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SEPilot
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Engine efficiency-what are the limits?

Mon Nov 18, 2019 9:20 am

Modern jet engines have become almost unbelievably reliable-who would have thought thirty years ago that twin engine airliners would routinely be flying ETOPS flights of 340 minutes? But has the quest for more and more efficiency started to encroach on that reliability? Anything pushed to its limits will tend to be less reliable, and one of the primary ways to increase efficiency is to push limits, be they temperature, pressure, or speed limits. A couple of the latest engines seem to have been fairly trouble free, the GenX and the TrentXWB. But others, like the Trent1000 and the GTF are having significant problems as they start building hours and cycles. I look back at piston engine history; while they never were anywhere nearly as reliable as jet engines were from the outset, the latest turbo-compound models were absolute maintenance and reliability nightmares. Are we trying to push jet engine technology too far? What are the practical limits? Everyone on this forum seems to accept the idea that there will be continual efficiency improvements, with a new, more efficient generation appearing every five to ten years. But that is not realistic. Automotive engines have improved greatly over the years, but thermodynamic efficiency has improved very little if at all in recent years.
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Re: Engine efficiency-what are the limits?

Mon Nov 18, 2019 1:23 pm

I've mentioned before that carbon off-sets are often good economics. A few billion from off-sets in jet engines might make those engines cheaper and more reliable, and put several hundred thousand electric cars on roads twenty years earlier. Atmosphere doesn't care where the carbon comes from, then more flying will mean less CO2.

$3 billion would provide $7500 incentives for 400K cars
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MIflyer12
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Re: Engine efficiency-what are the limits?

Mon Nov 18, 2019 1:41 pm

SEPilot wrote:
Automotive engines have improved greatly over the years, but thermodynamic efficiency has improved very little if at all in recent years.


That isn't true in automotive. There are more high efficiency engines, by more manufacturers, achieving higher peak efficiency. Of course electrification of autos is where the big money is going, be it plug-in hybrids or Battery Electric Vehicles (with Tesla being the exemplar). Several manufacturers have actually called the end of development of their internal combustion engines.

Poster #2 makes a good point. If the air passenger industry were to be challenged to go completely carbon-neutral by, say, 2050, offsets and geo-engineering would be the cheaper way to do it, not solar-powered electric planes.

The 'can't get any better' trope gets rolled out by people who don't know the history of engineering innovation or economic history. It's an argument with an analog to the whack-jobs arguing zero population growth. Malthus was wrong in ~1800, and he's wrong today.
 
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lightsaber
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Re: Engine efficiency-what are the limits?

Mon Nov 18, 2019 7:39 pm

MIflyer12 wrote:
SEPilot wrote:
Automotive engines have improved greatly over the years, but thermodynamic efficiency has improved very little if at all in recent years.


That isn't true in automotive. There are more high efficiency engines, by more manufacturers, achieving higher peak efficiency. Of course electrification of autos is where the big money is going, be it plug-in hybrids or Battery Electric Vehicles (with Tesla being the exemplar). Several manufacturers have actually called the end of development of their internal combustion engines.

Poster #2 makes a good point. If the air passenger industry were to be challenged to go completely carbon-neutral by, say, 2050, offsets and geo-engineering would be the cheaper way to do it, not solar-powered electric planes.

The 'can't get any better' trope gets rolled out by people who don't know the history of engineering innovation or economic history. It's an argument with an analog to the whack-jobs arguing zero population growth. Malthus was wrong in ~1800, and he's wrong today.

The problem was not enough technology development due to low oil prices. When peak oil mania hit, the price skyrocketed and technology was rushed.

New tech:
3.5:1 gearbox, a few percent reduction in fuel burn
CMCs turbine inlet vanes (fixed), about 3% drop in fuel burn. In GE9x
2nd row high turbine, 2.5% or so. Not yet ready.
1st row of high turbine 3.5% A decade out or so
Issue is poor CMC yield and the fact higher density CMCs are needed for rotating blades.

Higher mach # compressor, 2%
Better system design, in particular matching low to high compressor profiles 1%

Variable cycle technology:
Variable turbine cooling, in LEAP engines, about 3%
Variable fan nozzle, 2%, but only in cruise (no benefit earlier in mission).
Variable fan pitch (about 2.5% in cruise, about 2% in climb)

Technology isn't done. We just forgot lessons learned.

Lightsaber
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Re: Engine efficiency-what are the limits?

Mon Nov 18, 2019 11:51 pm

lightsaber wrote:
MIflyer12 wrote:
SEPilot wrote:
Automotive engines have improved greatly over the years, but thermodynamic efficiency has improved very little if at all in recent years.


That isn't true in automotive. There are more high efficiency engines, by more manufacturers, achieving higher peak efficiency. Of course electrification of autos is where the big money is going, be it plug-in hybrids or Battery Electric Vehicles (with Tesla being the exemplar). Several manufacturers have actually called the end of development of their internal combustion engines.

Poster #2 makes a good point. If the air passenger industry were to be challenged to go completely carbon-neutral by, say, 2050, offsets and geo-engineering would be the cheaper way to do it, not solar-powered electric planes.

The 'can't get any better' trope gets rolled out by people who don't know the history of engineering innovation or economic history. It's an argument with an analog to the whack-jobs arguing zero population growth. Malthus was wrong in ~1800, and he's wrong today.

The problem was not enough technology development due to low oil prices. When peak oil mania hit, the price skyrocketed and technology was rushed.

New tech:
3.5:1 gearbox, a few percent reduction in fuel burn
CMCs turbine inlet vanes (fixed), about 3% drop in fuel burn. In GE9x
2nd row high turbine, 2.5% or so. Not yet ready.
1st row of high turbine 3.5% A decade out or so
Issue is poor CMC yield and the fact higher density CMCs are needed for rotating blades.

Higher mach # compressor, 2%
Better system design, in particular matching low to high compressor profiles 1%

Variable cycle technology:
Variable turbine cooling, in LEAP engines, about 3%
Variable fan nozzle, 2%, but only in cruise (no benefit earlier in mission).
Variable fan pitch (about 2.5% in cruise, about 2% in climb)

Technology isn't done. We just forgot lessons learned.

Lightsaber

So what you are saying is that there is probably about a 20% gain available from improvements that are known but not yet implemented for various reasons? What time frame would you estimate it would take to implement them all? My guess would be about 40 years. And since none of the ones you mention involve increased temperatures except perhaps the CMC turbine blades I don’t see a great risk of decreased reliability, do you? I am pleased with your input, I was hoping you would respond. You present a much more optimistic picture than I had.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
FLALEFTY
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 12:14 am

Variable cycle technology:
Variable turbine cooling, in LEAP engines, about 3%
Variable fan nozzle, 2%, but only in cruise (no benefit earlier in mission).
Variable fan pitch (about 2.5% in cruise, about 2% in climb)

Technology isn't done. We just forgot lessons learned.

