This paper introduces research work on 1-D model of Roots type supercharger with helical gears using 1-D simulation tool. Today, passenger car engine design follows approach of downsizing and the reduction of number of engine cylinders. Superchargers alone or their combination with turbochargers can fulfill low-end demands on engine torque for such engines. Moreover, low temperature combustion of lean mixture at low engine loads becomes popular (HCCI, PCCI) requiring high boost pressure of EGR/fresh air mixture at low exhaust gas temperature, which poses too high demands on turbocharger efficiency.
The main objective of this paper is to describe Roots charger features and to amend Roots charger design. The presented analysis tool is a 1-D model of Roots type supercharger respecting inlet and outlet processes due to the change of volume between teeth, fast compression in the gap between teeth after connecting the compressor outlet, mass flow losses caused by teeth mesh and casing clearances and additional compression/expansion between meshing-in teeth. Finding the geometrical data (variable volumes, surfaces and cross-section areas) is based on newly developed procedures using scripts in 3-D solid CAD model, in which teeth meshing was simulated. The developed model has been calibrated using supercharger map measured at a test rig.
The model constructed from 1-D model modules has been used for sensitivity analysis considering design data. It can be connected to engine model and easily used for supercharger map extrapolation.