Abstract
Serpentine inlet is widely used in military and civil aircraft due to its good stealth performance. However, it generates a high total pressure loss and swirl distortion which significantly affects the performance and the stability of the compressor. In order to improve the quality of the flow field at the aerodynamic interface plane (AIP), a flow control is required inside the serpentine inlet.
The objective of this paper was to study the effectiveness of the blowing active flow control on reducing the swirl distortion and on improving the total pressure recovery at the AIP, by reducing the low-momentum flow in the serpentine inlet. The mechanism of the blowing control and the effect of the design parameters (i.e. blowing angle, blowing position and blowing flow rate) on the aerodynamic performance at the AIP were studied. The optimal solution was applied to the full flow path of the serpentine inlet and the fan-stage.
The numerical results showed that the quality of the flow field at the AIP were effectively improved by blowing high-energy airflow into the boundary layer of the serpentine inlet. The blowing position had a high influence on the blowing effect, and upper wall blowing scheme obtained greater benefits than lower wall blowing scheme and combination blowing scheme. In addition, the blowing angle should be selected to avoid the high-energy air from pipes mixing with mainstream in the serpentine inlet which will result in an additional total pressure loss. When the ratio of the blowing mass flow rate to the designed mass flow rate of the serpentine inlet was about 1.5%, the swirl distortion on the AIP reached a minimum value, which then did not show a significant difference in performance with blowing ratio increased. When the upper wall blowing scheme was adopted with a blowing angle of 6 degrees and a blowing ratio of 1.5%, the AIP aerodynamic performance achieved the highest improvement, with an increase of the total pressure recovery factor by about 1%, and a decrease of the circumferential total pressure distortion and the swirling distortion by 60% and 61%, respectively. With the optimal control scheme, the area of the low-pressure region near the upper wall was remarkably reduced, and the performance of fan-stage was improved, with an increase of the pressure ratio by about 1.5%, and the efficiency of the single-stage compressor by about 3.1%, respectively.
