Delaying the buzz onset in a supersonic inlet by multi-row disk concept

• Increasing the number of disks in the MRD concept so that they covered entire surface of the spike tip leads to the buzz onset postponement to an exit blockage ratio 4.5 % greater than the base inlet. • Comparative analysis revealed significant reductions in total pressure and mass flow rate fluctuations due to the implementation of MRD. • The investigation of one buzz cycle indicated that while MRD can postpone the buzz onset and alleviate the adverse effects of the buzz oscillations, it needs a discharge mechanism to further eliminate the separation region at higher exit blockage ratios. • Combining MRD with the discharge mechanism can delay the buzz onset up to an exit blockage ratio, which is 22.5 % greater as compared with the base inlet. • The findings of this research demonstrated that the MRD method is an efficient and straightforward approach for improving the inlet stability. At subcritical operating conditions of the supersonic air inlets, if the mass flow rate drops below a certain threshold for any reason, the shock waves begin to oscillate back and forth through the inlet, causing the inlet to become unstable. This event is known as the buzz phenomenon. A literature review reveals that one of the proposed methods for improving the inlet stability is using the Multi-Row Disk (MRD) arrangement concept. In this method, part of the inlet compression body is replaced with a series of disks, and between these disks, a series of cavities are created that can prevent flow separation. The use of this method is novel and very limited studies have been conducted on it so far. Most of the studies have focused on the effects of the size and number of cavities that are created between the disks on the inlet performance parameters, and no research has been done about the inlet stability and buzz phenomenon. Therefore, the main goal of the present study is to investigate the effects of MRD method on preventing and postponing the buzz phenomenon. In this research, an axisymmetric supersonic inlet is computationally studied at a free stream Mach number of 2. The Reynolds-Averaged Navier-Stokes (RANS) equations are solved in an unsteady state and the k-ω turbulence model is used to account for the turbulence effects. The results showed that MRD method can delay the buzz onset and increase the subcritical stability margin of the inlet significantly. In addition, this method, relying on simple geometric principles, not requiring complex control systems, and not adversely affecting the inlet performance parameters, can improve the inlet stability by decreasing the amplitude and frequency of the buzz oscillations.