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Some extracts from Dieselair –

At same fractional power, the diesel is as efficient as at full power. So maintaining cruise speed may require down to 50% of the fuel flow needed with gasoline engines operating at same fractional power, meaning so much more range.

W W W . D I E S E L A I R . C O M -- The Diesel Air Newsletter -- Home

Very interesting references to what appears to be a recent resurgence in popularity of diesel aircraft! :naughty: The 4-seat Diamond DA42 Twin Star in particular in a pretty amazing (with the addition of only a 26 gallon (118 L) added fuel tank, and throttled back to 42% power, in 2004 one made the first nonstop Atlantic crossing by a diesel airplane!), as is the Centurion 2.0 L engine system, which can be retrofitted into such popular light singles as the Cessna 172. I hope Thielert’s current financial woes present only a brief obstacle to the use of this remarkable engine system.

 

That said, I’m uncertain that, outside of a niche like light aircraft, diesel pistonprop are anywhere near as good as turboprop in any area other than purchase and maintenance cost, factors that are significant in the light aircraft market, but not very in the air carrier market.

I would suggest Bio-diesel could be a replacement for Jet-A
An excellent suggestion, and one highly likely, I think, to be realized when a large, long-term increase in the cost of petrodiesel is clearly imminent or upon us.

 

The major challenge with replacing petrodiesel with biodiesel in aviation and other cold environment applications is its higher solidification (congealing) temperature. Unless a reliable technique of blending or cracking current biodiesel to overcome this issue is developed, a 90%+ biodiesel jet, turboprop, or diesel pistonprop all-season and commercial carrier altitude aircraft will need to have a fairly elaborate fuel heating and pre-shutdown flushing system. As these issues have been successfully addressed in other biodiesel, I don’t think this challenge presents a difficult barrier to biodiesel aviation. :D

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what about ram jet engines?

resistance is energy

the ram engine has no moving propellars to compress the air for combustion, insted it uses resistance to compress the air.

 

Ramjet - Wikipedia, the free encyclopedia

 

i imagine every forward facing surface of resistance being used for the ram engine

 

The main problem with Ram Jets is they have to be moving to work, you cannot take off with a ram jet only. Ram Jets are also difficult to throttle and can flame out easily, they also use more fuel than a good turbofan jet.

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what about ram jet engines?

resistance is energy

The main problem with Ram Jets is they have to be moving to work, you cannot take off with a ram jet only. Ram Jets are also difficult to throttle and can flame out easily, they also use more fuel than a good turbofan jet.
Another problem with ramjets (or scramjets) is not only must they be moving to work, they must be moving fast. Although it’s possible to run one at airspeeds as low as 100 MPH or so, they are very inefficient below about mach 0.5, and only approach or even exceed turbojet efficiency around mach 3.

 

Resistance does requires energy, and resistance varies about with the square of airspeed, so usually, higher speed aircraft takes more energy to carry the same load the same distance. So, as a general rule, improving energy the energy efficiency of an aircraft (or any vehicle where most of its drag is parasitic drag) requires lowering its speed. So, rather than motors that work better at higher speeds, motors that work better at lower speeds, such as turboprops, are needed.

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