Axial Energy Research Articles

Influence of circular and annular pupil function on Axial Point Spread Function of optical system

The paper presents an analysis of influence of shape and transmissivity of a pupil of an optical system on an axial energy distribution while the optical system images axial point. Therefore, a depth of focus is studied. Specifically, the analysis is done for uniform illumination of a circular pupil, and for the circular and annular pupil in the case of Gaussian amplitude distribution. Analytical formulas for Point Spread Function and Axial Point Spread Function are described, and characteristics of properties of the depth of focus of the optical system are derived. The novel analytic formulas presented in the paper can be used for determination of the value of the depth of focus of the optical system for given threshold limit of normalized axial intensity.

Thermal rectification in asymmetric two-phase nanowires

Thermal rectification based on a new strategy of nanostructuration has been assessed with nonequilibrium molecular dynamics and wave-packet propagation simulations. The use of asymmetric crystalline-core/amorphous-conical-shell nanowires creates a direction-dependent thermal conductivity due to variable axial and radial phonon propagation/confinement. The origin of this effect is related to the combination of a crystalline/amorphous interface parallel to the heat flux, together with the variable amount of amorphous coating due to the conical shell of the nanowire. Physical insights of the rectification are given by the mean free path of phonons, the axial and radial energy transfer, the energy diffusivity, and the vibrational density of states restricted to different constitutive elements of the nanowire.

Effect of length of outer electrode on plasma characteristics in coaxial gun

The dense plasma produced by a coaxial gun possesses an extremely high velocity (~100 km/s), electron density (~10<sup>16</sup> cm<sup>–3</sup>) and energy density (~1 MJ/m<sup>2</sup>), which has great potential applications in fusion energy, astrophysics and aerospace physics. Through the measurements of electrical and optical signals, as well as the temporal and spatial evolution of the ejected plasma, the plasma characteristics of two different outer electrodes in length are investigated. As the outer electrode is lengthened, the axial velocity, the collimation and the propagation distance of plasma are all enhanced while the electron density and the optical intensity decrease, this can be ascribed to the extension of plasma column formed by <i>Z</i>-pinch on the central electrode during the discharge. When moving across the end of the inner electrode, the plasma sheet can be stretched into a bow shape due to the Coulomb and Lorentz force. With the appearance of axial current, part of the plasma sheet near the head of the inner electrode converges toward the center, and then generates a plasma column with much higher electron density and temperature. On the one hand, the extending of the plasma column can match the outer electrode in length and therefore the plasma column gains longer accelerating time in the coaxial gun resulting in the growing of ejected velocity. On the other hand, it also brings higher losses of the charged particles and recombination rates between the plasma and the wall of electrodes, resulting in the decrease of electron density and optical intensity. Moreover, the axial kinetic energy, the electron density and the radial Lorentz force of ejected plasma are jointly responsible for the collimation and the attenuation characteristics in its propagation. As the axial velocity and electron density increase, the axial kinetic energy of ejected plasma increases, which induces a longer propagating distance. In contrast, with the electron density and radial Lorentz force growing, the density gradient and thermal expansion of ejected plasma are enhanced correspondingly, leading the energy density to decrease and finally the propagating distance to shorten. In conclusion, a high collimation plasma jet trends to generate in a high axial velocity, electron density and with a relatively long outer electrode.

Stagnation Point Flow of EMHD Micropolar Nanofluid with Mixed Convection and Slip Boundary

The aim of this numerical research is to study the stagnation point flow of the electrical magnetohydrodynamic micropolar nanofluid with slip conditions past a stretching sheet. The phenomenon of linear thermal radiation, Ohmic and internal heating, has also been considered in the energy equation. The modelled PDEs are converted into ODEs via similarity transformation, and converted ODEs are tackled via the shooting technique. The features of assorted parameters on the axial and angular velocities and energy and concentration fields are sketched. The numerical values of the Sherwood and Nusselt numbers have been computed numerically and displayed in the form of tables. Our analysis shows that the heat transfer rate is decreased as the thermal slip parameter and the diffusion slip parameter are enhanced. The present study illustrates that the energy and concentration distribution are decreased with each of the mass free convection parameter, stagnation parameter, and thermal free convection parameter.

