|
A pulse detonation engine, or "PDE", is a type of propulsion system that has the potential to be compact and powerful, and can operate from subsonic up to hypersonic speeds. To date, no practical PDE engine has been put into production, but several testbed engines have been built and one was successfully integrated into a low-speed demonstration aircraft in 2008. In theory the design can produce an engine with a burn efficiency higher than other designs, with fewer moving parts. The burn efficiency of PDE can exceed even turbojets and turbofans. However, the impossibility of including a bypass fan in a PDE (which increases the overall efficiency of turbofans above the theoretical maximum for no-bypass engine) restricts the competitiveness of PDE to applications where turbofans are impractical or impossible. Air propulsion is the act of moving an object through the air. ...
Boeing X-43 at Mach 7 In aerodynamics, hypersonic speeds are speeds that are highly supersonic. ...
Look up efficiency in Wiktionary, the free dictionary. ...
Concept All regular jet engines and most rocket engines operate on the deflagration of fuel, that is, the rapid but subsonic combustion of fuel. The pulse detonation engine is a concept currently in active development to create a jet engine that operates on the supersonic detonation of fuel. A log in a fire place. ...
Subsonic has two possible meanings: A speed lower than the speed of sound is called subsonic. ...
This article is about the chemical reaction combustion. ...
For other uses, see Fuel (disambiguation). ...
A weapons cache is detonated at the East River Range on Bagram Airfield, Afghanistan Detonation is a process of supersonic combustion in which a shock wave is propagated forward due to energy release in a reaction zone behind it. ...
The basic operation of the PDE is similar to that of the pulse jet engine; air is mixed with fuel to create a flammable mixture that is then ignited. The resulting combustion greatly increases the pressure of the mixture to approximately 100 atmospheres[1], which then expands through a nozzle for thrust. To ensure that the mixture exits to the rear, thereby pushing the aircraft forward, a series of shutters are used with careful tuning of the inlet to force the air to travel in one direction only through the engine. A pulse jet engine (or pulsejet) is a very simple form of internal combustion engine wherein the combustion occurs in pulses and the propulsive effort is a jet; a reaction to the rearward flow of hot gases. ...
The main difference between a PDE and a traditional pulsejet is that the mixture does not undergo subsonic combustion but instead, supersonic detonation. In the PDE, the oxygen and fuel combination process is supersonic, effectively an explosion instead of burning. The other difference is that the shutters are replaced by more sophisticated valves. In some PDE designs from General Electric, the shutters are even removed because the process can be controlled by timing on the periodic sudden pressure drops that occur after each shock wave when the "combustion" products have been ejected in one shot. This article is about the chemical element and its most stable form, or dioxygen. ...
For other uses, see Fuel (disambiguation). ...
“GE†redirects here. ...
The main side effect of the change in cycle is that the PDE is considerably more efficient. In the pulsejet the combustion pushes a considerable amount of the fuel/air mix (the charge) out the rear of the engine before it has had a chance to burn (thus the trail of flame seen on the V-1 flying bomb), and even while inside the engine the mixture's volume is continually changing, an inefficient way to burn fuel. In contrast the PDE deliberately uses a high-speed combustion process that burns all of the charge while it is still inside the engine at a constant volume. This increases the burn efficiency, i.e. the amount of heat produced per unit of fuel, above any other engines, although conversion of that energy into thrust remains inefficient. The V-1 (German: Vergeltungswaffe 1) was the first guided missile used in war and the forerunner of todays cruise missile. ...
Another side effect, not yet demonstrated in practical use, is the cycle time. A traditional pulsejet tops out at about 250 pulses per second, but the aim of the PDE is thousands of pulses per second, so fast that it is basically continual from an engineering perspective. This should help smooth out the otherwise highly vibrational pulsejet engine -- many small pulses will create less volume than a smaller number of larger ones for the same net thrust. Unfortunately, detonations are many times louder than deflagrations.
