可程控交流电源供应器简介及应用

将电压波形编辑、输出功率级、输出量测整合成一台仪器,就称为可程控交流电源供应器(Programmable AC Source).

Effect of Adsorbent Diameter on the Performance of Adsorption Refrigeration

Adsorbents are important components in adsorption refrigeration. The diameter of an adsorbent can affect the heat and mass transfer of an adsorber. The effect of particle diameter on effective thermal conductivity was investigated. The heat transfer coefficient of the refrigerant and the void rate of the adsorbent layer can also affect the effective thermal conductivity of adsorbents. The performance of mass transfer in the adsorber is better when pressure drop decreases. Pressure drop decreases with increasing permeability. The permeability of the adsorbent layer can be improved with increasing adsorbent diameter. The effect of adsorbent diameter on refrigeration output power was experimentally studied. Output power initially increases and then decreases with increasing diameter under different cycle time conditions. Output power increases with decreasing cycle time under similar diameters.

Blade pitch control of straight-bladed vertical axis wind turbine

Collective pitch control and individual pitch control algorithms were present for straight-bladed vertical axis wind turbine to improve the self-starting capacity.Comparative analysis of straight-bladed vertical axis wind turbine(SB-VAWT) with or without pitch control was conducted from the aspects of aerodynamic force,flow structure and power coefficient.The computational fluid dynamics(CFD) prediction results show a significant increase in power coefficient for SB-VAWT with pitch control.According to the aerodynamic forces and total torque coefficient obtained at various tip speed ratios(TSRs),the results indicate that the blade pitch method can increase the power output and decrease the deformation of blade;especially,the total torque coefficient of blade pitch control at TSR 1.5 is about 2.5 times larger than that of fixed pitch case.Furthermore,experiment was carried out to verify the feasibility of pitch control methods.The results show that the present collective pitch control and individual pitch control methods can improve the self-starting capacity of SB-VAWT,and the former is much better and its proper operating TSRs ranges from 0.4 to 0.6.

Pervoskite-type Bao.sSro.sAl0.1Fe0.9O3-δ as Intermediate-Temperature Solid Oxide Fuel Cell Cathode

A cobalt-free perovskite-type Ba0.5Sr0.5A10.1Fe0.9O3-δ （BSAF） chemically studied as solid oxide fuel cell （SOFC） cathode. The ductivity, and electrode polarizations in symmetrical cell based is developed and electro- structures, electrical con- on mixed ion conducting electrolyte were investigated, respectively. The temperature dependence of conductivity of BSAF in air shows a typical semiconductor behavior with positive temperature coefficient up to 450℃ where the conductivity reaches 14.0 S/cm while above this temperature the negative temperature coefficient dominates the total conductivity. Electrochemical charac- terizations show desirable polarization resistance of BSAF cathode in a symmetric cell based on mixed ion conducting electrolyte at 650-700℃, A single SOFC with BSAF cathode shows OCV of 1.0 V and maximum output of 420 mW/cm2 at 700 ℃ with humidified hydrogen fuel and static air oxidant.

Novel Switched Reluctance Motor with Auxiliary Winding

The characteristics of the novel switched reluctance motor with auxiliary winding and four big swallow-tailed-slots in the internal surface of stator is analysed with the stator cross section and winding photo given, and the nlathematical model of the novel switched reluctance motor presented. To show that the auxiliary winding causes the electromotive force to improve current waveform and increase output power. The different effects of auxiliary winding on system performance under different speeds are analyzed and experimented. Simulation analyzing and experiments studying of the novel switched reluctance motor demonstrate validity of auxiliary winding improving current waveforms, increasing output power.

