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

[LMFS]

AL-31FP weighs 1520-1530kg. AL-41F1S weighs about 1604kg. Brochure figures. We have no definitive weight for 117, only a single comment from 2010 aimed specifically at rebutting Russian media criticisms of the engine choice. Sukhoi also claimed 30% lower weight for Izdeliye 30 - which is 1071kg, which is lighter than F414. We'll see about that I guess.

The comment is a technical statement and comes from a top respected and knowledgeable guy, UAC head at the time IIRC, so I am more than ready to basically take it at face value, at least when it makes sense and we have no other valid source that contradicts it. That would be 1370 kg for the izd. 117.

As to the 30% lower weight of the izd. 30, it was actually specific weight, which is the inverse of thrust to weight ratio. And that value, for a weight of ca. 1400 kg, gives the famously claimed thrust of 18 tf.

 

[icyplanetnhc (Steve)]

Roughly 1,600 kg mass for the AL-41F1 was given in multiple publications by Butowski, who has thus far proven to be very accurate with regards to the Russian aerospace industry.

If we are to take the “official” figures at face value, then the numbers would be preposterous. If specific weight refers to the inverse of thrust-to-weight ratio, then 30% lower specific weight means 43% greater T/W. If the AL-41F1 (117) really does weight 1,370 kg with 14.5 tons of thrust, then the izdeliye 30 will have a T/W of 15.1, and (assuming ~1,400 kg mass) have a thrust of 21.2 tons (208 kN, 46,600 lbf)

Sorry, but nope…

 

[LMFS]

1,600 kg for the AL-41F1 was given in multiple publications by Butowski, who had thus far proven to be very accurate regarding the Russian aerospace industry.

If we are to take the official figures at face value, then the numbers would be preposterous. If specific weight refers to the inverse of thrust-to-weight ratio, then 30% lower specific weight means 43% greater T/W. If the AL-41F1 really does weight 1,370 kg with 14.5 tons of thrust, then the izdeliye 30 will have a T/W of 15.1, and a thrust of 21.1 tons.

Sorry, but no…

Butowski seems very well connected, but he has made such outlandish claims as Okhotnik having the same low altitude max speed as a Su-35. My personal choice is to take a top UAC official anytime, specially when they are actual technical people knowing what they talk about, but who knows.

As to the 30% lower specific weight, it was referred to the izd. 117S, whose official weight is the one overscan noted above, 1604 kg. So TWR of izd. 30 is 12.9, corresponding to ca. 18 tf if we assume 1400 kg weight. May be more, may be less, but it is reasonable.

 

[Bhurki]

Having gone through multiple sources that cite info about the new engines in the last week, I find that the language deviates quite a bit on both sides of the mean reference(117s). Though, one strand of info seems to resonate through all, 'the thrust capability vis-a-vis the weight (specific weight) will be about 30% higher'.
I'm not adept at understanding the nuances of the Russian language, but they are probably referring to the T/W ratio.

1.3x 9.3 is 12.0.
It would be safe to assume that the final product will deviate on standard around this number. Whether it be 19 tons at 1600 kg, 17 tons at 1400 kg or anywhere in the middle.

 

[LMFS]

Having gone through multiple sources that cite info about the new engines in the last week, I find that the language deviates quite a bit on both sides of the mean reference(117s). Though, one strand of info seems to resonate through all, 'the thrust capability vis-a-vis the weight (specific weight) will be about 30% higher'.
I'm not adept at understanding the nuances of the Russian language, but they are probably referring to the T/W ratio.

Could you refer the sources?

1.3x 9.3 is 12.0.

I don't understand this.
- It is the inverse of TWR that is ca. 30% lower in izd. 30 than in 117S.
- That value is calculated based on max thrust, not mil.
- Mil value for 117S is 8.8 tf

 

[icyplanetnhc (Steve)]

Butowski seems very well connected, but he has made such outlandish claims as Okhotnik having the same low altitude max speed as a Su-35.

Where? He did initially put the S-70’s maximum speed as 1,400 km/h, but it has since been written as 1,000 km/h in more recent publications, including his 2021 book on the Su-57.

As far as specific weight or T/W, and what the baseline for the comparisons is, I’ve perused through several sources but often times, the specifics are often appended by the journalist rather that directly from officials themselves. Again, there are nuances to the Russian languages that can result in quite significantly different quantitative results. Is it “specific weight” that’s 30% better, or T/W? I have yet to find a statement directly from Lyulka-Saturn that establishes the specific weight improvement and the baseline that it’s being compared to, based on the sources that I have read. Perhaps you can provide one?

 

[Bhurki]

I don't understand this.
- It is the inverse of TWR that is ca. 30% lower in izd. 30 than in 117S.

Specific thrust or thrust at specific weight means thrust per unit mass.

 

[F119Doctor]

I don't understand this.
- It is the inverse of TWR that is ca. 30% lower in izd. 30 than in 117S.

Specific thrust or thrust at specific weight means thrust per unit mass.

Unless “specific thrust” means thrust per unit of airflow - not thrust to weight.

Supercruise requires high exhaust velocity at Mil power at supersonic inlet conditions. Typically this requires low bypass ratio, which implies a large core (high compressor, combustor, high turbine). Big cores are heavy and low bypass reduces augmentation ratio, making 12:1 T/W very unlikely for a supercruise engine that has any measure of durability.

 

[Bhurki]

making 12:1 T/W very unlikely for a supercruise engine that has any measure of durability

We're trying to assess the max T/W limit here. Anything lower is viable.
This is for the people who are suggesting that somehow a 1200 kg engine could produce 20 tons of thrust.

 

[LMFS]

Where? He did initially put the S-70’s maximum speed as 1,400 km/h, but it has since been written as 1,000 km/h in more recent publications, including his 2021 book on the Su-57.

Proves he has a questionable technical knowledge.