Lightsaber


The variable fan pitch estimates, do they include allowing for the weight reduction from eliminating thrust reversers? This is supposed to be a feature of RR's Super Fan design.
 
Waterbomber2
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 1:32 am

I'm trying to make my own observations, I'm running a reforestation/carbon capture experiment in an area in Mediterranean Italy that has very arid, almost Sahelic charachteristics despite not being far from the sea. For this location, I'm studying weather patterns using websites like wetteronline.de, and quite honestly I can't come to a clear conclusion. 3 summers ago we hit 50°C almost daily with no rain for 5 months, 2 summers ago it rained the whole summer as a cycle of rain > high humidity > rain was sustained throughout the summer. Last summer it didn't rain for 4 months, but temperatures were rarely above 40°C, and now it's been raining heavily for 2 weeks like I have never seen it rain before. Quite frankly, it's so random that it's impossible to define a clear pattern. Also while this area used to be very dry and blunt with little vegetation, it is now becoming greener and greener by itself despite that it should be going the other way if we may believe the global warming theories.
I have also been observing the beach near this location and quite frankly, if there is a rise of the mean sea level, it is not really perceptible.

However, I have been taught through school that global warming is a real thing, NASA scientists are also saying this and they can't all be liberal democrats.
In addition, while I also believe the theory that higher atmospheric CO2 will be beneficial to plant growth, I also believe that something's got to give for pummping up 80 millions of barrels of oil per day, which is the equivalent capacity of 5000 olympic pools. I don't know if you can picture how much oil that is. While not all of it is used for combustion, a significant portion is.
Also, I think that if we let people have their way, the whole world is going to become a landfill in no time.

So overall, I think that continuing on the premise that global warming is real is not a bad thing.
If it isn't, we still progress by developping new technologies, that could help increase the survivability of humanity on the hyper long term, especially in the face of critical events or expansion towards other planets.

So while semi-skeptic, I'm also active in compensating my own carbon footprint.
My message to Greta and friends is that while their passion for their cause is great, if they really believe in it, they should study hard, earn money, buy land and plant trees on them. Many countries like Italy even subsidise reforestation projects. So I think that it's not reasonable to travel around the world with an angry face, expecting other people to do something about it while they are doing nothing about it themselves.

So back to the engines, I think that the current turbine engine architecture does have its limitations and that we will see new architectures see the light in the coming years, enabling much higher fuel efficiency.
One of the goals is to reach stoichiometric fuel burn, for which you need a combustion temperature of above 2000°C, resulting in very high TIT, which is still the challenge in terms of materials.
I think that we will reach the stoichiometric fuel burn within the next decade though.
There are also other potential area's of improvement to the turbine engines in terms of aerodynamics.

So no, we haven't hit the limitations, but improving turbines has been about finding a balance between efficiency and reliability from its early days on the Me262, and when you try to jump the progress curve, you are trading efficiency for reliability..
 
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hongkongflyer
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 1:54 am

I think we have reached the current technology limits. See what happened to the new generation planes' engine on 320Neo; 787 and 777X.....
 
Canuck600
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 3:05 am

Where is the lack of reliability in the new engines coming from? Lack of quality in the new materials used or is it the overall manufacturing process no mature enough to lead to increased reliability?
 
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lightsaber
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 3:24 am

SEPilot wrote:
lightsaber wrote:
MIflyer12 wrote:

That isn't true in automotive. There are more high efficiency engines, by more manufacturers, achieving higher peak efficiency. Of course electrification of autos is where the big money is going, be it plug-in hybrids or Battery Electric Vehicles (with Tesla being the exemplar). Several manufacturers have actually called the end of development of their internal combustion engines.

Poster #2 makes a good point. If the air passenger industry were to be challenged to go completely carbon-neutral by, say, 2050, offsets and geo-engineering would be the cheaper way to do it, not solar-powered electric planes.

The 'can't get any better' trope gets rolled out by people who don't know the history of engineering innovation or economic history. It's an argument with an analog to the whack-jobs arguing zero population growth. Malthus was wrong in ~1800, and he's wrong today.

The problem was not enough technology development due to low oil prices. When peak oil mania hit, the price skyrocketed and technology was rushed.

New tech:
3.5:1 gearbox, a few percent reduction in fuel burn
CMCs turbine inlet vanes (fixed), about 3% drop in fuel burn. In GE9x
2nd row high turbine, 2.5% or so. Not yet ready.
1st row of high turbine 3.5% A decade out or so
Issue is poor CMC yield and the fact higher density CMCs are needed for rotating blades.

Higher mach # compressor, 2%
Better system design, in particular matching low to high compressor profiles 1%

Variable cycle technology:
Variable turbine cooling, in LEAP engines, about 3%
Variable fan nozzle, 2%, but only in cruise (no benefit earlier in mission).
Variable fan pitch (about 2.5% in cruise, about 2% in climb)

Technology isn't done. We just forgot lessons learned.

Lightsaber

So what you are saying is that there is probably about a 20% gain available from improvements that are known but not yet implemented for various reasons? What time frame would you estimate it would take to implement them all? My guess would be about 40 years. And since none of the ones you mention involve increased temperatures except perhaps the CMC turbine blades I don’t see a great risk of decreased reliability, do you? I am pleased with your input, I was hoping you would respond. You present a much more optimistic picture than I had.

Engine efficiency and aircraft efficiency combined are improving about 1.25% per year.

Material changes are the big breakthrough and CMCs are the obvious change. I see new technology being proposed and some taking a long time to perfect. Test engines were equiped with CMC blades in 1996 and the first aircraft to fly will be the 779.

There will also be minor improvements retrofitted. For example, compressor blades should be more shaped.

We had issues with the latest engines, but their reliability is improving dramatically. The GE9x is as amazing jump in technology. As much over the GEnX as it was GEnX over the CF6 (latest and greatest versions).

I cannot predict every innovation. I can read old Whittle patents and see ideas still not implimented. :spin:

Unfortunately the T1000 and PW1100G issues will make the next engines more conservative.

Lightsaber
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 4:49 am

I believe that you forgot that changing turbine size also effects efficiency. Hence, the recent larger (and heavier) turbines.

However, for metal blades and reasonable sizes and weights I believe that we are nearing the end of what can be done. Yes, Light-saber indicates that "in theory" there might be another 10-12% with many various improvements with metal blades; and about another 9% by changing to ceramic blades.

My personal take on real world engineering is that I would expect Light-Saber's 10-12% to be half of that within practical engineering and production.

