Energy Loss Coefficient Research Articles

Fault Diagnosis of a Wind Turbine Gearbox Based on Improved Variational Mode Algorithm and Information Entropy.

The working environment of wind turbine gearboxes is complex, complicating the effective monitoring of their running state. In this paper, a new gearbox fault diagnosis method based on improved variational mode decomposition (IVMD), combined with time-shift multi-scale sample entropy (TSMSE) and a sparrow search algorithm-based support vector machine (SSA-SVM), is proposed. Firstly, a novel algorithm, IVMD, is presented for solving the problem where VMD parameters (K and α) need to be selected in advance, which mainly contains two steps: the maximum kurtosis index is employed to preliminarily determine a series of local optimal decomposition parameters (K and α), then from the local parameters, the global optimum parameters are selected based on the minimum energy loss coefficient (ELC). After decomposition by IVMD, the raw signal is divided into K intrinsic mode functions (IMFs), the optimal IMF(s) with abundant fault information is (are) chosen based on the minimum envelopment entropy criterion. Secondly, the time-shift technique is introduced to information entropy, the time-shift multi-scale sample entropy algorithm is applied for the analysis of the complexity of the chosen optimal IMF and extract fault feature vectors. Finally, the sparrow search algorithm, which takes the classification error rate of SVM as the fitness function, is used to adaptively optimize the SVM parameters. Next, the extracted TSMSEs are input into the SSA-SVM model as the feature vector to identify the gear signal types under different conditions. The simulation and experimental results confirm that the proposed method is feasible and superior in gearbox fault diagnosis when compared with other methods.

Marbles and smartphone on physics laboratory: an investigation for finding coefficient of restitution

Experimenting is a basic skill that science students must have. Experimental activities are generally carried out in the laboratory. But by using a smartphone, many experiments can be done outside the laboratory. This research is an example of an experiment using a smartphone that can be carried out outside the laboratory. This study aims to measure the coefficient of marbles restitution through a simple experiment assisted by a smartphone. Marbles are dropped from a certain height, the Phyphox application on a smartphone will record experimental data through a sound sensor. Experimental data recorded through a smartphone is used to analyze the coefficient of restitution and mechanical energy of marble during a collision with the floor. The experimental results show that smartphones can be used to determine the coefficient of restitution and mechanical energy as an experimental tool. We hope that this experiment will be an alternative method for lecturers or physics teachers to demonstrate bouncing objects to determine the coefficient of restitution and mechanical energy loss.

Effect of sputtering power on the first order magnetization reversal, reversible and irreversible process in Fe71Ga29 thin films

We report on the first-order reversal curves (FORC) of magnetization and effect of defects on magnetization process in Fe71Ga29 thin films with different values of sputtering power (50 – 120 W). Phase purity of the thin films was confirmed by grazing incidence X– ray diffraction (GI-XRD). The reversible and irreversible contributions to the magnetization are evidenced through the minor loop parameter such as pseudo hysteresis loss (WF*) and energy loss coefficient (WF0). In particular, the energy loss coefficient is found to decrease from 28 × 106 (A/m. mT) at 50 W to 21 × 106 (A/m. mT) at 120 W, which signifies a decrease in domain wall resistance. FORC infers narrow switching, which leads to low coercivity distribution at 120 W as a result of less defects.

Numerical study on the biomimetic trailing edge in the environment of a high-pressure turbine stage

In this study, the whisker structure of a harbor seal is applied to the trailing edge of a high-pressure turbine stage to reduce energy loss. The method to produce biomimetic geometry is provided. Two cases are studied in this paper including a prototype of a high-pressure turbine stage and this stage with the biomimetic trailing edge. The delayed detached-eddy simulation (DDES) method is used to simulate the flow of the stages. The energy loss coefficient of the turbine stage with the biomimetic trailing edge is significantly reduced. The analysis of the local entropy generation rate shows that the wake loss of the biomimetic stage and the loss in the blade passage are greatly reduced. Two reasons for the widening of the wake of the prototype vane during the downstream movement are analyzed. For the biomimetic stage, the Karman vortices are completely suppressed and transformed into small vortices with strong three-dimensional motion. The wake width of the biomimetic trailing edge is narrowed and the speed recovery becomes faster. This leads to the reduction of the wake loss and the interaction between the wake of the vane and the downstream blade.

