the Turbojet Start Sequence
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- Опубліковано 18 лют 2023
- Explained in detail the series of events that take place during the start of a turbojet engine from fully stopped to working in the flight regime. In our test cell, we have full manual control over the engine, so all these steps must be completed in the right order, and within narrow time windows to ensure a good start, and to avoid any damage to the engine.
This is a project completed in Summer of 2021 that was never used.
It's also a good follow up to my video called How to Start a Jet Engine. - Авто та транспорт
The twin V8 start cart used on the SR-71 might be the greatest method of starting a turbine engine ever.
Yes, I think they have one at the Boeing museum in Seattle. Sitting under the SR-71 parked there... that you can climb into.
@@AgentJayZ
Cool! They have a static display of the cart outside the AGE shop at Beale AFB.
Theres one at the AirZoo in Kalamazoo.
So the SR-71 is "technically" using the V8 engine to operate, yes?
In the exact same way that all groceries are based on diesel... yes.
I'm a diesel mechanic and over the last 10 years I have worked on steam turbines and screw compressors in a refinery.
I'm really fascinated by gas turbines and I just love your lectures. Thanks for your efforts they really clear up a lot of misconceptions I had. 👍🇿🇦
You are always so informative! I've been a diesel tech all my life and its always interesting to see how other systems work.
Internal combustion, internal combustion.
I may have said this before but you are truly a great teacher. You know your subject matter backwards and have great enthusiasm and if you love this stuff it’s magic. Thank you
Thanks again!
What a good instructor im so impressed . So good explanations. Thank you so much.
Thanks for a BRILLIANT technical run through, made simple enough that an enthusiast like me can follow. Very clear, and no questions about starting the things left 👍.
Cheers
Pete' New Zealand.
Loved the gloved hand in hot pot analogy.
Thank you. The video I’ve been looking for. So many google results are like “this fan compresses this gas which ignites that fuel and the exhaust turns this other turbine and then thrust happens. “ This video shows the details along with the maths and video to help people really understand what’s going on.
You might like the predecessor to this video. It's called How to start a Jet Engine.
Gotta say older jet engines startups are elegant to this day
Love these technical videos with actual numbers! The way a jet engine starts reminds me of the fan curve I set for my cpu overclock, which deals with temperature and rpm too, got to make sure the heat doesn't get ahead of the fans!
I worked for New England Tel & Tel in the 70's and we had a turbine in the central office to run a generator used to charge banks of batteries in the event that we lost power. It was about the size of a pickup truck , not as tall . That beast went from 0 rpm to 10k real quick . Glad I got to experience the maintenance test. On a side note we had fallout shelters in the building and I came across cases of bottled water that had labels with the word Poland ( Springs ). LOL well before the bottled water craze . I thought why do we have water from Poland?
Very good explanation, even I understood a lot of the starting process and why the different steps need to be done at a specific RPM. Thank you very much!
thanks, my dad started on merlins, p-80s f-86 t-33 f100 f101 f104 cf-5 13 years at cold lake instructing finish off with buffalos 1939 to 1969 RCAF thanks again
Great explanation, especially the bit about the cause of high egt at start.
Thanks! 👍
Everybody in Americas favorite Canadian Jet technician! 😝😝
Interesting video. I work with the electricity industry that uses heavy frame gas turbines (essentially very large jet engines) that turn the alternator that generates the electricity. However, the heat from the exhaust is also collected and turned into steam to turn another steam turbine to generate even more electricity. These so called combined cycle gas turbines are therefore very efficient BUT they take several hours to start as they have to heat up very slowly to prevent damaged to the turbine blades.
They can start quicker in open cycle mode (without the steam generator) but it would be an absolute dream to be able to start a power station combined cycle gas turbine as quickly as this jet engine.
I always used to wonder how much a full overhaul would cost
But being a piston engine mechanic, I knew man hours was a large part
of that, then I heard a J79 could be 700 hours to complete with testing
This was a good enough answer, I could never own a F4 Phantom that flew
A gave me a better understanding of why the rich fly L-39 with AI-25 turbo-fan engine
Fascinating stuff
Excellent Jay! Thank you. Rich.
Excuse my newbieness- I honestly expected those RPM numbers to be MUCH higher. Turbines SOUND fast. I guess in reality, you can only safely spin physically large things so quickly before vibrations and harmonics become a serious problem, despite precision balancing. I guess what I'm trying to say is that I learned more than I expected to, and I thank you for that.
