RT - Journal Article T1 - Experimental Investigation of Instability of a Supersonic Mixed Compression Air Intake JF - mdrsjrns YR - 2015 JO - mdrsjrns VO - 15 IS - 4 UR - http://mme.modares.ac.ir/article-15-4240-en.html SP - 93 EP - 100 K1 - Supersonic Air Intake K1 - Buzz K1 - Stability Margin K1 - Oscillation Frequency K1 - Acoustic Resonance AB - An extensive experimental study has been conducted to investigate the performance and stability of a supersonic axisymmetric mixed compression air intake. The intake has been designed for a free stream Mach number of 2.0. However, tests were conducted for free stream Mach numbers of 1.8, 2.0, and 2.2. This investigation is aimed to study effects of Mach number and back pressure on the intake flow stability during the buzz phenomenon. Further, the effect of acoustic resonance on the Buzz frequency has been investigated. Buzz phenomenon is defined as the shock oscillation ahead of the intake that may occur when the intake mass flow ratio reduces. Results show that the stability margin reduces when the free stream Mach number increases. In addition, reducing the free stream Mach number and increasing the back pressure cause the oscillation frequency to increase. The main cause of instability start is flow separation on the compression ramp and two ranges of frequency of buzz oscillations are obtained, range of 100 Hz for flow instability for Mach numbers of 1.8, 2.0 and 2.2, and range off 475 Hz for flow instability in Mach number of 1.8. For both cases, the spatial domain of buzz oscillations covers the entire intake length. Further, this low and high frequency ranges have significant conformity with the zeroth-order and first-order of the acoustic resonance frequency, respectively, that increase the probability of existence of acoustic resonance driving the buzz oscillation. LA eng UL http://mme.modares.ac.ir/article-15-4240-en.html M3 ER -