As far as specific weight or T/W, and what the baseline for the comparisons is, I’ve perused through several sources but often times, the specifics are often appended by the journalist rather that directly from officials themselves. Again, there are nuances to the Russian languages that can result in quite significantly different quantitative results. Is it “specific weight” that’s 30% better, or T/W? I have yet to find a statement directly from Lyulka-Saturn that establishes the specific weight improvement and the baseline that it’s being compared to, based on the sources that I have read. Perhaps you can provide one?

Specific weight is what Russian industry uses. This is one of the sources that reported such statements:

НПО «Сатурн» создает двигатель поколения 5+ | Еженедельник «Военно-промышленный курьер»

Стендовые испытания принципиально нового двигателя (двигателя второго этапа) для российского самолета пятого поколения ПАК ФА начнутся в 2014 году, сообщил генеральный конструктор-директор Научно-технического центра имени Люльки НПО «Сатурн» Евгений Марчуков.

vpk-news.ru

NPO Saturn creates a 5+ generation engine ​

Bench tests of a fundamentally new engine (engine of the second stage) for the Russian fifth-generation aircraft PAK FA will begin in 2014, said Evgeny Marchukov, General Designer-Director of the Lyulka Scientific and Technical Center of NPO Saturn.

“The engine will be ready in hardware in two years, and bench tests will begin, and its refinement will take place,” said E. Marchukov at the 11th International Conference “Aviation and Cosmonautics - 2012”, which opened at the Moscow Aviation Institute on Tuesday.

According to him, the new "engine 117" will belong to the "5+" generation and will surpass the existing foreign counterparts of engines for fifth-generation aircraft in terms of its characteristics.

“This is a fundamentally new engine, so it takes a long time to create. The engine has a 30% less specific gravity (than 117C - approx.), The life cycle cost is also 30% less, and it itself should be cheaper, "- said E. Marchukov.

Specific thrust or thrust at specific weight means thrust per unit mass.

See comment from F119Doctor

Marchukov reported recently that the specific thrust of izd. 30 was the highest of any comparable engine, worldwide. All indicates they use that term in the same sense than the West

Supercruise requires high exhaust velocity at Mil power at supersonic inlet conditions. Typically this requires low bypass ratio, which implies a large core (high compressor, combustor, high turbine). Big cores are heavy and low bypass reduces augmentation ratio, making 12:1 T/W very unlikely for a supercruise engine that has any measure of durability.

Izd. 30 has a lower stage count, but I cannot comment on whether that T/W is realistic or not. Maybe it being VCE would do the trick and allow to raise AB thrust enough? It may be more complex and heavy due to the variable circuit on the one hand, but augmentation could be more effective too.

 

[icyplanetnhc (Steve)]

Proves he has a questionable technical knowledge.

Butowski has overwhelmingly demonstrated himself to be correct more often than not. Pointing to isolate instances of errors that he has since corrected as "proof" of questionable technical knowledge and dismissing his work is frankly preposterous. I would rate his assessments very highly, especially if they have remained consistent over time.

The verbatim statement was "specific gravity" when translated from Russian to English. This is a different property from specific weight, and I haven't heard of this term used to describe engine performance characteristics (I’ve only heard of it used for fuel density). I would prefer to have someone who understands the nuances of the Russian language to clarify what this refers to.

EDIT: Calling him questionable? He published the turbomachinery architecture of the izdeliye 30 (3 stage LPC/fan, 5 stage HPC, 1 stage HPT, 1 stage LPT) as early as 2013. He drew the N036 side arrays quite accurately before the aircraft even first flew.

 

[LMFS]

Butowski has overwhelmingly demonstrated himself to be correct more often than not. Pointing to isolate instances of errors that he has since corrected as "proof" of questionable technical knowledge and dismissing his work is frankly preposterous. I would rate his assessments very highly, especially if they have remained consistent over time.

That is why I said he is very well connected, I take his reports seriously too. But what I find preposterous is to think he is on a higher level as a source than the head of UAC...

The verbatim statement was "specific gravity" when translated from Russian to English. This is a different property from specific weight, and I haven't heard of this term used to describe engine performance characteristics. I would prefer to have someone who understands the nuances of the Russian language to clarify what this refers to.

Russians don't use the same terminology than us, but of course, go ahead and do your research please.

 

[paralay]

izd. 117S (Su-35S) 14500 kgf / 8870 kgf, short-term mode-15000 kgf, engine weight 1604 kg-dry weight of the engine in a "simple configuration"
izd 117 (Su-57) 15500-16000 kgf / 9800 kgf
izd 30 (Su-57) 17500 kgf / 11000 kgf engine weight 1750 kg

 

[LMFS]

izd. 117S (Su-35S) 14500 kgf / 8870 kgf, short-term mode-15000 kgf, engine weight 1604 kg-dry weight of the engine in a "simple configuration"
izd 117 (Su-57) 15500-16000 kgf / 9800 kgf
izd 30 (Su-57) 17500 kgf / 11000 kgf engine weight 1750 kg

Rosobornexport official data (izd. 117S)

Special power conditions, kgf 14500-2%
Full afterburner military thrust, kgf 14000-2%
Max military thrust (w/o afterburning), kgf 8800±2%

http://roe.ru/eng/catalog/aerospace-systems/engines/al-41f-1s/

For the rest of the data, we need a source or reasoning to start with...

 

[paralay]

Deputy Chief Designer A. S. Bulatov:
- the engine of the fighter "75", existing, in the thrust class of 14.5-16 tons (end of quote)

Obviously izd. 117C and izd. 117

 

[Scar]

As far as i can understand, again, from Bulatov' speech, this will be a new version of izd.117.

 

[paralay]

He didn't say "new version"

 

[LMFS]

Bulatov speaks at the mark 17:45 about the engine

View: https://www.youtube.com/watch?v=Vy4Q-NoQyoo


As per the transcription here:

Облик перспективного легкого однодвигательного истребителя пятого поколения ЛТС

Появление разработанного в условиях секретности самолета ЛТС, о предстоящей презентации которого было объявлено только 13 июля, стало большим сюрпризом для всей авиационной общественности.

rusnext.ru

Bulatov said that "the engine will be in the 14.5-16 t class. This engine is made on the basis of the groundwork of the United Engine Corporation, and will be even more advanced on this aircraft."

