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The cooling characteristic experimental rig of rotor system is designed and manufactured, which mainly includes SCO2 turbine shafting, electric spindle, PLC control system, electromagnetic heating device and cooling device. A high precision infrared thermal imager was used to evaluate the impact cooling characteristics of a small gap annular gas jet. The small gap annular gas jet impingement cooling characteristic experiment was completed using a high-precision infrared thermal imaging instrument. The experiment studied the influence of cooling medium temperature and pressure on the axial temperature distribution of the shaft. The results show that the small gap cooling device with incoming airflow interacts with the shaft journal, a significant temperature gradient is formed between the shaft journal and the heat source, thereby effectively controlling the shaft journal temperature. Under the condition that the heat source temperature at the end of the cantilever is approximately constant, the average temperature attenuation rate of the journal decreases gradually with the increase of the pressure difference between the inlet and outlet of the cooling device. Therefore, the mass flow rate of the cooling medium can be controlled by reducing the constrained gap of the jet impact of the gas array, and the mass flow utilization rate of the cooling medium can be improved.

To promote the development and application of the liquid–gas jet pump (LGJP), the research status of its design theory, internal flow mechanism, structural optimization and practical application are reviewed. The development history of the LGJP is briefly reviewed, the latest research and application progress of the LGJP is introduced, and the pulse-type of LGJP, especially the centrifugal jet vacuum pump (CJVP), is emphatically discussed. The research and development direction of the LGJP is analyzed and proposed: CFD will be more deeply applied to the mechanism research and performance improvement of the LGJP; the diversity and heterogeneity of the fluid medium and its influence on the internal flow mechanism are the research highlights of the LGJP; it is urgent to study the gas–liquid two-phase flow and pumping mechanism inside the pulsed liquid–gas jet pump (PLGJP), especially the CJVP.

The mass flow of abrasive is one of the significant factors, which affects the erosion rate of abrasive gas jet eroding rock and coal, because it affects rebounding abrasives and the shielding effect. However, the effect of abrasive mass flow on abrasive acceleration has been little studied in favor of research on abrasive particle erosion, which is of prime importance for the determination of how the mass flow affects the erosion rate. Therefore, in this study, the effect of mass flow on erosion rates was investigated by numerical simulation and experiment, to analyze the effect of mass flow on abrasive acceleration. It can be concluded that the influence of pressure cannot be ignored, as it determines the time and distance of abrasive acceleration. Each pressure has a corresponding optimal mass flow that can achieve the maximum erosion rate. The erosion rate begins to decrease when the mass flow exceeds the optimal value. The wave-like flow-field structure of free jets influences the distribution character of the abrasive, and leads to the formation of the annular structure of the abrasive flow field. The mass flow barely affects the distribution of abrasive, but clearly affects the abrasive velocity. As the mass flow increases, the distance and time of acceleration of the abrasive decrease, which causes the amount of high-speed abrasive on both sides of the jet axis to decrease and the velocity also decreases.

Understanding the physics of electromagnetic pulse (EMP) emission and nozzle damage is critical for the long-term operation of laser experiments with gas targets, particularly at facilities looking to produce stable sources of radiation at high repetition rates. We present a theoretical model of plasma formation and electrostatic charging when high-power lasers are focused inside gases. The model can be used to estimate the amplitude of gigahertz EMPs produced by the laser and the extent of damage to the gas jet nozzle. Looking at a range of laser and target properties relevant to existing high-power laser systems, we find that EMP fields of tens to hundreds of kV/m can be generated several metres from the gas jet. Model predictions are compared with measurements of EMPs, plasma formation and nozzle damage from two experiments on the VEGA-3 laser and one experiment on the Vulcan Petawatt laser.

The authors have considered the gas-dynamic influence upon the mechanical properties, chemical composition, microhardness, and geometry of single-rim welds made of 30ХГСА steel when welding with a consumable electrode under a double-jet gas shield. Their regressional relationships on the selected controlled welding parameters have been developed. It has been found that the gas-dynamic effect of a dynamic shield gas jet has a controlling influence on the formation of welds made of alloy-treated 30ХГСА steel.