Fabrication and performance evaluation of the thermoelectric generation and performance measuring system

A novel thennoelectric generating and performance measuring system （TGPMS） was designed and fabricated. TGPMS can not only achieve the function of thennoelectric generation, but also measure the thennoelectric performance parameters of the bismuth-telluride-based thennoelectric device accurately. These thennoelectric performance parameters mainly include the dependence of the Seebeck coefficient of the thennoelectric device on the device＇s temperature in the low temperature range （about 40 ~ 190~C ）, and the dependence of the power output and thermoelectric conversion efficiency on the temperature dif- ference or output load. With the optimum load, the optimal value of the power output is 3.39W when the temperature difference reaches 231.2~C, and the optimal value of the conversion efficiency is 3.22% when the temperature difference reaches 208.9~C. TGPMS provides an experimental foundation for the application of the thennoelectric generators in the space field.

Investigation of the performance of the dish/stirling solar thermal electricity system

A dish/stifling solar thermal electricity system consists of two parts： a dish solar concentrator and a Stifling engine. For optimizing the system, in this paper, the mathematical model for concentrator design was established and the effects of those design parameters of concentrator, such as the size and intensity of the focal point, the receiver temperature, on the efficiency of the Stifling engine and output power were numerically simulated. The results of the simulation revealed a close relationship between power and efficiency because of power losses, and there was a maximum for the engine efficiency and power with increasing solar radiation because there was a peak value of system efficiency with increasing receiver temperature. So, in view of our Stifling engine, the 450 rim angle and 6m focal length are optimal design for concentrator and the 800℃receiver temperature is best.

Analysis and Control of a Three-Phase Switched Reluctance Wind Generator

This paper deals with various aspects of modeling, simulation, analysis, and control ofa SRG （switched reluctance generator） in different modes of operation. Excitation method of such a generator is shortly described. The output power of the SRG is controlled so that it can track the maximum output power of a wind turbine drive applications. Also, the output generator voltage is stabilized under either load or wind speed variations. Basic operational characteristics of a three-phase 6/4 SRG are developed through experimental observation. Meanwhile, the real-time operation was implemented in a DSP （digital signal processor） environment. The simulation of the complete system model has been obtained using the Matlab/Simulink software. A good agreement between experimental and simulation results has been observed which supports the validity of the proposed analysis.

Mathematical modeling of output power in RF-excited CO_2 waveguide lasers

Theoretical analysis model has been established for CO 2 laser to describe the process of dynamic emission in the electrooptically Q switched laser .The electron excitation and the energy transfer of vibration level and the rotational relaxation of rotational levels are described. The comparison between this model and a set of coupled rat equations model are discussed.

Decreasing of Grid-Tied PV Power Output due to Thick Haze Phenomena in Malaysia

Recently, thick haze and poisonous smoke have cloaked the surrounding air in Malaysia due to the uncontrollable and unethical burning of nearby country. This devastating episode of open burning started in the year 1997 in Indonesia which deeply affected most of the ASEAN （association of southeast asian nations） countries especially their neighbour Malaysia and Singapore. The PV （photovoltaic） technology as an alternative means of energy generation experiences such significant energy decrease based on this condition which is due to the shading of sunlight. The 6 h claims of good sunlight has become not more than 2 h and gets worst when the API （air pollution index） struck 200 levels which is at very unhealthy condition. This study embraces some findings from 1 kWp PV generator field data installed in Malaysia reflecting the daily energy decrease operated during this unhealthy weather condition. It is found that, such significant energy decrease with the value of 0.43 W power output per increment of one point API. This value shows such concrete proof of additional factors to be considered in PV modelling in line to support PV technology adaptation in the ASEAN region.

Analyses of thermodynamic performance for the endoreversible Otto cycle with the concepts of entropy generation and entransy

In this paper, the endoreversible Otto cycle is analyzed with the entropy generation minimization and the entransy theory. The output power and the heat-work conversion efficiency are taken as the optimization objectives, and the relationships of the output power, the heat-work conversion efficiency, the entropy generation rate, the entropy generation numbers, the entransy loss rate, the entransy loss coefficient, the entransy dissipation rate and the entransy variation rate associated with work are discussed. The applicability of the entropy generation minimization and the entransy theory to the analyses is also analyzed. It is found that smaller entropy generation rate does not always lead to larger output power, while smaller entropy generation numbers do not always lead to larger heat-work conversion efficiency, either. In our calculations, both larger entransy loss rate and larger entransy variation rate associated with work correspond to larger output power, while larger entransy loss coefficient results in larger heat-work conversion efficiency. It is also found that the concept of entransy dissipation is not always suitable for the analyses because it was developed for heat transfer.

