Twin-Scroll turbocharger turbine stage evaluation of experimental data and simulations

• In this study a novel comparison of CFD, measured data and a ID-model is presented for a Twin-scroll turbocharger turbine stage. Both full and single admission flow divisions were taken into consideration and shown to represent "on-engine" conditions in the high and low engine rpm range respectively for a heavy-duty 6-cylinder diesel engine. With this in mind, the turbine stage was evaluated for each flow division at several rotational speeds. Both high and low pressure ratios were run. Emphasis is made on high pressure ratios as it is the most relevant case with regards to the energy levels of the exhaust flow. The purpose of the study was to gain insight into the differences and similarities between gas stand measurements, a ID-model and CFD considering performance and turbine stage parameters. The study concludes that the results from the measurements in the gas stand and ID-model, obtained best correlation with the CFD results at low turbine pressure ratios. At high pressure ratios significant deviations were observed. In order to check for discrepancies, both frozen rotor and stage interfaces were considered in the CFD-model, with an additional variant taking the rotor-volute tongue clocking into account. All interfaces resulted in the same trends, although the frozen rotor approach provided the best correlation with measured data. The clocking effect was seen not to affect the results to a great extent in this case. The main difference between the CFD and measurements in combination with the ID model-prediction primarily occur at the rotor inlet. The pressures were predicted to be substantially higher by the CFD calculations due to reduced pressure losses in the volute. Especially taking effect at high turbine pressure ratios which is most relevant for turbocharger applications and therefor the mapping process in the gas stand. This can be one of the reasons for significant deviations in efficiency, turbine parameters etc. at high pressure ratios as effectively more energy will be available to the rotor for a given turbine stage pressure ratio. In general best coherence was achieved for the full admission case. Even so, trends of main parameters such as efficiency, flow capacity and turbine parameters point in the same direction comparing CFD with calculations and measured results for both full and single admission.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

Machine Design

Maskinkonstruktion

Publikations- och innehållstyp

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