0
Research Papers: Gas Turbines: Turbomachinery

Aerodynamics of Centrifugal Turbine Cascades

[+] Author and Article Information
Giacomo Persico

Associate Professor
Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
via Lambruschini 4,
Milano 20156, Italy
e-mail: giacomo.persico@polimi.it

Matteo Pini

Assistant Professor
Propulsion and Power,
Aerospace Engineering Faculty,
Delft University of Technology,
Delft 2629 HS, The Netherlands
e-mail: M.Pini@tudelft.nl

Vincenzo Dossena

Associate Professor
Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
via Lambruschini 4,
Milano 20156, Italy
e-mail: vincenzo.dossena@polimi.it

Paolo Gaetani

Associate Professor
Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
via Lambruschini 4,
Milano 20156, Italy
e-mail: paolo.gaetani@polimi.it

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 22, 2014; final manuscript received February 15, 2015; published online May 12, 2015. Assoc. Editor: Piero Colonna.

J. Eng. Gas Turbines Power 137(11), 112602 (Nov 01, 2015) (11 pages) Paper No: GTP-14-1427; doi: 10.1115/1.4030261 History: Received July 22, 2014; Revised February 15, 2015; Online May 12, 2015

The centrifugal turbine architecture is a promising solution for small-to-medium organic Rankine cycle (ORC) power systems. The inherent compactness of the multistage arrangement makes this configuration very attractive for dealing with the high volumetric flow ratios typical of ORC turbines. In absence of experimental evidence, a thorough assessment of the technology can be uniquely based on sufficiently accurate computational fluid dynamic (CFD) simulations. In the present work, the aerodynamic performance of a fixed and a rotating cascade of centrifugal turbine are investigated by applying a three-dimensional CFD model. Precisely, the study is focused on the sixth stage of the transonic centrifugal turbine proposed in Pini et al. (2013, “Preliminary Design of a Centrifugal Turbine for ORC Applications,” ASME J. Eng. Gas Turbines Power, 135(4), p. 042312). After recalling the blade design methodology, the blade-to-blade and secondary flow patterns are carefully studied for both stator and rotor. Results show that the centrifugal configuration exhibits distinctive features if compared to axial turbine layouts. The diverging shape of the bladed channel and the centrifugal force alter significantly the pressure distribution on the profile. Moreover, the Coriolis force induces a slip effect that should be properly included in the preliminary design phase. Provided that the flaring angle is limited, the almost uniform spanwise blade loading greatly augments the three-dimensional performance of the cascades compared to axial rows. In the rotor, the low inlet endwall vorticity and the Coriolis force further weaken the secondary flows, resulting in even lower secondary losses with respect to those predicted by loss models developed for axial turbines. Ultimately, the efficiency of the stage is found to be two points higher than that estimated at preliminary design level, demonstrating the high potential of the centrifugal turbine for ORC applications.

FIGURES IN THIS ARTICLE
<>
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Distribution of absolute and relative Mach number in the last stage of the centrifugal turbine

Grahic Jump Location
Fig. 2

Blade-to-blade flow in the centrifugal turbine stator

Grahic Jump Location
Fig. 3

Entropy field downstream of the stator

Grahic Jump Location
Fig. 4

Secondary vortices and vorticity downstream of the stator

Grahic Jump Location
Fig. 5

Relative total pressure and Mach number distributions on the rotor blade row at midspan—ROT CASE

Grahic Jump Location
Fig. 6

Relative Mach number distributions on the rotor blade row removing inertial effects. Left frame: FIX-LE case; right frame: FIX-TE case.

Grahic Jump Location
Fig. 7

Isentropic relative Mach number distributions for the inertial and noninertial models

Grahic Jump Location
Fig. 12

Secondary vortices and vorticity downstream of the rotor computed in fixed reference frame—high inlet endwall vorticity

Grahic Jump Location
Fig. 8

Entropy field downstream of the rotor with rotation effects

Grahic Jump Location
Fig. 9

Secondary vortices and vorticity downstream of the rotor with rotation effects

Grahic Jump Location
Fig. 10

Spanwise profiles of inlet total pressure at the stator (absolute) and rotor (relative) calculations

Grahic Jump Location
Fig. 11

Secondary vortices and vorticity downstream of the rotor computed in fixed reference frame—real inlet endwall vorticity

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In