The Impact of Volute Aspect Ratio on the Performance of a Mixed Flow Turbine

Abstract

Current trends in the automotive industry towards engine downsizing mean turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, mixed flow turbines can offer non-zero blade angles, reducing leading edge (LE) separation at low velocity ratios. The current paper investigates the performance of a mixed flow turbine with three different volute aspect ratio (AR) designs (AR = 0.5, 1 and 2). With constant A/r (ratio of volute area to centroid radius), the AR = 0.5 volute design produced a 4.3% increase in cycle averaged mass flow parameter (MFP) compared to the AR = 2 design. For the purpose of performance comparison, it was necessary to manipulate the volute A/r's to ensure constant MFP for aerodynamic similarity. With the volute A/r's manipulated to ensure constant MFP for aerodynamic similarity, the maximum variation of cycle averaged normalized efficiency measured between the designs was 1.47%. Purely in the rotor region, the variation in normalized cycle averaged efficiency was 1%. The smallest tested volute aspect ratio showed a significant increase in volute loss while the ARs of 1 and 2 showed similar levels of loss. The smallest AR volute showed significant secondary flow development in the volute. The resulting variation in LE incidence was found to vary as a result.

The impact of volute aspect ratio and tilt on the performance of a mixed flow turbine

“…While both aspects have been investigated individually no previously published work has investigated the two aspects combined. In particular this work builds on previously published work by the current authors on volute aspect ratio 14 and volute tilt. 9 The investigation focuses on the development of volute secondary flow structures and the resulting rotor inlet conditions, highlighting the importance of correct volute-rotor matching, particularly in mixed flow applications where span-wise LE manipulation is possible through camber and flow cone angle changes.…”

Analysis of leading edge flow characteristics in a mixed flow turbine under pulsating flows

“…A full domain specific mesh study was completed, similar to that recommended by Galindo et al., 12 and was extended to include a boundary mesh independence study, further details of the mesh study conducted are available in the literature. 13 The volute and outlet region domains used an unstructured tetrahedral mesh developed in ICEM CFD. The rotor region used a structured hexahedral mesh completed in ANSYS TurboGrid.…”

Electric Boosting and Energy Recovery Systems for Engine Downsizing

“…This enables the mixed flow turbines to accomplish higher mass-induced mass flow rate and optimum efficiency at lower velocity ratios, compared to equivalent radial ones. [34], radial inflow turbine [35] and axial flow turbine [36].…”

“…Their results showed a 14% improvement of the pivoted VGT compared to conventional VGT. [34], radial inflow turbine [35] and axial flow turbine [36].…”