Axial Compression Performance of Square Tube Filled with Foam Aluminum

As a typical buffer energy absorbing structure, thin-walled tube filled with foam aluminum has good mechanical properties and energy absorption characteristics. Therefore, the axial compression performance of square tube and foam aluminum filled square tube was experimentally studied by quasi-static mechanical loading method. On the basis of the existing experimental research and theoretical analysis, the strain rate is introduced into the dynamic compression theory, and the mathematical model of the average crushing load of foam aluminum filled square tube under the axial quasi-static and impact loads is obtained. By comparing the theoretical results with the simulation results, the relative error of quasi-static and impact state is 2.8% and 8% respectively. This paper not only proves that foam aluminum filling can significantly improve the bearing capacity and energy absorption performance of square tube structure in the axial compression process, but also provides a more specific theoretical basis for the axial compression energy absorption design of square tube filled with foam aluminum.

Appendix gap losses in Stirling engines – review of recent findings

The appendix gap loss in Stirling cycle machines is generated by the annular gap around the thermally insulating, thin-walled dome typically attached to a piston or displacer plunging into the hot cylinder volume of an engine or the cold volume of a cryocooler. It was considered to be of minor importance for decades. Thus, simplified analytical models were considered sufficiently accurate for its description, until numerical simulations and experimental results gave rise to a more detailed analysis revealing that, neglecting entrance and end effects, the flow is typically laminar, but unsteady. Subsequently, an enhanced analytical model accounting for fluidic and thermal inertia effects as well as the volumetric displacement by the seal was developed. Compared to the previous ones, this model predicts a shift of the optimum width to smaller values, a higher minimum overall loss and furthermore, an option to decrease the loss by reducing the effective seal diameter. This could be experimentally confirmed as well as the unsteady gas temperature profiles predicted by this model. Subsequently, both theoretically and experimentally founded correlations for the radial and axial energy transport in the gap were derived and implemented in a differential simulation of the gap within a third order code.

Particularities of spatial kinetics of hybrid thorium reactor installation containing the long neutron source based on magnetic trap

In this work, we study the features of the spatial kinetics of installation as a hybrid thorium reactor with an elongated plasma neutron source based on a magnetic trap. The active zone of the installation under study consists of an assembly of hexagonal fuel blocks of a unified design and a long solenoid with a high-temperature plasma column passing through the axial region of the core. Combining engineering expertise in creating nuclear reactors with a physics-technical potential for obtaining high-temperature plasma in a long magnetic trap we ensure the solution of the multidisciplinary problem posed. These studies are of undoubted practical interest, since they are necessary to substantiate the safety of operation of such hybrid systems. The research results will allow optimizing the active zone of the hybrid system with leveling the resulting offset radial and axial energy release distributions. Results of our study will be the basis for the development of new and improvement of existing methods of criticality control in related systems such as “pulsed neutron source – subcritical fuel assembly”

Large eddy simulation of compressible round jets with coflow

Large eddy simulations of subsonic round jets are carried out using high order compact finite difference scheme and an explicit filtering based approximate deconvolution method. The jets have a Mach number of 0.9 and Reynolds number of 4.5×105 based on jet diameter and centerline velocity at inflow. Results obtained for the mean flow and turbulence intensities agree well with those in existing literature. We also study the effects of co-flow velocity ratio on the flow physics. Increase in potential core length and decrease in spreading rate of jet is observed in the presence of co-flow. The effects of co-flow velocity ratio on the axial Reynolds stress and turbulent kinetic energy budgets are also presented. It is observed that increasing co-flow velocity ratio leads to reduction in the turbulence intensities and near-field sound levels.

