Chinese Engine Development

latenlazy said:

Obviously you would need material enhancements to maintain the same level of mechanical performance for a larger engine, but my point is that with a bigger engine you can get more performance with less demanding mechanical performance.

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I think that only works with reciprocating engines where heat transfer across the cylinder walls is a substantial loss factor, so that the cube-square relationship of cylinder volume to wall area improves with size. With gas turbines the combustion chamber is proportionately tiny and wall heat loss is (relatively speaking) negligible, to the point that the M1 gas turbine is air cooled where the equivalent Leopard 2 diesel requires water-cooling, despite better efficiency (if you were to compare exhaust temperature though...).

Certainly for the fairly narrow range of scale we're dealing with here the effect would be insignificant.

Tirdent said:

I think that only works with reciprocating engines where heat transfer across the cylinder walls is a substantial loss factor, so that the cube-square relationship of cylinder volume to wall area improves with size. With gas turbines the combustion chamber is proportionately tiny and wall heat loss is (relatively speaking) negligible, to the point that the M1 gas turbine is air cooled where the equivalent Leopard 2 diesel requires water-cooling, despite better efficiency (if you were to compare exhaust temperature though...).

Certainly for the fairly narrow range of scale we're dealing with here the effect would be insignificant.

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Probably, but so would the difference in mechanical strain. The original comment was an offhand one meant to make a general abstract point about how suitable the performance of a smaller engine would be for judging overall technological capability. I wasn’t actually suggesting that anyone should or would upsize or downsize one engine to meet a different weight class.

From the thread where he mentioned the weight of the J-20, gongke101 something (what?) about the stages and pressure ratio of the WS-15.
Q:

Engineering is big, some people say that WS15 has two configurations of 3+6+1+1 and 2+5+1+1. Is this statement reliable?

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gongke101:

Not reliable, in the northeast, some people think that the high pressure is less than 7 and the pressure ratio is less than 30 is the heresy.

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工科大，有人说WS15有3+6+1+1和2+5+1+1两个构型。这个说法靠谱吗？
不靠谱，东北方面有人认为高压少于7级、压比低于30左右就是异端。

Klon said:

From the thread where he mentioned the weight of the J-20, gongke101

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something (what?) about the stages and pressure ratio of the WS-15.
Q:
gongke101:
工科大，有人说WS15有3+6+1+1和2+5+1+1两个构型。这个说法靠谱吗？
不靠谱，东北方面有人认为高压少于7级、压比低于30左右就是异端。

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工科大 shouldn’t be translated to big engineering here, but big Gongke. The person asking him the question typed the characters for his handle instead of the pinyin. Specifically they’re asking if it’s true that there are actually two different WS-15 engines, one that’s a 3 stage fan, 6 stage hpc, 1 stage hpt, 1 stage lpt, and one that’s 2-5-1-1. Gongke replied that this rumor is unreliable. From what he’s heard from the Northeast (implying Shenyang I think) any rumour where the HPC is below 7 stages and the overall pressure ratio isn’t less than 30 shouldn’t be trusted.

FWIW, I should probably add here that I don’t completely trust Gongke for a lot of stuff. The guy has some major beef with SAC and the 606th institute, and he always seems a bit careless with information he gathers from hearsay. Still, I suppose in this information sparse hobby he’s a goldmine for discussions. We’ll see though.

Thanks. Most of it was pretty clear; I was wondering about the last part.

latenlazy said:

From what he’s heard from the Northeast (implying Shenyang I think) any rumour where the HPC is below 7 stages and the overall pressure ratio isn’t less than 30 shouldn’t be trusted.

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Should it be is? At least that's what it looks like from the machine translation.

This also apparently contradicts the 6 stage information from four pages back.

工科大 shouldn’t be translated to big engineering here, but big Gongke. The person asking him the question typed the characters for his handle instead of the pinyin.

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I know it's referring to him, I just don't edit the translations.

Klon said:

Thanks. Most of it was pretty clear; I was wondering about the last part.


Should it be is? At least that's what it looks like from the machine translation.

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Oops. Yeah, I meant “is”. Originally I wrote “he’s saying the OPR isn’t less than 30” and missed that negative when I reworded.

Just reiterating to be completely clear, Gongke is saying that from what he’s heard the OPR is above 30.

This also apparently contradicts the 6 stage information from four pages back.

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Not just four pages back, but 6 stages is something we’ve been hearing for years now, from other sources we’ve deemed to be reliable (like maya). That’s one of many reasons why I think this bit of information is suspect, and why I added some personal thoughts about how reliable I think Gongke’s comments can be. It seems very apparent, at least to me, that a lot of his comments are charged with corporate politics, and it’s not beyond people from Chinese industry to use public outlets as a way to slander and undermine groups and firms they don’t get along with. I’m not saying that what he’s saying can be categorically discounted, but that we should be particularly careful with information that comes from him.

I know it's referring to him, I just don't edit the translations.

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Just clarifying in case anyone was confused.

Maybe the 7 is a typo? The key is located right next to 6, after all.

Not that I've ever made that kind of mistake

Tirdent said:

Maybe the 7 is a typo? The key is located right next to 6, after all.

Not that I've ever made that kind of mistake

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He’s refuting a rumour that there was two designs, one with a 6 stage HPC and one with a 5 stage HPC, and he’s saying that neither are true, so I’m pretty sure he means it when he says no less than 7 stages.

I don't know about your typos, but the very nature of mine is that they end up making me say something I do not in fact mean Isn't the only reason to believe that he is disagreeing with both options the assumption that the 7 is deliberate?

Alternatively (forgive me if this is a stupid suggestion, since I'm completely at the mercy of machine translation with Mandarin), is it possible that he isn't talking about the stage count at all but HPC *pressure ratio*? Implying the 2+5 LP+HP compressor configuration isn't realistic because it would in his view preclude the HPC and overall pressure ratios (of 7+ and 30, respectively) claimed by the grape vine, but making no statement on the 3+6 layout at all?

Tirdent said:

I don't know about your typos, but the very nature of mine is that they end up making me say something I do not in fact mean

Alternatively (forgive me if this is a stupid suggestion, since I'm completely at the mercy of machine translation with Mandarin), is it possible that he isn't talking about the stage count at all but HPC *pressure ratio*? Implying the 2+5 LP+HP compressor configuration isn't realistic because it would in his view preclude the HPC and overall pressure ratios (of 7+ and 30, respectively) claimed by the grape vine, but making no statement on the 3+6 layout at all?

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Nope. He was pretty clear in his phrasing. Though, after rereading the comment, I think there may be some wiggle in terms of what he’s saying, and I might have fudged the original framing of the reply a bit. Let me do a more precise line by line translation (and of course, corrections by other members are always welcome).

工科大，有人说WS15有3+6+1+1和2+5+1+1两个构型。这个说法靠谱吗？
Gongke, some people say the WS-15 has two configurations, 3+6+1+1 and 2+5+1+1. Is this reliable?


不靠谱，东北方面有人认为高压少于7级、压比低于30左右就是异端。
Not reliable, from the standpoint of the Northeast (Shenyang) there are people who think HPC under 7 stages, pressure ratio below 30, is heresy.

When I reread it I realized there’s a small chance that Gongke is playing loose here in terms of couching his reply not so much as a matter of fact, but as a matter of the opinions of the people who are working on the engine.

This ought to highlight my caveats about information from Gongke. Everything Gongke knows about the WS-15 is from hearsay. He works at a different firm (that as I’ve noted earlier has a bad history with the firm responsible for the WS-15), and is not even peripheral to the project. Take it as you will.