Scramjet Inlet Research Articles

Experimental Investigation of a Two-Dimensional and a Three-Dimensional Scramjet Inlet at Mach 7

The current experimental study at Mach 7 was carried out to investigate the viscous flow effects in a scramjet inlet with a fixed geometry operating at Mach 7.5-8. To reduce the risk of inlet unstart, an optional passive boundary-layer bleed was integrated at the throat and tested for different bleed dimensions. The passive bleed significantly reduces the lip-shock-induced separation bubble on the ramp. But the correct location of the bleed gap is important for the reduction of the separation bubble. To investigate the compression behavior, different backpressures were applied and the effects on the internal flow structure were analyzed by means of static pressure along the isolator and pitot pressure profiles at the exit of the isolator. Because the reference configuration has a very small internal contraction ratio to guarantee self-starting, the internal compression ratio was increased in three steps by means of additional sidewall compression along the internal flowpath. This includes internal contraction ratios above the starting limit. This measure led to a significant increase of the static pressure ratio at the end of the isolator. The complex flow structures are explained by means of detailed static and pitot pressure plots.

Shock tunnel studies on cowl/ramp shock interactions in a generic scramjet inlet

An experimental study is presented to show the effect of contraction ratio (CR) on shock interaction phenomena for a two-dimensional, planar scramjet inlet model. Experiments are conducted in a hypersonic shock tunnel, at Mach 8, at three CRs: 8.4, 5.0, and 4.3. CR here is defined as the ratio of the projected inlet area to the throat area. Investigations include Schlieren flow visualization around the cowl region and heat transfer rate measurement inside the inlet chamber. Various ramp/cowl shock interaction processes ahead of the inlet have been visualized using a high-speed camera. Edney type II interference pattern is observed for a CR of 4.3 with all its typical features resulting because of the forebody shock/cowl shock interaction. Peaks in the heat transfer rate measured inside the chamber show possible locations of shock impingement because of the shock interaction inside the inlet.

Investigation of Two-Dimensional Scramjet Inlet Flowfield at Mach 7

A measurement campaign has been carried out to investigate the viscous flow effects in a fixed geometry two-dimensional scramjet inlet at Mach 7. The tests have been performed in a hypersonic blowdown wind-tunnel facility. The existing boundary layer separation due to shock interaction in the inlet throat can lead to inlet unstart. Therefore, an optional passive boundary layer bleed has been integrated at the throat. The passive bleed reduces the lip shock induced separation bubble in the throat significantly. The obtained experimental wall pressure distribution and pitot pressure profiles are discussed and compared to 2-D and 3-D computational fluid dynamics calculations. To investigate the compression behavior, different backpressure ratios have been applied to the isolator flow and the effects on the internal flow structure are analyzed by means of shadowgraph pictures, static pressure distribution, and pitot pressure profiles at the exit of the isolator. The heat transfer coefficient to the inner side wall of the isolator is calculated using the time-dependent surface temperature, measured with an infrared system. The resulting 2-D Stanton number distributions are presented for different configurations and different backpressure ratios. In addition, three different Reynolds numbers have been used to investigate the effect on the separation bubble located in the corner of the first and second ramp transitions and the resulting change in ramp heat flux.

Internal Flowfield Investigation of a Hypersonic Inlet at Mach 6 with Bleed

To study the influence of viscous effects on the performance and, especially the internal flowfield, of scramjet engines, an experimental study has been carried out on a fixed geometry scramjet inlet operating at Mach 6. The tests have been performed using a hypersonic blowdown wind-tunnel facility. To reduce the risk of inlet unstart, a passive boundary-layer bleed has been integrated at the throat and successfully tested. The passive bleed reduces the lip shock-induced separation bubble on the ramp significantly. The obtained experimental results are discussed and compared with computational fluid dynamics calculations. To investigate the compression behavior, different backpressures have been applied and the effects on the internal flow structure are analyzed by means of schlieren change in pitot pressure and calculated Mach number profile base don the geometrical shape of the internal flowpath. The heat transfer coefrficient to the inner sidewall of the isolator is calculated using the time-dependent surface temperature, measured with an infrared system. The variation of the Stanton number based on different flow phenomena could be resolved successfully.

