SR-72 Confirmed: Mach 6 Project Blackswift

a reply to: clay2 baraka

I thought that was the case as well, be interesting to see if Zaph pipes up again.

Experimental study on the thermodynamic characteristics of the high temperature hydrocarbon fuel in the cooling channel of the hypersonic vehicle

Authors:

Li e al

Abstract:

Cooling is one of the key technologies for the scramjet considering the enormous thermal load and the demand of reusable long-range mission. In the regenerative cooling process, hydrocarbon fuel flows through the cooling channel, gets heated and experiences severe thermal properties changes. The compressibility of fuel becomes non-negligible and possible dynamic process emerges, which affects both the characteristics of fuel cooling and fuel mass flow control. As a result, the dynamic characteristics of the high temperature hydrocarbon fuel within the cooling channel must be carefully studied. In this work, experiments are conducted at different simulated engine working conditions. The settling time of pipe pressure drop is used to characterize the dynamic process of the outlet fuel mass flow, because the outlet temperature of the fuel is too high to measure the fuel mass flow directly. In conditions of the variation of inlet fuel mass flow and backpressure disturbance, overshoot of the pressure drop is observed and the magnitude of which varies with the working conditions. The settling time of outlet fuel temperature and wall temperature channel firstly increases, then decreases with the increase of the outlet fuel temperature. The settling time of both outlet fuel temperature and wall temperature increases with the increase of the heating heat flux. The experimental results in this work are expected to provide supports to the engine control system design.

www.sciencedirect.com...

Numerical investigation on drag and heat reduction mechanism of combined spike and rear opposing jet configuration


Authors:

Huang et al

Abstract:

In order to reduce the hypersonic aerodynamic drag and heating, a combined spike and rear opposing jet configuration is proposed in this paper, and the CFD method is adopted to analyze the drag and heat reduction efficiency. The results show that the spike pushes the bow shock wave away from the blunt body, which translates the normal shock wave into the oblique shock wave and reduces the shock wave intensity. In addition, the low temperature jet gas is injected into the flow field, which reduces the temperature of the flow field after the shock wave. So the combined configuration reduces the aerodynamic drag and heating of the blunt body by the reconstruction of flow field, and the drag and heat reduction efficiency is better than the other configurations that already exist. The influences of the length of spike, total pressure of the opposing jet and jet gas on the drag and heat reduction efficiency are studied. The results show that increasing the length of the spike and the total pressure of the opposing jet can effectively improve the drag and heat reduction efficiency, and the decreasing rates of the aerodynamic drag and heating slow down gradually with the increase of above two parameters. In addition, the nitrogen has the best drag reduction efficiency and the carbon dioxide has the best heat reduction efficiency. The investigations in this paper verify the advantages and application in engineering of the combined configuration proposed in this paper.

www.sciencedirect.com...

Design exploration of combinational spike and opposing jet concept in hypersonic flows based on CFD calculation and surrogate model

Authors:

Ou et al

Abstract:

The combined thermal protection system has led the drag and heat reduction of hypersonic reentry vehicles to a new developing direction. In order to obtain better resistance to aerodynamic drag and heat while maintain the work stability of the aircraft at the same time, the optimization design of the combined thermal protection system is indispensable. In this paper, a CFD numerical simulation method is combined with a surrogate model based multi-objective optimization algorithm to optimize the configuration of a combinatorial spike and opposing jet thermal protection system in a hypersonic flow with the freestream Mach number of 5.75. The obtained results show that when the total drag coefficient (Cd) and the heat fluxes on the head of the blunt body (Q) are the objective functions, the diameter ratio of the aerodisk to the blunt body bottom (d/D) has no significant effect on the drag and heat flux reduction, and it can be neglected in the optimization process. While the objective functions Cd and Q are affected by the three variables the length-to-diameter ratio of the aerospike (L/D), the jet pressure ratio (PR), and the nozzle radius (r0) in similar ways. Therefore, in this case, the optimization problem can be transformed into a single-objective optimization problem. The quadratic response surface model established by sample points obtained by the orthogonal experimental design method is of high simulation accuracy, with the determination coefficients of Cd and Q are 0.964 and 0.965 respectively, and there is only a difference of −6.96% in the objective function Cd, −0.93% in Q between the optimization results and the CFD results. The combined thermal protection system has better performance in both drag and heat reduction than the single spike or opposing jet systems. Compared with the pure blunt body, the total drag coefficient and heat flux on the head of the blunt body with the combined thermal protection system have significantly decreased, with the Cd goes down 86.66%, and the wall heat flux Q drops off 96.37%.

www.sciencedirect.com...

Numerical and experimental investigation of an adjustable dual-channel supersonic diffuser

Authors:

Yicong et al

Abstract

The conventional diffuser performance is constrained by the optimal contraction ratio and the start-up contraction ratio. In order to balance the start-up performance and operating performance, the diffuser can be designed to be adjustable. Existing adjustable diffuser configurations have different drawbacks and most of them lack experimental verification. Therefore, a new parallel dual-channel diffuser scheme is proposed. The diffuser operates at Ma 4 and uses simple transmission devices to achieve an adjustment in the contraction ratio. The performances of the dual-channel mode, single-channel mode and the mode conversion are tested experimentally. The diffuser exhibits good starting and anti-backpressure capabilities. The unsteady numerical results show that the increase in the anti-backpressure capability of the diffuser is mainly due to the increase in the number of oblique shock waves in the main channel and the backward movement of the leading shock.

www.sciencedirect.com...

To address the challenge DARPA has initiated the Materials, Architectures, and Characterization for Hypersonics (MACH) programme. The programme seeks to develop and demonstrate new design and material solutions for sharp, shape-stable, high heat flux capable leading edge systems for hypersonic vehicles travelling more than five times the speed of sound.

DARPA is seeking expertise in thermal engineering and design, advanced computational materials development, architected materials design, fabrication and testing (including net shape fabrication of high temperature metals, ceramics, and their composites), hypersonic leading-edge design and performance, and advanced thermal protection systems. DARPA has specified that it does not want research “that primarily results in evolutionary improvements to the existing state of practice”.

The MACH programme will comprise two technical areas. The first area aims to develop and mature a fully integrated passive thermal management system to cool leading edges based on scalable net-shape manufacturing and advanced thermal design. The second technical area will focus on next-generation hypersonic materials research, applying modern high-fidelity computation capabilities to develop new passive and active thermal management concepts, coatings, and materials for future cooled hypersonic leading edge applications.

www.janes.com...

Those freakin aussies...

Cavity enhanced jet interactions in a scramjet combustor

Authors:

Roos et al

[b]Abstract:[/b]

The shock structure around a fuel jet drives most of the initial mixing in a scramjet combustor, making it of interest for mixing enhancement studies. The effect of a cavity placed upstream of a fuel injector on the jet interaction of a transverse jet in a supersonic crossflow was examined numerically in this work. The cavity was found to significantly alter the structure of the typical supersonic cross-flow jet interaction. The typical horseshoe vortices were found to be absent and the barrel shock was found to be larger and more upright than in the no-cavity case. This was caused by the cavity recirculation shielding the fuel jet. The shock structure around the cavity was found to decrease the strength of the bow shock, reducing total pressure loss in the flowfield close to the injector. A small region of fluid above the cavity circulation was found to be the origin of vortical structures in the jet interaction, as opposed to the wall boundary layer in the conventional jet interaction. The presence of the fuel jet was found to alter the flow behaviour inside the cavity from closed cavity flow to open cavity flow, with the recirculation rising out of the cavity. This transition from closed to open cavity flow was found to be turbulence model dependent, however the main flow features and behaviour were shown to be maintained across turbulence models. Fuel was entrained in the cavity for the configuration under investigation, however this was dependent on fuel injection pressure, with no fuel entering the cavity at lower injection pressures.

www.sciencedirect.com...

www.wired.com...

a reply to: anzha

Not a fantastic article.

May be it can solve the problem of propulsion more than the scramjet engine.

a reply to: darksidius

It's really just a stye of combustor. It uses the shockwave to create pressure instead of allowing the gas/air mix to deflag (lowering pressure). It will still face all the challenges of ramjets/scramjets if used as a combustor in a ram-/scramjet and offers little if any efficiency in that form. Not really my field, but I'm not sure if it would work in a scramjet because of the supersonic flow through the engine.

The 5% improvement they hope for is using RDE combustors in a turbofan which has a lot of fundamental hurdles to overcome, none of which managed to get mentioned in that article. 10% gains might be possible in the larger turbines which the navy uses to propel ships. Mathematically, if not yet in practice, you might even get higher efficiency from larger electric production gas turbines. A lot will depend on how it scales up or down where CFD isn't always accurate -- 5% is actually a big deal, though, which is why they are chasing it.
The article read as though the author didn't really understand what is going on. If he actually talked to people involved instead of quote-mined, then I'm not sure he understood them. Or he did an exceptionally poor job of communicating the concept.
Problems include pressure/temp spikes, slowing the flow before it gets to the turbine blades. Basically instead of the smooth flow created by normal deflag process, you're sending a rotating pressure wave into the turbine section and basically beating the # out of the blades and other components. Uneven or exceptionally high temps inside the turbine section are also dealbreakers (or blade breakers, as it were). And you have to make sure the shockwaves aren't advancing into the compressor section where it can wreck havoc as well.
The solution to those problems means generally speaking defusing or slowing the air out of the RDE combustor before it gets to the turbine section. That means a loss of pressure, and associated inefficiency. Basically, it offers higher efficiencies through higher pressures, but practically will need to lower pressure to be functional/practical. If we see a 10% increase in sfc efficiency but you have to replace the engine or it breaks every three hours, we're spinning our wheels. It may scale down better than up. It might be a deadend. Or we might get more efficient turbofans. No one really knows, which is why they've spent money left and right chasing it down and following closely turbine material science.

