Theoretical Prediction of CHn Crystal Structures under High Pressures

CHn is the precursor unit for graphene synthesis. We have theoretically predicated a series of CHn structures with n = 1, 2, 4, 6, 8, 10, and 12 at elevated pressures (ambient pressure, 50, 100, 200, 300, 350, and 400 GPa) using evolutionary algorithms. The predicted CH and CH2 structures are graphane-type and polyethylene over the whole considered pressure range, respectively. The molecular crystalline methane is predicted for the stoichiometry of CH4. The combination of methane and H2 for CH6, CH8, CH10, and CH12 up to 300 GPa are obtained. At 400 GPa, the mixture of polymer and H2 for CH6, CH10, and CH12 comes into play. From the computed enthalpy, higher pressure and more hydrogen concentration contributed to the decomposition (to carbon and H2) of CHn systems. The total density of states for these CHn structures show that only the CH12 phase is metallic above 300 GPa. The rotational properties are traced in H2 and the CHn structures. The CH4 rotation is more sensitive to the pressure. The H2 units are nearly freely rotational. Other structures of CHn, including fcc-type and experimentally known structures, are not competitive with the structures predicted by evolutionary algorithms under high pressure region. Our results suggest that the CHn (n > 4) system is a potential candidate for hydrogen storage where H2 could be released by controlling the pressure.

ABOUT CONICAL CUMULATION IN STORAGE AMPOULES

Conical cumulation in storage ampoules consists of a periodically repeating wave pattern - the formation of an axial high-pressure region as a result of the focusing of oblique waves and its unloading. In this case, the convergence of the oblique wave is accompanied by a loss of stability - protrusions appear at the wave front, the collision of which leads to an increase in pressure. The expansion of the high-pressure region is accompanied by the formation of an axial crack and continues until its pressure becomes lower than the pressure of the incoming oblique waves, after which the flow pattern is repeated.

Biomass Burning and Gas Flares create the extreme West African Aerosol Plume which perturbs the Hadley Circulation and thereby changes Europe’s winter climate

Europe’s winter climate has experienced three significant changes recently: increased UK flooding; Iberian drought; and warmer temperatures north of the Alps. The literature links all three to a persistent, significant increase in sea level pressure over the Mediterranean and Iberia which changes the atmospheric circulation system by: forcing cold fronts north away from Iberia; and creating a south westerly flow around the high-pressure region bringing warmer, moist air from the subtropical Atlantic to Europe which increases UK precipitation and European temperatures. Here I show, using modelled, reanalysis and measured data, that: the extreme, anthropogenic, West African aerosol Plume (WAP) which exists from late December to early April perturbs the northern, regional Hadley Circulation creating the high-pressure region; and that the WAP has only existed in its extreme form in recent decades as the major sources of the aerosols: biomass burning; and gas flaring have both increased significantly since 1950 due to: a four-fold increase in population (United Nations); and gas flaring rising from zero to 7.4 billion m3/annum (Global Gas Flaring Reduction Partnership). I also suggest that the WAP can be eliminated and Europe’s winter climate returned to its natural state after the crucial first step of recognising the cause of the changes is taken.

Sensitivity Analysis of Tunable Equation of State Material Model In Pulsed Mercury Target Simulation

A pulsed neutron spallation target is subjected to very short but intense loads from repeated proton pulses. Approximately 60% of the energy from each proton pulse is deposited into the mercury target material and the stainless-steel target structure, leading to a high-pressure region in both the stationary target structure and the flowing mercury. The high-pressure region propagates and leads to fluid-structure interaction. The resultant loading on the target structure containing liquid mercury is difficult to predict, although various simulation approaches and material models for the mercury have been tried. To date, the best match of simulation to experimental data is obtained by using an equation of state (EOS) material model with a specified tensile cutoff pressure, which simulates the cavitation threshold. The inclusion of a threshold to represent cavitation is key to the successful predictions of stress waves triggered by the high-energy pulse striking the mercury and vessel. However, recent measurements of target structure strain show that significant discrepancies remain between the measured and simulated strain values in the EOS mercury model. These differences grow when noncondensable helium gas is intentionally injected into the flowing mercury to reduce the loading on the structure. An EOS-based proportional–integral–derivative (PID) mercury model has been proposed to reduce the gap between the measured and simulated vessel strain responses for targets with gas injection. The conceptual and numerical description and initial investigation of the PID model are presented in previous work. Further studies of this PID model — including the sensitivity of the structure’s strain response to model parameters (the tensile cutoff, PID parameters Kp, Ki, and Kd) — are reported in this article. Results show the strain response is more sensitive to changes in the tensile cutoff value than to changes in the model parameters Kp, Ki, and Kd. These results will aid in future work where the model parameters will be optimized to match simulation data to strain measurements.

