Energy Flow Characteristics Research Articles

Energy conversion during the crown evolution of the drop impact upon films

The energy conversion is proposed to analyze the effects of inertial force, surface tension, gravitational force and viscous force during the crown evolution of the drop impact phenomena. The incompressible laminar Navier–Stokes equations coupled with the volume of fluid model are solved numerically in the axisymmetric frame to simulate the impact process. The influences of both the ratio of the initial kinetic energy to the surface tension energy of the drop as well as the initial film thickness on the energy conversion during the impact process are studied in detail. The ratio of the initial kinetic energy to the surface tension energy of the drop can affect the energy conversion at a very early stage of the impact process, thus it can affect the occurrence of prompt splash significantly; while the initial film thickness can affect the energy conversion process during the whole impact process, and it is related to the occurrence of delayed splash. The energy conversion process corresponds to the type of impact phenomena, which is affected by the film depth significantly. according to the differences in energy curves and flow characteristics, the impact phenomenon is divided into three types: the drop impacts on shallow, medium and deep films. A typical impact process of the medium film is analyzed in detail. The impact process is divided into five stages, namely, crown formation, crown growth, crown stabilization, crown collapse and central jet formation. In the crown formation and growth stages, inertial force promotes the deformation of the liquid-gas interface and surface tension prevents the deformation; while in the crown collapse stage, inertial force prevents the deformation and surface tension does the opposite effect. During the whole process, the viscous force plays a prevention effect.

Experimental and numerical study of a horizontal-vertical gas-solid two-phase system with self-excited oscillatory flow

To better explore the energy-saving mechanism and flow characteristics of the self-excited oscillatory flow, the experiment is performed by a new self-excited oscillatory flow generator that the 45° oblique sheet is mounted through the pipe axis in a horizontal-vertical closed pneumatic conveying system. The experimental study focuses on the optimum air-velocity and power consumption, and results shows the maximum reduction of the optimum air-velocity and the coefficient of power consumption are approximately 8.2% and 16.4%, respectively. In addition, the CFD-DEM coupled approach is first developed to investigate the interaction of gas-solid flow in terms of the gas turbulent kinetic energy and spatial particle flow characteristics. Compared with the conventional pneumatic conveying, it is found that the optimum air-velocity and power consumption are reduced by the new self-excited oscillatory flow at lower air-velocities. The numerical results show that the approximately symmetric distribution of axial velocity and the intensive tangential velocity is emerged in the self-excited oscillatory flow at upstream. Particles is efficiently dispersed and suspended by the self-exited oscillatory flow reflecting in the smaller particle variation coefficient and the lager particle suspension coefficient. And since the airflow kinetic energy is utilized more fully to promote particles flowing, the spatial particle axial velocity is accelerated and reached early steady state. As a result, the developed numerical model is further explained the mechanism of energy saving with the self-excited oscillatory flow.

Energy performance and flow characteristics of a multiphase pump with different tip clearance sizes

Deep sea oil resources worldwide possess great potential for exploration; however, multiphase medium technology requires urgent development. The multiphase pump has achieved great success as one of the most advanced machinery in underwater oil and gas exploration. Tip clearance is inevitable between the rotating and stationary components of the multiphase pump. In this study, tip clearance sizes of 0.0, 0.2, 0.5, and 0.8 mm are selected to investigate the effect of tip clearance on energy performance and flow characteristics of a multiphase pump. Results show that pressure rises decrease by 10.72%, 24.96%, and 41.39% with gas volume fraction = 0% under different tip clearance sizes, while the pressure rises decrease by 17.10%, 25.35%, and 38.11% with gas volume fraction = 10%. The dominant frequencies and maximum amplitudes of pressure fluctuation rise with the increase in tip clearance. The entrainment effect between the tip leakage flow and main flow in the impeller strengthens with the increase in tip clearance size; the induced vortex area and leakage flow rate also increase.

