Net Zero Aviation Fuels - Royal Society
Discussion
I came across this & thought it might be if interest to some aircraft enthusiasts here.
https://royalsociety.org/-/media/policy/projects/n...
It's an interesting read but changes seem to be a long way off.
I'd never think of ammonia being suitable as a fuel.
The Rolis Royce engine being run on hydrogen was new to me.
https://royalsociety.org/-/media/policy/projects/n...
It's an interesting read but changes seem to be a long way off.
I'd never think of ammonia being suitable as a fuel.
The Rolis Royce engine being run on hydrogen was new to me.
When I worked at the National Gas Turbine Establishment we had test facilities which replicaticated the pressure and temperature of air entering a jet engine in flight. The air had to be cooled to replicate temperatures at cruise altiude, so we had a large cooling plant using ammonia (edit: not nitrogen) as the operating fluid. We were told that if this failed, the resulting ammonia cloud would be likely to kill most people in the town a couple of miles downwind. For this reason ammonia may well be too hazardous to use as an aviation fuel.
Edited by GliderRider on Wednesday 1st March 19:52
julianm said:
There are a lot of calculations about using `green` electricity to generate H2 from water.
I was referring to GliderRider's comment: 'we had a large cooling plant using nitrogen as the operating fluid. We were told that if this failed, the resulting ammonia cloud would be likely to kill most people in the town a couple of miles downwind'.Nitrogen and air don't make ammonia - air doesn't contain hydrogen.
Believe it or not it was the gas of choice in the 1940`s!
Lovely old video of the wonder of the fridge here: https://www.youtube.com/watch?v=KDPgGDCdAo4
Lovely old video of the wonder of the fridge here: https://www.youtube.com/watch?v=KDPgGDCdAo4
Simpo Two said:
julianm said:
A recirculating cooling plant could have used compressed ammonia - expect that would have been the issue.
Aha compressed ammonia not nitrogen, that could make sense.CFC-free, but presumably not safe enough for domestic freezers?
Simpo Two said:
Ammonia is NH3. Where would the hydrogen come from to make it?
It's already done in vast quantities all over the world with the Haber-Bosch process: https://en.wikipedia.org/wiki/Haber_processKrikkit said:
Simpo Two said:
Ammonia is NH3. Where would the hydrogen come from to make it?
It's already done in vast quantities all over the world with the Haber-Bosch process: https://en.wikipedia.org/wiki/Haber_process
Interesting that hydrogen fuel would require 2.4-3.4 times the UK's current total renewable electricity generation capacity to service aviation.
I think part of the problem is that we have the wrong aircraft. They're much too fast and power hungry, which is the right thing to design to suit jet engines which drink a lot of fuel whenever they're running whatever the power setting and only become remotely efficient at converting fuel to thrust when run at high power settings. To have enough power for takeoff and climb especially with an engine out you get big engines, and to use the fuel you're going to burn either way you might as well blatt along at Mach 0.8 at high altitude to use up the power in a productive way.
If burning the hydrogen directly you'd have similar efficiency characteristics and end up needing the same energy.
If however you were using hydrogen to run electric motors the efficiency behaviour would be drastically different. Unlike a jet engine, 10% power from an electric motor uses 10% electrical power, or in other words your electricity source can last 10 times as long. You can have big motors for take off and climb power and choose to cruise a bit slower at much reduced power and use a lot less juice in between.
It would still be a lot more electrical power than the UK's power generation infrastructure has to spare at the moment though certainly.
I think part of the problem is that we have the wrong aircraft. They're much too fast and power hungry, which is the right thing to design to suit jet engines which drink a lot of fuel whenever they're running whatever the power setting and only become remotely efficient at converting fuel to thrust when run at high power settings. To have enough power for takeoff and climb especially with an engine out you get big engines, and to use the fuel you're going to burn either way you might as well blatt along at Mach 0.8 at high altitude to use up the power in a productive way.
If burning the hydrogen directly you'd have similar efficiency characteristics and end up needing the same energy.
If however you were using hydrogen to run electric motors the efficiency behaviour would be drastically different. Unlike a jet engine, 10% power from an electric motor uses 10% electrical power, or in other words your electricity source can last 10 times as long. You can have big motors for take off and climb power and choose to cruise a bit slower at much reduced power and use a lot less juice in between.
It would still be a lot more electrical power than the UK's power generation infrastructure has to spare at the moment though certainly.
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