6 ms·

Ok, but so what? Is there something bad about diesel engines?

by gregschlom 6y ago

deleted 6y ago
[deleted]
Stevvo 6y ago
Not at all, without question it's a superior fuel to leaded avgas.
- KMag 6y ago
  It has higher energy density, higher flash point (less prone to fire or explosion), less volatile (doesn't evaporate as quickly), and less toxic. However, it's difficult to make a diesel that gets as much power/weight or power/volume as a comparable petrol engine. There are trade-offs. It's not a universally superior fuel.
msandford 6y ago
Nothing is inherently bad but diesels tend to be heavier for the power they make. And there's a fairly well understood weight vs reliability tradeoff. Light an unreliable is bad for airplanes and so is heavy and reliable. You want light and reliable, ideally.
- baybal2 6y ago
  It is a V12. Historical military V12s had a feature of two bank redundancy. One row of 6 cylinders can be shut down along with its pumps, cooling, etc. And I have a big suspicion that they use two of these engines inside.
  - davidgould 6y ago
    V* engines share a common crankshaft with both banks, that's the V part. Please cite any specific V12 aircraft engine that can have one bank of cylinders shut down. I don't believe one exists.
    - baybal2 6y ago
      Of course the crankshaft is shared. It is oil, fuel, and cooling that can be shut down to prevent leaks.
    - ledauphin 6y ago
      I don't know much about aircraft engines, but in fact straight-6 engines are inherently balanced, and a V12 is fundamentally two straight sixes, so at least in theory it would be quite possible to stop using one bank of cylinders if some of their cylinders suffered some form of non-catastrophic failure.
    - akrain 6y ago
      Although I can't find a reference to an aircraft engine, Chrysler did have a variable displacement tech on its third gen Hemi engines that could turn off one bank of the V8. Ref: https://en.wikipedia.org/wiki/Multi-Displacement_System https://en.wikipedia.org/wiki/Multi-Displacement_System
    - desdiv 6y ago
      >Please cite any specific V12 aircraft engine that can have one bank of cylinders shut down. The RED A03 Engine[0], which is what this sub-thread is about. >Two cylinder-bank redundancy concept for high safety. >Robustness and safety are incorporated into the engine design. The two 6-cylinder banks are capable of independent operation. All critical engine sub-systems are mutually-independent. [0] https://red-aircraft.com/ https://red-aircraft.com/
      - londons_explore 6y ago
        Except the crankshaft... Oh, and any mechanical issues with pistons or valves in one side will jam the crankshaft, therefore stop the other half working... And that crankshaft needs some kind of oil... And a pump to pressurize that oil. And if a leak forms anywhere the oil drains out and the crankshaft seizes. Pretty hard to lube one crankshaft with two redundant and isolated oil systems... Overall, I'd call the engine 1.5x redundancy...
- owenversteeg 6y ago
  This is far lighter and significantly different from your usual diesel, though. It's an all-aluminum design and weighs 250-300kg. Heavier (for the same power) than competing turbine engines (like, say, the ubiquitous PT6?) Sure, absolutely. Crazy heavy? Nah. The entire thing probably weighs somewhere around 2000-3000kg (veeery roughly) if I had to guess. So the extra 100kg or so isn't a total dealbreaker, if they can make it up elsewhere. Very interesting aircraft for sure. I'm still skeptical, but hoping it works out, and rooting for them! Some discussion on its claims to fly at 65,000 feet here: https://www.beechtalk.com/forums/viewtopic.php?f=49&t=174467&start=30 https://www.beechtalk.com/forums/viewtopic.php?f=49&t=174467...
Gibbon1 6y ago
They weigh more but have lower fuel consumption. More complex than gasoline aero engines. Usually more reliable but making them light probably impacts that. I think the lower fuel consumption compensates for the higher weight for longer flights. Big reason for switching to them after 100 years of using gasoline is aviation gas is expensive and concerns about lead. Big picture I think refineries and distributors don't want to supply aviation gasoline anymore.
Neil44 6y ago
BSFC as in horsepower generated per unit of fuel tends to be better in Diesel engines, but they’re heavier because the combustion events are more violent, requiring a stronger block and pistons.

