PLA 6th generation fighter thread

[ashnole]

So far as the USAF 6th Gen fighter is concerned, the expected combat radius in clean/full-stealth configuration is somewhere around 1500-1800 nautical miles (2.5-3 times that of an F-22) with a 2.5-3 times greater CAP on-station time.

The NGAD is also going to fly with various unmanned wingmen with combat radii about 750-900 nautical miles greater than the NGAD itself.

The USN's 6th Gen will be obviously smaller than the USAF's because of CVN deck constraints and would be quite lucky to get a combat radius of even 1200 nautical miles in clean configuration.

 

[polati]

China needs to be working very actively on these 6th gen aircraft if it wants to catch up and eventually overtake the US. By settling with just producing large quantities of J-20, yes they'll be adequate for the next 10-20 years, but you don't want to always be playing the catch-up game by not investing in new platforms sooner.

 

[Blitzo]

These are the first two pages.

I've uploaded it here, so people can read it and download it.

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It's about variable cycle engines, which of course is very relevant to 6th gen applications. It's not about combined cycle engines, which is quite different.

 

[latenlazy]

I've uploaded it here, so people can read it and download it.

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It's about variable cycle engines, which of course is very relevant to 6th gen applications. It's not about combined cycle engines, which is quite different.

Oops. Definitely meant variable when I posted the article.

 

[Blitzo]

Oops. Definitely meant variable when I posted the article.

There are a few nice articles from relevant Chinese institutes, fully in English relating to the topic that are referenced too and able to be found in other places, with some pictures that are study specific.
In terms of literature, there's a fair bit out there, but of course the timing of these and how much real world development and testing they may have done may not necessarily sync up with when these articles would've been written. There's likely a fair bit they haven't published and kept quiet on deliberately, but we definitely have enough literature to say they're heavily looking into VCEs at minimum.


There's this one from 2021, which on my end can be fully accessed and I assume is just open access in general.

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Designing method of acceleration and deceleration control schedule for variable cycle engine
Linyuan JIA a b, Yuchun CHEN a, Ronghui CHENG b, Tian TAN a, Keran SONG a
School of Power and Energy, Northwestern Polytechnical University, Xi’an 710072, China
Aero-engine Corporation of China, Shenyang Engine Research Institute, Shenyang 110066, China

Abstract
Studies show that different geometries of a Variable Cycle Engine (VCE) can be adjusted during the transient stage of the engine operation to improve the engine performance. However, this improvement increases the complexity of the acceleration and deceleration control schedule. In order to resolve this problem, the Transient-state Reverse Method (TRM) is established in the present study based on the Steady-state Reverse Method (SRM) and the Virtual Power Extraction Method (VPEM). The state factors in the component-based engine performance models are replaced by variable geometry parameters to establish the TRM for a double bypass VCE. Obtained results are compared with the conventional component-based model from different aspects, including the accuracy and the convergence rate. The TRM is then employed to optimize the control schedule of a VCE. Obtained results show that the accuracy and the convergence rate of the proposed method are consistent with that of the conventional model. On the other hand, it is found that the new-model-optimized control schedules reduce the acceleration and deceleration time by 45% and 54%, respectively. Meanwhile, the surge margin of compressors, fuel–air ratio and the turbine inlet temperature maintained are within the acceptable criteria. It is concluded that the proposed TRM is a powerful method to design the acceleration and deceleration control schedule of the VCE.

And another more recent one from 2022 as well

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Flow control of double bypass variable cycle engine in modal transition
Haoying CHEN, Changpeng CAI, Jiayi LUO, Haibo ZHANG
Jiangsu Province Key Laboratory of Aerospace Power System, College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Abstract
To study the change mechanism and the control of the variable cycle engine in the process of modal transition, a variable cycle engine model based on component level characteristics is established. The two-dimensional CFD technology is used to simulate the influence of mode selection valve rotation on the engine flow field, which improves the accuracy of the model. Furthermore, the constant flow control plan is proposed in the modal transition process to reduce the engine installed drag. The constant flow control plan adopts the augmentation linear quadratic regulator control method. Simulation results indicate that the control method is able to effectively control the bypass ratio and demand flow of the variable cycle engine, and make the engine transform smoothly, which ensures the stable operation of the engine in modal transition and the constant demand flow of the engine.

And a few older ones:

2016:

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A Study on Combined Variable Geometries Regulation of Adaptive Cycle Engine during Throttling
by Ya Lyu 1,2,Hailong Tang 1,2 andMin Chen 1,2,*
1
School of Energy and Power Engineering, Beihang University, Beijing 100191, China
2
Collaborative Innovation Center of Advanced Aero-engine, Beijing 100191, China

Abstract
The most remarkable variable cycle characteristic of the variable cycle engine (VCE) is that it keeps airflow almost constant during subsonic cruise throttling by modulating variable geometries, which can efficiently decrease spillage drag and increase installed thrust. One of the most critical challenges for the modulation lies in completely maintaining airflow, as well as avoiding specific fuel consumption (SFC) degradation during throttling. This has resulted in a need to investigate the modulation regulation of the adaptive cycle engine (ACE) which is a new concept for VCE and has greater potential for flexibly modulating airflow and pressure ratio. Thus, the aim of this paper is to study the variable geometries’ modulation schedule of ACE in maintaining airflow during throttling. A configuration of an ACE concept and its modeling study are first put forward. Then, the control schedule is researched via the combination of sensibility analysis and basic working principle instead of optimizing them directly. Results show that when the net thrust decreases from 100% to about 55% during subsonic cruise and to 32% during the supersonic cruise, the demand airflow of the engine is kept almost constant, which greatly improves the installed performance during throttling.

