I was referring to the fact that WS-10 has a higher by-pass ratio compared to WS-15. I guess it comes down to a trade-off between range and payload.
Future PLA combat aircraft composition
- Thread starter Totoro
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F135 has a relatively high bypass ratio. WS-15 is more like a Chinese F119. For H-20, you will have to increase its bypass ratio by quite a lot, which may not make a good starting point. Why not just start with WS-10?
I wasn't aware that we had any credible numbers for what WS-10 and WS-15's bypass ratios will end up being, respectively.
Please re-read my post where I mention the idea of a "non AB WS-15".
I wrote "- Longer term, if a new H-20 variant or upgrade emerges, a non-AB WS-15 may prove very desirable"
I thought the phrasing of the sentence was pretty obvious, but I'll elaborate on it so there's no misunderstanding, ahem:
"H-20 is of course expected to be powered by a non afterburning WS-10 variant as the initial intended powerplant, and will likely be produced with them for a good long period. This is all widely accepted information. However, in the longer term (i.e.: a decade or more after H-20 begins production), there is a possibility that an engine upgrade for H-20 might be seen as desirable, in which case a non afterburning variant of WS-15 to replace the non afterburning variant of WS-10, would be a good candidate."
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I don't have references, but from what I read, WS-15 has lower by-pass ratio compared to WS-10.
The point isn't to compare an airliner engine to a fighter jet turbofan, but to compare bypass ratios within the range used by fighter jet turbofans. Some variants of the F100 have bypass ratios as high as 0.6 (like the F135), while the F119 has a bypass ratio of 0.3. If we buy the hypothesis that the WS-15 is optimized for high-altitude supercruise, we can expect it to have a similarly low bypass ratio.
A subsonic bomber is speed-limited to less than Mach 1 no matter how powerful the engine running it is. The only advantage I can see to installing a hotter burning engine like the WS-15 is better Carnot efficiency and therefore better combat range. I can imagine a higher bypass variant of the WS-15 eventually being installed into the H-20 (probably past the mid 2030s) but not the one intended to be installed on the J-20 (with the afterburner deleted).
Looking at the primary design goal of the J-20 (air superiority), it's very reasonable to infer that the WS-15 is optimized along the lines of the F119.
I'm sorry but I feel like this discussion is sort of missing the forest for the trees here -- in the context of talking about the demand for WS-15s (i.e.: production of all WS-15 variants going into the future period that a land based J-XY/35 variant will be getting produced), whether WS-15 has a slightly higher or lower bypass ratio than WS-10 or F119 or F135, does not particularly change the statement of "Longer term, if a new H-20 variant or upgrade emerges, a non-AB WS-15 may prove very desirable".
If one wants to add a slightly higher bypass ratio to the list of modifications for such a WS-15 variant, that's fine.
However, my point is that the WS-15 engine would still be the basis of it, and if such a variant does end up happening it sill just add to the overall a high degree of demand for WS-15 engines (on top of the other guaranteed/more likely applications, namely J-20s, PLA 6th gens) going forwards.
This is all in turn on the suggestion by reservoir dogs that a variant of WS-19 being used for H-20s, which is strange. Frankly the only reason I entertain the idea of a WS-15 variant for H-20s in the future, is because WS-19 and WS-15, the WS-15 is the one which is far more likely to have any future prospect as having applications for H-20.
That is just adding another layer of complexity to the discussion, because it leads to questions like:
1. Will the J-20 only be produced for the PLAAF, or will they also in future be produced for land based PLANAF?
2. Will there even be a land based PLANAF into the medium and long term future, or will they wholly transition and expand to a carrier based airwing and divest their land based fighter capabilities to the PLAAF?
3. Given how small the current land based PLANAF fighter fleet is, would development of a land based J-XY/35 make sense for them if the PLAAF wasn't also committed to buying a large number?
Etc.
Given all that, I think it is much simpler for us to talk about the land based J-XY/35 variant as one for the PLA as a whole, where the primary customer is the PLAAF but also possibly land based PLANAF to a degree. Without it, the idea of a land based J-XY/35 being a land based PLANAF exclusive doesn't pass the smell test to me.
It's nothing to do with whether it has afterburner or not. J-20 is designed for supercruise (at higher altitude), which favors a lower bypass ratio similar to that of F119. It's reasonable to make a wild guess that WS15 will be such an engine (bypass ratio around 0.3). As for WS10, I would be very surprised if its bypass ratio deviates too much from the range 0.5-0.8.
Subsonic aircrafts like H-20 need a relative high bypass ratio for better thrust and fuel efficiency, so WS10 could actually be the better starting point.
I have already established that the H-20 will be powered by a non afterburning WS-10 variant.
Here:
Here:
And here:
This entire hypothetical discussion about a future potential application of WS-15 variants for future H-20 production is as a successor to the H-20's powerplant of non afterburning WS-10.
So I'm not sure why you keep saying "WS-10 could actually be a better starting point" -- because I've already written multiple times that the H-20 is going to be powered by a WS-10 variant as its initial intended powerplant.