Chinese next generation military engines

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Jacky

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@F119Doctor Sir, I found information in the X, which seems the Chinese ACE demonstrator. But It has a unique structure with a combustion chamber inside the 2nd duct. This combustion chamber will be activated when the aircraft requires high thrust, such as during high Mach flight at low/high altitude and supersonic cruise. And according to the image, the combustion chamber inside the 2nd duct can increase the temperature in front of the low-pressure turbine.

Compared to the technologies of XA100/101/102/103, has China's technology achieved the same goal in a simpler way? QQ_1762092442370.png G4vRFLtbgAASZTF.jpg G4vRFOVawAAw5Jb.jpg G4vRFP7bgAEcGxe.jpg
 
Jacky said:
But It has a unique structure with a combustion chamber inside the 2nd duct.

Compared to the technologies of XA100/101/102/103, has China's technology achieved the same goal in a simpler way?
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That second combustion chamber probably gives greater thrust , but if anything this seems more complex and riskyt than just leaving it as a cold third stream.

The ppt slide says 27.6% increased unit thrust and 33% thrust per capture area on the ground and 47% increased unit thrust and 37% lower fuel comsumption in the high altitude test chamber. These terms arent the same measurement types as the stated thrust and fuel consumption numbers for the XA100s but I wouldn't know how to make meaning out of these numbers anyway.
 
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Not sure where to actually post this because there doesn't seem to be a Chinese engine thread, but they recently unveiled an interesting VCE with a variable combustion chamber instead of the normal variable fan route by the US. Some specs are in ground testing the engine had 27.6 percent more specific thrust and 33 percent more thrust per frontal area while in high-altitude, high-speed conditions the engine had approximately 47 percent more specific thrust and 37.5 percent less fuel consumption than an engine with a traditional afterburner. They then proceeded to show a few slides about high-speed, high-altitude research, so presumably this engine is meant for high altitude and high-speed regime.
 
This is an interesting concept from what I can understand, but I believe this is intended to be high Mach solution for speeds in excess of M3, not the subsonic cruise efficiency / high specific impulse supercruise variable bypass concepts in the XA100-103 engines.

It appears that they are addressing the issue of airflow turndown that occurs at elevated Mach numbers as the inlet temperatures increase while the engine reaches it rotor speed and turbine inlet temperature limits. Further increases in inlet temperature reduces the corrected rotor speed, reducing airflow and moving the compressor towards rear end choked flow and front end stall. The single rotor J58 cambered its inlet guide vanes and opened its bleed bypass at M2.2 to unload the front end of the compressor and capture the bypassed air for use in the augmentor section. You can see the J58 referenced as the middle line on the two graphs.

The pictured concept combining some of the architecture of the YF120 variable bypass engine with the J58 bleed bypass from the 2nd stage of the high compressor on a low bypass 2 spool turbofan, and adding duct burning and reintroducing the heated bleed bypass air to the core flow in front of the low pressure turbine. The claim is that this cycle will raise the OPR of the engine into the more efficient part of the compressor map under the M3+ portion of the flight envelope.

Will it work? I don’t know. Difficulties I see are:
1. Cooling of the LPT. The low turbine normally runs cooler than the HPT and doesn’t need as much cooling air. Heating the bleed bypass air will drive significantly higher LPT cooling requirements.
2. Normally at high power, air entering the LPT vanes is choked, as is the combustor air entering the HPT vanes. Increasing the temperature of the LPT entry air will change the LPT vane flow area requirements to keep the same pressure drop across the HPT. May require variable geometry LPT vanes.
3. The airflow turndown with increasing inlet temperature affects the fan also. The heated bleed bypass air can drive the low rotor faster to offset this reduction in airflow, but there will be a structural limit on how fast the Fan can turn, as well as the LPT which is also running hotter. Alternatively, you can limit the low rotor speed by closing the exhaust nozzle, increasing the engine pressure ratio and thrust at that airflow. This also increases the fan pressure ratio, pushing the fan closer to stall.

