HySIITE, the Hydrogen Steam Injected, Inter‐Cooled Turbine Engine

[UpForce]

P&W to develop novel hydrogen engine in US government-backed project

Pratt & Whitney is to develop a novel hydrogen-burning engine that will cut carbon dioxide emissions to zero, slash nitrous oxide emissions by 80% and reduce fuel consumption for next-generation single-aisles by 35%.

www.flightglobal.com

A P&W project, hydrogen burning, steam injected and intercooled engine envisioned to increase efficiency (single aisles 35%), evade (at least direct) carbon dioxide emissions entirely and cut nitrous oxide emissions (80%). Not an incremental approach but aiming for something greater then. Water vapor at least partially recovered - could we call this a hybrid steam engine? US DoE funding quite modest at this stage, only $3.8 million but it's a start anyway.

 

[Nik]

So, it carries cryo-hydrogen fuel, and a tank of water as augment ??

Woe !! My Google-Fu hath failed me: All finds went to article referenced above, or this thread. And, yes, auto-corrected, to eye-drops...

 

[Trident]

Sounds more like what would be termed exhaust gas recirculation in the automotive industry.

 

[Dagger]

This is typical for the tricks that the hydrogen maffia uses: they take some old ideas and combine them with the use of hydrogen so that they can claim that the benefits are all due to the use of that magical hydrogen.

Using an intercooler for the compressor is not new, it is very basic and can be found in decades old text books.
Using steam injection into the combustion chamber is nothing new either.
Both could also be applied in a jet engine burning kerosene, but one could not collect a subsidy for that.
The efficiency of a jet engine is not determined by the fuel that is burned. Pressure ratio is what matters.

Thanks to global warming all kind of old and impractical ideas can now be promoted as being green, and associated subsidies collected.

Don't fall for it. Everything, and I mean EVERYTHING, you read about the benefits of using hydrogen as a fuel is either a lie or an extreme form of exaggeration.

 

[Trident]

Using an intercooler for the compressor is not new, it is very basic and can be found in decades old text books.

Sure, but LH2 is a better heat sink than anything available on a non-cryogenic hydrocarbon fuel vehicle. The Reaction Engines SABRE for example would not be viable with any other fuel.

Using steam injection into the combustion chamber is nothing new either.

Here too, recovering steam from the exhaust is easier than with fossil fuels.

Both could also be applied in a jet engine burning kerosene, but one could not collect a subsidy for that.

And if we didn't need to remove CO2 from the picture entirely, they probably would be, in the next generation of kerosene engines. They might well be in there because they were going to be used anyway, not necessarily because of the conjuction with hydrogen. Also, if past experience is anything to go by, the OEM likely WOULD collect subsidies regardless. The research feeding into the current crop of kerosene turbofans was heavily subsidized under various US and EU initiatives.

The efficiency of a jet engine is not determined by the fuel that is burned. Pressure ratio is what matters.

Increases in which could be enabled by intercooling (compressor exit temperatures are starting to push material limits). Which is precisely why this technology would probably find its way into a next-gen engine sooner or later, no matter the type of fuel. Hydrogen may just be what moves it into the "sooner" as opposed to "later" category.

Don't fall for it. Everything, and I mean EVERYTHING, you read about the benefits of using hydrogen as a fuel is either a lie or an extreme form of exaggeration.

There is a lot of magical thinking to be sure, but I'd say you're rather guilty of an extreme form of exaggeration here yourself I do get where you're coming from, and in most instances we'd likely agree, I just think you are carrying the cynicism a bit far.

 

[Zoo Tycoon]

The Reaction Engines SABRE for example would not be viable with any other fuel.

Without wishing to redirect the thread;- At a talk given by RE just over two years ago there was a mention that alternative to hydrogen were being a investigated, but said no more. So in the Q&A I asked if deep cooled Methane (-182C) would work;- His response was “I’m unable to comment”. Given it has 5 times the volumetric energy density the vehicle gets radically smaller, has less drag so needs less propellant.

 

[Zoo Tycoon]

There is a lot of magical thinking to be sure, but I'd say you're rather guilty of an extreme form of exaggeration here yourself I do get where you're coming from, and in most instances we'd likely agree, I just think you are carrying the cynicism a bit far.

These articles only tell of how wonderful LH2 is and never the flip side;- liquid helium pre cooling to avoid thermal shock, loading loss during refuelling, the formation of solid air at any insulation break down, it’s poor volumetric energy density, managing a system that constantly leaking, toxic Indium seals, what leaks out in an enclosed space will find an ignition source (even Helium purging hasn’t worked in the past), and finally, every kilogram that leaks into the atmosphere maybe has the same global warming as 200 kg of CO2.

What’s there not to like?

Edit He2 corrected to Helium.

 

[Nik]

He2 ? Please confirm as typo...

Also, I take it the 200 kg equivalent figure is due to formation of cirrus contrails changing effective 'surface' albedo...

