If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
|
#1
|
|||
|
|||
Diesel aircraft engines and are the light jets pushing out the twins?
In rec.aviation.owning R. David Steele /omega wrote:
What has happened to the development of the diesel aircraft engines? As far as I have seen, only Diamond has a production aircraft with diesel engines (they flew one across the Atlantic, with 5.76 gph). See http://www.avweb.com/ the column entitled Motor Head #2: Excerpts from the Oshkosh Notebook. And it looks like the small jets are pushing the turbo props and the twin piston engines. Is it a matter of time before it will be cheaper to just buy a small jet? I'm not holding my breath on that one. What puzzles me is why there doesn't appear to be anyone working on turbines in the range of 160 to 250 HP for aircraft. The upside to diesels is Jet-A is cheaper and more available just about everywhere outside the US. The downside is they tend to be heavier than the gas engines they would replace, reducing the usefull load. Turbines run on Jet-A and tend to be a lot lighter. Put a 180 HP turbine in a 172 and you would have a real 4 place A/C, though one with a long, funny looking nose to make the W/B work out. -- Jim Pennino Remove -spam-sux to reply. |
#2
|
|||
|
|||
I don't see the fuel burn on the small turbines competing with the diesels,
but there are some attempts at getting close to the Lycosaur level. Here is one - http://www.innodyn.com/ Don't know anything about them though. As for light jets pushing down demand for twin piston and turbo props, you are correct. You mentioned Diamond, and they are going straight after the light twin and turbine single engine market with their single engine jet. If you will accept a single engine, the economics seem to make sense to go that route rather than with an equally expensive Piper or Beech plane. It will be interesting to see what will happen. Some missions will likely push folks to stick with the prop planes though. |
#3
|
|||
|
|||
R.,
What has happened to the development of the diesel aircraft engines? As far as I have seen, only Diamond has a production aircraft with diesel engines (they flew one across the Atlantic, with 5.76 gph). In the European market, Diamond offers both the single-engine DA40 and the DA42 twin with Thielert Centurion engines. More than 100 of these engines are flying. in the US, only the DA42 is offered. Also, Thielert in Europe offers retrofit kits for Cessna 172s and Piper Warriors. Of those, 30 or so are flying. All other diesels I know of are not yet available in a certified kit, although by now the sma retrofit to the 182 might be available. -- Thomas Borchert (EDDH) |
#4
|
|||
|
|||
Thomas Borchert wrote in message ...
All other diesels I know of are not yet available in a certified kit, although by now the sma retrofit to the 182 might be available. There is at least one, I believe it is either a C172 or C182. I can not tell the difference, all planes with the wings on top are just cessnas to me. Anyway, it is used as a jump plane operating from Seppe(EHSE) with a SMA engine. Call sign PH-PAC. -Kees |
#6
|
|||
|
|||
A gas turbine scales up easily and but is nearly impossible to scale
down. The auto manuacturers found that out in the 1940s - remember the "car of the future" on the covers of Popular Science et al? Turbines for cars are further away now than they were 55 years ago. The turbine suffers from excessive fuel consumption at part throttle (the piston engine is incredibly flexible that way)and in smaller HP installations. So much of the useful load of an aircraft is fuel, that fuel efficiency is very important for overall mission performance. The problem of an engine is to find the most efficient way to expand a certain flow rate of compressed hot gas to atmospheric pressures. A turbine can do this with large mass flow rates, but as the flow rates become smaller, the turbine speeds (rpm) must increase enormously and the centrifugal accelerations get out of hand. On the other hand, a piston can process an expansion efficiently with small flow rates. Think of it this way - a model airplane engine can be made to run with 1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston engine aircraft became impractical above a few thousand HP. That is the range of practicality for a piston concept. An engineering prof once said - if the gas turbine had been invented first, the piston engine would have been looked on an ingeneous solution to the turbine's material and speed and power range problems. Diesels may eventually make it. They have a weight problem that may be offset by a lower specific fuel consumption, but for a given operating condition, spark ignition engines can nearly approach the consumption of diesels by using turbo compounding and operation only at full throttle. |
#7
|
|||
|
|||
In article ,
) wrote: Think of it this way - a model airplane engine can be made to run with 1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston engine aircraft became impractical above a few thousand HP. That is the range of practicality for a piston concept. It is certainly possible to build much larger piston engines than that. How about http://www.bath.ac.uk/~ccsshb/12cyl/ |
#8
|
|||
|
|||
Howdy!
In article , Roy Smith wrote: In article , ) wrote: Think of it this way - a model airplane engine can be made to run with 1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston engine aircraft became impractical above a few thousand HP. That is the range of practicality for a piston concept. It is certainly possible to build much larger piston engines than that. How about http://www.bath.ac.uk/~ccsshb/12cyl/ But it is a *little bit* impractical as an *aircraft* engine... yours, Michael -- Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly | White Wolf and the Phoenix Bowie, MD, USA | Tablet and Inkle bands, and other stuff | http://www.radix.net/~herveus/ |
#9
|
|||
|
|||
Roy Smith wrote:
It is certainly possible to build much larger piston engines than that. How about http://www.bath.ac.uk/~ccsshb/12cyl/ Ah! I've always wondered how that Antonov 225 Mrija was powered... Stefan |
#10
|
|||
|
|||
In rec.aviation.owning wrote:
A gas turbine scales up easily and but is nearly impossible to scale down. The auto manuacturers found that out in the 1940s - remember the "car of the future" on the covers of Popular Science et al? Turbines for cars are further away now than they were 55 years ago. The turbine suffers from excessive fuel consumption at part throttle (the piston engine is incredibly flexible that way)and in smaller HP installations. So much of the useful load of an aircraft is fuel, that fuel efficiency is very important for overall mission performance. The problem of an engine is to find the most efficient way to expand a certain flow rate of compressed hot gas to atmospheric pressures. A turbine can do this with large mass flow rates, but as the flow rates become smaller, the turbine speeds (rpm) must increase enormously and the centrifugal accelerations get out of hand. On the other hand, a piston can process an expansion efficiently with small flow rates. Think of it this way - a model airplane engine can be made to run with 1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston engine aircraft became impractical above a few thousand HP. That is the range of practicality for a piston concept. An engineering prof once said - if the gas turbine had been invented first, the piston engine would have been looked on an ingeneous solution to the turbine's material and speed and power range problems. Diesels may eventually make it. They have a weight problem that may be offset by a lower specific fuel consumption, but for a given operating condition, spark ignition engines can nearly approach the consumption of diesels by using turbo compounding and operation only at full throttle. While not quite a .049, here's a 3.7" in diameter, 2.6 lb turbine that produces 16.5 lb of thrust. http://jetcatusa.sitewavesonline.net/p70.html Their biggest turbine is 5.12", 5 lb, and produces 45 lb of thrust. Here's another outfit that sells a 3.5" diameter, 7.25" long, 1.9 lb turbine with 11.4 lb of thrust. http://www.swbturbines.com/model_turbines.htm Now granted these are turbojets, not turboprops, but it appears to me that making small turbines is possible... -- Jim Pennino Remove -spam-sux to reply. |
Thread Tools | |
Display Modes | |
|
|