Pneumatic Performance of Staggered Impulse Turbine for OWC Wave Energy Convertor

A staggered impulse turbine is proposed for asymmetric air flows in Oscillating Water Column wave energy plants, which is expected to enhance the pneumatic power output in a wave cycle. The setting angle of rotor blades is set as 5°. The 3D numerical simulations were conducted under steady conditions using MRF and Mixing Plane model based on CFD software Fluent 12.0. Its mean efficiencies under different velocity amplitude ratios are studied using quasi-steady analysis, which derive corresponding data from the numerical simulation. It is found that the staggered turbine shows better performance than the conventional one under the asymmetrical air flows. Furthermore, its mean efficiency and output-work in a wave period are compared with another unsymmetrical twin impulse turbine system. The results show that the staggered turbine shows better output-work performance than the twin turbine system over the high flow coefficient domain(φ>0.7), which provides more choices to future research on turbine's optimization.

Study on Drug Property Differences of Shexiang (Moschus) and Bingpian (Borneolum Synthcticum) Based on Analysis of Biothermodynamics

Objective: To study the drug property differences of Shexiang (Moschus) and Bingpian (Borneolum Synthcticum) with biothermodynamics, and to verify the objectivity and authenticity of the drug property. Methods: The growth-thermogram curves of Escherichia coli (E. coli) affected by Shexiang (Moschus) and Bingpian (Borneolum Synthcticum) at different concentrations were determined with microcalorimetry, and the power-time curves (thermogram curves) of E. coli metabolism and characteristic parameters, such as growth rate constant (k), maximum output power (Pm), peak time (tp), total heat-output (Qt), etc. were analyzed with the principal component analysis (PCA) to find the close correlative parameters, so as to objectively reflect the drug property differences of Shexiang (Moschus) and Bingpian (Borneolum Synthcticum). Results: The values of P2 in the second exponential growth phase increased with the increase of the concentrations of Shexiang (Moschus) and Bingpian (Borneolum Synthcticum), and the P2 of Shexiang (Moschus) was larger than that of Bingpian (Borneolum Synthcticum); Q2 increased with the increase of the concentrations of Shexiang (Moschus), but for Bingpian (Borneolum Synthcticum) it was opposite. It is indicated that they have different effects on P2 and Q2 of E. coli in the second exponential growth phase, and have differences in warm and cold natures. Conclusion: The microcalorimetry can accurately and objectively appraise differences of the drug property of Shexiang (Moschus) and Bingpian (Borneolum Synthcticum) and verify the objectivity and authenticity of the drug property, so as to provide a new and useful method for studies of the drug property of Chinese drugs.

Unsteady Flow Analysis of an Axial Flow Hydraulic Turbine with Collection Devices Comprising a Different Number of Blades

We previously devised a new type of portable hydraulic turbine that uses the kinetic energy of an open-channel flow to improve output power by catching and accelerating the flow. The turbine contains an axial flow runner with an appended collection device and a diffuser section that is not axisymmetric. The objective of this study is to determine how interference between the collection device and the runner influences performance characteristics of the turbine. We investigated the performance characteristics of the turbine and flow field for different numbers of blades during both unsteady and steady flow. During an unsteady flow, the maximum values of power coefficients for three and two blades increased by approximately 8.8% and 21.4%, respectively, compared to those during a steady flow. For the three-blade runner, the power coefficient showed small fluctuations, but for the two-blade runner, the power coefficient showed large fluctuations. These fluctuations in the power coefficient are attributed to fluctuations in the loading coefficient, which were generated by interference between the runner and the diffuser section of the collection device.