Large Turbofan LP sections turn at 3500 or so.
The HP sections at 8 to 10 thousand.
Turbojets turn 7500 or so if they are big, and 12 or more if they are small.
APUs will turn at 30,000-ish
Starters maybe 38 to 45
The Allison 250 turns at 50 thousand.
RC toy engines at 150 thousand
Dentist drills are air turbine powered, and they go up to 250,000 rpm.
The pattern here is that smaller things can spin faster without breaking up. It's more about the material strength than the bearings.
Was F-15 mechanics and I remember these mystery hot starts... Very good description!
Agent JayZ,
Thank you for this - great explanation and very interesting!
Paul (in MA USA)
Excellent video, thank you for the explanations.
Great explanation!
Fascinating for this simple piston engine mechanic.
Ahh...yes...Ft.St.John. My old stomping grounds. Grandparents moved there back in the 40's. Hi to ya'll from CA!!
Great video sir. Thank you!
Excellent; thanks for sharing.
Great video, as always! Nice clip of the aircraft start!😀
Its very interesting when you compare the hydromechanical engine control.and the fadec/ digital engine control starting parameters. On the hydromech one there is a nice 5% N2 roll back and a nice peak Egt when the engine is stabilzing at idle after start. Its because of the mechanical governor takes over the control from the acceleration control. On the Fadec very hard to observe these roll back. And the peak Egt is also minimum. Digital fuel control can control transients very accurate.
Excellent video sir, thank you for sharing. 10/10 explanation
Thanks for the kind words.
Just casually says he works on gas turbine engines. In fact he overhauls friggin fighter jet engines.
It's like the president of a country saying he's just a CEO.
Every Friday, at our "safety meeting" I try to remind all the guys just how cool our jobs really are.
Far out man great video. 👍.
Great video. Thank you AgentJayZ.
Love the Channel!
Awesome, thank you!
Thank you and hope to see more. Going to need it when I get into turbines next year!
Super Cool Jay !
Done many starts and learned from this. Keep it up, Agent J.
Thanks and well done!!!
Really wished I could be there at this moment.. 😍
The start sequence of a gas turbine is my favourite sound
That and a Harrier RR Pegasus throttle back after landing
Watching this and some of the Everyday Astronauts how to start a space rocket engine is really fascinating. In some ways, a rocket engine is much more complicated and risky to start compared to a turbine engine. On top of that, some rocket engines literally do employ one or even two combusting turbine engines hooked directly into turbo pumps. Those engines tend to use some really exotic chemicals just to start them up. Needless to say, jet and chemical rocket engines are among the most complex to manufacture machines in existence employing some of the most exotic manufacturing systems.
I was reading a book on the development of liquid fueled rocket engines.
It described the stresses on components and fasteners similar to turbine engines... only ten times higher.
I bet rocket mechanics get paid at least double the millions I make, eh?
increible las cosas que me encuentro en youtube jajajaj cada dia mejor
nice start ... 30krpm approx at about 600c ... and around 60% rpm ... good point how the engine is at max stress during the start and not from idle onwards ... but then the engine is designed to work at this setting for extended periods because that is where it spends most of its time ... (there and OFF) ... I liken it to getting moving on a bike .. you got to peddle for a bit before the bike will stay upright and keep going ....
as for solo designing a jet engine ... mine is at the 3rd of 9 compressor stages .. and thats since the video you said it couldnt be done solo ... as I said it just takes longer ..
Saw a video on starting the SR71's J58 engines, which apparently required a pair of Buick V8 engines to start - that's a lot of HP to spool the engine up.
Agent Jay, can you do a video of turbine throttle up while focusing on the variable inlet guide vanes actuating?
I've made a few vids about that. I think one is even called VIGV's in action.
@@AgentJayZ yup, searching for that returns a few. After a bit of searching,
One with a running engine is 'Afterburning J79 test in the snow' at mid 13' mark.
There's a video somewhere of a British portable hand crank turboshaft generator. You can tell from their effort that avoiding over temping the turbine and guide vanes is critical. I'm thinking the ignition cut off was controlled by a centrifical mechanism.
Great stuff. I remember how much trouble it was to figure out how to start the AI-25 turbofan engine. I've been looking through the jet questions series, and I can't find info on what exactly what you look for and what you watch for when testing a jet engine. (Idling, throttling up and down, etc.) I have been watching for about 9 years but maybe you did a video on this and it slipped by me, or have you not yet done a video on this?
