Properties of a Small Titanium-ion Pump

Aim: The main aim of the study was to investigate the possibility to use the Pathfinder simulation software to determine the duration of an evacuation and to plan its course for various scenarios of evacuation organisation, for specific profiles and behaviours of passengers and on-board personnel, and for a specific geometrical arrangement of the passenger cabin of a selected passenger aircraft. In addition, the paper discusses selected factors that affect the evacuation from the passenger aircraft. Project and methods: The Pathfinder software used in the research has the graphical interface to create an evacuation simulation model (2D and 3D) as well as tools to visualise the results. Pathfinder is based on artificial intelligence algorithms, in which each passenger has a number of individual features that can influence his/her movements and decisions during the simulation. The simulation of people's movement is determined by their profiles and behaviours, the parameters of which can be entered by means of probability distributions, which makes it possible to take into account the stochastic nature of the evacuation process. Results: The Boeing 787 Dreamliner was selected for the study, for which six options for simulating the evacuation of 252 passengers and eight members of on-board personnel were conducted. The shortest evacuation time was achieved by changing the even distribution of the number of passengers to the individual emergency exits, thus avoiding congestions in sensitive areas of the passenger cabin. The increase in passengers' maximum speed has paradoxically increased evacuation times, as it has increased the intensity of passenger collisions. It was found that one of the key issues affecting the timing of an evacuation is the proper organisation of the evacuation by on-board personnel, who, by guiding passengers through the geometrically most advantageous passageways, results in the fastest possible evacuation. The simulations in variants five and six have achieved satisfactory evacuation times, which are within the emergency aircraft evacuation time limit required in a certification process. Conclusions: The presented simulation models, the results obtained, and the wide range of possibilities of three-dimensional visualisation of research results give a rational basis for the use of Pathfinder software for testing the evacuation process and thus: for the usage in the aircraft design process, for preparing aircrafts for tests, for shaping evacuation procedures, for on-board personnel training and for air accident investigation.

This paper presents the experiment results of the magnetic suspension in a bearingless brushless DC motor to apply in small liquid pumps. The bearingless motor structure, the principle of the suspension force generation and the magnetic suspension control strategy in the bearingless brushless DC motor have been proposed by the author. A prototype bearingless brushless DC motor has been designed based on the computed results by Finite Element Method (FEM) to apply a small liquid pump. It is confirmed by the experiments using the prototype machine that the rotor is successfully suspended without mechanical contact when it drives a liquid pump at the maximum rotational speed of 2,200 r/min and the maximum fluid flow of 8.2 l/min. This result shows that the proposed bearingless brushless DC motor is enough suitable as the drive for the small liquid pumps.

Reduction of etch pits in heteroepitaxial growth of 3CSiC on silicon

The pressure inside an enclosed void in a solid dielectric is generally determined by calculation based on equating the measured partial discharge (PD) onset voltage and the breakdown voltage from the Paschen curve for a particular gas. Here it is assumed that the gas is known or that physical properties remain approximately constant. In the present experiment, two different large voids were placed in epoxy adjacent to the ground electrode containing a small pump out port. This arrangement allowed for direct measurement and setting of the pressure for different gases filling the void. PD onset and extinction voltages were determined as a function of pressure over the range from 13.3 Pa (0.1 torr) to 101 kPa (760 torr) for nitrogen and SF/sub 6/ at room temperature. The onset voltages generally followed the Paschen curve dependence on pressure but were higher in voltage at pressures around the minimum, while the extinction voltage followed the Paschen curve more closely in both pressure dependence and voltage. Agreement with the Paschen curve is better at the higher pressures. One possible explanation is the dominant role that real surfaces play at lower pressures.

Spacecraft operate in complex space environments filled with a variety of natural or anthropogenic particles and fields, which may trigger outgassing breakdown on their surfaces and thus lead to spacecraft failures in orbit. The physical process of outgassing breakdown in the atmosphere is more complex than in vacuum, which requires the consideration of electron–neutral collisions and electron attachment effects in addition to field emission and secondary electron multiplication. In this article, based on particle-in-cell (PIC), a 2-D simulation model of electromagnetically irradiated metal-aluminum film under atmospheric conditions is established to simulate the outgassing breakdown process in oxygen and air, and to analyze the influence laws of gas density, gas composition, microwave field strength, and electron attachment effect on the breakdown. The results show that gas breakdown is related to the background gas composition, and breakdown is more likely to occur in an oxygen environment than in air; the same kind of gas shows different breakdown formation time patterns at low and high pressures. At low pressure, the breakdown time is rapidly shortened with the increase in air pressure, and at high pressure, the breakdown time increases with the increase in air pressure; the electron attachment has an inhibitory effect on the gas breakdown at high air pressure.

