Pulsed detonation engine

[seruriermarshal]

I found a news about Long E-Z used Pulsed detonation engine from Air force website , and found a Comment :

12/7/2009 10:45:37 AM ET
Ten years ago this month on Dec. 18, 1999, a pulse detonation engine-equipped SST flew over Arizona on it's way to Southern California. The airframe of this SST, still unnamed officially, was remarkably similar to the museum's XB-70 supersonic bomber ca.1965. Evidently museums may have to wait for sometime to update the accuracy of their historic flights data set until certain programs are declassified.
Bill Lohmeier, Tucson Arizona

http://www.af.mil/news/story.asp?id=123099095

???

 

[Lauge]

Ten years ago this month on Dec. 18, 1999, a pulse detonation engine-equipped SST flew over Arizona on it's way to Southern California. The airframe of this SST, still unnamed officially, was remarkably similar to the museum's XB-70 supersonic bomber ca.1965. Evidently museums may have to wait for sometime to update the accuracy of their historic flights data set until certain programs are declassified.
Bill Lohmeier, Tucson Arizona

Is there any particular reason to believe that "Bill Lohmeier" has any inside knowledge that the rest of us don't? "Some guy wrote this in a comment to an article on www.af.mil" is not exactly the most cast-iron solid of sources.......

Cue video of Ma Nielsens boy raising the BS flag.

Regards & all,

Thomas L. Nielsen
Luxembourg

 

[Nik]

Uh, I'd suggest that some-one noted PDE's potential for hypersonic propulsion and assumed that any test vehicle would, of course, explore that end of the envelope...

( Remember that inter-war Russian biplane with the ramjets on its wings ?? )

In mitigation, most things 'Rutan' do look as if they're 'flying', whatever their air-speed....

 

[tequilashooter]

https://www.researchgate.net/publication/318470797_MATEMATICESKOE_I_KOMPUTERNOE_MODELIROVANIE_GORENIA_I_DETONACII_PODKRITICESKIM_STRIMERNYM_RAZRADOM

https://ntv.ifmo.ru/file/article/14542.pdf

Scientific and Technical Bulletin of Information Technologies, Mechanics and Optics,
2016, Volume 16, No. 1 4

The main problem at supersonic speeds is the increased specific fuel consumption. The takeoff weight of an aircraft at supersonic speeds (Mach number M> 1) is a power law function of the flight range, i.e. fuel reserve grows nonlinearly with increasing range. That is why the SPS-2 (Tu-244), designed for an intercontinental flight range, makes sense to design for a significantly greater passenger capacity than the Tu-144, otherwise the plane will carry itself and fuel, and not a payload.

At supersonic speeds, wave drag is added to the friction and pressure drag. If at subsonic speeds the perturbations created by the body of the aircraft are concentrated near its surface (inside the boundary layer and within a certain distance at which the pressure waves decay), then at supersonic speeds the picture is different. The shock waves generated by the aircraft are damped relatively weakly and can propagate for many kilometers, reaching the Earth's surface. Behind the front of these shock waves, the direction and magnitude of the velocity vector changes, and, accordingly, the gas momentum. The force of resistance, as is known, due to the laws of conservation, is equal to a change in momentum, therefore the resistance created by the shock waves is very high, since the mass of air involved in movement is large.

However, this does not mean that a supersonic aircraft with an equal fuel reserve with a subsonic aircraft must necessarily have a shorter range.

The flight range is determined by the Breguet formula

L = 1062 (KM / Ce) ln (G1 / G2), where K - aerodynamic quality; M is the Mach number; Ce is the coefficient of specific fuel consumption; G1 is the initial weight of the aircraft; G2 is the final weight of the aircraft. Several important conclusions can be drawn from this. The range is directly proportional to the speed, i.e. a supersonic aircraft with the same range as a subsonic aircraft may have a lower aerodynamic quality. The flight range is determined by the product KM. For the Tu-144, it is about 17.6 at M = 2.2, which is more than that of modern subsonic airliners (KM ~ 16). The Tu-244 was supposed to have an aerodynamic quality of about 9.5 at M = 2.2. Why, then, today are not considered at all ATP, calculated at a flight speed in the region of M = 2, and are immediately studied hypersonic projects with flight speeds M = 5-6?

It's all about the specific fuel consumption. For subsonic aircraft, Ce ~ 0.7 , for supersonic aircraft , Ce ~ 1.1. The reason is that the supersonic air flow at the inlet to the air intake must first be decelerated to subsonic speed, which is accompanied by losses, then compressed by a compressor, mixed with fuel in the combustion chamber, burned this mixture and accelerated the combustion products to a speed not less than the flight speed ... All these processes at M> 1 are accompanied by losses proportional to the flight speed. It is necessary to reduce Ce by 25%.

An engine with detonation combustion can have a specific consumption of Ce ~ 0.8 at M = 2.2. An ATP with such a power plant at a cruising speed of M = 2.2 will have a longer range than a subsonic aircraft. If we had such an engine at our disposal, the Tu-244 with a cruising speed of M = 2.2 would fly now.

Let us now consider the problems of designing a hypersonic transport aircraft designed for M = 4–5. A modern subsonic passenger aircraft has a KM / Ce ~ 22 complex , while an SPS-2 (M = 2.2) has KM / Ce ~ 19.5, i.e. with an equal supply of fuel, the range of the former will be greater. But at M = 5, a hypersonic aircraft already has KM / Ce ~ 21 . If we compare the transport performance, then the maximum it will be for a hypersonic aircraft, therefore hypersonic aircraft with traditional ramjet ramjet engines in the speed range M = 4-5 can be quite competitive due to the very high transport performance.

 

[publiusr]

Another paper

Detonation-based device for novel propulsion applications

Combustors that drive propulsion systems are often volumetric in nature, typically in the form of cylinders, and convert chemical to thermal and mechanical energy through oxidation of fuels. This deflagrating combustion approach is now beginning to be challenged by detonation-based combustion...

techxplore.com

Redirecting

 

[quellish]

The Air Force was apparently doing serious work on PDEs in the 1980s. In at least one document PDEs are referred to as "wave technology" engines.

From https://apps.dtic.mil/sti/tr/pdf/ADA180311.pdf

Fiscal Year 1988 Technical Objective Document (U), Air Force Wright Aeronautical Labs, March 1987, AFWAL-TR-87-2000