Chinese Engine Development

manqiangrexue

manqiangrexue

Brigadier
latenlazy said:
Flying with intakes designed for another engine being suboptimal is precisely why I doubt that the current airframes have been optimized for the WS-15. If they intend on production before the WS-15, I don't think they would go with an unoptimized solution and wait for the untested one that's supposed to be more optimized to make their airframes whole. I'm sure they already have a redesign ready for the aft and the intake, but I'm also pretty certain that the intake geometry (if not external, than internal) and thus every structural element related to the engine will have to be changed, and those aren't trivial ones that can be done with a "plug and play" solution. Whatever changes will be needed to properly fit and utilize the WS-15 will probably need to be done on a future airframe, or else extensive modifications that could take a while would have to be done on a current one.

I myself once thought it would make sense for the solution to be plug and play, but the more I've looked into the complex needs of intake geometry and the tight tolerances for structural requirements, the less I believe that it could be that simple.
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If WS-15 is ready for testing this quickly, would they necessarily go for production of first batch with AL-31 then? If WS-15 were to take beyond 2020, then that would make more sense. Also, how different are the airflow requirements of the WS-15 to the WS-10 and AL-31? An advanced design could have similar airflow requirements while putting forth more thrust. I understand that AL-31 needed ~40% more airflow than similar American engines while putting forth only a few percent more power. Then if WS-15 is indeed advanced, it may require a similar amount of airflow compared to AL-31 while putting forth ~35% more power. Also, WS-10A was developed from the CFM-56 engine, not AL-31 but it could still be used by Flankers and one J-10B prototype without a different type of intake than the ones powered by AL-31. Did it coincidentally need exactly the same amount of airflow as AL-31, or is it enough to be "in the neighborhood"? Do all the different Russian variants of Flanker engines require the same airflow?
 
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latenlazy

Brigadier
manqiangrexue said:
If WS-15 is ready for testing this quickly, would they necessarily go for production of first batch with AL-31 then? If WS-15 were to take beyond 2020, then that would make more sense. Also, how different are the airflow requirements of the WS-15 to the WS-10 and AL-31? An advanced design could have similar airflow requirements while putting forth more thrust. I understand that AL-31 needed ~40% more airflow than similar American engines while putting forth only a few percent more power. Then if WS-15 is indeed advanced, it may require a similar amount of airflow compared to AL-31 while putting forth ~35% more power. Also, WS-10A was developed from the CFM-56 engine, not AL-31 but it could still be used by Flankers and one J-10B prototype without a different type of intake than the ones powered by AL-31. Did it coincidentally need exactly the same amount of airflow as AL-31, or is it enough to be "in the neighborhood"? Do all the different Russian variants of Flanker engines require the same airflow?
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Finishing ground tests isn't a sign that it will be ready that quickly. If we're to believe our chain of leaks, a fully assembled engine started testing last January. If it takes one and a half years to complete ground tests, I would expect a similar span of time (or longer) for aerial and high altitude testing. Then they would have to install the engine in the J-20 to do further testing to make sure that the intake design and airflow management software is adequate. Then they would need to certify the engine and set up manufacturing and assembly for actual production . I don't see the engine being ready by the time we hit that theoretical 2018 induction date.

The airflow requirements are going to be quite different, because the WS-15 is supposed to have a much higher mass flow than the WS-10 and AL-31 (if I'm not mistaken what really matters here is the fan diameter?). Then there are specific flow management requirements for the engine design itself, which will vary based on the engine design.

The J-11B has a variable intake, which probably makes switching engines easier. Its inlet geometry is also not very complex. The J-20's S-duct is going to make inlet geometry much more important. Either way, they probably made some adjustments to the J-11's inlet geometry even if changes aren't noticeable. The J-10B's entire inlet geometry changed due to the implementation of the DSI. There might be internal differences between one equipped with the WS-10 and one equipped with the AL-31, but the differences probably aren't going to be as significant given that they're comparable engines. Being in the neighborhood definitely helps, because it probably reduces variations in performance due to lack of optimization.

The main point though is that all these potential variables will need to be tested.
 
manqiangrexue

manqiangrexue

Brigadier
latenlazy said:
Finishing ground tests isn't a sign that it will be ready that quickly. If we're to believe our chain of leaks, a fully assembled engine started testing last January. If it takes one and a half years to complete ground tests, I would expect a similar span of time (or longer) for aerial and high altitude testing. Then they would have to install the engine in the J-20 to do further testing to make sure that the intake design and airflow management software is adequate. Then they would need to certify the engine and set up manufacturing and assembly for actual production . I don't see the engine being ready by the time we hit that theoretical 2018 induction date.