Improved Modal Strain Energy Decomposition Method for damage detection of offshore platforms using data of sensors above the water level

Offshore structures usually are implemented in harsh environmental conditions which make the structures disposed to different failures. Negligible failures may lead to catastrophic ones. To prevent potential catastrophic failure, development of robust damage detection methods for offshore structures is necessary. Damages change structure's dynamic characteristics. Among different dynamic characteristics, modal frequencies and mode shapes are utilized more often. Due to various problems regarding damage detection methods for offshore structures such as sensor installation and data acquisition in water, damage detection methods using limited sensors seems very vital. In this paper, a novel method called Improved Modal Strain Energy Decomposition Method (IMSEDM) is developed to detect structural damage of jacket-type offshore platforms using a limited number of sensors just above the water. The proposed method has two main contributions. The first is simultaneous use of both modal frequencies and mode shapes which make damage detection more accurate. The second is decomposition of modal strain energy into axial and bending. IMSEDM locates damaged elements by considering the impacts of the damage on axial and bending modal strain energy. The method is evaluated using an experimental jacket type offshore platform. The results confirm that IMSEDM can effectively detect damages with incomplete data.

On different kinetic approaches for computing planar gas expansion under pulsed evaporation into vacuum

The numerical study of one-dimensional gas expansion under pulsed evaporation into vacuum is carried out on the basis of the direct simulation Monte Carlo method, the exact Boltzmann kinetic equation, and the S-model kinetic equation. The results are presented for various levels of evaporation intensity, defined by the amount of evaporated material. Special attention has been paid to the calculation of the average axial energy of particles, the velocity vector of which deviates from the axis by no more than a small prescribed angle α. This characteristic of the flow is important for analysis of time-of-flight distributions in pulsed laser ablation. It is found that for intense evaporation, the average axial energy has a maximum as a function of time. The presented results allow us to establish the relative accuracy of the considered kinetic approaches for various flow regimes.

Study on energy distribution characteristics of cyclone in Laval nozzle

Supersonic separator is a device for dehydrating and separating heavy hydrocarbons in natural gas. Laval nozzle and cyclone in the separator have a great influence on the separation efficiency. At present, there are few studies on the energy distribution characteristics of the cyclone, and the law of the influence of cyclone on subsonic and transonic flow fields is not clear. Based on numerical simulation, the paper studies the influence of gas-liquid density on the separation performance of the separator, studies the energy distribution characteristics of methane flow in Laval nozzle under subsonic and transonic velocities, and deduces the energy equation containing axial kinetic energy term and radial kinetic energy term in the nozzle. The results show that the gas-liquid density has some effects on the separation efficiency of the separator. The distribution of tangential velocity and tangential kinetic energy in the nozzle is similar before the cyclone along the axis, but after the cyclone, the distribution of tangential velocity and tangential kinetic energy is significantly different. The proposal of tangential kinetic energy has important guiding significance to the structure design of supersonic separator.

Structural Behavior of RC Columns Improved by Different Strengthening Techniques

Abstract Deficient or deteriorating reinforced-concrete columns in many existing structures have to be strengthened using economical, efficient, and fast methods. In the present study, different strengthening techniques to improve the load-carrying capacity of reinforced concrete (RC) columns have been compared. Five groups of fifteen square reinforced concrete columns (150 mm × 150 mm × 600 mm) and one group of three circular columns ( φ 170 mm) that have cross-sectional areas equivalent to those of the square columns were cast from normal-strength concrete. The test program was designed to examine the behavior of columns strengthened by carbon fiber-reinforced polymer (CFRP), steel jacketing, ferro cement, steel fibers, and silica fumes under cyclic axial compression. The efficiency of each strengthening method in increasing the column’s axial capacity, energy absorption, and ductility was studied using the experimental data. The test results showed that strengthening the columns could significantly enhance their load-carrying capacity and failure strains.

Axial compression deformability and energy absorption of hierarchical thermoplastic composite honeycomb graded structures

Thermoplastic composites have advantages of high damage tolerance, reprocessing and recycling capacities which are in growing demand in lightweight engineering applications. Structural gradient were introduced to designed continuous woven glass fiber reinforced hierarchical thermoplastic composite honeycomb graded structures (HTCHGS) aim to improve on deformation stability and induce the failure processes. Axial compression tests were conducted to investigate compression behavior, energy absorption capacity and influence of structural gradient distributions. Experimental observation showed that failure of HTCHGS was induced and constrained as expected, stable rising load plateau achieved by presented staggered conical HTCHGS. The staggered conical HTCHGS obtained mean value of 0.64 and 1.56 J/g on crushing force efficiency and specific energy absorption at the densification displacement. FEM simulations were carried out among presented configurations by parameterized modeling, validated the induced deformation processes by structural gradient which matched well with the tests. Stress distributions were compared among six configurations at typical deformation stage, found core components of staggered configurations contribute more to energy absorption than that of regular configurations. Staggered dumbbell HTCHGS provide long and stable deformation plateau till densification, and staggered conical HTCHGS are considered as optimal energy absorbing components among the configurations which give possible guidance for engineering structural designs.