Spectral analysis of the budget equation in turbulent channel flows at high Reynolds number

The transport equations for the variances of the velocity components are investigated using data from direct numerical simulations of incompressible channel flows at friction Reynolds number ($Re_{\unicode[STIX]{x1D70F}}$) up to$Re_{\unicode[STIX]{x1D70F}}=5200$. Each term in the transport equation has been spectrally decomposed to expose the contribution of turbulence at different length scales to the processes governing the flow of energy in the wall-normal direction, in scale and among components. The outer-layer turbulence is dominated by very large-scale streamwise elongated modes, which are consistent with the very large-scale motions (VLSM) that have been observed by many others. The presence of these VLSMs drives many of the characteristics of the turbulent energy flows. Away from the wall, production occurs primarily in these large-scale streamwise-elongated modes in the streamwise velocity, but dissipation occurs nearly isotropically in both velocity components and scale. For this to happen, the energy is transferred from the streamwise-elongated modes to modes with a range of orientations through nonlinear interactions, and then transferred to other velocity components. This allows energy to be transferred more-or-less isotropically from these large scales to the small scales at which dissipation occurs. The VLSMs also transfer energy to the wall region, resulting in a modulation of the autonomous near-wall dynamics and the observed Reynolds number dependence of the near-wall velocity variances. The near-wall energy flows are more complex, but are consistent with the well-known autonomous near-wall dynamics that gives rise to streaks and streamwise vortices. Through the overlap region between outer- and inner-layer turbulence, there is a self-similar structure to the energy flows. The VLSM production occurs at spanwise scales that grow with$y$. There is transport of energy away from the wall over a range of scales that grows with$y$. Moreover, there is transfer of energy to small dissipative scales which grows like$y^{1/4}$, as expected from Kolmogorov scaling. Finally, the small-scale near-wall processes characterised by wavelengths less than 1000 wall units are largely Reynolds number independent, while the larger-scale outer-layer processes are strongly Reynolds number dependent. The interaction between them appears to be relatively simple.

Problem of optimization of management of resources distribution of cluster organizational structures for energy-efficient construction

The choice of the optimal strategy for managing the distribution of resources is proposed on the basis of simulation modeling of the plurals of alternative strategies for managing the activities of cluster-organizational structures. The scheme of forming "advisory" models for adaptive management of aggregate structures for different sets of input data is described. The practical significance of the research lies in the fact that the economic and mathematical models for imitation experiments are formed in real time, taking into account the effects of the dynamic stochastic nature of the real environment. The choice of equations for the development of "advisory" models is substantiated. It is shown that imitative simulation based on quasi-linear dynamic econometric equations is able to provide an "advisory" function of supporting the adoption of optimal managerial decisions at different stages and levels, since it provides an opportunity to evaluate key performance indicators of aggregated systems. The adequacy of the models is ensured by the hierarchical structure of the key indicators of the system's operation, which makes it possible to evaluate and forecast the impact of each subsystem as a whole on the degree to which the target function is achieved. The process of identifying a system of key indicators is shown by comparing the characteristics of energy flows and variables of a model. The algorithm for setup parameters of the management model is described in detail. The methods that are planned to be used in decision-support systems are based on the control and analysis of the deviations of the expected values of the key indicators from the actual activity's results of the structure-analogue. The scientific novelty lies in the theoretical substantiation of the prospect of the use of artificial neural networks.

Intelligent Scheduling Optimization of Seasonal CCHP System Using Rolling Horizon Hybrid Optimization Algorithm and Matrix Model Framework

The optimal operation of a combined cooling, heating and power (CCHP) system depends on its structure and adopted energy dispatch strategies. This paper proposes a matrix modeling method for the CCHP system structure, in which multi-energy supply is regarded as the input of system, and cooling, heating, electric load as the output of the system. The energy flow from the system input to output includes the scheduling matrix, the efficiency matrix, and the energy conversion matrix model. Adopt mixed rolling-horizon and particle swarm optimization algorithm to allocation the system scheduling factor to promote optimal operation of CCHP systems. According to the characteristics of input and output energy flow in different seasons of a certain area, the system is simulated and calculated. The results show that the adoption of rolling-horizon optimization for the thermal-electric load in winter can fully calculate the three scheduling strategies and select the optimal strategy in the rolling window. Compared to other methods, the optimization of scheduling factors in summer highlights the low-cost benefits.