Theoretical and experimental investigations of mechanical vibrations of hot hammer forging

The characterization of mechanical vibrations in a hammer forging process is a tremendously important parameter for machine design and production engineering. The dynamic response of a forging hammer to the reaction forces is affected by material behaviour, time, spring-damper system and foundation. In this research firstly, the effect of mass ratio and coefficient of restitution on the forging efficiency were theoretical characterized. The interesting influence of anvil initial velocity on the forging efficiency is also analytically presented. The mechanical vibrations of a LASCO HO U-315 hammer were experimentally investigated. Two steel grades a S355 and a 42CrMo4 were used to forge trial parts. The velocity of the ram and acceleration of the anvil during a hot die forging process were measured using a laser velocity meter type LSV-2000-45. The influences of forging time, coefficient of restitution, energy loss and time interval (delay) between blows on the efficiency of the forging process were examined. The energy loss before die contact was determined to be approximately 10%. The investigations also showed that a variation of the time interval between blows within the usual range has no effect on the intensity of the vibrations of the anvil nor on the energy loss of the hammer. The dependence of the free damped vibrations of the anvil on machine stiffness, damper coefficient and mass of machine has been confirmed. Additionally, the loss of energy due to hammer movement as well as the free damped mechanical vibrations of the anvil were theoretically analysed in order to verify the experimental findings. Theoretical analysis showed an anvil initial velocity of approximately 0.2 m/s results in a 4% increase of forging efficiency. A good agreement between the experimental and theoretical results was observed.

Correction and laboratory investigation for energy loss coefficient of square-edged orifice plate.

A lot of studies have shown that the hydraulic characteristics of orifice plate are mainly controlled by its contraction ratio, but the thickness of square-edged orifice plate also has many impacts on energy loss characteristics. The primary objective of this study was to investigated the effects of square-edged orifice plate thickness on energy loss characteristics. In this paper, the effects of square-edged orifice plate thickness on energy loss characteristics are investigated by numerical simulation using CFD. Orifice plate discharge tunnel is axial symmetric, two dimensional numerical simulations of orifice plate discharge tunnel flow was used. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed. The results of the present research demonstrate that energy loss coefficient decreases with increase of the orifice plate thickness. The results of model experiment are consistence with the results calculated by using rectified equation in present paper. The CFD simulations and Model experiment for the flow through an orifice plate are carried out. For square-edged orifice plate energy dissipater, the relative orifice plate thickness T/D has remarkable impacts on its energy loss coefficient ξ. The Traditional equation (8) is corrected by numerical results. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed and this equation is available in the condition of d/D = 0.4-0.8, T/D = 0.05-0.25, and Re > 105(Re is Reynolds number). Comparing with the physical model experimental data, the relative errors of equation (9) is smaller than 15%.

Unified Wall Function and Application for Steady Turbulent Pipe Flow with Uniform Wall Roughness

A newly developed wall function for the velocity-profile of steady turbulent flow in various hydraulic regimes near rough walls was created. The wall function was then applied into two approaches to obtain the total flow energy loss (mechanical energy loss) of turbulent pipe flow. The energy loss values calculated through the above two approaches both predicted the experimental results well. The energy loss coefficient calculated through the second approach gave a more precise definition of the total flow characteristics than the Manning roughness coefficient as it was proved to be a function of the field statistics. It was furtherly found that this energy loss can be decomposed into the energy loss due to dissipation caused by molecular viscosity and the dissipation of turbulent kinetic energy, and that its density distribution falls mainly into the near-wall region.

