Su-57 intakes, supercruise performance and 2nd stage engine

[F119Doctor]

Thanks! Very interesting. Some comments below.



I've been trying to extrapolate Izd. 30 performance based on open-source data available on other clean-sheet, new-generation Russian engines and demonstrator turbomachinery. As a lower bound, I got the same kind of LP compressor PR. As an aside, if you say 4.2 is only sufficient for at most Mach 1.4 supercruise, what's the PR of the F119 LPC, if that is publicly releasable info? It also has a 3-stage fan, and otherwise does not seem to have especially high stage-PRs compared to the EJ200 with a 4.2 ratio for its LPC.

Worth noting that the KND-924-3 blisk LPC upgrade for the AL-31FM was already supposed to hit a 4.2 ratio 20 years ago. So with advances in the state of the art in the mean time, I expect this to be firmly the lower bound, as mentioned.



It's definitely going to be a 5-stage machine. Other than that, I think this is almost certainly low-balling the HPC PR. From the performance achieved in the civilian PD-14 compressor, various research projects and a 6-stage core upgrade for the ultimate AL-31FM3 that targeted 6.7, i'd expect a PR of at least 6.2 (like the 5-stage EJ200). Possibly as high as 7.0 as an upper bound (but that is pushing it on OPR, leading to high compressor exit temps for an engine behind a supersonic intake).

Might the temperature rise over a machine with a relatively high number of stages and a high PR skew your geometrical method here?



Plausible. My gut instinct is also that the Russians would not go quite as low with BPR as the F414, M88 or F119, given a fairly high emphasis on SFC in their statements about the design. So nearer to 0.4 (akin to the EJ200) than 0.3 or less seems about right.



The rear of the engine schematic looks suspiciously like the legacy AL-31F (nozzle design, AB flame holders, turbine exit cone), so that might be a place holder. When images were first leaked of the LO nozzle on an uninstalled Izd. 30, the interior was censored, obscuring the AB flame holder design and possible LO measures. It's conceivable that these are considered sensitive and therefore not shown.



Fairly safe bet that there will be independent A8/A9 control given the emphasis on supersonic performance - the AL-31F nozzle already had this.

1. The F119 fan pressure ratio, like many of the engine’s specifications, has not been publicly released, to my knowledge

2. Is the Project cross section accurate? Hard to tell. When the F119 cross section was first printed, the inner and outer flow path were split to prevent any geometric analysis by better engineers than me.

3. Could the HP compressor pressure design ratio be higher than the flow path geometry indicates? Yes, the operating line of the compressor is a function of the HP turbine inlet vane area. Making the HPT vane flow area smaller will raise the operating line and increase the HPC pressure ratio. However, this results in the flow Mach number decreasing in the rear stages of the compressor, and pushes the compressor towards stall and typically reduces the compressor efficiency. But, as I said before, the Russians have known to be very good at aerodynamics, so they may have found way to make this work for them.

The real challenge for supercruise is to maintain the airflow and engine pressure ratio under increasing ram inlet air temperature. You have to have sufficient Fan pressure ratio for have nozzle exhaust velocity higher than your supersonic airspeed to have forward thrust and enough to overcome drag. As the inlet temperature increases with Mach number, both the LP and HP spools have to turn faster with increasing TIT just to maintain the same airflow and pressure ratio, until you hit the rotor speed and TIT limits, after which your airflow and engine pressure ratio drop off. Having sufficient rotor speed and TIT margin for high inlet temperatures , along with a high Fan Pressure Ratio / Engine Pressure Ratio for high non-reheat exhaust velocity is the key. And very difficult to achieve….

 

[icyplanetnhc (Steve)]

ОКБ им. А. Люльки и РАН договорились о работах по полноразмерному детонационному двигателю

new.ras.ru

It would appear that the "universal gas turbine engine" for 5th and 6th generation fighters in slide 5 would refer to the izdeliye 30. Some of the numbers are interesting, as the engine fits in the same footprint as the AL-31FP, has 30% more thrust and 15% lower specific fuel consumption, and have an "assigned life" of 6,000 hours. This would indicate that the izdeliye 30 produces 16,250 kgf, or 35,825 lbs of thrust, and perhaps up to 17,000 kgf or 37,479 lbs in emergency power during single-engine operations.

