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Jet Questions 90
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07:33.5
07:43.0
07:43.0
We'll see how complicated it is. This is one right here. It's a big piece of pipe but is really like a big annular chamber.
07:46.0
08:00.0
08:00.0
It's meant to contain the air pressure around the combustor and this one has two holes right there, those are for the igniters, those holes look like drains.
08:09.0
08:21.2
08:21.2
That is where the hot air is taken off for the anti-icing and those two holes here, those are for the igniter plugs, see.
08:31.1
08:36.7
08:36.7
Ok, so air is rushing this way, is going to get to this solid surface and go around it.
08:36.8
08:49.4
08:49.4
This surface and go around, and just go around and some of it is, that's where the fuel nozzle goes, some of it's going to get down a little circle, circular hole and travel into the combustion chamber.
08:49.4
08:58.7
08:58.7
Now, all this other stuff, other air is blasting on the outside and it's got little holes to go in and it gets in whenever it can.
09:13.2
09:22.4
09:22.4
And all the little holes everywhere are where cooling air, or the rest of the air, can leak in. By the time we get to my fingers right there.
09:29.1
09:39.6
09:39.6
It's the hot combustion gases that go into the turbine so the way that the air is diverted to be cooling air is by the metal structure that this thing is.
09:39.6
09:50.4
09:50.4
The combustor liner and by tuning the diameter and the number and the shape you can control how much air gets in, where it gets in and all that stuff.
09:50.4
10:03.4
10:03.4
So that's how you control the amount of air that mixes with the fuel and the amount of air that mixes with what was once the air and fuel and is now flame.
10:06.2
10:14.4
10:14.4
This is an annular combustor that looks a lot like a series, a circle of individual combustor liners
10:21.3
10:30.4
10:30.4
to a pure annular combustor like the LM2500 which was featured in, I think it was your questions or jet questions 56 or something like that,
11:02.2
11:10.0
11:10.0
Ok, we're here at the cutaway in front of the shop and we're going to see why you need to be more specific.
11:15.2
11:22.5
11:22.5
Let's see. Those little holes. Those little holes. Those little holes. These little holes. Those little holes.
11:22.5
11:31.1
11:31.1
This little hole. That little hole. These little holes. Those little holes. Those little holes. This little hole.
11:47.8
11:56.2
11:56.2
If you can't be more specific, at least put a second by second time signature on the video related to the question you're asking.
12:06.2
12:15.6
12:15.6
Ok, along the compressor, go to the front, past the actuating rings, looking on the intake.
12:20.3
12:30.2
12:30.2
Himjan asks: "Excuse me if the question is answered before, why do you need to separate fuel lines to start and to run?"
12:30.2
12:39.3
12:39.3
Well, if you look at my "fuel nozzles 3" or "fuel nozzles 4", I'm not really sure which one, I can't remember.
12:43.6
12:52.2
12:52.2
For starting you need a nice fine atomized wide spray pattern to distribute flammable stuff everywhere so it'll catch fire.
13:02.2
13:12.1
13:12.1
And on an old fuel system like this, this is an Orenda fuel nozzle, the same thing that's in that guy.
13:17.4
13:25.1
13:25.1
It is continuous all the way through and they supply this little line that goes into a tiny orifice in the center of the fuel nozzle
13:31.8
13:42.1
13:42.1
Which is what you want. Independent of this connection, this goes all the way around the engine in one circle and it's supplied by one supply line from the fuel control.
13:42.1
13:47.5
13:47.5
This one, and although it looks like they intersect there but they don't, it just looks like it.
13:47.5
13:55.7
13:55.7
This is supplied by its own individual fuel line from the fuel distributor, field distribution block
13:55.7
14:03.6
14:03.6
and supplies this large line and it introduces fuel from this larger annulus right there.
14:22.7
14:33.5
14:33.5
Hang on, there we go, you see how there are six individual lines leaving that and one, big one going in.
14:33.5
14:41.1
14:41.1
That's the fuel distribution block and each of those lines goes to its own fuel nozzle.
14:48.1
14:56.2
14:56.2
The primaries are for starting, secondary is that what you call the main running line and they come to each fuel nozzle.
