In this paper, a theoretical model for diffusion in Lennard-Jones fluids over a larger density range is proposed. Instead of looking at molecular transport in real space, we treat molecular transport ...in radial distribution function space. Specifically, the radial distribution function, which reflects the static properties of the system, is used to calculate the mean free path of molecules, a key physical quantity for diffusion modeling. Then, on the basis of the rarefied hard sphere gas diffusion model, and with consideration of the correction of collision frequency and backscattering effect caused by the higher density, the expression of self-diffusion coefficient in Lennard-Jones fluid is obtained. Molecular dynamics was used to simulate the diffusion in Lennard-Jones fluids in a wide range of reduced densities from 0.298 to 1.19 and reduced temperatures from 0.833 to 1.67. Except for small deviations at very high densities, the simulation results agree with the model predictions when the temperature is not too low.
A space solar power station (SSPS) has become a huge potential candidate to provide abundant and clean electrical energy for terrestrial users by collecting and converting solar power in space. In ...this paper, an innovative two-layer ring truss-based SSPS is proposed. It consists of the top layer concentrator-based spherical one-time reflection region, the bottom layer space radiator using symmetric or asymmetric cable networks, a ring truss for a supporting structure, a photoelectric conversion system, and transmitting antennas. The construction strategies including the triangular facets modularity of top layer concentrator, area requirement of bottom layer space radiator, two-segment optimization design of generatrix of photoelectric conversion system, and aperture derivation of transmitting antenna are carried out. Then, the performance analysis mainly including the modularization theory error calculation, energy collection and distribution, and thermal characteristics in orbit of this proposed SSPS is presented. Finally, the system parameters are estimated and summarized for a better sense of the proposed SSPS. The results indicate that 100% energy collection can be achieved for an ideal concentrator, and 80% with a modular division layer of 6 and tracking error of no more than 2°. The results demonstrate the feasibility of the proposed SSPS concept and can provide a reference for future space energy harvesting and space exploration projects.
Abstract
The theory and algorithm of electric initiation are applied to the study of time-domain response of electromagnetic compatibility of electro-explosive devices(EEDs). based on the antenna ...theory and transmission line theory, the mathematical model of electromagnetic wave time domain response of different signal characteristics of EEDs was established, and the time domain response characteristics of electromagnetic field of typical EEDs were calculated and analyzed. The time domain characteristics of response of EEDs in electromagnetic field were tested and studied based on the characterization method of electromagnetic induction energy of transducer. The experimental results are consistent with the calculated results.
The Space Solar Power Satellite is an ultra-large space structure, which collects sunlight directly in space and then transmits it into the ground. Since the idea was invented in 1968, scientists ...around the world have proposed several typical conceptual design models. Nevertheless, the conceptual models have not been implemented for technological, manufacturing, and cost reasons. This paper presents a novel Space Solar Power Satellite scheme with modular line-focused concentrators and low concentration photovoltaic modules. First, the line-focused mode is analyzed and the optical performance of the circular trough concentrator is evaluated via ray-trace technique. Then, shape optimization for the cell array based on the Bézier curve is carried out to improve the optical property. Numerical examples indicate that the optimized cell array could obtain high power collection efficiency and suitable energy distribution. Moreover, the area of the photovoltaic cell array is reduced, which is conducive to cost reduction. Furthermore, modular design is conducted on the circular trough concentrator. Finally, the primary scheme of the novel Space Solar Power Satellite is designed with the previous modular concentrator and optimized cell array.
To augment the intelligence and safety of a rocket or ammunition engine start, an intelligent initiation system needs to be included in the data link. A laser-controlled intelligent initiation system ...with inherent safety and a laser-controlled explosion-initiating device (LCEID) incorporating electromagnetic pulse (EMP) resistant, safe-and-arms fast-acting modular device based on photovoltaic power converter technology is designed and fabricated in this work. LCEID is an integrated multi-function module consisting of the optical beam expander, GaAs photovoltaic (PV) array, safe-and-arms integrated circuit, and low-energy initiator. These components contribute to EMP resistance, fast-acting, safe-and-arm, and reliable firing, respectively. To achieve intelligent initiation, each LCEID has a unique "identification information" and a "broadcast address" embedded in integrated-circuit read-only memory (ROM), which is controlled by encoded laser addressing. The GaAs PV array was investigated to meet the low-energy initiator firing voltage requirements. Experimental results show that the open-circuit voltage, short-circuit current, and maximum power output of the four-junction GaAs PV array illuminated by a 5.5 W/cm
laser beam were 220 mA, 21.5 V, and 3.70 W, respectively. When the voltage of the 22 μF energy storage capacitor exceeds 20 V, the laser charging time is found to be shorter than 2.5 s. Other aspects of LCEID, such as laser energy coupling efficiency, the firing process, and the energy-boosting mechanism, were explored. Measurements show that the coupling efficiency of the micro lens with a radius of curvature D = 20 μm and size of r = 50 μm reaches a maximum of 93.5%. Furthermore, for more than 18 V charge voltage, the LCEID is found to perform reliably. The fabricated LCEID demonstrated a high level of integration and intrinsic safety, as well as a finely tailored initiation performance that could be useful in military applications.
