Experimental characterization of an axisymmetric supersonic air ejector

Details

Supervisors

Bartosiewicz, Yann ; Winckelmans, Grégoire

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

Supersonic ejectors are passive components in thermodynamic cycles, functioning as compressors that utilize two streams of fluid. The primary stream, characterized by high stagnation pressure, entrains the secondary stream, which has a lower stagnation pressure. The two streams mix in a constant-area duct, where momentum and energy are exchanged. The mixed flow is then expanded through a diverging section and reaches an intermediate pressure that matches the downstream conditions. Thanks to their ability to operate on low-grade energy, such as waste heat, solar energy, and renewable energies in general, supersonic ejectors have attracted more and more attention at a time when finding solutions to climate change has become a priority. Additionally, since ejectors are passive devices, their maintenance requirements and overall costs are relatively low. Studies on supersonic ejectors have been conducted for decades, beginning with 1-D models and recently advancing to 2-D and 3-D analyses using Computational Fluid Dynamics (CFD) simulations. The need to study ejectors is driven by their relatively low performance in refrigeration cycles, as measured by the Coefficient of Performance (COP). Although their use of low-grade energy sources is appealing, they still cannot compete with traditional compressors in terms of efficiency. The purpose of this Master's thesis is then clearly drawn: better understand the behavior of supersonic ejectors, and in particular, how do the experimental results compare to 2D Reynolds-Average Navier-Stokes (RANS) simulations, based on an axisymmetric ejector designed and analysed numerically during a previous Master's thesis. The experimental setup must be made fully operational before commencing the testing campaign. Once the setup is operational, measurements are taken under various operating conditions. The reliability of measurements is ensured through an extensive evaluation of their uncertainty. The resulting data is then set side by side with the results from the RANS simulations, and this comparison enables qualitative and quantitative analyses aimed at explaining the observed discrepancies.