are discussed. The result shows that the tube type of radiant heater has a greatest performance. Considering the tubes with compact structure, taking tube type of radiant heater as the heater used in gate station is the optimal decision. The analysis combined in this paper is the foundation to choose the heater of gate station.

Abstract: LNG (Liquefied Natural Gas) submerged combustion vaporiser is applied to convert Liquefied natural gas to gas phase natural gas through using the hot combustion gas generated from submerged combustion. This paper investigated the vaporisation and heat transfer process of a single horizontal tube, a simplified model, to simulate the heat transfer of circular tube heat exchanger used in LNG submerged combustion vaporiser. This work provides a useful computer model for the design of heat exchanger used in LNG submerged combustion vaporiser. The overall heat transfer and vaporisation process of the tube was separated into single-phase liquid, two-phase mixture and single-phase vapour heat transfer regions for calculation and analysis. Through development of a dedicated computer model, a parametric study was carried out to analyse the effects of geometrical size and operating conditions on inner surface convective heat transfer of tube. The results of study suggested that the preferable tube surface temperature for design was found between 280 K and 288 K in order to avoid frost deposition. The minimum tube length required for the overall vaporisation is predicted to be about 16 m when the inner tube diameter set between 0.24 m and 0.28 m.

Abstract: The paper gives a brief introduction of the permanent magnet synchronous motor (PMSM). The author gives the mathematical model under the simplified conditions and the PMSM rotor and stator impedance matrix. Besides, the author used AMESim to build a synchronous motor model on the basic of hysteresis current control strategy and set the parameters. A simulation was carried out and advantages and disadvantages of hysteresis current control strategy were analyzed.

Abstract: In this paper, a new system which absorbs the water vapor in flue gas of natural gas fired boiler (NGFB) by desiccant solution is introduced. This system can recover the latent heat of water vapor and improve the thermal efficiency of the NGFB significantly. In the theoretical analysis, the packed tower which is the most important equipment of solution circulation heat recovery system (SCHRS) can be designed by establishing a mathematical model. Based on the recovery efficiency of water vapor by desiccant solution absorption, the thermal efficiency analysis of NGFB is discussed, which show that SCHRS has a good application prospect in NGFB waste heat recovery.