Performance improvement of a radial organic Rankine cycle turbine by means of automated computational fluid dynamic design

Abstract

There is a growing interest in organic Rankine cycle turbogenerators because of their ability to efficiently utilize external heat sources at low-to-medium temperature in the small-to-medium power range. High-temperature organic Rankine cycle turbines typically operate at very high pressure ratio and expand the organic working fluid in the dense-vapour thermodynamic region, thus requiring computational fluid dynamics solvers coupled with accurate thermodynamic models for their performance assessment and design. In this article we present a steady-state three-dimensional viscous computational fluid dynamics study of the Tri-O-Gen organic Rankine cycle radial turbine, including the radial nozzle, the rotor and the diffuser. The turbine operates with toluene as the working fluid, whose accurate thermophysical properties are obtained with a look-up table approach. Based on the three-dimensional simulation results, together with a two-dimensional fluid dynamic optimisation procedure documented elsewhere, an improved nozzle geometry is designed, manufactured and experimentally tested. Measurements show it delivers 5 kWe or 4% more net power output, as well as improved off-design performance.

Organic Rankine Cycle Power Systems: From the Concept to Current Technology, Applications, and an Outlook to the Future

“…The fluid dynamics of expanders attracts considerable research efforts [158][159][160]: a sizable improvement of the fluid-dynamic performance of the expander directly affects the power output and thus the return on investment, more often without affecting the cost of each unit. On the contrary, improvement of the heat exchanging equipment can often be obtained only by increasing the heat transfer surface, therefore the cost of each unit.…”

Optimization of blade profiles of axial turbine working with MDM

“…Należy jednak zwrócić uwagę na fakt, że wciąż są one dużym wyzwaniem, szczególnie dla wielkocząsteczkowych gazów ze względu na równania stanu, nieklasyczne zachowania z punktu widzenia dynamiki gazów [6] oraz trudności z rozwiązaniem warstwy przyściennej (ze względu na duże gęstości trudno jest uzyskać maksymalne wartości parametru y + w granicach 1). Pomimo tych trudności wiele uzyskanych wyników obliczeń CFD dla tych substancji znajduje potwierdzenie w badaniach eksperymentalnych [7,8]. Nawet dobrze zaprojektowana maszyna może być poprawiona.…”

An innovative small-scale two-stage axial turbine for low-temperature organic Rankine cycle

“…In terms of 3D CFD of RIT, Harinck et al [13] performed a 3D CFD study on a Tri-O-Gen radial turbine for the ORC system operated by toluene. The 2D optimization was performed for a nozzle which was manufactured and tested with 5 kWe power output.…”