RESUMEN
The gap leakage between the impeller ring leads to the change of the pump cavity flow characteristics, resulting in the uneven pressure distribution of shroud, which causes the axial force of the cavity to change. In this paper, the flow in the front and the rear cavity of the multistage centrifugal pump was taken as the research object. Through the numerical method, the radial flow velocity, the leakage flow size and its direction, the core zone rotation factor of the front and the rear cavity of the multistage pump impeller at all stages and the axial force of pump cavity were studied. The results show that the leakage in the front cavity of multistage pump impeller at all stages flows inward along radial direction (i.e. it flows from the inlet of pump cavity to the front ring clearance). The rotation factor in core zone is higher than 0.5, and with the increase of rotation factor, the axial force of the front pump cavity increased. The leakage in the rear pump cavity flows outward along radial direction (i.e. it flows from the rear ring to the inlet of pump cavity). The rotation factor in core zone is less than 0.5, and with the increase of rotation factor, the axial force decreased gradually. Besides, the radial velocity and rotation factor in the front and the rear multistage pump of impellers were obviously along the axial direction at three regions, the regions are pump case boundary layer, core zone and impeller boundary layer. The flow in the core zone is dominated by circumferential circular motion, and the radial velocity in the core zone is 0. It is shown that the direction of the leakage in the pump cavity and the rotation effect of the flow micelle in the mainstream core zone are the main factors affecting the axial force of the pump cavity, and the research results can provide theoretical guidance for the calculation and suppression of axial force of multistage pumps.
RESUMEN
[Objective]To explore the effect of alpha2-macroglobulin(α2M)on superoxide anion(.O2-)content, superoxide dismutase(SOD)activity and the process of cell-to-myofibroblast transformation in human skin fibroblasts (HSF)after X-ray irradiation.[Methods]HSF cells were irradiated with 0,5,10,15 and 20 Gy X-ray.The change of. O2- content and SOD activity in the supernatant of cell culture medium were measured on the first day after irradiation. The protein expression of alpha-smooth muscle actin(α-SMA)was detected by Western blot on the fifth day after irradia-tion.The most sensitive radiation dose is selected.HSF cells were irradiated with the above sensitive dose.Respectively, 1h before irradiation,1 h after irradiation,the experimental group cell culture medium was added to a final concentration of 0.25 mg/mL,0.5 mg/mL of α2M.The change of.O2-content,SOD activity and the protein expression of α-SMA were detected.[Results]HSF cells were irradiated with 5~20 Gy doses of X-ray..O2- content increased,SOD activity de-creased and α-SMA protein expression increased gradually(P<0.05).The addition of α2M at 1 h after 10Gy X-ray irradi-ation reduced the.O2- content,increased the SOD activity and downregulated the protein expression of α-SMA in HSF cells(P<0.05). There was no significant change in the administration at 1 h before irradiation.[Conclusion]HSF cells increased.O2-content significantly,while SOD activity decreased,and the tendency to transform myofibroblasts after X-ray irradiation.α2M can reduce the.O2-content,increase the SOD activity in HSF cells and inhibit the transformation of fibroblasts into myofibroblasts after irradiation.Indicating that α2M can play a role in radiation protection by anti-oxida-tion and anti-fibrosis.