As I said, this is an interesting concept for a high altitude M3+ engine, perhaps a modern take on as a J58 successor.
 
isn't the main task of the american design reaching highly increased cooling capacity for the insane power demands they are anticipating (MW territory)?
 
Lepespi said:
isn't the main task of the american design reaching highly increased cooling capacity for the insane power demands they are anticipating (MW territory)?
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This is not likely for 6th gen, they don't casually release highly classified info like this. It's just a self funded research engine by some aeroengine institute.
 
F119Doctor said:
As I said, this is an interesting concept for a high altitude M3+ engine, perhaps a modern take on as a J58 successor.
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What PLA aircraft is flying the mach 3+ speeds? Aside from the WZ-8 I cant think of amy off the top of my head, and do correct me if im wrong but none of the 6th gens are going mach 3.
 
I'm not an engine guy, but this is more of a technology development project than a purely military engine; it seems they are "preparing for" use on spaceplanes. AECC Shenyang and other departments are also developing VCE/ACEs that are further along in development than this.
 
Reddington777 said:
What PLA aircraft is flying the mach 3+ speeds? Aside from the WZ-8 I cant think of amy off the top of my head, and do correct me if im wrong but none of the 6th gens are going mach 3.
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Not everything has to be military, they are working on high supersonic transport and launch aircraft for spaceplanes. Not to mention there are many unknown PLA projects including a possible M4 capable manned aircraft.
 
F119Doctor said:
As I said, this is an interesting concept for a high altitude M3+ engine, perhaps a modern take on as a J58 successor.
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So what technology does the successor of M3+ engine/J58 engine traditionally use? Is it still TBCC?
 
lancer21 said:
China is working on some kind of Mach 4 combat aircraft. Maybe that's what the kind of engine demonstrated above is intended for.
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Yes, these evidences we've gathered over the past few weeks interestingly suggest that China is seriously building out the foundations beneath this or has seriously evaluated it in the past.

With unmanned platforms like WZ-8, MD-22 and MD-25 already in use/development, developing a dedicated manned-recon aircraft strikes me as redundant; especially given the reveals of the WZ-X and GJ-X, which are massive unmanned aircraft (indicating the PLA is ok with large, compex, expensive unmanned aircraft). On the other hand, developing a bomber would bring in more disadvantages than advantages, so I don't think it would be worth the effort either.
 
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Looks like a different arrangement of the dual chamber design that's been floating around for years. There are even design patents with 4 chambers.

Multi-Mode-Multi-Chamber.png Multi-chamber-arrangement.png
It looks to me like they want to be able to burn more air throughly and eventually make augmentors obsolete. This would harness more power at the turbine. Ofc this reduces bypass making cooling more difficult. And effectively becomes an airbreathing rocket motor... Obviously, there's a limit how far this can go and be useful for an aircraft. Might be something for 7th generation to go into near space, though.
 
Reddington777 said:
What PLA aircraft is flying the mach 3+ speeds?
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The engine design could also allow Mach 2 supercruise at higher altitude. That opens up a list of potential aircraft applications.

Plenty of Chinese aircraft can exceed Mach 2 using conventional fuel guzzling afterburner. This engine design could then provide exhaust velocity comparable to a moderate afterburner setting with the fuel consumption of a light afterburner setting.

This reduced fuel consumption would then make the Mach 1.5 to Mach 2 regime more usable from an operational perspective using current known designs.

This engine design might maintain more thrust as altitude increases. This will help current known designs fight at higher altitudes.

The F119 doctor mentioned the US XA100-103 designs have a fuel efficient subsonic mode that this Chinese design lacks. The US fighters often have a long subsonic transit to perform to get to the combat area. The Chinese aircraft will be operating closer to home so this could be a very elegant solution.
 
insidersource said:
The engine design could also allow Mach 2 supercruise at higher altitude. That opens up a list of potential aircraft applications.

