Steady State Experimental Characterization of a Twin Entry Turbine under Different Admission Conditions
Vittorio Usai, Silvia Marelli
Abstract
The increasingly restrictive limits on exhaust emissions of automotive internal combustion engines imposed in recent years are pushing OEMs to seek new solutions to improve powertrain efficiency. Despite the increase in electric and hybrid powertrains, the turbocharging technique is still one of the most adopted solution in automotive internal combustion engines to achieve good efficiency with high specific power levels. Nowadays, turbocharged downsized engines are the most common solution to lower CO2 emissions. Pulse turbocharging is the most common boosting layout in automotive applications as the best response in terms of time-to-boost and exhaust energy extraction. In a high-fractionated engine with four or more cylinders, a twin entry turbine can be adopted to maximize pulse turbocharging benefits and avoid interaction in the discharge phase of the cylinders. The disadvantages of the twin entry turbine are mainly due to the complexity of the exhaust piping line and the high amount of information required to build a rigorous and reliable matching model. This paper presents a detailed experimental characterization of a twin entry turbine with particular reference to the turbine efficiency and the swallowing capacity under different admission conditions. The steady flow experimental campaign was performed at the turbocharger test bench of the University of Genoa, in order to analyze the behavior of the twin entry turbine in full, partial and unbalanced admission. These are the conditions in which the turbine must work instantaneously during its normal operation in engine application. The results show a different swallowing capacity of each sector and the interactions between the two entries.