Detailed Study of Pulsating Flow Performance in a Mixed Flow Turbocharger Turbine

Abstract

Automotive turbocharger turbines experience a highly unsteady and pulsating flow field due to the abrupt operation of the exhaust valves in a reciprocating internal combustion engine. Previous work has demonstrated and validated against experiment a computational model of a turbine stage under such conditions. The same model is used in the present paper to examine in greater detail the complex flow characteristics observed. The pulsating inlet condition results in a highly disturbed flow field in the turbine stage, the main features of which have already been identified. The effect of the passing of the blades at the volute tongue is observed, and the fluctuating velocity field in the blade passages is seen to lead to poor flow direction control at the turbine inlet and exit. The turbine geometry, calculated for steady flow, is forced to operate away from design conditions for most of the pulse period. Through a detailed analysis of the intricate flow field features at varying instants during the pulse period, this paper highlights areas of the blade geometry and periods in the pulse profile that should be investigated further, such that the integrated performance across the entire pulse cycle can be improved.

Untersuchung und Charakterisierung einer zweiflutigen asymmetrischen Radialturbine

“…Die Frage nach der Gültigkeit der quasi-stationären Betrachtung des Strömungsverhaltens der Turbine unter motorischen Randbedingungen wird in der Literatur unterschiedlich beantwortet. Baines et al (1994) und Costall et al (2005Costall et al ( , 2007 haben 1D-Turbinenmodelle für instationäre Turbinenrandbedingungen vorgestellt. Die Turbinenvolute wurde über ein Volumen in der Modellierung berücksichtig, während das Verhalten des Turbinenrotors als quasi-stationär kennfeldbasiert beschrieben wurde.…”

“…In den Arbeiten von Costall (2005) In der Literatur werden unterschiedliche Herangehensweisen zur Modellierung von zweiflutigen Turbinen vorgestellt. Das Turbinenverhalten von zweiflutigen Turbinen wird zum Teil lediglich über die Kennfelder bei Gleichbeaufschlagung beschrieben, wobei eine auf Motormessungen basierende Kalibrierung dabei zwingend notwendig ist.…”

Design of a Pulsing Flow Driven Turbine

“…They found that turbine efficiency decreased with pulsing flow and that the decrease in efficiency was related to the amplitude of the pressure pulse. The decrease in turbine efficiency has also been demonstrated computationally [11], but most of the computational analysis of pulsing flow through a turbine has focused on radial and mixed flow turbocharger applications [12][13][14][15].…”

Investigation on the flow characteristics of a VNT turbine under pulsating flow conditions

“…They found that the change of the turbine efficiency is contrary to the change of turbine inlet pressure. Palfreyman and Martinez-Botas 25 and Costall et al 26 studied the performance of turbocharger turbines under pulsating conditions. Their results showed that there is a significant deviation between the quasi-steady and actual performance of turbines.…”