Hydrodynamic Analysis of Horizontal Axis Tidal Current Turbine under the Wave-Current Condition

To take advantage of the high tidal current velocity near the free surface, the horizontal axis turbine is installed, which inevitably causes hydrodynamic characteristics to effect the turbine by the waves. In this article, we established a numerical calculation method for the hydrodynamic load of a horizontal axis turbine under wave-current conditions. Based on the numerical calculation results, the hydrodynamic loads were decomposed and the influence rules of wave parameters and blade tip immersion depth on the hydrodynamic load were obtained. The study found the following: (1) the multi-frequency fluctuations based on the rotation frequency and incident wave frequency occurred in instantaneous values of the axial load coefficients and energy utilization ratios, and the fluctuation amplitude decreased with the increase of the blade tip immersion depth; (2) the fluctuation amplitude, according to rotation frequency, changed less with the increase of wave period and wave height, and was smaller according to wave frequency; (3) the fluctuation amplitude based on wave frequency increased linearly with the increase of wave height and wave period. The research results can provide the basis and reference for the design and engineering application of tidal current power station.

Theoretical Model of Radial Scattering Velocity of Fragments of the Reactive Core PELE Projectile

PELE projectile is a new type of armor-piercing warhead and has a more obvious fragmentation effect, which solves the problem of insufficient after-effects of conventional armor-piercing projectiles. Reactive material is a new type of energetic material, which has some characteristics similar to the traditional explosives but has better mechanical properties. Reactive material is insensitive under normal conditions, and it can release huge energy under external impact loading. This paper hopes to study the application of reactive materials to the inner core of PELE projectiles to further improve the fragmentation effect of PELE projectiles. The fragmentation effect of PELE projectile is mainly reflected in the radial scattering velocity of fragments after it perforates the target plate. In this paper, three energy sources for the radial scattering of fragments were obtained by analyzing the penetration process of PELE projectile, that is, the axial kinetic energy of outer casing, the radial compression potential energy generated by the inner core to the outer casing, and the chemical energy released by the reactive core material. Based on the simplification and assumptions, the theoretical model of radial scattering velocity of fragments of the reactive core PELE projectile was established. In addition, numerical simulations were carried out to verify the theoretical model. The results show that the numerical simulation results are in good agreement with the theoretical calculation results, which indicates that the model established in this paper is scientific and reasonable. The reactive core PELE projectile has a more significant fragmentation effect, which further enhances the comprehensive damage power of traditional PELE projectile. The theoretical model established in this paper can quickly assess the power of reactive core PELE projectile’s fragmentation effect, which can be used to provide guidance and reference for engineering application.

Measurements of axial energy loss from magnetic mirror trap

The work represents a next step in studies of longitudinal energy losses from linear magnetic plasma confinement devices. The paper describes the experimental technique that has been developed and used to measure the absolute values of longitudinal particle and energy density fluxes from an open magnetic mirror trap. Using this technique, it was possible to measure and account for the secondary electron emission coefficient from plasma-facing end plate, and perform a comparison with the existing theory of energy confinement in open traps. It is shown that the average energy transported by an ion-electron pair leaving the trap is close to theoretically predicted minimum value of 6–8 electron temperatures. As confirmed by the measured dependencies, this conclusion is valid in a broad range of parameters and the threshold value of the magnetic expansion ratio does not exceed its theoretically predicted minimum of .