 

[paralay]

The achieved milestone of 16,000 kgf was informally announced before the appearance of izd.30. AL-51F (izd.30) should give 17,500 kgf

 

[Ainen]

It would appear that the "universal gas turbine engine" for 5th and 6th generation fighters in slide 5 would refer to the izdeliye 30. Some of the numbers are interesting, as the engine fits in the same footprint as the AL-31FP, has 30% more thrust and 15% lower specific fuel consumption, and have an "assigned life" of 6,000 hours. This would indicate that the izdeliye 30 produces 16,250 kgf, or 35,825 lbs of thrust, and perhaps up to 17,000 kgf or 37,479 lbs in emergency power during single-engine operations.

UGD is a separate engine program, aimed at all the different AL-31 subtypes (maintenance problem).

It's a close relative of the concurrent engine development, but not the same.

 

[F119Doctor]

1. The F119 fan pressure ratio, like many of the engine’s specifications, has not been publicly released, to my knowledge

2. Is the Project cross section accurate? Hard to tell. When the F119 cross section was first printed, the inner and outer flow path were split to prevent any geometric analysis by better engineers than me.

3. Could the HP compressor pressure design ratio be higher than the flow path geometry indicates? Yes, the operating line of the compressor is a function of the HP turbine inlet vane area. Making the HPT vane flow area smaller will raise the operating line and increase the HPC pressure ratio. However, this results in the flow Mach number decreasing in the rear stages of the compressor, and pushes the compressor towards stall and typically reduces the compressor efficiency. But, as I said before, the Russians have known to be very good at aerodynamics, so they may have found way to make this work for them.

The real challenge for supercruise is to maintain the airflow and engine pressure ratio under increasing ram inlet air temperature. You have to have sufficient Fan pressure ratio for have nozzle exhaust velocity higher than your supersonic airspeed to have forward thrust and enough to overcome drag. As the inlet temperature increases with Mach number, both the LP and HP spools have to turn faster with increasing TIT just to maintain the same airflow and pressure ratio, until you hit the rotor speed and TIT limits, after which your airflow and engine pressure ratio drop off. Having sufficient rotor speed and TIT margin for high inlet temperatures , along with a high Fan Pressure Ratio / Engine Pressure Ratio for high non-reheat exhaust velocity is the key. And very difficult to achieve….

One method of possibly increasing the HPC pressure ratio beyond the geometric flow area reduction would be to put variable vanes in the rear of the compressor.

In current HPC designs, there are variable vanes at the inlet and behind one or more stages of the front end compressor blades. When the core is running slow and the pressure ratio is much lower than the geometric flow contraction, the Mach number increases in the back of the compressor until the flow becomes choked, which slows the airflow in the front of the compressor and drives the airfoils to higher angle of attack and into stall. In this condition, the variable vanes are cambered to reduce the front end AOA, effectively making the front end smaller and unchoking the back end. As the rotor speed increases, the vane move toward a more axial direction, increasing the front end airflow to match the increasing capacity in the back end as the pressure ratio approaches the geometric flow area reduction for the design high power pressure ratio.

By putting variable vanes in the back of the compressor, one could optimize the aft end airfoil AOA as the pressure ratio exceeds the geometric flow area reduction, effectively making the back end of the compressor smaller.

To my knowledge, there has only been one engine flown with variable compressor aft end variable vane - the YJ93 on the XB-70. These were intended to make the back end of the compressor larger while the front end variable vanes made the front end smaller under the lower corrected rotor speeds encountered under M3+ high temperature inlet conditions. This was to address the same design challenges that the J58 in the A-12 / SR-71 addressed with variable inlet guide vanes and mid-stage bleed bypass.

I don’t know of any engines with variable compressor aft end variable vanes for high pressure ratio operation, and I don’t see any signs of this configuration in the Project 30 cross section shown. There are a lot of aero mechanical / thermal design challenges to put variable vanes in the back of the HPC, which may be why they have never been in production engines.