Optimum Performance of Electron Beam Driven Magnetohydrodynamic Generators for Scramjet Inlet Control

This paper is devoted to the analysis and optimization of magnetohydrodynamic control of forebody flow compression and shock incidence in scramjet-powered vehicles that would fly at Mach 5-8. The short (about 30 cm long) magnetohydrodynamic region is created by placing a magnetic coil with B-field strength of several Tesla inside the forebody and ionizing the cold air flow by high-energy electron beams propagating along the magnetic field lines. The Faraday current flowing in the spanwise direction is presumed to be collected with electrodes that are mounted on sidewalls. The purpose of the magnetohydrodynamic device is to restore a shock-on-lip condition at Mach 8 for a vehicle geometry designed for Mach 5, while operating in self-powered mode (the magnetohydrodynamic generated electricity is enough to power the ionizing beams). Location and spatial dimensions of the magnetohydrodynamic region, beam-generated ionization profiles, magnetic field strength, and the magnet size are varied to maximize performance and reduce the magnet size. Two-dimensional inviscid steady-state flow equations are solved jointly with equations describing electron beam-induced ionization profiles, plasma kinetics, vibrational relaxation, and magnetohydrodynamic effects. The model predicts an interesting phenomenon of electric current reversal due to the nonuniformity of velocity, magnetic field, and conductivity in the magnetohydrodynamic region. Vibrational nonequilibrium effects are found to be substantial. Overall, the modeling shows that a considerable reduction in magnet size is possible with the optimum choice of parameters.

Aerodynamic Performance of Scramjet Inlet Models with a Single Strut

A series of three-dimensional sidewall compression-type scramjet inlet models with single struts were tested in a Mach 4 wind tunnel to investigate the influence of a strut between the sidewalls. With the sidewalls having a fixed shape, five struts of the same width but different lengths and wedge angles were mounted, so that the effect of each model could be compared with the same geometrical contraction ratio. The aerodynamic performances of inlets were determined based on the total pressure efficiency and the mass capture ratio at the geometrical throat. Also, flow visualizations were carried out to examine the flow structure, especially around the strut. Some of the results were compared with previously examined nonstrut models. The additional shock waves generated by the strut created a large separation on the sidewalls and the strut wall, resulting in the reduction of the total pressure efficiency and the capture ratio. Due to this separation, the shock wave was observed to be oscillatory. Measurement of fluctuating wall pressure was also carried out, which revealed that, in some regions, the pressure signals were asynchronous on the left and right sides of the strut. It seems that a small difference of the separation bubble structure on each sidewall initiated a cascade effect of pressure imbalance around the struts.

Magnetohydrodynamic Energy-Bypass Procedure in a Three-Dimensional Scramjet

A generic configuration is employed to explore the kinematic and dynamic structure of the flowfield in a Mach 8 scramjet with and without magnetohydrodynamic (MHD-) bypass. Particular emphasis is placed on describing the three-dimensional interaction between the fluid and the electromagnetic field in a given plasma environment. Faraday-type operation is considered with coarsely segmented electrodes in a generator and accelerator respectively mounted on either side of a constant-area isolator/combustor element. The numerical procedure adopts a robust high-resolution technique to solve the governing equations, which include the full three-dimensional Navier-Stokes equations supplemented with electromagnetic source terms and a Poisson equation for consistency of the electric field with current continuity. Spatially variable combustion and plasma parameters are either specified or phenomenologically derived. Various three-dimensional features such as swept shock-wave boundary layer interactions have a profound impact on operation. Separated regions and vortical structures interface with the current, electric, and ponderomotive force fields to yield complex three-dimensional features that indicate that two-dimensional and inviscid analyses are inappropriate. The MHD generator shows the potential to efficiently slow down flow in the inlet, thus decreasing scramjet inlet length, and to reduce the total temperature of the flow. However, separation causes near-wall secondary eddy currents and local body force reversal, thus limiting the useful length of the generator. Accelerator operation is characterized by more prominent irreversibilities, especially near walls, where electric and body force field gradients are large. Trends in integrated pressure and viscous and magnetic force are summarized.