Numerical study of structure parameters on energy transfer and flow characteristics of integrated energy recovery and pressure boost device

Numerical study of structure parameters on energy transfer and flow characteristics of integrated energy recovery and pressure boost device

An Energy-Saving Method by Balancing the Load of Operations for Hydraulic Press

Large energy loss caused by mismatching between the installed power and demanded power, as well as the wasted potential energy, is a serious problem for a hydraulic press. In order to reduce the energy loss, an energy-saving method by balancing the load of operations of presses was proposed based on the analysis of energy flow characteristics of the hydraulic system. In the method, the motor pumps in the drive system are shared in different time by a unit composed of two hydraulic presses so that the energy loss caused by unloading operations can be reduced. Furthermore, these two presses are combined, and the excessive energy from one press can serve as the input energy to the other one during some operations to improve the energy efficiency of the drive system, and the potential energy can be utilized directly. Meanwhile, operation durations of these combined presses are optimized for coordination of working processes. The method was applied to two hydraulic presses in a tandem line, and the energy consumption was obtained by quantifying the characteristics of conversion components. Results indicate that for a single press, 36% of electrical energy can be saved in the investigated forming processes.

Wave Directionality in Three-Dimensional Periodic Lattices

This work focuses on elastic wave propagation in three-dimensional (3D) low-density lattices and explores their wave directionality and energy flow characteristics. In particular, we examine the dynamic response of Kelvin foam, a simple-and framed-cubic lattice, as well as the octet lattice, spanning this way a range of average nodal connectivities and both stretching-and bending-dominated behavior. Bloch wave analysis on unit periodic cells is employed and frequency diagrams are constructed. Our results show that in the low relative-density regime analyzed here, only the framed-cubic lattice displays a complete bandgap in its frequency diagram. New representations of iso-frequency contours and group-velocity plots are introduced to further analyze dispersive behavior, wave directionality, and the presence of partial bandgaps in each lattice. Significant wave beaming is observed for the simple-cubic and octet lattices in the low frequency regime, while Kelvin foam exhibits a nearly isotropic behavior in low frequencies for the first propagating mode. Results of Bloch wave analysis are verified by explicit numerical simulations on finite size domains under a harmonic perturbation.

Energy distribution mechanism and open-kinetic-chain characteristics of the upper body system in female volleyball spiking

The aim of this study was to investigate the energy distribution mechanism in volleyball spike movement by assessing the individual contributions of muscular torque and interactive torques of the upper body including gyroscopic, centripetal force, and Coriolis force effects. The spiking movements of seven female collegiate volleyball players were recorded using a three-dimensional motion capture system and an induced power analysis using a link system with 18 degrees of freedom joints to decompose the system’s mechanical energy into causal torque- and force-dependent components. The kinetic energy output of the striking hand at ball impact was 28% (40.7 J) of the system kinetic energy. The decrease in system kinetic energy (−91.3 J) during the early period resulted from the energy absorption mechanism associated with an external joint force component. The energy transfer mechanism, which occurred in the later period, was attributed to a centripetal force effect. Although proximal-to-distal sequential joint rotations were observed in the participants, the quantified data that were calculated using the induced power analysis did not completely agree with the effective energy transfer pattern. These findings indicate that open-kinetic-chain movement–specific task in volleyball spiking likely affected the energy flow characteristics. From the view of energy flow perspective, this study suggests that the volleyball spike movement might have inefficient movement characteristics.

Simulation-based approach to modeling the chip formation energy of polishing process

ABSTRACTPolishing is one typical material removal process, which is widely used for surface processing of porcelain tiles. Due to complex polishing head structure and kinematics features of polishing machine, polishing for porcelain tile is a high energy intensity process. To improve the energy efficiency by optimizing operation, it is essential to establish an energy consumption model for polishing process. This article divides the total energy of polishing process into constant energy and chip formation energy. Furthermore, this article focuses on modeling the chip formation energy for optimizing operation. Based on the energy conversion mechanism and energy flow characteristics, the chip formation energy of polishing process is further divided into three motion energies that govern the abrasive trajectory over the tile surface. A conceptual framework of simulation-based approach is then proposed for modeling chip formation energy of polishing process by integrating the above calculation algorithm of motion energy. Finally, a case study is implemented to illustrate the validation of the proposed approach, and the results show that it is a feasible tool to model the chip formation energy of polishing process and reveal the influence of different process operational parameters.

