Analytical Model of a Particular Type of Positive Displacement Blower

Many papers exist in literature which deal with the twin screw compressor; this usually has two different rotors, a male and a female, and is commonly used to produce compressed gas for industrial uses. However, a different type of positive displacement rotary compressor with two screws is sometimes used; one of its typical applications is in car engine supercharging. Present paper deals with the latter type, which is defined as a two screw blower. This blower has two identical helical rotors, each with three lobes. The kinematics and the geometry of the rotors are analysed here, and a complete mathematical model for the rotor is defined. Moreover different possible shapes of the rotors, depending on the design parameters, are analysed and the limitations in the choice of the design parameters are presented. Finally an analysis of the theoretical specific slipping of the rotors is presented, showing which zones of the profile are the most stressed. This model will be useful for further studies on rotor pressure loads and blower dynamics.