Talk:Turbojet

Clarification request

For a time, some turbojet engine designs included the ability to inject water onto the engine to cool the exhaust in these cases. This was particularly notable because of the huge amounts of smoke that would pour out of the engine when it was turned on.

Is this "smoke" in fact steam formed due to the evaporation of injected of water onto the turbine blades, or was it smoke due to some other factor? --Abqwildcat 23:14, 26 Jul 2004 (UTC)

The Rolls-Royce Pegasus certainly still employs water cooling for use in the hover mode, this indeed limits the harrier's hovering endurance for as long as the supply of coolant water holds out. Emoscopes 08:31, 14 December 2005 (UTC)

Liquid injection was tried on the Power Jets W.1 in 1941 initially using ammonia before changing to water and then water/methanol. A system to trial the technique in the Gloster E.28/39 was devised but never fitted.

IIRC, the Pegasus only needs water injection when the Harrier is hovering at high weights.

Cooling the combustion gases slows down combustion, so there is incomplete combustion and smoke. Smoke is mostly partially burned hydrocarbons, or just carbons. Gah4 (talk) 00:15, 26 May 2022 (UTC)

References

Edit as to what actually causes thrust

Generally speaking, for aspirated engines at lower altitudes the previous statement holds true, but the mass of the fuel must also be considered. Regardless of whether we're talking rockets or jet engines, it's simply the change in momentum that either produces thrust, or creates a net drag. When considered as a system, including all the air drug forward by the aircraft, at a constant velocity, the net momentum of the total mass of air through with the jet, airplane, or helicopter flies through will have a net change in momentum along the direction of flight of zero, but will have a negative change in momentum along the verticle plane. It's than downward increase in momentum which holds the airplane up. —Preceding unsigned comment added by Mugaliens (talk • contribs) 20:26, 15 August 2006

ERROR IN ARTICLE

The article states that the ME-262 was Germany's first jet fighter. It actually was the HE-280. —Preceding unsigned comment added by 209.226.201.236 (talk • contribs) 18:51, 5 February 2007

Clarification needed

Please clarify the definitions of each term under "Net thrust". Fuzzform 02:10, 22 February 2007 (UTC)

The statement comparing the fuel expenditure of the Concorde to an aircraft using a turbofan is true, but misleading. The TSFC of the Olympus 593 on the Concorde was around 1.9 compared to around 1.1 for a General Electric CF-6 series. That is, the engine on the Concorde needed more fuel for the same amount of push per second as a turbofan. The statement on fuel per mile is true, since the Concorde was traveling twice as fast while doing this. However, the wing design is optimized for speed over lift, so it cannot carry as much weight. This is analogous to saying a Corvette is more efficient than a city bus. — Preceding unsigned comment added by Steven.i.davis (talk • contribs) 18:18, 23 July 2019 (UTC)

In-flight reverser deployment

The accidental deployment of a thrust reverser during flight is a dangerous event that can lead to loss of control and destruction of the aircraft.

It's nice to see that the Lauda B767 is remembered, but does in-flight reverser deployment happen often enough that a broad statement such as this is warranted, or might it be better if the Lauda incident was more directly acknowledged? 59.167.244.69 12:14, 19 June 2007 (UTC) PWA flight 314 crashed in Cranbrook, BC after touching down, they noticed a vehicle on the runway and went around. The left hand thrust reverser did not stow, and the aircraft rolled over and crashed. https://en.wikipedia.org/wiki/Pacific_Western_Airlines_Flight_314 — Preceding unsigned comment added by 204.101.240.26 (talk) 20:25, 2 December 2016 (UTC)

I don't think accidental thrust reverser deployments are common enough to be notable. Feel free to delete that line if you wish. Shreditor 00:01, 20 June 2007 (UTC)

Assessment

This is a nice article, pity it doesn't have inline citations and more references. --Colputt 17:31, 12 September 2007 (UTC)

Fonó's patent was the first

In this Article they state that Albert Fonó's patent was the first: Albert Fonó MarkMT42 (talk) 02:46, 14 November 2008 (UTC)

Soviet Work

Might be worth mentioning the work of Arkhip Mikhailovich Lyulka in the Soviet Union, in the late 1930s. His experimental jet engines figured prominantly in the History Channel's documentary on "Secret Russian Aircraft of World War II". His work was not given appopriate resources by the Soviets, who prefered rocket and ramjet technology in the 1930s. DonPMitchell (talk) 00:09, 7 July 2009 (UTC)

