Steady-state experimental and meanline study of an asymmetric twin-scroll turbine at full, unequal and partial admission conditions

Paper #:
  • 2018-01-0971

  • 2018-04-03
The use of twin-scroll volute turbocharger turbines has gained popularity in recent years. The main reason is the capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetric twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one limb while designing the other limb for optimal scavenging. This research is based on an series production asymmetric turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Despite a number of studies on symmetric twin entry scroll performance, the development of a modeling tool for asymmetric twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage. This study presents the development of a generalized meanline model for a twin scroll turbine, both symmetric and asymmetric, which can be used in the early stages of turbine development. The combination of the meanline model and an in-house one-dimensional gas dynamics code, which is used to model the interaction (cross-talk) between the two limbs, is described. The model is validated against experimental hot gas stand data under full, unequal, and partial admission conditions. Comparing this to the meanline model indicated the importance of the connecting duct and cross-talk model between the scrolls in obtaining satisfactory full admission predictions due to the non-symmetrical features between the scrolls. For the same reason, it is found that the conventional meanline model falls short in predicting the unequal and partial admission performance of an asymmetric twin-scroll turbine. Therefore, a newly developed cross-talk model is proposed to enable more satisfactory unequal and partial admission performance predictions of an asymmetric twin-scroll turbine.
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