The major difficulty with a pulse detonation engine is starting the detonation. While it is possible to start a detonation directly with a large spark, the amount of energy input is very large and is not practical for an engine. The typical solution is to use a Deflagration-to-Detonation Transition (DDT) - that is, start a high-energy deflagration, and have it accelerate down a tube to the point where it becomes fast enough to become a detonation. Alternatively the detonation can be sent around a circle and valves ensure that only the highest peak power can leak into exhaust.
This process is far more complicated than it sounds, due to the resistance the advancing wavefront encounters (similar to wave drag). DDTs occur far more readily if there are obstacles in the tube. The most widely used is the "Shchelkin spiral", which is designed to create the most useful eddies with the least resistance to the moving fuel/air/exhaust mixture. The eddies lead to the flame separating into multiple fronts, some of which go backwards and collide with other fronts, and then accelerate into fronts ahead of them. Wave drag is an aerodynamics term that refers to a sudden and very powerful form of drag that appears on aircraft flying at high-subsonic speeds. ...
The behavior is difficult to model and to predict, and research is ongoing. As with conventional pulsejets, there are two main types of designs: valved and valveless. Designs with valves encounter the same difficult-to-resolve wear issues encountered with their pulsejet equivalents. Valveless designs typically rely on abnormalities in the air flow to ensure a one-way flow, and are very hard to achieve a regular DDT in.
NASA maintains a research program on the PDE, which is aimed at high-speed, about mach 5, civilian transport systems. However most PDE research is military in nature, as the engine could be used to develop a new generation of high-speed, long-range reconnaissance aircraft that would fly high enough to be out of range of any current anti-aircraft defenses, while offering range considerably greater than the SR-71, which required a massive tanker support fleet to use in operation. (See Aurora aircraft) NASA Logo Listen to this article · (info) This audio file was created from the revision dated 2005-09-01, and does not reflect subsequent edits to the article. ...
An F/A-18 Hornet breaking the sound barrier. ...
A military aircraft used for monitoring enemy activity, usually carrying no armament. ...
The Lockheed SR-71, unofficially known as the Blackbird, is a long-range, advanced, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft by Lockheeds Skunk works, which was also responsible for the U-2 and many other advanced aircraft. ...
Aurora (also credited as the SR-91 Aurora) is the popular name for a hypothesised American reconnaissance aircraft, believed by some to be capable of hypersonic flight at speeds of Mach 5+. According to the hypothesis, the Aurora was developed in the 1980s or 1990s as a replacement for the...
While most research is on the high speed regime, newer designs with much higher pulse rates in the hundreds of thousands appear to work well even at subsonic speeds. Whereas traditional engine designs always include tradeoffs that limit them to a "best speed" range, the PDE appears to outperform them at all speeds. Both Pratt & Whitney and General Electric now have active PDE research programs in an attempt to commercialize the designs. Pratt & Whitney is an American aircraft engine manufacturer whose products are widely used in both civil and military aircraft. ...
“GE†redirects here. ...
Key difficulties in pulse detonation engines are achieving DDT without requiring a tube long enough to make it impractical and drag-imposing on the aircraft; reducing the noise (often described as sounding like a jackhammer); and damping the severe vibration caused by the operation of the engine.
First PDE powered flight The first flight of an aircraft powered by a pulse detonation engine took place at the Mojave Air & Space Port on January 31, 2008.[2] The project was developed by the Air Force Research Laboratory and Innovative Scientific Solutions, Inc. The aircraft selected for the flight was a heavily modified Scaled Composites Long-EZ. The engine consisted of four tubes producing pulse detonations at a frequency of 80 Hz, creating up to 200 pounds of thrust. Many fuels were considered and tested by the engine developers in recent years, but a refined Octane was used for this flight. A small rocket system was used to assist the liftoff of the Long-EZ, but the PDE operated under its own power for 10 seconds at an altitude of approximately 100 feet. Obviously, this flight took place at a low speed whereas the appeal of the PDE engine concept lies more at high speeds, but the demonstration showed that a PDE can be integrated into an aircraft frame without experiencing structural problems from the 195-200 dB detonation waves. No more flights are planned for the modified Long-EZ, but the success is likely to fuel more funding for PDE research. The United States Air Force Research Laboratory with headquarters at Wright-Patterson Air Force Base, Ohio, was created in October 1997. ...