FWIW, I'm under a 'fly-way' for trans-Atlantic route. During 'covid lock-down', was so very, very weird to see so very few contrails. Usually, by mid-afternoon, a morning's clear sky would become a palimpsest. But, Covid kept it clear save for one or two rare birds...

Tangential, did you notice the Chem-Trail 'q-spiracists' failed to claim any benefit from the severe reduction in flights ??

 

[Zoo Tycoon]

Yes Helium ;- With LH2 turbo machines you can’t just push in a highly combustible, deep cryogenic liquid into a warm space occupied by air;- the temperature gradient across precision parts jams them solid, the air freezes solid, and oxygen then present a hazard. So what the rockets do is they purge with Helium steadily dropping the temp until the volume is filled with Liquid Heluim. Then it’s ready for LH2. Fine for an occasional rocket, but is there enough Helium on the planet to support commercial aviation?

As for the other mention of Helium ;- The TU155 abandoned its LH2 trial after flight no 4. The LH2 tank sat in a compartment being purged with Helium to suppress the combustion of leaked hydrogen and oxygen;- wide combustion range and minimum ignition energy lower than a visible spark.

The 200 X factor;- No not contrails, it’s explained in the links below;-

https://www.eceee.org/all-news/news/scientists-warn-against-global-warming-effect-of-hydrogen-leaks/

Scientists warn against global warming effect of hydrogen leaks

Recent studies suggest that hydrogen could be a contributor to the greenhouse effect when it leaks through infrastructure.

www.euractiv.com

Edit Helium correction - every days a school day.

 

[Dagger]

Using an intercooler for the compressor is not new, it is very basic and can be found in decades old text books.

Sure, but LH2 is a better heat sink than anything available on a non-cryogenic hydrocarbon fuel vehicle. The Reaction Engines SABRE for example would not be viable with any other fuel.

Ambient air is cold enough for the compressor intercooler. For example in this way:



I don't think that P&W intends to use LH2 for the intercooler. Maybe 50 years from now but not on the first jet engine family using intercooling.

Adding a recuperator like in this figure would also save fuel. Strange that P&W didn't include that in their HySIIT too. Why stop half way when drumming up a story for subsidies?
Pathetic that a big company like P&W is fishing for a $3.8 million DoE subsidy to do development work that they should be doing anyway to stay competitive.

Intercooling could already have been used in jet engines decades ago, but apparently the additional weight, complexity and cost of such engine is not justified by the fuel saving due to the low (taxfree) price of kerosene. Same for the recuperator. It's all technically feasible but not economical (it would add weight, complexity and cost to the engine) as long as kerosene is not taxed to make it as expensive as the gasoline and diesel that cars use.

 

[Nik]

"He2 ? Please confirm as typo..."

Helium is atomic weight 2, but a monomer unless under extreme conditions, not found here. Where-as Liq. Hydrogen is dimer, H-H.

No big deal...

 

[Arjen]

Helium has atomic number 2.
Two naturally occurring stable isotopes, helium-3 and helium-4.
Helium-2 has a half-life of ≪ 10^−9 s - highly unstable.

Isotopes of helium - Wikipedia

en.wikipedia.org

Dimer and trimer helium exist at extremely low temperatures:

Helium dimer - Wikipedia

en.wikipedia.org

Helium trimer - Wikipedia

en.wikipedia.org

I am not sure what He2 refers to - helium-2 or dimer helium. Both are quite exotic.

 

[Nicknick]

Unfortunately, the article is not precise enough to understand what is really meant. Intercooling or precooling of the air by liquid hydrogen seams feasible, because the compressor work can be significantly reduced. It might also be considered to expand the than pre heated hydrogen and inject it as hydrogen steam in to the combustion chamber (instead of a liquid injection). Of course, the hydrogen could be heated by exhaust gas prior to the combustion. Hydrogen has an extremely high heat capacity (14.300 Kj/kg*K) so that a large amount of heat could be recovered. The Hydrogen could also be used in a high-pressure steam (hydrogen steam, not H2O) cycle, so it would be used for intercooling, heat recovery and high to middle pressure expansion into the combustion chamber. Due to the intercooling the combustion might be stoichiometric or slightly understoichiometric to supress NOx emissions (low compression temperature).

Such a high-pressure hydrogen process with heating and expansion into the combustion chamber by a turbine reminds me to the space shuttle rocket propulsion. The main engines of the space shuttle did something very similar by pumping liquid hydrogens to a high pressure, using it to cool the combustor/nozzle and expanding it in a turbine before it entered the combustion chamber (the turbine was used to drive the fuel/oxygen pumps).

I don’t believe water based steam is a real option, because you have to use giant coolers to condense it out of the exhaust stream or you need to carry a huge quantity of liquid water in the plain, both is not realistic.