Effect of a Circular Slot on Hybrid Airship Aerodynamic Characteristics

This numerical study reports the aerodynamic properties of a hybrid airship. The hybrid airships were designed by combining two semi-ellipsoids with a semi-discoid as the base model. From the base model, three different geometrics were identified to study their aerodynamic characteristics. A circular slot was provided between the pressure side and the suction side of the airship. The objective of this study was to realize the flow behavior, aerodynamic characteristics, and stability properties of such slotted hybrid flying vehicles. Interestingly, the results imply that the lift coefficient increases with an increase in the angle of attack for the slotted configurations; this is because the flow separation is delayed due to the slot opening, which in turn is due to the flow of energies from the high-pressure region to the bottom through the slots. The delayed stall angle was 50 degrees, which was 10% more than that of the base model. Aerodynamic characteristics are discussed based on surface pressure, coefficient of lift, and coefficient of drag for various slotted hybrid airships.

Mitigating the Piston Effect in High-Speed Hyperloop Transportation: A Study on the Use of Aerofoils

The Hyperloop is a concept for the high-speed ground transportation of passengers traveling in pods at transonic speeds in a partially evacuated tube. It consists of a low-pressure tube with capsules traveling at both low and high speeds throughout the length of the tube. When a high-speed system travels through a low-pressure tube with a constrained diameter such as in the case of the Hyperloop, it becomes an aerodynamically challenging problem. Airflow tends to get choked at the constrained areas around the pod, creating a high-pressure region at the front of the pod, a phenomenon referred to as the “piston effect.” Papers exploring potential solutions for the piston effect are scarce. In this study, using the Reynolds-Average Navier–Stokes (RANS) technique for three-dimensional computational analysis, the aerodynamic performance of a Hyperloop pod inside a vacuum tube is studied. Further, aerofoil-shaped fins are added to the aeroshell as a potential way to mitigate the piston effect. The results show that the addition of fins helps in reducing the drag and eddy currents while providing a positive lift to the pod. Further, these fins are found to be effective in reducing the pressure build-up at the front of the pod.

HYDROGEN — ZERO CARBON FOOTPRINT

This article presents Russia’s main achievements of over the past 65 years in the development of an advanced scientific and technical groundwork for the introduction of hydrogen as a fuel in various energy systems. On the basis of the obtained world-class results, the authors argue for the necessity of creating a Center for Hydrogen Innovative Development (CVIR) with the decisive participation of enterprises with real experience in obtaining liquid hydrogen (H2l) with the possibility of its long-term storage. A concept has been formulated for the development of breakthrough technological solutions for the widespread use of hydrogen as an efficient and environmentally friendly (without the formation of carbon oxides) fuel in various power systems within the framework of the CVIR. In particular, the strategic direction of the CVIR project was developed in order to create a developed infrastructure for the reliable provision of vehicles with the required amount of fuel in a limited period of time. This can be achieved by applying the method of cryogenic filling of transport cylinders, taking into account the real properties of hydrogen in the ultra-high pressure region (70 MPa and above). The results have revealed possibilities for further building up the advanced scientific and technical groundwork for the broad promotion of hydrogen in the energy complex of Russia, which is presented in the CVIR project. In addition, the authors have compared the developed technologies with foreign analogues.

Numerical simulation of an industrial centrifugal fan 5,5 kW with OpenFOAM

Centrifugal fan is a mechanical device working on the principle of centrifugal pump. When working, propeller sucks air along the axis, the pressure at the fan center will be small. The air will move from high pressure region to where the pressure is low. In other words, the air will receive additional centrifugal forces. The appearance of centrifugal fan has brought us many benefits such as basement ventilation systems or where ventilation fans enable to be directly established. Hence, the study of the performance characteristics of centrifugal fan is currently a matter concern, from which the improvement of performance can be applied to the fan. In this paper, a model simulating the performance characteristics of centrifugal fan was done on snappyHexMesh ultility with mainly hexahedron girds. Therefore, the results of the performance characteristics of centrifugal fan use k – omega SST is compared with experimental data. The results obtained from automatic meshing snappyHexmesh ultility and the SimpleFoam solver of open source OpenFOAM software provide the reliable data in the design and calculation of centrifugal fan. On this basis, the cost of improving the performance of centrifugal fan can be reduced considerably by numerical simulation.