Topologically Enhanced Dual-Network Hydrogels with Rapid Recovery for Low-Hysteresis, Self-Adhesive Epidemic Electronics.

Dual-network conductive hydrogels have drawn wide attention in epidemic electronics such as epidemic sensors and electrodes because of their inherent low Young's modulus, high skin-compliance, and tunable mechanical strength. However, it is still full of challenges to gain a dual-network hydrogel with high stretchability, low hysteresis, and skin-adhesive performance simultaneously. Herein, to address this issue, a novel dual-network hydrogel (denoted as PAa hydrogel) with polyacrylamide as the first network and topologically entangled polydopamine as the secondary network was prepared through a facile gel-phase in situ self-polymerization and soaking treatment. Benefiting from the topological enhancement as well as the synergetic effects of hydrogen bonds and metal coordination bonds, low modulus (∼10 kPa), excellent stretchability (1090.8%), high compression (90%), negligible hysteresis (η = 0.019, energy loss coefficient), rapid recovery in seconds, and self-adhesion are obtained in the PAa hydrogels. To demonstrate their practical use, a states-independent and skin-adhesive epidemic sensor was successfully attached on human skin for motion detection. What is more, by using the hydrogel as an epidemic electrode, electromyogram signals were accurately detected and wirelessly transmitted to a smart phone. This work offers a new insight to understand the strengthening mechanism of dual network hydrogels and a design strategy for both epidemic sensors and electrodes.

Effects of free heave motion on wave resonance inside a narrow gap between two boxes under wave actions

Fluid resonance inside a narrow gap between two side-by-side boxes is investigated based on an open-source CFD package, OpenFOAM. An upstream box heaves freely under wave actions and a downstream box remains fixed. The focus of this work is to study the influence of the motion of the upstream box on the hydrodynamic behavior of the resonant fluid inside the gap. The hydrodynamic behavior considered in this study includes the wave height inside the gap, heave displacement and their harmonic components, and reflection, transmission and energy loss coefficients. For comparison, the configuration in which the two boxes are fixed is considered. It was found that the heave motion of the upstream box increases the fluid resonant frequency and significantly reduces the resonant wave height in the gap. The frequencies at which the maximum and minimum heave displacements of the upstream box are observed to obviously deviate from the fluid resonant frequency. For the wave height in the gap and heave displacement, the effects of the incident wave height on their harmonic components are different. The heave motion of the upstream box results in a larger reflection coefficient and smaller energy loss coefficient.

Emulsion-templated flexible epoxy foams

Flexible epoxy foams were successfully prepared by curing medium internal phase emulsions (MIPEs) with a continuous organic phase containing epoxy resin and hardener, surfactant and carbon nanotubes and an aqueous internal phase. Curing the MIPEs at ambient temperature resulted in interconnected polyepoxide foams with average pore size of about 10 μm, while curing the MIPEs (with carbon nanotubes as a thickening agent) at 50 °C resulted in epoxy foams with pore sizes of one magnitude higher. The polyepoxide foams were compressible up to a strain of 70% of their original height and did not fracture. The polyepoxide foams were resilient with energy loss coefficients ranging from 40% to 60%, representing their energy adsorption during cyclic loading.

Formula on energy loss coefficient considering the difference in flow rate of three inflow pipes of a four-way circular manhole at a crossroads

Formula on energy loss coefficient considering the difference in flow rate of three inflow pipes of a four-way circular manhole at a crossroads

THEORETICAL STUDY OF THE CLOSED BAR LOOS FACTOR

The coefficient of vibrational energy loss is a physical and mechanical characteristic, the accuracy of calculation of vibroacoustic characteristics of corresponding machines at the stage of their design to a great extent depends on its value.

REGRESSION ANALYSIS OF THE COEFFICIENTS OF VIBRATION ENERGY LOSSES IN GAS-DISCHARGE SYSTEMS OF POWER PLANTS

Within the framework of this article, an experiment was conducted to determine the coefficient of energy loss of oscillatory motion. The analysis of the behavior of the frequency dependence of the coefficient showed that the approximation by a polynomial of degree 7 gives the most approximate result to the experimental values. The standard deviation of the experimental data from the polynomial is consistent with the error of the experimental data.