So I think that with metal blades that we are within about 6% of what is realistically achievable due to temperature limits; and that it will likely take another decade to get half of that with any real reliability.

I see that Ceramic Blades add far more than the possible 9% that Light-Saber indicates; because, I believe that going to all ceramic blades will allow another major geometry change that will ad at least another 4-5% and possible even double that. I speculate 18% achievable with a geometry change and ceramic blades The cool thing is that all of those other geometry things that likely add another 6% to the metal blade engines - are also likely to occur. Thus, I think you could yet see about another 25% reduction in fuel usage. That may be 20-30 years out though.

After that; perhaps we will have mastered fusion reactors and be generating anti-matter and we can come up with antimatter reaction engines and totally change how aircraft and ship propulsion is done.

Have a great day,
 
1989worstyear
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 5:19 am

lightsaber wrote:
SEPilot wrote:
lightsaber wrote:
The problem was not enough technology development due to low oil prices. When peak oil mania hit, the price skyrocketed and technology was rushed.

New tech:
3.5:1 gearbox, a few percent reduction in fuel burn
CMCs turbine inlet vanes (fixed), about 3% drop in fuel burn. In GE9x
2nd row high turbine, 2.5% or so. Not yet ready.
1st row of high turbine 3.5% A decade out or so
Issue is poor CMC yield and the fact higher density CMCs are needed for rotating blades.

Higher mach # compressor, 2%
Better system design, in particular matching low to high compressor profiles 1%

Variable cycle technology:
Variable turbine cooling, in LEAP engines, about 3%
Variable fan nozzle, 2%, but only in cruise (no benefit earlier in mission).
Variable fan pitch (about 2.5% in cruise, about 2% in climb)

Technology isn't done. We just forgot lessons learned.

Lightsaber

So what you are saying is that there is probably about a 20% gain available from improvements that are known but not yet implemented for various reasons? What time frame would you estimate it would take to implement them all? My guess would be about 40 years. And since none of the ones you mention involve increased temperatures except perhaps the CMC turbine blades I don’t see a great risk of decreased reliability, do you? I am pleased with your input, I was hoping you would respond. You present a much more optimistic picture than I had.

Engine efficiency and aircraft efficiency combined are improving about 1.25% per year.

Material changes are the big breakthrough and CMCs are the obvious change. I see new technology being proposed and some taking a long time to perfect. Test engines were equiped with CMC blades in 1996 and the first aircraft to fly will be the 779.

There will also be minor improvements retrofitted. For example, compressor blades should be more shaped.

We had issues with the latest engines, but their reliability is improving dramatically. The GE9x is as amazing jump in technology. As much over the GEnX as it was GEnX over the CF6 (latest and greatest versions).

I cannot predict every innovation. I can read old Whittle patents and see ideas still not implimented. :spin:

Unfortunately the T1000 and PW1100G issues will make the next engines more conservative.

Lightsaber


Per each year? But it was 0% from 1989 (V2500) to 2014 (NEO) for NB's, and still 0% for the A320-200 airframe.

Are you referring to tech that has not been introduced?
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...
 
luv2cattlecall
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 5:52 am

1989worstyear wrote:
lightsaber wrote:
SEPilot wrote:
So what you are saying is that there is probably about a 20% gain available from improvements that are known but not yet implemented for various reasons? What time frame would you estimate it would take to implement them all? My guess would be about 40 years. And since none of the ones you mention involve increased temperatures except perhaps the CMC turbine blades I don’t see a great risk of decreased reliability, do you? I am pleased with your input, I was hoping you would respond. You present a much more optimistic picture than I had.

Engine efficiency and aircraft efficiency combined are improving about 1.25% per year.

Material changes are the big breakthrough and CMCs are the obvious change. I see new technology being proposed and some taking a long time to perfect. Test engines were equiped with CMC blades in 1996 and the first aircraft to fly will be the 779.

There will also be minor improvements retrofitted. For example, compressor blades should be more shaped.

We had issues with the latest engines, but their reliability is improving dramatically. The GE9x is as amazing jump in technology. As much over the GEnX as it was GEnX over the CF6 (latest and greatest versions).

I cannot predict every innovation. I can read old Whittle patents and see ideas still not implimented. :spin:

Unfortunately the T1000 and PW1100G issues will make the next engines more conservative.

Lightsaber


Per each year? But it was 0% from 1989 (V2500) to 2014 (NEO) for NB's, and still 0% for the A320-200 airframe.

Are you referring to tech that has not been introduced?


Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?
 
1989worstyear
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 6:00 am

luv2cattlecall wrote:
1989worstyear wrote:
lightsaber wrote:
Engine efficiency and aircraft efficiency combined are improving about 1.25% per year.

Material changes are the big breakthrough and CMCs are the obvious change. I see new technology being proposed and some taking a long time to perfect. Test engines were equiped with CMC blades in 1996 and the first aircraft to fly will be the 779.

There will also be minor improvements retrofitted. For example, compressor blades should be more shaped.

We had issues with the latest engines, but their reliability is improving dramatically. The GE9x is as amazing jump in technology. As much over the GEnX as it was GEnX over the CF6 (latest and greatest versions).

I cannot predict every innovation. I can read old Whittle patents and see ideas still not implimented. :spin:

Unfortunately the T1000 and PW1100G issues will make the next engines more conservative.

Lightsaber


Per each year? But it was 0% from 1989 (V2500) to 2014 (NEO) for NB's, and still 0% for the A320-200 airframe.

Are you referring to tech that has not been introduced?


Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?


Yes, for the CEO.
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...
 
ltbewr
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 11:41 am

There may be limits on how much further internal combustion jet aircraft engines can become more efficient, that is just the reality of thermodynamic physics. We seen how trying to fit a larger, more efficient engine on the 737MAX led to unintended consequences.

You are still burning dirty, carbon loaded fuel. Reductions in sulfur in jet fuel while good for the enviroment, means more wear on key parts as the sulfur was a kind of lubricant. We have to engineer improved lubrication of bearings or of the lubricants themselves, improve temperature tolerances of seals used to offset the higher temperatures in combustion chambers. Adding more stuff to make engines more efficient means more complexity and greater chances of some failure or dirtier exhaust. We have seen that with piston engines and modern car engines. Yes, there may be incremental improvements in the future, but major redesigns are costly and may lead to their own issues. Better might be to find ways to reduce weight of aircraft themselves with carbon fiber and other materials in their structures and component parts as well as improve wing designs but taking care not to create problem there either..
 
frmrCapCadet
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 2:57 pm

I deliberately in my response made no mention of climate change. There was and is no need to inflame persons who have chosen to reject evolution, vaccines, climate change, flat earth etc. Policies and science build upon certain assumptions, technology is based on those assumptions. The people of Venice do not have to discuss the basic science, but they damn well better figure out how to cope with higher water - and they are working at it.
Buffet: the airline business...has eaten up capital...like..no other (business)
 
lowbank
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 5:42 pm

Well my twopence worth.
It is now recognised that to do a 1% PIP is now is going to cost you 5x what it did 5-10 years ago.

