Applied Mechanics and Materials Vols. 313-314

Abstract: In order to fully recycle power plant’s circulatingwater heat, improve the thermal efficiency and protect the environment, thispaper designs the comprehensive scheme of heat pumptechnology recycling power plant’s circulating water heat, including theboiler mae-up water pre-heating system, the central heating circulatingsystem and the domestic hot water circulating system, which not only run at thesame time but also function independently. Even in non-heating seasons,the waste heat of circulating water can be utilized fully. It is worthmentioning that this paper puts forward to install climate compensationdevice in the central heating system, which can perform intelligent district timesharing control to meet different users’ needs.

Abstract: Based on the uncertaintyproblem of decision factors in the fault diagnosis and maintenance ofequipment, the fuzzy method and grey theory were introduced. Firstly, fuzzyterms were applied to describe the basic variables (probability of occurrence,severity and detection). Triangular fuzzy number was selected to carry out thequantitative calculation of fuzzy terms and the defuzzification of membershipfunctions. Then the grey correlations of all Failure modes were computed andrisks were ranked, considering the relative importance of decision factors. Thefuel system of marine diesel engine was taken as an example. It is pointed thatalthough the risk priority numbers are equal, if the values or weights ofdecision factors are different, then the risk levels of Failure modes aredifferent as well. The results indicate that the calculation model can identifythe failures of ship equipment more precisely and optimize allocation ofmaintenance resources.

Abstract: Based on the experiment of vertical evaporative condenser in water vapor condensation, the influence between heat resistances and water spray density, air inlet velocity, spiral inserted tube, wavy tube was studied. The results show the heat resistance at the air-water interface predominates over all other heat resistance, air-water interface heat resistance is particularly declined up to 20.65% with spiral inserted tube, and water condensation heat resistance is particularly declined up to 35.85% with wavy tube.These conclusions are useful for the design, optimization and application of this type of evaporative condenser.

Abstract: The aims of this study are to measure the defect rate and analyze the problems of production of ready concrete mixture plant by using Six Sigma methodology which is a business strategy for operations improvement depending basically on the application of its sub-methodology DMAIC improvement cycle and the basic statistical tools where the process sigma level of concrete production in the case study was 2.41 σ.

Abstract: For existing local severe vibration problems on the pipeline system of conveying ethylene booster in ethylene cracking system of a petrochemical company, the detailed analysis by CAESARII was carried out to its pipeline system natural frequency and vibration modal; The flow of ethylene gas within the booster pipeline from the suction pipe to exhaust pipe inside including the buffer tank was analyzed using fluid analysis software--FLUENT, the pressure field and velocity field of the flow was obtained. According to the law of the suction and exhaust valve open-closed mouth, dynamic boundary conditions was set on the suction valve and exhaust valve. The ethylene flow non-steady-state analysis calculations was carried out within the pipeline from the suction tube inlet to suction valve and from the exhaust valve to the exhaust tube outlet , the law of the pressure pulsation frequency response was obtained on the suction pipe inlet and the exhaust pipe outlet. The results show that ethylene gas pipeline pressure pulsation frequency response was basically equal to the frequency of the suction and exhaust valve open-closed mouth; The actual pipe vibration modals of the pipeline system on the scene and the pipeline vibration modals a few corresponding to the natural frequencies of the pipeline system close to the pulsation frequency in flow pressure are very similar, indicating that the vibration of the pipeline system is due to the pressure pulse frequency of the ethylene gas internal pipeline close to the natural frequency of the local pipeline, caused due to local resonance. Changing the form of hangers in vibration system can change the natural frequency of pipeline to avoid resonance. Tube fluid dynamic pressure caused by the stress of the pipeline is limited and will not cause damage to the tube material. Mass flow rate does not match with the tube diameter will cause too large flow velocity, the inertia force caused by the larger on the suction valve and exhaust valve before and after, resulting in the forced vibration of the compressor body.

Abstract: Preparation of superabrasive grinding wheels presents severe challenges due to the high hardness of abrasive grain. In this paper, electrical discharge dressing (EDD) technology with misted emulsion is applied to dressing bronze-bonded diamond wheels. Dressing experiments were carried out. The wheel profiles before and after dressing were measured using a Dektak 6M profilometer. The diamond wheel surface topographies before and after dressing were observed by three-dimension digital microscope. In addition, the performance of EDD’ed wheel was evaluated in practical grinding. It is shown that favorable surface topography can be obtained under suitable processing parameters and EDD misted emulsion with is feasible for metal-bonded diamond grinding wheel.

Abstract: The wind turbine tower is to bear wind load and work load which is brought by the rotating blades during operation. Therefore, analysis of dynamic characteristics of wind turbine tower is a complicated task in the wind turbine reliability design. The dynamic characteristic of wind turbine tower plays an important role in its vibration control. This paper presents fluid-structure coupled dynamics equations accounting for the blade wheel load and wind load applying on the tower. By the model analysis, a feasible method for evaluating the dynamic characteristics of wind turbine tower under the wind turbine wind load and the rotating blade random load is obtained. The model is verified in the 1.5MW wind turbine.

Abstract: The traditional high-voltage high-frequency transformer has a drawback of low power density due to the rigorous requirements of high voltage insulation. This paper proposes a new configuration for the magnetic core based on planar EE cores. The parallel connection of planar cores was adopted as a unit, and several units were cascaded to form the high-voltage transformer. The electrical potential distribution of the proposed transformer is more uniform than a traditional transformer, and enables a decrease in the insulation distances. The mechanical configuration of a laboratory prototype is discussed, as well as the electrical, parasitic, and thermal behaviors.

Abstract: To solve the problem of harmonic pollution in distributed power system, a new type of grid-connected inverter with harmonic compensation is studied in this paper. This system adopts a unified control strategy with decoupled active and reactive power based on grid voltage orientation. Both the grid connection and harmonic compensation are realized together in one inverter, which improves the inverter’s utilization efficiency and protects the power grid from harmonic pollution. The simulation and experimental results are shown to prove the correctness of the control strategy.

Abstract: With large-scale development of ultra high-transmission network, the structure of transmission line-towers system tends to the tower higher, the cross-section of transmission lines larger and span between towers longer. As the increasing of transmission lines voltage grade, transmission line-towers system has higher requirements on static and dynamic stability. It is difficult for traditional design method to meet the demands of new transmission line-towers, not to mention shorten the design cycle, improve design quality. In this paper, we establish overhead transmission line-towers system model based on parameterized finite element method, by gradually increasing the thickness of the icing, iced load, wind load, weight, mechanical properties under the action of the load and the conductor tension. The analysis results show that the model can effectively reflect the mechanical properties of the transmission towers, and improve the quality of the design, greatly shortening the design cycle.