Chinese Engine Development

Tirdent

Junior Member
Registered Member
I have some screen captures of a TV report that I cannot locate, so I cannot judge its credibility. Does anyone have a link to the video? The captioning and Weibo poster's summary state the following:
- The titanium-aluminum alloy engine blades developed by the Institute of Metal Research of the Chinese Academy of Sciences will be used in the CJ1000 turbofan destined for C919.

Nice! This would seem to confirm that the statement about the engine not having TiAl blades did apply only to the (first) demonstrator, while the production version is planned to have this technology. Makes sense, it seemed strange for the press release to emphasize the fact that prototype did not have hollow LPT blades, if not to make the point that the final product would. That means the technology underlying the CJ-1000A will ultimately become practically identical to the Russian PD-14, although the engine architectures and cycles have some notable differences. I'll take this opportunity to give my two cents on ougoah's earlier question:

The WS-20 may not be designed for those commercial demands but is the CJ-1000A somewhat efficient and competitive? Not to mention, safe and reliable enough for commercial?

We will know that it meets safety standards when it gets certified (preferably also outside China) and final proof of reliability is only in regular commercial operation of an engine.

In terms of efficiency, the available specs suggest that the CJ-1000A should do ok, with slightly higher BPR and OPR than the PD-14 resulting in a lower SFC. But SFC is a purely engine thrust specific measure, it does not account for the possibility that one engine might necessitate higher thrust settings due to higher weight and drag when actually installed on the aircraft than another in an otherwise identical scenario. This is where I have some reservations about it, I suspect it will turn out to be a very heavy engine - potentially heavier even than the LEAP-1C (which is already heavier than the PW1100G & PD-14 by a not insignificant margin). It seems to me that ACAE is attempting to achieve as close a copy of the LEAP-1C architecture and cycle as possible, without however having all of the technological building blocks necessary to execute such a design without further weight penalties.

By contrast, the Russians appeared to realize that aiming for the same BPR & SFC as the PW1100G and LEAP-1A would require a number of solutions which they considered too immature in their industry, namely composite fan blades and a composite fan case. As you increase BPR, fan diameter increases, which means longer and heavier fan blades for a given manufacturing method which in turn requires a larger and beefier fan case to contain the blade out contingency. There comes a point where the weight of of the fan and associated structure eats up the benefits of higher BPR. At the aircraft level anyway - looking at the engine in isolation on a test stand, the more BPR the merrier! So the PD-14 seems to be the result of an attempt to design the optimum engine achievable within the technology available, while the CJ-1000A (based on very similar technology over all) might be trying too hard for its own good to be a LEAP-1C.
 

reservior dogs

Junior Member
Registered Member
Nice! This would seem to confirm that the statement about the engine not having TiAl blades did apply only to the (first) demonstrator, while the production version is planned to have this technology. Makes sense, it seemed strange for the press release to emphasize the fact that prototype did not have hollow LPT blades, if not to make the point that the final product would. That means the technology underlying the CJ-1000A will ultimately become practically identical to the Russian PD-14, although the engine architectures and cycles have some notable differences. I'll take this opportunity to give my two cents on ougoah's earlier question:



We will know that it meets safety standards when it gets certified (preferably also outside China) and final proof of reliability is only in regular commercial operation of an engine.

In terms of efficiency, the available specs suggest that the CJ-1000A should do ok, with slightly higher BPR and OPR than the PD-14 resulting in a lower SFC. But SFC is a purely engine thrust specific measure, it does not account for the possibility that one engine might necessitate higher thrust settings due to higher weight and drag when actually installed on the aircraft than another in an otherwise identical scenario. This is where I have some reservations about it, I suspect it will turn out to be a very heavy engine - potentially heavier even than the LEAP-1C (which is already heavier than the PW1100G & PD-14 by a not insignificant margin). It seems to me that ACAE is attempting to achieve as close a copy of the LEAP-1C architecture and cycle as possible, without however having all of the technological building blocks necessary to execute such a design without further weight penalties.

By contrast, the Russians appeared to realize that aiming for the same BPR & SFC as the PW1100G and LEAP-1A would require a number of solutions which they considered too immature in their industry, namely composite fan blades and a composite fan case. As you increase BPR, fan diameter increases, which means longer and heavier fan blades for a given manufacturing method which in turn requires a larger and beefier fan case to contain the blade out contingency. There comes a point where the weight of of the fan and associated structure eats up the benefits of higher BPR. At the aircraft level anyway - looking at the engine in isolation on a test stand, the more BPR the merrier! So the PD-14 seems to be the result of an attempt to design the optimum engine achievable within the technology available, while the CJ-1000A (based on very similar technology over all) might be trying too hard for its own good to be a LEAP-1C.
How difficult it it to replace the components with the composite counterpart once the material is ready? Is it almost like re-starting then engine design?
 

gelgoog

Brigadier
Registered Member
How difficult it it to replace the components with the composite counterpart once the material is ready? Is it almost like re-starting then engine design?

