Chinese Engine Development

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ACuriousPLAFan

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Turns out we might actually be onto something here...

Interesting find and development, by @爱若丰狂SOYO历 on Weibo.

China Aero Engine Sichuan Gas Turbine Research Institute:
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Research on Matching Analysis Method for Large-Offset S-Duct Inlet and High-Bypass-Ratio Turbofan Engine & Development of Aerodynamic Stability Evaluation Technology – Procurement Announcement (Re-issued)
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GpCD0gwbIAAguhc.jpeg

High-bypass turbofan with offset S-duct inlet... Which aircraft would be using such a design? Hmm...
 
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ACuriousPLAFan

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Registered Member
Deino said:
But a high-bypass engine in the H20?
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sunnymaxi said:
they didn't mention anything related bomber or other application.

Stealth bomber requires Medium/low bypass ratio engines.
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Well, here's the question - Is the WS-18 a medium-bypass engine or a high-bypass engine?

Firstly, if the WS-18 is indeed a carbon copy of the D-30KP-2 with no changes/improvements to speak of, then it will have a fan diameter of 1.45 meters and a bypass ratio of 5.21 (plus thrust of ~117 kN).

Meanwhile, there's the CFM56 family which is considered high-bypass turbofan engines, with fan diameters and bypass ratios ranging from 1.55 meters and 5.1 (plus thrust of ~105 kN) to 1.84 meters and 6.5 (plus thrust of ~151 kN), respectively.

On the other hand, the F118, considered as a medium-bypass turbofan engine and powers the B-2 Spirit has a fan diameter of 1.18 meters and a bypass ratio of 1.3 (plus thrust of ~85 kN).

Plus, as a matter of fact - Isn't there an academic paper from 2020 on the avenue of swapping initial, older engines with thrust and fuel consumption rate that is similar to the D-30KP-2/WS-18 engines for newer, more fuel-efficient engines on a large, VLO flying wing warplane with listed stats that are largely similar to the B-2 while attempting to avoid changing the shaping of the inlet and the fuselage of the warplane itself? It was posted in the H-20 thread in late-November last year, as follows:

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ACuriousPLAFan said:
To provide some context for the academic paper.

According to the original poster
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, roughly translated:

1. The general stats of the warplane mentioned in the paper (168-ton designed MTOW, 78.5-ton empty weight, 72.2-ton fuel weight, 17-ton+0.2-ton payload capacity with a combat radius of 4500 kilometers) looks to be close/roughly similar to that of the B-2 Spirit strategic bomber of the USAF.
2. The required bench thrust given in the paper is 114.22kN, but the warplane seems to already have a new, target engine (in the pipeline?).
3. According to the paper, the original engines slated for the warplane has a cruising fuel consumption rate of 0.7kg/(kgf·h), and the cruising fuel consumption rate of D-30KP-2/WS-18 officially given by Saturn NPO is 0.705kg/(kgf·h). Both engine models seem to be comparable to one another.
4. The new, target engines meant to replace the original engines are stated to have a cruising fuel consumption rate of 0.0679kg/(N·h), which is equal to 0.665kg/(kgf·h).
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ACuriousPLAFan said:
Possible objectives of the academic paper in question:

1. The warplane was to be powered by D-30KP-2/WS-18 at the beginning of the design, and they have already considered to replace them with new, target engines later on.
2. The paper discusses the methods of determining the performance parameters of the new, target engines without significantly altering the structure (of the warplane).
3. In fact, one major contribution of the paper is to explore the avenue of changing the engines without redesigning/reconfiguring the inlets and nozzles of the warplane.
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So I suppose there are actually more things to consider, yeah?
 
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OppositeDay

Senior Member
Registered Member
Encyclopedia Britannica says anything below 4 and above 2 BPR is considered medium bypass and anything above 5 is considered high bypass. So I guess between 4 and 5 is a kind of grey area?

But realistically I think people working on an engine with greater than 4 BPR for a bomber will definitely call it high bypass because it sounds more innovative - bombers with medium bypass engines are dime a dozen.
 
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ACuriousPLAFan

Brigadier
Registered Member
Let's put things into perspective.

If the H-20 really is meant to employ turbofan engines of the D-39KP-2/WS-18-category (whether than be WS-18 or a brand new WS-XX model), and assuming that the H-20 sports the same number of engines as the B-2 - Then it is reasonable to expect that the H-20 would be bigger and heavier than the B-2, due to the greater cumulative thrust available to the H-20 compared to the B-2 (468 kN versus 340 kN).

In addition, there are the benefits of fuel efficiency as well. Namely, the larger the bypass ratio, the more fuel efficient the engines are. This translates to:
1. Increased range and combat radius; and/or
2. Increased airframe volume available for internal weapons bays (IWBs), fuel tanks, sensors, avionics and computing systems.

As for the difference in fan diameters between the F118 and the D-30KP-2/WS-18 - That's about one 30-centimeter/12-inch ruler, for visualization purpose. Moreover, if the H-20 is indeed larger than the B-2 (which I've heard rumors of this being the case), then there should be enough airframe volume to embed the engines, plus sufficient forward cross-sectional area of the aircraft body to hide the engine fan blades.

Otherwise, there could be some compromises as a result - However, if the PLAAF higher-ups deem the tradeoff from such downside is worth the overall performance and capability of the H-20, then it'll certainly get the green light.

TL; DR -
1. High-bypass engines on a large, flying-wing VLO platform shouldn't be too much of a problem, provided that they can be designed and engineered properly; and
2. The aforementioned high-bypass engine very likely isn't the same as the ones we are typically associated with (e.g. WS-20, CJ1000A, CJ2000 etc).


Side note: While lacking rather conclusive/authoritative information for the time being, I don't think we should be surprised should the B-21 be able to achieve long enough ranges, if not comparable to the B-2, provided the claim of the B-21 being powered by PW9000 engines with bypass ratio of ~4 is accurate, compared to the ~1.3 bypass ratio of the F118 engines.
 
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