15:05.7
15:12.4
15:12.4
The "Rotor balance job on the J-44". He says: "This is the first time I've seen a centrifugal compressor on your channel.
15:22.2
15:36.8
15:36.8
An axial compressor has 10 to 17 stages which is a lot of stages because each stage is not very ... doesn't have a very high compression ratio.
15:36.8
15:43.7
15:43.7
Can raise ... it can compress the air by about 10 percent maybe 15 percent which is not very much.
15:43.7
15:51.1
15:51.1
Whereas a centrifugal compressor, because it has more of a ... it's not a positive displacement device
16:06.6
16:15.3
16:15.3
Which is up why centrifugal compressor is usually one stage, sometimes there's two but usually one.
16:15.3
16:30.6
16:30.6
So the air comes in the front of a big impeller, they call it, wheel, and it gets ... starts to turn and as it travels rearward,
16:36.3
16:47.9
16:47.9
And as it travels outward, it experiences increasing amounts of centrifugal or centripetal force.
16:59.6
17:06.5
17:06.5
And the wheel is usually as big as it can be made until it wants to fly apart at the operating speed.
17:06.6
17:18.4
17:18.4
So you want to get the air rushing outward as hard as possible and as it speeds up, the pathway gets smaller.
17:28.5
17:39.5
17:39.5
It has to pass through a smaller, the same amount of air going quickly goes through a small hole as going slowly through a big hole.
17:41.8
17:48.0
17:48.0
The pressure at the intake and the pressure at the outlet of the impeller is exactly the same.
18:04.7
18:16.4
18:16.4
Ok, so your air is ... it's coming at me and it's rushing out to the side now in a very small height and width of a passage.
18:35.7
18:43.8
18:43.8
Now I know you have difficulty with wondering how air rushing into an opening up cavity can be compressed, it seems crazy.
18:53.1
19:03.0
19:03.0
If you look at the Bernoulli equation, the energy, the total energy of the flowing airstream stays the same.
19:21.0
19:27.8
19:27.8
There's lots of really cool animations and diagrams on the Internet that I have nothing to do with but I endorse entirely.
19:27.8
19:37.2
19:37.2
Have a look at them and all I can talk about for Bernoulli's equation is read as many sources as you can until it finally makes sense to you.
19:37.2
19:44.0
19:44.0
It's really hard to wrap your head around subsonic aerodynamics and then when things go supersonic it all changes.
20:05.3
20:11.8
20:11.8
When a customer send you a turbine engine, what is generally, typically wrong with it?
20:15.1
20:24.4
20:24.4
Is the customer request as simple as: "See engine in close please, restore it to working condition at any cost". Sometimes.
20:24.4
20:32.9
20:32.9
Or does a more nuanced conversation take place with customer involving the type of work involved, expected cost in parts and labor, etc.
20:32.9
20:40.0
20:40.0
I understand that some of your work involves transforming an aircraft engine into ground-based turbine unit.
20:40.0
20:49.0
20:49.0
Do some engines sent to you by customers fail a cost-benefit, a cost-benefit analysis in which case you notify the customer wholly macro buddy?
21:09.8
21:21.5
21:21.5
And if one, if there's one problem the customer may find that in a borescope inspection or a visual external inspection and they'll ship it to us to say:
21:24.2
21:31.4
21:31.4
Then we take the engine apart, we find other things like: "Hey that's cracked, that should be replaced, it's going to go" or: "This is worn out".
21:35.0
21:44.0
21:44.0
Because you're not going to approve one repair job with a damaged part and say: "Just put it back together with the damaged part".
21:53.9
22:00.9
22:00.9
If you're flying the thing, if it's in a military fighter jet or especially if it's in a passenger airliner, which we don't deal with.
22:06.3
22:11.2
22:11.2
Every single component and every step of the way and it can cost a huge amount of money.
22:11.2
22:22.9
22:22.9
If you have an industrial version of that engine and you say: "It sucked in a coke can and it broke something in the compressor, can you just fix it? Just get it running."
22:22.9
22:29.4
22:29.4
We can do that and then we'll notice things saying that: "Well this looks really worn, this looks like it needs to be replaced".