Finding ideas to make changes that give even small gains are hard to find.

The last PIP I working on , my component redesign was estimated to give 0.03 to 0.05% gain in SFC.

Some of the numbers I see discussed on here about certain PIP’s I worked on in the past were far greater than were being aimed for and in the main not achieved.
Every days a school day.
 
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OA412
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 5:56 pm

As this was posted in civil aviation, please keep religion and politics out of the discussion. Both of those topics belong in non aviation. Thank you!
Hughes Airwest - Top Banana In The West
 
LTCM
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 6:31 pm

The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.
 
frmrCapCadet
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 6:55 pm

LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


The answer to this was in a previous post.
It is now recognised that to do a 1% PIP is now is going to cost you 5x what it did 5-10 years ago


The curve implicit in that post now dominates the curve implicit in LTCM's post
Buffet: the airline business...has eaten up capital...like..no other (business)
 
luv2cattlecall
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 7:07 pm

1989worstyear wrote:
luv2cattlecall wrote:
1989worstyear wrote:

Per each year? But it was 0% from 1989 (V2500) to 2014 (NEO) for NB's, and still 0% for the A320-200 airframe.

Are you referring to tech that has not been introduced?


Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?


Yes, for the CEO.


Haven't there been continual improvements such as SETWA, sharklets, lighter galley and seat hardware, engine PIPs, trim system software tweaks, and so on?
 
Chemist
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 7:08 pm

LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


Well said. I was just going to post something similar.
The fact is that current jet fuel has a certain amount of energy releaseable in combustion. We can get ever close to harnessing that energy 100%, but you aren't going to get more than that. Unless you change to some new fuel. So you can't assume that we can forever keep getting more energy out of the same fuel.
It would be interesting to know how much actual headroom we have on theoretical maximum fuel output versus where we are today. I have no idea whether we are using 20%, 50%, or 90% of the fuel's theoretical maximum energy in today's commercial aircraft.
 
1989worstyear
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 7:34 pm

luv2cattlecall wrote:
1989worstyear wrote:
luv2cattlecall wrote:

Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?


Yes, for the CEO.


Haven't there been continual improvements such as SETWA, sharklets, lighter galley and seat hardware, engine PIPs, trim system software tweaks, and so on?


Those can be retrofitted onto an older frame to bring it up to 2019 specifications, and it only is a single-digit % efficiency gain over three decades.
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...
 
BooDog
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:01 pm

I work in the wind turbine industry. I know how the economic cycle works with wind, and I'm assuming that the economics for jet engines is the same. You figure out the total costs. Initial purchase price of the jet engine + cost of fuel consumed + cost of planned maintenance + cost of replacement parts that won't last the life of the engine. If the cost of fuel saved is less than the increased cost of the part, you don't do it. But... you can count on certain cost savings as technology progresses.
For example, the cost of an exotically shaped compressor blade in 2019 might be too expensive, but that cost will come way down by 2029, and manufacturers are counting on that cost reduction for future efficiency gains. With wind turbines, the cost of CFRP turbine blades was way too high in 2009, but we knew that cost would start dropping as time went by, and we could count on that future efficiency gain. And what happened in those ten years? Still no CFRP. Other technological gains in glass fiber reinforced polyester and glass fiber reinforced epoxy means that it's now the best direction to go with wind turbine blades, and not CFRP.
Progress ALWAYS happens. Many more gains in efficiency and reliability in the future with jet engines.
B1B - best looking aircraft ever.
 
2175301
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:25 pm

LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


That is not even close to the truth:

The 1st law of Thermodynamics: You cannot win. You cannot get more energy out than there is to start with.

The 2st law of Thermodynamics: You cannot even break even. As it applies to heat engines (gas turbines, boilers, internal combustion engines, etc) you are first limited by what is named the Carnot thermal efficiency equation: 1- (Tcold/Thot) Tcold is the temperature to which you are rejecting waste heat. Thot is the fluid temperature entering the process section of the heat engine (which is for a gas turbine is often less than the combustion temperature). The temperatures are in Degrees Kelvin (or Rankine for the users of the English/German system).

Thus if you assume that a modern gas turbine engine has hot gas entering the expansion section of the turbine of 1645 K (1372 C), and you are rejecting to atmospheric air at 273 K (0 C) then your best theoretical efficiency is: 1-(273/1645) = 83% (if I did the math right).

Now the turbine has a further reduction in efficiency based on the pressure ratios of the combustion chamber to the outside air pressure (the equation is a bit more complex as it also involves specific heat of the fuel and air) - but it produces a somewhat similar further reduction in possible efficiency.

My knowledge in power industry applications is that a stand alone combustion turbine rarely exceeds 45% thermal efficiency. Pair it with a back end steam cycle and you can achieve 60% in ideal situations (which is why "Combined cycle" power plants are being built - despite the high cost of the fuel).

Perhaps one of the Aircraft Turbine experts here could show us some typical actual calculations of combined Carnot and Brayton cycle efficiencies so we would know.

The 3rd law of Thermodynamics: You cannot even get out of the game... and we will leave that discussion for tech ops if someone wishes to discuss thermodynamics on that level.

Have a great day,
 
mjoelnir
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:35 pm

1989worstyear wrote:
luv2cattlecall wrote:
1989worstyear wrote:

Per each year? But it was 0% from 1989 (V2500) to 2014 (NEO) for NB's, and still 0% for the A320-200 airframe.

Are you referring to tech that has not been introduced?


Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?


Yes, for the CEO.


One gets tired of summing up what Airbus has done to the A320 since the first -200.
 
Kilopond
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:44 pm

An awful lot of the chemical energy contained in the fuel gets converted into thermal energy which is permanently °lost“. In the sense that it just gets blown into the atmosphere without any positive effect. Technics are needed that would convert that wasted thermal energy into something useful.
 
Kilopond
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:44 pm

An awful lot of the chemical energy contained in the fuel gets converted into thermal energy which is permanently °lost“. In the sense that it just gets blown into the atmosphere without any positive effect. Technics are needed that would convert that wasted thermal energy into something useful.
 
1989worstyear
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 8:53 pm

mjoelnir wrote:
1989worstyear wrote:
luv2cattlecall wrote:

Are you saying that the first A320-200 built and the newest one both have the same fuel efficiency?


Yes, for the CEO.


One gets tired of summing up what Airbus has done to the A320 since the first -200.


They've made some updates, but they're no different from any other 25+ year old type like the 763 or A333.