It does seem to indicate that there will be a further development of the 117 for this plane, at least for the export version. Which makes sense, since thrust is one of the main apparent constraints for such concept.

 

[LMFS]

I am going to quote here for reference some excerpts about the izd. 30 from the last interview with Marchukov at N+1 a couple of years ago:

Плазменный мотор

N + 1 поговорил с разработчиком «Изделия 30» для истребителя Су-57

nplus1.ru

“The difference between engines of different generations is manifested, first of all, in their specific parameters. There are several main parameters: specific gravity, specific thrust and specific fuel consumption per kilogram of thrust per hour. The generational change occurs with the simultaneous improvement of all these characteristics. In this regard, “Product 30” can even be attributed to the “5+” generation, since this engine was created taking into account domestic and foreign experience in the development and operation of fifth-generation engines. In the USSR, and then in Russia, this engine was “Product 20”. It was planned to install it on the MiG-1.44 MFI fighter being developed by the MiG corporation. Then “Product 30” appeared, ”said N + 1 Marchukov.

>> Izd. 30 should be expected to go beyond parameters of known 5G engines.
>> The reference of izd. 30 as a follower of izd. 20 is very obvious here

Specific gravity in aviation is usually called the ratio of the mass of the engine to its total thrust. For the promising "Product 30" this figure is less than 0.1, that is, the engine is capable of delivering more than 10 times more thrust than it weighs itself. Specific thrust is the ratio of the total thrust to the air flow rate of the engine.

>> About the questions above on the meaning of specific weight/gravity parameter.
>> The above estimation of 17500 kgf / 1750 kg weight is explicitly denied here. The ratio 10:1 was already surpassed at izd. 117 (ca. 11:1)

In the second stage engine for the Su-57, the developers applied a number of new design approaches and technologies, due to which the "Product 30" in terms of specific fuel consumption roughly corresponds to the AL-31F bypass engine (670 grams per kilogram-force per hour in cruising mode), but surpasses its in terms of specific thrust.

>> Unclear, whether this is just the journo saying it. But the wording seems solid and well documented. It is complemented in any case by the subsequent statement quoted to Marchukov:

“Specific fuel consumption opposes specific thrust. The best fuel consumption is obtained on civilian by-pass engines, but they have the least specific thrust due to the high by-pass ratio. In single-circuit engines, on the contrary, the specific thrust is high, but the consumption is also high. Due to the use of new designs and technologies in "Product 30" the specific consumption remained at the same level, but the specific thrust increased, "Marchukov said.

>> The hint to VCE is not so subtle here, me thinks.

“Compared to engines of the fourth generation, the fifth has added the ability to cruise supersonic motion - for this, the engine must have a variable bypass ratio. This requirement added one more specific parameter - specific fuel consumption at cruising supersonic. Also, the engine should have significantly less visibility in the infrared and radio wavelengths. This is achieved by a special design of the nozzle and air intake. A serious aspect of the new engine is also a reduction in the cost of the machine's life cycle - less maintenance costs, more overhaul life, ”Marchukov said about the new power plants.

>> I am at a loss to explain how VCE remains a taboo word after the designer has said the above... 5G engine needs to be VCE, and izd. 30 is in fact 5.5G... someone wants to join the dots for me here?

 

[icyplanetnhc (Steve)]

I am at a loss to explain how VCE remains a taboo word after the designer has said the above... 5G engine needs to be VCE, and izd. 30 is in fact 5.5G... someone wants to join the dots for me here?

This very interview has already been discussed here more than 2 years ago. I have even inquired about it, but actual Russian speakers have said that variable cycle refers to future developments, not the izdeliye 30 itself.

https://www.secretprojects.co.uk/th...opment-part-ii-2012-current.15626/post-347148

 

[TomcatViP]

Specific gravity would more refer to the volumic mass (that's what it is generally). Here, as taken as a design parameter it would refer to the property of the total mass of the engine divided by its volume and give an indication of how components and accessories design have evolved.

It is not the Thrust to Weight ratio that is the next parameter mentioned in the interview as quoted above by @LMFS

 

[overscan (PaulMM)]

“The difference between engines of different generations is manifested, first of all, in their specific parameters. There are several main parameters: specific gravity, specific thrust and specific fuel consumption per kilogram of thrust per hour. The generational change occurs with the simultaneous improvement of all these characteristics. In this regard, “Product 30” can even be attributed to the “5+” generation, since this engine was created taking into account domestic and foreign experience in the development and operation of fifth-generation engines. In the USSR, and then in Russia, this engine was “Product 20”. It was planned to install it on the MiG-1.44 MFI fighter being developed by the MiG corporation. Then “Product 30” appeared, ”said N + 1 Marchukov.

specific gravity is the ratio of density of a substance compared to an equal volume of water, typically.

Density vs. Specific Weight and Specific Gravity

An introduction to density, specific weight and specific gravity.

www.engineeringtoolbox.com

It is common to use the density of water at 4 C as a reference since water at this point has its highest density of 1000 kg/m3

Unless Russian usage of this term is different and is specific weight i.e. weight/thrust. If the figure of "better than 0.1" is correct for weight/thrust then it means t/w ratio is above 10, but nothing in this interview says 12:1.

Specific thrust which is mentioned next though is thrust to mass flow rate NOT thrust to weight and again is more of an indicative design parameter, this relates to supercruise optimisation. High specific thrust means its acting like a turbojet, giving more thrust for a given flow rate. This would normally come at a cost in specific fuel consumption, which Saturn mention effectively remains the same as AL-41F1.

“Specific fuel consumption opposes specific thrust. The best fuel consumption is obtained on civilian by-pass engines, but they have the least specific thrust due to the high by-pass ratio. In single-circuit engines, on the contrary, the specific thrust is high, but the consumption is also high. Due to the use of new designs and technologies in "Product 30" the specific consumption remained at the same level, but the specific thrust increased, "Marchukov said.

This directly suggests mass flow rate is probably not increased over AL-41F1, the thrust increase being attributable to improved engine cycle with greatly increased temperatures.

The interview says that AL-41F1S replaced 70% of AL-31F parts, and AL-41F1 replaced 80%. This suggests they are pretty similar, and its hard to think AL-41F1 is 150kg lighter from replacing 10% of parts unless they were very heavy parts.

 

[overscan (PaulMM)]

“Compared to engines of the fourth generation, the fifth has added the ability to cruise supersonic motion - for this, the engine must have a variable bypass ratio. This requirement added one more specific parameter - specific fuel consumption at cruising supersonic. Also, the engine should have significantly less visibility in the infrared and radio wavelengths. This is achieved by a special design of the nozzle and air intake. A serious aspect of the new engine is also a reduction in the cost of the machine's life cycle - less maintenance costs, more overhaul life, ”Marchukov said about the new power plants.

>> I am at a loss to explain how VCE remains a taboo word after the designer has said the above... 5G engine needs to be VCE, and izd. 30 is in fact 5.5G... someone wants to join the dots for me here?

Pratt & Whitney's F119-PW-100 is the foundational fifth generation engine and is not variable cycle as he well knows, so something doesn't add up. He definitely talks about VCE for the next generation after Izdeliye 30 later in the interview. Nothing conclusive in my opinion. He may be talking about the fifth generation as Izdeliye 20 which did have VCE.

 

[LMFS]

This very interview has already been discussed here more than 2 years ago. I have even inquired about it, but actual Russian speakers have said that variable cycle refers to future developments, not the izdeliye 30 itself.

Yes, I know it was discussed, that is why I did not quote it until fundamental questions appeared that called for the clarifications contained in it.

What is clear is that the 3 stream design is a development for the future, for what is called in Russia the 6G engine, see below. Russian speakers can help in determining if the translation above is correct, for the rest we have our own brains I guess...



@TomcatViP @overscan (PaulMM)

Specific gravity is defined in the article, a value consistent with T/W provided, and Marchukov also said it would be smaller in the izd. 30 than in izd. 117S. Given their sizes are equal, that would mean 1000 kg for the izd. 30, which does not make any sense. In general, density is not a technological parameter of engines and seems irrelevant to define a generation based on it. Besides:

The article:
Основных параметров несколько: это удельный вес, удельная тяга и удельный расход топлива на килограмм тяги в час.

weight	вес, масса, груз, тяжесть, нагрузка, значение

Should be clear now.

Specific thrust which is mentioned next though is thrust to mass flow rate NOT thrust to weight and again is more of an indicative design parameter, this relates to supercruise optimisation. High specific thrust means its acting like a turbojet, giving more thrust for a given flow rate. This would normally come at a cost in specific fuel consumption, which Saturn mention effectively remains the same as AL-41F1.

Yes, this is what we said and explained in the text. The name of the parameter and its interpretation is analogue to the Western one.

This directly suggests mass flow rate is probably not increased over AL-41F1, the thrust increase being attributable to improved engine cycle with greatly increased temperatures.

SFC is a thrust specific value, it says nothing about mass flow. It is logical to expect improved design of the compressor, apart from increased temperature.

The interview says that AL-41F1S replaced 70% of AL-31F parts, and AL-41F1 replaced 80%. This suggests they are pretty similar, and its hard to think AL-41F1 is 150kg lighter from replacing 10% of parts unless they were very heavy parts.

150 kg is a 10% of the weight of the AL-31F, I don't think it is crazy to think that you can gain that with 80% of the pieces being different. Nobody says the new pieces in 117S and 117 are the same, BTW, though it may seem logical to think so.

Pratt & Whitney's F119-PW-100 is the foundational fifth generation engine and is not variable cycle as he well knows, so something doesn't add up. He definitely talks about VCE for the next generation after Izdeliye 30 later in the interview. Nothing conclusive in my opinion. He may be talking about the fifth generation as Izdeliye 20 which did have VCE.

Or about YF120, since for both sides it has always been clear that the proper solution for a supercruising plane is a VCE, because otherwise the specific thrust demands of the supersonic flight regime force the engine to be inefficient in all other conditions. This is the way I interpret that statement, as a how things are from a theoretical point of view, despite of USAF having opted for the F119. At that time they were under no pressure from rivals and taking the lower risk option was a logical thing to do. They should have not relaxed that much though, Russia did not forget the lessons from izd. 20 and they may use the window of opportunity that US created for them. A 2 stream VCE may not be as advanced as the adaptive engine US is working full speed on, but it is better than having fixed BPR.

EDIT:

Unless Russian usage of this term is different and is specific weight i.e. weight/thrust. If the figure of "better than 0.1" is correct for weight/thrust then it means t/w ratio is above 10, but nothing in this interview says 12:1.

The statement about specific weight compared to 117S was linked some posts above, as per my calculation TWR would be ca 13:1. F135 is estimated at 12:1 from what I know, so this would be a bit better, but not something out of this world.

 

[overscan (PaulMM)]

@LMFS Specific gravity can't be "defined in the article" it is a standard engineering parameter. You can't just redefine it to mean something different, and the explanation of specific gravity in the article is presumably by the journalist. Either the wrong word was used or the meaning ascribed by the journalist was incorrect.

Also you seem to being deliberately obtuse in regard to your mass flow argument. The article specifically says specific thrust is increased. This means more thrust per unit of mass flow. If thrust of Izdeliye 30 is say 17500kg compared to 15000kg for Ideliye 117, thats 16.67 % increase in thrust. By the terms of this article, if the mass flow of Izeliye 30 is higher, then that reduces the increase in specific thrust. Its possible that mass flow is slightly higher (say, 5%), but if mass flow of Izdeliye 30 was 20% higher, for 17% more thrust, then specific thrust would be LOWER than Izd. 117. This is basic maths not advanced engineering.

This discussion belongs in the Propulsion forum and I will move the posts there eventually.

 

[LMFS]

@LMFS Specific gravity can't be "defined in the article" it is a standard engineering parameter. You can't just redefine it to mean something different, and the explanation of specific gravity in the article is presumably by the journalist. Either the wrong word was used or the meaning ascribed by the journalist was incorrect.

удельный вес means specific weight, the machine translation used the word gravity instead of weight, and the article provided the explanation about what they are referring too, even if you don't want to check the translation for accuracy. You are also ignoring the rest of the evidence I provided. The density of an engine is not a meaningful parameter and cannot be 0.1, unless you are willing to accept it weights 180 kg by your proposed definition...

Also you seem to being deliberately obtuse in regard to your mass flow argument. The article specifically says specific thrust is increased. This means more thrust per unit of mass flow. If thrust of Izdeliye 30 is say 17500kg compared to 15000kg for Ideliye 117, thats 16.67 % increase in thrust. By the terms of this article, if the mass flow if Izeliyie 30 is higher, then that reduces the increase in specific thrust. Its possible that mass flow is slightly higher (say, 5%), but if mass flow of Izdeliyie was 20% higher, for 17% more thrust, then specific thrust would be LOWER than Izd. 117. This is basic maths not advanced engineering.

I am not being obtuse, believe me. You are taking specific thrust, which refers to mil settings of which we have no values for the izd. 30, and mixing it with max thrust where such consideration does not apply, because the AB is in operation, burning all the oxygen that bypassed the core.

To get an increase in mil thrust both mass flow and specific thrust can and are normally increased, check for instance the different versions of the AL-31F in this regard.
Additionally, if f we talk about a VCE, then the situation is even more complicated, because there can be a setting with low BPR for highest mil / specific thrust and another for highest settings in AB.

As to the corresponding thread, yes please move the posts where you see them fit.

 

[overscan (PaulMM)]

@LMFS Specific gravity can't be "defined in the article" it is a standard engineering parameter. You can't just redefine it to mean something different, and the explanation of specific gravity in the article is presumably by the journalist. Either the wrong word was used or the meaning ascribed by the journalist was incorrect.

удельный вес means specific weight, the machine translation used the word gravity instead of weight, and the article provided the explanation about what they are referring too, even if you don't want to check the translation for accuracy. You are also ignoring the rest of the evidence I provided. The density of an engine is not a meaningful parameter and cannot be 0.1, unless you are willing to accept it weights 180 kg by your proposed definition...

Russian wikipedia says otherwise:

Удельный вес — Википедия

ru.wikipedia.org

Уде́льный вес — физическая величина, которая определяется как отношение веса вещества P к занимаемому им объёму V...

Specific gravity is a physical quantity, which is defined as the ratio of the weight of a substance P to the volume V occupied by it.

Weight per volume being decreased could correlate to higher thrust to weight but not directly.

Also you seem to being deliberately obtuse in regard to your mass flow argument. The article specifically says specific thrust is increased. This means more thrust per unit of mass flow. If thrust of Izdeliye 30 is say 17500kg compared to 15000kg for Ideliye 117, thats 16.67 % increase in thrust. By the terms of this article, if the mass flow if Izeliyie 30 is higher, then that reduces the increase in specific thrust. Its possible that mass flow is slightly higher (say, 5%), but if mass flow of Izdeliyie was 20% higher, for 17% more thrust, then specific thrust would be LOWER than Izd. 117. This is basic maths not advanced engineering.

I am not being obtuse, believe me. To get an increase in thrust both mass flow and specific thrust can and are normally increased, check for instance the different versions of the AL-31F in this regard. Say the thrust increase is 20% (to have rounder numbers), a 15% can come from specific thrust and a 5% from mass flow, for instance, or viceversa The increase of mass flow does not mean a reduction specific thrust, since it does not imply a higher or lower BPR.

As to the corresponding thread, yes please move the posts where you see them fit.

You have been arguing that Izdeliye 30 has a significantly higher mass flow rate and advanced opinions on the intakes being greatly oversized etc for supercruise optimisation for several pages.

When confronted by the engine designer saying that supercruise optimization depends on higher specific thrust not increased mass flow, doesn't that theory go out the window?

SFC being the same could mean a lower bypass ratio (for higher speciic thrust) combined with higher efficiency due to TET increase cancels each other out rather than being a hidden clue to VCE.

 

[icyplanetnhc (Steve)]

Technically, specific gravity should be a unitless parameter. I've only ever used it as a measure of propellant density; for instance, the specific gravity of JP-8 or Jet A is usually around 0.8 or so.

I am not being obtuse, believe me. To get an increase in thrust both mass flow and specific thrust can and are normally increased, check for instance the different versions of the AL-31F in this regard. Say the thrust increase is 20% (to have rounder numbers), a 15% can come from specific thrust and a 5% from mass flow, for instance, or viceversa The increase of mass flow does not mean a reduction specific thrust, since it does not imply a higher or lower BPR.

Frankly, none of this is really supporting your original argument that increased inlet size corresponds to superior supercruise performance. This is especially if the izdeliye 30 is meant to largely match the dimensions of the current AL-41F1, in which case I wouldn't expect the mass flow to significantly increase, not to the extent that the differences in inlet capture area would suggest.

The izdeliye 30 supposedly has a dry thrust of 11 metric tons compared to the AL-41F1’s 9 metric tons, a roughly 22% increase, but bear in mind these are static figures. Since the focus on the izdeliye 30 is specific thrust, a mass flow increase corresponding to the inlet size increase that you keep trying to argue frankly doesn’t add up.

 

[overscan (PaulMM)]

Technically, specific gravity should be a unitless parameter. I've only ever used it as a measure of propellant density; for instance, the specific gravity of JP-8 or Jet A is usually around 0.8 or so.

I am not being obtuse, believe me. To get an increase in thrust both mass flow and specific thrust can and are normally increased, check for instance the different versions of the AL-31F in this regard. Say the thrust increase is 20% (to have rounder numbers), a 15% can come from specific thrust and a 5% from mass flow, for instance, or viceversa The increase of mass flow does not mean a reduction specific thrust, since it does not imply a higher or lower BPR.

Frankly, none of this is really supporting your original argument that increased inlet size corresponds to superior supercruise performance. This is especially if the izdeliye 30 is meant to largely match the dimensions of the current AL-41F1, in which case I wouldn't expect the mass flow to significantly increase, not to the extent that the differences in inlet capture area would suggest.

Russian wikipedia says it can be dimensionless (volumetric density relative to the volumetric density of water) but doesn't rule out it being volumetric density.

 

[LMFS]

Specific gravity is a physical quantity, which is defined as the ratio of the weight of a substance P to the volume V occupied by it.

Weight per volume being decreased could correlate to higher thrust to weight but not directly.

Ok then, izd. 30 has a density lower than 0.1 and weights less than 500 kg, right?

You have been arguing that Izdeliye 30 has a significantly higher mass flow rate and advanced opinions on the intakes being greatly oversized etc for supercruise optimisation for several pages.

When confronted by the engine designer saying that supercruise optimization depends on higher specific thrust not increased mass flow, doesn't that theory go out the window?

Confronted? I am the one saying that izd. 30 is an engine designed for supercruise with the highest specific thrust in the world. That says nothing about the inlet's size and how it is designed for the different flight conditions. In the pages before we have seen the dependence of mass flow demand with speed and we know the characteristics of the atmosphere with altitude, that is a restriction placed on the engine by the inlet at given conditions. If the inlet does not provide the needed mass flow, the engine cannot work properly. It is obvious that if you want to have the highest thrust possible, you will work in both directions at the same time, specific thrust and mass flow at the engine itself, and then make sure that the intake is up to the task at the flight regime of interest.

BTW here is the chief designer saying the engine has the highest specific thrust, the conversation starts around 18:20:

View: https://www.youtube.com/watch?v=aDXNDA5xuS4


Please consider that captions are not correct, they translate as thrust to weight ratio but they are talking about specific thrust (удельная тяга)

SFC being the same could mean a lower bypass ratio (for higher speciic thrust) combined with higher efficiency due to TET increase cancels each other out rather than being a hidden clue to VCE.

Certainly, but consider the difference in mil thrust between a F119 and an AL-41F-1, that is ca. 11.5 tf vs ca. 9 tf, or almost a 30% difference, with F119's TIT to my knowledge still being unmatched by any engine other than F135 and corresponding to 5G standard. So Saturn went so much above the F119 and the 5G level, that surpassed them in specific thrust and still kept a much lower SFC of a very modern, relatively high BPR engine? That would be an extraordinary and unlikely technological leap IMHO, but I am not saying it is absolutely impossible. And again, when the designer talks in the terms that I quoted above the logical thing is to assume that VCE is indeed a possibility to consider, specially given it helps explaining some of the features claimed for the engine.

Technically, specific gravity should be a unitless parameter. I've only ever used it as a measure of propellant density; for instance, the specific gravity of JP-8 or Jet A is usually around 0.8 or so.

Exactly, I have never seen such parameter being used for engines, and I find it completely uninteresting, unlike specific weight as the inverse of thrust to weight ratio, which is indeed a cardinal performance indicator. Plus the resulting values are completely implausible.

Frankly, none of this is really supporting your original argument that increased inlet size corresponds to superior supercruise performance. This is especially if the izdeliye 30 is meant to largely match the dimensions of the current AL-41F1, in which case I wouldn't expect the mass flow to significantly increase, not to the extent that the differences in inlet capture area would suggest.

The max thrust suggest a certain increase of mass flow (again, if it is a VCE there might be additional complications to assess how this corresponds to higher mass flow) and then, my point is that the intake indicates to a design point clearly shifted to higher speeds and altitudes consistent with the highest end of supercruising performance.
To be totally sincere, I think Sukhoi just made damn sure with the intake design that it was not going to be the limiting factor, since they did not have certainties about the performance (or even existence) of the second stage engine by the time of the design. Therefore it being fully variable and very big, maybe as a way of compensating for potentially lower specific thrust at the engine level. With a specifically designed engine, they have pretty much piled all factors of propulsion performance one on top of another, and the results should be outstanding.

I take that you don't see it conclusive, that is fine with me.

As to engines of the same diameter having different mass flow, this is a constant in the technical evolution both within a generation or model and with the generational change. Do you expect the adaptive engines not to have higher mass flow than F135? Or AL-41F-1/1S not to have higher air consumption than AL-31F?

IMHO I have made my point and presented the evidence, coming directly from the mouth of the designer, now is up to everyone to decide what makes sense for them.

 

[Trident]

SFC being the same could mean a lower bypass ratio (for higher speciic thrust) combined with higher efficiency due to TET increase cancels each other out rather than being a hidden clue to VCE.

Not really, increasing TET improves thermal efficiency only, so long-haul airliner engines require both high TET and high BPR. Elevated TET alone means *even higher* specific thrust and at low speed, generating net thrust by high (c9-c0), where c9 is jet velocity and c0 aircraft forward flight speed, is inefficient. Propulsive efficiency is proportional to 1/(1+c9/c0), so for good values jet velocity needs to be matched well to aircraft speed - this is why turboprops work for commuter liners, despite generally downright primitive gas generators. The SFC figure Marchukov uses as a data point in his comparison to the AL-31F refers to subsonic cruise, so a condition where higher specific thrust offsets the gain in thermal efficiency by worsening propulsive efficiency.

The objective of a supercruise capable engine is to substantially increase specific thrust (jet velocity) to enable enough net thrust at supersonic speed to counter drag in dry setting, where otherwise (c9-c0) is marginal. This is at odds with good specific fuel consumption at lower speeds, where the widening disparity between c9 and c0 adversely affects propulsive efficiency. Which is the attraction of VCEs: they can adapt their cycle to maintain favourable specific thrust across a wider range of speeds. An unnecessary complication if higher TET would suffice to improve fuel consumption across the board!

From this you can deduce that maintaining the same subsonic cruise SFC as the AL-31F in an engine with significantly higher specific thrust is no mean feat, and may well require variable cycle tech. I agree that the Marchukov interview is ambiguous on this point regarding Izd.30 in particular, but it follows that the possibility cannot be excluded on this basis, either. If there are *other sources* that definitively establish that it is a fixed-cycle design I'll of course defer to that, but inferring solely from this source does yield potential indications of a VCE.

 

[icyplanetnhc (Steve)]

I would also venture to say that the increase in TIT is not solely for exhaust velocity purposes, as you can extract more work for the compressor and electrical power generation. Component matching will also be different so it’s difficult to say exactly what an increase in TIT will entail.

Despite being a fixed cycle, I do recall reading in some conditions (even in the supersonic part of the envelope), the YF119 was less thirsty than the variable-cycle YF120.

Also, the argument that specific thrust is being compensated for with mass flow in supercruise conditions is a non-sequitur. For dynamic thrust in supercruise conditions, mass flow is not correlated to specific thrust (an intensive property) and especially at supersonic speeds, additional mass flow won’t compensate for specific thrust or exhaust velocity. Not to mention that supercruise tends to not be the condition that demands maximum airflow.

 

[Trident]

Yeah, it's entirely plausible for a fixed-cycle engine to be more efficient at its primary design point (in the case of the F119 likely the Mach 1.5 supercruise condition, so the supersonic part makes sense too).

 

[tacitblue1973]

Pratt were happy with the fan design at design cruise conditions but accepted that the SFC at part throttle wasn't all that great. Was in AvWeek I read ages ago.

 

[stealthflanker]

Hmm and talking about Electrical power generator. The book "Airborne Early Warning System Concept" by Maurice W Long (Editor).

Discussed that an engine can have about 25% Extra rating for electrical power generation. Now i wonder how to make out of it from thrust information as that's usually what is available. Does that mean if an engine have a thrust of 10000 Kgf applying that 25% will mean that only 7500 Kgf will be available for thrust generation while the 2500 Kgf is absorbed by the turbine, shaft and the generator for electrical power generation ?

Or does it mean the engine actually capable of making 12500 Kgf. but 10000 is for thrust will the 2500 Kgf is for electrics ?

 

[TomcatViP]

Probably in shp.
Power is continuous thrust at cruise speed time the speed.
Then convert KW To shp.

Then use the ratio.

Here is a good explanation:

Aerospaceweb.org | Ask Us - Convert Thrust to Horsepower

 

[tequilashooter]

«Изделие 30»: в чём уникальность нового двигателя для российского самолёта Су-57

11 ноября 2016 года состоялся первый наземный запуск двигателя-демонстратора «Изделие 30». Силовая установка предназначена для оснащения российского истребителя пятого поколения Су-57. Сейчас этот самолёт летает на промежуточном агрегате АЛ-41Ф1. По оценкам разработчиков, «Изделие 30»...

russian.rt.com

On November 11, 2016, the first ground launch of the Product 30 demonstrator engine took place. The power plant is designed to equip the Russian fifth generation fighter Su-57. Now this aircraft flies on the AL-41F1 intermediate unit. According to the developers' estimates, the "Product 30" will significantly surpass modern engines in power and fuel efficiency. Experts believe that the carrier of the new power plant will be able to strike much faster and evade enemy attacks.

Five years ago, on the basis of the Lytkarinsky Machine-Building Plant (LM3), the first ground launch of the “Product 30” demonstrator engine, intended for the Russian fifth generation Su-57 fighter, took place .

On December 5, 2017, an aircraft with a new power plant made its debut flight, which lasted 17 minutes. It was run by the Hero of the Russian Federation, the chief pilot of the Sukhoi company, Sergei Bogdan.

Russian Industry and Trade Minister Denis Manturov said that the successful maiden flight of the Su-57 with the new engine would give an additional impetus to the fifth generation fighter program.

“This is proof of the high potential of the Russian aircraft industry, capable of creating highly intelligent advanced systems: a unique airframe, innovative digital filling, the latest engines,” Manturov emphasized.

LMZ is a subdivision of the A. Lyulka Experimental Design Bureau, which is part of the United Engine Corporation (UEC). The main task of LMZ is assembly, testing and fine-tuning of aircraft gas turbine engines and their units.

In non after-burning mode

"Product 30" is the designation of the so-called second stage engine of the fifth generation aircraft. Now the Su-57 flies on the AL-41F1 intermediate power unit ("Product 117"), which is also called the first stage engine. Its developer is the A. Lyulka Design Bureau.

Specialists of the enterprise attribute super-maneuverability, thrust-to-weight ratio, low visibility to enemy radars to the key characteristics of the AL-41F1.

The "Product 117" has an integrated oxygen-free plasma ignition system for the main and afterburner combustion chambers. It allows you to start the engine during flight without oxygen make-up. As experts interviewed by RT explained, providing an aircraft with oxygen requires the availability of appropriate infrastructure at the airfield and the placement of a certain set of equipment on board a combat vehicle.

In addition, the AL-41F1 became the first Russian aircraft engine to use a fully digital control system based on a domestic element base. The modification of the device will be integrated into the second stage engine as well.

“The AL-41F1 is the engine on which the Su-35S , the most modern Russian fourth-generation fighter jet, now flies . The power unit really has high performance, but it still belongs to the previous generation of aircraft engines, ”Dmitry Kornev, founder of the Military Russia portal, told RT.

As the expert explained, the AL-41F1, like other motors, “glows” quite strongly in the radar and infrared spectra. In addition, this engine is not able to provide cruising (normal) flight at supersonic speed in non-afterburner mode.

“Currently, supersonic flight leads to a significant increase in fuel consumption. As a rule, an aircraft is able to withstand supersonic sound for several minutes, and then, if it continues to fly at supersonic speed, it risks running into a fuel shortage. "Product 30" practically removes such a problem from the agenda, "Kornev emphasized.

According to the expert, cruising supersonic is becoming an important advantage in the modern theater of operations. In particular, it significantly improves the flight performance of the carrier.

“Such an aircraft is capable of avoiding enemy attacks much more rapidly, reaching the position of striking the enemy faster and safer, and intercepting and escorting foreign aircraft more quickly,” said Kornev.

According to the analyst's forecast, the second stage engine will increase the cruising speed of the Su-57 to about 1.5 Mach number. At the same time, in the RT commentary, Honored Pilot of Russia Major General Vladimir Popov estimated this figure at almost Mach 2.

"Special offer"

Little is known about the characteristics of Product 30. Earlier on the air of Sputnik radio, UEC representative Anton Chechukov said that in comparison with the AL-41F1, the thrust of the second stage engine would be increased to 17.5-19.5 tons. The engine would also be distinguished by increased fuel efficiency and a reduced life cycle cost.

In 2018, in an interview with the Zvezda TV channel, General Designer - Director of the A. Lyulka Design Bureau Evgeny Marchukov said that in terms of specific thrust, the Product 30 would surpass all foreign analogues. As a result, the carrier will be able to take off faster, gain altitude, and perform maneuvers with a large overload during air combat.

In March 2020, an article was published on the website of the Science and Technology journal with an analysis of the technical solutions implemented in Product 30. It reported that the oxygen-free ignition system is installed on modernized nozzles, which ensure the ignition of the fuel immediately after it enters the combustion chamber.

Thanks to this approach, the optimal combustion mode is maintained and the so-called torching is excluded - the ejection of a column of fire from the nozzle due to excess fuel in the combustion chamber. Also, the second stage engine is equipped with a new nozzle with thrust vector control function.

The article noted that the electronic-digital control system "Product 30" significantly simplifies the work of the pilot and facilitates the process of tuning the engine. She receives a command from the pilot, and then executes it "taking into account the current parameters and various factors."

Vladimir Popov stated that Russian designers have significantly changed the thermodynamic process used in previous generations of jet engines.

“This is due to the special ionization of the air flow, the air-fuel mixture. The afterburner is located in a traditional combustion chamber. In "Product 30" there will be no afterburner as such. Instead, a ring system appeared, which will create the combustion of fuel without its additional supply through pumping systems, which will be more economical. It is planned to increase the efficiency from fuel combustion by 1.2—1.5 times, ”the expert said.

Also, as Popov noted, the engine of the second stage provides for a complex of new fuel automation, which will regulate the flight mode due to thrust. According to him, in the non-afterburning mode, the thrust of the "Product 30" will be 1.5 times more than that of today's engines.

“In addition, technological and operational characteristics have been improved in the new engine. Now the testing process is underway. Upon their completion, I think, our industry will cope with setting up the production of the unit. The design office and manufacturing plants work simultaneously, so there should be no problems with production, ”Popov explained.

Answering a question from RT about the prospects for exporting "Product 30", the major general said that with the deployment of serial production, it is reasonable to focus on equipping the second stage of the Russian aircraft fleet with engines. In the future, as Popov argues, Russia can export the power unit to China, India, Turkey, Argentina and Brazil.

“There are too many technological positions that are inappropriate to give abroad. For now, it is in the interests of the Russian Federation to use "Product 30" to ensure our defense capability and combat readiness of the Aerospace Forces. Export is possible in five years after the start of production of this unit. Now we will continue to offer other countries deeply modernized samples of the previous generation, ”Popov said.

Dmitry Kornev adheres to a different point of view. In his opinion, Moscow can start exporting "Product 30" and aircraft with it to the most reliable partners in the area of military-technical cooperation. The expert is confident that such products will be very popular in the global arms market.

The interlocutor of RT recalled that Russia is actively promoting its fighters on the international market, so the aircraft flying on the "Product 30" will definitely become a "unique offer." According to Kornev, the new unit can be installed not only on the Su-57. With minor modifications, the second stage engine will most likely be mounted on the Su-35 and Su-34 as part of their modernization programs.

“Creation of jet engines for combat aviation is a most difficult technological task for any state. In my opinion, testing and work on the "Product 30" will continue for several more years. All these gains are not in vain. Our country is close to getting the first power unit since the 1990s, practically devoid of Soviet ancestry. "Product 30" will serve for at least 40 years and will certainly become a platform for the development of various modifications, "summed up Kornev.

 

[TMA1]

They have been very quiet about the izd 30. There have not been any statements in the past two or three years detailing need for delays which is a good sign. The izd 30 is one of the most important projects for the russian MIC. If all works out, it will be the basis for even more advanced engines.

 

[tequilashooter]

I was already impressed with the ranges of the 1st stage engines when comparing them to other aircrafts with now a supercruise capability added with better fuel efficiency and if what I am reading is correct on the fuel combustion efficiency the range might be better. The other engine projects are three stream cycle and detonation engines.

 

[icyplanetnhc (Steve)]

My own measurement with blueprints. To be honest, I am not sure anymore whether the exact value was 20 or 30%, but it was quite significant in any case.

The oversized intakes of the Su-57 tell me quite a different story from what you are saying, what is your explanation to such big capture area?

Just so that I can avoid taking the other thread off topic, for all this argument of a significant difference in capture area, based on properly scaled front views of the Su-57 and the F-22 from official sources (Sukhoi's patent and Lockheed Martin), I'm getting a difference on the order of 5%. Mind you, in propulsion terms, 5% is not insignificant, but the actual flow field the inlets see will be different from a head on view, and given the functions that the inlet flow serves in addition to propulsion, and general inlet performance at supersonic speeds, frankly this difference is not worth noting.

EDIT: Intake areas outlined in red, both are roughly 0.7 sqm in terms of frontal capture area; statements about the Su-57 having greatly “oversized intake" compared to the F-22 are frankly wrong.