PIV Measurement of Supersonic Swirling Jet
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Supersonic fuel injection with swirl is investigated to enhance the air-fuel mixing in scramjet combustors. We studied the effect of supersonic swirling jet for mixing enhancement with a PIV. In measurement of supersonic flow with a PTV, it is important for particles to track the flow, particularly when they pass through the shock wave. In this work, the size of particles was specified by gravitational separation. The response of the particles was examined by measuring velocity response downstream of a Mach disk. These results guaranteed the accuracy of the PIV system. Under-expansion jets in both cases with and without swirl were examined by the PIV. We got the result that the swirling jet mixed better than none swirling jet.Keywords:
Scramjet
Choked flow
Fuel injection schemes impact the combustion efficiency, flame stability and thermoacoustic instabilities in supersonic combustion. Usually, the fuel injection can be upstream or downstream the cavity. The present studies concerns the effect of the fuel injection scheme, upstream/downstream, on the combustion instabilities and efficiency in supersonic combustion. The combustion efficiency is assessed based on the turbulent mixing and temperature inside the cavity. Due to the fact that the experimental studies of supersonic combustion poses significant challenges. Therefore, computational approaches are a promising alternative for the numerical studies of supersonic combustion. In the present study the computations are performed using the large-eddy simulation approach along with a flamlet combustion model. The analysis reveals the presence of a region of high level of temperature, NO and , inside the cavity. The reverse flow causes a preferential distribution of this region towards the step side of the cavity.
Scramjet
Large-Eddy Simulation
Choked flow
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The expansion tube is the only type of ground test facility currently able to simulate high-Mach-number scramjet test flows. These access-to-space flow conditions are characterized by total pressures of the order of gigapascals. The University of Queensland's X2 expansion tube facility has recently been used to generate scramjet flow conditions between Mach 10 and 14, relevant to a 96 kPa dynamic pressure ascent trajectory, with total pressures up to 10 GPa. These experiments have matched flight enthalpy and Mach number while achieving test flow static pressures considerably higher than the true flight values. This demonstrates that Reynolds number can also be matched, even for subscale models, thereby addressing one of the major challenges for ground testing of high-Mach-number scramjet design concepts. The routine operation of expansion tubes at high flight enthalpies has already been established; but for operation at lower enthalpies (relevant to scramjet testing), the wave processes within these machines become more tightly coupled and difficult to tune. This paper details the combined analytical and numerical processes used to develop new flow conditions in the X2 facility. Experimental results are presented, and axisymmetric computational fluid dynamics analysis is used to fully characterize the test flow properties.
Scramjet
Stagnation enthalpy
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Scramjet
Stagnation enthalpy
Piston (optics)
Total pressure
Expansion tunnel
Dynamic pressure
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In order to explore how the change of attack angle at different frequencies influences the start property of inlet,this paper conducted a wind tunnel experiment for the sidewall compression scramjet inlet with Mach number 3.85 and attack angle at different frequencies.The sidewall compression scramjet inlet,with designed Mach number 6 and start Mach number 2.5,was subject to several flow tests,when attack angle changed from 0°to 8.15° again down to 0°,with the frequency at 0.8,1.6,3.2 Hz and 6 Hz,respectively.Results show that at each frequency,the inlet in a periodic oscillation succeeds to go through a start-unstart-restart process.With the increase of frequency,attack angle gradually goes up in the first periodic oscillation,and sharply goes down in the proceeding periodic oscillation.
Scramjet
Oscillation (cell signaling)
Supersonic wind tunnel
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An introduction to supersonic gas flow is given, with emphasis on the features that distinguish supersonic from subsonic flow. Experimental methods for the study of supersonic flow are briefly considered and some simple flows are described.
Choked flow
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Supersonic combustion ramjets or scramjets offer significant performance benefits over other propulsion technologies for atmospheric flights at hypersonic speeds, as a result of their ability to extract the oxygen for combustion from the atmosphere.Supersonic combustion in scramjet is still a challenging one. The complexity of supersonic combustion involves turbulent mixing, shock interaction and heat release in supersonic flow. This project deals with the enhancement of supersonic combustion by breaking down the streamwise vorticity and enhancing the rate of fuel air mixing in supersonic combustion. The amplification of stream wise vorticity is achieved out of the interaction between an oblique shock and fuel injector.
Scramjet
Ramjet
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View Video Presentation: https://doi.org/10.2514/6.2021-1517.vid The energy transfer mechanisms for Mack's second mode and a supersonic mode based on spatial linear stability theory for a Mach 6 flat plate flow with $T_w=0.5 T_\infty$ is investigated. For the current conditions, the supersonic mode is unstable but obtains a relatively low amplification rate in comparison to the second mode. The energy analysis conducted in this paper shows that the total energy of the second mode is available throughout the boundary layer, however, for the supersonic mode, it is concentrated closer to the wall.~The combined effect of thermal production and production density dissipates most of the energy away from the critical layer for the supersonic mode.~As opposed to the second mode, a significant amount of energy is available in the free-stream in the case of supersonic mode. It is found that the energy is provided from the pressure strain transport term counteracting the shear-work. In the second part of the paper, direct numerical simulations were performed for the same flow conditions, and a decomposition of the disturbance flow field was performed. Some differences in the growth rates especially in the region where the supersonic mode appears was observed. Although the flow decomposition showed that the unstable mode F dominates the disturbance flow field, there appears to be a non-negligible contribution from the stable supersonic mode.
Choked flow
Mode (computer interface)
Dynamic Mode Decomposition
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The aim of this letter is to present an original experimental technique to study weak shock wave in a minitube. Thus, we designed an apparatus that can be connected to any classical shock tube in order to characterize high speed flows induced by the shock wave transmission in minitubes. We proposed appropriated measurements based on high speed strioscopy coupled with pressure sensors. Two minitube diameters are considered: 1.020±0.010 and 0.480±0.010 mm. We realized preliminary experimental and numerical campaigns with an incident shock wave Mach number at 1.12±0.01. The generation of a microshock wave was observable in the two minitubes. For the smallest minitube, we found an attenuation of the strength of the shock wave with a decrease of 1.8% of the Mach number.
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Three-dimensional computational fluid dynamic simulations were performed for the Mach 12 Rectangular-to-Elliptical Shape-Transitioning scramjet. Present injector arrangements at the combustor entrance displayed low jet penetration, resulting in a oxygen-based combustion efficiency of 84.9%. It is proposed to convert three cowl-side injectors into one larger injector located further upstream. To support this, injector configurations were investigated computationally, taking injectors optimised for penetration at lower Mach numbers, and evaluating their performance at higher Mach number flight conditions. It was determined that reduced performance of these optimised injectors was encountered at scramjet flight conditions above their design point, with circular injectors at equal or greater injection angles displaying greater penetration and mixing capabilities.
Scramjet
Penetration (warfare)
Ramjet
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