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ERC

NSHOCK Report Summary

Project ID: 617603
Funded under: FP7-IDEAS-ERC
Country: Italy

Periodic Report Summary 2 - NSHOCK (Non classical rarefaction shock-waves in molecularly complex vapours)

The ERC Consolidator Grant NSHOCK project regards the non-ideal compressible-fluid flows of molecularly complex fluids, with particular regards to the behavior of binary mixtures of silicone fluids. The research is focused on the identification and study of shock waves in the non-ideal regime, including so-called negative or rarefaction shock waves. Applications of this knowledge range from chemical and pharmaceutical processes using carbon dioxide in the super-critical state to Organic Ranking Cycle machinery for power generation from low-temperature, renewable energy sources, from high-enthalpy wind tunnel to the study of the fluid dynamics of the atmosphere of Venus.
The scientific achievement so far regards the further advance of the theory of nozzle flows in the non-ideal and non-classical regime and the discovery of a new type of shock wave, which we christened non-ideal oblique shock wave. Differently from ideal flows, the Mach number can increase across a non-ideal oblique shock. Non-ideal oblique shock waves are expected to occur at the trailing edge of turbine blades operating in the non-ideal compressible-fluid regimes and with molecularly complex fluids, such those employed in Organic Rankine Cycle. Regarding the experimental activities, the first-ever observation of expanding supersonic flows in the non-ideal regime was performed during the first half of the project. Experimental results include total pressure and temperature measurements, static pressure measurements along the nozzle axis and flow visualization using schlieren techniques. These results are currently the only ones available to validate theoretical and numerical models of non-ideal compressible-fluid flows. The research team participated to the development of the open-source flow simulation solver SU2 into an open platform for simulating non-ideal compressible-fluid flows in three-dimensional complex geometries, including turbines of axial and centrifugal type. Current activities are devoted to the implementation of a novel sliding mesh approach for unsteady simulation of multi-stage turbomachinery. The study of the thermodynamic properties and of the thermal stability of the working fluids, which is of paramount importance for cycle optimisation and turbine design, focused initially on the pure fluids and it is now devoted to binary mixtures of siloxane fluids.
Unique experimental facilities and technologies are used to achieve the project goals. The TROVA facility completed during the present project is currently the only available test-rig in which non-ideal compressible-fluid flows of molecularly complex fluids can be generated, observed and measure. An innovative test-rig is currently being built to investigate thermal stability of mixtures of molecularly complex fluids at high temperature. The test-rig will allow to sample both the liquid and the vapour phase of the fluid (pure or mixture) being tested. This is required to work with mixtures where the composition of the liquid and vapour phase can possibly differ. A novel simulation tool, called VirtuaSchlieren, was developed and implemented in both CPU and GPU architectures to predict the images obtained from schlieren visualisations during the experiment. A fast, scalable kd-tree algorithm as developed to reduce the computational time. A non-ideal dependence of the refraction index on the density was also implemented to deal with non-ideal flow conditions.
Diverse action are being taken to disseminate the achievement of the project towards the general public and specialists in academia and industry. The time line of the project development is available at the website crealab.polimi.it. The results of the research have been published in high-level scientific journals and presented at international conferences with delegates from both the academic and the industrial worlds. In particular, care was taken to present the developments at conferences devoted to experts in specific disciplines, such as e.g. computational fluid dynamics and experimental fluid mechanics, and at technology- or application-oriented conferences. The latter are e.g. the ASME Turbo Expo and the ORC Power system conferences.
The 1st Iinternanional Seminar on Non-Ideal Compressible-Fluid Dynamics for Propulsion and Power (NICFD 2016, nicfd2016.polimi.it) was organized by the research team in Varenna on the 20th and the 21st of October 2016, in collaboration with the Technical Univeristy of Delft and the University of Cambridge. During the seminar, an international community of from academia and industry discussed the implications of fluid non-ideality on both our current understanding of the flow physics and the technical applications. All publications submitted to the conference will be published in open-access journals.

Contact

Alberto Guardone, (Professor)
Tel.: +39 02 2399 8393
Fax: +39 02 2399 8334
E-mail
Record Number: 199458 / Last updated on: 2017-06-21
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