Papers by Keyword: Gas Flow

Abstract: Seed crystal stabilization during the initial stage of 200-mm 4H-SiC crystal growth is critical for achieving high-quality wafers with large diameters. This study investigated the effects of heating ramp rates (0 - 6 °C/min) and SiC source powder porosity through both simulation and experimental approaches. Low ramp rates resulted in surface degradation of the seed crystal, whereas high ramp rates induced significant thermal stress, leading to cracking. Optimal ramp rates of 3 - 5 °C/min significantly minimized damage caused by seed crystal loss. Furthermore, high-porosity source powder facilitated adequate gas transport channels, thereby enhancing seed crystal stability. Crystals grown under these optimized conditions demonstrated improved edge morphology, absence of polycrystalline inclusions, and low dislocation densities, with threading screw dislocations (TSD) below 500 cm^-2 and basal plane dislocations (BPD) below 1,000 cm^-2. These results demonstrate that precise control of thermal parameters and source powder porosity offers an effective strategy for stable seed attachment and reproducible growth of high-quality, large-diameter SiC single crystals.

Abstract: The paper is devoted to the issues of energy saving automatic control of radial burden distribution in the blast furnace throat. The main idea consists in control with prediction of the control resulting on the basis of automatic monitoring of burden surface texture. The paper develops the mathematic description of burden surface texture on the blast furnace throat by means of substantiation of minimum quantity of general indicators of the mixture being closely related to the main parameters of blast furnace processes. It is the first time that the optimum value of hoper depth in burden surface at 0.14 – 0.2 of throat diameter determined, the methods of its stabilization at the rate are substantiated, the new regularity of burden surface formation on the operating blast furnace throat is shown as consisting in the fact that the hoper depth on the surface is mainly changed responding the process of material charge rather than bulk material descent after the charge. It was also substantiated for the first time that radioisotopic methods for current control of burden distribution on the blast furnace throat provide timely formation of control actions for gas flow stabilization. The principle of self-tuning was theoretically substantiated for monitoring system of gamma profilometer responding to the monitoring conditions with respect to high penetration and random character of gamma rays. The principle enables significant improvement of accuracy, quick-response and radiological safety of gamma profilometer operation. The possibility of determination of burden surface texture on the throat of operating blast furnace and distribution of burden components according to infrared radiation of the surface without application of radiation hazardous monitoring means was proved for the first time.

Abstract: In the paper nonlinear vibrations of a drill string’s section in a supersonic gas flow are studied. The drill string is modelled in the form of a circular cylindrical shell under the effect of a longitudinal compressing load and torque. In contrast to the previous research, pressure of an unperturbed gas is defined nonlinearly in the third approximation. The eighth order partial differential equation describing the motion of the shell reduces to a nonlinear system of ordinary differential equations with application of the Bubnov-Galerkin technique. An implicit Runge-Kutta method is applied to construct modes of vibrations.

Abstract: The paper describes a plasma source based on a self-sustained volume discharge for diamond and diamond-like film deposition. The suggested scheme of the electrode system enables to provide stable combustion of the self-sustained volume discharge with high pulse repetition rate in atmospheric pressure gases. Gas flow rate to blow off the interelectrode gap depending on the anode temperature has been considered.

Abstract: Using numerical experiment the gas flow in the gravity field through a plane porous object with heat sources inside and partial closure of the object's outlet has been investigated and compared with axisymmetric case. The influence of partial closure of the object's outlet on the cooling process of the plane porous objects with a non-uniform distribution of heat sources has been analyzed by means of computational experiment. It has been revealed that effect of the top cover on a cooling process of the plane porous objects is qualitatively the same as in the axisymmetric objects, but quantitative differences are significant.

Abstract: The gas concentration field in goaf of Huangling No.1 Mine 304 fully-mechanized face was simulated numerically by FLUENT software with high fracture drilling or not. The results of numerical simulation were confirmed by fixed sampling method of immersed tube in goaf. Thus, the law of gas concentration field was gained, which provides the important basis for gas control of working face.

Abstract: With the rapid development of the world economy, energy has become tighter. Industrial equipments play an important role in the development process of the world economy, at the same time they also consume a lot of energy. Equipment selections are related to the different working conditions, such as temperature, pressure, load, economy etc. Reasonable and scientifically select the equipment and the auxiliary devices can meet the specifications required, while also help on energy saving and consumption reduction. In this article, this paper discusses on the reasonable correct selection of the 2BE1 series water ring vacuum pumps in the chemical industry.

Abstract: A novel gas flow sensing probe based on silver-coated Fiber Bragg Grating (FBG) is proposed. A square hole was fabricated in the middle of a capillary stainless steel pipe. A silver-coated FBG sensing probe was fixed up between the hole. The diameter of the silver-coated FBG sensing probe is only 0.125 mm, with the PVC materials deposited around the surface of the both ends with a diameter of 0.9 mm. Simulations on different packages of sensing probe were carried out via Finite Element Method (FSM). Results of the simulations reveal that the sensing probe of the capillary stainless steel pipe with a diameter of 3 mm and the square hole with a length of 12 mm can provide the best performance.

Abstract: Experiments were carried out to learn about the frictional resistance of gas flow in vertical helically coiled pipe. The expression of friction factor was established and the formula used to calculate the frictional resistance of gas flow in vertical helically coiled pipe was defined based on partial data got from different experiment conditions. The calculating formula was verified by the experimental data. The results show that the formula is accurate enough to calculate the frictional resistance of gas flow in similar operating conditions.

Abstract: The in-plane thermoelectric generator (TEG) was ingeniously designed when the thermal gas flowed over the carbon nanotube (CNT) membrane at the modest speed of a few meters per second. It was composed of the glass substrate, aurum electrodes and CNT membrane synthesized by a floating catalyst chemical vapor deposition method. In the air under atmospheric pressure, the experimental results showed that the maximal output voltage could reach 1.7 mV. It related not only with the temperature difference between the hot-side and cold-side, but also the temperature gradient of the CNT membrane which was closely dependent on the velocity and temperature of the gas flow. The multi-physical power mechanism was applied to interpret the energy conversion, which included the coupling relation of the fluid dynamics, heat transmission and Seebeck effect. This novel method could effectively enhance the output voltage, extend the applied range of TEG and had a fine prospect.