Talk:Valveless pulsejet

Valveless pulsejet article

My main premises for taking the approach I did in writing the article were that a visual description of the engine was not sufficient and that what was really needed was communicating some idea of how the device actually works. This is not possible without the introduction of the underlying wave theory, though it is possible I think, at least at a basic level, to do so without going to a mathematical mode of description. The older article was inaccurate in several respects, and seemed to deal only with one design (Lockwood). I think one thing useful that could be added to this article would be a small graphic showing simple silhouette views of the engine types named (Lockwood, Ecrivesse, Escopette, Kentfield, "Chinese" and Thermojet) with small labels at the intake and tailpipe - they are all different beasts in shape and proportion and make an interesting visual grouping for comparison. However, I haven't studied the manuals enough yet to know how to properly upload and re-size such a drawing to make it fit the format properly. Any suggestions at all on improving this article would be welcomed. Many thanks to Ben Brockert for getting me through the fundamentals of Wikipedia publication!

We also really need an article on the topic of Kadenacy effect. - Larry Cottrill

A Valve is a Valve

Sic: "uses the mass of the air as a valve"... sigh. This article, and the Pulse jet engine article which duplicates much of its verbiage, employs a linguistic runaround. The problem is that a valveless pulsejet engine, like a ramjet, does not and cannot work at zero inlet speed. It's open at both ends, and everyone can see this. Such a phrase will produce in the lay reader the notion of using the "mass of the air as a valve" in all sorts of things -- plumbing, waterworks, flamethowers. It will take more effort to explain how the thing works, and this "easy" explanation will give rise to pseudoscience, which no engineer wants to have happen. --Sobolewski 14:30, 29 July 2006 (UTC)

A Valve is a Valve - and Air Makes a Perfectly Fine One

Sic, indeed. The problem is that Mr/Ms Sobolewski has never built, started or run a valveless pulsejet, nor apparently seen one started and run. The inertial mass of fluids, including air, HAS been used as a viable one-way valve in various devices - Louis Pasteur's beautiful invention that keeps bacteria out of wine while allowing fermentation gas to escape is a classic example (possibly of "plumbing" or "waterworks", albeit at a small scale). The phrase "does not and cannot work at zero inlet speed" is just ... wrong. I and dozens of other hobbyists throughout the world have built many different designs of successful valveless pulsejets, and we can run them statically as long as desired WITHOUT "force-feeding" air in any way -- forced air is ONLY needed for a few moments during startup of small engines. A valveless pulsejet is NOT a "defective ramjet" that needs outside help to keep air moving. Once running, all it needs is plenty of surrounding air (still OR in motion) and an uninterrupted supply of suitable fuel. "It's open at both ends, and everyone can see this." Absolutely - if you build your engine without a bend, you can look straight through it while it's running. But that doesn't keep it from developing usable thrust. There's no "pseudoscience" about a device that successfully burns fuel to produce propulsive power and keeps itself running. Larry 17:23, 18 October 2006 (UTC)

EDIT: Here are a couple of brief shots I posted on YouTube of a valveless pulsejet in action. I designed this one with twin rear-facing intakes. In the 'Starting' video, the use of the hand-held starting air gun is clearly seen. In the 'run' video, the engine is finally driven to flameout by excessive fuel flow:

Startup:

http://www.youtube.com/watch?v=E7oJW7rA14Q

Full power run and final flameout:

http://www.youtube.com/watch?v=ZpL2FF86Buw

Larry 18:45, 5 April 2007 (UTC)

A Valve is a Valve

It can be argued that all pulsejets use a valving effect. The valve is either Mechanical or Aerodynamic. The Dynajet is an example of a pulsejet that uses a mechanical valve to control induction flow. The Valveless (a misnomer) Pulsejet uses the energy (as derived from the momentum of high velocity and relatively high density air) in the induction gasses as they pass down a tuned induction pipe to provide a partial valve and a degree of confinement during combustion. During the cycle, pulsejets induce air from both ends of the duct so this argument can be extended. The Valved pulsejet uses a combination of mechanical valve and aerodynamic valve; the mechanical valve at the front (controlling induction) and an aerodynamic valve operating in the tailpipe. The valveless pulsejet uses aerodynamic valves at both ends of the duct.

So we now have partial confinement from both ends of the duct. This state exists for a short period during combustion and produces some degree of Constant Volume combustion! Graham C Williams (talk) 12:36, 8 January 2008 (UTC)

Merge

See the merge rationale on Talk: Pulse jet engine#Merge. Jumping cheese ^Cont@ct 10:49, 18 December 2006 (UTC)

Sucking air

A couple of questions I think could bear answering. What governs the amount of thrust produced? Which is more significant, pulse rate or engine diameter? TREKphiler ^{hit me ♠} 00:02, 12 September 2008 (UTC)

Jam jar jet question

Hi! I'm sort of new to this subject, so please excuse me if this has already been answered, but in the "jam jar jet" design, it seems like when the fuel vapor/air mixture above the fuel is ignited, the surface of the fuel will also be ignited, preventing fuel vapor from entering the area above the fuel, and potentially causing a big "boom". How is this prevented? 71.227.195.32 (talk) 05:37, 12 July 2009 (UTC)

Liquids don't explode, only volatile vapors. 70.233.93.179 (talk) 03:55, 2 September 2012 (UTC)

Jam jar jet: shameless self-promotion?

Currently, the article reads "Successful versions of the jam jar jet have been run by a New Zealand man (Mitchell Laughton) in a plastic bottle." This is laughable to me, in part because I discovered this phenomenon when I was 8 years old: open up a bottle of rubbing alcohol, and hold a lit match at the opening. If the level of the alcohol in the bottle is just right, it'll pulse. It would be good to get a citation for this, but Laughton's contribution here is hardly noteworthy. As such, I'm removing the reference to him. 70.233.93.179 (talk) 03:55, 2 September 2012 (UTC)

Numbers

It would be nice to have some numbers, for example

1. fuel efficiency compared to other types of jet engine
2. pollutants (nitrogen oxides, sulphur dioxide, unburned fuel, etc) —Preceding unsigned comment added by Specrat (talk • contribs) 02:41, 2 April 2010 (UTC)

Why does "resojet" redirect here?

Is it a synonym? Equinox (talk) 19:11, 12 November 2015 (UTC)

The resojet (resonant jet) was a US duplicate of the V1 pulse jet engine. http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19771238000  Stepho  talk  21:45, 12 November 2015 (UTC)

Typo in he first diagram.

There is a typo in the first diagram. Underpressure is misspelled as "Uderpressure" CrazyCat138 (talk) 18:01, 18 December 2023 (UTC)

And of course I misspell "the". How ironic CrazyCat138 (talk) 18:02, 18 December 2023 (UTC)

WP allows any editor to edit any page. We encourage you to fix it directly.  Stepho  talk  22:58, 18 December 2023 (UTC)