There is an ever-growing demand for automotive turbocharger compressors to deliver a high boost-pressure efficiently over a wide range of engine operating conditions. At low turbocharger speeds, the engine operating line is close to the surge limit of the compressor wherein upstream blockage, for example, could result in system surge. Therefore, sufficient surge margin is required to ensure stable operation. Currently, the most effective method in operating range extension is through the use of a ported shroud (or bleed slot) casing treatment. However, extension typically comes at the cost of stage efficiency due to the mixing of high and low momentum flow at the inducer inlet. In recent years, active systems such as the on/off vaned diffuser and the swing vane type variable geometry vaned diffuser have gained more attention in the automotive sector due to their potential in improving both performance and range with minimum efficiency penalty. As part of a study of an on/off vaned diffuser concept, a vaned diffuser was designed for a small automotive turbocharger centrifugal compressor with a vaneless diffuser at the engine low-end torque point. Single-passage CFD simulations with the impeller back-disk cavity included showed a not insignificant drop in stage performance when compared to those without the cavity, which in turn motivated this numerical investigation. This CFD study aims to identify the key aerodynamic mechanisms responsible for reduced stage performance when the back-disk cavity is included at widely varying operating conditions. The results showed that for overall stage performance predictions, it was not essential to include the back-disk cavity, however for detailed aerodynamic investigations, particularly with vaned diffuser included, it was worth careful consideration.
|Number of pages||11|
|Publication status||Published - 17 Oct 2018|
|Event||International Turbocharging Seminar 2018 - Shanghai, China|
Duration: 16 Oct 2018 → 17 Oct 2018
|Seminar||International Turbocharging Seminar 2018|
|Period||16/10/2018 → 17/10/2018|