Applied Mechanics and Materials Vols. 448-453

Abstract: A thermal power plant, where there are hundred of equipments, and many of them are usually controlled by sequential control system (SCS),which is a part of Distributed control system (DCS). For a relatively independent process system, it can be controlled by some of steps, generally, we use the traditional sequential control module supplied by DCS to construct the control logic. This article introduces a brand new control strategy -- the Sequential Control based on Device Code (SCDC). This control method can be used in the occasion of a large number of equipments to be controlled, with the advantage of clear structure, easy maintenance etc.. This method can be widely used in many technological control fields.

Abstract: A three-dimensional physical mode of metal foam tube was built by CFD software. The Brinkman-Forchheimer extended Darcy equation and user-defined function (UFD) of the mass transfer and energy transfer between vapor phase and liquid phase compiled by C language were used in the simulation of boiling heat transfer in metal foam tube. The results show that, at a given mass flow rate, the pressure drop nonlinearly increases as the vapor quality rises; At the low mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to wavy flow from stratified flow and then transfer to stratified wavy flow, while the heat transfer coefficient decreases with the increasing of vapor quality. At the high mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to annular flow from slug flow, while the heat transfer coefficient increases with the increasing of vapor quality. The simulation results agree well with the experimental data.

Abstract: According to the view of heat transfer, the process of the fluid flow with high temperature and high speed over a flat plate may be considered as the heat transfer process within a compressible thermal boundary layer. Based on the numerical results of thermal isolation assumption, combining the temperature comparison with modification method, a coupled method of convection heat transfer coefficient with temperature field of the plate is established, and the characteristics of the thermal response for the flat plate is dominated. Take some ribbed plates as instances, the convection heat transfer coefficient and temperature field of the plate are simulated through the provided coupled method. The results show that, not only the position and materials of the plate influence the convection heat transfer coefficient, but also the time.

Abstract: The coefficient of thermal conductivity is one of the important parameters of concretes thermal performance and it has a relatively great influence on the temperature field inside its structure. This paper explores the basic equipments of the experiment on concretes coefficient of thermal conductivity and the requirements on configuration of primary materials. In the meanwhile, it studies the establishment of the model of concretes coefficient of thermal conductivity from the theoretical basis of thermal conductivity simulation, the division of thermal fluxs pathways and that of K in the formula of the coefficient of thermal conductivity.

Abstract: In order to detection wind turbine equipment and accurately assess the the equipments condition, this paper combines cloud theory, and propose a new comprehensive evaluation method about wind turbine operating status. Use AHP to establish wind turbine evaluation system, and taking advantage of variable weight mode correct quantitative indicators right weight. Adopt Cloud model function represent the indicator data, and establish improved evaluation model, finally, an example verify the effectiveness of the method.

Abstract: This paper has mainly studied the double bending elliptical vibration transducer with the method of limited element analysis, mold analysis of dynamics and moment analysis etc. The modal analysis for double bending elliptical vibration transducer have been processed with ANYS base on mechanical properties electromechanical coupling characteristics of PZT-4 piezoelectric ceramics, therefore the variety of vibration modal of transducer are obtained. The vibration displacement distribution was obtained through driving both directions of piezoelectric ceramics by different phase of the voltage signal. The vibration displacement of the x axis, y axis and z axis direction in the transducer end center were extracted, at the same time, the vibration displacement was entirely fitted, the different ellipse fitting curve were drawing by changing phase displacement and vibration frequency. The result of the dynamics analysis indicates when the frequency is 19.403 kHz and phase difference is π/6, it can achieve optimum elliptic curve, its axle ratio is 1:2.

Abstract: Solutions of the problems existing in design of power machinery were analyzed. Furthermore, through the introduction of bionic ideas into the design, new thoughts and methods for the innovative design of future power machinery were proposed. After summarizing the application of the bionics in macro and micro aspects, the concept of living power machinery was established finally. Bionic ideas experienced from unconsciousness to consciousness, which will finally push the design of power machinery to a new stage and will help build more power machinery, safe, sustainable, energy-efficient and harmonious.

Abstract: A density correction function was introduced into SST (shear stress transport) model in CFX by user defined subroutine. The unsteady cloud cavitation around a Clark-y hydrofoil was numerically simulated using the modified SST model, associated with Zwart cavitation model. The quasi-periodic evolution of cloud cavity and lift coefficient variation were analysed. The results compared with experimental data show that the modified SST model reduces turbulent viscosity in the rear part of cavity and the reentrant jet in cloud cavitation is predicted. The quasi-periodic evolution of cavity generation, development and collapse is captured accurately and the calculated lift coefficient curve is consistent with the experimental date. It can be concluded that the modified SST model used in this paper has a good applicability in the unsteady cloud cavitation simulation.

Abstract: Characteristics of multiple conditions and nonlinear are existed in working process of thermal power unit. To solve the problem, a LS-SVM multi-model modeling of oxygen content in flue gas method based on affinity propagation clustering is presented. In this method, affinity propagation clustering is firstly used to cluster the training samples. Then, the sub-models of LS-SVM are trained by sub-samples. The predicted value of the testing sample is estimated by the sub-model which is selected by similarity measurement. The proposed method has been applied to modeling experiment based on the field data. The experiment shows that the proposed modeling method has superior regression accuracy and better ability of generalization.

Abstract: Experiments were separately carried out on Liquefied Petroleum Gas (LPG) and gasoline as fuel for a spark ignition (SI) engine. According to the indicator diagram and the calculation of corresponding heat release, combustion characteristics of the two fuels were analyzed. The results showed that using LPG would lead to 7.64% power reduction and a little peak pressure reduction when the structures and ignition advance angle of the engine were remained. At rated speed and full load, the power of engine fueled with gasoline reaches the maximum when the excess air ratio is 0.90 and 0.76 fueled with LPG; when comparing the maximum power and specific heat consumption at different excess air ratios, we can see that the change of excess air ratio has a greater effect on the engine fueled with gasoline than that fueled with LPG; the specific heat consumption of both fuels decrease with the increase of load. Besides, under the same Фa, LPG has a shorter combustion delay period, faster combustion speed and shorter combustion period than gasoline.