I used to work on the LM2500 engines in an FFG-7 class ship in the US Navy. From "cold iron," which is all systems off and cold, to moving the ship at full speed took 8 minutes. In a conventional steam boiler ship that took 48 hours.
Chris Moore Jet engines themselves are reliable pieces of machinery. Can't imagine with the extra "over built" nature of these engines to power generators, they must last damn near forever.
Imagine having to work on a nuclear reactor in something like a sub or aircraft carriers *I think some other ships have them but most likely wrong there*
I am a compressor station operator on a gas pipeline in New York where we use a Solar Mars 100 (15,900hp) to run our centrifugal compressor. I wish you had done my initial turbine theory training as I have learned (and understood) so much more from watching your videos than from a week of official Solar classroom time. Having said that - management is discussing adding a Solar Titan 130 (20,500hp) to increase our capacity and while reviewing the specs on this unit I noticed that while the Mars 100 power turbine is referred to as a 2 stage axial, the Titan power turbine is called a 2 stage "reaction". I've tried to do some research online but find very few references to reaction turbine in the realm of gas turbines. Most of the references are to water or steam. I found one short video on youtube that gave a brief definition and it appears to have something to do with the angle of the blades on the power turbine stages. I was hoping you would be able to clarify the difference between an axial turbine and a reaction turbine - as well as why you would use one as opposed to the other. Thank you very much for your channel.
AgentJayZ Damn I didn't want my first question to be one you already answered. Apologies for not locating it myself and thanks for actually taking the time to point me in the right direction. I think over the last month or so I've watched all of the Q videos in order. I guess it's time to start at 1 again and work on my retention. Thanks again for the videos - will definitely keep following.
It's actually more complicated than that. There are two types of axial flow turbine blade arrangements. An impulse turbine works on changing the direction of the flowing gases without accelerating or decelerating it. A reaction turbine works by having a gas pathway that narrows from entrance to exit, and this causes the gases to accelerate as they pass through the blades. Most turbines are a mixture of impulse and reaction, as chosen by the deign engineers.
When we mount blades, we always weigh them, and then assign them a place of the disc/hub. That way it is balanced out. The two blades with the closest weight to each other sit on opposite sides of the disc. The discs are then rivet bolted. The turbine blades have a small amount of play. This is normal. It allows for expansion from heat, and it allows the blades to find their natural center during start-up and shut down, much like helicopter blades and their flapping.
About twenty years ago I was privileged to be given a tour of a Transgas boost station near Caronport SK. One thing that impressed me most was how much care was taken to filter the incoming air prior to supplying it to the intake of the compressor. I wish I had even a smidgen then of the knowledge I've taken in from watching your videos. I would have appreciated the tour much more I think.
I was working for a gas company. We repaired and maintenanced the turbines sometimes by ourself. the biggest was a titan 250 which was used to compress gas to i think 70 bar. the smallest we had was a turbine from a helicopter which was used for producing electricity with 2200 horsepower. all of these turbines were inside giant metal boxes to reduce the noise they make and it was also better for cooling. there were huge ventilators blowing fresh air through these boxes. we weren't allowed to open the boxes while the light in the turbine hall was on and also not allowed to make pictures with our smartphones through the glas of the box with flashlight on. In the turbine boxes were photosensors which should detect fire and if they get activated, the whole turbine hall will get flooded with co2. it was so amazing to hear these beasts start up and rev to max rpm.
Awesome video, your explanations are so clear that my 5 year-old nephew could understand them! Thank you very much for going through the trouble of putting all this together for us interested ignorantsvto become more knowledgeable!!!
oh god these videos are goooooood! I am a Level 2 Aerospace Engineering student in West London. Watching your videos just out of interest.. So so good. giving context. giving depth. fantastic.
"So now you're an expert" - Few channels leave me with net knowledge gain after every video - this is one. Much thanks AgentJayZ. While I'm not going to be rebuilding turbine engines in this lifetime, your teachings grant a level of demystification granting insight into that magic cephalopod living under the cowling on commercial airliners. That has been one of the best Eurekas I've had in a long while.
Never had it explained so well before, especially the difference between the compressor section, and the blades / shaft where it gets its power - and the main power / load section. Awesome Job!
balancing the single stage LM15 power turbine at 11-12 minutes was seriously scary. At one point, a young mechanic walks within what looks like 18 inches of the blades-at speed, wearing a loosely fitting hoodie. One little trip into those blades would have said mechanic spray-painted all over the inside of that shed. I was literally scared for him.
