Effect of different startup modes on the cavitation performance in Rotary lobe pump

Abstract

This present paper therefore used the dynamic mesh of FLUENT, RNG k-ε turbulence model and Z-wart-Gerber-Belamri cavitation model are used to simulate a rotary lobe pump with unsteady method. Meanwhile the instantaneous flow field distribution and its internal cavitation of rotary lobe pump are analyzed. We also gave the judgment of incipient cavitation. At the same time the cavitation area and the inlet pressure of the lobe pump are determined under the conditions of incipient cavitation, critical cavitation, developing cavitation and complete cavitation. The results show that the bubble occurs firstly in the rotor meshing of the suction cavity, and with the rotation of the rotor, the cavitation is brought into the adjacent transition region, forming the attached cavitation bubble. In different linear startup modes, it can be seen that with the increase of rotational speed, it is easier to form a local low-pressure region at the meshing gaps between two rotors and the pump cavity. When the startup time is 0.1s, the diffusion of the low-pressure region of the inlet section is effectively suppressed, so the volume of the bubble is obviously reduced. Moreover, the critical NPSHc of the lobe pump is 3.59m and the critical cavitation point flow rate is 20.85m3/h, which is in good agreement with the experimental data.