 

[Scott Kenny]

There are a lot of aero mechanical / thermal design challenges to put variable vanes in the back of the HPC, which may be why they have never been in production engines.

Can't imagine how much "fun" designing that would be... Let's start with whatever materials you're using for your turbine blades, then fuss with variable pitch mechanisms in the hottest part of the engine...

 

[F119Doctor]

Can't imagine how much "fun" designing that would be... Let's start with whatever materials you're using for your turbine blades, then fuss with variable pitch mechanisms in the hottest part of the engine...

You misunderstood my comment - I was specifically talking about variable vane at the back end of the high pressure compressor - still very hot at 1000+F, pushing the air against an adverse pressure rise that is always wanting to reverse direction, but not turbine temperatures.

However, varying the area of the high pressure turbine vanes to adjust the operating line of the engine during operation is another challenge that we may see addressed in the not so distant future

 

[Scott Kenny]

You misunderstood my comment - I was specifically talking about variable vane at the back end of the high pressure compressor - still very hot at 1000+F, pushing the air against an adverse pressure rise that is always wanting to reverse direction, but not turbine temperatures.

However, varying the area of the high pressure turbine vanes to adjust the operating line of the engine during operation is another challenge that we may see addressed in the not so distant future

There's more than a few engines that are using materials and techniques normally used for turbine blades on the last couple stages of their HP compressors.

 

[icyplanetnhc (Steve)]

Seems Izd.30 will be named Al-51F1.

https://twitter.com/x/status/1676407148140457985

View: https://twitter.com/MuxelAero/status/1676407148140457985?t=ZBrc00CF7OUig5GYsNm0wg&s=19

This is from an OAK presentation in June 2023 at Samara University. The presentation, with some slides blurred, can be found here.

View: https://youtu.be/g6W_5FllNGU?feature=shared&t=6350

Interestingly, at 1:45:50, Evgeniy Marchukov states that the Su-57 with the current AL-41F1 requires some afterburner to achieve supersonic cruise, hence why he deemed it as "fifth-generation minus". Given that the Su-35 could apparently achieve Mach 1.1 with the AL-41F1S, he may be referring to the Su-57's use of afterburner to achieve the Mach 1.3 requirement. The izdeliye 30 engine is designated as the AL-51F1 in this presentation, which presumably is the expected official designation. Marchukov also gives some background from Saturn's perspective on potential flat nozzle application on the Su-57, where he states that Sukhoi only requested a flat nozzle recently, after all of the airframe-engine integration was already complete. This apparently made flat nozzle integration challenging as Sukhoi did not want to alter the airframe, and achieving acceptable lifespan and performance was described as a struggle. He mentioned that flight tests can hopefully start this year.

He describes another engine that has the same envelope as the AL-31FP, but with 5th generation engine technology. This engine appears to be the "universal gas turbine engine" as described in this slide as referenced here, but I can't quite tell if this is distinct from the izdeliye 30/AL-51F1. This engine is intended to be a drop-in replacement for most of the existing Su-27 family of aircraft, as the AL-31FP has a smaller inlet diameter of 905 mm compared to 932 mm of the AL-41F1 and AL-41F1S.

Piotr Butowski also wrote a good summary of the presentation in an Aviation Week article here.
https://aviationweek.com/defense-sp...russias-fighter-engine-development-slow-going

 

[Anduriel]

Interestingly, at 1:45:50, Evgeniy Marchukov states that the Su-57 with the current AL-41F1 requires some afterburner to achieve supersonic cruise, hence why he deemed it as "fifth-generation minus". Given that the Su-35 could apparently achieve Mach 1.1 with the AL-41F1S, he may be referring to the Su-57's use of afterburner to achieve the Mach 1.3 requirement.

Okay. This needs to die. Never Marchukov states that there is need to AFB. Nor does he gives any speed values.

So, 1:45:50 transcript (in Russian)

Spoiler: LONG TEXT

Следующий двигатель. Мы его назвали "поколение 5-", потому, что по удельным характеристикам он соответствует 5-му поколению, кроме крейсерского сверхзвука, удельной тяги на "максимале" не хватает немножко до 5-го поколения. Этот двигатель тоже прошел государственные стендовые испытания (ГСИ) и сейчас объект Су-57 летает на этом двигателе. Тут тоже много нового, и новая электронно-цифровая система с полной ответственностью, и мероприятия по спецхарактеристикам и так далее.

