282 / 2021-04-15 23:57:31

A CO-SIMULATION MODEL FOR SIMULATING TURBOCHARGER ROTORS WITH BALL BEARINGS

co-simulation,2 phase model,rotor-bearing system

On the one hand, stringent emission regulations are challenging automobile manufacturers to design engines that meet the needs of these environmental regulations. On the other hand, vehicles are desired that are enjoyable to drive. Turbochargers meet that challenge and deliver significant benefits to end-users. A turbocharger is a system that uses the exhaust gas of the engine in order to compress the air, which is supplied to the engine. The main part of a turbocharger consists of a rotating shaft with two wheels, namely a turbine wheel and a compressor wheel. The rotating shaft is supported by an appropriate bearing system. Usually, oil-film bearings are used in turbocharger applications. Alternatively, ball bearings can be applied, which have the advantage that the friction losses are reduced. Since ball bearings exhibit only less damping/friction, squeeze-film dampers are used in order to introduce damping into the rotor system.



Here, a detailed numerical model is presented for turbochargers supported by ball bearings; the model also includes an external squeeze-film damper. For the ball bearings, an analytical 2D-model approach based on Hertzian contact theory is used. The bearing forces acting in the squeeze-film damper, are calculated with the Reynolds equation for thin fluid films. The Reynolds equation is a partial differential equation, which is solved numerically by a finite element approach. The rotor is modeled as a flexible multibody system. Hence, the discretized Reynolds equation–represented by a system of nonlinear algebraic equations–has to be solved in every time integration-step in parallel with the multibody system. To reduce the simulation time, a computationally efficient semi-implicit co-simulation approach is used here.