22:34.6
22:42.4
22:42.4
Or they'll say: "Good idea, let's increase the safety and performance of this engine and do that".
22:42.4
22:52.4
22:52.4
And then other times they'll say: "Well, you know it's old and worn out and rather than spend millions of dollars making it new again we're just going to retire it".
22:57.8
23:03.3
23:03.3
There's a lot more leeway when it's an industrial engine and the owner literally can do whatever they want with it.
23:03.3
23:13.6
23:13.6
With certain aircraft, military aircraft, they have high standards but they also are not bound by FAA regulations.
23:13.6
23:24.4
23:24.4
They have their own. And if it's an FAA controlled situation like a commercial airliner you have to do what has to be done.
23:28.0
23:37.6
23:37.6
We do not do that work because in a nutshell, and the short way of explaining it, massive amounts of paperwork in legalese.
23:37.6
23:48.1
23:48.1
And we would need several more managers just to handle all the red tape, let's call it, so we don't do that.
23:50.9
24:00.6
24:00.6
There is a lot of work in the industrial sector and in the experimental aircraft and military aircraft market and that's what we stick to.
24:25.0
24:33.9
24:33.9
This particular cart trolley, trailer, thingy, majig, whatever it is, it's designed to be used on an airbase only on flat ground.
24:41.1
24:52.0
24:52.0
It can handle different engines but it's meant to be towed around on an airbase so the engine was shipped to us like this because there was no engine container.
24:52.0
24:57.1
24:57.1
So now that it's finished it's mounted on it by the engine mounts to the trailer here.
24:57.1
25:02.3
25:02.3
It's wrapped in bubble wrap and then shrink wrap. Not shrink wrap. What is this stuff?
25:04.7
25:11.8
25:11.8
And then it's going to be on a truck on these tires. The trailer will be hooked to the trailer.
25:11.8
25:18.8
25:18.8
The trailer of the truck will be lashed to this thing not over the engine and then it's going to be tarped.
25:18.8
25:29.4
25:29.4
So what we've done, because the truck drivers request this and they love it when we do this because it saves a lot of time, is we put softeners on all the sharp corners.
25:38.9
25:44.8
25:44.8
This is going to be on the truck for a couple of days and so it's going to be protected from the weather.
25:44.8
25:51.6
25:51.6
But it's a bit of an unconventional way to ship things because this is not ... it's not a shipping container.
25:55.1
26:01.7
26:01.7
Usually they're inside a metal can which provides complete protection from the weather.
26:05.9
26:12.5
26:12.5
It's wrapped in a not exactly waterproof fashion because we've got these struts that we had to wrap around.
26:12.5
26:20.5
26:20.5
But it's going to protect it from most contamination and then all of this is going to be under a tarp so it's going to be pretty good.
26:31.1
26:40.3
26:40.3
I might be a little bit behind the times here but I just looked at "Star Wars, The Force Awakens" and I was amazed.
26:40.3
26:48.1
26:48.1
Was funny how in Star Trek, a lot of engine stuff that we deal with was in the background in the engineering section.
26:48.1
26:56.4
26:56.4
And sure enough, when Khan Solo steps onto the Millennium Falcon and he's got three of these in his pocket.
27:03.2
27:08.9
27:08.9
It's pretty hard to tell because actually the movies are not that sharp, on my computer anyway.
27:31.2
27:45.1
27:45.1
What it is, it's a magnetic chip detector plug and got two o-rings on because it fits into a hole and then these two things lock it in place.
27:45.1
27:51.9
27:51.9
That's a magnet and I'm not sure of these little tap, these little whatever they are, tabs.
27:51.9
28:02.4
28:02.4
Things are on the ones in Han Solo's pocket and some of them have the o-rings removed and it looks like one of them has only one o-ring groove and the magnet is smaller.
28:02.4
28:11.6
28:11.6
Because each engine is different, this is from a Rolls-Royce Avon, it looks familiar doesn't it? I think it does.
28:11.6
28:17.0
28:17.0
Ok, if you're the prop guy for "Star Wars, The Force Awakens", I want to know if that's what this is.
28:30.5
28:35.6
28:35.6
They are from a different engine maybe, slightly bigger diameter, slightly shorter magnet.