The matching of a radial inflow turbine with a piston engine, while ensuring torque backup across ranges of engine speeds and loads, is a complex task due to the nature of exhaust gas flows. This paper investigates the effects of pulsating exhaust gas flows on a single-entry radial turbine when coupled with a spark-ignition piston engine. The transient behaviour is analyzed using a combination of computational fluid dynamics (CFD) and an analytical model under both steady and unsteady conditions. This study also examines how the pulsating gas flows affect the turbine performance and the transient response when paired with an internal combustion engine (ICE) under various operating conditions. When matched with an ICE, the unsteady performance of a turbocharger differs significantly from the steady-state one due to highly pulsating gas flows at the inlet of the turbine. This behaviour is characterized by a hysteresis loop in the turbine’s performance, which stems from the filling and emptying of gases within the volute. This work essentially demonstrates that the unsteadiness from the turbine-side propagates through the whole turbocharging system, inducing a shift in the compressor’s operating line. For the case of single-cylinder engine, the operating points are moved towards the surge limit at low engine speeds—with observed deviations of up to 4% in the pressure ratio and 4.9% in the swallowing capacity—a critical surge risk that the conventional steady-state matching approaches fail to predict. The contribution of this work lies in integrating a system-level analysis, which uniquely quantifies the substantial impacts of the radial turbine’s unsteady behaviour on the matching with a spark-ignition engine and the operational stability of the entire turbocharging system.
Cerdoun et al. (Wed,) studied this question.