Sharif Digital Repository

An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at Mach numbers from 1.8 to 2.2 and at different values of mass flow rates. Frequencies of the buzz were achieved from the pressure data as well as the high speed shadowgraph pictures. For each Mach number, two main frequencies for the buzz were obtained. The inlet at its design condition was stable, but when the mass flow rate was reduced, at first the shock wave started to oscillate with a small amplitude which is matched the Ferri criterion (little buzz). In this situation, both high- and low-frequency oscillations occurred; however, the high frequency one was dominant, but the oscillations seemed to be... 

The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional (3D) modeling in comparison with the axisymmetric one. For this purpose, a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers, using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ω turbulence model, for a free-stream Mach number of 2.0 and at zero degrees angle of attack. The grid for the 3D cases was a 14.4-degree sector, instead of a 360-degree domain one, with rotational periodic boundary condition for the side boundaries. The results show that both... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

A new structure for the compression surfaces of a supersonic inlet is proposed which has improved the target performance parameter i.e. total pressure recovery ratio. This idea resulted in development of a new type of supersonic inlet, utilized four ramps and a cone simultaneously as the compression surfaces. A prototype of the proposed inlet has been designed for a free stream Mach number of 3 and its performance has been evaluated via numerical simulation for both design and off-design conditions. The performance of the newly designed inlet has been compared to the existing experimental data of two double-cone inlets. The acquired data are further compared with analytical calculations of... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and... 

Comprehensive numerical analyses are conducted to simulate and capture “Buzz” phenomenon in a supersonic mixed compression air inlet. The buzz is an unsteady self-sustained feature that occurs in supersonic inlets, especially when operating in their subcritical condition. In such a situation, the shock waves oscillate along the inlet and cause mass flow fluctuations inside the inlet that will deteriorate the engine performance significantly. An axisymmetric unsteady numerical simulation was used to solve the Navier–Stokes equations combined with the URANS SST k–ω turbulence model. The simulations for two different free-stream Mach numbers of M∞=2.0 and 2.2 and at two specific subcritical... 

Effects of various boundary-layer bleed locations on the stability of an axisymmetric supersonic inlet has been investigated experimentally. The bleeds were located on the inlet compression cone and were designed to improve the stability margin of the inlet. The main objective of the study was to identify the boundary-layer bleed location and its effectsonthe improvementofthestability marginofthe inlet.Inaddition,a buzz precursordetection methodology based on the rms level has been introduced. Experiments have been carried out on a mixed-compression inlet with a design Mach number of 2.0 and three different bleed locations at three freestream Mach numbers of 1.8, 2.0, and 2.2. All tests were... 

The performance characteristics of an axisymmetric inlet at its design and off-design operational conditions are experimentally investigated. The model is tested for wide ranges of free stream Mach numbers, M∞ = 1.5-2.5, and mass flow rates. For each test, the pressure recovery, the mass flow passing through the inlet and the pressure distribution over the spike and the cowl are measured. In addition, the shock wave formed in front of the inlet is visualized. The characteristic curve of the inlet is then obtained for each free stream Mach number. As the Mach number is increased, the pressure recovery is reduced, but the maximum value of the mass flow rate grows up. Variations of the mass... 

The flow over a supersonic inlet has been investigated experimentally and numerically at a free stream Mach number of 2 and a zero degree angle of attack. Wind tunnel tests were performed to obtain the performance parameters of the inlet and were used as a baseline and validation tools for the numerical code. A heat source was added to the flow field at a distance ahead of the inlet. The effect of heat source addition on the main performance parameters of the inlet is investigated numerically. Results show that the heat source considerably reduces drag coefficient; however, its effect on pressure recovery is not favorable. This unfavorable effect was then minimized by controlling heat source... 

An experimental study was carried out on an axisymmetric supersonic inlet with external compression. The scope of this study was to investigate the general characteristics of the inlet buzz under various design and off-design conditions. The model was equipped with accurate and high frequency pressure sensors and the tests were conducted at Mach numbers varying from 1.8 to 2.5, at various angles of attack, and at different mass flow rates. Shadowgraph flow visualization, together with a high speed camera, was used to capture the external shock structure in front of the inlet. Frequencies of buzz were obtained from both the shadowgraph pictures and analysis of the pressure data. The amplitude... 

An extensive wind tunnel test series were conducted on an axisymmetric supersonic inlet. The model was tested at Mach numbers from 1.8 to 2.2 and at different values of mass flow rate. Shadowgraph flow visualization was used to capture the external shock structure in front of the inlet. The goal of this study is to find out the general characteristics of the inlet buzz. Frequencies of the buzz have been achieved from the analysis of the pressure data as well as the shadowgraph pictures. The amplitude of the shock waves motion has been measured from the visualization pictures too. In the some large value of mass flow rate, the frequency of shock oscillation increased versus Mach number. Also... 

Experiments were conducted to study various kinds of Shock wave/Boundary Layer Interaction (SBLI) in an axisymmetric mixed-compression inlet. Experimental findings were compared and verified by numerical solutions where possible. Different types of SBLI relevant to the mixed-compression inlets are classified. Interactions of normal shock wave/boundary-layer at subcritical condition and in buzz condition are investigated using Schlieren and shadowgraph flow visualization as well as unsteady pressure recordings. The data is compared with the CFD predictions. Interactions of cowl lip reflected oblique shock and the terminal normal shock with the spike boundary-layer at both critical and... 

The effects of geometrical scaling on a supersonic external compression axisymmetric inlet are investigated. Various lower and higher geometrical scales of supersonic inlet are considered as the case studies. The inlet flow is simulated numerically using RANS solver along with the SST k-w turbulence model. The numerical results are in an acceptable agreement with the NACA experimental data at free stream Mach number of 1.79 and at zero angle of attack. The results show that the static pressure distribution of the inlet flow experiences some differences for various scales especially at the regions of the flow entrance and throat area. The mean flow Mach number and the mass flow rate at the... 

Heat source addition to the axisymmetric supersonic inlet may improve the performance parameters, which will increase the inlet efficiency. In this investigation the heat has been added to the flow field at some distance ahead of an axisymmetric inlet by adding an imaginary thermal source upstream of cowl lip. The effect of heat addition on the drag coefficient, mass flow rate and the overall efficiency of the inlet have been investigated. The results show that heat addition causes flow separation, hence to prevent this phenomena, roughness has been added on the spike surface. However, heat addition reduces the drag coefficient and the inlet mass flow rate considerably. Furthermore, the... 

Feasibility of an innovative buzz detection technique through measuring the static pressure outside a mixed-compression supersonic inlet is studied. The buzz is an instability phenomenon that occurs almost in all supersonic inlets. During the buzz, shock oscillation along with pressure and mass flow fluctuations affects the performance characteristics of the inlet. The main objective of this paper is to introduce a simple and easy-to-implement method for investigation of the buzz phenomenon in a supersonic inlet. The experimental data for far field-based are compared with those of the model-based one at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack for a... 

A series of wind-tunnel tests were conducted on a Y-shaped diverterless supersonic inlet (DSI) in order to investigate its performance at various operating conditions. The present DSI was designed for a freestream Mach number of M∞ 1.65. The experiments were performed at supercritical, critical, and subcritical operating conditions and at 0 deg angle of attack and angle of side slip. The results showed that the present DSI had an acceptable performance at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions. At low subcritical operating conditions, the supersonic flow pattern remained symmetric too. However, at high...