[home] [Personal Program] [Help]

---

Session: Parallel Session: Systems Design, Optimization and Applications III
Session starts: Friday 23 September, 11:20
Presentation starts: 11:20
Room: Senaatszaal

---

Andrea Spinelli (Politecnico di Milano - Dipartimento di Energia)
Matteo Pini (Politecnico di Milano - Dipartimento di Energia)
Vincenzo Dossena (Politecnico di Milano - Dipartimento di Energia)
Paolo Gaetani (Politecnico di Milano - Dipartimento di Energia)
Francesco Casella (Politecnico di Milano - Dipartimento di Elettronica e Informazione)

Abstract:
A blow-down wind tunnel for real-gas applications has been designed, validated by means of dynamic simulation and finally constructed. The facility is aimed at characterizing an organic vapour stream, representative of expansions taking place in Organic Rankine Cycles (ORC) turbines, by independent measurements of pressure, temperature and velocity. ORC turbine performances are expected to strongly benefit from characterization of such flows and validation of design tools using experimental data, which still lack in scientific literature. The flow field investigation within industrial ORC turbine passages has been considered strongly limited by the unavailability of calibration tunnels for real-gas operating probes, by poor plant availabilities and by restricted accesses for instrumentation. As a consequence, the opportunity of building a test rig has been exploited and a dedicated facility has been implemented. The paper thoroughly discusses the design and the dynamic simulation of the apparatus, presents its final layout and shows the facility “as built”. A straight-axis planar convergent-divergent nozzle represents the test section for early tests, but the test rig can also accommodate linear blade cascades. The facility implements a blow down operating scheme, due to high fluid densities and temperatures of operation, which result in an unaffordable thermal power to be provided in case of continuous operation. A wide variety of working fluids can be tested with adjustable operating conditions up to maximum temperature and pressure of 400 °C and 50 bar respectively. Despite the fact that the test rig’s operational mode is unsteady, the inlet nozzle pressure can be kept constant by a control valve. In order to estimate the duration of both set-up and experiments and to describe the time evolution of the main cycle processes (namely the fluid heating/evaporation, the vapour expansion and the vapour condensation) the dynamic plant operation, including the control system, has been simulated. Design and simulation have been performed with either a lumped parameter or a 1D approach using siloxane MDM and hydrofluorocarbon R245fa as the reference compounds and by adopting state-of-the-art thermodynamic models of the selected fluids. The above calculations shown how experiments may last from 12 seconds to several minutes (depending on the fluid and test pressure) while their set-up requires a few hours. These durations have been considered consistent with those required to perform the desired experiments. Moreover, the economic constraints have been met by the technical solution adopted for the plant, allowing the construction of the facility.