You'll basically have to redesign the low pressure sections of the engine and the external casing of the engine. The reason being that you can use much larger fans with composites. In fact the larger the fan diameter the more performance benefit you will see with composites.
 

reservior dogs

Junior Member
Registered Member
You'll basically have to redesign the low pressure sections of the engine and the external casing of the engine. The reason being that you can use much larger fans with composites. In fact the larger the fan diameter the more performance benefit you will see with composites.
Thanks Gelgoog.
 

Orthan

Senior Member
What you and everybody else found about WS-15 is not spec from any official or designer's source, the "likely specs of Izd.30" means it is not official either. This simply means that nobody knows, all being talked about are perhaps and maybes.

I think it is better that we say "we know nothing" than speculation about any of the engines.
It seems that stating that "we know nothing" is the most accurate statement when talking about the WS-15. It seems that no one knows for certain, how along it is in development, if it has been tested inflight. It could even be in "development hell". The fact that J-20 is now flying with WS-10 doesnt help to dispel that idea.
 

taxiya

Brigadier
Registered Member
It seems that stating that "we know nothing" is the most accurate statement when talking about the WS-15. It seems that no one knows for certain, how along it is in development, if it has been tested inflight. It could even be in "development hell". The fact that J-20 is now flying with WS-10 doesnt help to dispel that idea.
The "we know nothing" in my original post has a context which was against the "over speculation". In fact we do know something about WS-15. There has been report of "engine casing production plan (years) for XX-15 in the number of low two digits" which certainly was about WS-15 that is in late development, not "hell" at all. J-20 using WS-10 says nothing certain of WS-15 either, because we do not know if this was anticipated and planed at the beginning of J-20 program. If it was known by the program that WS-15 won't be ready by 2020, then there is nothing wrong in WS-15's progress. And nobody has ever said about WS-15 being ready in 2020, but rather rumor says 2025.

So to conclude, my "we know nothing" should be precisely stated as "do not easily conclude anything around WS-15". This applies to both sides of overly positive and negative. I hope this time, I got my statement water-tight.
 

Tirdent

Junior Member
Registered Member
How difficult it it to replace the components with the composite counterpart once the material is ready? Is it almost like re-starting then engine design?

Once developed and tested, you could simply swap them out and leave it at that, this would give you a small weight saving with little impact on other parts of the engine. Conventionally, it would be more beneficial to take advantage of the opportunity to increase fan size and go for a higher bypass ratio, though. As gelgoog says, that involves revising the entire low pressure spool including shaft and low pressure turbine as well as the nacelle to accommodate the larger diameter.

To illustrate, the Russians have mounted drop-in replacement composite blades on the PD-14 as a test for later use on the PD-35 widebody engine and the expected weight saving is only 20-30kg. This is for an engine weighing ~3t with a BPR of 8.5 (a reduction of just 1%), but on the ~8t PD-35 with a BPR of ~11 it is estimated to save around 400kg (5%!!!) over a PD-14-style hollow titanium fan! So there is a strong incentive to increase bypass ratio for lower SFC with composite materials, even to the point of accepting a net increase in engine weight.

With the CJ-1000A however, the original engine basically has the BPR increase already built in (which is precisely why I think it will turn out overweight). So in this specific example we'd be talking about a simple drop-in, with a much larger than usual weight benefit (at a guess far in excess of 100kg, if you also include a composite fan case). At the aircraft level (with two engines), that's at least 3 additional fare-paying passengers' worth at no range penalty.
 

latenlazy

Brigadier
With the CJ-1000A however, the original engine basically has the BPR increase already built in (which is precisely why I think it will turn out overweight). So in this specific example we'd be talking about a simple drop-in, with a much larger than usual weight benefit (at a guess far in excess of 100kg, if you also include a composite fan case). At the aircraft level (with two engines), that's at least 3 additional fare-paying passengers' worth at no range penalty.
What if they built in the BPR increases because they’re already looking at more weight saving components and materials?
 

Tirdent

Junior Member
Registered Member
That is quite likely the rationale, but if they don't mount composite fan blades on an actual CJ-1000A soon, chances are it will have to be introduced on an improved variant after service entry with metal blades. The very fact that ACAE took the time to develop hollow titanium blade technology also indicates a composite fan was not considered mature enough to meet the desired schedule. Otherwise they'd have simply mounted conventional solid blades on the non-flying demonstrators and skipped straight to a CFRP solution at a later stage and for production (as is obviously being done with the TiAl LPT).
 
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