Hi JZ enjoyed your explanations of turbine engines. I’ve flown a PT6-47E Free Turbine engine on a Pilatus aircraft. The compressor rate RPM is north of 37500 rpm, whereas the power turbine free side is conveyed into approximately 30000rpm with a planetary reduction gearbox generated 1700 rpm for the propellor. Thankyou again for your great videos. MRM
@Blackmoonempire Because of the hi temperatures involved, engine self-locking nuts can't have any plastic parts. The self-locking nuts used in aviation and industrial gas turbines are either solid and slightly ovalized for the top portion of their thread, or have axial slots cut halfway down from their top and the resulting "tabs" are bent inwards slightly.
Great videos... I am a systems engineer but I love jet engines and it is just great to be able to see how it all works through your camera. Thanks again, Jorge.
Your videos are honestly the only reason I now understand turbine operation and utilization. Up until now it was a combination of Charlie Brown's Teacher talking and the textual equivalent of arcane text such as the Necronomicon. You rock.
The overhaul manual of a current model of the GE LM2500, an engine which includes an integral power turbine and therefore produces it output as a turning shaft, states that the max continuous output torque is 66,000 ft-lbs. The shaft turns at 3000 to 3600 rpm, so that works out to around 38,000 Hp, which is the rated output power for that engine.
You could say that. In a two shaft turbojet like the Olympus or J57, the LP compressor acts to supply a consistent supply of compressed air to the core of the engine. Much like a supercharger, this increases power output. A later development of the two shaft turbojet was to increase the size of the first stage or two of the LP compressor, and divert some of the extra compressed air around the core.
@krbruner The main rotor rpm of a helicopter does not change, but the rpm of the GG goes up and down as the fuel control varies the power as needed to keep PT rpm constant. If the pilot pulls too much pitch, the main rotor rpm begins to drop, as the temp limits on the GG will not allow enough power to be generated to maintain the PT rpm. This causes alarms to go off: both for GG temp and for low PT rpm. In other words - reduce the load or crash.
Yes, the turboshaft engine has an integral reduction gearbox, whose output is usually around 6000 rpm. Then there is the helicopter main gearbox... not part of the engine, and its output is the main rotor shaft, so 400 rpm or so for a light helcopter. The turbine engine consists of the power turbine and reduction gearbox, designed to run at a constant 600 rpm, and the gas generator, which varies in rpm on order to supply the PT with what it needs to stay at 6000 despite varying load.
I operate a combined cycle power plant which uses a GE 7FA combustion turbine. We do not use a separate "power turbine" as everything is common to one shaft. So we have a compressor, 3 stage power turbine, and electrical generator all on one shaft. The hot exhaust is used to produce steam for a steam turbine/generator set. All this is designed for 3600RPM for a 60Hz electrical grid. Seeing you explain some of these other types of turbines along with some of the different terminology that goes along with them gave me a cool new perspective on what other designs are out there.
Th GE 7 is a single shaft engine, and a large-purpose built industrial turbine engine. I don't have any experience with them. The small Solar Saturn is a single shaft, as is the RR 501, which is adapted from an aviation design. Most of the aeroderivative engines we see are adapted for industrial use by being coupled to a separate power turbine. And the exhaust is often used as a source of heat to make steam. Why waste it, eh? You are right; there are many ways to get the job done.
@krbruner Generating electricity, the rpm of the pt connected to the electrical generator is very carefully controlled. But not more carefully than a helicopter main rotor. The pilot controls the load on the main rotor, and main rotor rpm controls fuel to the gas generator. The main rotor never overspeeds, because of the fuel control to the GG. If the pilot increases the load on the rotor, the GG instantly responds to maintain PT rpm.
@tranceaddict704 The PT6-A is about 500 hp... roughly. The last LM2500 we put together was rated at 34,800 Hp. So yes, the same principle as the PT6, only bigger.
The blades are less fragile than you think... in the way a sledgehammer is less delicate than a feather. The aluminum drift will never touch the high-nickel alloy that the blades are made of. The alloy is used for two reasons: It maintains its incredible strength, stiffness and toughness at very high temperatures... and it is incredibly strong, stiff and tough. Toughness is used here as a technical word meaning being very resistant to fracture of cracking.
I have watched many vids and talked to many people about these engines, you just made me completely understand how and why they work and what the differences are for... thanks
great video. i work on avon, olympus and ruston TD4000 fuel control systems used on the oil rigs/power stations. i'll never get bored of hearing the GTs firing up. only thing i don't like are the mechanical overspeed tests lol.
