when will the lunacy end ?

[rb1957]

Reported in Flight, from a prestigious establishment as Cranfield, the latest in fuel cell engine design ...

At first I thought those "enormous" red things were just a picture, highlighting some internal "gubbings" ... but no ...

Surely, people can see the insanity of this design ? The losses from those heat exchangers must, Must, be massive. and given that the thermal demand (whatever that is, 'cause I don't know) will vary significantly with altitude and outside temperature, then "surely" a more sophisticated installation (more like a P-51 radiator, with a controlled outflow) would be more sensible.

And before people start in with ... this is just a demonstrator, the article crows about the fantastic design this embodies, how ...
"This integration required meticulous planning, iterative design, and close coordination with partner Reaction Engines, to ensure optimal performance,"
and "The decision was taken early on in the programme that before proceeding to ground and flight test, we had to ensure that we had solved the packaging and thermal management challenges that underpin the commercial viability of the technology. Now that this significant milestone has been achieved, ..."

sigh ...



"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

Sigh, its from an academic institution. They don't need to worry about any practical issues. Looks scabbed onto an existing aircraft for demo purposes.

 

[GregLocock]

Fuel cells are about 60% efficient so you've got 40% of output power available as rather low grade (temperature) energy. My guess is they'd mount the fuel cells directly in the ducts and get Meredith effect thrust from them. As to whether an internal duct on the fuselage is better tan pods, one has to guess they've done some sums.

Looks like it may just be for the prototype

Removing the heat that a HFCS produces is one of the key challenges. CAeS’ demonstrator will have two Reaction Engine heat exchangers mounted underneath the converted nacelle, sized to reject the full amount of heat produced.

Not representative of the production solution, the design will be optimised into a smaller configuration more akin to the existing air intake for the production version.

The larger than production version heat exchangers also pose a drag issue for the demonstrator hydrogen aircraft, and as such the aircraft will house the pressurised gaseous hydrogen fuel tank inside the fuselage.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[rb1957]

Cranfield have a better reputation than "an academic institution". The nacelle packaging does look impressive. The whole power-train too, but those god awful radiators !? A radial radiator, a la Fw190D, would be a much better choice. Surface radiators on the nacelles sidewalls ... anything else ...

And, yes, this is a demonstrator but geeze ...

But it does make me wonder why a fuel cell generates so much heat ? so is it heat generated by the combustion of H2 (instead of av gas) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[GregLocock]

No it is more like a lead acid battery. At the moment PEM is the main tech used.

https://en.wikipedia.org/wiki/Fuel_cell

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[rb1957]

ok, "burnt" may not have been the best word ... but the chemical reaction must be highly exothermic (one might say stupidly so) ... akin to burning the H2.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[enginesrus]

A jetA burning recip ICE is a much better fuel saving idea?

 

[rb1957]

one would think that the drag of those radiators would require a lot more energy to achieve the same result (airplane cruising speed).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[enginesrus]

Yes if propellers are again the future of powered flight, minds well have high efficient jet A burning, diesel recips, something compact like the Achates on its side.

 

[WKTaylor]

Electric-only flight is coming... starters... light reading...

SAE PT-187 THE ELECTRIFICATION OF CIVIL AIRCRAFT AND THE EVOLUTION OF ENERGY STORAGE

SAE PT-192 The Use of Electric Batteries for Civil Aircraft Applications

SAE R-462 ELECTRIC AIRCRAFT SERIES - Fundamentals of Electric Aircraft

SAE T-135 Electric Flight Technology: The Unfolding of a New Future

SAE TU-003 ADVANCES IN ELECTRIC PROPULSION

SAE J1715 Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) Terminology

Hmmmmmm reminds me of the truisms...

"Lead, follow or get-out-of-the-way."

"The only constant is change."

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov