Effect of Quench Polish Quench Nitriding Temperature on the Microstructure and Wear Resistance of SAF2906 Duplex Stainless Steel

The effect of quench polish quench (QPQ) nitriding temperature on the microstructure and wear resistance of SAF2906 duplex stainless steel was investigated. Results showed the surface of the nitrided samples was composed of an oxidized layer, a loose compound layer, a compact compound layer, and a diffusion layer. The oxidized layer was composed of Fe3O4. The main phases of the loose compound layer were CrN, alpha(N), Fe2-3N, and Fe3O4. The compact compound layer was composed of CrN, alpha(N), and Fe2-3N. In the diffusion layer, CrN and expanded austenite (S) were the main phases. The nitrided layer thickness increased from 20 to 41 mu m with an increasing temperature of 570 to 610 degrees C. When the nitriding temperature was above 590 degrees C, the precipitates in the diffusion layer became coarsened, and their morphologies gradually changed from spherical particulate to rod-like and flocculent-like. Tribotests showed the cumulative mass loss of QPQ-treated samples was much lower than that of the substrate. The cumulative mass loss of the samples nitrided at 610 degrees C was higher than that at 570 degrees C during the first 29 h. When the test time was over 29 h, the former was lower than the latter

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Modeling aluminum (Al) particle-air detonation is extremely difficult because the combustion is shock-induced, and there are multi-phase heat release and transfer in supersonic flows. Existing models typically use simplified combustion to reproduce the detonation velocity, which introduces many unresolved problems. The hybrid combustion model, coupling both the diffused- and kinetics-controlled combustion, is proposed recently, and then improved to include the effects of realistic heat capacities dependent on the particle temperature. In the present study, 2D cellular Al particle-air detonations are simulated with the realistic heat capacity model and its effects on the detonation featured parameters, such as the detonation velocity and cell width, are analyzed. Numerical results show that cell width increases as particle diameter increases, similarly to the trend observed with the original model, but the cell width is underestimated without using the realistic heat capacities. Further analysis is performed by averaging the 2D cellular detonations to quasi-1D, demonstrating that the length scale of quasi-1D detonation is larger than that of truly 1D model, similar to gaseous detonations

Development of A Maintenance Device for Bus-bar PT Voltage Air Switch

When PT breaks down, it takes long time of switching operation before maintenance, which seriously delays the restoration time. Based on the principle of multiple circuit, a live replacement maintenance device for PT voltage air switch is proposed. The following aspects are involved in the design of the device: the principle of device, component selection, device’s assembly and operation process. Through functional test in simulation substation and on-site installation, it is proved that the failed air switch can be lively replaced by the device without switching operation, which greatly reduces the risk on power grid caused by such faulted air switch

Development of A Maintenance Device for Bus-bar PT Voltage Air Switch

When PT breaks down, it takes long time of switching operation before maintenance, which seriously delays the restoration time. Based on the principle of multiple circuit, a live replacement maintenance device for PT voltage air switch is proposed. The following aspects are involved in the design of the device: the principle of device, component selection, device’s assembly and operation process. Through functional test in simulation substation and on-site installation, it is proved that the failed air switch can be lively replaced by the device without switching operation, which greatly reduces the risk on power grid caused by such faulted air switch

The initiation characteristics of oblique detonation in acetylene-air mixtures in the finite wedge

Oblique detonation waves (ODWs) have been widely studied due to their application in hypersonic propulsion. Most of the previous studies focus on hydrogen fuel, and the induced wedge is always infinite. In this paper, based on the detailed chemical reaction model, the two-dimensional multi-component Euler equations are solved, and the finite wedge-induced oblique detonations for acetylene-air mixtures are investigated numerically and theoretically. Effects of expansion waves, inflow Mach number and equivalence ratio (ER) on initiation characteristics of ODW are studied according to the initiation criterion in the confined space. Results show that the initiation distance of acetylene is relatively larger than the hydrogen fuel, and the convergence position of deflagration waves and the originated position of expansion waves determine the initiation characteristics of ODW. As the originated position of the expansion wave is downstream of the convergence position of the deflagration, the ODW is ignited; Otherwise, the ODW is not initiated. The characteristics length of induction zone presents a U-shaped curve distribution for different ERs, both fuel-rich and lean-burn conditions will result in the non-initiation of ODW

The initiation characteristics of oblique detonation in acetylene-air mixtures in the finite wedge

Oblique detonation waves (ODWs) have been widely studied due to their application in hypersonic propulsion. Most of the previous studies focus on hydrogen fuel, and the induced wedge is always infinite. In this paper, based on the detailed chemical reaction model, the two-dimensional multi-component Euler equations are solved, and the finite wedge-induced oblique detonations for acetylene-air mixtures are investigated numerically and theoretically. Effects of expansion waves, inflow Mach number and equivalence ratio (ER) on initiation characteristics of ODW are studied according to the initiation criterion in the confined space. Results show that the initiation distance of acetylene is relatively larger than the hydrogen fuel, and the convergence position of deflagration waves and the originated position of expansion waves determine the initiation characteristics of ODW. As the originated position of the expansion wave is downstream of the convergence position of the deflagration, the ODW is ignited; Otherwise, the ODW is not initiated. The characteristics length of induction zone presents a U-shaped curve distribution for different ERs, both fuel-rich and lean-burn conditions will result in the non-initiation of ODW

Study on initiation characteristics of oblique detonation induced by hydrogen jets in acetylene-air mixtures

In this paper, effects of hydrogen jets in acetylene-air mixtures on the initiation characteristics of oblique detonation wave (ODW) are investigated, the two-dimensional (2D) multi-component NS equations considering detailed chemical reactions are solved. Influences of the transverse jet on flow field characteristics of the ODW are studied, including the initiation characteristics, the wave structures, and the state parameters. The existence of the jet changes the ignited mode of the ODW from double Mach interaction to single Mach interaction. Several wave configurations and their transitions induced by the jets are observed, including deflagration-to-detonation transition (DDT), jet-induced bow shock wave (BSW) in front of the transverse jet and rapidly develops into ODW, and ODW that generated directly in front of the transverse jet. The structure of these three wave systems is mainly influenced by the flow discharge of the hydrogen jet. When the hydrogen jet is small, no combustion is induced by the BSW in front of the jet. ODW is induced by the action of the deflagration wave and OSW. Increasing the hydrogen jet, BSW induces combustion and rapidly develops into ODW. When the hydrogen jet is large enough, the BSW disappears and direct detonation combustion occurs to produce ODW. Two types of relationships are obtained between the initiated position and the position of the transverse jet: the U-shaped curve at low flow discharge and the positive correlation at high flow discharge. When the flow discharge is small and no shock wave-induced combustion occurs, the initiated position is influenced by the position of the deflagration wave interacting with the OSW, which forms a U-shaped curve with the position of hydrogen jet. When the flow discharge is high and shock wave induced combustion occurs, ODW is rapidly developed behind the jet, resulting in a positive correlation between the initiated position and the position of hydrogen jet. Furthermore, the viscous effect has significant influence on the flow field characteristics of ODW, it promotes the transition between these initiation modes and shortens the initiation distance of oblique detonation. The findings of this study can better help understand the effect of transverse hydrogen jets on ODW initiation and contribute to theoretical studies and engineering applications of oblique detonation engines

Licorice protects against ulcerative colitis via the Nrf2/PINK1‐mediated mitochondrial autophagy

Abstract Purpose Study of the effects and mechanisms of licorice in the treatment of ulcerative colitis (UC) from the perspective of mitochondrial autophagy. Methods BALB/C mice were induced with 3% dextran sodium sulfate to build an animal model of UC. After 7 days of modeling, different doses of licorice were administered for 7 days. Hematoxylin and eosin staining is used to detect pathological changes in the colon. Mitochondrial membrane potentials and reactive oxygen species (ROS) contents were detected by flow cytometry, and autophagy of mitochondria was observed by transmission electron microscopy. Determination of inflammatory cytokines by enzyme‐linked immunosorbent assay. The oxidizing factors are detected by the kits. Western blot analysis was used to detect expressions for nuclear factor called erythropoietin (Nrf2), pten‐induced protein kinase 1 (PINK1), Parkin, HO‐1, P62, and LC3. Results Licorice improved the pathological condition of UC mice, increasing the mitochondrial membrane potential and decreasing the ROS content. Promotes the emergence of autophagosomes and autophagosomes. The contents of interleukin (IL)‐1β, IL‐6, IL‐17, and tumor necrosis factor‐alpha were downregulated, the contents of superoxide dismutase and glutathione peroxidase were upregulated and the contents of malondialdehyde were downregulated. In addition, licorice promotes the expression of Nrf2, PINK1, Parkin, HO‐1, P62, and LC3. Conclusion Licorice was shown to reduce levels of inflammatory factors and oxidative stress in mice with UC, possibly by promoting mitochondrial autophagy through the activation of the Nrf2/PINK1 pathway