Plenty of Chinese aircraft can exceed Mach 2 using conventional fuel guzzling afterburner. This engine design could then provide exhaust velocity comparable to a moderate afterburner setting with the fuel consumption of a light afterburner setting.

This reduced fuel consumption would then make the Mach 1.5 to Mach 2 regime more usable from an operational perspective using current known designs.

This engine design might maintain more thrust as altitude increases. This will help current known designs fight at higher altitudes.

The F119 doctor mentioned the US XA100-103 designs have a fuel efficient subsonic mode that this Chinese design lacks. The US fighters often have a long subsonic transit to perform to get to the combat area. The Chinese aircraft will be operating closer to home so this could be a very elegant solution.
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The likelihood is more that the engine developed and tested is not for their current 6th gen fighters being test flown (or indeed it may not be for a future fighter either, but could be for a generic high speed platform/s).

The VCE in development for J-36/J-XDS should be under works by AECC, not CAS, and it also should be in a higher state of secrecy and likely would not have its developmental details shown publicly like this.


All of which is to say -- I suspect the VCE intended for J-36/XDS will also prioritize fuel economy as well. Range is important for the PLA as well, as they are going to be operating over the expanses of the western Pacific.
 
I found a paper, "The GE-NASA RTA Hyperburner Design and Development", The Chinese new engine looks like RTA-GE57 engine? c9d3346a-7657-4ce2-b52b-beeea28fe44b.png
 

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Jacky said:
I found a paper, "The GE-NASA RTA Hyperburner Design and Development", The Chinese new engine looks like RTA-GE57 engine?View attachment 790286
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The GE57 is conceptually similar to the YF120 variable bypass scheme with a low rotor fan bypass able to be closed off and directed into the core, with a core driven fan stage having a bypass into the fan ducts for the low bypass / higher fan pressure ratio mode. The development described appeared to focus on the advanced augmentor.

The Chinese concept puts a combustor in the core bleed and directs this into the low pressure turbine for additional low rotor power, while the GE57 core bleed goes straight to the augmentor.
 
Tomboy said:
More info on the project, as suspected it is meant for high supersonic cruise without afterburner and could be used as the turbine component in a TBCC engine for hypersonic aircraft.
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I was surprised when no one had mentioned this would be the ideal supersonic cruise engine layout. This was very obvious to me within seconds of seeing the drawing.
 
Yeah, it was obvious so most went on talking about the further reaching technical outlook. So kind of skipping the irrelevant information A and moving to the more interesting information B, C etc.

Found some of their older research publications:
Methane precooling turbine-based combined cycle engine system with interstage combustion chamber
Research on Optimization Technology of Minimum Specific Fuel Consumption for Triple-Bypass Variable Cycle Engine
As expected the goals were more turbine power for electric generation and dry fuel efficiency pushed into the afterburner region allowing supercruise up to M2.35. Pretty much the same what NATO research has been saying about VCE goals.
 
F119Doctor said:
The GE57 is conceptually similar to the YF120 variable bypass scheme with a low rotor fan bypass able to be closed off and directed into the core, with a core driven fan stage having a bypass into the fan ducts for the low bypass / higher fan pressure ratio mode. The development described appeared to focus on the advanced augmentor.

The Chinese concept puts a combustor in the core bleed and directs this into the low pressure turbine for additional low rotor power, while the GE57 core bleed goes straight to the augmentor.
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Theoretically, gained the additional power fromlow pressure turbine, could the Chinese design generate higher thrust than a design similar to the GE57? Or could the Chinese design avoid some of the shortcomings of a design similar to the GE57?
 
Seragina said:
Yeah, it was obvious so most went on talking about the further reaching technical outlook.
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Actually everyone went onto discussing Mach 3+ air frames. That isn't what this engine layout is optimised for. It could be used as the core of a TBCC engine but that's not what the drawing shows.

This Chinese engine layout would be superior to the XA100-103 engine layouts in terms of supercruise capabilities. All of the problems the US has encountered with supercruising engines this second combustion chamber solves nearly all of them.