That AI series was really good.
Poor Orenda has a crooked nose. 🙂 Super video, JZ!
Designed that way to fit in the Sabre. The vid is called "Orenda 14 in the Sabre", or something real close to that.
The original RB211-22 engines produced a very long-lasting, low-pitch. What causes that loud hum when starting an L1011??
If the temperature in the cockpit reads about 800 degrees you will like the temperature in my wifes car.
I'm really glad this guy doesn't live next door
That would be you... living in an open grassland, next to a scrubby forest, next to a huge farm.
@@AgentJayZ yep
Thanks for sharing.
Goldy Locks zone of start speed/airflow for ignition.
hey!, i was wondering if you have ever worked on morden jet engines like the GE F110 or like the P&W F100?. also love your content ♥
The most modern engine I've worked on is the LM500, which is based on the TF34, used most famously in the A-10.
@@AgentJayZ thanks a lot!
If you have a change it would be nice to have subtitles on videos, it would help lot to understand better for foreign language peoples, but amazing content by aircraft mechanics student from finland
As I have said many times before, the autogenerated english subtitles are so inaccurate and misleading, they only add confusion. I can only imagine the subs in any other language are at least as bad.
No subtitles until they can actually help.
@@AgentJayZ okay👍
@AgentJayZ Did you make a freudian slip at time index 8:35. "You said the combustion of the fuel air mixture causes it to expand". Should that be "causes the velocity to increase"? Pressure gain combustion only exists in science fictions movies right ;-) The pressure drops in the combustion chamber which is how the cooling air flows through the dilution holes?
The reason the velocity increases is because the volume increases, because an uncontained mass of air, when heated... ... ... expands.
Eh?
J, does the shape of the nacelle enhance the inlet pressure. Like a wing?
A wing does not do that. There is no nacelle in this video. If you are talking about the starter fairing, it is shaped to fit the inlet duct in the aircraft. It's all explained in my video called the Orenda 14 in the Sabre.
If you are talking about the bell mouth inlet fairing, it helps to reduce the inlet pressure loss due to the fact the engine is stationary. Inlet pressure is almost restored to ambient when using a bell mouth.
It's kind of interesting thing that the highest load (thermal at least) on the parts are during start cycle whereas all Engine Manuals that I am aware of are limiting the components (life-limited components) by the Flight Cycles. So, you can start the engine how many times you want, yet, the if you do not put the engine in the air, you don't have to deduct the cycle from corresponding limit.
Nope. A startup is a cycle. Two short flights without a shutdown in between is one cycle.
@@AgentJayZ I disagree. I.e GE manual states that cycle is defined as a flight that consists of an acceleration to takeoff power, takeoff and landing. Regardless of if the engines are shutdown before the next takeoff.
A start and shutdown is also a cycle. Each engine manual uses different language, but industry standards are more generic. A hot start, if certain time limits are exceeded, is all of your cycles being used up all at once.
About the inlet guide vanes, these "black blades" before the guide vanes are for axis fixing purposes only? What is the effect on the flow?
The Orenda has six struts in front of the IGVs. The struts are structural, and locate the front bearing housing, along with a gearbox and starter input, at the center of the front frame. The struts are hollow, with passages for radial drive shafts, electrical cables, and oil lines. They are streamlined in profile, but I'm sure they create some loss of airflow. Airliner engines have been engineered with overhung fans, so there are no struts in front of them.
Do you guys balance non manufactured compressors/turbines? I have one I'm going to order and need it balanced but its not commercial sized. If not do you know where I can get it balanced?
Not sure what a non manufactured anything is, but we can balance just about anything. Many places that deal with fans or rotating equipment can balance machinery.
On a cartridge start, how is the start sequence compressed to a second or two? It seems to be too quick for manual changes during the procedure so are the igniters started before firing the cartridge and fuel injected at the same time the cartridge is fired? What % of RPM does a cartridge kick the engine up to to make sure it can continue to idle on its own?
We've never used a cartridge start, because they are military, unnecessary, and dangerous.
There's a vid of a cartridge start of an Avon in a Canberra bomber here:
ua-cam.com/video/Hz5-yM6fJ70/v-deo.html
It spins the engine quickly to min self sustain, or maybe a bit less, increasing the thermal stress, but lowering the already enormous mechanical stress placed on the engine. For the Avon, I don't know these numbers.
