Modeling the working process of the roots blower with an ejector attachment and gas bypass through profiled windows on the housing

The results of mathematical modeling of the Roots supercharger working with gas bypass from the discharge to the suction through the ejector and the suction of an additional portion of the gas are presented. A distinctive feature of the simulated system is that the place of supply of the bypass gas from the ejector diffuser into the cut-off working cavity are end windows having a profile defined by the contour of the rotor blade. The CFD calculation of the flow in the ejector under the conditions of pressure change at the outlet from the diffuser was carried out separately. The dependences obtained for the ejection coefficient are included in the mathematical model of the supercharger, which is based on the principle of the thermodynamic model of the control volume. The indicator and temperature diagrams of the supercharger workflow were obtained and analyzed depending on the pressure ratio, which are presented in comparison with the modes of operation without an ejector and with another method of bypass through radial slots on the body.