EDIT: and for the record, buyer-furnished equipment like galleys or seats should not apply here, as OEM's do not incorporate it into their baseline weights for a type (typically).
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...
 
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zeke
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 9:40 pm

The current limits i think are to do with the moving parts and the engine cycle used.


The ultimate jet engine would have no moving parts, and would not burn fuel in the engine.

Experiments with high voltage electric charge of air has started as a propulsive force to sustain flight.

While in the very early days, if we see the leaps and bounds with that technology over the next 60 years like we have seen with gas turbines over the past 60 years, it will me a much more sustainable future.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
Swadian
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 10:12 pm

In recent diesel engines, there's little or no correlation between fuel efficiency and emissions. The latest Tier 4 engines emit less than Tier 3 engines, but at a noticeable increase in fuel consumption. Why? Because their Exhaust Gas Recirculation reduces NOx at the expense of increased fuel and particulates, and their Diesel Particulate Filters get blocked at low RPM. So, the only advantage of using a Tier 4 engine is if one has a lot of money to spend and wants to virtue-signal about the environment.

Does this apply to jet engines? Probably not, but it's worth pointing out that "better for the environment" isn't the same as "better for the wallet".
 
planewasted
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 10:35 pm

hongkongflyer wrote:
I think we have reached the current technology limits. See what happened to the new generation planes' engine on 320Neo; 787 and 777X.....

I remember when I was a kid and SAS crashed an MD80 due to ice ingestion. Some SAS pilots complained about that the MD80 had too advanced and sensitive engines compared to the DC-9.
 
Waterbomber2
Posts: 544
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 10:41 pm

2175301 wrote:
LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


That is not even close to the truth:

The 2st law of Thermodynamics: You cannot even break even. As it applies to heat engines (gas turbines, boilers, internal combustion engines, etc) you are first limited by what is named the Carnot thermal efficiency equation: 1- (Tcold/Thot) Tcold is the temperature to which you are rejecting waste heat. Thot is the fluid temperature entering the process section of the heat engine (which is for a gas turbine is often less than the combustion temperature). The temperatures are in Degrees Kelvin (or Rankine for the users of the English/German system).

Thus if you assume that a modern gas turbine engine has hot gas entering the expansion section of the turbine of 1645 K (1372 C), and you are rejecting to atmospheric air at 273 K (0 C) then your best theoretical efficiency is: 1-(273/1645) = 83% (if I did the math right).



The temperature of the hot gas entering the turbine section vs. ambient air is irrelevant in calculating the theoretical thermodynamic efficiency of your engine.
What you would want to calculate is 1 - (Texhaust/Tturbine inlet) replacing the ambient air temperature with your exhaust gas temperature.
So it's actually much worse than that as engine exhaust is never as low as 273K.
 
mjoelnir
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 10:50 pm

I think efficiency increase could come by separating fan and core for example, hybrid engines and so on.


for example, without thinking about storing energy
An engine with a very small core for example, the fan driven mechanically from the core and with an incorporated elektro motor driven by an APU at take off and climb. The core completely optimized for cruise.
An aircraft with two engines and two fans and an APU. In take off the fans are driven by the APU, in cruise by the engines.
 
StTim
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 10:58 pm

2175301 wrote:
LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


That is not even close to the truth:

The 1st law of Thermodynamics: You cannot win. You cannot get more energy out than there is to start with.

The 2st law of Thermodynamics: You cannot even break even. As it applies to heat engines (gas turbines, boilers, internal combustion engines, etc) you are first limited by what is named the Carnot thermal efficiency equation: 1- (Tcold/Thot) Tcold is the temperature to which you are rejecting waste heat. Thot is the fluid temperature entering the process section of the heat engine (which is for a gas turbine is often less than the combustion temperature). The temperatures are in Degrees Kelvin (or Rankine for the users of the English/German system).

Thus if you assume that a modern gas turbine engine has hot gas entering the expansion section of the turbine of 1645 K (1372 C), and you are rejecting to atmospheric air at 273 K (0 C) then your best theoretical efficiency is: 1-(273/1645) = 83% (if I did the math right).

Now the turbine has a further reduction in efficiency based on the pressure ratios of the combustion chamber to the outside air pressure (the equation is a bit more complex as it also involves specific heat of the fuel and air) - but it produces a somewhat similar further reduction in possible efficiency.

My knowledge in power industry applications is that a stand alone combustion turbine rarely exceeds 45% thermal efficiency. Pair it with a back end steam cycle and you can achieve 60% in ideal situations (which is why "Combined cycle" power plants are being built - despite the high cost of the fuel).

Perhaps one of the Aircraft Turbine experts here could show us some typical actual calculations of combined Carnot and Brayton cycle efficiencies so we would know.

The 3rd law of Thermodynamics: You cannot even get out of the game... and we will leave that discussion for tech ops if someone wishes to discuss thermodynamics on that level.

Have a great day,


Saved me having to post something similar from my first year mech eng lectures 35 years ago.

From now on each improvement comes from increasing the top temp (CMC’s) or more and more marginal gains.

I read the expected efficiency improvements posted here with a wry smile.
 
Vladex
Posts: 382
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 11:37 pm

When cars and everything else goes electric, how can aviation compete? in 10 years around half of the cars will be electric and super cheap to drive, why would anyone pay to fly under 500km?
 
2175301
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 11:41 pm

Vladex wrote:
When cars and everything else goes electric, how can aviation compete? in 10 years around half of the cars will be electric and super cheap to drive, why would anyone pay to fly under 500km?


Where is all that electricity going to come from. The only substantial environmental waste gas emission free generation is nuclear. Wind and Solar don't even come close to ever being able to meet our needs based on our past usage. Even combined cycle gas turbines are still SO2 and CO2 emitters.

People talk about hydrogen. How do we get hydrogen... electrolysis of water or breaking down of Natural Gas. Electrolysis of water takes a lot of electricity...

Have a great day,
 
2175301
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Re: Engine efficiency-what are the limits?

Tue Nov 19, 2019 11:52 pm

Waterbomber2 wrote:

The temperature of the hot gas entering the turbine section vs. ambient air is irrelevant in calculating the theoretical thermodynamic efficiency of your engine.
What you would want to calculate is 1 - (Texhaust/Tturbine inlet) replacing the ambient air temperature with your exhaust gas temperature.
So it's actually much worse than that as engine exhaust is never as low as 273K.


From a practical sense you are correct. I was showing the theoretical Carnot thermal efficiency - which is based on the temperature of the available heat sink.

In theory - you could build a combustion turbine that would exhaust very close to the available heat sink temperature.

From a practical engine standpoint - especially on an aircraft where you cannot have long and huge turbine sections (as some land based power generation units have) - your point is valid on what can be practically achieved (at this point in time).