The F-4 Phantom 2 had J79-15s in it, and they had a cartridge start option. Min self sustain on a J79 is about 2300 rpm, after starting at 1300 rpm. Idle is at 5000 rpm.
Going from zero to around 2000 rpm in a second or two on a rotor that weighs about 1200 lbs is really hard on the starter drive through the main gearbox, so if any other method is starting is available...
@@AgentJayZ Yes, that must cause some stress. It's more like the start of a rocket engine and rocket engines generally are not started very many times although that is changing. The turbo pumps in a rocket engine look like small jet engines (I can lift one that generates 15 000 hp, the rotor is like a small dumbbell and each postage stamp-sized turbine blade generates as much power as a car engine). The gas generator used for the start has been described to me as similar to the one that inflates an airbag but bigger. 0 to 30 000 rpm or so in a few seconds.
Great video. Where is the EGT measured?
EGT is measured by thermocouples in the exhaust, usually just downstream of the turbine, but upstream of the accelerating jet nozzle.
Where does the kickstarter lever get stored?
Exactly where you are thinking...
There are multiple combustion chambers on the orenda jet engine, each with its own fuel and ignition. What happens if one or more combustion chambers fail to ignite?
They are not chambers, but there are six of them. There are not six ignitors. Only two, on combustor cases 2 and 5. Only one is really needed, and the other is just for redundancy.
The only way all six might not light is if there is something blocking flow to the fuel nozzle, or if the operators are not doing it right.
I don't think I've done a video on interconnectors, also known as crossfire tubes. I think it might be time!
Where is the temp sensor located?
Nice video!
Depends on the engine but either between two of the turbines or in the exhaust nozzle after the exhaust turbines.
Some engines e.g. the RB199 in the Tornado had an infrared optical pyrometer which measured and displayed the temperature of the HP turbine blades as Turbine Blade Temperature on the cockpit gauge. It also displayed Exhaust Gas Temperature or EGT on the same gauge from thermocouples in the jetpipe downstream of the LP turbine. If I remember correctly, during start EGT was displayed but over 80% NH (high-speed shaft rpm) the gauge changed to TBT.
Interestingly, the EGT was displayed as T7 on the gauge because they apparently were the same gauges used on Concorde for the RR Olympus engines.
Is the start cart automatic or manual it would be cool to see the procedure on it
Video called The Huffer
Would a hot start and wet start be the same thing? Lots of flames shooting out the exhaust at start-up?
Not necessarily, you can get a buildup of fuel that burns in the tailpipe on startup. The EGT may not be affected much, but you have what is known as a tailpipe fire... a definite non-emergency.
Or a rough, crude start, with lots of flames but no spike in EGT. The Orendas sometimes do that.
Or a totally normal fiery start, like with the J47.
A true hot start can happen without any flames coming out the back. It's the burning of fuel at too low an rpm, and the inability to accelerate up to idle. The engine just cooks itself to death due to insufficient cooling air, and that does not take a lot of fuel.
That's why the operator of pilot looks at only two things: rpm and EGT until idle is achieved.
@@AgentJayZ thanks
Thanks! Can you get a Ge90?
We do not work on commercial aviation engines. That is a modular engine, and could be shipped without the fan module. If there was an industrial version, it would not be equipped with a fan, and we could definitely work on it. If someone sends us one, I'll record the work and test.
Q. When landing in very cold conditions (e.g. North pole) they don’t shut off the engines, is that true of jet engines and if so why?
Turbine engines don't have the sliding friction of pistons in bores, so the oil can get cold and not cause problems. I think the service limit for synthetic jet oil is -65C. It's up to the discretion of the pilot, but as long as you have a way to turn the engine to starting rpm, you don't need to keep the oil warm by running the engine.
@@AgentJayZ cheers, makes sense
21:20 Why are variables on the screen so slow to update? It looks like it might miss the RPM value when you need to do something
The only noticeable lag is the EGT, and that is because exhaust gases are heating up metal parts. There is even more delay in the heating of the turbine blades, because they are much more substantial pieces of metal. We are measuring exhaust gas temperature, but what we are interested in knowing is the temperature of the metal parts in those gases,
So the spark plugs need to be changed in tens of hours of flight do you have to remove the engine to do that?
