The Audible Difference between Deflagration and Detonation

[afrolion44]

you say tomato I say potato

[dtiydr]

Dam..

[gcr100]

you need to put a hs camera in there

[Mathview]

The acoustic wave Power Spectrum P(f) would be a quantitative representation of this phenomenon, with f the frequency. Easy enough to obtain with a wide band acoustic pickup and ADC. FFTs and power spectral analysis gets P(f). The detonation signal should have a flat or flatter P(f) signature, at least that's what it sounds like to me.

[monimstarfox]

deflagration sounds like a 9mm

Detonation sounds like a .50

[displayfireworks1]

This is a great upload. You can hear why fireworks dont detonate as people believe.

[TheMarvelousMarw]

you can see the sonic barrier :=

[tomterahedrob]

Thank you!5*.Please keep this posted!How much more efficient, more thrust do you get with detonation as opposed to the deflagration?Did the measure it here?

[emb8]

Here there was about a 200% increase in thrust between deflagration and detonation. More fuel was used for the detonation, so that increase does not translate directly to an efficiency comparison. I think the current consensus is a PDE should be 10-20% more efficient than a turbojet.

[tomterahedrob]

Thanks for the great info you just cant find in any book.

[kiknet]

Have you measured what kind of detonation velocity these mixtures reach under PDE conditions?

[emb8]

The detonation wave itself travels down the tube at speeds between 1800 and 3000 m/s. The temperature can vary quite a bit, but the Mach number is usually around 5 for this engine. The blowdown flow behind the shock wave is often subsonic and would be accelerated using a nozzle for flight vehicles.

[archileach]

Hi emb8, both deflagration and detonation are irreversible processes, with respective subsonic and supersonic effects. Therefore detonation seems suited only for open propulsion systems because of the powerful wave energy developed. Removing the wave from the equation, wouldn't deflagration give a higher uniform pressure?

[archileach]

BTW, my point on this is to theorize that in an I.C. engine, detonation could never be harnessed because of the destructive force of the wave on the mechanical components of the engine. And if the mixture was diluted to the point that the pressure wave could be absorbed, the remaining pressure would be weaker than deflagration in driving the piston. Does this sound right?

[emb8]

Building an engine that can withstand the force of a powerful detonation wave is difficult, but not impossible. There is some current research with an air-breathing PDE demonstrator. I don't think there has been much work on an internal detonation engine for ground vehicles - maybe a good topic for research. Just in my opinion I think the wave could be harnessed with a stainless steel block and a robust cooling system. It can be more fuel efficient, but very noisy I suppose.

[crazykb]

Have you ever heard of the 'donut on a rope contrails?. Would this be the type of engine that would creat those types of contrails? Have you ever heard of the 'Auroa project'?

[emb8]

I've heard of them and I suppose that a PDE may be able to form them in flight. However, I think there are other factors (atmospheric, etc.) that can form these contrails with a typical turbofan or ramjet engine. I very much doubt that the Aurora, whether it exists or not, was a PDE or any type of pulsed engine. Perhaps the donut on a rope contrails left by these secret aircraft simply mean that the engine has some stability problems.

[QuantumCarl]

No mang, see, the only PDE we've seen in action decided to explode but with the kind of budget that the navy and aerospace has it's not unfeasible that, since all they have to do is that, they could come up with a relatively working model.

[QuantumCarl]

First of all it's Project Aurora. And secondly that uses a PDE type and is seen in a lot of places probably due to the high speed. I think it's an unmanned project.

[crazykb]

Actually, when you look at the Aurora project some of the 'stories' claim that it uses technology that goes way beyond turbine driven technology. HAve you ever heard of the TR-3B?

[emb8]

The TR-3B reminds me of Project Pluto. Nuclear powered aircraft, in my opinion, are realizable with current technology (I have a publication that briefly covers this). However, it may not be very clean. In this current 'green' movement where SUVs are criticized for fuel consumption, imagine the reaction to high speed vehicles with radiation emissions. We barely pass resolutions for nuclear reactors that just sit on the ground, let alone ones that fly around.

