Construction of NovelInvolute Rotor Profile for Roots Pump with Higher Maximum Shape Factor

Novel involute rotor profile, with higher maximum shape factor, was constructed based on involute gear profile.The discussions focused on i) construction of involute profile equation; ii) calculation of maximum shape factor; and iii) profile intervention between rotors and possible solution.The results show that the new rotor's top-arc effectively reduces the radial leakage and improves the volumetric efficiency; when it comes to new maximum shape factor with addendum half-angle of 0°~5°, the increases, by 9.3%~4.3% for two lobes, by 13%~6.2% for three lobes and by 13.9%~5.8% for four lobes, were achieved.The peak involute profile comprises transition and conjugate profiles.Unfortunately, the transition profile interferes with the basic point of its paired rotor profile, but an alternative peak profile with concave arc is capable of removing such profile interference, alleviating dynamic unbalance of rotors and simplifying its fabrication.