A Study of Trailing-Edge Losses in Organic Rankine Cycle Turbines

Abstract

In this paper, vane trailing-edge losses which occur in organic rankine cycle (ORC) turbines are investigated. Experiments are performed to study the influence of dense gas effects on trailing-edge loss in supersonic flows using a novel Ludwieg tube facility for the study of dense-gas flows. The data is also used to validate a computational fluid dynamics (CFD) flow solver. The computational simulations are then used to determine the contributions to loss from shocks and viscous effects which occur at the vane trailing edge. The results show that dense gas effects play a vital role in the structure of the trailing-edge flow, and control the extent of shock and viscous losses.

Working-Fluid Replacement in Supersonic Organic Rankine Cycle Turbines

“…A major challenge facing numerical studies on ORC turbines is that of obtaining experimental data for validation of design models and CFD solvers. Currently, there are a few commissioned test facilities that aim to address this challenge [25][26][27][28]. Already there have been interesting results concerning trailing-edge losses in ORC turbines [27], and experimental observations of the expansion of MDM within a converging-diverging nozzle [29].…”

“…Currently, there are a few commissioned test facilities that aim to address this challenge [25][26][27][28]. Already there have been interesting results concerning trailing-edge losses in ORC turbines [27], and experimental observations of the expansion of MDM within a converging-diverging nozzle [29]. These results, along with further developments in the other test facilities, will remain critical for the future validation of numerical models.…”

Development and application of simulation tools for supercritical carbon dioxide radial inflow turbine

“…Hence for perfect gases acoustic speed increases with density and pressure along an isentrope [183]. For air, steam, or CO 2 , the value of the fundamental derivative is greater than 1, meaning that the acoustic speed, a, increases in a compression and decreases through an expansion [185]. However for organic fluids with high molecular complexity, the fundamental derivative, Γ, close to the critical point can drop below 1 or 0 [186].…”

“…And for Γ < 1 the acoustic speed decreases with pressure. The effect of fundamental derivative, Γ, on the Prandtl-Meyer function is discussed by Thompson [125] and Galiana et al [185]. They shows that for certain conditions with Γ < 1, acoustic speed increases through an expansion, leading to the possibility of rarefaction shocks.…”

“…This phenomena has attracted attention from researchers working on ORC design. Some dense gases, considered as ideal working fluid for ORCs, such as R245f a, MD n M, exhibit this non-classical region [185,187]. Thus it is important for a non ideal gas CFD solver with potential for turbomachinery applications to accurately simulate the fluid dynamics when fluid properties are in this particular region.…”