There is an interesting July 1945 Soviet report by Abramovich, assessing German turbojet technology, and also including stats on the Soviet jet engine built by Lyulka:

• Jumo 004 engine - 720 kg, 900 kgf thrust, 3800 hp, 8700 rpm
• BMV 003 engine - 620 kg, 800 kgf thrust, 3400 hp, 9500 rpm
• Heinkel S8a - 490 kg, 550 kgf thrust, 2300 hp, 12,500 rpm
• Lyulka's engine - 800 kg, 1650 kgf thrust, 7000 hp, 8500 rpm

DonPMitchell (talk) 16:31, 27 August 2009 (UTC)

RC model plane turbojets

There are "toy" jet engines available, eg Jet Cat USA and Wren Turbines UK that develop between 5 and 50 lbs thrust, available in turbojet, turboprop and turboshaft configurations for radio controlled planes and helicopters. See a functional description here. Is it appropriate to mention these in the Jet Engine articles? Chalky (talk) 05:25, 14 January 2011 (UTC)

They deserve their own article, if you feel like it. I wouldn't put too much in here, as jets are relevant to miniature models, models are much less relevant to jets overall. We did at one time have coverage at Gas_turbine#Scale_jet_engines, but this has been eroded quite a bit from when I last saw it. Incidentally, there are gas turbine turboshafts out there as well as pure-thrust jets. There was a chap on the model jet builder's association stand at the Bristol model engineering show who had a turbine-electric loco chassis on display. Andy Dingley (talk) 09:49, 14 January 2011 (UTC)

Cycle improvements

How the heck can nozzle temperature remain the same whilst turbine temperature increases? The statement makes absolutely no sense! The purpose of increasing the compression ratio is to correspondingly increase the burn rate of the fuel... a higher compression ratio allows the engine to burn more fuel at any given time or to run more efficiency. Combustor inlet temps have little to do with nozzle temps, or even turbine temps for that matter - this is because combustor inlet temps are much, much lower than outlet temps and the net transfer is low. That said, compressed, pre-combusted air that's used to cool the nozzle, will invariably become less effective at higher temps. — Preceding unsigned comment added by 211.27.67.97 (talk) 07:46, 3 August 2012 (UTC)

Style

Currently trying to address "This article's tone or style may not reflect the encyclopedic tone used on Wikipedia".Pieter1963 (talk) 19:43, 17 March 2014 (UTC)

Review requested

Please review my attempt at improving the style as requested..with a view to removing the"style improvement" header.Pieter1963 (talk) 01:02, 18 March 2014 (UTC)

Difference from turbofan in language ordinary folks can understand ?

This is an encyclopedia, not a technojizzforum. So please can we have an explanation that folks without PhDs can understand, of the difference between turbofan and turbojet. Rcbutcher (talk) 07:46, 27 March 2014 (UTC)

Doesn't that mostly belong at jet engine? Even at turbofan, as the distinction is more important there. Here at turbojet though, this is simply the ur-jet and so needs less distinction from later variants.

To phrase it, I would try something like:

The turbofan is a development of the turbojet. Some of the air from the compressor is passed through the combustion chamber and used to drive the turbine. A portion of the compressed air is instead used directly for thrust. Most turbofans have large initial axial compressor stages that compress both air streams, then a smaller compressor that compresses the combustion air alone, to a higher pressure ratio.

This includes the essential points, but excludes those (like bypass ratio, twin shafts, or the use of a centrifugal second stage compressor) that are important in a turbofan article, but not defining of them overall. Andy Dingley (talk) 10:51, 27 March 2014 (UTC)

A turbofan is a modified turbojet that has a larger intake (in diameter) than a "regular" jet engine. The first few blade(s) on the engine blow air past and around the entire engine and act more or less as a propeller. That's why turbofans work better at slow speeds. Because they get more "bite" at lower RPMs. These folks will make anything sound complicated, but that's the .02 on turbofans. How much air goes around and how much goes through the engine is called the bypass ratio. (Sure, it's really more of a ducted fan than a straight propeller effect, the result is the same...) Air going around the engine and right out the back - just like a prop would do. Think of it as a mid-point between an turbojet and a turboprop. Cheers. 73.6.96.168 (talk) 16:56, 21 August 2020 (UTC)