Development of chaotic advection in laminar flow of a non-Newtonian nanofluid: A novel application for efficient use of energy

The current research aims to investigate energy efficiency and flow characteristics of a non-Newtonian nanofluid containing TiO2 nanoparticles in a chaotic geometry. For this purpose, hydrothermal features of the nanofluid are assessed in the C-shaped channel and compared with the straight channel. Heat transfer and pressure drop in the C-shaped channel are higher than those in the straight channel. This finding is due to intense mixing in the C-shaped channel resulting from chaotic perturbations, such that the velocity and temperature profiles in the C-shaped channel are more uniform than those in the straight one. Convective heat transfer coefficient in chaotic channel has a periodic trend in which it increases in regions where boundary layer is disturbed while decreases in regions where boundary layer is allowed to grow. In comparison with base fluid, applying the nanofluid in both channels presents better cooling along with higher pressure drop. At low Reynolds numbers, development of chaotic advection causes more increment in heat transfer rate in comparison with pumping power and therefore, the value for Figure of Merit (FoM) becomes greater than 1. Simultaneous use of nanofluids and chaotic advection can result in not only greater energy efficiency, but also preventing sedimentation of nanoparticles.

Coordinated Optimal Operation Method of the Regional Energy Internet

The development of the energy internet has become one of the key ways to solve the energy crisis. This paper studies the system architecture, energy flow characteristics and coordinated optimization method of the regional energy internet. Considering the heat-to-electric ratio of a combined cooling, heating and power unit, energy storage life and real-time electricity price, a double-layer optimal scheduling model is proposed, which includes economic and environmental benefit in the upper layer and energy efficiency in the lower layer. A particle swarm optimizer–individual variation ant colony optimization algorithm is used to solve the computational efficiency and accuracy. Through the calculation and simulation of the simulated system, the energy savings, level of environmental protection and economic optimal dispatching scheme are realized.

Numerical simulation of power-engineering complex with torrefaction reactor

The paper presents a mathematical model of power-engineering complex implementing a combined technology of production of power, heat, and solid biofuels, namely, torrefied pellets. Torrefaction of fuel pellets is carried out in a thermochemical reactor by heat from exhaust gases of a gas piston power plant. The results of testing the model by experimental data and the results of calculations of the main characteristics of torrefaction, the mass and energy flows are given. The analysis results of efficiency of the power plant with a build-on thermochemical reactor are reported.

Numerical investigation and experimental development on VM-PT cryocooler operating below 4 K

Vuilleumier coupling pulse tube (VM-PT) cryocooler is a novel kind of cryocooler capable of attaining liquid helium temperature which had been experimentally verified. Depending on different coupling modes and phase shifters, VM-PT cryocooler can be designed in several configurations. This paper presents a numerical investigation on three typical types of VM-PT cryocoolers, which are gas-coupling mode with room temperature phase shifter (GCRP), gas-coupling mode with cold phase shifter (GCCP) and thermal-coupling mode with cold phase shifter (TCCP). Firstly, three configurations are optimized on operating parameters to attain lower no-load temperature. Then, based on the simulation results, distributions of acoustic power, enthalpy flow, pressure wave, and volume flow rate are presented and discussed to better understand the energy flow characteristics and coupling mechanism. Meanwhile, analyses of phase relationship and exergy loss are also performed. Furthermore, a GCCP experimental system with optimal comprehensive performance among three configurations was built and tested. Experimental results showed good consistency with the simulations. Finally, a no-load temperature of 3.39K and cooling power of 9.75mW at 4.2K were obtained with a pressure ratio of 1.7, operating frequency of 1.22Hz and mean pressure of 1.5MPa.