Следующий двигатель, который сейчас у нас на стенде, это где мы используем, использовали наш задел по 5-му поколению, даже 5+ поколение, этот двигатель имеет диаметр входа и длину, и массу двигателя АЛ-31ФП, т.е. он полностью взаимозаменяем и можно ставить на самолет марки Су-27, Су-30, Су-35. Но у него, значит, тяга существенно больше, это наработка на боевых режимах, назначенный ресурс, межремонтный можно сделать, это еще не доказано, но расчетами доказаны -по параметрам это видно - сделать 2000, а назначенный это до 6000, и вот преимущество, которые написаны, они будут, в общем-то реализованы.

Двигатель, который делается для нашего беспилотника тяжелого, который сейчас разрабатывается, это называется "Охотник", его показывали, его выкатку показывали по телевизору, Новосибирский завод делает. Это на основе двигателя, вот который стоит на Су-57, изделие 117Б у нас называется, только нижнее расположение агрегатов, нет форсажной камеры, и выходное устройство для обеспечения РЛ заметности плоское. И вот, вот этот переход с круглого на плоское, вот он реализован, вот эта се-, причем вот эта серая часть - это самолетная часть. Но самолетчики сказали
"мы такого никогда не делали" вот впервые в истории нашего КБ мы делаем кусок самолета. Я говорю, нам уже осталось научиться крылья делать, и уже нам никто не будет нужен, кроме Самарского университета.
Вот такой двигатель у нас прошел уже часть ресурсных испытаний, это, значит, идут полеты этой беспилотной птички.

Так.
Ну, вот при создании двигателя нового поколения используется много новых технологий. Тут и новые технологии, и новые материалы, и это делается в ОДК в общем-то совместно; Иноземцев Сан Саныч какие-то технологии для ПД-14, часть мы их у себя применили, а то что мы сделали, мы это Сан Санычу отдали и вот с Кузнецовым обмениваемся технологиями, вот Павел иногда звонит: "Слушай не могу понять что, пришли своих ребят". Мы, то есть мы, сейчас в одной компании ОДК и вот такой полезный симбиоз у нас развивается. Вот, например, значит, интерметаллидные сплавы, который при той же... Вот эта вот технология, это литье сегментов жаровой трубы, жаровая труба уже на двигателе, который уже прошел гос. испытания собрана из сегментов, они из интерметаллидного сплава, и, ну, пока направленной кристаллизации, но можно делать даже монокристальное литье, представляете, монокристальная камера сгорания, т.е. она может быть стехиометрическая. В будущем. Ну тут надо турбину подтянуть.

Ну тут мы написали как бы тренд развития наш, где вот двигатель АЛ-51, это вот который будет на Су-57 стоять.
На это, значит, куда у нас сейчас развивается программа двигателя: газогенератор и технологии двигателя 6-го поколения, такой научно-технический задел (НТЗ). Мы вместе самым этим занимаемся. Дальше, значит, требования, которые предъявляются к двигателю 6-го поколения, тут вместе надо тут... Ну аддитивные технологии понятно, они, в общем, активно развиваются и тут нам, в общем-то надо догонять мир, а дальше эти, армированные сплавы и композиции, адаптивные циклы - сейчас я ниже расскажу - активные системы управления двигателями...
Очень сильно возрастает интеграция изделия с объектом. От этого можно очень многое выиграть и самолетчикам; нужно гораздо больше сейчас энергии, т.е. мы даже уже рассматриваем технологию вместе с Уфимским университетом - это генератор на валу двигателя, а не на коробке.
Вот, я попытался тут ближайшие технологии для шестого поколения: это технология третьего контура; технология обеспечения спецхарактеристик, которые для нас, в общем-то, когда на двигатель 117 выдвинули требования, были новые и мы тут с нуля начинали, поскольку за рубежом все это закрытая информация; технология применения композитных материалов, особенно в узлах горячей части; технология электрификации ГДТ; распределенной механоторонной САУ двигателя; это цифровое проектирование ГТД; и любопытная низкая это технология детонационного повышения тяги.

