System energy benefit using co-flow jet active separation control for a serpentine duct

Abstract

Even though active flow control has attracted broad interest to improve flow performance by adding external energy, few studies investigate whether the energy consumed by the AFC can bring energy benefit to the system. This paper numerically demonstrates that co-flow jet (CFJ) active flow control can not only eliminate the flow separation and distortion of a serpentine duct (S-duct), but also leverage the energy state of the inlet system with the available work increased more than the CFJ energy consumed. The 3D Reynolds Averaged Navier-Stokes (RANS) equations with one-equation Spalart-Allmaras turbulence model are used and validated with experiments for the simulation. The optimum configuration of the CFJ S-duct removes the flow separation and virtually eliminates the distortion by reducing DC60 from 41.7% to 0.67%. Benefited from the attached flow, the total pressure recovery is increased by 2.0%. An exergy analysis is conducted to assess the potential benefit of the system available work. A parameter, EIPR, is introduced to measure the merit of an AFC by calculating the ratio of exergy increase to the power required by the AFC. Attributed to the zero-net-mass-flux control, all the power consumed by the CFJ actuators are absorbed by the inlet system as exergy increase. At the same time, the system exergy is further increased by 22% more than the CFJ energy consumption due to removal of flow separation that reduces entropy increase.