Characterization of a smart transducer for axial force measurements in vibrating environments

The possibility to harvest energy from ambient sources and to measure additional physical quantities at the same time and by a single device is of great interest in the context of “industry 4.0”. In this paper, we present a smart electromagnetic energy transducer that performs two tasks simultaneously: measurement of axial forces and energy harvesting. The proposed device is completely passive and able to operate in vibrating environments having very weak amplitudes even less than 0.5 mm. In response to kinetic energy coming from environmental vibration, the electromagnetic transducer is able to operate as an energy scavenger and as a measurement system of the applied axial force as characteristic property of the source itself. The sensor system, presented in this paper, is also capable to transmit the measurement data through an optical fiber without necessity of supplementary active conditioning circuits. The system has been designed, analytically modeled and a laboratory prototype has been realized. An extensive experimental investigation has carried out to show the performance assessment of the overall system and the metrological characterization of the measurement functions.

Reynolds-Averaged Simulation of the Fully Developed Turbulent Drag Reduction Flow in Concentric Annuli

AbstractReynolds-averaged modeling is performed for polymer-induced drag reduction (DR) fluid at the fully developed turbulent regime in a concentric annulus by using the commercial code, ansys-fluent. The numerical approach adopted in this study relies on a modified k–ε–v2¯–f model to characterize the turbulence and the finitely extensible nonlinear elastic-Peterlin (FENE-P) constitutive model to represent the rheological behavior of the polymer solution. The near-wall axial velocity, Reynolds stress, and turbulent kinetic energy (TKE) budget near both walls of the annulus (fixed radius ratio of 0.4) are compared in detail at a constant Reynolds number (Re=10,587) and various rheological parameters (Weissenberg number We in the range of 1–7 and the maximum polymer elongation L = 30 and 100). Current simulation has predicted the redistributions of turbulent statistics in the annulus, where the two turbulent boundary layers (TBLs) of the DR flow differ more compared to those of its Newtonian counterpart. The difference is also found to be highly dependent on the rheological properties of the viscoelastic fluid.

Study on Loading Rate Dependence of the Coal Failure Process Based on Uniaxial Compression Test

To study the influence of the loading rate on the failure process of coal, uniaxial compression tests were performed with various axial strain rates of 0.83 × 10–5 to 6.66 × 10–5 s−1 on coal samples, which were collected from the Shamushu Coal Mine in Sichuan Province. The parameters of stress, strain, and acoustic emission during the failure process were collected and recorded. The peak stress, axial strain stiffness, energy dissipation, and acoustic emission characteristics of coal samples with different axial strain rates were analysed. The results demonstrate that (1) as axial strain rates increase, the peak strength and degree of fragmentation of the coal sample after failure also increase, and they exhibit good dependence on the axial strain rate; (2) the axial strain rate has little influence on the change trend in strain stiffness during the process of failure, but as the axial strain rate increases, the strain stiffness value of the horizontal section of the axial strain stiffness curve increases, and the initial stress level of this stage has a forward trend; (3) as the axial strain rate increases, the total energy absorbed by the coal sample increases gradually, and the proportion of elastic strain energy decreases when the peak stress is reached, while the proportion of dissipated energy increases gradually; (4) as the axial strain rate increases, the AE signal’s activity increases in the process of sample failure, the threshold value of the strain level decreases corresponding to AE active and intense periods, and higher amplitude AE signals are produced in the violent period. The research results can provide reference for monitoring and controlling geological hazards, such as pillar instability and failure in underground mining.

Method to Determine the Impact Strength of Triple‐Base Gun Propellant Based on Strain Energy Density

AbstractA method to obtain the impact strength of triple‐base gun propellant is proposed according to strain energy density. Using a drop‐weight impact testing machine, the impact strengths of DAGR125‐21/19 gun propellant at room temperature (20 °C) and low temperature (−40 °C) were studied. In the experiments, there were different impact energies via changing the drop weight or height. The surface images of gun propellants during the impact process were captured using a high‐speed camera. The deformation of DAGR125‐21/19 gun propellant was calculated through digital image correlation method (DICM). After analyzing the surface images and deformation, it was found that there was a good agreement between the maximum of axial nominal strain energy density (ANSED) and initial fracture point. Finally, the impact strength of DAGR125‐21/19 gun propellant was obtained through calculating the strain energy density during the plastic stage between the yield and initial fracture points. Moreover, successive parallel and replication experiment results proved the rationality and feasibility of the proposed method to determine the impact strengths of DAGR125‐21/19 gun propellant at room temperature (20 °C) and low temperature (−40 °C).