Rolls-Royce's digital twin engines

One major player in the world of digital engines is the Aerospace company Rolls-Royce. Specialist in mechanical analysis Rob Fox explains what kinds of digital twins Rolls-Royce are currently involved in.

Rob - The answer to that question is that we're doing many types of digital twins, and I'll take you through a couple of examples. And they range from connected to unconnected digital twins. So a connected twin is something that's live monitored, so it's passing information back and forwards. We use those sorts of things to spot if engines aren't functioning as we intend. So we'd have a mathematical model of what speed and how hot we expect the engine to be, for example. And we'll be receiving data from flights at the service centre to tell us whether engines are behaving as we expect, and that'll allow us to schedule inspections or maintenance and things like that. Unconnected twins are generic models, but we'd update them offline. So that might be something like an engine on a test bed where we're going to undertake a very, very nasty test on it, and we would then produce that model and update it based on the parameters of the day and the conditions that we saw to give us a better indication as to how the engine performed under those testing conditions.

Will - What would be the data that is being sent back to you from these engines? Is it just a matter of temperature? Is it how well the parts are faring under pressure? What kind of stuff?

Rob - It would be dependent on the type of model, but to give an example for the connected twin, it would be things like shaft speed, so they'd be like the RPM that you would get in your car. So how fast are things running temperatures and pressures from within the engine, because obviously we would have an idea of what performance the engine is supposed to be providing and how its internal is supposed to be. So if it's running too hot or too cold, that will be important information for us. But then other things as well, like fuel flow, for example. So we'd know how efficiently the engine's operating, its fuel efficiency and also safety measures. So we'd monitor vibration within the engine and that way we'd know if things were changing within the engine, we'd spot those earlier and hopefully track engines through their life to see if they're suddenly changing as well.

Will - How often does all of this data from the engines come through back to you?

Rob - So the data being transmitted is obviously somewhat limited by the bandwidth available, but it is constant transmission from assets in service. So there's a lovely video on the internet of Rolls-Royce IntelligentEngine, which kind of gives a view of that. The data updates aren't many thousands of samples per second as you can imagine, because you've got thousands of hours of flights in real time. But the data is reasonably rapid updates within the confines of what we can save and and secure.

Will - So this sounds really useful in terms of being able to spot when something might wear out or break, but is it useful as well for potential improvements if you're prototyping an engine?

Rob - Absolutely. I mean, we would start with a generic understanding of how we expect a thing to be operated in service and we'll establish the life prediction for it. So, we will know that a particular part might be able to operate for say, a thousand flights or something like that. Usually very expensive parts if they're live. But if the aircraft is operated slightly less arduously, so fewer passengers on a particular flight, so the engine is operating at lower power settings. By measuring and knowing that we can then increase the operational life of those expensive parts and in development testing. So when we build an original engine, we'll start off and it will be quite a rough design, relatively speaking of course, and the performance. As we hone and improve our models, we can then get closer and closer and closer to the real understanding of the limits and conditions and can also manage how we operate it. So not push things, uh, quite so hard if we recognise that they're causing these issues.

Will - Yeah, I shudder to think how expensive, expensive parts are and stuff like aircraft and engines. So even with the complexity of creating a digital twin, does it therefore make more economic sense to do this than to build a second one and see how that fares instead?

Rob - Well, yeah I mentioned an unconnected twin. So my background is fan blade off testing. So we'll release a blade and we'll destroy an engine on a test bed. Anybody looks on YouTube, you'll see numerous videos of fan blade off tests. They're very exciting, but they're also very nerve wracking moments because you're taking a very, very expensive jet engine and you are essentially blowing it up. We make models of those before the test so we know that they're going to be successful, but you've still trashed an engine. And where we might wish to use an engine in different applications, so perhaps taking one that's been used in a civil context and used in military aircraft, you would not necessarily wish to redo a test that you already know is okay. So you take your digital twin of the test that you'd already performed, adapt that and avoid the necessity of performing a secondary test, which you already know the outcome of anyway, and would have very limited learning from. And that can save you many millions of pounds and many months in the development program for a new engine.

Will - From an environmental and resource management side as well, this is using a lot less stuff.

Rob - Absolutely, absolutely. I've mentioned predicting maintenance for example, if you have a generic understanding of how a part's going to be used in service, you might estimate that it can last a thousand flights and it's very expensive metals. If you can know exactly how a particular part is used, you can extend the life from a thousand to two thousand to five thousand flights. Then all of a sudden you are reducing the CO2 production simply from making the parts, you are also not taking the engine off wing. So it's been able to be in service much longer minimising the resource consumption whilst maximising the operation. And obviously that enables us then to use things for longer and get the full life out of everything rather than going with a worst case scenario and pulling something off just because we don't know what its condition is.

Will - You've got the environmental side covered, the economic side covered. Where are you planning on taking this sort of system next? What's the future of digital twins at Rolls Royce?

Rob - Probably an increased level of connectivity. You can imagine there are many thousands of aircraft flying around. They have very limited bandwidths of data transmission back to base. So increasing the degree of connectivity and the faster updates so we can hone even further still and really eke out every opportunity to get data, but also that'll enable us to make faster decisions as well. So rather than landing an aircraft with a suspicion that we need to look at the engine, we'd hopefully land with not only the suspicion, but knowing in more detail exactly what it's that we're going to look at. And also linking data together as well and various different twins. So examples would be for perhaps a part that we built on a test bed, we've assembled it and moved it around if we find that it's damaged in transit, having twins for transit as well as what testing was performed. You can ascertain whether the damage perhaps occurred when it was being tested, when it was being transferred, or when it was in the build shop and things like that.