Performance Optimization of the Magnetohydrodynamic Generator at the Scramjet Inlet

The performance optimization problem of a magnetohydrodynamic (MHD) generator at the inlet of a scramjet engine is studied. The generator performance is characterized in terms of both the net energy extracted from the flow and the flow characteristics through the channel before it enters the combustion chamber of the scramjet engine. The analysis assumes a steady-state one-dimensional flow in which the position along the channel is treated as an independent coordinate. The performance optimization problem can then be handled by optimal control theory, in which position now plays the role of time as in a standard control problem. In this work, an optimal neural-networks-based controller design technique developed in our previous work is used. The technique is well suited for this application, because the MHD system is highly nonlinear. Furthermore, the technique is data-based, in that experimental data obtained from the system can be used to design the optimal controller without requiring an explicit model of the system. Nomenclature A f = cross-sectional area of the channel, m 2 B f

Analysis of Magnetohydrodynamic Control of Scramjet Inlets

Magnetohydrodynamic (MHD) control of forebody flow compression and air mass capture in scramjet inlets is analyzed for flight at Mach 5‐10. Because of the low static temperature, nonequilibrium electrical conductivity is created by electron beams injected into the gas along magnetic field lines. Two-dimensional inviscid steadystate flow equations are solved jointly with equations describing electron-beam-induced ionization profiles, plasma kinetics, and MHD effects. Among several scenarios considered, the scenario with an MHD accelerator has only disadvantages. A modest increase in mass capture can in principle be accomplished with a Faraday MHD generator, if the magnetic field has components both parallel and orthogonal to the flow. The principal focus is on MHD inlet control at flight Mach numbers higher than the design value. The shocks that would otherwise enter the inlet can be moved back to the cowl lip by placing an MHD generator at one of the compression ramps. Analysis shows that the best performance of such a device is achieved with a very short MHD region placed as far upstream (close to the vehicle nose) as possible, in conjunction with a high-current ionizing electron beam. An MHD energy bypass scenario with on-ramp MHD generator for inlet control is briefly discussed.

Scramjet Inlet Control by Off-Body Energy Addition: A Virtual Cowl

The theory of energy addition to hypersonic airflow off the vehicle to increase air mass capture and reduce spillage in scramjet inlets at Mach numbers below the design value is explored. The heated region creates a virtual cowl and deflects flow streamlines into the inlet. Optimization studies are performed with a two-dimensional inviscid fluid code. The best location of the energy addition region is near the intersection of the nose shock of the vehicle with the continuation of the cowl line, and slightly below that line. In that case, the shock generated by the heating is close to the shock that is a reflection of the vehicle nose shock off the imaginary solid surface-extension of the cowl. Effects of the size and shape of the energy addition region on inlet performance are also studied.

Scramjet Inlet Flow Control Using Combined Magnetohydrodynamics and Glow-Discharge-Plasma Effect

Scramjet Inlet Flow Control Using Combined Magnetohydrodynamics and Glow-Discharge-Plasma Effect

Experimental Evaluation for Mass Capture Ratio of Scramjet Inlets

Experimental Evaluation for Mass Capture Ratio of Scramjet Inlets

Magnetohydrodynamic control of hypersonic flows and scramjet inlets using electron beam ionization

Magnetohydrodynamic control of hypersonic flows and scramjet inlets using electron beam ionization

Magnetohydrodynamic Control of Hypersonic Flows and Scramjet Inlets Using Electron Beam Ionization

