Numerical simulation of air flow through turbocharger compressors with dual volute design Kui Jiao a , Harold Sun b , Xianguo Li a, * , Hao Wu a , Eric Krivitzky c , Tim Schram b , Louis M. Larosiliere c a Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 b Ford Motor Company, Dearborn, MI 48126, USA c Concepts NREC, White River Junction, VT 05001, USA article info Article history: Received 27 November 2008 Received in revised form 24 January 2009 Accepted 28 February 2009 Available online 29 March 2009 Keywords: Turbocharger centrifugal compressor CFD Dual volute Dual diffuser Stable operating range abstract In this paper, turbocharger centrifugal compressors with dual volute design were investigated by using Computational Fluid Dynamics (CFD) method. The numerical simulation focused on the air flow from compressor impeller inlet to volute exit, and the overall performance level and range are predicted. The numerical investigation revealed that the dual volute design could separate the compressor into two operating regions: ‘‘high efficiency” and ‘‘low efficiency” regions with different air flow characteris- tics, and treating these two regions separately with dual diffuser design showed extended stable operat- ing range and improved efficiency by comparing with conventional single volute design. The ‘‘dual sequential volute” concept also showed the potential to further extend the stable operating range by clos- ing one of the volutes at low air flow rates. Furthermore, by comparing with other alternate designs such as variable diffuser vanes and variable inlet guide vanes, the operation of the dual sequential volute also features relatively simple control and calibration. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Turbocharger compressors have been widely accepted as effec- tive devices to improve the performance and reduce the emissions of diesel engines. The increasingly stringent emission regulations, engine downsizing and heavy exhaust gas recirculation (EGR) are likely to push the engine operating conditions toward less efficient or even unstable regions of a conventional turbocharger compres- sor which is constrained by surge and choke. Low speed and high load working conditions of diesel engines require the turbocharger compressors to supply highly boosted air at low flow rates, how- ever, the performance of turbocharger compressors is usually lim- ited under such operating conditions, which is recognized as surge. On the other hand, choke is the constraint of turbocharger com- pressors at high air flow rates. Therefore, improving turbocharger efficiency and extending the stable operating range are becoming critical for viable future low emission diesel engines. Different technologies have been developed for such purposes, such as var- iable inlet guide vanes, casing treatment, variable diffuser vanes, adjustable vaneless diffusers, and so on. Moltar et al. [1] conducted an experimental study to investigate the effects of variable inlet guide vanes on the performance of a centrifugal compressor, and the advantages of variable inlet guide vanes in extending the turbocharger operating range were con- firmed. Helmut et al. [2] designed an inlet swirl-generator device, and both the Computational Fluid Dynamics (CFD) simulations and experimental measurements showed improved turbocharger performance. Both [1,2] focused on improving the air flow quality at compressor inlet, and similar studies were also found in [3,4]. Recirculation around inlet of compressor impeller (also called cas- ing treatment) is also an effective way to widen the operating range. Hunziker et al. [5] conducted numerical and experimental investigations of a centrifugal compressor with an inducer casing bleed system, and they demonstrated that optimized air flow at compressor impeller could improve the compressor map width without a loss in efficiency. CFD simulations carried out by Iwakiri and Uchida [6] showed that a combination of both the casing treat- ment and variable inlet guide vanes could provide wider operating range by comparing than that using each independently. Compressor surge or choke may also occur at diffuser area. Improving the air flow at the downstream of impeller is also an effective way to extend the operating range, which is usually achieved by the design optimization of the diffuser. Both the vane- less and vaned diffusers are widely used for turbocharger compres- sors, and generally vaneless diffuser has wider operating range but lower pressure recovery and efficiency by comparing with vaned diffuser. Engeda [7] conducted numerical and experimental studies 0306-2619/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2009.02.019 * Corresponding author. Tel.: +1 519 888 4567x36843; fax: +1 519 885 5862. E-mail addresses: kjiao@uwaterloo.ca (K. Jiao), hsun3@ford.com (H. Sun), x6li@uwaterloo.ca (X. Li), h25wu@uwaterloo.ca (H. Wu), emk@conceptsnrec.com (E. Krivitzky), tschram@ford.com (T. Schram), lml@conceptsnrec.com (L.M. Larosi- liere). Applied Energy 86 (2009) 2494–2506 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy