For what it’s worth, SMA’s recommended operating technique is to go full throttle from takeoff until approach, irrespective of altitude. The engine has a TBO of 2400h a few years after introduction and is aiming for 3000h next. Austro just got 1800h on their beast and are going to get 180hp out of a 135hp Mercedes engine soon.
Who would be buying Lyco/Conti if we saw them for what they are: totally outdated low tech products from a long gone era.
I assumed Peter had inefficiency that comes with low loading in mind.
are going to get 180hp out of a 135hp Mercedes engine soon.
Certificate for the more powerful version was published something like a month ago.
The first Toyota hybrid was a turbine-electric, the tiny Sports 800 GT (GT for gas turbine). This was in 1977. A gas turbine can run at a comparably efficiency as a diesel engine, if it is allowed to run at best efficiency. The problem with a turbine is the efficiency decreases by a factor 10 or something if it runs on idle, it has a very narrow band of good efficiency, and this band is at high output power. This is also why it, in theory at least, will be good in a hybrid configuration in an aircraft. Just start it and let it run on max power (best efficiency) all the time, charging batteries when descending/taxiing, using the stored energy for take off.
This could also be done with a 350 HP diesel, but such a diesel weigh 5-10 times as much as a turbine, and is also 5-10 times more bulky.
Airbus Group today announced plans to build a factory in southwest France where it will manufacture the E-Fan 2.0, a two-seat electric airplane that is due to hit the market about two and a half years from now
Read more at http://www.flyingmag.com/news/airbus-build-electric-plane-factory-france#V5xbQxE2hQr7PRgB.99
Airbus seems to be desperate for “publicity projects” :)
A gas turbine can run at a comparably efficiency as a diesel engine, if it is allowed to run at best efficiency.
Sorry but this is complete nonsense.
Sorry but this is complete nonsense.
No, not complete. A normal turbine has a thermal efficiency of about 30-35% at best point, a diesel the same. An otto engine 25-30% max. The largest 2 stroke marine diesels has an efficiency close to 50%, while large marine gas turbines has about 40% (more than 50% when also using waste heat). The problems with turbines are not that they are particularly inefficient, rather they are inflexible. They have to run at one particular rpm at one particular torque to be efficient (constant power), and this is not very typical for anything that needs power, particularly not vehicles, boats or aircraft. Run it outside that narrow band, and the efficiency goes to the low 1 digits, so the overall efficiency becomes very low compared with a diesel for instance.
A gas turbine has always been considered the perfect match for a electric system in a hybrid configuration for a vehicle, but the overall cost of a gas turbine has proven hard to get down to diesel engine prices.
No, not complete. A normal turbine has a thermal efficiency of about 30-35% at best point, a diesel the same. An otto engine 25-30% max.
I don’t know where you get your numbers but they are far from reality. You don’t have to do more than google to realize that.
Aircraft turbines (bigger than for GA, i.e. more efficient) do around 27% at max output. The GA turbines are so old and primitive that they’re not a good comparison because one could do much better if there was any development. A simple Otto engine does 30-36% and a modern diesel engine does 40-47%. A 2-stroke marine diesel 55%.
They have to run at one particular rpm at one particular torque to be efficient (constant power)
No, they have to run at max design power.
A gas turbine has always been considered the perfect match for a electric system in a hybrid configuration for a vehicle, but the overall cost of a gas turbine has proven hard to get down to diesel engine prices.
No, it’s not. Absolutely not. Especially since the size works against efficiency in a turbine.
Well, a gas turbine achieves 40% efficiency without any extra cycles for waste heat (more than 60% with combined cycles). This is certainly comparable to a diesel or otto engine. But a gas turbine also drops off much faster when operating outside BEP. A diesel/otto engine on the other hand, has a large envelope in torque and rpm with good efficiency.
No, it’s not. Absolutely not. Especially since the size works against efficiency in a turbine.
Size always works against efficiency. This is no different for a turbine than for a diesel engine. The only difference, it is comparatively much more costly to create a small and efficient turbine than a small and efficient diesel engine, due to many reasons. The two main bad points for a gas turbine is low efficiency outside BEP and manufacturing cost. For an aircraft, those two points always exist when using a turbine. The manufacturing cost there is not much to do about, unless someone comes up with some fancy new materials and methods. But, in a hybrid setting, the poor efficiency can be fixed, and it can be fixed with lots of other benefits. This can also be done with an otto/diesel, but not with the same relative increase in overall efficiency, and not with the same benefits. A small super compact, highly efficient constant power two stroke diesel could probably do the trick, but such an engine does not exist either.
Airbus seems to be desperate for “publicity projects” :)
Maybe so, but they said the same about electric cars. Typically they said a car with 150 km range would not be useful for anything. I thought so too, but today my 120 km range eUp serves at least 95% of all my driving. For the rest I would actually be better off economically renting a car than owning one. In the last 5 months since I got my eUp I have filled the tank of my diesel BMW one single time. I have to drive it from time to time mostly to prevent the brakes rusting to much.
Those Airbuses, with a clever cartridge battery system or fast enough charging, could be excellent trainers for the right open minded persons. The trick is to view them as what they are and what they can do, not as what they are not and what they cannot do. Should be simple enough.
Well, a gas turbine achieves 40% efficiency without any extra cycles for waste heat
Aha, which aircraft gas turbine is that? The Trent XWB not so which one? The smaller aircraft turbines are all below 30% efficiency and apart from the lack in R&D, it’s an inherent problem because the fan to duct gap is relatively speaking larger the smaller the turbine.
It is technically not possible to produce a small turbine that comes close to a Diesel engine, even when assuming both run at 100% BHP all the time. Thermodynamics are in the way. Plenty of literature to read on this subject. Cost is certainly not the reason.
Aircraft turbines are optimised for best fuel consumption taking an aircraft from A to B. This involves taxing, clump, cruise, descent etc. They are not optimised exclusively to run at best possible efficiency in the “cruise” regime only, which is done for stationary power plants. With a hybrid technology it is possible to do exactly that. We will get a simpler turbine, with higher efficiency at lower cost.
Even the huge marine 2 strokes run exclusively at one rpm at one torque. Power regulation is done by “blanking off” individual pistons. I think the rpm varies between 100 and 106, maybe even less.
The exact same thermodynamic laws apply to diesel engines as it does to turbines.
