Talk:Ramjet

Great new graphic, but

The new graphic is great but it couldnt be hello good samaratin in two ways. 1) it lacks a flameholder, usually just drawn as a zigzag line. 2) Most importantly, the design shown is supersonic, therefore it needs a converging-diverging exhaust nozzle to induce supersonic exhaust.

Finally, a subsonic rendition would be nice, with simple diverging intake diffuser and converging exhaust

Comment 2) is not strictly true! Even a convergent nozzle can generate a supersonic exhaust plume. The gross thrust is calculated at the throat as follows:

Fg = w.Vj/g +Aj(pj-pamb)

The first term is the momentum thrust, which generates the bulk of the thrust, whereas the second term is the residual pressure thrust. Ideally, a convergent-divergent nozzle will expand the flow so that there is zero pressure thrust (i.e pj=pamb) and all of the thrust is from the momentum term. Depending on nozzle pressure ratio, a con-di nozzle produces more thrust than the corresponding convergent unit. On a rocket motor the advantage is very large, because of the high nozzle pressure ratio. The advantage on a turbojet/turbofan is usually marginal, because nozzle pressure ratios are quite low. Ramjets are somewhere in between. :) Burbank 17.09 January 9 2006 (UTC)

The picture of the "low speed Ramjet" is worthless. That is NOT a ramjet. It's more of a space heater than anything else. A ramjet produces thrust, while theirs does not. It does not operate like a ramjet in any sense of the word. I removed the picture of it since it is misleading and doesn't contribute anything to an article about ramjets. Maybe it will be useful in an article about space heaters.

Youtube

Put this link to the article? http://www.youtube.com/watch?v=duHJjcMAoWM&feature=related 84.56.62.55 (talk) 10:46, 22 February 2008 (UTC)

No. Random YouTube videos don't usually go in articles as reliable sources. The view count looks sus 🙄 184.69.159.242 (talk) 02:24, 6 February 2022 (UTC)

Just saying, that comment is a decade and a half old :P Captain Jack Sparrow (talk) 17:10, 9 February 2022 (UTC)

Priciple of operation

I am wondering how the forward thrust results in detail. Naively looking one could assume that the combustion generates thrust symmetrically forward through the outlet and backward through the inlet which compensate themselves to zero. Can someone explain where the mistake is in this idea? I assume hat has something to do with requirement for preexisting forward speed and the asymmetries in geometry of the chamber, but how does it work in detail? I think somewould who knows should add an explanation of the priciple of operation to the article. 141.58.5.24 (talk) 10:00, 16 August 2010 (UTC)

The illustrations are somewhat misleading. Consider a simple ramjet design with no central diffuser. As the air expands (the cross-section of the inlet, internally, is increasing from front to back) coming in the front, its pressure increases, due to the Bernoulli effect. This pressure is unbalanced: it has a forward vector component against the forward inside of the inlet, but the empty space toward the back of the ramjet offers no resistance. A well-designed exit-geometry will increase the exhaust gas velocity, while decreasing its pressure progressively. This means, overall, that there is a net decrease in gas pressure from front to back (and logically a net increase in pressure from back to front), and thus the unbalanced forward-vector is maintained, and actually increases the faster the thing goes.

For more complicated designs, the matter takes some rethinking, but the key to where the reaction force actually occurs is the same: where is/are cross-sections which can take a front-ward pressure vector component? Will that component always be greater than any surface getting a back-ward vector component? The answer is 'yes', but as the article says, ramjets are rather inefficient at low speeds: the balance of forces is not really very much in the front-ward's favor JohndanR (talk) 15:29, 30 May 2016 (UTC)

Stechkin

Article needs more information about Stechkin, who worked out the theory of the ramjet with compressible fluid flow and supersonic flow. That work was widely acclaimed at the time, and prompted Crocco's famous paper on "Superaviation". DonPMitchell (talk) 06:37, 18 April 2013 (UTC)

J58 deleted - not a ramjet

The J58 at M3.2 is classified in authoritative sources as an afterburning turbojet (http://www.enginehistory.org/Convention/2013/SR-71PropulsionSystem-2013.pdf) or a turbojet with bleed air recovery (US Patent 3,344,606) or a turbojet with afterburner and compressor bleed bypass at high Mach (Flight Manual)

I have deleted the J58 from this ramjet article as I believe the statement "act as turbojet-assisted ramjets at high speeds (Mach 3.2)" is misleading and unhelpful without some explanation of how and why which of necessity would be a somewhat personal viewpoint, perhaps only for the serious thinker.User:Pieter1963|Pieter1963]] (talk) 21:33, 2 March 2014 (UTC)

Since the J58 (in SR-71) is often described as operating like a ramjet - it might be worth saying briefly why it is not considered a ramjet (eg. not all the compressor stages are bypassed, the turbine always operates ...) ? - Rod57 (talk) 17:41, 22 October 2019 (UTC)

Let me try that. "is often described as operating like a ramjet" Do you have any examples? Cheers.Pieter1963 (talk) 20:48, 14 June 2020 (UTC)

The problem with the ramjet association is that the author may be delusional or insightful. Since they rarely explain why they use the term you don't know which they are.Pieter1963 (talk) 22:26, 14 June 2020 (UTC)

Added explanation.Pieter1963 (talk) 21:12, 18 June 2020 (UTC)

Article style / layout / table of contents

I rate this as a below average article for Wikipedia. look at the table of contents - then overall the article. Mixed in are some short paragraphs/ phrases tha read like they might be section headers- but are not marked as such in per table of contents. Also look at the structure of the table of contents, use of subsections. Content on its own for the article seems pretty good but headings/ structure gives article a poor feel. Wfoj3 (talk) 20:46, 13 May 2017 (UTC)

Layout of history section

History section is mainly split by nation. It might be more helpful to organise it chronologically ? Any reason not to ? - Rod57 (talk) 18:20, 22 October 2019 (UTC)

Name

Nowhere is it stated where the name comes from. Neutron Jack (talk) 02:08, 11 July 2017 (UTC)

Old source on flame stabilisation in subsonic ramjets

CAN-TYPE COMBUSTOR DESIGN FOR A LOW COST SUBSONIC RAMJET ENGINE may be a useful source re subsonic ramjets. - Rod57 (talk) 19:02, 2 September 2019 (UTC)

Convert lists into useful tables

The two sections : Aircraft using ramjets, and Missiles using ramjets could be easier to use if they were tables. But what columns to add ? Maybe dates, engines, ranges, max speed, and a comment (eg for launch method) ? - Rod57 (talk) 18:17, 22 October 2019 (UTC)

A Commons file used on this page or its Wikidata item has been nominated for deletion

The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:

• Albert Fono's ramjet-cannonball in 1915-hu.svg

Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 15:52, 26 February 2022 (UTC)