Thoughts on Diesel Fuel

There was a prototype nuclear aircraft engine, and you can go see it in the parking lot for EBR-1, but I believe air was the working fluid. http://www.roadtripamerica.com/GettingO ... /EBR-1.htm

Do turbines need better materials than reciprocating engines? Isn't there an advantage to reciprocating engines if you need sort-of-OK efficiency at a wide range of speeds?

Expert snuggler wrote:There was a prototype nuclear aircraft engine, and you can go see it in the parking lot for EBR-1, but I believe air was the working fluid. http://www.roadtripamerica.com/GettingO ... /EBR-1.htm

Cool! Thanks!

Do turbines need better materials than reciprocating engines? Isn't there an advantage to reciprocating engines if you need sort-of-OK efficiency at a wide range of speeds?

Materials: not really. If you look into the jumo 004, they designed it initially using higher grades of steel (something that I don't the Charis has *yet*) but they moved to mild steel for the B version since there wasn't enough nickel available at that point in the war. The hard parts are the tail end of the combustion chamber and the turbine at the back (as opposed to the compressor at the front), but these are totally solvable problems with bleed air. The combustion chamber typically burns about 30% of the air, so the remaining 70% is available to mix in to cool the result. The turbines blades in the jumo004 were hollow, with some of that 70% unburned air blowing through it. Personally, I've been wondering if a ceramic turbine would work. The heat would not be an issue, but ceramics can be brittle, so maybe the RPMs would be a problem...
As for throttling, yes, there are some efficiency issues with a throttled turbine, but really, that's pretty much only relevant to a car in traffic. Airplanes don't really use a wide range of powers: high power for take-off, about 75% for cruise, and idle for descents. Jets basically run at full speed all the time... However, in the 50s, Chrysler did devellop a turbine engine that worked in cars. Its efficiency was comparable to similarly powered engines of the time, and there's speculation that an improved combustion chamber would have made a big difference. Unfortunately, they never took the engine to mass-production.

MTO wrote:

Expert snuggler wrote:There was a prototype nuclear aircraft engine, and you can go see it in the parking lot for EBR-1, but I believe air was the working fluid. http://www.roadtripamerica.com/GettingO ... /EBR-1.htm

Cool! Thanks!

Do turbines need better materials than reciprocating engines? Isn't there an advantage to reciprocating engines if you need sort-of-OK efficiency at a wide range of speeds?

Materials: not really. If you look into the jumo 004, they designed it initially using higher grades of steel (something that I don't the Charis has *yet*) but they moved to mild steel for the B version since there wasn't enough nickel available at that point in the war. The hard parts are the tail end of the combustion chamber and the turbine at the back (as opposed to the compressor at the front), but these are totally solvable problems with bleed air. The combustion chamber typically burns about 30% of the air, so the remaining 70% is available to mix in to cool the result. The turbines blades in the jumo004 were hollow, with some of that 70% unburned air blowing through it. Personally, I've been wondering if a ceramic turbine would work. The heat would not be an issue, but ceramics can be brittle, so maybe the RPMs would be a problem...
As for throttling, yes, there are some efficiency issues with a throttled turbine, but really, that's pretty much only relevant to a car in traffic. Airplanes don't really use a wide range of powers: high power for take-off, about 75% for cruise, and idle for descents. Jets basically run at full speed all the time... However, in the 50s, Chrysler did devellop a turbine engine that worked in cars. Its efficiency was comparable to similarly powered engines of the time, and there's speculation that an improved combustion chamber would have made a big difference. Unfortunately, they never took the engine to mass-production.

The limiting metal wasn't nickel - it was chromium. This was also an issue for the German artillery as it is essential for armor piercing shells. Their fix was to plate the turbine blades with aluminum. When heated to combustion temperatures this oxidizes to alumina - a reasonable high temperature ceramic. The down side is that ceramics don't like being heat cycled - they shatter.
Turbines and diesels have one major limitation - low speed torque. Unlike a reciprocating steam engine (which produces maximum torque at zero speed) in wheeled vehicles you can't directly connect the engine to the wheels. You need a clutch with significant slippage to keep the engine above its idle speed as the vehicle moving. Step down gearing may also be needed.
To achieve this you have a number of choices, electric - either DC or in more modern systems AC variable frequency (diesel electric trains and hybrid cars), gear trains with either a conventional clutch or torque converter (hydraulic clutch)(standard practice in 20th century cars) or hydraulic drive with variable volume pumps and/or variable volume hydraulic motors sometimes with hydraulic accumulators to provide extra starting torque (and regenerative braking)(used in diesel hydraulic locomotives (particularly shunters)) and some hybrid trucks). If diesel engines get used for locomotives under the proscriptions only the last two would be a viable option. The hydraulic drive would be the most reliable of the two options under high variable load conditions. (Mechanical clutches are more efficient at constant speed at the expense of high wear at start-up and intermittent motion).

MTO wrote:..snip..
Personally, I've been wondering if a ceramic turbine would work. The heat would not be an issue, but ceramics can be brittle, so maybe the RPMs would be a problem...

In the latest generations of jet engines, they use hollow titanium turbine blades which are coated with ceramics. This combination makes them stand up to very high temperatures. To make the turbine blades hollow they heat them up after the initial casting and machining and then injects inert gas into them which makes them "blow up". The process makes the blades extremely durable compared to initially casting them hollow.

Alas, the current techlevel on Safehold is nowhere near this sophistication.

Weird Harold wrote:

TheOneLogician wrote:1) Good-bye steam engines. Massively improved engine efficiency means that railroads are about to become much more popular.

Diesel only locomotives were never efficient or successful. It wasn't until Diesel-Electric locomotives were perfected that "Diesels" displaced Steam locomotives. Safehold isn't getting "Diesel" locomotives displacing Steam locomotives until the OBS is neutralized and the Proscriptions are overturned.

OTOH, with liquid hydrocarbon fuels, things like Steam Lorries and Steam Airplanes are possible -- and until the Proscriptions are overturned, practical.

(Search Youtube for "Steam Lorries" and "Steam Airplane" for examples and a history lesson or two.)

Diesel Hydraulic locomotives were very successful (Where the writ of General Motors did not run)
Unfortunately they did not get the development that the DE got.
Diesel Mechanical also works well at low powers and speeds.

chrisd wrote:
Diesel Hydraulic locomotives were very successful (Where the writ of General Motors did not run)
Unfortunately they did not get the development that the DE got.
Diesel Mechanical also works well at low powers and speeds.

In the US the development of the DE locomotive was underwritten by the US Navy, even if the engines and drive trains were to go in different directions. Modern DE locomotives do not carry significant batteries, Diesel Subs carry a lot of batteries. Locomotives use Air cooled engines, Subs are water cooled. I believe newer Locomotives use AC traction motors, Subs for obvious reasons had an all DC electrical system.