@oisiaa I think the rotor disks are different. I could check the manuals to see if the part numbers are different, but we don't have the CF6 manuals. As hinted to in the video, the manufacturer strongly discourages (forbids!) any mixing of the industrial and aviation worlds.
@JETZcorp The info is very hard to come by... but I think those turbine trains used a de-rated version of the LM1500. The fuel consumption of a turbine engine does not fall to near zero at idle as it does with a diesel piston engine, so they are really only economical to run in applications where they are working at or near max power most of the time.
@TheDeeSpence I'll bet it's more expensive than the engines connected to it. Wish I could see some video of that very rare and powerful piece of machinery.
Gearhead Numbers: Paraphrasing from a book, each postage stamp sized turbine blade generated 660 hp to develop 75,000 hp. We had gone from a 28 cylinder Pratt & Whitney R-4360 developing about 1 hp per pound of engine to a Rocketdyne High Pressure Fuel Turbo Pump developing 100 hp per pound of engine, the highest power density rotating device known anywhere in the world in its time. The two-stage turbine was 11 inches in diameter, spun at 36,000 rpm, and generated 75,000 hp to feed fuel to NASA's Space Shuttle Main Engine. From Rocketdyne: Powering Humans into Space, p. 214 - 215. AgentJayZ, FANTASTIC videos sir! Although these numbers are from a slightly different theme, I thought you might appreciate them. As Buzz Lightyear would say, "To Infinity & Beyond!" Keep up the GREAT work sir!
There is... between the power turbine and the load ( generator or gearbox). The gas generator turbine, sometimes called the compressor turbine... provides the power to turn the compressor of the gas generator. The leftover exhaust energy then turns the power turbine, which provides the power to turn the load...
@topdoorslammer666 It's a temporary setup, and while we rearrange things we still have to do an occasional balance with this machine. We have three balance machines in two shops, and we really don't have room for this one.
The result was better fuel economy and more thrust. These enlarged forward stages of the LP compressor became known as a fan, and the engines were called turbofans, or bypass fan engines, or simply bypass engines. The benefits were very significanrt, and the engines were eventually designed so that the major portion of the power developed by the LP turbine was used to turn a huge single stage fan, which bypassed most of its output around the core. These are the modern, high-bypass turbofans.
@oisiaa Hmmm, I have taken an LM2500 apart and rebuilt it, but we never disassembled the compressor rotor, and it stayed on a stand. The rotor is hollow, because it is built up like the LM1500 rotor... but it does not have a large passageway through it for the non-existent LP shaft. So the answer to your question is yes and no...
I serviced and repaired many combustion powered generators 150KW diesel and gas, and the detail you gave on the turbine engine, and speed of 3,600 RPM with the gear reduction box was great!!!, and all controlled by the fuel in the core of this wonderfull engine with a massive HP rating for the MEGA WATT OUT PUT!!! was easy to see. Thanks for the insight into this field and keep up the good work.
The two rings of heavy wire are there to halp dampen vibration in the blades. The strength of the blades is compromised by having hole drilled in them, which is why later designs of this machine did away with the wire damping, and changed the blade mounting system slightly.
@narcoti ...Very unusual question. So unusual I can't answer it. The output of an LM1500 is the exhaust gases, which are about 900 degrees F, and about 30 psi. Roughly 150 lbs per sec at full honk. Convert that to SCFM? Not me! And if you mean what's the output of the compressor, then it's 150 lbs per sec, but now it's at about 450F, 140psi... another conversion to SCFM... That's why jets aren't measured in volume of flow.
The closer the actual working speed of the PT is to its design speed, the more efficient it is. Sure the electrical grid synchronises the PT, but it wants to spin at very close to that anyway.
"if you know exactly, great tell me" hehe, right as you said that, I happened to be looking at the PT6 book. Axial Flow Compressors: 37,500RPM @ 100% N1...same for centrifugal impeller. Power Turbine: 33,000 RPM @ 100% N1 Shaft angular velocity is 2200 RPM @ 100% N1 Great Videos Jay! Can't wait for more!
Yes, interestingly the CT58 has an optional reduction gearbox, for use in some aircraft. The two CT58s that I have worked on were originally from CH-47s, and they had the reduction gearbox. It seems to be more highly stressed, and less reliable than the engine itself.
Nothing is free. In our engine, the fan needs about 20 thousand Hp to turn at 3400 rpm, and that power comes from the LP turbine. The HP compressor and turbine, also called the core, is turning a bit more than 9000 rpm to supply the gases that turn the LP turbine.