Space Solar Power Station (SSPS) is a giant spacecraft to collect space solar energy and transmit electric energy to the ground by using the wireless transmission technology. As a concentrated space ...solar power station, SSPS via the Orb-shape Membrane Energy Gathering Array (OMEGA) system is comprised of the concentrator subsystem, the photovoltaic array subsystem and the transmitting antenna subsystem. In this manuscript, the comprehensive study on the coordinate kinematic among subsystems is carried out. Firstly, kinematic analysis and dynamic analysis are conducted. Secondly, under the condition of ideal attitude, the influence of the moving condition of the Photovoltaic (PV) array on the overall system is studied. Finally, the control ability for the deviation attitude caused by the acceleration process of the photovoltaic array is studied. The simulation results demonstrate the serious influence of the angular acceleration of the photovoltaic array on the system's attitude and the validity of the designed attitude control system.
For high-temperature gas-phase reactions in the presence of steam such as the selective catalytic conversion of NOx from mobile sources, the deactivation of catalysts often occur because of their ...poor hydrothermal stability. Herein, we successfully prepared a high-silica Cu/ZSM-5-PAD catalyst based on an effectively induced polymer (polyacrylamide) assisted deposition (PAD) strategy. The obtained catalyst exhibited excellent catalytic performance for NH3-SCR in terms of activity, anti-hydrothermal aging and poison-resistant abilities. This excellent catalytic performance could be correlated with the encapsulation and confinement dispersion of Cu-based active species within the ZSM-5 molecular sieve channels, which dramatically optimized the catalytic properties and structural stability of the solid.
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•An excellent Cu/ZSM-5 catalyst was prepared by polymer assisted deposition method.•The confinement dispersion of CuO species in the zeolite channels was constructed.•Satisfactory hydrothermal stability and H2O/SO2 resistance were also obtained.•The deactivation derived from agglomeration of active species was inhibited.
The condensation process of water with different nuclei under electromagnetic wave irradiation was studied by molecular dynamics simulation. It was found that there is a different electric-field ...effect when the condensation nucleus was a small (NH4)2SO4 cluster than a CaCO3 nucleus. Through the analysis of the hydrogen-bond number, energy change, and dynamic behavior, we found that the effect of external electric field on the condensation process mainly comes from the change of potential energy caused by the dielectric response and there is a competition effect between the dielectric response and the dissolution in the system with (NH4)2SO4.
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•The condensation process of water vapor under time-varying electric field was studied by Molecular Dynamics.•When CaCO3 was applied as the condensation nucleus, the electric field delays the occurrence of phase transition.•There is a competition effect between the dielectric response and the dissolution of ions in system with (NH4)2SO4.
•A flexible multibody dynamics model of the SSPS-OMEGA is established.•Concentrator is divided into many planar elements as equal latitude and longitude.•Relationship between division layers of ...concentrator and solar collection is studied.•Relationship between deformation of concentrator and solar collection is studied.
According to the ideal optical design, the spherical concentrator made by the semi-transparent and semi-reflecting thin film is used in SSPS-OMEGA system. To obtain the continuous power, the PV array should rotate around the spherical concentrator to point the sun when SSPS-OMEGA rotate around the earth on GEO. However, considering the in-orbit assembly, the concentrator is assembled by many planar elements to be approximate to the ideal spherical concentrator. The solar ray collection rate fluctuates in certain scope because the original solar ray path is changed. In addition, planar element is deformed easily by the rotating PV array, which also lead to the fluctuation because the position of the planar element is changed. In this paper, the spherical concentrator is divided into many planar elements by using equal latitude and longitude method. It is studied that the relationship between the number of division layers and the collection rate fluctuation by using Monte Carlo Ray Tracing method. The simulation results indicate that with increasing dividing layers, the collection rate increases and the fluctuation amplitude decreases, which ranges 80.72–83.70% (2.98%) of 24-layers concentrator, ranges 88.45–89.91% (1.47%) of 48-layers concentrator, and ranges 92.46–93.80% (1.33%) of 72-layers concentrator. To solve the deformation of the concentrator, the flexible multibody dynamics model of SSPS-OMEGA is established. Combing the deformation and Monte Carlo Ray Tracing method, it is studied that the relationship between the deformation of the concentrator and the collection rate. The simulation results indicate that the stiffness of 72-layers concentrator is better than 24-layers concentrator and 48-layers concentrator, and the reduction of the collection rate of 72-layers concentrator, which is 0.4%, is less than 24-layers concentrator (1.57%) and 48-layers concentrator (0.81%).
This paper proposes an innovative thermal control strategy for obtaining optimum layout of Orb-shape Membrane Energy Gathering Array (OMEGA) space solar power station radiator based simultaneous ...shape and topology optimization. Firstly, a parameter in term of maximum heat dissipation per mass is introduced for the optimal configuration using the Particle Swarm optimization algorithm. Then, analogizing the butterfly wing vein and branch points, a better layout of heat transfer network is inspired to conduct. Based on this, the virtual temperature points are added for completely constructing bionic butterfly wing heat transfer network and the calculation method is derived and discussed in detail. Finally, the derived method is realized through topology optimization method and the validity is verified through comparison of thermal analysis results. Unlike other radiators design, the proposed method optimizes layout of radiator from both two aspects of configuration outside and bionic butterfly wing heat transfer network inside, which is meaningful for the future application.
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