Applied Mechanics and Materials Vol. 392

Abstract: In this communication we present a new active method to modify two-phase flow distribution in a heat exchanger, when it is in operation, by using ultrasound generators which can be activated when necessary. An experimental study has been carried out to validate the concept and to evaluate the effects of ultrasound on the flow distribution. An experimental test rig was built to measure the flow distribution in realistic manifold and parallel channel geometry. The test section is composed of a manifold feeding 10 channels with air-water mixture. In front of each channel a piezoelectric generator is placed to emit ultrasonic waves which can interact with liquid flows. Comparison was made between two-phase flows with and without ultrasound. It was demonstrated that, in most cases, uneven distribution was improved by using ultrasound.

Abstract: The short-circuit test is an important topic on the study of transformer features. With the shunt capacitor paralleled to the tested transformer, the test current can be reduced by the resonant of the capacitor and the inductance of transformer winding. Furthermore, using the high frequency power supply, the capacitor can be reduced in the resonant point because the high frequency values. In this work, the simulation model of short-circuit test of transformer with different frequency power supply is designed. Under variable frequency power supply, which are 50Hz,100Hz and 150Hz, the shunt capacitors value is given. From the simulation results, the application of the shunt capacitor takes a role in the short-circuit test of transformer. This has a significance role in transformer test research and engineering application field.

Abstract: Energy balances are increasingly used to assess the energy efficiency and productivity of production. In this study, energy balances for the slow pyrolysis process of cow manure were calculated. The results show that, for cow manure dry matter, all the recovered energy value from the pyrolysis process products is about 12 times of the energy needs for the dry matters pyrolysis process. But the moisture has a noteworthy impact on the energy efficiency. When the input moisture is 60.85%, the recovered energy value from all products is approximately equal to the process energy consumption, and if only using non-condensable gases (NCG) as the energy resource, the input moisture should lower than 36.63%. Meanwhile, if the vapor could be separated in the beginning phase of pyrolysis process, the energy efficiency will be greatly improved, e.g. if removed all water vapor out the system at 423K, the former two data could be 71.43% and 48.18%, which is 10.58% and 11.45% higher than the process without vapor separation handling.

Abstract: In order to supply a reliable and low-cost method for construction machinery real-time test, take a hydraulic excavator for example. Especially for testing controllers and evaluating the performance of strategies, a hardware-in-the loop platform has been developed based on the xPC real-time system. The hardware-in-the-loop system, including dynamic model of the excavator and an 3D real-time display subsystem, is presented in this paper. The simulation results are also described at the end of the paper.

Abstract: Generation scheduling is one of the major contents of power dispatch and has an important impact on the safe and efficient operation of power grid. As a newly-established provincial power grid, Jibei power grid bears features like multiple regional wind power installations and high rate of external power receiving, etc., and it urgently needs to develop a secured and economic power scheduling system with comprehensive consideration of various constraints. Aiming at features of Jibei power grid, this paper gives an overall design scheme of the day-ahead power scheduling system. The application indicates that this system can efficiently optimize generation schedule and power flow distribution, intensify the decision ability and intelligence level of power dispatch.

Abstract: This paper presents a new method for transient stability assessment (TSA) of power systems using kernel fuzzy rough sets and extreme learning machine (ELM). Considering the possible real-time information provided by phasor measurement units, a group of system-level classification features were firstly extracted from the power system operation condition to construct the original feature set. Then kernelized fuzzy rough sets were used to reduce the dimension of input space, and ELM was employed to build a TSA model. The effectiveness of the proposed method is validated by the simulation results on the New England 39-bus test system.

Abstract: In this paper, system operating costs as the objective function, considering the reduced costs of system losses after compensation and the adding costs of compensating devices, established reactive power compensation optimization mathematical model of distribution system with photovoltaic station. And to improve the standard particle swarm optimization, adopting particle swarm optimization to optimize an example, optimizing results verify the accuracy and effectiveness of the model and algorithm.

Abstract: In China, more and more power communication network soft-switch transformation is proposed. In this context, the article analyzes the principle of the introduction of the soft-switch technology. Detailed design methods and strategies for the introduction of soft-switch technology. and compare these rehabilitation programs. Analysis application of soft-switch in Huizhou and Xianning.

Abstract: Frequency influencing factors in small weak receiving power grid with wind power penetration during the disturbance of power shortage are analyzed in this paper, such as wind power penetration rate, wind turbine types, inertia control loop and wind power fluctuation. Based on the influencing factors above, in the light of the phenomenon of large dive depth and long duration of the frequency first swing after fault, the coordination scheme of load shedding and under-frequency load shedding based on the simulation system is proposed: load shedding time and load shedding ratio coordination scheme. Simulation results verify the correctness of the theoretical analysis and the rationality and feasibility of the coordination scheme proposed.

Abstract: Along with the continuous expansion of photovoltaic (PV) power generation, different capacity of grid connected PV system is gradually increased. China's first residential grid-connected PV system has interconnected successfully in QingDao and operated normally. This document analyzed electrical connected diagram of grid-connected PV system. Using power quality analyzer, the online power quality is monitored and analyzed. When PV power generation is low efficiency of operating state, harmonic current is over distortion limits. Monitoring data was simulated through electrical power standard source. To ensure power metering accuracy under harmonic, the watt-second method is proposed. Testing results show that smart electrical meter can meter accurately within 20 times harmonics.