Numerical Modelling of a Turbocharger Splitter-Vaned Centrifugal Impeller at off-Design Conditions Part II:Computation of Forces and Torques

Forces and torques acting on each individual blade and on the shaft of a centrifugal impeller with splitter vanes working at off-design conditions, are computed by using the pressure integration and the momentum balance method. Two cases are examined simulating the operation of a centrifugal compressor at higher mass flows than the optimum one: the first where the Strouhal number, S, = 0.14 6 , corresponds to subsonic flow inside the impeller and the second one where the Strouhal number, Sr = 0.225 , corresponds to transonic flow inside the impeller. For the first case, the variation of forces is more distinct in the circumferential location where the volute tongue is located. For the second case a bimodal distribution is observed per impeller rotation. Calculations done for impellers with backward leaned blades and with radial ending blades demonstrate the influence of the impeller exit geometry to the radial force.