Effects of forebody boundary layer on the performance of a submerged inlet

Abstract

The use of a submerged inlet is advantageous in modern aircrafts because of its low drag resistance, small radar cross section and ease of maintenance. Although it is well known that the forebody boundary layer deteriorates the aerodynamic performance of a submerged inlet, the level of impact has not yet been fully quantified. To quantify the forebody boundary-layer effect, a submerged diverter was designed to remove a portion of the low-energy boundary flow. The flow pattern and aerodynamic performance of a submerged inlet, with and without the diverter, were investigated by wind-tunnel experimentation and numerical simulations. The effects of mass flow, free stream speed, angle-of-attack and sideslip angle on the aerodynamic characteristics of the inlet with and without the submerged diverter were studied, over an operating envelope of M 0 = 0.3 ∼ 0.6, $\alpha$ = –6 $^{\circ}$ ∼ 8 $^{\circ}$ and $\beta$ = 0 $^{\circ}$ ∼ 4 $^{\circ}$ . The results indicate that both the total pressure loss and the circumferential distortion can be significantly reduced with the removal of the forebody boundary-layer low-energy flow. Meanwhile, the main mechanisms for losses in the submerged inlet were also analysed.

S-duct flow distortion with non-uniform inlet conditions

“…Rein and Koch 48 demonstrated that the distortion at the AIP increases proportionally with the thickness of the inlet boundary layer. Thick boundary layers were found to reduce also the pressure recovery on the intake 49 – 51 and to promote non-uniform radial pressure loading on the compressor blades which could trigger stall inception. 4 Different azimuthal orientations of the approaching boundary layer were also investigated for intakes under yaw and pitch angles 52 , 53 , 18 were found to notably influence the fan-face pressure and swirl distortion.…”

Prepositive Synergistic Bulge Design for Improving Aerodynamic Performance of Submerged Inlet

“…Therefore, how to improve aerodynamic performance of submerged inlets has become a key issue. Many scholars have conducted series of research on it, including the optimization of the design of the inlet shape [5][6][7][8][9], the application of active flow control methods such as jet [10][11][12][13][14][15][16], and the exploration of passive flow control methods such as setting synergistic components near the inlet [17][18][19][20][21][22][23][24][25][26][27].…”

“…The results show that the ridge structure can split the boundary layer before the inlet's entrance, but it is necessary to ensure that the swirling vortex of the side edge of the inlet can pass through safely. Xie et al [25] proposed a method to remove part of the low-energy boundary flow and improve the inlet's performance by setting a submerged deflector in front of submerged inlet and studied it through numerical simulation and wind tunnel tests. After adding the submerged deflector, the inlet's total pressure recovery coefficient is increased by 3.3%, and its circumferential distortion DC60 is reduced by 28.2%.…”

Numerical Investigation of a Vortex Diverter Designed for Improving the Performance of the Submerged Inlet

“…Xie designed a boundary layer splitter that improved the quality of airflow inside the intake duct by displacing the lowenergy flow in the boundary layer. The study results showed an improvement of 3.3% in the total pressure recovery coefficient of the intake duct and a 28.2% reduction in circumferential distortion DC60 [21]. Saheby designed a ridge-type vortex generator near the entrance, which can divert the boundary layer at the intake entrance.…”