Jet Engine Ignition & Starting: Interconnectors 

Thanks man. Please share with us any stories you have.

Towards the end of my career, I joined the Olympus 593 service team, to provide in-service design support. One of my first tasks was to address a problem with the EGT 'spider', which was attached to the engine's exhaust annulus inner cone. I remember being sent up to LHR from Bristol with white paper overalls, to crawl up the jet pipe of a Concorde. I got really up close and personal with a very fast lady.

Thank you sir. Your comment means a lot to me.

This has been a recommendation in the operation manuals for aircraft jet engines since the 1950's.

In fact for a light jet I fly there is a max rear wind of 10kts when starting.

You talkin' to me? Who's "this guy" ?

Me too. I searched and can't find it. Maybe in Your Questions Answered. YT deleted my index.

I’m pretty sure I remember him discussing it too, maybe briefly, but I do recall.

I saw him do it on the video about Combuster Liners and Igniters

Just trying to help. If you really want to dig in your heels and resist using what is considered proper terminology in the industry today, I can't stop you.

I've already criticised AgentJayZ about this: twice here, and once before elsewhere. The term 'combustion chamber' was the proper terminology long before some American invented the word 'combustor': it's an American "slang" word that's now in common use in the industry, which I've used myself.

@@grahamj9101 As I wrote (and was deleted soon after by someone) "Po-tate-oh Po-tot-oh" to continue the pedantic theme let me add Toe-mate-oh toe-mot-oh.

Hey, Graham, I did not try to start an argument. And it does not really matter. I was and am slightly enjoying the diametric opposition between the Queen's own jet engine manufacturer, and the undisputed authority on the Queen's English: the Oxford dictionary. They do not agree, and I apologize for enjoying that. PS: Camilla is not a queen.

That was probably what is known as 'combustion rumble', which is a form of combustion instability. Now, if you want to experience it on a more modern airliner, try a flight on a Triple-Seven powered by GE90s. The whole aircraft rattles and vibrates for several seconds when the engines are started. In complete contrast, the Trent 800s are noticeably quieter on start-up.

There's an internal ridge at the middle of the sleeve, so it can't go far enough in either direction to expose the piston rings. Very perceptive question, especially from a madness maker.

Greatest

Nothing to balance. Each passage in the diffuser is about 10 inches in diameter, and air at 75 psi flows into it. The interconnectors are about 12 inches down stream.

There is horsehair stuffed into them and this resists clogging/provides food for the engine

They can't get "too hot". They are exposed to flame for less than one second, then they are surrounded by air at up to 400F during flight. They are made of stainless steel.

The igniters are whoppers because jet fuel is like diesel. In normal air, it's pretty hard to get going. Even in a modern turbofan with 40 to 1 compression... that's at full rpm. At starting compression is basically none. Less than 1.5 to 1.

Flame does not move forward. If by turbines, you mean turbines, then yes for a brief few seconds when airflow is minimal during startup, some flame travels back and into the turbines, It clears up by the time idle rpm is reached. If, as many people do, you mean the compressor when you say turbines, then no.

@@AgentJayZ Right O , yeah , I was referring to the flaming through the rear turbine blades , mainly because looking into the exhaust from a distance , you don't see orange flame much . I would think the Gas Turbines interfere with alot of combustion thrust , but they are needed .

If the plane has taxied so you can see what you are seeing, the engine is running, and often the afterburner will light in segments. Normally in any aircraft engine built since the 1960s, you will not see anything when it starts up except heat waves.

You might be describing axial compressor and centrifugal compressor. But you're still messed up with your terminology, and in this field it's critical. A gas turbine engine can be a jet engine. A gas turbine is a part of a gas turbine engine, but if people are a bit lazy, they call a gas turbine engine a gas turbine. A turbine is a thing that uses high speed and high pressure gases to create mechanical rotating power, like a piston is used in a piston engine. Think about the difference between a piston, and a piston engine. Do those two terms mean the same thing, or different things?

@@AgentJayZ This is what I'm trying to clarify. To simplify. Is there a technical or designated name for each of these engines or are they considered the same "jet engines"? Jet engine with "combustion Chambers" versus a jet engine without combustion chamber's straight through shot path for the air so to speak.

I ask if your question is a troll, or some kind of joke. There are combustor outer cases, and combustor liners. Together they make up a tubular assembly known as the combustor. As pointed out in this very video, there is no part of the engine that forms a chamber. In answer to your question about what material is used to make a non-existent part of the engine, i will say: metal or metal like material.

@@AgentJayZ I understood that the technical them was inaccurate. But I was taught to call it a combustion chamber when I studied my ATPL. I've always since then wonder what material they could have been made of to be able to sustain such pressure and heat. I suppose we'd be talking more of an alloy rather than material. That's fine if you can't answer clearly, I'll keep on searching for my answer.

In the Navy in 1968, on the Pratt and Whitney J52, the term was "burner cans". 9 of them interconnected by flame tubes with 2 igniters. Thing change.

