The paper presents results of experimental investigation of microchannel boiling flow which was controlled by dielectrophoretic (DEP) restrictor. The DEP restrictor was connected to the microchannel liquid supply tube. Operation of DEP restrictor influenced the flow rate at the microchannel inlet. Resulting changes in flow structures and vapour content along the microchannel were observed and analysed with a high-speed video camera. Video recordings were synchronised with measurements of differential pressure between the channel inlet and outlet. It was found that it is possible to change average void fraction in the microchannel by switching on and off the voltage applied to the restrictor electrodes. However, to achieve significant variation of the void fraction, applied voltage should be of the order of 2000 Vpp. The voltage switching also generates oscillations of the differential pressure. The amplitude of these oscillations is proportional to the voltage magnitude, reaching 35 Pa for 2400 Vpp.
The deployment of a distributed power-flow controller (DPFC) in a single-machine infinite-bus power system with two parallel transmission lines are considered for the analysis in this paper. This paper presents the network analysis of the DPFC for power flow control. The performance is evaluated on a given test system with a single line-to-ground fault. The improvement in the stability as well as power quality is evident from the results. Thus the DPFC has the ability to enhance the stability and power quality of the system.
The Variable Frequency Drive (VFD) is used to control the speed of the pumpmotor to attain the desired flow rate and fluid level in a fluid system. An AC drive provides efficient flow control by varying the pump-motor speed. The comparison of energy requirements and costs in a system where a throttling device is used for flow control on a centrifugal pump with the power used when an variable frequency drive (VFD) is used to control the same flow, evidently shows potential savings. In this system, AC Motor Frequency drive and static pressure transmitter, turbine type flowmeter and Analog/Digital cards, micro-control unit and computer connection are designed specially to control flow rate, fluid flow type (turbulence or laminar) and water level at the different conditions with different PID parameters.
This paper proposes a methodology based on installation cost for locating the optimal position of interline power flow controller (IPFC) in a power system network. Here both conventional and non conventional optimization tools such as LR and ABC are applied. This methodology is formulated mathematically based on installation cost of the FACTS device and active power generation cost. The capability of IPFC to control the real and reactive power simultaneously in multiple transmission lines is exploited here. Apart from locating the optimal position of IPFC, this algorithm is used to find the optimal dispatch of the generating units and the optimal value of IPFC parameters. IPFC is modeled using Power Injection (PI) model and incorporated into the problem formulation. This proposed method is compared with that of conventional LR method by validating on standard test systems like 5-bus, IEEE 30-bus and IEEE 118-bus systems. A detailed discussion on power flow and voltage profile improvement is carried out which reveals that incorporating IPFC into power system network in its optimal location significantly enhance the load margin as well as the reliability of the system.
The paper presents the influence of different liquid cargo properties on discharge rate of hydraulic submerged cargo pumps on modern product and chemical tankers is presented in the paper. Main parts of submerged cargo pumps and hydraulic drive system are described. Some examples of technical solutions of the described systems installed on board of the newly building constructed ship m/t ‘Helix’ are presented. The formula of use application of flow and drive characteristics of cargo pumps is given. These characteristics were made derived for a basic cargo (fresh water) for the case of the service of a real cargo of different viscosity and density.
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The uncontrolled power flow in the AC power system caused by renewable energy sources (restless sources, distributed energy sources), dynamic loads, etc., is one of many causes of voltage perturbation, along with others, such as switching effects, faults, and adverse weather conditions. This paper presents a three-phase voltage and power flow controller, based on direct PWM AC/AC converters. The proposed solution is intended to protect sensitive loads against voltage fluctuation and problems with power flow control in an AC power system. In comparison to other solutions, such as DVR, UPFC, the presented solution is based on bipolar matrix choppers and operates without a DC energy storage unit or DC link. The proposed solution is able to compensate 50% voltage sags, in the case of three-phase symmetrical voltage perturbation, and single phase voltage interruptions. Additionally, by means of a voltage phase control with a range of ±60◦ in each phase, it is possible to control the power flow in an AC power system. The paper presents an operational description, a theoretical analysis based on the averaged state space method and four terminal descriptions, and the experimental test results from a 1 kVA laboratory model operating under active load.
The genesis of both coherent structures and reactive flow control strategies is explored. Futuristic control systems that utilize mi-crosensors and microactuators together with artificial intelligence to target specific coherent structures in a transitional or turbulent flow are considered. Of possible interest to the readers of this journal is the concept of smart wings, to be briefly discussed early in the article.
This paper presents a load equivalent conductance based control method for a shunt active power filter. The principle of energy balance in the circuit, which means between supplying source - active filter - load, is used to obtain the control formula. The natural inertia of the active filter action is exploited, so no PI regulators are needed. The active filter can compensate for non-active current and, additionally, can stabilise the supplying source active power. In a case of generating loads energy harvesting is possible. The presented method is useful as well for voltage-source as current-source inverter based active filters, and for DC system as well as for AC single- or three-phase one.
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