Comparison of Secondary Flow Characteristics in Mixed-Flow Turbine between Nozzleless and Symmetric Nozzle Vane Angles under Steady-State Flow at Full Admission

Mohd Jazmi Asyraff Jama’a, Balamurugan Annamalai Gurunathan (), Ricardo Martinez Botas and Uswah Khairuddin
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Mohd Jazmi Asyraff Jama’a: Department of Mechanical Engineering, Faculty of Engineering, National Defense University of Malaysia, Kuala Lumpur 57000, Malaysia
Balamurugan Annamalai Gurunathan: Department of Mechanical Engineering, Faculty of Engineering, National Defense University of Malaysia, Kuala Lumpur 57000, Malaysia
Ricardo Martinez Botas: Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London SW7 2BX, UK
Uswah Khairuddin: Department of Mechanical Precision Engineering, Malaysia-Japan International Institute of Technology, University of Technology Malaysia, Kuala Lumpur 54100, Malaysia

Energies, 2023, vol. 16, issue 10, 1-29

Abstract: In industrial applications, radial or mixed-flow turbines are frequently used in energy recovery systems, small turbines for producing power, and turbochargers. The implementation of radial or mixed-flow turbines helps to maintain high efficiency at a large range of pressure ratios by reducing the overall turbine losses and secondary flow losses. Numerous findings on secondary flow development research adopting double-entry turbines can be obtained in the public domain, except asymmetric volute, which is less well-researched. The focus of the present work is to investigate the evolution of secondary flows and their losses in a mixed-flow turbine used in an asymmetric volute turbine, by employing an experimentally validated three-dimensional computational fluid dynamics (CFD). The flow topology is analyzed to explain the formation and evolution of flow separations at the pressure, suction, and hub surfaces. As the opening angle of the nozzle vane increases, the incidence angle falls into the positive range while the maximum pressure difference between the shroud and hub decreases by about 40%. The results also show that the development of secondary flow accounts for the majority of losses and induced the centrifugal pressure head influence. The presence of symmetric nozzle vanes in both large and small scrolls is also found to have a significant detrimental effect on the turbine efficiency, which is 4% lower than the nozzleless case. Furthermore, significant flow separation is observed in the symmetrical nozzle vane configuration as opposed to that of nozzleless. In addition, the centrifugal pressure head indicated by the maximum pressure difference between the hub and shroud influences the overall turbine efficiency, as the symmetrical nozzle vane arrangement is introduced with two different turbine rotational speeds of 30 K rpm and 48 K rpm.

Keywords: turbocharger volute; asymmetric volute; double-entry volute; symmetric nozzle vanes; secondary flow; losses; centrifugal pressure head (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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