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Valveless pulsejet aircraft?

Bgray

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The valveless pulsejet (a pulsejet that does away with the valves needed to make the V1 style jets work) has been seen as a very promising technology by some advocates, mainly because it has literally no moving parts. Does anyone know if there's ever been any studies on using this technology for manned aircraft of any type?
 

Michel Van

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There were some attempt to build Valveless Pulsejet engines
but they were abandon do it disadvantage, to high fuel consumption or extrem Noise level for the lower trust and speed there produce compare to a Jet engine.

see this example
https://www.youtube.com/watch?v=qwuDkOB9Jik

https://www.youtube.com/watch?v=rbn8qvjjAW4

THEY ARE QUITE NOISY...
 

soapy

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The main issue with valveless systems is that the frontal cross section is so huge compared to almost anything else engine-wise. Of course, no-one has ever, as far as I know, turned two onto their sides and put them under a wing. The second issue is that they tend to melt themselves, but once moving the air cooling can stop that issue.
 

Maiwand1880

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Between 1946 and 1956 SNECMA developped a range of valveless pulse-jet engines (though not without a moving sleeve) of increasing thrust-levels : from Escopette (10 kgf) to AP-503 Écrevisse (30 to 50 kgf, designed for vertical flight for VTOL applications) via Tromblon, 22kgf. Designer was Jean Bertin of later fame (Aérotrain, Naviplane, V-STOVL aircraft and many other developments), under SNECMA chief-engineer Raymond Marchal. SFC was three-fold better the Fi-103's ("V1", FZG-76) Argus 109-014 / 109-44 (aka Maru Ka.10 and Ford PJ31). Like the Hiller-Lockwood PJ, they used the Kadenacy-effect. For test-flights, a SNECMA subsidiary, SEMIVIA (formerly Minié Aéronautique) modified two Arsenal SA.104 Emouchet gliders into pulse-jet powered light aircraft: cn 203, F-WGGG flew for the first time in December 1950 from Melun-Villaroche with two groups of two SNECMA Escopette 3340, piloted by Léon Gouel. Cn 224, F-WGGH flew later and until the end of 1951 with two groups of three Escopette. F-WGGG complete with its four PJs still exists and can bee seen in the very interesting SAFRAN museum in Melun-Villaroche.
 

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Grey Havoc

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From the old Himmelstürmer thread:
After coming across this topic today, I did a quick bit of research on the subject of small pulse jets.

Assuming for the moment that the Himmelstürmer did indeed use two small pulse jets, rather than two small low powered liquid fueled rockets, as some sources seem to suggest, there seems to be two main ways, based on the technology available at the time, that they could have approached the problem (based on the traditional pulse jet that is, see further below):

Pulse jet with aspiration-

In this type of pulse jet, the fuel is drawn into the engine through an atomizer by the air which enters through the intake. The main advantage of this is that it is very simple and requires no fuel pump or other ancillary equipment. It also doesn't require that much operator interaction (just turn on and off). Therefore it's the most likely approach to have been used with regards as to the (pulse jet based) Himmelstürmer. The three most likely fuels, IMHO, that might have been used by the Germans in this case are, in descending order of likelyhood, methanol, kerosene or diesel.


Pulse jet with injection-

Here, the fuel is sprayed directly into the combustion chamber where it then mixes with air that has already passed through the valves. This allows one to throttle the engine simply by varying the amount of fuel injected. The major downside is that it normally requires the use of a pressurized fuel system such as a bladder or pump. Given the available information on the Himmelstürmer, this would seem to be the least likely approach used, unless they went with a pressurized gas as the fuel (removing the need for a pump), and even then it's doubtful.


Now, there is a third possible approach that the designers could have gone with, that being the valveless (also known as a acoustic-type) pulse jet. However, while they can be quite compact, and easy to build, use and maintain, I'm not sure that fuel efficient valveless pulse jets were developed before the post-WWII era. Although, given the known operational requirements for the Himmelstürmer system, that might not have been a insurmountable problem in the eyes of the design team. For the moment though, I would tend towards the first approach described as being the most likely used.

Whichever approach they did use, one way they might have improved the jump performance of the Himmelstürmer is through the use of an augmenter placed in the pulse jets exhaust. This would improve both the amount of thrust produced as well as overall fuel efficiency. The major disadvantage of augmenters is that, beyond a certain point at higher speeds, the drag they produce can offset their advantages. On the other hand, at slower speeds (and/or in short hops!) augmenters can be very effective indeed. I'm not sure how advanced augmenter related research was in WWII Germany though.
Just for informational purposes;
Probably the best site for information and research on "home-made" and experimental jets, pulsejets, ramjets, and rockets
http://www.pulse-jets.com/

This page has a .pdf by Bruno Ogorelec that is probably one of the most comprehenive histories on the valveless pulse jet ever :)
http://www.pulse-jets.com/pulse3.htm

http://www.pulse-jets.com/pulse3.htm

It mentions that while the Argus company is arguably more well known for their valved-pulsejet design(s) used on the V-1, they had in fact been working on valveless pulsejets, specifically a variety of "Capped-Tube" pulsejet which would been ideal for a project such as this IF it could be made to work properly. However they were supposedly ordered to drop the valveless work and concentrate on improving the performance of the valved Argus engines.

I'll also note that Boeing proposed using "Capped-Tube" valveless-pulsejets in one of their (2004 IIRC) VTOL transport designs. (Which it seems has either just been 'rediscovered' or they are pitching it again: http://www.flightglobal.com/blogs/the-dewline/2011/07/video-boeings-all-new-advanced.html )

So while I'm at it I'll point out that the Bruno Ogorelec article also mentions that Messerschimtt in the early '70s had a program testing a valveless pulsejet that was designed to become a ramjet at higher speed. I can't seem to find a whole lot about it and when I wrote Bruno he found that the majority of his information on the project had become corrupted and last I heard he was also trying to regain the information he'd had.

I don't suppose anyone here knows anything? :)

Randy
A DARPA sponsored thesis paper from 2005 regarding work on a 15 centimeter class pulsejet engine: http://repository.lib.ncsu.edu/ir/bitstream/1840.16/1999/1/etd.pdf
 
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