File:Jet engine.svg

Hello! This is a note to let the editors of this article know that File:Jet engine.svg will be appearing as picture of the day on August 11, 2014. You can view and edit the POTD blurb at Template:POTD/2014-08-11. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page. Thanks! — Crisco 1492 (talk) 01:41, 20 July 2014 (UTC)

Picture of the day

A diagram of a typical turbojet engine. Air is compressed as it enters the engine, and is mixed with fuel that burns in the combustion section. Released through the exhaust, the resulting hot gases provide forward thrust and turn the turbines that drive the fan blades of the compressor.Diagram: Jeff Dahl

History

The article has the following quote-

"At the time of its design the turbojet was still seen as the optimum for cruising at twice the speed of sound despite the advantage of turbofans for lower speeds. For the Concorde less fuel was required to produce a given thrust for a mile at Mach 2.0 than a modern high-bypass turbofan such as General Electric CF6 at its Mach 0.86 optimum speed."

- This needs clarification. As it's written it suggests that the Concorde was more fuel efficient than a modern turbofan airliner. I can believe that Concorde achieved better mileage than a 747, for instance, but not that it achieved better passenger miles per gallon, which is what airlines are concerned with when choosing planes.

Confusion as to what is being claimed may arise because Concorde has been retired for some time now, and never had many passengers. A casual Wiki user might not know that a 747 seats four or five times the number that Concorde did. If indeed its passenger MPG was lower, then that's an amazing fact and should be cited. If it's simply a comparison of total fuel consumption, that's a bit like saying an old Chevy Corvette with a 7 liter engine uses less fuel per mile than a modern bus; it may be technically true, but is a bit misleading.

2602:306:39BC:1129:17F:F8C4:7F10:8739 (talk) 08:53, 11 August 2014 (UTC)

The quotation makes little sense to me. I agree it is most likely misleading. The paragraph is entirely unsourced so we can't check its accuracy. I will place a "citation needed" tag on it. If a suitable in-line citation doesn't turn up in a few days we are at liberty to remove the quotation. It can always be restored by someone who has sufficient information and a reliable published source to allow it to appear in the encyclopedia. Dolphin (t) 11:44, 11 August 2014 (UTC)

Concorde carried around 2.6 million passengers with BA alone, and around 2 million with Air France.

Airlines aren't only interested in 'passenger miles per-gallon' - they are interested in whether they can carry passengers at a profit. Concorde created over half a billion pounds profit for BA during its 27 years in service. That's around 25% of its yearly profits every year.

Concorde's Rolls-Royce/Snecma Olympus 593 engines were some of the most efficient engines of any kind ever made - and still are.

Concorde's fuel burn figures were 5 gal per-nautical mile at Mach 2, increasing to 45 gal per-nautical mile when on finals at 165 knots.[1] — Preceding unsigned comment added by 95.149.53.233 (talk) 11:48, 16 March 2016 (UTC)

BTW, Concorde's Olympus 593's ran at 100% dry power throughout the three-hour Mach 2 cruise, which is equivalent to a subsonic airliner's turbofans being required to be operated continuously at take-off power for the duration of the entire subsonic flight. The Olympus 593 did this every day without complaint for the entire 27 years the aircraft was in airline service. The first Olympus ran in 1950.— Preceding unsigned comment added by 95.149.53.180 (talk) 16:16, 6 March 2018 (UTC)

Power (electricity)

Turbojets seem to be used as backup in power plants. It is a cheap oil turbine easy to start and fast to connect to the network. (Engie Electrabel in Belgium in the news these days.) Is there literature on this in general? It would be then worth mentioning in the page. --Dominique Meeùs (talk) 07:18, 23 November 2018 (UTC)

The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust

The article says: The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. I would think that expansion would slow down the exhaust gases, not speed them up. Gah4 (talk) 00:19, 26 May 2022 (UTC)

The statement is correct. Exhaust gas enters the propelling nozzle at high pressure and exits at atmospheric pressure. This represents a substantial fall in pressure, causing the exhaust gas to exit at lower density and higher speed. The mass of gas leaving the nozzle in a given time must be the same as the mass of gas entering the nozzle in the same time. Dolphin (t) 22:06, 27 May 2022 (UTC)

No mention of engine noise

What does the noise depend on, thrust, rpm, exhaust velocity ... ? How is it controlled ? - Rod57 (talk) 12:10, 25 September 2022 (UTC)