Instruments and Experimental Techniques最新文献

This study designed a visualization experimental system for investigating the flow characteristics and phase transition processes during small-hole leakage of supercritical CO₂ pipelines. This experimental system introduces innovations in the test pipeline, observation window, and release valve assembly, which expand the observation range and improve the universality of the experimental conclusions. In this study, experiments on supercritical CO₂ release were conducted at various initial temperatures using this system. The results indicated that the evolution process of supercritical CO₂ leakage can be categorized into three stages: supercritical, vapor-liquid phase, and vapor phase. During the transition from supercritical to vapor-liquid phase, the depressurization rate significantly decreased, leading to the formation of an inflection region on the depressurization curve. The initial temperature notably influenced both the pressure level and duration of the inflection region. When the initial temperature exceeded 55°C, the inflection region disappeared, and the release process of supercritical CO₂ became similar to that of vapor CO₂. These experiments also demonstrated the reliability of the experimental system.

The study provides a detailed account of the Stereolithography (SLA) additive manufacturing process used to manufacture a Blended Wing Body (BWB) model for low-subsonic wind tunnel testing. It examines the feasibility of SLA for fabricating aerodynamic models, focusing on material properties, minimum feature sizes, internal channel design, and post-processing techniques such as curing, support removal, and surface finishing. The research highlights the advantages of SLA in achieving complex geometries with smooth surfaces and fine details, demonstrating its potential as a cost-effective and efficient method for manufacturing wind tunnel models. Considerations for structural integrity, print resolution, and surface treatment are explored to enhance model accuracy. The study also outlines best practices for optimizing the manufacturing process to ensure reliable and repeatable production, making SLA a viable approach for rapid prototyping in aerodynamic research.

This paper proposes a method of passive reference reflectometry based on the use of references with known localization and constant reflection coefficients within the transmission path. A comparison of different approaches to implementing passive references is presented. To enhance identification reliability, paired inhomogeneities are introduced as references, generating responses with opposite polarities. Model and experimental studies are carried out with the use of a 519-mm in length coaxial probe, with diameters of the screen and central conductor of 12 and 5 mm, respectively, with the inclusion of five equidistant paired references. The applicability of the passive reference reflectometry method for determining the relative permittivity along the path length is concluded. For this probe, when measuring a multilayer medium consisting of air, technical oil, and distilled water, the experimental error of the relative permittivity was less than 7.9% and that in the cases when the interface boundaries are located near the references is up to 34.7%. Thus, the application of the proposed method allows for determining or refining the relative permittivity of layers. This can be useful in the problems of level measurement to improve the accuracy of level determination and to obtain information about the qualitative characteristics of layers of multilayer media.

Continuous spectrum radiation in the frequency range of 2–4 GHz is generated by a plasma relativistic source. The pulsed radiation is fed into a rectangular waveguide measuring 72 × 34 mm² with the substance under study. A piston is inserted into the waveguide, and the refractive index of the substance is determined by the appearance of the interference pattern. The substance in the waveguide can be a gas or have the form of a rectangular bar or a cuvette with liquid. It can be used for spectroscopy of dielectrics.

A research software and hardware complex for measuring the surface adhesion factor by the method of tearing off a preliminarily pasted adhesive tape at a constant speed at an angle of 90° is presented. The design of the adhesimeter and the main screen of the data-processing program interface are presented. The experimental procedure is described. The results of the experiment proving that the adhesive interaction between the adhesive layer and the surface is measured are given. The experiment that demonstrates the sensitivity of the complex to a change in the surface adhesion is presented. This is especially important for conducting research.

The design of the upgraded front-end card (FEC) of the ALICE/CERN Photon Spectrometer experiment is described. The development of the new FEC is associated with an increase in the luminosity and energy of the Large Hadron Collider beams and with the need to increase the accuracy of time-of-flight measurements for the better identification of detected particles. The available FEC of the photon spectrometer does not meet the new requirements and must be replaced according to the upgrading plan. The improvement of FEC measurement performance is achieved through hardware-based measurement of the flight time instead of offline processing of photodetector waveform digitization codes. The upgraded FEC contains 32 measuring channels and all functional modules necessary for the photon spectrometer operation. The functional modules are described. The characteristics of the upgraded FEC have been measured on the PS/SPS test beams at CERN in the momentum range of 1−150 GeV/c. Based on these results, it is concluded that the developed card fully complies with the requirements for the FEC of the upgraded photon spectrometer.

A femtosecond laser pulse oscillator based on a Yb:KGW crystal with a repetition rate of 78 MHz and an average power of 2.3 W has been developed. The generated pulse duration is approximately 170 fs with a spectral width at half maximum of approximately 7 nm, with a central wavelength of 1031 nm. High stability of average power and diffraction-limited quality of radiation allow the device to be used as a precision source of femtosecond pulses for various high-power amplifiers, including widely used amplifiers based on Yb:YAG crystals.

The hard X-ray diagnostic is an important system for tokamak, primarily used to measure the hard X-rays emitted by fast electron bremsstrahlung to obtain the intensity and energy information of fast electrons. The system is crucial for understanding physical phenomena such as lower hybrid wave energy deposition location, fast electron intensity and energy, fast electron transport, high energy instability, etc. To meet the demanding requirements of the next generation compact burning plasma tokamak characterized by physics research of high parameters plasma and intense magnetic field environments, it is imperative to enhance both the energy resolution of primary electronic systems and their capability to withstand strong magnetic fields. In this paper, a main electronic system is developed for the diagnostic system of hard X-ray intensity and energy spectrum distribution of the next generation compact burning plasma tokamak. The main electronic system is composed of an analog signal conditioning circuit, ADC (Analog-to-Digital Converter), an FPGA (Field-Programmable Gate Array), and a 10 Gigabit data communication interface, which can analyze multi-channel energy spectrum. Through the testing with ¹³⁷Cs radioactive source, the main electronics system can achieve the energy resolution of 2.9%@662 keV by a CZT (Cadmium Zinc Telluride) detector. It can also operate normally in a strong static magnetic field environment with the magnetic field strength of 160 mT. When operating in the EAST Tokamak, the main electronics of hard X-ray diagnostic can be running stably and providing reliable analytical data.

An experimental method for obtaining the spatial electrical-conductivity distribution during detonation of solid organic explosives is described. The results of a numerical simulation are presented, the accuracy of the experimental results is assessed, the justification of the method for determining the width of a high-conductivity zone is discussed, the data on the effect of the measuring-system geometry on the measurement result are provided, and the advantages, limitations, and capabilities of the technique are discussed in detail.

Study into the aerodynamics of unmanned aerial vehicles (UAVs) requires simulation of atmospheric flows in laboratory conditions taking into account wind gust. Traditional wind tunnels do not generate flows similar to the real atmosphere, which is characterized by significant spatial nonuniformity and unsteadiness of flow. This paper considers a multifan wind tunnel developed at Khristianovich Institute of Theoretical and Applied Mechanics (Siberian Branch, Russian Academy of Sciences) as a promising tool for simulation of the atmospheric turbulence. The main measurements were made by hot-wire anemometer and PIV. Data on turbulence and nonuniformity generated by a multifan wind tunnel (MfWT) have been obtained. The effect of the flow quality on the aerodynamic characteristics of the UAV was analyzed. The cross-sectional area of the test section of the wind tunnel is approximately 0.7 m² and the maximum velocity of the flow is 10 m/s.