But for aviation, it's not a radically different engine as much as a different form of combustor inside already very conventional turbojet/fans. They've got very loud, very short lived, relatively small engines running already. The quest is to make them practical.

a reply to: RadioRobert

To create content pressure...

It is like supercritical fluid in that respect. You get more energy out of it compared to a normal engine.

And old hat here on ATS. This has been discussed since the “donuts on a rope” photo (and Zaphod’s answer is very prescient!!). The problem has been high temperature ceramics.

Now, do you think Boeing or Lockheed hasn’t figured it out?

Nice that Wired posted a story but it is twenty years too late!

We’ve got even better stuff up there!!

I hope so

a reply to: TEOTWAWKIAIFF

Sure if you can find materials to take the giant pressure spikes and associated rapidly changing giant temperature differences on different parts of your turbine disc(s) and associated mechanical bits, then you can take advantage of the pressure/temps created by the rotary detonation engine. Unfortunately, that isn't as simple as "ceramic blades". And in the meantime everyone is working on different ways to slow the shockwaves before they reach the turbine. Which lowers the pressure/efficiency of the RDE turbine.

Investigation of turbulence flow characteristics in a dual-mode scramjet combustor using hydroxyl tagging velocimetry

Authors:

Ye et al

Abstract:

The results of an investigation of the turbulence characteristics of a kerosene-fueled, dual-mode scramjet combustor are reported in this paper. The combustor had a cavity flame holder and was operated at an inlet Mach number of 2. The combustor was made to transition across different modes by adjusting the fuel injection and inlet flow total temperature. The velocity and fluctuations thereof in the flow field upstream of the combustion zone were measured using the hydroxyl tagging velocimetry method. Given a signal-to-noise ratio of about 4 for the OH lines and considering the effect of dithering of the optical equipment owing to strong vibration, the uncertainty in the measured velocity was about 29 m/s. The computational fluid dynamics solution of the flow was compared with the measurements, and the computed positions of the shock wave trains were used to distinguish the combustion modes. The results show that the turbulence fluctuation velocity (u'rms) in the supersonic mode was the same as that in the case of the nonreacting flow, but it was considerably higher in the subsonic mode. During the ram-to-scram process, the turbulence intensity (u'rms/ū) declined exponentially as the local Mach number of the flow field upstream of the combustion zone increased.

www.sciencedirect.com...

Experimental study of flame stabilization in a kerosene fueled scramjet combustor

Authors:

Wang et al

Abstract:

Kerosene flame stabilization in a Mach 2.0 model combustor was studied experimentally by using laser-induced fluorescence and high-speed photography. The interferential fluorescence in OH-PLIF was eliminated by the comparison with kerosene-PLIF. The reaction layers of flame were marked by the sharp gradient regions of fluorescence intensity in OH-PLIF. The results show that the flame is stabilized in the cavity at a lower equivalence ratio. As the equivalence ratio is increased, flame is stabilized in the cavity shear layer and spreads into the mainstream. The oscillations of the flame are quantified and correlated with the pressure fluctuations of the pseudoshock. Low-frequency oscillations are found to be amplified in the upstream propagation. As the inlet stagnation temperature rises, ram-scram transition occurs at a higher equivalence ratio. Kerosene flame is always stabilized in the cavity region without propagating upstream within the range of current inlet stagnation temperature (885–1285 K).

www.sciencedirect.com...

Im sure there are several top secret drones flying around already today. Via military and CIA... Ive personally seen a craft twice back in late 2000's was rounded in front transitioning to more square in middle to finally more triangle shape in the back. Roughly the size of a dc10 maybe smaller.....was fkying around 3000 at night was pitch black no lights ....the cool thing about it is once it kicked on its powerful engines it enveloped in some type of light from engines or plasma , then a bright light from back and this thing was in space in a matter of seconds. This was a decade ago.

a reply to: Wgeorge666

What location you were at? Did it make any sound? What makes you think it was unmanned?

Could you provide any details?
Cheers!

a reply to: SpeedFanatic

Sacramento ca. Was on flight path of McClellan afb. No sound. Both times ive seen it was after midnight . no basis to know if manned or unmanned. But was amazing to see.

a reply to: Wgeorge666

Interesting.

We used to have an LAV hanger at McClellan around that timeframe.

Wonder if our former “colleagues” were “checking up” on us?