[crazykb]

THe lore that I have read on the TR-3B has even claimed that it uses some type of 'anti-gravity' propulsion technology. I have a question for you, since we are talking about the TR-3B, what is your opion on UFO's. DO you think that the evidence is good enough to say that there have been bizzare crafts in the sky (seen by pilots for example)? Don't worry, I'm not a 'UFO nut'.

[emb8]

I really don't believe in any UFO's or bizzare crafts. I think most of this is attributed to science networks that use these concepts to increase TV ratings. I trust in the observations of airline pilots but all of this is probably from weather balloons, research aircraft, etc. I read a book on electrogravitics and was not impressed by it. The Coulomb force is interesting, but there is no 'free' energy associated with its use and it can't be utilized for full-scale aircraft propulsion systems.

[crazykb]

I have read books on pilots and UFO's. In North America pilots usally keep silent if they see a UFO (it can mean the end of your career).However,in places like Russia they are more open to the subject.There is a lot of good data form russian pilots.I also have a friend of the family(former pilot for the airforce flying the CF-18 Hornet for example).He saw a UFO once and says to this day that it had "incredible flight characteristcs"(his words).As Dr. Michio Kaku has stated: it makes you think.

[QuantumCarl]

What was the engine design?

[crazykb]

Anyway, enough about the UFO thing. What do you think is the 'next step' in aviation propulsion? Also, a question that me and my friends have been discussing is Mars. SO, I have question for you: do you think we should send people to Mars, or keep sending robots?

[emb8]

I think the the next step may be a propulsion system that can transition from low speed flight to hypersonic speeds. Scramjets work, but no feasible intermediate system has been developed yet that can bring a vehicle up to the speed where supersonic combustion can be initiated while holding any kind of appreciable efficiency. I hope people can be sent to Mars, but we need a reason to stay. Landing on the Moon was a 'demonstrator' mission with no other long-term goals, so we stopped going.

[crazykb]

Hey, thanks for the replys. One thing I wanted to comment on was the stress factor of the pilot. I mean you can only creat something thats in the realm of human tolerance. I wonder how future aircraft will combat the problem of inertial forces experienced by pilots. They will have to address this issue as the performance of aircraft increases. I agree, that it would be cool to send people to Mars. However, it is enormously expensive to do so. We have better places for our money here on Earth.

[emb8]

Human tolerance is certainly a major factor and the designs of modern fighter aircraft already have had to be reduced for pilots. As for the expense of Mars, keep the following in mind: the Apollo program cost about 90 billion dollars but the technological benefits more than made up for the cost. The advancement in integrated circuits alone may have been worth the 90 billion. I think a Mars program will have the same effect.

[crazykb]

I see where you are coming from for sure, dude. however, the trip to Mars has many factors not accouted for: the psychological impacts of long space missions,not to mention seeing Earth as a 'pale blue dot' (RIP Carl).Also,the impact to the human body (muscle and skeletal changes in lower gravitional fields, like on Mars).I would love to see us go there.however robots can do alot of good science for a fraction of the cost.BUt shit,I have to admit,that the 'star trek' in me wants to go.Engage...

[datzfast]

Apollo used 10 year old proven technology or it was not allowed to fly. so much for your propaganda.

[tomterahedrob]

I thought scramjets were more efficent (not ceratain)than turbojets in high Mach speeds.Isnt detonation the most efficient in lab tests as far as thrust and fuel consumption?

[emb8]

Depending on the fuel used, turbojets can theoretically operate up to about Mach 4-5. PDEs have roughly the same speed limit, but they are more efficient considering thrust and fuel consumption. As speed increases, turbojet efficiency will drop off considerably and ramjets/scramjets have to be used. A scramjet is the only air-breathing concept that is feasible past about Mach 7 right now.