Вот я коротко про каждую расскажу.

Это третий контур, у нас изделие уже такое, индекс присвоен.
Значит, мы хотим изготавливать, значит детали, вот такой вот стендовый вариант двигателя, это третий контур в виде таких сделан, и мы (получаем) по расчетам до 5 % снижение удельного расхода.На стенде даже. А в полете до 10% оцениваем снижение, значит расхода воздуха на крейсерских режимах. Т.е это, фактически, двигатель изменяемого цикла: когда нужна большая тяга, когда надо ему догнать кого, высокая удельная тяга (нужна) - отбор закрыт, а на крейсерских он открывается и снижается сопротивление самолета, повышается контурность и так далее.

Значит это комплекс по исследованию спецхарактеристик проводим совместно с Институтом тепло- и прикладной электродинамики РАН, с академиком Игорьковым. Оптимизированы геометрические размеры сопла и внешняя огранка, схемы маскировки, эффективное термостойкое радиопоглощающее покрытие, высокотемпературные покрытия, метаматериалы созданы…
В общем, все что можно показать я тут сказал, но это вот очень серьезное направление, которое в ТЗ заданы строгие требования и оно, конечно, они портят нам жизнь, ухудшают характеристику двигателя - даром ничего не дается.

Вот мы уникальную, значит, работу делаем. Сухие значит говорят “сделайте для незаметности нам плоское сопло”. Причем когда закладывали новые изделия, сказали “нам не надо”, а вот когда все готово “сделайте плоское”, причем обычно плоское сопло должно быть близко интегрировано с самолетом, а они самолет не хотят сильно менять, поэтому у нас получилось вот такое вот достаточно сложное вот сопло, плоское, причем потери невысокие очень удалось достичь и 4 независимые управляемые створки: две дозвуковых, две сверхзвуковых. Почему независимы? Потому, что управляется критиком среза, и управляемый вектор тяги. Т.е очень сложное управление. Это вот показано на стенде на форсаже это сопло работает, 90% деталей изготовлено аддитивными технологиями, и сейчас уже третья постановка на стенд, отрабатываем автоматику, все и, надеюсь, скоро уже начнем ресурсные испытания и в этом году попробуем с этим соплом взлететь.
Т.е. это вот достаточно уникальная разработка.

Вот это вот элементы нашей работы по шестому поколению. Значит мы изготовили уже керамическую камеру сгорания. Вот это вот ее жаровая труба, горелки керамические и мы изготавливаем там железную часть, потому, что фронт там из металла, а жаровая труба и форсунки из керамики, и есть сопловые аппараты из керамики. Вот мы хотим в конце года на стенде такую камеру испытать.

At no point he does say that there is afterburner needed for supercruise.

 

[icyplanetnhc (Steve)]

Мы его назвали "поколение 5-", потому, что по удельным характеристикам он соответствует 5-му поколению, кроме крейсерского сверхзвука, удельной тяги на "максимале" не хватает немножко до 5-го поколения.

Perhaps this is lost in the translation, but how else are you interpreting this?

 

[Anduriel]

"We called it "Generation 5-" because it's specific values are of Gen 5 engine with an exception of supercruise, somewhat not enough of specific thrust at MIL power for 5 gen engine"
It does not say that current MIL thrust is insufficient for Su-57 to have supercruise, at all.

 

[BBCRF]

Perhaps this is lost in the translation, but how else are you interpreting this?

Cruising supersonic flight can be different. For the MiG-25, these values are 2.53. For the MiG-31, 2.35M

 

[icyplanetnhc (Steve)]

I’m sorry, but is “supercruise” somehow an extensive property that changes with mass?

 

[BBCRF]

yes, because with increasing mass, the required lifting force increases, which means you will have 2 ways out either to increase the angle of attack or to increase the speed.but in this case, your fuel consumption will increase. Because it takes more thrust to maintain the required lift. it also all depends on the aerodynamic layout of the aircraft. For the MiG-25, let's assume that the speed of the supercruise does not depend on the flight weight and the minimum kilometer fuel consumption is achieved with M = 2.4-2.53

 

[overscan (PaulMM)]

"We called it "Generation 5-" because it's specific values are of Gen 5 engine with an exception of supercruise, somewhat not enough of specific thrust at MIL power for 5 gen engine"
It does not say that current MIL thrust is insufficient for Su-57 to have supercruise, at all.

