Multi-row disk arrangement concept for spike of axisymmetric air inlet

In this paper are presented the advanced concept of air inlet applying for the air breathing propulsion systems of hypersonic flight vehicle like a space plane. It is designated to be the Multi-Row Disk (MRD) inlet It was devised to give the better inlet performance (mass capture ratio (MCR) and total pressure recovery (TPR)) over the wide flight conditions up to around Mach 6 by improving its off-design performance. The MRD inlet is a kind of axisymmetric air inlet composed of the center conical envelope spike and the cowl. As shown in Fig. 1, the unique structure is employed on the conical envelope spike that is composed of a tip cone and several round disks arranged so as to shape the conical envelope. The space in between tìie disks can be changed mechanically and thus the overall spike length of the MRD inlet is adjustable to meet the shock on lip condition at the given flight speed independent of the throat area control. The performance of MCR and TPR are governed respectively by the shock on lip condition to reduce a spillage flow and the throat area control and thus the MRD inlet is easier to improve them independent from each other under the off design conditions. It was made clear from the result of wind tunnel tests that the MRD inlet achieves the same on-design performance as the conventional inlet with the solid surface conical spike and improves TPR by 10% comparing with the conventional ones in case of flow matching with the turbo fan. It was revealed from the result of wind tunnel tests and numerical simulations that the cavities formed in between the disks gave little effect on a boundary layer growth.