About 85 km west of London is Didcot Power Station. Actually, there are three stations, the 'B' station is about 15 years old and is a gas-fired combined cycle station of about 1300 MW. The 'A' station closed in March this year. It had four 500 MW steam sets, originally coal fired, later converted to also burn gas. The third station, part of the 'A' station is a small gas turbine station, which could be used to supply power to start up the main steam plant, or to feed the grid at peak times.
No.In a few rare cases the fan is geared to a lower speed than the Hp system. In two shaft engines, which are the majority, the two systems turn at their own best rpm, and the LP system of turbofans is optimized for turning the fan. Almost all arliners do not have reduction gearing driving the fan.
Turboprops and turboshaft engines are designed from the first day of their existence to do what they do. Gas turbine engines of all types are the product of much more intense engineering and design than any automotive engine. That's why they don't change much over decades of refinement, and why they stay in production so long. For the price of a new Veyron engine, you could do a part of an overhaul of a small helicopter engine.
Thanks JayZ! All great information to have for... well, maybe next life. I liked "testing the rent-a-jet" video too but would really like it if you spent some more time showing us the details of the data on video monitor.
Holy smoke. On the balancing there was no shroud. Where I worked people would freak out. We has one set up for a fan (low pressure compressor) that was only partially covered on the side and other people complained. I'm impressed with that set up. Looks adaptable for different applications.
Thank you for hundreds of hours educational entertainment. My dad was one of the owners of INTERNATIONAL GAS TURBINE so as kids we had our share of jet engine discussion.
@krbrunerOK, your ideas are sounding better. as for controlling PT rpm, that's done by the load. Remember, a PT works against a huge load all the time. If you back off the fuel to the gas generator (engine), the PT instantly loses rpm. No need to bleed off the gases being fed to it. Negative throttle response, as in reducing power, for a gas turbine is instant. You might be interested in a book I am always recommending : "the Jet Engine" published by Rolls Royce. Probably in your library!
Yes, the power turbine uses the exhaust energy of an industrial gas generator to produce mechanical power. It is a turbine that produces mechanical power from a stream of gas. That's how it got its name
As far as I know, even the free power turbine turboprops still have reduction gearing. The PT turns much too fast for a propeller. The PT6 and the PW100, as well as the RR250-B17 are all free power turbine turboprops, and all of them have a reduction gearbox between the PT and the propeller.
This is really an amazing video. I've been on the obsessive side of casually interested in all of this 'stuff' for quite some time, and I've never seen how closely all of the applications of turbines relate to one another, from generators to airliners. Your simple but well explained visualization of how a turbofan operates was very informative. It's also kind of funny to think how much different the public perception of a commercial 'prop plane' is from a 'jet' when they are nearly identical.
I immediately recognized the last two engines as the PT6 and Garrett engines! A book that uses those two engines as examples and also explains a TON about turbines in general is the ASA Aviation Maintenance Technician Series: Powerplant by Dale Crane. Alas, no specific free power turbine rpm but considerable amounts of good information!
Thanks so much for your reply. I understand your skepticism about my idea but I didn't say I didn't have a turbine but only said I got rid of the turbine in the hot exhaust. Since I'm now retired I've had time to build a crude model of my design and the principle works amazingly but not being a jet engine engineer I can't say whether it would work in a full size engine. I've shown my model to a friend who was an engine mechanic on c130s in the Navy and he was amazed at how it worked and said he'd never seen anything like it before. I'm still just feeling my way and don't want to lose the idea as I can't afford to patent it yet.
You are missing the point I'm trying to get across. The energy is in the exhaust, and the compressor needs a lot of power to work. Turbines exist because they are the lightest, simplest, most efficient way to turn energy in a gas stream into mechanical rotating power.
@@AgentJayZ sorry I don't mean to frustrate you but I agree with everything you've said about the energy in the exhaust it's just that I've discovered a way to harness that energy without a turbine in the gas stream. But I do need to do more work on it as I've only got about 2500 rpms in my model at the moment. Do love your videos so much. Learned so much. I'm an old Kiwi now living in Oregon. Cheers
Just saw the answer to my question at the turbo prop part at the end of the video. Anyway thank you very much for your explanations and your educational stuff. Very high information grade, very authentic, well made. Thanks for your enthusiasm.Torque rules, speed moves.
Thanks for all the info, I think I will check out that book as I am really interested in gas turbines, I think part of my problem is thinking that they are all a cookie cutter solutions. A elec. generator is rather heavy and I am sure that the flywheel effect makes it so much easier to control, where as a small turbine in a helicopter probably has much better throttle response, so it can trim out the PT easily for optimal operation...keep up the series, always enjoy them.