 

[X-39]

Article is paywalled, but i got this snippet from Wikipedia:

Pratt & Whitney wants to associate its geared turbofan architecture with its Hydrogen Steam Injected, Inter‐Cooled Turbine Engine (HySIITE) project, to avoid carbon dioxide emissions, reduce NOx emissions by 80%, and reduce fuel consumption by 35% compared with the current jet-fuel PW1100G, for a service entry by 2035 with a compatible airframe.[23] On 21 February 2022, the US Department of Energy through the OPEN21 scheme run by its Advanced Research Projects Agency-Energy (ARPA-E) awarded P&W $3.8 million for a two-year early stage research, to develop the combustor and the heat exchanger used to recover water vapour in the exhaust stream, injected into the combustor to increase its power, and into the compressor as an intercooler, and into the turbine as a coolant.[23]

P&W sees 2035 service entry potential for revolutionary hydrogen powerplant

Pratt & Whitney is hopeful that a revolutionary hydrogen combustion system that uses water vapour recovered from the exhaust stream to increase engine efficiency could be ready for service entry by 2035.

www.flightglobal.com

 

[Nicknick]

OK, next try, maybe they do the intercooling with air and do the condensation of the water by cooling down a bypass of the exhaust stream with liquid hydrogen by a heat exchanger. This would cover the heat for gasification of the hydrogen and partial cooling of the exhaust gases as well so that water will condense. The intercooling and water injection would decrease the combustion temperature significantly and enable a stoichiometric combustion (which eases the condension)

 

[Dagger]

Gasturbines and jet engines use a lot more air than required for the combustion.
Most of the air from the compressor bypasses the combustors and mixes with the combustor exhaust gases before entering the turbine. There is a limit to the turbine inlet temperature and that determines how much air needs to be compressed.

Combustion temperature has impact on NOx formation: the higher the more NOx.
Recycling some water from the exhaust can lower NOx.

Intercooling of the compressor will improve fuel efficiency by several percentage points, but not by 35 %.
Condensing large amounts of water from the exhaust, pump it to combustion pressure, vaporize it into steam to send it through the turbine works in theory and could maybe be achieved in a gasturbine on the ground, but doing that in a jet engine would make it bulky and heavy, so forget it.

Jet engine manufacturers always claim that their new engine uses 20 - 30 % less fuel than existing engines,
but what they mean is: compared to the oldest engines still in uses that the new engine will replace.

All kind of tricks can be used to improve the fuel efficiency of a jet engine, at least in theory,
but they have little or nothing to do with the kind of fuel the engine is burning.

 

[Nicknick]

Its not wrong what you saying, but interccoling and water injection reduces the combustion temperature significantly, maybe to the point were a stoichiometric combustion is possible (it might be a staged combustion).

Condensing water out of the exhaust is next to impossible with conventional fuel, but not with liquid hydrogene. The very low temperature and relativ high (compared to air, not water) vaporization heat plus very high heat capacity of gazous hydrogene could make it practical (not in the full flow) because the heat exchanger can be very small. Also a air/fuel ratio close 1 and a fuel which produces much more water than hydrocarbons will help a lot.

I thought about it again and I came to the conclusion that intercooling might be done by injecting water (at least a part of it) instead of using ait/air heat exchangers. This would be much more efficient than spraying liquid water into the combustion chamber.

 

[Dagger]

Let's see what P&W writes on their own website:

"The Hydrogen Steam Injected, Inter‐Cooled Turbine Engine (HySIITE) project will use liquid hydrogen combustion and water vapor recovery to achieve zero in-flight CO2 emissions, while reducing nitrogen-oxide (NOx) emissions by up to 80 percent and reducing fuel consumption by up to 35 percent for next generation single-aisle aircraft."

Pratt & Whitney Awarded Department of Energy Project to Develop Hydrogen Propulsion Technology

EAST HARTFORD, Conn., February 22, 2022 – Pratt & Whitney has been selected by the U.S. Department of Energy (DoE) to develop novel, high-efficiency hydrogen-fueled propulsion technology for...

newsroom.prattwhitney.com

So the liquid hydrogen is not vaporized, and therefor not used as cooling medium, but is burned as a liquid presumably to reduce the adiabatic flame temperature so as to minimize NOx.
Also no liquid water is condensed from the exhaust, but water vapor is recovered (not clear how) and presumably recycled to the burners to reduce NOx. Recycling water vapor will cost energy so not save fuel.

As usual when hydrogen is involved: a lot of blah blah and claims that are not really the result of hydrogen use but could also been achieved when other fuels were used.

When reading about H2 always beware for BS.

 

[Nicknick]

We will see, as you said, there is a lot of bla bla and I don t see a realistic way to condens the water out of the exhaust other than by cooling with liquid hydrogene (I might be wrong). Just because the public relation department wrote something different on the website, it must not be the truth....

The heat required for heating up the hydrogen in the combustion chamber is lost for propulsion, therefor a liquid hydrogen injection is not a very logical approach for maximum efficienty. Despite that, the temperature difference between liquid hydrogen and burning hydrogen within few milimeters could be demanding for the materials, what will happen if a drop of liquid hydrogen hits a hot wall?

Indeed, BS is certainly a danger when it comes to H2...