Accuracy Assessment of the SU2 Flow Solver for Non-Ideal Organic Vapor Supersonic Expansions using Experimental Data

Non-ideal compressible fluid dynamics is a novel research field which studies the behavior of dense, supercritical or two-phase fluid flows. Complex models are now being developed to describe the thermodynamic behavior of these fluids in various regimes, often based on empirical results. In the present work, experimental data is used to assess the predictive capabilities of the SU2 flow solver coupled with the Peng-Robinson equation of state together with variable specific heats for the hexamethyldisiloxane in its non-ideal vapor state. The experimental campaign is carried out in the Organic Rankine Cycle Hybrid Integrated Device facility, also called ORCHID, in Delft (NL). The ORCHID nozzle test section is equipped with a Z-type Schlieren measurement chain capable of acquiring images of the supersonic expansion of the organic vapor in various regions of non ideality. The Schlieren images are post processed following a new developed method and Schlieren data extraction tools. The method allows the extraction of Mach lines and shocks from raw Schlieren images from which the Mach field is calculated. The developed tools are divided into two main applications: the first one is the characterization of the Mach field in a nozzle, and the second one is the detection of Shocks. In the following, the Mach line detection tools is tested to understand the capabilities of the Mach line and Shock extraction tools, and then used to characterize the supersonic expansion of the organic vapor through calculation of the Mach field and evaluation of all the possible uncertainties in the method. Once all the uncertainties in the boundary conditions, Schlieren measurement chain, nozzle test section and post processing tools have been quantified, the experimental results of the vapor expansion are compared to the CFD prediction of SU2, thus taking a first step towards the validation of the SU2 software for NICFD applications.