From a practical standpoint I suspect between Carnot and Brayton cycle efficiencies that the theoretical achievable if we could build the perfect combustion turbine is likely in the 60% range.

We are doing well if we are building machines that can get 3/4 of that. Most people have no idea how hard it is to build machines that can approach the theoretically possible for anything.

My understanding is that the first combustion turbine only had a thermal efficiency of 17%. It appears that we have about tippled that over the decades. That is quite the accomplishment.

Have a great day,
 
mjoelnir
Posts: 8902
Joined: Sun Feb 03, 2013 11:06 pm

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 12:43 am

2175301 wrote:
Vladex wrote:
When cars and everything else goes electric, how can aviation compete? in 10 years around half of the cars will be electric and super cheap to drive, why would anyone pay to fly under 500km?


Where is all that electricity going to come from. The only substantial environmental waste gas emission free generation is nuclear. Wind and Solar don't even come close to ever being able to meet our needs based on our past usage. Even combined cycle gas turbines are still SO2 and CO2 emitters.

People talk about hydrogen. How do we get hydrogen... electrolysis of water or breaking down of Natural Gas. Electrolysis of water takes a lot of electricity...

Have a great day,


Perhaps fuel cells get light enough for airplane use, direct conversion to electricity gives a higher efficiency than burning.

That the only substantial environmental waste gas emission free generation would be nuclear, is about as much BS as can be. The first point is cost. Any modern nuclear power plant, that fulfills today's safety standards, is prohibitive expensive to build. Not to start talking about decommissioning cost. Nuclear power plants would not exist, if the development, design and building of them, would not have had vast government subsidies. Without those subsidizes today, it is no economical viable to build them.

We are far from using all renewable resources we could use. There are big industries, that are not interested in being replaced. Oil and coal are subsidized. If not directly, than through tax incentives. Asking oil and coal to go clean would produce gigantic cost for those industries, that live on being able to pollute freely and I am not starting to talk about CO2. What does a coal using power plant does with its ash. What does a coal mine do with coal slurry and or black water. What is the water use of a coal mine and the resulting wastewater. Put a price on those things, or ask them to clean up that stuff, and coal disappears. One can make a similar list with oil, but that gets actually to expensive to burn for electricity.

Throw similar subsidizes at renewables as was done with nuclear and you will have enough electrical energy. Today new build windmills rival gas in energy cost, when build in places with enough wind. The USA for example has not started on using offshore windmills.
 
Waterbomber2
Posts: 544
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Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 2:02 am

2175301 wrote:
Waterbomber2 wrote:

The temperature of the hot gas entering the turbine section vs. ambient air is irrelevant in calculating the theoretical thermodynamic efficiency of your engine.
What you would want to calculate is 1 - (Texhaust/Tturbine inlet) replacing the ambient air temperature with your exhaust gas temperature.
So it's actually much worse than that as engine exhaust is never as low as 273K.


From a practical sense you are correct. I was showing the theoretical Carnot thermal efficiency - which is based on the temperature of the available heat sink.

In theory - you could build a combustion turbine that would exhaust very close to the available heat sink temperature.

From a practical engine standpoint - especially on an aircraft where you cannot have long and huge turbine sections (as some land based power generation units have) - your point is valid on what can be practically achieved (at this point in time).

From a practical standpoint I suspect between Carnot and Brayton cycle efficiencies that the theoretical achievable if we could build the perfect combustion turbine is likely in the 60% range.

We are doing well if we are building machines that can get 3/4 of that. Most people have no idea how hard it is to build machines that can approach the theoretically possible for anything.

My understanding is that the first combustion turbine only had a thermal efficiency of 17%. It appears that we have about tippled that over the decades. That is quite the accomplishment.

Have a great day,


It takes a while to perfect something, but evolution happens as each step gives us a better view of what is practically possible.
If we look at the turbofan as it is, there isn't much to it.

I already threw an apple in the A380 thread by suggesting that supercharged diesel piston motors would replace the APU and take care of all auxiliary services that suck energy from the engines (electricity generation, pressurisation), doing the same job much more efficiently and without weight penalty, and little waste as waste heat of the engines would be used to heat the cabin air.
Obviously, this is a free one, on the house, which is sufficient enough to illustrate that we are still far from an optimum configuration.

Combined cycle turbines are not a new thing but not easy to implement on something that isn't bolted to the ground.
If you want to capture the waste heat, you're going to need to trap it, transfer it to a fluid, then let it be absorbed by another turbine etc...
The real problem is trapping the heat and extracting it on something like a turbofan. The problem is that, like condensing boilers, trapping the heat will cause a major slow down in the exhaust air speed, in order to maximise the heat-absorption. What happens then? The air flowing through the core is slowed down to the point that it can stall readily.
 
Sokes
Posts: 438
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Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 3:47 am

Kilopond wrote:
An awful lot of the chemical energy contained in the fuel gets converted into thermal energy which is permanently °lost“. In the sense that it just gets blown into the atmosphere without any positive effect. Technics are needed that would convert that wasted thermal energy into something useful.


Could Emirates heat their shower water with it?
Why can't the world be a little bit more autistic?
 
JayinKitsap
Posts: 1647
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Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 6:49 am

2175301 wrote:
Waterbomber2 wrote:

The temperature of the hot gas entering the turbine section vs. ambient air is irrelevant in calculating the theoretical thermodynamic efficiency of your engine.
What you would want to calculate is 1 - (Texhaust/Tturbine inlet) replacing the ambient air temperature with your exhaust gas temperature.
So it's actually much worse than that as engine exhaust is never as low as 273K.


From a practical sense you are correct. I was showing the theoretical Carnot thermal efficiency - which is based on the temperature of the available heat sink.

In theory - you could build a combustion turbine that would exhaust very close to the available heat sink temperature.

From a practical engine standpoint - especially on an aircraft where you cannot have long and huge turbine sections (as some land based power generation units have) - your point is valid on what can be practically achieved (at this point in time).

From a practical standpoint I suspect between Carnot and Brayton cycle efficiencies that the theoretical achievable if we could build the perfect combustion turbine is likely in the 60% range.

We are doing well if we are building machines that can get 3/4 of that. Most people have no idea how hard it is to build machines that can approach the theoretically possible for anything.

My understanding is that the first combustion turbine only had a thermal efficiency of 17%. It appears that we have about tippled that over the decades. That is quite the accomplishment.

Have a great day,


The improvements to efficiency usually are inverse log function like the learning curve is. The closer to maximum efficiency, the more and more difficult to improve by a set amount . Gas internal combustion engines are in the later part of the curve that could be called "difficult to improve more". Turbines using a liquid fuel are not quite as far out on the curve, but still well along the way. Airplane wings are well along the curve as well, also plagued as to where in the flight the design is optimized. Otherwise planes such as the A320, B737, B747, and B767 can compete still in the arena. Had the improvements been 10% more, these would not be economic at all.

