Steady State Experimental Characterization of a Twin Entry Turbine under Different Admission Conditions

Vittorio Usai,Silvia Marelli

doi:10.3390/en14082228

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.

Highlights

The two entries could be fed separately due to their design and, when connected to different cylinders taking into account the firing order, the exhaust process is optimized to avoid backflow
The turbine performance obtained by the experimental campaign is analyzed, with special reference to the characteristic curves of the swallowing capacity and to the thermomechanical efficiency
It is possible to see the typical trend of turbine maps with a monotone correcorrelation between the Mass

Summary

Introduction

CO2 reduction is the main goal in the modern automotive engine. Environmental Protection Agency (EPA) for passenger cars have prompted the automotive industry to develop technological solutions to improve the global efficiency of the propulsion system to limit fuel consumption and pollutant emissions, without compromising vehicle performance and drivability [1]. The Internal Combustion Engine (ICE) can, play an important role in a medium-term scenario thanks to the progressive electrification of the powertrain through Hybrid Vehicles [3] and the development of integrated technologies. Turbocharging (TC) is one of the most commonly used ways to achieve these goals, allowing downsizing without compromising engine power. The adoption of multi-entry coupled with a properly designed exhaust piping arrangement allows for a significant improvement in transient response. The two entries could be fed separately due to their design and, when connected to different cylinders taking into account the firing order, the exhaust process is optimized to avoid backflow

Methods

Results

Conclusion