There is a reason why the USA decided to not go with such an obvious solution. The US three stream designs have a different requirement due to the mission profile. The mission profiles for US fighters have long transit distances so the third stream is dedicated to subsonic transit fuel efficiency. The US three stream designs could be thought of performing like the F119 in low bypass mode but once the third stream opens up there is a nice maybe 20% gain in fuel burn for the long subsonic transit.

The Chinese fighters will be much closer to the combat zone. They do not need a high efficiency subsonic mode. I could see the Chinese wanting their 6th platforms having a mission profile that involves the aircraft climbing to altitude and then supercruising for the vast majority of the mission. The Chinese engine layout with two hot streams and one cold stream is then a better choice than two cold streams and only one hot stream.

The Chengdu J-36 and Shenyang J-50 would make ideal candidates for this style of engine.
 
insidersource said:
The Chinese fighters will be much closer to the combat zone. They do not need a high efficiency subsonic mode. I could see the Chinese wanting their 6th platforms having a mission profile that involves the aircraft climbing to altitude and then supercruising for the vast majority of the mission. The Chinese engine layout with two hot streams and one cold stream is then a better choice than two cold streams and only one hot stream.

The Chengdu J-36 and Shenyang J-50 would make ideal candidates for this style of engine.
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No they won't? Chinese fighters are fighting all the way out to 2nd island chain and beyond from mainland and SCS bases. They need combat radius up to 1800 miles.
 
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Tomboy said:
No they won't? Chinese fighters are fighting all the way out to 2nd island chain and beyond from mainland and SCS bases. They need combat radius up to 1800 miles.
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That is just crazy talk. Chinese aircraft will be hitting a wall of US and allied aircraft only 300 miles from the Chinese mainland. Please look at a map. Korean and Japanese territory is only 300 miles from mainland China. The Philippines is only 400 miles from mainland China.

The Chinese aircraft will never get a chance to fly a combat radius of 1800 miles unless they punch through the allied combat air patrols.

The J-36 is incredibly large and no doubt has a large internal fuel capacity. It does not need a high bypass ratio turbofan to optimise subsonic range. It will be far more lethal flying supersonic.
 
insidersource said:
That is just crazy talk. Chinese aircraft will be hitting a wall of US and allied aircraft only 300 miles from the Chinese mainland. Please look at a map. Korean and Japanese territory is only 300 miles from mainland China. The Philippines is only 400 miles from mainland China.

The Chinese aircraft will never get a chance to fly a combat radius of 1800 miles unless they punch through the allied combat air patrols.

The J-36 is incredibly large and no doubt has a large internal fuel capacity. It does not need a high bypass ratio turbofan to optimise subsonic range. It will be far more lethal flying supersonic.
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You mean air bases that are going to get wiped clean by tactical missles the second the first shot goes off? It's a joke if you think China is still confined to the first island chain. All of PLA's current efforts are pretty clearly trying to extend their control to the second island chain and beyond. Whether it be the carrier program or GJ-X and WZ-X or these new massive fighters.
 
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Pretty sure the mach 3 aircraft was because F119 doctor said this design would be for an aircraft like that and others more knowledgeable than I seem to agree.
 
I only said it was intended for a high Mach application was the PowerPoint graphic showing airflow or overall pressure ratio drop off from M1.5 to M3.5, with the J58 being one of the comparison engines shown. Whether it would be a good engine for that application is TBD.
 
F119Doctor said:
I only said it was intended for a high Mach application was the PowerPoint graphic showing airflow or overall pressure ratio drop off from M1.5 to M3.5, with the J58 being one of the comparison engines shown. Whether it would be a good engine for that application is TBD.
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I searched some papers, and this engine should be using a derivative technology of inter-stage turbine burner(ITB). All papers show that turbojet engines using ITB have better thrust performance at high speeds(＞ Mach 1.6) compared to conventional afterburning turbojet engines. However, I am puzzled as to whether ITB technology means that turbojet engines can also operate at Mach 3 to Mach 4, thus eliminating the need for TBCC engines.
 

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