After growing up with NCAR (National Center for Atmospheric Research) in our town and visiting many times back before 2000. Currently (came on line in 2017) at the NCAR-Wyoming Supercomputing Center (NWSC) the "Cheyenne' supercomputer is an SGI ICE XA system with 4,032 dual-socket scientific computation nodes running 145,152, 18-core 2.3-GHz Intel Xeon E5-2697v4 (Broadwell) processing cores and has 315 terabytes of memory. But it still cannot handle a global weather model in real time (it takes over a day to run a day long model). Climate change models run on such super computers still have been poor at predicting 10 years out such changes. The Summit at Oak Ridge is the #1 supercomputer in the world, with 4,608 nodes (2 IBM POWER9 CPUs and 6 Nvidia Tesla GPUs / node[12]) has over 600 GB of coherent memory (6×16 = 96 GB HBM2 plus 2×8×32 = 512 GB DDR4 SDRAM) is also doing climate modelling, a far faster machine Frontier is being acquired, keeping Oak Ridge's #1 supercomputer title.

https://youtu.be/ycNQ_wqsWFc

I certainly do not believe that climate change will be the end of civilization as we know it. However, energy efficiency and resource management are essential for human progress. So yes, we should design better planes, trains, cars, trucks, ships, and even bicycles to be as efficient as practical. Stopping 5% waste means 5% better profit etc. As the world becomes more energy efficient, that means far less heat is dumped into the world and the warming effect will slow.
 
ei146
Posts: 274
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Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 8:03 am

2175301 wrote:
Vladex wrote:
When cars and everything else goes electric, how can aviation compete? in 10 years around half of the cars will be electric and super cheap to drive, why would anyone pay to fly under 500km?


Where is all that electricity going to come from. The only substantial environmental waste gas emission free generation is nuclear. Wind and Solar don't even come close to ever being able to meet our needs based on our past usage. Even combined cycle gas turbines are still SO2 and CO2 emitters.

People talk about hydrogen. How do we get hydrogen... electrolysis of water or breaking down of Natural Gas. Electrolysis of water takes a lot of electricity...

Have a great day,


Well, you have to start somewhere. Just sitting there in denial won't take you any further.
Currently 46% of all electrical energy produced in Germany comes from renewable sources (e.g. hydro power, biomass, wind and solar). I would consider that a substantial amount. In 2002 it was less than 9%. And Germany is a net exporter of electricity, we produce more than we need. More details here if you are interested.

Hydrogen production from electricity actually goes very well together with renewable energies: You can use cheap excess energy that is produced on sunny or windy days. And when demand is high and production is low (e.g. on a calm winter night) and thus electricity prices go up you stop your H2-generator.

BTW: It is a lie, that nuclear power comes emission free. The actual electricity production is. But if you look at the whole process from mining and production of nuclear fuel, building and decommissioning of the power plants and treatment and storage of the nuclear waste there is an emmission of about 30g to 120g of CO2 per kWh electricity, depending on where the fuel is coming from. And we didn't even talk about the chemical and radioactive pollution coming with the whole process.
 
2175301
Posts: 1572
Joined: Wed May 16, 2007 11:19 am

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 8:51 am

ei146 wrote:
BTW: It is a lie, that nuclear power comes emission free. The actual electricity production is. But if you look at the whole process from mining and production of nuclear fuel, building and decommissioning of the power plants and treatment and storage of the nuclear waste there is an emmission of about 30g to 120g of CO2 per kWh electricity, depending on where the fuel is coming from. And we didn't even talk about the chemical and radioactive pollution coming with the whole process.


That's fair... Now just produce a similar chart showing the emissions from building and using the other forms of generating electricity.... From the charts I've seen Nuclear Power Plants do not come out that bad (not the best, and by far not the worst).

As for wind... Here in North America every wind farm has another gas fired power plant built to be able to supply power when the wind is not blowing... yet no one here in North America seems to count the cost of the 2nd power plant into the cost of wind-power... Yet it's a very real cost.

You are correct that Germany has in fact generated a large amount of wind energy... they also found that you cannot have more than about 20% of your energy from wind due to the way its output changes as the wind changes. It makes the grid unstable; and Germany has had cases where large portions of the grid tripped off line because of the instability caused by wind generation. Not saying wind cannot play a part... but; its part is limited at the current technology of other power generation sources connected to the grid (things can only safely change so fast).

I've spent decades studying the economics and environmental effects of power production - all technologies (and I've worked in coal, gas, oil, and nuclear power generating units). I'll stand on my statement that the ONLY large scale power production technology that we have that is considered emission free (outside construction and normal operations) is Nuclear. Its also highly competitive long term (despite the initial construction cost of a modern PWR reactor). That's why there are currently about 100 new nuclear units under construction world wide by many countries. The fact that it has about a 95% capacity and availability factor is a huge bonus as well.

If we ever solve the issues with the pebble bed reactor we will almost double the thermal efficiency of nuclear plants. Pebble bed plants heat the "process" gas in a Brayton Cycle turbine; and then a steam cycle is added to the back end to provide a combined cycle plant. Current issue is that ceramic or graphite dust from the nuclear fuel pebbles is causing problems in the turbine. They are trying to solve that without adding a huge air to air heat exchanger. A pebble bed nuclear reactor could not melt down either due to its design in the event of loss of cooling gas flow. Very nifty idea... if we can make it work.

Have a great day,
 
Sokes
Posts: 438
Joined: Sat Mar 09, 2019 4:48 pm

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 9:12 am

2175301 wrote:
Where is all that electricity going to come from. The only substantial environmental waste gas emission free generation is nuclear. Wind and Solar don't even come close to ever being able to meet our needs based on our past usage. Even combined cycle gas turbines are still SO2 and CO2 emitters.


Combined cycle gas turbines are not SO2 emitters.
Nuclear makes a little bit of electricity, but including energy requirements for transport, industrial heat, heating housing... it's rather neglectable.

Image

https://en.wikipedia.org/wiki/World_energy_consumption


Wind and photovoltaic power are cheap, but can't follow demand.
However solar towers can store energy at least for some hours:

Image

source: https://en.wikipedia.org/wiki/Concentrated_solar_power



Image

"The hot storage tank at the 110 MW Crescent Dunes CSP power tower plant in Nevada holds molten salt at 565°C and can deliver 10 hours of stored solar energy at any time day or night"

source: http://www.solarpaces.org/how-csp-therm ... age-works/

The price for electricity from solar towers is between 5 - 10 cent/ kWh. We are on the steep part of the learning curve.

