Compression Of Helium Research Articles

Quasi-Isentropic Compression of Gaseous Helium and Deuterium in Spherical Structures at Terapascal Pressures

The results of four experiments on studying preliminarily statically compressed gaseous helium and deuterium during their subsequent compression in explosive spherical cascade structures providing quasi-isentropic gas compression are presented. For helium, the following parameters were achieved: in one experiment, the compression pressure is Pmean ≈ 4.9 TPa at a density ρmax ≈ 6.4 g/cm3 and the compression ratio is δ = ρ/ρ0 ≈ 320; in another experiment, Pmean ≈ 10.9 TPa, ρmax ≈ 10.3 g/cm3, and δ ≈ 470. For deuterium, these parameters are Pmean ≈ 3.4 TPa, ρmax ≈ 6.0 g/cm3, and δ ≈ 162 in one experiment and Pmean ≈ 13.3 TPa, ρmax ≈ 11.4 g/cm3, and δ ≈ 520 in another experiment. The gas density was determined by an X-ray method using the position of the boundaries of the steel shells compressing a gas. The experiments are simulated with a one-dimensional gasdynamic software package, in which the Kopyshev–Khrustalev equations of state are used for the gases under study. The pressures are determined using calculations, in which the dynamics of gas compression is satisfactorily simulated for the entire set of experiments.

Quasi-Isentropic Compression of Gaseous Helium and Deuterium in Spherical Structures at Terapascal Pressures

Quasi-Isentropic Compression of Gaseous Helium and Deuterium in Spherical Structures at Terapascal Pressures

Modeling the Properties of Helium at High Pressures

The paper presents simulation of shock-wave compression of liquid helium. Considering the possible ionization at high compression rates is shown to increase the accuracy of prediction of the helium properties.

Results of Experiments on Quasi-Isentropic Compression of Deuterium and Helium to Extreme Pressures of 3000 GPa

Results of Experiments on Quasi-Isentropic Compression of Deuterium and Helium to Extreme Pressures of 3000 GPa

Experimental Evaluation of the Efficiency of Long-Stroke, Low-Speed Reciprocating Compressor Stages in Compression of Different Gases

Results of comparative experimental tests of a stage of a long-stroke, low-speed reciprocating compressor with compression of air, helium and carbon dioxide in a single-stage from atmospheric pressure to 5.0−10.0 MPa are presented. An analysis of the working processes of the stage is performed in the course of operations in these regimes. The results confirm the assumptions that it is possible to compress gas in a single stage from atmospheric pressure to high pressures with an acceptable level of discharge temperature and with acceptable integral characteristics.

Experiments on Quasi-Isentropic Compression of Deuterium and Helium to Extreme Pressures of ≈3000 GPa

Experiments were performed to study the spherical compression of deuterium and helium to pressures of ≈3000 GPa in a quasi-isentropic regime. The process was recorded by a multiframe radiographic system which produces up to nine x-ray images of a cavity with gas at different times in one experiment. X-ray images show that explosive devices provide a nearly spherically symmetric shape of the cavity with gas up to the maximum compression of the gas. The experimental data are in good agreement with the results of calculations using the equations of state of the gases studied. From the results of these calculations, the parameters of the region of the compressed gas states obtained in the experiments were determined: for deuterium, a density of 5.5 g/cm3 and a pressure of 3.6 TPa; for helium, a density of 4.7 g/cm3 and a pressure of 2.4 TPa.

Results of Experiments on Quasi-Isentropic Compression of Deuterium and Helium to Extreme Pressures of ~3000 GPa

Results of Experiments on Quasi-Isentropic Compression of Deuterium and Helium to Extreme Pressures of ~3000 GPa

Theoretical and experimental studies on oil injected twin-screw air compressor when compressing different light and heavy gases

Oil injected twin-screw compressors are widely used for medium pressure applications in many industries. Low cost air compressors can be adopted for compression of helium and other gases, leading to significant cost saving. The efficiency, delivery rate and the heat of compression of the compressors (medium and small size) has been analyzed and presented in the study. To generate machine independent experimental data, two similar compressors with different capacities have been setup to test the performance of air compressors when applied to compress nitrogen, argon and helium gases apart from air. Also this paper addresses the gas delivery rate and heat of compression (temperature) on volumetric and power efficiency.

