Applied Mechanics and Materials Vols. 291-294

Abstract: The scarcity of the fossil fuels and the large amount of energy consumption in the world trigger the development of bioenergy. Bioenergy is friendly to the environment and could benefit the human being and the whole society. This paper analyzes the cornstalk processing for the bioenergy in China. It explores the feasibility of the cornstalk using in the bioenergy production from the supply side and the demand side. The effects of the cornstalk used for bioenergy production are investigated. Finally, the conclusion is made that the cornstalk is a best substitute for bioenergy production in China.

Abstract: Transesterification were carried out under microwave irradiation conditions and the effects of imidazolium hydroxide with different branched alkyl side-chains ([Cnmim]OH, n = 2, 3, 4) were investigated. The results showed that less than conventional amount of NaOH, and the alkaline ionic liquids formed clearly biphasic systems immediately after the transesterification of soybean oil with methanol was finished. The method offers significant improvement over conventional techniques in terms of operational simplicity, processing time reduction and excellent yields. Among the imidazolium salts studied, [C2mim]OH proved to be the most efficient catalyst, affording 96 % yield.

Abstract: Various physical factors including particle size, pH, temperature and so on may influence the release of organic materials from dry dairy manure. The effect of these factors on release of protein and carbohydrate was investigated in this study using Box-Behnken Experimental Design with three factors (particle size, temperature and pH) at three levels. Test results suggested that particle size of 0.15-0.25 mm accounted for almost half of the dry manure particles and the optimum condition for release of protein and carbohydrate were pH 2, particle size 1.0-1.4 mm under reaction temperature of 90 oC, under which the protein and carbohydrate release rates could reach 1570.57 and 2813.29 mg l-1, respectively. The degree to which these factors affected organics release was in the order from high to low of temperature > particle size > pH.

Abstract: Eucalyptus broken wood, eucalyptus bark, sugar cane leaves and bagasse as the representative of South China typical biomass have been investigated by experimental study. The experimental study was carried out to study the devolatilization law and the fixed carbon burning law, also the NOX emission characteristics. The experiments showed that the influence of temperature on combustion, especially in the initial stage of combustion, the weight loss rate difference were up to 60%. The NOX emission experiments showed that the NOX emission of eucalyptus bark was the maximum in 700°C combustion.

Abstract: In order to meet the requirements of LVRT and realize the asymmetry control in wind power system, the voltage phase, amplitude, and frequency are needed in real time under both asymmetrical and symmetrical low Voltage condition. Based on double DQ synchronous rotating coordinate system and software phase-locked loop (SPLL), the amplitude and phase angle of both positive and negative sequence components are obtained. Finally, through Matlab simulation and Low voltage device experiment, it proves that the algorithm has the advantages of accurate detection, interference resistance, and strong adaptability.

Abstract: The output power of wind farms has significant randomness and variability, which results in adverse impacts on power system frequency stability. This paper extracts wind power fluctuation feature with the HHT (Hilbert-Huang Transform) method. Firstly, the original wind power data was decomposed into several IMFs (Intrinsic Mode Functions) and a tendency component by using the EMD (Empirical Mode Decomposition) method. Secondly, the instantaneous frequency of each IMF was calculated. On this basis, taking a WSCC 9-bus power system as benchmark, the impact on power system frequency caused by wind power fluctuation was simulated in a real-time simulation platform, and the key component which results in the frequency deviation was found. The simulation results validate the wind power fluctuation impacts on frequency deviation, underlying the following study on power system frequency stability under the situation of large-scale intermittent generation access into the grid.

Abstract: Combined with characteristics of wind turbine bolt connection structure, with the connection of pitch bearing inner ring and the blade root as the research object, through the finite element analysis software Ansys, establish various connection model, using the multiple point coupling constraint and nonlinear contact for finite element analysis , research on bolt truss element types, connections of each component and the establishment of contact, then obtain and analysis affects of finite element calculation with different element types of bolt truss ,contact relationship ,compared with theoretical results, put forward feasible finite element analysis scheme of wind turbine bolt connection, and provide basis for the structure design and intensity analysis.

Abstract: Based on the local acceleration effect generated by air flow passing through obstacles, this study explored changes in the surrounding wind field of buildings and the possibility to develop the potential wind energy by installing wind deflector in building according to the concept of “dredging” to facilitate the integrated application of small-scale wind turbine in buildings. With a nine-story building as the research subject, this study used the wind deflector installed on the building roof to generate the contracted flow effect (Venturi effect) to accelerate the air flow, change wind field and thus increase the possibility of wind power use as well as the power generation efficiency of the small-scale wind turbine. This study applied the numerical simulation method to discuss differences in three cases of no wind deflector (N-WD), installing lower wind deflector (L-WD) and installing upper and lower wind deflectors (2-WD). It also evaluated the impact on wind field and contribution to wind speed acceleration.

Abstract: This paper proposes a new method for horizontal axis wind turbine (HAWT) angle of attack (AOA) determination. Despite common circular planes for data extraction, here, data is extracted on rectangular planes. NREL Phase VI is used for validation of the method. Results show that even in a high velocity wind the proposed plane can be an appropriate choice. Furthermore, the average radial distributions of axial and tangential induction factors are calculated based on the velocity values at the planes. Moreover, local normal force coefficients are calculated and then, the local AOA are compared with 2D results and other 3D values for different wind speeds.

Abstract: This paper has proposed a wind farm generation output forecasting model based on projection pursuit (PP) and back propagation neural network (BPNN), in order to eliminate the influence of the bad points and mutations on and enhance robustness of the forecasting model. A median absolute deviation is used as projection index function, effectively avoiding the influence of the outlier. Firstly, Extract the principal components of each factor by PP. Then, input the principal components to the BPNN for training the network. Finally, forecast the wind farm generation output via the trained network. The simulation shows that the proposed approach is of higher accuracy.