@LarryCanFly If it's a home-built helicopter, you're on your own. If it's a production model, the engineers would not waste weight on something that was unneccesary. Helicopters have reduction gearaboxes because a power turbine that turns at main rotor speed just won't work. If it would work, then that's the way helicopter would be built. That's what I meant.
Thanks for these awesome videos! I've learned a lot about turbines and several other things you show in the videos! I very much appreciate the time you take to make them!
Thanks SO MUCH for this, and all your amazingly informative and no-nonsense videos. Keep doing what you're doing. We all appreciate your efforts enormously. THANKS !!!
I really enjoy your videos. I am not in the aviation field, but find them very interesting. They do a good enough job getting it to a level anyone can understand!
Very interesting .. highly informative..Gr8 job AgentJayZ, me being a vibration anlyst didnt have much opportunity getting the hook of .. The last words you mentioned - "NOW YOU'RE AN EXPERT" are realy possible for people who just lack this exposure.. Long live you.. Try to post any troubleshooting of these GGs and PTs so one can really become an expert.. Kudos
Over the time i get an expert about turbine and his technology. Thank for this Jay! Greets from germany to the far distace canada. Maybe when i will make a little vacation up there, i ill visit your shop! Thx
AgentJayZ I stand corrected on that figure, I do not have one in my backyard myself, as awesome as that would be. The object of my comment was to explain why the PT6 spins so much faster than the LM1500. If you have any more input on the matter i'm all ears (or eyes, i suppose), I am always ready to learn. Keep up the videos, I enjoy them a lot
It is interesting to compare the product of (shaft speed x tip diameter, or tip speed) on the last stage of the GG turbine, and (shaft speed x tip diameter, or tip speed) on the first stage of the PT. It is also interesting to compare the disks. Some aircraft GG turbine stages are so flexible(when not spinning)that they wobble -- flop like a potato chip. As you point out, aviation GG rely on more intense inspection and maintanance schedules, because they cant be overdesigned like PTs.
Your question does bring up the point that the terms used often are confusing, and a few drawings can help clear things up. I've just re-watched "Turbojet or Turbofan", and it does leave out a few details that you might find helpful. I will make another video that will try to illustrate the answer to your question, because I think it is a good one, shared by many. I will put that video on the waiting list, as I have about five to complete first. Stay tuned!
The PT-6 is like the Chevy 5.3L of aviation. It's hard to dislike it because it is common and it just plain works. But like you said, it has its advantages in certain applications where the Garrett has it's own advantages elsewhere. I've seen that the PT-6 is a gold standard of sorts in fixed wing and the Garrett in more use in helicopters.
Oh dear, not sure if I should have watched this, it looks absurdly simple to build a simple engine, once I've sourced the compression ratios I might have to have a little tinker in my garage to see if it can be done, if you see a news clip showing first UK man into space in a garden shed you may take all the credit you want for the inspiration. lol
+Lewie McNeely it's quite an old picture of me, however my forays into building a simple turbojet did produce some interesting fireballs and a brief period without eyebrows was the net result of my last attempt.
I go on at chromium domes because when mine touches my ears, it's GONE! I can't handle it at all so I'm like your old picture most of the time. Glad it was only eyebrows! Cheers 2 U!
not in all cases you dont, the CT58 I work with has no reduction gear box, its a straight drive into the 'freewheel' unit of the main gearbox (Sikorsky s61 in this case) after the freewheel unit you have the reduction gears. Of course some turbo shaft engines DO have an integral reduction gear system, turbo prop being a common one.
The reason I said "don't ask me" is because I don't know the ratio of impulse to reaction of this particular turbine ( or any others ), and even if I did, the combination of equations needed to solve for a design speed at any particular mass flow and gas velocity is more than I want to tackle.
@AgentJayZ Not misleading, I am just an over-thinker! Maybe I worded that wrong, I meant that the PT rpm is regulated by the pressure inside the duct. It is, I guess, acting like an torque converter with air as the coupling medium. As for the bleed valve, that would be like a wastegate on a turbo charger, which I could see as useful if they quickly need to control the pt rpm faster than the average throttle response of the engine, which In some application, would be quite required.
@AgentJayZ As for the helicopter comment, since in flight, the load is going to vary anyway, just in maneuvering, (pitching the nose up while moving at a decent speed, puts tremendous load on them very quickly) so the stability of the rotor RPM is not as critical as AC electricity power generation, where it is important to match Voltage and Frequency as best as possible to feed it onto the grid.
