Hydrodynamic performance of liquid film seals in circumferential beveled-step spiral grooves
(2.CNPC Dushanzi Petrochemical Company, Kelamayi, Xinjiang, China 833699)
【Abstract】To reduce liquid film pressure loss in liquid flow divergent zone between sealing surfaces and to improve sealing performance, the structure of circumferential beveled-step was introduced into rectangular section spiral groove and corresponding physical model was established. Based on the JFO cavitation model, the effects of bevel angle ratio on liquid film pressure distribution, cavitation occurrence, and liquid film hydrodynamic performance were studied at different groove depths. When bevel angle ratio was below 1/30, liquid film pressures of downstream and upstream pumping liquid film seals along circumferential and spiral line direction were enhanced rapidly but cavitation area ratio was dropped sharply, which was more significant for upstream pumping seals. With the increase of bevel angle ratio, leading edge pressure at liquid film rupture showed an increasing trend and trailing edge pressure at liquid film reformation showed opposite trend, but cavitation area ratio increased first and decreased later. The increase of groove depth contributed to the increase of liquid film pressure and the decrease of cavitation area ratio. When groove depth ranged from 8 to 12 μm and bevel angle ratio ranged from 0.1 to 0.3, the load-carrying capacities of both liquid film seals reached to peak values with about 13.5% maximum amplification for the former and about 28% for the latter, whereas increase of friction torque was smaller with about 4.6% maximum amplification. The leakage change along with the increase of bevel angle ratio was similar to the load-carrying capacity.
【Keywords】 spiral groove liquid film seals; circumferential beveled-step; hydrodynamic performance; liquid film pressure; cavitation area ratio;
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