Three-dimensional unsteady stator-rotor interactions in high-expansion organic Rankine cycle turbines

Three-dimensional unsteady stator-rotor interactions in high-expansion organic Rankine cycle turbines

Otero Rodriguez, G.J. (TU Delft Energy Technology)
Smit, S.H.H.J. (TU Delft Energy Technology)
Pecnik, Rene (TU Delft Energy Technology)

2021

Organic Rankine cycle (ORC) systems are a readily available technology to convert thermal energy from renewable- and waste heat sources into electricity. However, their thermal performance is relatively low due to the low temperature of the available heat sources, but more importantly, due to the low efficiency of the employed expander. Designing the turboexpander is exceptionally challenging, because the flow field is highly supersonic and unsteady, and since the expansion takes place in the highly non-ideal dense-vapor region. In this work, we perform unprecedented three-dimensional unsteady simulations of several high-expansion cantilever ORC turbines to highlight distinctive loss mechanisms. The simulations indicate strong unsteady effects in the rotor blade passage, as a result of unsteady propagating shock waves interacting with viscous wakes and boundary layers. Moreover, the flow field in the rotor blade passage is strongly affected by three-dimensional secondary flow features and a sharp expansion in the shroud region at the inlet of the rotor blade. These span-wise mechanisms and unsteady flow interactions introduce irreversible losses which must be taken into account for designing highly efficient ORC expanders.

High-expansion radial inflow turbines
ORC power systems
stator-rotor unsteady interaction
Three-dimensional simulations

http://resolver.tudelft.nl/uuid:26dfa0a8-4b5e-48de-91ec-d1cbc42d4a05

https://doi.org/10.1016/j.energy.2020.119339

0360-5442

Energy, 217

Institutional Repository

journal article

© 2021 G.J. Otero Rodriguez, S.H.H.J. Smit, Rene Pecnik