This work presents a systematic literature review of powder-gas jet stream (PGJS) characterisation techniques for coaxial nozzles in the laser directed energy deposition process (L-DEDp). The analysis includes thirty-four camera-based and four weight-based techniques. In weight-based techniques, the mapping of powder concentration is made by measuring the powder flow rate in certain areas within the PGJS. Despite being cost-effective, these methods are time-consuming, invasive, and less suitable for real-time monitoring. Camera-based techniques use laser light and a camera to capture particle intensities, allowing for the non-intrusive measurement of powder distribution. Despite its advantage, limitations are reported in the literature regarding the techniques. Detecting dense or fine powder flows accurately is challenging. Two-dimensional images cannot fully represent the jet’s three-dimensional structure, relying on image processing algorithms for the results. However, the non-existence of a common standard metric for evaluating and comparing results across various setups is a significant gap, as each characterisation often needs to be performed on a case-by-case basis. To address these challenges, a basic reporting structure is suggested to enable a standardised assessment of PGJS measurements, thereby supporting process control and quality assurance in L-DEDp applications.

The surface accuracy and quality of the mirror blank determine the performance of the optical mirror, so it is essential to explore a simple and effective way to process the mirror blank. Gas jet forming is a simple and efficient way of forming optical surfaces. However, the key to accurately forming mirror blanks is establishing the relationship between the gas jet parameters and the resulting surface shape. Therefore, several experiments were carried out in this study to develop the relevant models to investigate the above issues. The experimental data analysis found that the surface tension of the viscous fluid being processed impacts the shape of the surface formed by the gas jet. Therefore, the new model for predicting the surface shape of gas jets was developed by refining the Blanks and Chandrasekhara model by adding surface tension. The prediction error of the new model for the depth of the surface formed by the gas jet is in the range of 0.0497–0.833 mm, much smaller than the uncorrected model.

This study is a further development of our “Proposal of a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy” paper published in the journal Atoms earlier this year. Here, we propose equipping the double-nozzle technique with the RF-only funnel and RF-buncher placed in a gas-jet chamber at a 70 mm distance downstream of the double-nozzle exit. It allows for highly effective extraction into vacuum heavy ion beams, produced in two-steps laser resonance ionization in the argon supersonic jet. We explored the operation of this new full version of the double-nozzle technique through detailed gas dynamic and Monte Carlo trajectory simulations, with the results presented and discussed. In particular, our calculations showed that more than 80% of all nobelium-254 neutral atoms, extracted by argon flow from the gas-stopping cell, can then be extracted into vacuum in a form of pulsed ion beam having low transverse and longitudinal emittance.

This paper proposes a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy. We explored the functionality of this new technique through detailed gas dynamic and Monte Carlo atom-trajectory simulations, in which results are presented and discussed. The results of similar computer simulations for JetRIS setup (as a typical representative of the conventional in-gas-jet technique nowadays) are also presented and discussed. The direct comparison of calculation results for the proposed new technique with the conventional one shows that the double-nozzle technique has many advantages compared with the one used in the JetRIS setup at GSI for future high-resolution laser spectroscopic study of heaviest elements. To fully implement the proposed new technique in all existing (or under construction) setups for in-gas-jet laser resonance ionization spectroscopy, it will be enough to replace the used supersonic nozzle with the miniature double-nozzle device described in the paper.

A laser-driven spin-polarized 3He2+-beam source for nuclear–physics experiments and for the investigation of polarized nuclear fusion demands a high-density polarized 3He gas-jet target. Such a target requires a magnetic system providing a permanent homogeneous holding field for the nuclear spins plus a set of coils for adjusting the orientation of the polarization. Starting from a transport vessel at a maximum pressure of 3 bar, the helium gas is compressed for a short time and can be injected into a laser–interaction chamber through a non-magnetic opening valve and nozzle, thus forming jets with densities of about a few 1019 cm−3 and widths of about 1 mm. The target comprises a 3D adjustment system for precise positioning of the jet relative to the laser focus. An auxiliary gas system provides remote target operation and flushing of the gas lines with Ar gas, which helps to reduce polarization losses. The design of the target, its operation procedures and first experimental results are presented.