Enhancement of dynamic performance of wave energy converter by introducing a flow control

The stabilization of power take-off (PTO) is imperative especially under circumstances of fluctuating input wave energy. In this paper, a flow control valve is introduced to optimize the transient process of the hydraulic PTO, which can contribute to a quicker adjustment and a stronger stability. Under variations of input power and load torque in transient process, an open-loop control method and a closed-loop control method are proposed as the opening law of the above valve, and the hydraulic motor speed, the pressure at the accumulator inlet and the generated power are chosen as indicators to examine the regulation performance. Then, the synergic effect of the flow control valve and the accumulator in the transient process is discussed. The effectiveness of the two presented control methods on the fluctuation suppression is respectively tested and compared in both regular wave and irregular wave situations via simulation. To validate the practical effectiveness of the proposed methods, field experiments are conducted. The results demonstrate that the open-loop control can only improve the damping ability of the hydraulic PTO in the speed raising stage, while the closed-loop control can improve the stability both in the speed raising stage and in the load increasing stage.

Dynamics of interphase interaction between components during mixing

The processes of mixing, whipping, and foaming are essentially uniform and consist in dispersing the gas in a liquid. When mixing and whipping, the mixture of components is swollen due to the mechanical action; increased in volume water-insoluble protein substances (gluten proteins) form a three-dimensional spongy mesh continuous structure. It is called a gluten frame. It determines the elastic and resilient properties of the medium. Therefore, the purpose of the study is to establish the relationship between the gas holding capacity of the medium and the energy expended on the hydration of the components. The study solves the task of determining the gas holding capacity of the medium with variable parameters of the height of the liquid phase from the mixing intensity, the duration of transient processes for the formation of the full volume of the gas-liquid medium, the duration of the transient process for the dispersed gas phase yield. The difference between the levels before the gas phase formation and during the mixing (aeration) mode determines the value of the gas holding capacity. In this context, we concluded that it is expedient to completely destabilize the established modes by changing the operating modes in the working body in the flow system. An additional effect on the system is the change of hydrodynamic regimes due to the unstable dynamics of the dispersed gas phase formation. The generation of the dispersed gas phase means the presence of energy expenditure on the interphase layer formation, which should be considered in the total energy balance. At the same time, another feature should be mentioned. Part of the gas phase, which existed and continues to exist in the new mode after mixing, enters the mode of a transient process. Therefore, the most effective mixing occurs while adhering to the shifted mode for dosing components in a suspended state and the mechanical impact of the working body. Based on the given objectives and conditions of sponge dough mixing, we determined the requirements for the mixer design and found that the supply of components should last at least 45 seconds. During this period, hydration occurs and energy consumption is declining.

Experimental analysis of a prototype voltage stabilizer using an optoelectronic proximity voltage relay

This article discusses the issues of experimental analysis of power quality indicators when using a voltage stabilizer using an optoelectronic proximity voltage relay. Where, the booster voltage stabilizer, the magnetizing windings of which are switched using non-contact voltage relays made on the basis of semiconductor devices, as well as the duration of the transient process when switching active and active-inductive loads connected to the output of the stabilizer. In addition, the article provides information regarding the performance of the developed prototype voltage stabilizer using an optoelectronic contactless voltage relay and verification of an experimental study of the operation of installations with their use. Also presented is material on the experimental study of a prototype voltage stabilizer using an optoelectronic contactless voltage relay in various operating modes. Summarizing the results of experimental studies of a prototype voltage stabilizer using an optoelectronic contactless voltage relay, it can be stated that it fully meets the requirements for such devices and can ensure reliable operation of the power supply network of household electrical consumers.

Investigating the reliability of all-optical switches in transient mode

In this paper the scheme of 8×8 all-optical switch with two duplicating switching elements and the algorithm of its functioning are presented. For calculating the reliability of all-optical switches, the analytical method based on the Markov process theory is presented. This method allows us to calculate reliability indicators of the all-optical switches as downtime coefficient and availability factor in stationary and transient modes and time of transient mode. The results of numerical calculations show that an increase in the number of duplicating elements by one gives decrease in the downtime coefficient by 6 percent, and the time of the transient process is halved in this case.

Complete characteristic curve processing method based on improved backpropagation neural network and Logarithmic curve projection

The calculation of transient process is the basis of the design and construction of pumped storage power plant, which directly affects operation stability of pumped storage units. However, for satisfying the design of uniform and smooth flow in both directions, the complete characteristic curves of pumped turbine show a significant S feature, which brings difficulties to the interpolation calculation in the transient process as there are crossover and overlap phenomenon in pump and turbine working conditions. In this paper, a transformation method for complete characteristic curves based on logarithmic curve projection and improved backpropagation neural network is presented to solve the above problem. Furthermore, the feasibility and accuracy of the method are verified through the comparison of load rejection condition with on-site measurement, the results show that the proposed method overcomes the multi-value problem that exists in the original curve, in especial makes the small opening region well expressed. The simulation based on the transformed curve reaches a high similarity of transient process with the field test, both in the trend and extreme values, which provides great convenience for the calculation of transient process.