Advanced Materials Research Vols. 455-456

Abstract: Simulation of microscale thermo-fluidic transport has attracted considerable attention in recent years owing to rapid advances in nanoscience and nanotechnology. The three-dimensional molecular dynamics simulations are performed for coupling between flow and heat transfer in a nanochannel. Effects of interface wettability, shear rate and wall temperature are discussed. It is found that there exist the relatively immobile solid-like layers adjacent to each solid wall with higher number density. Both slip length and Kapitza length at the solid-liquid interface increase linearly with the increasing wall temperature. The Kapitza length decreases monotonously with the increasing shear rates. The slip length is found to be overestimated by 5.10% to 10.27%, while Kapitza length is overestimated by 8.92% to 19.09% for the solid-solid interaction modeled by the Lennard-Jones potential.

Abstract: The frequency and pressure characteristics of a Helmholtz-type valveless self-excited pulse combustor with continuous supply of fuel and air are investigated in this paper. A theoretical model of combustion is established. In the model, combustion is assumed to take place in a thin flame sheet separating the two zones, and the effects of the continuous gas-supply mode and heat transfer of the tailpipe on the operating characteristics are considered. From the mathematical model, the expressions of frequency and maximum pressure amplitude for the pulse combustor are derived. The results suggest that the frequency decreases with the increase of excess air ratio and tailpipe length, and increases with the heat load. The pressure amplitude increases with the increase of the excess air ratio and heat load, and slightly declines with the increase of the tailpipe length. The experimental data show qualitative agreement with the calculated results.

Abstract: To improve the low-permeability coal seam gas drainage and gas prevention and to seek the methods to improve the permeability of low-permeability coal, the experimental study on supercritical CO₂ on coal was conducted in the laboratory conditions, and the experiment on pseudo-triaxial permeability testing for coal samples, with and without supercritical CO₂, was conducted. The results show that due to the effect of supercritical CO₂ on coal like physi-chemistry, the porosity of coal was changed, which markedly varied the permeability of coal samples before and after the effect of supercritical CO₂; the permeability of the experimented coal samples was significantly higher than before, and average permeability increased by nearly an order of magnitude under the same volume-stress.

Abstract: A mesoporous silica (SBA-15) was used to prepare the Ni/Mo₂C catalysts in order to study the influence of the support on the catalytic performance. The catalysts were characterized by-N₂ adsorption, X-ray diffraction, FT-IR absorption, CO₂-TPD and SEM analysis. The catalytic properties was tested at 800°C, atmospheric pressure, GHSV of 9000 ml³h^-1g^-1 and a CH₄/CO₂ molar ratio of 1. These results suggest that catalytic activity, which is directly related to the incorporation of nickel and molybdenum carbide to the mesoporous silica.

Abstract: The new type wind power yaw reducer has been virtually assembled in Pro/E for the operating conditions of the Megawatt wind power yaw reducer. The planetary gear contact model of the new type wind power yaw reducer has been built to simulate the change of the contact stress in the process of planetary gear operation with the interface of Pro/E and ANSYS. The results show that: the initial maximum contact stress of the meshing planetary gear is 395MPa and the maximum stress in the engagement process is 460MPa, but it is still less than the material yield limit of the planetary gear. The results also show that the fatigue life of the gear teeth is 125,800 times, the cumulative fatigue factor is 0.72501 by analyzing the fatigue loads and 42CrMo’s S-N curve of Megawatt wind power yaw drive planetary gear, so it can meet the design and operation requirements for the Megawatt wind power yaw reducer.

Abstract: .According to the operation condition of megawatt wind turbines yawing reducer, an assembly model of megawatt wind turbines yawing reducer is established, and aiming at different load conditions, the tooth surface of three teeth planetary gear model is analysised with using finite element analysis software-ANSYS ,including three-dimensional nonlinear contact analysis and structural finite element analysis which simulates contact stress of engagement pairs during the operation process of planetary gear. The results indicated that when the torque is M₁=100N·m, the maximum stress on the engagement pairs is 177.584MPa; when the torque is and M₂=300N·m, the maximum stress on the engagement pairs is 329.607MPa, which were less than the yield limit of planetary gear materials, but it can meet the design and operation requirements of planetary gear of megawatt wind turbines yawing reducer.

Abstract: In the construction of thick filling area on expressway soft-foundation, the free pore water in the saturated foundation soil of expressway is seldom discharged immediately, and the excess pore water pressure comes into being, which lead to the delay of the process of soil consolidation, and the lag of stabilization time of settlement and time limit for a project. On the basis of settlement analysis of small non-sand concrete pile composite foundation under the action of anaphase load, optimal design method of the post-processing technology for soft-foundation is researched on the basis of settlement control in this paper. Which provides theoretical basis for the design of small pile composite foundation.

Abstract: The optimal design theory of the post-processing technology of thick filling area is based on the characteristics of small non-sand concrete pile, to research the production and development process of stress and strain of foundation soil in the course of drilling and grouting, and thus to optimize the key technical parameters of the post-processing technology. In this paper, on the basis of the analysis of consolidation process and treatment mechanism of the post-processing under the conditions of saturated soft soil, the research of optimal design of the post-processing technology on the control of consolidation degree and bearing capacity is completed, which is of reference for the design and construction of the post-processing technology.

Abstract: In the two-dimensional experiment of similar material simulation, three-dimensional coordinate data obtained by total station should be conversed to the coordinate system which is concerned in the experiment.When using bursa-wolf model to converse coordinate,the three rotation parameters should be linearized,which will affect the accuracy of coordinate conversion if the three rotation parameters are big.In this paper,it is researched that using an antisymmetric matrix which is consist of three separate parameters to substitute for the three rotation parameters,and then the lodrigues matrix is composed from the antisymmetric matrix. Conversion results showed that: By introducing of lodrigues matrix, not only the algorithm becomes simple but also the coordinate transformation precision is improved.

Abstract: The auto-disturbance-rejection-controller (ADRC) is a new control theory that doesn’t need the exact object model. The variation of load resistance is observed and estimated by an extended state observer, which is the core of the ADRC. It is known to all that t-he output power of wind turbine is direct ration to the third power of wind speed; hence the flywheel is introduced to keep the stable current output. The system is composed by the permanent magnetism synchronized generator wind turbine and the permanent magnetism synchronized generator flywheel. The control system is nonlinear, the nonlinear parts of the system can be considered as the disturbance which is estimated by an additional state. The Matlab simulink software and lab system have been carried out and the results confirm the robustness of the ADRC.