| 论文简介 |
In this paper, the dynamic failure of the two-phase ejector in
a modified auto-cascade freezer system was experimentally investigated in
the pull-down process. The effects of the critical ejector geometries
including the nozzle throat diameter, mixing section diameter and nozzle
exit position on the ejector performance were discussed in detail. The
entrainment ratio and pressure lift ratio were used to evaluate the
ejector performance. The failure behaviors of the pressure rise and fluid
entrainment at different ejector geometries were analyzed. The results
showed that improper ejector geometry could contribute to the pumping
failure of the ejector. The operation reliability of the ejector was
sensitive to the nozzle throat diameter. Low mass entrainment ability and
poor mixing effect for the mixing fluids were the main reasons of pumping
failure for the ejector at undersize and overlarge mixing section
diameters, respectively. Pressure lifting failure was prone to occur at
smaller NXP, and the pulsation of the pressure lift ratio became obvious
at large NXP when the secondary fluid was at two-phase state. The
variation of temperature at the secondary fluid inlet was an important
symbol of detecting the reverse flow of the primary from the secondary
fluid inlet. The ejector with throat diameter of 0.8 mm, mixing section
diameter of 3 mm and NXP of 6 mm was proposed in consideration of the
ejector operation reliability and the fastest pull-down speed for the
freezer air in this prototype, and the time-average value of the pressure
lift ratio could reach 2.197 at the entrainment ratio of 0.663. |
(创新港)