John, the combustor liners are stainless steel. The outer cases are made of steel. nothing too exotic, because the cases only touch compressor discharge air, which gets to about 400F max. The liners control the flow of that air, and use it so the flames don't actually touch anything. So the liners are exposed to 400F air, and also receive the radiant heat from the bright flames. If everything is working correctly, they don't get very hot.

@@johnstark8116 Early engines used stainless steel, but with increasing compressor delivery temperature and pressure, nickel alloys came into use. Check out Hastelloy X and C263 alloys.

Several videos on my channel under the heading of combustor liners. Search feature on my channel page.

Also try searching for cooling air

There is no fire suppression system on the engine. All fire extinguishing equipment is actually part of the airframe, and is there to protect the aircraft from being damaged by fire.

​@@AgentJayZ ok then could you do a video on that or can you only make ones about very specific jet engines "jet master"

For all practical purposes... for example on a pressure gauge, the pressure in the combustion section does not increase. But of course, air expands because it is of a higher pressure, but because there is no containment, that pressure rise is vanishingly small. Feel free to continue picking nits. It keeps us all honest.

@@AgentJayZ I do find this information relevant talking about interconnectors. My intend is not to nitpick, or blame you; I am a longtime viewer and appreciate what you do. I know you like to be precise with your words; I tried to understand myself and get to the ground of it.

@@AgentJayZ Unconstrained air expands because it is either heated or moves into an area of lower pressure. If air is heated while constrained in a constant volume, pressure will increase. If that air is allowed to escape through an orifice it will decrease in pressure, increase velocity, reduce temperature, and increase volume while converting the energy that produced the initial higher pressure state.

Sure. They are not chambers, but if you call them that, I will know what you mean. So we can communicate efficiently.

@@AgentJayZ If you look back, we’ve been here before, and I’ve previously expressed my irritation with your over your objection to the term ‘combustion chamber’. If you really need an authoritative statement, I’ve gone yet again into my copy of ‘Jet: The Story of a Pioneer’, by Frank Whittle, published in 1953. He uses the term combustion chamber exclusively and I have little doubt that he used the term when he was developing his engine in the late 1930s and early 1940s. As I’ve previously told you, and will reiterate, the term ‘combustion chamber’ was in common use long before I, let alone you, first laid a spanner (or wrench) on a jet engine. The term ‘combustion chamber’ was obviously in common use when the Orenda manual was written. It’s there on the pages that you’ve shown us in the past, and it was similarly in common use at Bristol Siddeley and Rolls-Royce in my early days as a designer. As I’ve already said, the term ‘combustor’ is a Johnny-Come-Lately Americanism and I’ve readily admitted elsewhere that I was seduced into using it in the 1970s, as was Rolls-Royce. If anything, ‘combustor’ is therefore the “slang” term, which has entered common usage in the industry. But then ‘OK’, originally a bit of American slang, is now in use almost universally. You appear to have become hung up on the notion that a ‘chamber’ has to be a totally enclosed volume. Why? There are numerous examples of its usage to define a walled volume with open entrances and exits. Looking at the word logically and critically, ‘combustor’ could reasonably be used to describe any device that supports combustion. Comparing it to similar word usage, it could even be applied to someone who promotes a combustion process: a synonym for ‘arsonist’, perhaps?

@@grahamj9101 Or an ignitor since it initiates combustion.

The gas generator is the whole engine, minus the jet accelerating nozzle. The industrial Orenda is the exact same engine, without the final tail cone, jet pipe, and nozzle. Instead it is attached to a straight duct which leads to a power turbine.

New to me. It's a 2007 R1200 G/S. It has 112,000km on it, and it rides and sounds like new. I finally put my money where my mouth is, because I've been saying for years that a well maintained bike engine will last basically forever.

Your question indicates that you do not understand your subject. What is called the LP turbine in a turbofan airliner engine... is called a power turbine in an industrial engine. Also, many industrial engines do not contain a power turbine, but function as gas generators connected via a short duct to a separate piece of equipment called a power turbine. I have a video about engine configurations that may help your understanding.

@@AgentJayZ Thanks, now I understand

@@mostafaibrahiemthat’s right, you don’t even understand your subject, loser.

Sometimes they do: Any turbofan engine has at least 2 turbine stages, or 3 for the big high bypass versions. One turbine is the compressor turbine, powering only the compressor. Larger turbofans (and some turbojets such as the Rolls-Royce / SNECMA Olympus) have both a low pressure compressor and a high pressure compressor, which spin at different speeds (for higher efficiency), so are powered by two separate turbine stages. The final turbine stage, furthest towards the back of the engine, is a free power turbine which is used to spin the big fan at the front of the engine, mechanically independent from the rest of the engine. This is equivalent to a power turbine bolted onto the back of an industrial gas turbine engine, which could be powering whatever the industry needs the power for, such as an electrical generator. Or in a marine environment where the power turbine is connected to the gearbox in a ship, ultimately powering the propeller to move the ship. An analogous situation is the turboprop engine on a plane, or a turboshaft engine on a helicopter: These too have a free power turbine, which is likewise mechanically independent from the rest of the engine, powering either a propeller or the rotor blades of a helicopter, albeit through a step-down gearbox because direct drive would spin the propeller or rotor way too fast.