Computational Fluid Dynamics (CFD) for air/water-vapor and water-liquid two-phase flow mixing with condensation in a vertical inverted U-tube is presented in this paper. This study is to investigate the flow behaviors and underlying some physical mechanisms encountered in air/water-vapor and water-liquid mixing flow when condensation is considered. Water-liquid flows upward-downward through the inverted U-tube while the air/water-vapor mixture is extracted from a side-tube just after the flow oriented downward. The CFD simulation is carried out for a side air/water-vapor mixture volume fraction (αm) of 0.2–0.7, water-vapor mass fraction (Xv) of 0.1–0.5 in the side air/water-vapor mixture and water-liquid mass flowrate (mw) of 2,4,6, and 8 kg/s. The present results reveal that, at lower air mass flow rate, no significant effect of Xv on the generated static pressure at the inverted U-tube higher part. However, by increasing the air mass flow rates, ma ≥ 0.001 at mw = 2 kg/s, and ma ≥ 0.00125 at mw = 4 kg/s, we can infer that the lowest static pressure can be attained at Xv = 0.1. This may be attributed to the increased vapor and air mass flow rates from the side tube which results in shifting the condensation from the tube highest part due to air accumulation. This leads to increasing the flow pressure and decelerating the water-liquid flow. Raising mw from 2 to 4 kg/s at the same vapor mass ratio results in a lower static pressure due to more condensation of water vapor. The turbulent intensity and kinetic energy starts to drop approximately at ma = 0.002 kg/s, and αm = 0.55–0.76 at mw = 2 kg/s for all Xv values but no noticeable change at mw = 4 kg/s occurs. These findings estimate the operational values of air and water mass flow rates for stable air entrainment from the side-tube. Increasing the air and vapor mass ratio over these values may block the evacuation process and fails the system continuance. Likewise more air entrainment from the side-tube will decelerate the water flow through the inverted U-tube and hence the flow velocity will decrease thereafter. Moreover, this study reveals that the inverted U-tube is able to generate a vacuum pressure down to 55.104 kPa for the present model when vapor condensation is considered. This generated low-pressure helps to vent an engineering system from the non-condensable gases and water vapor that fail its function if these are accumulated with time. Moreover, the water-liquid mass flow rate in the inverted U-tube can be used to sustain the required operating pressure for this system and extract the non-condensable gases with a less energy consuming system. The present CFD model provides a good physical understanding of the flow behavior for air/water-vapor and water-liquid flow for possible future application in the steam power plant.

The variation in produced gas composition from mixed gas coal seam reservoirs

Nitrogen and water vapor pumping study on a 400 mm opening LN2 cooled sorption cryopump

Evidence for low-pressure incongruent melting of limestone containing up to 40 wt% of silicate minerals (marly limestone) is reported from the Khamaryn–Khural–Khiid Combustion Metamorphic (CM) complex in East Mongolia. Marly limestone exposed to high-temperature metamorphism during wild coal fires has acquired a mineral assemblage consisting of gehlenitic melilite and Al-diopside-to-kushiroite-dominant clinopyroxene as main phases and rare phases of celsian, spinel, perovskite, geikielite, etc. Melting of silicate minerals and calcite produced silicate melts of different compositions and stoichiometric calcitic (CaCO3) or non-stoichiometric carbonatite-like (CaCO3 + CaO) melts. Coalescence of silicate melt drops was followed by the formation of silica-undersaturated Ca-rich and Na-bearing paralava melts. Melilite-nepheline paralavas discovered in the Khamaryn–Khural–Khiid and Nyalga CM complexes in Mongolia have exceptional features of mineralogy and chemistry due to a rare combination of P–T conditions associated with wild coal fires and combustion metamorphism: a high temperature (> 1250 °C) and fluid pressure above 4 MPa that prevented decomposition of calcite. Such paralavas from the two CM complexes are composed of similar mineral assemblages made up of melilite, clinopyroxene, plagioclase, nepheline, Fe–Ca olivines (Ca-fayalite and kirschsteinite), K-Ba feldspars (celsian and hyalophane), spinel-group minerals, and rhonite-kuratite, with broad composition variations. Paralavas of this kind have never been reported before from anywhere. Their local mineralogical and geochemical specificity may be due to variations in the composition of carbonate protolith and in physicochemical conditions above the coal fire foci (T, P, gas composition, oxygen fugacity, and melt cooling rate). Low-pressure melting of calcite and the formation of carbonate (calcitic or carbonatite-like) melts have implications for phase relations in carbonate rocks altered by high-temperature metamorphism and metasomatism, as well to the origin of carbonatites. Calcite in carbonate sediments exposed to low pressures and high temperatures (above the invariant point Q1 in the CaCO3 phase diagram) does not decompose and can melt. Correspondingly, metamorphic decarbonation reactions do not produce CaO required for the crystallization of many Ca-rich index minerals of spurrite–merwinite facies. The melting point of calcite decreases markedly with increasing H2O content in the H2O–CO2 fluid, which may lead to melting of calcite in carbonate sediments and to formation of calcite-rich carbonatites at P–T crustal conditions.

