The application of active control for turbocharger turbines

In this paper, the motivation behind the development of an active control turbocharger is presented, along with the initial thinking that led to the basic concept of applying active flow control at the inlet to a turbocharger turbine. In addition, the concept of active control for turbochargers is analysed in depth with the purpose of presenting a theoretical basis for any subsequent application of this type of control of exhaust gas flow into a turbocharger turbine by providing the fundamental thermo-fluids background. Secondly, the aim was not only to merely present a theory summarising the behaviour of the exhaust gas flow occurring during turbocharger turbine inlet geometrical changes, but to also present the implications from the periodic nature of these geometric changes, in particular with respect to cycle performance results both for the turbocharger and for the engine. The effects of the application of active control turbochargers were demonstrated through testing of the first prototype active control turbocharger built and tested at the aerodynamic test facility at Imperial College and through the experimental data collected. In this first attempt, at the most favourable amplitudes tested, the power recovered reached a maximum value of 7.5% increase over the equivalent variable geometry turbocharger performance, although this depended on the phasing of the turbine inlet area variation in relation to the energy content variation of the incoming exhaust pulse.