The airflow requirements are going to be quite different, because the WS-15 is supposed to have a much higher mass flow than the WS-10 and AL-31 (if I'm not mistaken what really matters here is the fan diameter?). Then there are specific flow management requirements for the engine design itself, which will vary based on the engine design.

The J-11B has a variable intake, which probably makes switching engines easier. Its inlet geometry is also not very complex. The J-20's S-duct is going to make inlet geometry much more important. Either way, they probably made some adjustments to the J-11's inlet geometry even if changes aren't noticeable. The J-10B's entire inlet geometry changed due to the implementation of the DSI. There might be internal differences between one equipped with the WS-10 and one equipped with the AL-31, but the differences probably aren't going to be as significant given that they're comparable engines. Being in the neighborhood definitely helps, because it probably reduces variations in performance due to lack of optimization.

The main point though is that all these potential variables will need to be tested.
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Are the American (F-16, F-15) engines using significantly smaller fan blades than the AL-31 to merit a 40% reduction in airflow need? I think it depends on many more complex factors than just fan size; I think better engineering could reduce the airflow need. If the inside of the J-10B's DSI is variable and could be changed then the current J-20 prototypes probably also have some ability to change things up inside a bit. Anyway, small modifications, I can see, could probably be needed and quickly done.

Also, there could be structures installed inside the current J-20's intakes that reduce airflow (such as side vents, etc...) to the engine in order to accommodate the AL-31. When the WS-15 is installed, those structures could be removed or the vents closed so the full airflow opens up into the engine. Just some thoughts, with no evidence to back.

I tend to think that the planners would design the prototypes such that as little as possible extra testing is needed once the WS-15 comes online. I doubt they would design one version for using AL-31 and another very different version for WS-15 which would take several more years of testing. It's just not how I would do things.

And also, if WS-15 could be ready by 2020, I could see them pushing the induction date back 2 years so they don't end up with an odd number of less capable and very different J-20s with AL-31 that they now have to train people to maintain... unless, they could swap the engine on existing jets to upgrade them to WS-15 J-20 standard.
 
SamuraiBlue

SamuraiBlue

Captain
manqiangrexue said:
Are the American (F-16, F-15) engines using significantly smaller fan blades than the AL-31 to merit a 40% reduction in airflow need? I think it depends on many more complex factors than just fan size;
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If you compare the General Electric F110 with the Saturn AL-31 performance you'll find that the F110 has a higher Overall pressure ratio(30.4:1, 23:1) with higher Turbine inlet temperature(1,510°C, 1,412°C) meaning the F110 has a faster air flow with better combustion rate then the AL-31.
 
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latenlazy

Brigadier
manqiangrexue said:
Are the American (F-16, F-15) engines using significantly smaller fan blades than the AL-31 to merit a 40% reduction in airflow need? I think it depends on many more complex factors than just fan size; I think better engineering could reduce the airflow need. If the inside of the J-10B's DSI is variable and could be changed then the current J-20 prototypes probably also have some ability to change things up inside a bit. Anyway, small modifications, I can see, could probably be needed and quickly done.

Also, there could be structures installed inside the current J-20's intakes that reduce airflow (such as side vents, etc...) to the engine in order to accommodate the AL-31. When the WS-15 is installed, those structures could be removed or the vents closed so the full airflow opens up into the engine. Just some thoughts, with no evidence to back.

I tend to think that the planners would design the prototypes such that as little as possible extra testing is needed once the WS-15 comes online. I doubt they would design one version for using AL-31 and another very different version for WS-15 which would take several more years of testing. It's just not how I would do things.

And also, if WS-15 could be ready by 2020, I could see them pushing the induction date back 2 years so they don't end up with an odd number of less capable and very different J-20s with AL-31 that they now have to train people to maintain... unless, they could swap the engine on existing jets to upgrade them to WS-15 J-20 standard.
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I'm not certain about that 40% number, but from what I can gather, yes, the fan diameter for the f100 engine is smaller. I don't think you could just stick a al-31 into an f-15 and expect optimal performance.