Impact of coiled type inertance tube on performance of pulse tube refrigerator

An inertance tube is widely used to provide a phase shift between mass flow and pressure wave in pulse tube refrigerator (PTR). The inertance tube is usually coiled around the outer surface of a liner compressor or in a reservoir to reduce installation space. The performance of PTR is strongly influenced by different coiled types of inertance tube. Based on 1-D model (DeltaEC) and 3-D model (CFD), a coupling model is proposed to simulate the cooling performance of a PTR. The characteristics of phase shift and energy flow in the PTR are also analyzed in detail. The simulation results show that the phase shift ability of inertance tube would decrease while increasing the number of coiling turns, which would cause the increase of average mass flow rate within the regenerator. Therefore, more PV power would be consumed for the same cooling capacity. In order to improve the cooling performance of the PTR, it is necessary to adjust the length of the inertance tube when it is coiled. At last, the simulation results are verified by the test results.

Eight energy and material flow characteristics of urban ecosystems.

Recent decades have seen an expanding literature exploring urban energy and material flows, loosely branded as urban metabolism analysis. However, this has occurred largely in parallel to the mainstream studies of cities as ecosystems. This paper aims to conceptually bridge these two distinctive fields of research, by (a) identifying the common aspects between them; (b) identifying key characteristics of urban ecosystems that can be derived from energy and material flow analysis, namely energy and material budget and pathways; flow intensity; energy and material efficiency; rate of resource depletion, accumulation and transformation; self-sufficiency or external dependency; intra-system heterogeneity; intersystem and temporal variation; and regulating mechanism and governing capacity. I argue that significant ecological insight can be, or has the potential to be, drawn from the rich and rapidly growing empirical findings of urban metabolism studies to understand the behaviour of cities as human-dominated, complex systems. A closer intellectual linkage and cross pollination between urban metabolism and urban ecosystem studies will advance our scientific understanding and better inform urban policy and management practices.

Energy Analysis of Vehicle Suspension Oscillation Cycle

This article is devoted to conducting the energy analysis of the oscillation cycle in vehicle suspension based on the research of the dynamics equations of the linear single-support single-mass vibrating system with fixed elastic and damping characteristics at harmonic kinematic disturbance. The characteristics of the relative energy flows in the oscillation cycle of the suspension, taking into account the shock absorber inefficient work are received. The physical meaning of the overall characteristic point to the series of the sprung mass amplitude-frequency characteristics is identified. Analysis of vibration isolation properties of the suspension on the sprung mass amplitude-frequency characteristics and the frequency characteristics of the total width of the suspension ineffective work areas in the oscillation cycle is carried out in the damping regulation on the inefficient work areas and on different damping levels.

Transient unidirectional energy flow and diode-like phenomenon induced by non-Markovian environments.

Relying on an exact time evolution scheme, we identify a novel transient energy transfer phenomenon in an exactly-solvable quantum microscopic model consisting of a three-level system coupled to two non-Markovian zero-temperature bosonic baths through two separable quantum channels. The dynamics of this model can be solved exactly using the quantum-state-diffusion equation formalism, demonstrating finite intervals of unidirectional energy flow across the system, typically, from the non-Markovian environment towards the more Markovian bath. Furthermore, when introducing a spatial asymmetry into the system, an analogue of the rectification effect is realized. In the long time limit, the dynamics arrives at a stationary state and the effects recede. Understanding temporal characteristics of directional energy flow will aid in designing microscopic energy transfer devices.

Energy Flow Function and Operational Strategy of CCHP System

The energy flow characteristics of Combined Cooling, Heating and Power (CCHP) system are analyzed in detail and the energy flow function is proposed for its two operational strategies: thermal load dominant mode and electrical load dominant mode. In order to improve its economic and environmental efficiency, an optimal economic and environmental dispatch model is built, which includes the fuel cost, power purchase cost and pollution emission penalty as environmental cost in its objective function and takes the energy flow function as its energy balance equality constraint. Case simulation shows that, the proposed energy flow function and model optimizes the dispatch of CCHP system, reduces the productive cost, improves the environmental efficiency and enhances the energy utilization level.