Mathematical modeling of the working cycle of oil injected rotary twin screw compressor

Oil injected twin-screw air and gas compressors are widely used for medium pressure applications in many industries. Low cost air compressors can be adopted for compression of helium and special gases, leading to significant cost saving. Mathematical analysis of oil injected twin-screw compressor is carried out on the basis of the laws of perfect gas and standard thermodynamic relations. Heat transfer coefficient required for computer simulation is experimentally obtained and used in performance prediction, when the working medium being air or helium. A mathematical model has been developed for calculating the compressor performance and for validating the results with experimental data. The flow coefficients required for numerical simulation to calculate leakage flow rates are obtained from efficiency verses clearance curves. Effect of some of the compressor operating and design parameters on power and volumetric efficiencies have been analyzed and presented.

Towards a better understanding of the physics of the two-volume model of accelerator magnet quench thermohydraulics

The LHC currently under construction at CERN will make intensive use of high-field, twin aperture superconducting magnets operating in static baths of pressurized helium II at 1.9 K and at about 100 kPa. As long as magnet construction guarantees pressure homogeneity after a resistive transition by allowing sufficient radial venting, the quench thermohydraulics can be depicted by a mathematical model based on the assumed helium split between two hypothetical volumes of confined and bulk helium. The first phase of the process is dominated by fast adiabatic compression of bulk helium driven by the expanding confined helium while in the second phase the whole amount of the helium undergoes isochoric heating. We make the first conjecture that the confined helium is not solely composed from the helium filling the cable porosities, but also from a thin helium layer surrounding the coil. The second conjecture is that the onset of the isochoric heating phase is a result of fast heat transfer via the magnet collars to the bulk helium, still resting in a superfluid state, quantitatively overtaking in importance the adiabatic compression route as a means of energy transfer. Our hypothesis of the transition mechanism from adiabatic compression of the bulk helium to isochoric heating has been confirmed numerically and has been experimentally justified with String 2 measurements.

ОПТИМИЗАЦИЯ КРИОГЕННОЙ ГЕЛИЕВОЙ УСТАНОВКИ С ЭНЕРГОКРИОГЕННОЙ СТУПЕНЬЮ

The actual task is the creation of cryogenic helium units in which compression of helium has made in centrifugal compressors. Through of small degrees of compression of helium in one step it fails now to develop suitable for this purpose helium turbo compression. In the given article continuing cycle of the early publications of the writer, the helium refrigerator with energy-cryogenic step is considered. The most simple diagram of energy-cryogenic step realizing gaseous expander cycle is applied to simplification of optimization calculations and following analysis. The step makes operation for a drive of cold helium turbocompression and at the same time — a cold for heat elimination of compression. The working bodies of energy-cryogenic step are nitrogen, neon and argon. Helium is compressed in cold four-step centrifugal compressor, since temperature 85,8 K. The optimization of the refrigerator on a level 4,5 K was carried out at the same value of cold-productivity 576 W. The fulfilled optimization has shown that the creation of the rather effective helium refrigerator on a basis only of machines of dynamic operation is possible.

Noble gas exhaust with a strongly baffled divertor in ASDEX-Upgrade

Since spring of 1997 ASDEX Upgrade has operated with the new divertor II (LYRA), which is characterised by vertical target plates, tight baffling towards the main chamber, and a dome baffle in the private flux region. The main goal of this divertor modification was to increase the divertor density (of the plasma and of the neutrals) for a given plasma density, whereas the neutral density in the main chamber should be similar or even lower. Pumping occurs now from the private flux region which is linked to the pump chamber by finite conductance below the outer target. A cryo pump (about 100 m 3/s) has been installed in the outer divertor chamber in addition to the turbo pumps. This divertor scheme is very similar to the one planned for ITER. First experiments with the new divertor indicate that the compression of helium, C He (the ratio of neutral He density in the divertor to the He density at the plasma edge) is much higher in the new divertor, while the neon exhaust efficiency has decreased. The cryo pump can strongly enhance the scrape-off layer flow of deuterium (by a factor of about 3), resulting in a small improvement of the He exhaust rate.

Particle exhaust studies in ASDEX Upgrade

An experimental overview on pumping and particle exhaust studies for deuterium as well as for helium and neon in the ASDEX Upgrade divertor tokamak is presented. Strong turbomolecular pumps connected to the divertor region allow effective pumping of all these gases. Deuterium, however, is pumped effectively by the carbon walls in ASDEX Upgrade which dominate over the external pumping. Noble gases are hardly pumped by the walls, and their pumping efficiency and exhaust rate depends strongly on their respective density in the divertor chamber, i.e. on the effectivity of scrape-off layer transport and divertor retention. Compression of helium and neon in the divertor chamber increases with the divertor neutral gas density, and in high-power, high-density discharges in H- or CDH-mode pumping is very efficient. Helium exhaust in these scenarios is sufficiently fast to fulfill the requirements for ITER or a fusion reactor.

Building screw compressors for the compression of helium

Building screw compressors for the compression of helium