No, typically there is a way to access the ignitors (spark plugs) while the engine is installed.
There is no typically.
The Orenda in the Sabre: igniters inaccessible while intalled.
J79 in the Starfighter and Phantom II, inaccessible.
Only non-professionals call ignitors "spark plugs".
@@AgentJayZ well I am a non-professional. I've just always found Jets and engineering fascinating. I've never even been in a airplane before. Forgive us if we use the wrong jargon. A lot of us are average Joes I would assume and love your videos!
I'm a Jay Z also, but im no Agent!
this temp is jet peipe temprature,engine temprature or exhaust gas temp or turbine temp,,,,,at xhich place we measure temp
EGT can be measured in any of those places. It is used as an indicator of the temperature of the tubine nozzles and blades.
How does self sustaining speed work? Around the 9:02 mark.
It's the minimum engine rotor speed from which the power supplied by the turbine can accelerate the rotation. The starter is no longer needed, and the engine can increase the speed of rotation up to idle speed on its own.
Min self sustain is not idle, and if the engine stays at that speed for more than a few seconds, it will overheat and be damaged.
What sort of voltage do the ignitors need?
They get between 30 and 50 thousand volts
The igniters can run on almost any input voltage (at least modern ones, can't speak to older ones). The more voltage you give them the more frequently they produce the spark, they build up the voltage fed to them until they reach the amount specified for the spark.
@@ERIK31351 Many thanks for that info
Awesome, very informative! I love this channel haha
the thrust on the last engine test was that pounds of thrust or newtons ..
It's too low to be pounds and too high to be kilonewtons for this engine. It could be kNx10. Only Z knows.
@@damny0utoobe at idle it could be either
@@kaboom-zf2bl good call, looks like it isn't running max.
Our test cell measures thrust in lbs of force.
@@AgentJayZ now the tugh question seeing how beefy the stand is ... what is it's maximum rated load ... my guess would be upwards of 80,000 lbs of thrust
Came from the dropped in a turbine video
Man his voice changed alot from 12 years
Sounds the same to me!🤔
The quality of the recordings have gone up
Don't roast your cans.😆 Interesting.
Hope this is not a frustrating question what rpm is 100%
@@mikedupree832 From google: 7800
Each different engine has it's own max engine speed. The % system was created to make it easier to avoid difficulties, because different engine type run at different speeds.
The Orenda 14 is at 100% at 7800 rpm. The J79 at 7685. The LM2500 at 9200. The AI25 at 14,000
The RR250 at 50,900. The PT6 at 42,000.
@@AgentJayZ thanks for the information. I was thinking that the idle speeds would be close and the max speed different. Almost like automobile engines. Thanks for your
Around 420C at 69%RPM? Nice.
Agent Jay Zed..? Are you a Ham?
I think that would be cool, and really useful in one possible future... but I am already involved in too many activities that I don't do enough of.
I'm thinking of getting one and would probably be getting a handheld device soon so I can learn something. What's your call sign though?
Well, I'm trying to figure out how to make a mini bypass engine with an electric fan and an electric generator connected to the actual turbine // Electric Gear Ratio for the Fan😅
Glaaaarghhh. Word salad. Good luck figuring out what that even is, never mind building it.
えーじぇんじぇーずぃー
1st
Again! Nothin gets by you...
@AgentJayZ lol yeah I'm a big fan of you and your channel
and what is your aim to do this you provide big engine for giant plane company or for smaller sport plane? that are thousand way to go to...
I m still very clear with my direction but my idea worth put some money in.
If your ideas or designs have any value, the best people to decide that are the engine manufacturers.
are you engineer of jet engine factory or just a enthusiast guy？
I have some new idea on aviation engine, I have some potential investor
I m planing to do something, if you have not regulations that not allow you to cooperate with other people freely,
I have strong interest to contact you.
thanks
I run Jet City Turbines, where we carry out the overhaul of vintage turbojet engines for early fighter jets owned by private collector pilots.
I've heard from dozens of people claiming to have great new designs.
I have made a few videos about that subject. Here are two:
"So You Want to Design a Jet Engine"
and
Design and Build a Jet Engine Yourself?"
On my channel page there is a search bar, and you may find these vids interesting.
Hey, your idea sounds great. I know a bloke in Nigeria who is seeking help in moving large amounts of cash...maybe you could help each other...maybe meet up over some google translate training.