The possibility of controlling scramjet inlets in off-design conditions by operating a near-surface magnetohydrodynamic (MHD) system upstream of the inlet is examined. The required electrical conductivity in air is supposed to be created by electron beams injected into the air from the vehicle along magnetic field lines. A simple model of a beam-generated ionization profile is developed and coupled with plasma kinetics, MHD equations, and two-dimensional inviscid flow equations. Calculations show that an MHD system with reasonable parameters could bring shocks back to the cowl lip when flying at Mach numbers higher than those for which the inlet was optimized. The MHD effect is not reduced to heating only because the work by j X B forces is a substantial part of the overall effect. Power requirements for ionizing electron beams could be lower than the electrical power extracted with MHD, so that a net power would be generated onboard. Problems associated with high Hall fields are discussed

Effect of Noise on Roughness-Induced Boundary-Layer Transition for Scramjet Inlet

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Numerical Investigation of Strong Crossing Shock-Wave/Turbulent Boundary-Layer Interactions

Numerical results are reported for very strong fully separated three-dimensional crossing shock-wave/turbulent-boundary-layer interactions at Mach 5. The flowfield is generated by two sharp fins mounted at angle of attack on a flat plate in a manner closely resembling a portion of a scramjet inlet. Two symmetric configurations with fin angles of attack of 18 and 23 deg are considered. The flowfield is determined through solution of the full three-dimensional mean compressible Navier-Stokes equations using a sophisticated κ-e closure model

Sidewall Interaction in an Asymmetric Simulated Scramjet Inlet Configuration

The complex three-dimensional  owŽ eld arising from the interaction of a shock-induced turbulent vortical structure with a sidewall boundary layer is examined by numerically solving the Reynolds-averaged compressible Navier–Stokes equations closed with a two-equation k–2 turbulence model. The conŽ guration considered is representative of a scramjet inlet compression system and comprises two opposed sharp Ž ns mounted on a  at plate at 7 and 15 deg to the incoming  ow. The  owŽ eld arising from the impingement of a primary vortical structure on the 7 deg Ž n is found to be strongly dependent on the state of the boundary layer on this sidewall. An elegant turbulent kinetic energy production-limiting technique is employed to reproduce the complicated saddle-spiral topology observed in the experimental sidewall oil  ow pattern. Detailed analysis of the computed  owŽ eld shows that the main consequence of the interaction is characterized by the ejection of the vortex formed at the Ž n–plate junction (corner vortex in the terminology of single-Ž n  ows) in a direction along the sidewall and normal to the plate. The  owŽ eld asymptotes to the classic two-dimensional shock–turbulent boundary-layerinteraction at large distances from the plate.

217 スクラムジェットインレットの始動特性の推定法について

217 スクラムジェットインレットの始動特性の推定法について

Applications of unstructured hybrid grid method to high-Reynolds number viscous flows

An unstructured hybrid grid method is discussed for its capability to compute three-dimensional compressible viscous flows of complex geometry. A hybrid of prismatic and tetrahedral grids is used to accurately resolve the wall boundary layers for high-Reynolds number viscous flows. The Navier-Stokes equations for compressible flows are solved by a finite volume, cell-vertex scheme. The LU-SGS implicit time integration method is used to reduce the computational time for very fine grids in boundary layer regions. Two kinds of one-equation turbulence models are evaluated here for their accuracy. The method is applied to computations of transonic flows around the ONERA M5 airplane and ONERA M6 wing, and supersonic shock/boundary layer interacting flows inside a scramjet inlet to validate the accuracy and efficiency of the method

Optimization of Two-Dimensional Scramjet Inlets

The classical optimization of two-dimension al supersonic inlets for maximum total pressure recovery is extended to two-dimensional scramjet inlets. The result that optimal supersonic inlets have shock waves of equal strength is often applied to scramjets. However the typical flow turning constraint required for scramjets, along with the lack of a terminating normal shock, lead to a more involved optimization problem. Despite this, optimization by the method of Lagrange multipliers indicates that scramjet inlets with maximum total pressure recovery have external shocks with almost equal strength. The optimal total pressure recovery and turning angles for some typical scramjet inlet configurations with up to five shocks are presented.