New analytical solutions of oblique wave scattering by submerged horizontal perforated plates using quadratic pressure drop condition

This study develops new analytical solutions for oblique wave scattering by horizontal perforated plates submerged below the water free surface using a quadratic pressure drop boundary condition. Both kinds of submerged plates are considered: a) A horizontal perforated plate as an offshore breakwater; b) A horizontal perforated plate attached to a vertical wall as a wave absorber. The velocity potential decomposition method combined with an efficient iterative algorithm is adopted to obtain the analytical solutions, and the hydrodynamic parameters of engineering interest for the reflection, transmission and energy-loss coefficients as well as the vertical wave force are considered. A new simple formula for predicting the discharge coefficient in the quadratic pressure drop condition, which is critical to make the analytical solutions to be practically applicable, is developed by fitting the analytical results and an amount of experimental data in literature. The present analytical solutions are in good agreement with previous analytical solution for special case and the numerical results of an independently developed multi-domain boundary element method solution. The reflection and transmission coefficients calculated by the present analytical solutions are also in good agreement with experimental data when adopting a well-predicted discharge coefficient. The present analytical solutions are valuable for fast assessing the hydrodynamic performance of horizontal perforated plates in the initial stage of engineering design. The present analytical model can also be readily extended to the multi-layer horizontal perforated plates and similar structures.

A Semi-Analytical Potential Solution for Wave Resonance in Gap Between Floating Box and Vertical Wall

Based on potential flow theory, a dissipative semi-analytical solution is developed for the wave resonance in the narrow gap between a fixed floating box and a vertical wall by using velocity potential decompositions and matched eigenfunction expansions. The energy dissipation near the box is modelled in the potential flow solution by introducing a quadratic pressure loss condition on the gap entrance. Such a treatment is inspired by the classical local head loss formula for the sudden change of cross section in channel flow, where the energy dissipation is assumed to be proportional to the square of local velocity for high Reynolds number flows. The dimensionless energy loss coefficient is calibrated based on experimental data. And it is found to be insensitive to the incident wave height and wave frequency. With the calibrated energy loss coefficient, the resonant wave height in gap and the reflection coefficient are calculated by the present dissipative semi-analytical solution. The predictions are in good agreement with experimental data. Case studies suggest that the maximum relative energy dissipation occurs near the resonant frequency, which leads to the minimum reflection coefficient. The horizontal wave forces on the box and the vertical wall attain also maximum values near the resonant frequency, while the vertical wave force on the box decreases abruptly there to a small value.

Wave scattering by inverted trapezoidal porous boxes using dual boundary element method

A numerical model is developed based on the dual boundary element method (DBEM) to solve the problem of surface gravity waves past multiple floating inverted trapezoidal porous boxes under the framework of linear potential flow theory. The continuity of velocity and semi-empirical quadratic pressure drop equation is adopted on the porous boundary to incorporate the effect of incident wave amplitude on the energy loss coefficient. Various results by an array of inverted trapezoidal porous boxes are discussed in the form of scattering coefficients (wave reflection, transmission, and energy loss coefficients), and force coefficients (horizontal force, vertical force, and moment). The verification of the numerical model is carried out by an independently developed multi-domain boundary element method (MBEM) code, and also with results available in the literature. The study reveals that, in most cases, the long waves exhibit insignificant hindrance whereas intermediate waves delineate the harmonic oscillations and deep water waves feel maximal hindrance by inverted trapezoidal porous boxes. The wave damping of KL≥0.95 is obtained for structural width B/λ≥0.66 by a pair of identical inverted trapezoidal porous boxes. The angle of porous wings is helpful to alter the scattering coefficients and also helps in the fine-tuning of force coefficients. The angle of partially open wings within 300≤θ≤600 is suggested along with structural porosity μ=0.25 for effective constriction of incident waves. The parametric analysis will be useful in the meticulous design of cost-effective breakwaters.