Ok, but so what? Is there something bad about diesel engines?

deleted 6y ago

[deleted]

Stevvo 6y ago

Not at all, without question it's a superior fuel to leaded avgas.

KMag 6y ago
It has higher energy density, higher flash point (less prone to fire or explosion), less volatile (doesn't evaporate as quickly), and less toxic. However, it's difficult to make a diesel that gets as much power/weight or power/volume as a comparable petrol engine. There are trade-offs. It's not a universally superior fuel.

msandford 6y ago

Nothing is inherently bad but diesels tend to be heavier for the power they make. And there's a fairly well understood weight vs reliability tradeoff. Light an unreliable is bad for airplanes and so is heavy and reliable. You want light and reliable, ideally.

baybal2 6y ago
It is a V12. Historical military V12s had a feature of two bank redundancy. One row of 6 cylinders can be shut down along with its pumps, cooling, etc. And I have a big suspicion that they use two of these engines inside.
- davidgould 6y ago
  V* engines share a common crankshaft with both banks, that's the V part. Please cite any specific V12 aircraft engine that can have one bank of cylinders shut down. I don't believe one exists.
  - baybal2 6y ago
    Of course the crankshaft is shared. It is oil, fuel, and cooling that can be shut down to prevent leaks.
  - ledauphin 6y ago
    I don't know much about aircraft engines, but in fact straight-6 engines are inherently balanced, and a V12 is fundamentally two straight sixes, so at least in theory it would be quite possible to stop using one bank of cylinders if some of their cylinders suffered some form of non-catastrophic failure.
  - akrain 6y ago
    Although I can't find a reference to an aircraft engine, Chrysler did have a variable displacement tech on its third gen Hemi engines that could turn off one bank of the V8. Ref: https://en.wikipedia.org/wiki/Multi-Displacement_System https://en.wikipedia.org/wiki/Multi-Displacement_System
  - desdiv 6y ago
    >Please cite any specific V12 aircraft engine that can have one bank of cylinders shut down. The RED A03 Engine[0], which is what this sub-thread is about. >Two cylinder-bank redundancy concept for high safety. >Robustness and safety are incorporated into the engine design. The two 6-cylinder banks are capable of independent operation. All critical engine sub-systems are mutually-independent. [0] https://red-aircraft.com/ https://red-aircraft.com/
    - londons_explore 6y ago
      Except the crankshaft... Oh, and any mechanical issues with pistons or valves in one side will jam the crankshaft, therefore stop the other half working... And that crankshaft needs some kind of oil... And a pump to pressurize that oil. And if a leak forms anywhere the oil drains out and the crankshaft seizes. Pretty hard to lube one crankshaft with two redundant and isolated oil systems... Overall, I'd call the engine 1.5x redundancy...
owenversteeg 6y ago
This is far lighter and significantly different from your usual diesel, though. It's an all-aluminum design and weighs 250-300kg. Heavier (for the same power) than competing turbine engines (like, say, the ubiquitous PT6?) Sure, absolutely. Crazy heavy? Nah. The entire thing probably weighs somewhere around 2000-3000kg (veeery roughly) if I had to guess. So the extra 100kg or so isn't a total dealbreaker, if they can make it up elsewhere. Very interesting aircraft for sure. I'm still skeptical, but hoping it works out, and rooting for them! Some discussion on its claims to fly at 65,000 feet here: https://www.beechtalk.com/forums/viewtopic.php?f=49&t=174467&start=30 https://www.beechtalk.com/forums/viewtopic.php?f=49&t=174467...

Gibbon1 6y ago

They weigh more but have lower fuel consumption. More complex than gasoline aero engines. Usually more reliable but making them light probably impacts that. I think the lower fuel consumption compensates for the higher weight for longer flights. Big reason for switching to them after 100 years of using gasoline is aviation gas is expensive and concerns about lead. Big picture I think refineries and distributors don't want to supply aviation gasoline anymore.

Neil44 6y ago

BSFC as in horsepower generated per unit of fuel tends to be better in Diesel engines, but they’re heavier because the combustion events are more violent, requiring a stronger block and pistons.