Construction of Parabolic Rotor Profile with Rostellum Geometry for Roots Pump:A Simulation Study

A new rostellum parabolic rotor with an arc-shaped top was developed to enhance the shape coefficient and volume utilization rate.The shape coefficients and volume utilization rates of both the novel rostellum and conventional circular (or involute) rotors were numerically calculated.The calculated results show that the rostellum-rotor significantly outperforms the conventional circular rotor.To be specific, the bottom-heavy cross-section of rostellum-rotor improves the dynamic balance of Roots pump;as the half-angle increases, its max shape coefficient decreases, depending weakly on the lobe number (1.58, 1.48 and 1.41 for 2, 3 and 4 lobes, respectively) .For 2 lobes and in 1°~8° range, the max shape-coefficient and volume-utilization rate of the rostellum-rotor are 0.6%~8.16% and 2.68%~16.79%, respectively, higher than those of the conventional ones.Besides, for 3 and 4 lobes, the rostellum-rotor has higher max shape-coefficient/volume utilization-rate/volume-efficiency than the circular (or involute) rotor does.