High Voltage Direct Current (HVDC) is required to transport electricity over long distances. Again we are still on the steep part of the learning curve.
I assume a lot of excess electricity from renewables can be put to use for house heating with heat pumps.
Combined cycle gas turbines for backup are also required.
The technology for a complete energy transition is not ready yet. But compared to where the world was 20 years ago ...
Why can't the world be a little bit more autistic?
 
Sokes
Posts: 438
Joined: Sat Mar 09, 2019 4:48 pm

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 10:03 am

2175301 wrote:

As for wind... Here in North America every wind farm has another gas fired power plant built to be able to supply power when the wind is not blowing... yet no one here in North America seems to count the cost of the 2nd power plant into the cost of wind-power... Yet it's a very real cost.

You are correct that Germany has in fact generated a large amount of wind energy... they also found that you cannot have more than about 20% of your energy from wind due to the way its output changes as the wind changes. It makes the grid unstable; and Germany has had cases where large portions of the grid tripped off line because of the instability caused by wind generation. Not saying wind cannot play a part... but; its part is limited at the current technology of other power generation sources connected to the grid (things can only safely change so fast).

...
A pebble bed nuclear reactor could not melt down either due to its design in the event of loss of cooling gas flow. Very nifty idea... if we can make it work.



Do you have a source that large portions of the grid tripped off? Is it a regular problem or did it get solved?

But you are right. One needs backup. Indeed Germany "forces" it's excess renewables on it's neighbors. I think every house/ flat above 80 square-meters should be obliged by law to have a cheap air to air heat pump. Owners have to pay a flat rate for the year and get free electricity for their heat pump whenever the wind blows.
Also Germany is world champion in lignite power production. It's the worst method concerning CO2 and old plants can't follow the load. They are only suitable for base load.
From 1997 - 2002 Niederaussem lignite power plant was built.
2006 an important addition was made: waste heat dries the lignite. It is then powdered. This type of lignite plant can be regulated down 50% to follow fluctuating renewables. At any rate lignite is the wrong fuel and hard coal plants were always used for power regulation.
In my opinion existing lignite plants should be closed down as fast as possible. Existing hard coal plants are o.k. to help with the energy transition. New plants should always be combined cycle gas turbines with attached district heating.

I think if 20 or 40% wind energy can be integrated into power supply depends on a lot of factors. With base load based on lignite one is screwed, unless one has well wishing neighbors.

I remember when I was young I read that nuclear reactors are save because in case of power failure the brake rods fall in the reactor and stop the fission. There wasn't a word about cooling requirements after that.
I also read that nuclear waste can be stored save in salt mines.
Here the result: https://en.wikipedia.org/wiki/Asse_II_mine

Well, I'm not qualifies to judge. If an operator can find an insurance I'm o.k. with nuclear.

But we can agree that one should rather close a lignite plant than a nuclear power plant.
Why can't the world be a little bit more autistic?
 
Sokes
Posts: 438
Joined: Sat Mar 09, 2019 4:48 pm

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 10:53 am

LTCM wrote:
The limit to efficiency is the number of BTUs in jet fuel. Until we hit that number, there is room to improve.


I suggest a different approach:
One has to increase the number of BTUs / kg jet fuel. Oil refineries add/ substract H or C atoms to molecules to influence what products they get. Is it possible to get fuel with much higher energy densities that way?
Especially for long range that should be attractive.
Why can't the world be a little bit more autistic?
 
RJMAZ
Posts: 1695
Joined: Sat Jul 09, 2016 2:54 am

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 11:07 am

FLALEFTY wrote:
The variable fan pitch estimates, do they include allowing for the weight reduction from eliminating thrust reversers? This is supposed to be a feature of RR's Super Fan design.


From techops. I do not think a variable pitch fan is even possible in a nacelle.

viewtopic.php?t=1427925
 
2175301
Posts: 1572
Joined: Wed May 16, 2007 11:19 am

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 3:54 pm

Lets move this back to a discussion on the efficiency and potential improvements of aircraft engines.

To close (I hope) the discussion on world wide energy use: Yes, when you include transportation, home heating, etc. electrical use (and how it's generated) is only a fraction of overall energy use.

Long term I believe (and have believed for decades) that this world needs to move away from various forms of stored hydrocarbons. Those resources are not just limited; but, also the base product is often high in sulfur and overall we have not come up with a good way to handle that sulfur (that "relatively clean" natural gas at the end of a pipeline did not start nearly so "clean").

I personally believe that long term that the world will transition to a hydrogen based fuel economy. With that hydrogen largely being generated via electrolysis from some form of nuclear (Fission/Fusion) reactors. Light hydrocarbons may even be intentionally produced to provide aviation fuel.

All major energy sources have to consider energy density (liquid hydrocarbon fuel is very energy dense), compactness (land area usage), ability to operate in almost all locations in the world, overall production and use pollution (and water usage/Chemical waste disposal is a huge issue not often discussed), capacity factors, reliability, etc. This is not the forum to actually discuss these issues. There are no perfect solutions; just compromises and better choices for different situations.

As it relates to aviation: A real question is how much total air travel is going to occur in the future due to various pollution concerns and the limits on increasing efficiency of the current turbines. Should the governments of the world decide to tax or require offsets for aviation fuel usage... cost of air travel will go up and will have a reduction effect on overall air travel. Is that effect a few % or tens of %? The future will tell us.

Have a great day,
 
ei146
Posts: 274
Joined: Sat Jan 09, 2010 9:54 pm

Re: Engine efficiency-what are the limits?

Wed Nov 20, 2019 5:20 pm

2175301 wrote:
You are correct that Germany has in fact generated a large amount of wind energy... they also found that you cannot have more than about 20% of your energy from wind due to the way its output changes as the wind changes.

I am in a dilemma somehow. I don't want to further derail the thread, but I also do not want some of your statements to go undisputed.
Looking at the link I provided we are already at 24% and growing...
2175301 wrote:
It makes the grid unstable; and Germany has had cases where large portions of the grid tripped off line because of the instability caused by wind generation.

Could you please give a reference for that statement? I live here and I think I would have noticed outages. The last major outage I remember was in 2006, and it had nothing to do with renewable energy.
What regularly happens though is that wind generators are taken off the grid on stormy days to not overload the grid. The operators don't care too much because they are compensated when this happens.
Nobody disagrees though that a grid with a lot of renewable energy needs more attention and effort to stay stable. Some needed investments are being made and will continue. So far this was succesful and non of the alarmist predictions we keep hearing for 20 years from the "old" power industry came true.

Regarding your comments on the pebble-bed reactor: I personally do not want to wait for the next holy grail, be it a new reactor type, fusion energy or whatever. Because they never come. I prefer to do already now what can be done.
2175301 wrote:
Have a great day,

You too.

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