He is saying the engine is roughly 5th generation in performance with the exception of supercruise capability, where maximum MIL thrust is not is not up to 5th generation standards.

I don't think this precludes some measure of supercruise, just not up to F-22 levels.

 

[icyplanetnhc (Steve)]

yes, because with increasing mass, the required lifting force increases, which means you will have 2 ways out either to increase the angle of attack or to increase the speed.but in this case, your fuel consumption will increase. Because it takes more thrust to maintain the required lift. it also all depends on the aerodynamic layout of the aircraft. For the MiG-25, let's assume that the speed of the supercruise does not depend on the flight weight and the minimum kilometer fuel consumption is achieved with M = 2.4-2.53

Lift-induced drag is a very small part of overall drag at supersonic speeds. The predominant form of drag is parasitic, with wave drag and shock interferences being major contributors. Furthermore, engine performance itself does not depend on airplane mass.

He is saying the engine is roughly 5th generation in performance with the exception of supercruise capability, where maximum MIL thrust is not is not up to 5th generation standards.

I don't think this precludes some measure of supercruise, just not up to F-22 levels.

Rereading his comments, I think this may be the more accurate interpretation. The AL-41F1 may provide some limited supercruise capability, but not up to what they would consider to be 5th generation standards due to insufficient specific thrust. Per the OAK Saturn presentation in 2021, the izdeliye 30/AL-51F1 would address this and have 6.4% better specific thrust than the izdeliye 117/AL-41F1.

 

[Anduriel]

He is saying the engine is roughly 5th generation in performance with the exception of supercruise capability, where maximum MIL thrust is not is not up to 5th generation standards.

I don't think this precludes some measure of supercruise, just not up to F-22 levels.

Yes. Because Su-35 can fly supersonic at mil power while clean, and it's with weaker engines and unoptimized airfame. Hell, even Tu-128 can have M1.0 on MIL power, though it takes quite long time to achieve that and brief AFB acceleration is preferable.

Add to this that we don't know precisealy what Marchukov and co consider as 5 gen specs.
Nor do we have any info what desired specs RuMOD written in Su-57 TZ (task) when it was given to Sukhoi.

 

[BBCRF]

Лобовое сопротивление, вызванное подъемной силой, составляет очень малую часть общего лобового сопротивления на сверхзвуковых скоростях. Преобладающая форма лобового сопротивления - паразитная, основными факторами которой являются волновое сопротивление и ударные помехи. Кроме того, сами характеристики двигателя не зависят от массы самолета.

There is no drag and the required lifting force. Yes, the characteristics of the engine do not depend on the weight of the aircraft. However, your engine is part of the product.Therefore, it should be considered as part of a specific aircraft

 

[Scott Kenny]

He is saying the engine is roughly 5th generation in performance with the exception of supercruise capability, where maximum MIL thrust is not is not up to 5th generation standards.

I don't think this precludes some measure of supercruise, just not up to F-22 levels.

I'm interpreting that to mean that you need AB to get supersonic, but can cruise at MIL in the Mach 1.2-1.4 range once there.

 

[LMFS]

Per the OAK Saturn presentation in 2021, the izdeliye 30/AL-51F1 would address this and have 6.4% better specific thrust than the izdeliye 117/AL-41F1.

Added to a significant increase in absolute thrust, that should allow to produce much more thrust in supersonic flying conditions.

 

[F119Doctor]

There is thrust, to achieve a high T/W ratio for acceleration and climb. There is high specific thrust, needed to produce the high exhaust velocity needed for non-augmented supersonic thrust. And there is the ability to maintain that high specific thrust under the elevated inlet temperatures (100F+) that are encountered at the M1.5+ conditions. You need all three for a successful supercruise engine, and the last criteria is the most difficult to achieve with any sort of engine durability.