I'm skeptical they would install temporary structures into the inlet when space is a premium inside a plane, and structural modifications are expensive and time consuming. It seems like a needlessly complex approach, when they could just build another prototype with the changes (it might be less trouble and quicker, especially once they get production going). Even if that were the case though, they would still need to do testing with the new engine. Nothing gets around that step.

If they roll the J-20 into service before the WS-15 they will probably wait until they have enough planes to take the first batches with Al-31s for modification and upgrade. It seems unlikely that they would wait for more years just for the engine if everything else is ready, since once the J-20 goes into production they will need to immediately begin training and tactical development. Furthermore, by production they may have more advanced Al-31 variants that can provide more capability.
 
D

delft

Brigadier
latenlazy said:
Flying with intakes designed for another engine being suboptimal is precisely why I doubt that the current airframes have been optimized for the WS-15. If they intend on production before the WS-15, I don't think they would go with an unoptimized solution and wait for the untested one that's supposed to be more optimized to make their airframes whole. I'm sure they already have a redesign ready for the aft and the intake, but I'm also pretty certain that the intake geometry (if not external, than internal) and thus every structural element related to the engine will have to be changed, and those aren't trivial ones that can be done with a "plug and play" solution. Whatever changes will be needed to properly fit and utilize the WS-15 will probably need to be done on a future airframe, or else extensive modifications that could take a while would have to be done on a current one.

I myself once thought it would make sense for the solution to be plug and play, but the more I've looked into the complex needs of intake geometry and the tight tolerances for structural requirements, the less I believe that it could be that simple.
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It is not as if they now have to start redesigning J-20 to take the WS-15 engine. I understand the aircraft was designed for that engine then redesigned for the prototypes to take the J-31 engine.
 
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latenlazy

Brigadier
delft said:
It is not as if they now have to start redesigning J-20 to take the WS-15 engine. I understand the aircraft was designed for that engine then redesigned for the prototypes to take the J-31 engine.
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How do you design around an engine that isn't even finished testing yet?
 
S

Schumacher

Senior Member
latenlazy said:
How do you design around an engine that isn't even finished testing yet?
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I hope you're not suggesting the J20 team is isolated from the WS15 team and they don't share the designed dimensions and other critical parameters of the engine and air frame.
New jets, and other machinery for that matter, are designed and tested while the engines, or other components, are tested simultaneously all the time as long as the teams work together and the critical parameters are shared.
Maybe I have misunderstood you because it's not even funny that this needs to be pointed out.
 
manqiangrexue

manqiangrexue

Brigadier
Schumacher said:
I hope you're not suggesting the J20 team is isolated from the WS15 team and they don't share the designed dimensions and other critical parameters of the engine and air frame.
New jets, and other machinery for that matter, are designed and tested while the engines, or other components, are tested simultaneously all the time as long as the teams work together and the critical parameters are shared.
Maybe I have misunderstood you because it's not even funny that this needs to be pointed out.
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Yeah, you're right. Engines and their jets are often designed together. I'm pretty sure latenlazy was saying that even the WS-15 team doesn't know its final specs including max output or exact size before it's finished. They'll have a good ballpark, but while testing, they might need to optimize it by adding a thing here or making a new part, shifting something around, etc... that might slightly change its dimensions and space inside a jet needs to be very exact. I'm sure it'll present challenges but I think unless the fan blades get too long to fit the engine nacelle or the length is significantly increased, the engineers can tweek a solution. Also, a buffer zone was probably incorporated into their initial estimate so that adding an extra inch or 2 doesn't cause the whole project to come apart LOL
 
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latenlazy

Brigadier
Schumacher said:
I hope you're not suggesting the J20 team is isolated from the WS15 team and they don't share the designed dimensions and other critical parameters of the engine and air frame.
New jets, and other machinery for that matter, are designed and tested while the engines, or other components, are tested simultaneously all the time as long as the teams work together and the critical parameters are shared.
Maybe I have misunderstood you because it's not even funny that this needs to be pointed out.
Click to expand...
Not suggesting that at all, but there's only so much you can do while the engine is completing testing stages. The point I'm making is that it's unlikely for the current prototypes to have been built with the exact parameters of optimization for the WS-15 in mind, given that the engine only started testing (ignoring core testing) around the same time that the 201X series showed up. Perhaps you guys misunderstand what I mean by "optimization". The structural side of the equation is important, but only secondary to the real challenge, which is inlet aerodynamics. This goes back to the point about how S-ducts increase the complexity of geometric parameters.
 
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