Combined application of negative bowed blades and unsteady pulsed holed suction in a high-load compressor in terms of aerodynamic performance and energy efficiency

Active flow control techniques applied to compressors have been known to bring benefits at the cost of additional energy consumption. The viability of suction as a major active flow control technique, however, has been rarely estimated. In this study, energy efficiency was chosen as a parameter for the evaluation of the benefit relative to the cost of suction. The particular suction technique under investigation was endwall unsteady pulsed holed suction (EUPHS) which was combined with negative bowed blades as a novel application of the compound flow control (CFC) approach in order to obtain improved aerodynamic performance. The results showed the EUPHS was more effective in reducing time-averaged total pressure losses than the endwall steady constant holed suction (ESCHS) with the same suction-to-inlet time-averaged suction flow ratio ms. The advantage of a higher energy efficiency achieved by the EUPHS over the ESCHS, however, would correspondingly decline when ms was increased. The CFC presented a more obvious positive effect when compared with the ESCHS combined with negative bowed blades (CFC-steady) at different negative bowed angles and excitation locations, with the optimal negative bowed angle at Φ = 10° for CFC and CFC-steady. With the ensuing optimization of the CFC (Φ = 10°), the total pressure loss coefficients were reduced by 18%. A highest energy efficiency for CFC (Φ = 10°) was achieved at a relatively lower ms = 0.4%, and the time-averaged energy efficiency reached as high as 504%. The potentials of CFC (Φ = 10°) at different incidence angles were also validated.