[archileach]

Have you ever heard of the Bourke engine? A horizontally opposed four cylinder version of this offers a very balanced design that is ideal for studying the effects of detonation. Melvin Vaux, Russell Bourke's nephew, built and tested these with a 60 to 1 air-fuel ratio to achieve controlled detonation. Their primary problem is that they consistently fail to generate usable horsepower under a load.

[emb8]

I haven't heard of this until now, but if it operates based on auto-ignition then it should not be able to maintain pulsed detonation. Also, auto-ignition leads to high compression ratios, which results in low speeds. I have some doubts that pulsed detonation was achieved with this engine. It takes a great deal of sensor equipment to see if detonation is indeed occurring in a closed environment like that.

[crazykb]

Also, have you head about the newest cold fusion experiment? Apparently they created a large amount of heat from the collapse of a 'uniform water bubbles'. The same phenomenon that occurs from the cavitation effect (created by the propellers) on water by ships. I was listening to an interview with Dr. Michio kaku, in the interview he stated that if this technology bares fruit, we could be headed into a technological revoloution. Now, if that doesn't 'burst your bubble', I don't know what will.

[emb8]

The last update I heard about this indicated no helpful results. It has been a very competitive field of research. Unfortunately, it is not too uncommon lately that a researcher in a very competitive field will publish suspicious information or use classified information for an advantage. This is usually destructive for everyone in the field.

[emb8]

Above I should have said high compression leads to auto-ignition. Higher torque and efficiency are a result of the more compressed fluid doing more work. I doubt the Bourke engine concept will make good use of detonation, but many other engine concepts might for low speed vehicles that need a lot of torque (e.g., bulldozer, train).

[archileach]

The problem with an ICE utilizing denonation rather than deflagration, is that the product of detonation is a high pressure wave front. It's possible to make an engine that will withstand this by lowering the fuel content, but the available pressure after the wave front is too small to power the pistons as efficiently as that provided by deflagration. You get an engine with high rpm but with low HP and Torque. What you really want is low rpm and high torque.

[marmaladekamikaze]

That's some nice info, thanks friend, always wondered about that, Do you mind if I ask where you read that?

[DoctorAwesome]

Which it is both.

I can't wait to see one of these in full flight.

It'll hopfully put us into the upper SuperSonic speeds.

The only problem is once you hit a specific speed the G's make it impossible for manned flight.

So either UAV's or some kind of inertia machine that perhaps catches it so we don't feel it or creates a force equal to that affecting us and cancels it out...

[emb8]

The first PDE powered flight occurred a few months ago at the Mojave Spaceport. Manned flight should not be a problem because of the pulsed detonation aspect or the speed. Current theoretical studies show that the pulsed detonation process can be efficient until about Mach 5.

[tomterahedrob]

why mach 5?I thought pde were the most efficient of the jet engines.

[emb8]

In terms of specific impulse, a hydrogen-fueled PDE is theoretically more efficient than turbojets and ramjets at high speeds. It is limited to around Mach 5 because of pressure issues. Basically, the detonation has a maximum pressure limit, and the compressed air from the inlet system around Mach 5 is in the range of that pressure limit for current fuels so no net thrust is created. A lot of people have been working on hybrid engines transitioning from a PDE to something for higher speeds.

[tomterahedrob]

thanks!this is very usefull info.keep up this cutting edge stuff.Ive looked for years for this info.

[QuantumCarl]

But what could possibly work for those higher speeds short of needing a huge breakthrough in Physics?

[emb8]

The scramjet engine should work well past Mach 6 all the way to transatmospheric speeds. Many more improvements in control and aerothermodynamics may be needed for long-duration manned vehicles at these speeds. However, there are many desirable unmanned applications (e.g., high speed missiles) that can fuel the development of this technology.

[QuantumCarl]

I wonder what this could mean when it comes to space travel...

[Malk007]

amazing!