2016/17:

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Matching mechanism analysis on an adaptive cycle engine
Zheng Junchao, Chen Min, Tang Hailong
School of Energy and Power Engineering, Beihang University, Beijing 100083, China

Abstract
As a novel aero-engine concept, adaptive cycle aero-engines (ACEs) are attracting wide attention in the international aviation industry due to their potential superior task adaptability along a wide flight regime. However, this superior task adaptability can only be demonstrated through proper combined engine control schedule design. It has resulted in an urgent need to investigate the effect of each variable geometry modulation on engine performance and stability. Thus, the aim of this paper is to predict and discuss the effect of each variable geometry modulation on the matching relationship between engine components as well as the overall engine performance at different operating modes, on the basis of a newly developed nonlinear component-based ACE performance model. Results show that at all four working modes, turning down the high pressure compressor variable stator vane, the low pressure turbine variable nozzle, the nozzle throat area, and turning up the core-driven fan stage variable stator vane, the high pressure turbine variable nozzle can increase the thrust at the expense of a higher high pressure turbine inlet total temperature. However, the influences of these adjustments on the trends of various engine components’ working points and working lines as well as the ratio of the rotation speed difference are different from each other. The above results provide valuable guidance and advice for engine combined control schedule design.

 

[AndrewS]

So far as the USAF 6th Gen fighter is concerned, the expected combat radius in clean/full-stealth configuration is somewhere around 1500-1800 nautical miles (2.5-3 times that of an F-22) with a 2.5-3 times greater CAP on-station time.

The NGAD is also going to fly with various unmanned wingmen with combat radii about 750-900 nautical miles greater than the NGAD itself.

The USN's 6th Gen will be obviously smaller than the USAF's because of CVN deck constraints and would be quite lucky to get a combat radius of even 1200 nautical miles in clean configuration.

A combat radius for the USAF NGAD of 1500-1800 nautical miles is the 3000km distance from Guam to Mainland China.

So when China starts fielding its own 6th Gen NGAD equivalent, the US airbases on Guam and the rest of the Second Island Chain would likely be overwhelmed.

---

My guess is that US NGADs would be operating from airbases in Alaska, Hawaii? or Australia.
And they would be accompanied by airborne refuelling tankers till they reach Guam, Japan or Philippines.

So in a 2030-2040 timeframe, the military balance in the Western Pacific would continue to shift in China's favour.

 

[ACuriousPLAFan]

The USN's 6th Gen will be obviously smaller than the USAF's because of CVN deck constraints and would be quite lucky to get a combat radius of even 1200 nautical miles in clean configuration.

Wondering if this meant that in order to maintain/enhance the edge of carrier-based fighters on the high seas (and remain competetive to land-based counterparts), some kind of major changes have to be made WRT how we design aircraft carriers and carrier-based fighters going forward?

- Aircraft carriers with overall larger size and displacement? (Nimitz and Ford displaces ~105k tons)
- Larger flight deck & hangar deck plus related arrangements?
- Wider spacing between bow catapults? Or tandem-arranged launch position for catapults (akin to the waist catapults on US carriers)?
- Larger elevator decks?
- Additionally/Or, with 6th-gen fighters having more-than-one folding on each wing for smaller storage space onboard? (Current F/A-18s, F-35Cs and J-15s only fold once on each wing.)

 

[BoraTas]

Wondering if this meant that in order to maintain/enhance the edge of carrier-based fighters on the high seas (and remain competetive to land-based counterparts), some kind of major changes have to be made WRT how we design aircraft carriers and carrier-based fighters going forward?

- Aircraft carriers with overall larger size and displacement? (Nimitz and Ford displaces ~105k tons)
- Larger flight deck & hangar deck plus related arrangements?
- Wider spacing between bow catapults? Or tandem-arranged launch position for catapults (akin to the waist catapults on US carriers)?
- Larger elevator decks?
- Additionally/Or, with 6th-gen fighters having more-than-one folding on each wing for smaller storage space onboard? (Current F/A-18s, F-35Cs and J-15s only fold once on each wing.)

This is a bit off-topic but I will still write as the topic warrants it.

I think Chinese carriers will grow way beyond 100,000 tonnes. Aviation simply loves scale because a lot of the facilities needed are very expensive. And increasing tonnes/aircraft is an easy way to make up for the procedural differences between USN and PLAN. USN carriers are stuck at 100,000 because of infrastructural reasons, not military. You max the Panama Channel and the biggest US drydock at that point. These don't hold true for China.

And yes, it would enable a bigger naval 6th gen.

 

[HighGround]

This is a bit off-topic but I will still write as the topic warrants it.

I think Chinese carriers will grow way beyond 100,000 tonnes. Aviation simply loves scale because a lot of the facilities needed are very expensive. And increasing tonnes/aircraft is an easy way to make up for the procedural differences between USN and PLAN. USN carriers are stuck at 100,000 because of infrastructural reasons, not military. You max the Panama Channel and the biggest US drydock at that point. These don't hold true for China.

And yes, it would enable a bigger naval 6th gen.

How big? The F-35 is pretty small, but an F-14 is fairly sizeable.

 

[antiterror13]

This is a bit off-topic but I will still write as the topic warrants it.

I think Chinese carriers will grow way beyond 100,000 tonnes. Aviation simply loves scale because a lot of the facilities needed are very expensive. And increasing tonnes/aircraft is an easy way to make up for the procedural differences between USN and PLAN. USN carriers are stuck at 100,000 because of infrastructural reasons, not military. You max the Panama Channel and the biggest US drydock at that point. These don't hold true for China.

And yes, it would enable a bigger naval 6th gen.

Interesting idea, I have been thinking the same. I am not a naval engineer, so not sure whether it is possible to build let's say 150,000 tonnes carrier?. I read long time ago that the US navy did some analysis that 100k carrier is the optimum one, beyond that wouldn't be optimum