A TEPC, from its operation principle, fulfils reasonably well the requirements of an area monitor with dose equivalent response nearly independent of neutron energy to be used for radiation protection dosimetry at various work places. However, between neutron energies from 10 keV to 1 MeV, which are of relevance for environments with strongly moderated neutron fields, the response of TEPCs with thin walls is too low. Attempts to increase the response in this energy region by modifying gas pressure, gas composition and wall thickness show that significant improvement first requires operation of the TEPC at lower simulated diameters compared with the 2 µm diameter commonly used. Preliminary investigations to improve the operational properties of TEPCs at low pressures are presented.

The NH(2)-MIL-53(Al) metal-organic framework was studied for its use in the separation of CO(2) from CH(4), H(2), N(2)C(2)H(6) and C(3)H(8) mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO(2) were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in situ XRD patterns measured during adsorption. Apart from CO(2), all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO(2) interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO(2) from other gases. The separation of CO(2) from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH(2)-MIL-53(Al). The effect of total pressure (1-30 bar), gas composition, temperature (303-403 K) and contact time has been examined. In all cases, CO(2) was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH(2)-MIL-53(Al) pellets retained their selectivity and capacity for more than two years.

Because of its property of low permeability, low pressure and low production, Changqing low permeable oilfield decreases rapidly in the initial potential stage and has low individual-well producing rate, which give rise to the overestimated oilfield production and large-scale ground construction project of gathering system. Eventually, the problem of “big Marathi car” in oil gathering system generated excessive energy consumption. It is multi-purpose station, pumping station and block station that turn out to be the main energy consumption point, which consume over 90% of system electric energy consumption. Besides, energy like natural gas is dissipated so severely that the utilization ratio of associated gas is less than 30%. This is obtained by analyzing energy distribution of system. For the seriously power-wasting problems in gathering system, energy saving technologies of small power pump replacing large power pump, intermittent pipelining oil by liquid level automatically controlled and double speed adjustment based on frequency control apply to the effective utilization of electric energy, which using oil pumps load rate as energy evaluation criterion. Applying technologies of helical down hole oil-gas separation and oil-gas airtight gathering to recover associated gas effectively gives conspicuous energy saving effect.

The operation performance of the axial piston pump is affected by external environment pressure, and its conditions at low suction pressure are less studied. The oil model and fluid dynamic model of the axial piston pump are developed and a novel approach for predicting the operation performance of such machines at low suction pressure based on this model is presented. It was found that the inlet pressure of the suction chamber changes linearly with the environment pressure. Compared to the present data from the product manual, this approach is proved to be valid and is used to predict the maximum operating speed and suction pressure at other environment pressure, therefore the low-pressure operating performance map is enriched for the referring of more users of the pump. In future, this study provides a new method for the prediction and the design guide of pump operation at low suction pressures.

We have investigated the pumping speed as well as the liquid helium and liquid nitrogen consumption of a large-capacity, all aluminum cryocondensation pump having a projected area of 0.9 m2 and real area of 1.15 m2. The liquid-helium-cooled surface was shielded from room-temperature thermal radiation by a black anodized aluminum chevron baffle held at 77 K. Deuterium pumping speed was nearly constant ∠80 000 l/s for gas flow rates up to 11 Torr l/s (1.47 Pa m3/s) and surface coverages up to 9×1020 molecules/cm2. The speed, however, increased slightly with coverage. Hydrogen pumping speed was also constant, i.e., 110 000 l/s. The boil off of liquid helium depended on the residual pressure and gas composition in the system. At low pressures boil off of liquid helium for D2 and H2 films was 0.53 and 0.85 W, respectively. Boil off of liquid helium increased linearly with the pumped gas load. The liquid nitrogen consumption was only weakly dependent on the pressure in the system.

The objective of this study was to compare the energy efficiencies of flow rate valves used in different lines and variable speed drive (VSD) in a small centrifugal pump irrigation system. The tests were done by using an outlet valve, inlet valve, by-pass valve, and VSD. The study included four replications of constant speed and variable speed experiments, and three replications of constant pressure experiments. In each test, power consumption, inlet pressure, and outlet pressure were measured at different flow rates. During the constant speed tests at about the operating point, by-pass valve saved energy up to 66% and 5% compared to the outlet valve and inlet valve, respectively. Reducing the flow rate by 20% resulted in 7% less energy consumption with the use of both the by-pass valve and the inlet valve, and 19% more energy consumption with the outlet valve. The use of VSD showed profound advantage over the valves used in constant speed tests, with 41%, 44%, and 80% less energy demand compared to the by-pass, inlet, and outlet valve, respectively. Also, VSD and by-pass valves were compared in constant pressure operations. VSD offered 2 to 37% less energy consumption at pressures from 4.0 bar to 2.5 bar. The savings were less at high flow rates and quickly increased as the flow rate need decreased. The low system efficiency found in constant speed tests suggested that the pump was not appropriate for the hydraulic system used in low pressure applications. According to constant pressure tests, the system efficiency for VSD (26-29.1%) was greater than that of the by-pass valve (21.3-25.5%). In conclusion, the VSD was the most energy efficient method and suggested significant energy savings in small powered pump systems.