Yusuke Maru

Experimental Study on Aerodynamic Characteristics of Telescopic Aerospikes with Multiple Disks

In this paper, experimental studies on telescopic aerospikes with multiple disks are reported. The telescopic aerospike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon,which many researchers have reported. The occurrence of buzzing might be critical to the vehicle because it brings about severe pressure oscillations on the surface. Disks on the shaft produce stable recirculation regions by dividing the single separation flow into several conical cavity flows. Therefore, the telescopic aerospikes with stabilizer disks are useful without being any length constraints. Aerodynamic characteristics of the telescopic aerospikes were investigated using wind tunnel tests. Transition of recirculation/reattachment flow modes of a plain spike causes a large change in the drag coefficient. Because of this hysteresis phenomenon, the plain spike is unsuitable for fine aerodynamic control devices. Adding stabilizer disks is effective for the improved control of aerospikes.

Flow Oscillation Characteristics in Conical Cavity with Multiple Disks

ac = speed of sound inside the cavity D = cavity depth f = frequency fn = predicted peak frequency kc = ratio of the average vortex convection speed to the freestream flow speed L = cavity length L=D = length-to-depth ratio of the cavity M1 = freestream Mach number n = mode number pref = reference pressure, 2 10 5 Pa q1 = freestream dynamic pressure r = recovery factor in temperature U1 = freestream velocity = phase constant between vortex shedding and the acoustic wave response in the cavity = specific heat ratio of the ideal gas f = power spectral density as function of frequency Introduction

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 the 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 ondesign 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.