An Experimental Method to Test Twin and Double Entry Automotive Turbines in Realistic Engine Pulse Conditions

In a context of increasing emission regulations, turbocharged gasoline engines are increasingly present in the automotive industry. In particular, the twin-entry and double-entry radial inflow turbines are widespread used technologies to avoid interferences between exhaust process of consecutive firing order cylinders. In this study, a passenger car twin-entry type turbine has been tested under highly pulsating flow conditions by means of a specifically built gas stand, trying to perform pulses with similar features as the ones that can be found in a real reciprocating engine. For this purpose, the turbine has been instrumented with multiple pressure, temperature and mass flow sensors, using a uniquely designed rotating valve for generating the pulses. The test bench setup is flexible enough to perform pulses in both inlet branches separately as well as to use hot or ambient conditions with minimal changes in the installation. Using instantaneous pressure sensors and a beamforming technique, the pressure at the turbine inlets and outlet has been split into forward and backward travelling waves providing a complete realistic acoustic characterization in terms of reflection and transmission waves for both time and frequency domains. By adding the novelty of an experimental test in realistic flow conditions, this study provides a detailed testing methodology and contributes to a better understanding of the performance of two-scroll turbines in real driving conditions. Thus, the new data obtained could facilitate the modelling work in the air management loop, providing a better prediction of turbine outlet conditions and enabling a more optimized solutions during the engine design stage, especially in terms of optimization of scavenging effects and silencer and aftertreatment design during turbocharger selection.