Hydrodyamic Efficiency of Double Pontoon Supported on Piles (Dept.C)

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Design development of porous collar barrier for offshore floating fish cage against wave action, debris and predators

This paper presents a design concept of a porous collar barrier for a novel floating open-net fish cage that is integrated with a floating spar wind turbine (referred to as COSPAR fish cage). The COSPAR fish cage has an octagonal shape with each side length of 30m. The collar barrier, having an array of rectangular cut-outs with round corners, is installed at the top portion of the cage to attenuate wave transmission inside the cage as well as to protect fish from external predators and debris. Single and double collar barrier designs corresponding to single net and double net cages are studied. The wave transmission, reflection and energy-loss coefficients of barriers are determined from numerical analysis based on the linear potential wave theory and the eigenfunction expansion method. Various underwater heights (2m ≤ h ≤ 8m) and porosity (0.25≤ ε ≤ 0.75) of the collar barriers are examined with the view to obtaining the barrier design for minimal transmission coefficient and energy-loss coefficient. Without a collar barrier, the single net and double net cage can only provide average wave transmission coefficients of 0.9 and 0.8, respectively. This study finds that the transmission coefficient could be reduced below 0.4 by having a single collar barrier with h = 4m and ε = 0.25. On the other hand, the transmission coefficient could be further reduced below 0.3 by a double collar barrier with the same h and ε. In addition, the double collar barrier gives lower energy-loss coefficient and better proofing against fish escape, biosecurity and predator intrusion than the single collar barrier. A double collar barrier design with porosity combination of ε1 = 0.25, ε2 = 0.5 is recommended for the COSPAR fish cage as it yields competitive wave scattering performances and saves collar material by 25 % when compared with the best performing porosity combination of ε1 = ε2 = 0.25.

Application of an improved variational mode decomposition algorithm in leakage location detection of water supply pipeline

In the research of pipeline leak location, signal decomposition can be used to extract effective leak signal components. Variational mode decomposition (VMD) can decompose a complex non-stationary signals into several simple band-limited intrinsic mode functions (BLIMFs). However, the number of modes K and the quadratic penalty item α need to be preset before using VMD, which brings limitations to VMD. Therefore, an improved adaptive VMD (IAVMD) is proposed in this paper. This method can adaptively determine the quadratic penalty item α for each BLIMF according to the frequency characteristics of the signal. Meanwhile, the energy loss coefficient and the correlation of adjacent BLIMFs is regarded as an evaluation index to determine the best number of modes K. Finally, this method is used to locate the leak location of water pipelines, which can significantly improve the positioning accuracy.

Energy and exergy analysis of corrugated plate solar collector by forced convection using two different absorber plate material

In this paper, the experimental analysis of two types of corrugated plate solar collector (CPSC) using water as working fluid has been done. Two similar designs and dimensions of CPSC but different materials of absorber plates have been investigated, the collector1 is copper and collector 2 is aluminium. The performance of energy, exergy and total heat loss coefficient of CPSC were analysed and compared. Thermal performance of CPSC depends on many parameters such as outlet collector temperature, absorber plate temperature, temperature difference, inlet collector temperature, atmospheric temperature, mass flow rate (MFR), solar radiation, wind speed and absorber plate material. The three MFR values of 0.0167 kg/s, 0.025 kg/s and 0.033 kg/s were considered in this experimental setup. The thermal performances of these two types of solar collectors were investigated. Also, a comparison between the performance of these two types of solar collector at various MFR was done. Experimental results show that the use of copper-based CPSC could improve the thermal efficiency compared to the use of aluminium based CPSC. The maximum energy and exergy of copper and aluminium based CPSC was found at MFR 0.033 kg/s. Results show that as the water MFR is increased from 0.0167 kg/s to 0.033 kg/s, the thermal efficiency of collector made of copper and aluminium increases.