Scaled Composites (often abbreviated as Scaled), formerly the Rutan Aircraft Factory, is located at the Mojave Spaceport, Mojave, California, United States and is headed by aircraft designer Burt Rutan. ...
Long-EZ belonging to NOAA The Rutan Model 61 Long-EZ is a homebuilt aircraft with a canard layout designed by Burt Rutans Rutan Aircraft Factory. ...
For other uses, see Octane (disambiguation). ...
In science fiction - In the movie Stealth (2005), the advanced fighters use pulse detonation engines with scramjet boosters.
- In the drama television series JAG, the Season Nine episode "The One That Got Away" (original air date October 17, 2003) features the Aurora — which, in the show is a super-secret hypersonic aircraft under development by the CIA, that uses a pulse detonation engine.
- The PDE has been used as a story point in a number of modern novels such as Dan Brown's thriller, Deception Point (the second page of the book states that all technologies in the story are non-fictional and exist, no sources are listed but it's there), and Victor Koman's science fiction polemic, Kings of the High Frontier.
- In X-COM, the Interceptor is equipped with a PDE, however even this huge propulsion force is inferior compared to the alien Gravity Wave Engines.
Stealth is a 2005 action/adventure thriller starring Josh Lucas, Jessica Biel and Jamie Foxx. ...
X-43A with scramjet attached to the underside at Mach 7 A scramjet (supersonic combustion ramjet) is a variation of a ramjet with the key difference being that the flow in the combustor is supersonic. ...
For other uses, see JAG (disambiguation). ...
This is a list of episodes from all ten seasons of the television series JAG along with the original airdate, locations and relevant themes & issues. ...
Aurora (also credited as the SR-91 Aurora) is the popular name for a hypothesised American reconnaissance aircraft, believed by some to be capable of hypersonic flight at speeds of Mach 5+. According to the hypothesis, the Aurora was developed in the 1980s or 1990s as a replacement for the...
Boeing X-43 at Mach 7 In aerodynamics, hypersonic speeds are speeds that are highly supersonic. ...
Flying machine redirects here. ...
The CIA Seal The Central Intelligence Agency (CIA) is an American intelligence agency, responsible for obtaining and analyzing information about foreign governments, corporations, and individuals, and reporting such information to the various branches of the U.S. Government. ...
This article is about the writer. ...
Deception Point book cover Deception Point (2001) is a thriller novel by Dan Brown, the author of The Da Vinci Code, Angels and Demons, and Digital Fortress. ...
Victor Koman, three time winner of the Prometheus Award, is a science fiction and fantasy writer, mainly popular in the libertarian community. ...
Kings of the High Frontier is a hard science fiction novel by Victor Koman, first published (electronically) in 1996. ...
X-COM is a series of computer games, started by MicroProse in 1993. ...
Notes - ^ Pulse Detonation Engines (interview) An interview with Dr John Hoke, head researcher from Innovative Scientific Solutions Incorporated PDE program under contract to the United States Air Force Research Laboratory (broadcast on New Zealand radio, 14th April 2007)
- ^ Norris, G., "Pulse Power: Pulse Detonation Engine-powered Flight Demonstration Marks Milestone in Mojave," Aviation Week & Space Technology, Vol. 168, No. 7, 2008, pp. 60.
See also Nuclear pulse propulsion An artists conception of the Orion basic spacecraft, powered by nuclear pulse propulsion. ...
External links |
Feeds |
Contact