Turbine engines

Silverwall wrote:
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It's not the concept that is difficult it is the technical execution with high temp and strength compressor blades. You can use stainless stell with naval steam but you need exotic alloys for the Gas turbines, Just look at the jumo engines on the ME 262. They used stainless basically and as a result had to be rebuilt from the ground up every 10 hours of opperation because they burned themselves up.

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If you take a look at: Free Range Topic/High efficiency, Low pollution, DIY itself wood stove, and get a set of plans:
they tried stainless for the updraft riser, but had to go to ceramics, under some circumstances, temperatures can peak at 2500 degF. And they didn't even have any moving parts except the gases.
IIRC, there are some gas turbines using high temp, high strength ceramics for blades, but I don't know the details

The other issue with building high bypass turbofan turbines like those discussed above is that you need a VERY good grasp of aerodynamics and fluid flow to correctly shape the air flow. Get it wrong and your into the wonderful world of compressor stalls https://en.wikipedia.org/wiki/Compresso ... evelopment you can work round it but you need maths way beyond where safehold is now. Centrifugal compressors like the early english jets are much less complex but cannot be expanded in power like axial units can so rules out the more powerful applications including all high bypass options.

Basically advanced calculus and preferably a proper computer. You could get Owl to do this for you but then you get back to the problem of handing over solutions rather than actually getting safeholdians to think for themselves.

Here is the sketch outline from wikipedia on the topic of axial compressors https://en.wikipedia.org/wiki/Axial_com ... _equations now imagine trying to understand that when you only discovered arabic numerals and calculus 5 years ago.

Silverwall wrote:
snip

It's not the concept that is difficult it is the technical execution with high temp and strength compressor blades. You can use stainless stell with naval steam but you need exotic alloys for the Gas turbines, Just look at the jumo engines on the ME 262. They used stainless basically and as a result had to be rebuilt from the ground up every 10 hours of opperation because they burned themselves up.

snip

The Jumo's used carbon steel blades as the Chromium needed for stainless steel was unavailable (as by that stage of the war the trad route to Turkey had been cut). For longer life they were aluminum plated (which turned into alumina ceramic when the turbines were lit). A good pilot could get 50 to 60 hours out for the engines by being very careful with the throttle as rapid movements (quicker than 1 minute from open to closed) would shatter the alumina coating and kill the engine very rapidly.
This also made the jets very vulnerable during landing as the throttle once closed committed you to a landing (with or without bullet holes).

Silverwall wrote:The other issue with building high bypass turbofan turbines like those discussed above is that you need a VERY good grasp of aerodynamics and fluid flow to correctly shape the air flow. Get it wrong and your into the wonderful world of compressor stalls https://en.wikipedia.org/wiki/Compresso ... evelopment you can work round it but you need maths way beyond where safehold is now. Centrifugal compressors like the early english jets are much less complex but cannot be expanded in power like axial units can so rules out the more powerful applications including all high bypass options.

Basically advanced calculus and preferably a proper computer. You could get Owl to do this for you but then you get back to the problem of handing over solutions rather than actually getting safeholdians to think for themselves.

Here is the sketch outline from wikipedia on the topic of axial compressors https://en.wikipedia.org/wiki/Axial_com ... _equations now imagine trying to understand that when you only discovered arabic numerals and calculus 5 years ago.

Ahhh... It's all coming back to me...

I recall (oh so many decades ago - so the information is certainly dated) my course in gas turbine aerothermodynamics and the course book authored by Sir Frank Whittle (who patented his design in the 1935 timeframe). At the time, all of hic calculations were performed using a slide rule. At the time, today's exotic alloys were unavailable.

Sir Frank designed a very basic gas turbine engine (a "turbojet" as opposed to a turbofan) and constructed it using the materials available at the time.

Believe me - if I was able to understand it (and he explained it in such a way that yes, I DID understand it), even a bowling ball should be able to understand it!

We've come a long, long way since his initial design. We've optimized it seven ways to Sunday. But if you're willing to build an inefficient, low-temperature version then it will definitely work. Won't be the most reliable thing in the world, but it will definitely work.

For reference: https://en.wikipedia.org/wiki/Frank_Whittle

WeberFan wrote:

Silverwall wrote:The other issue with building high bypass turbofan turbines like those discussed above is that you need a VERY good grasp of aerodynamics and fluid flow to correctly shape the air flow. Get it wrong and your into the wonderful world of compressor stalls https://en.wikipedia.org/wiki/Compresso ... evelopment you can work round it but you need maths way beyond where safehold is now. Centrifugal compressors like the early english jets are much less complex but cannot be expanded in power like axial units can so rules out the more powerful applications including all high bypass options.

Basically advanced calculus and preferably a proper computer. You could get Owl to do this for you but then you get back to the problem of handing over solutions rather than actually getting safeholdians to think for themselves.

Here is the sketch outline from wikipedia on the topic of axial compressors https://en.wikipedia.org/wiki/Axial_com ... _equations now imagine trying to understand that when you only discovered arabic numerals and calculus 5 years ago.

Ahhh... It's all coming back to me...

I recall (oh so many decades ago - so the information is certainly dated) my course in gas turbine aerothermodynamics and the course book authored by Sir Frank Whittle (who patented his design in the 1935 timeframe). At the time, all of hic calculations were performed using a slide rule. At the time, today's exotic alloys were unavailable.

Sir Frank designed a very basic gas turbine engine (a "turbojet" as opposed to a turbofan) and constructed it using the materials available at the time.

Believe me - if I was able to understand it (and he explained it in such a way that yes, I DID understand it), even a bowling ball should be able to understand it!

We've come a long, long way since his initial design. We've optimized it seven ways to Sunday. But if you're willing to build an inefficient, low-temperature version then it will definitely work. Won't be the most reliable thing in the world, but it will definitely work.

For reference: https://en.wikipedia.org/wiki/Frank_Whittle

But Frank Whittle's work is still technology that is 50-75 years more advanced than what is available on Safehold. Depending on the specific technology, cutting edge Safehold tech is Earth equivalent of ~1750 - 1900, depending on the specific technology. Yes, once an Owl-enhanced researcher is able to touch a subject, 50 years of research and the equivalent of millions of hours of the most brilliant minds staring off into space with odd looks on their face, can be accomplished in a few months. But this is a world that is just introducing the Bessemer process. Even the materials Whittle had available in 1935 are "exotic".

WeberFan wrote:

Silverwall wrote:The other issue with building high bypass turbofan turbines like those discussed above is that you need a VERY good grasp of aerodynamics and fluid flow to correctly shape the air flow. Get it wrong and your into the wonderful world of compressor stalls https://en.wikipedia.org/wiki/Compresso ... evelopment you can work round it but you need maths way beyond where safehold is now. Centrifugal compressors like the early english jets are much less complex but cannot be expanded in power like axial units can so rules out the more powerful applications including all high bypass options.

Basically advanced calculus and preferably a proper computer. You could get Owl to do this for you but then you get back to the problem of handing over solutions rather than actually getting safeholdians to think for themselves.

Here is the sketch outline from wikipedia on the topic of axial compressors https://en.wikipedia.org/wiki/Axial_com ... _equations now imagine trying to understand that when you only discovered arabic numerals and calculus 5 years ago.

Ahhh... It's all coming back to me...

I recall (oh so many decades ago - so the information is certainly dated) my course in gas turbine aerothermodynamics and the course book authored by Sir Frank Whittle (who patented his design in the 1935 timeframe). At the time, all of hic calculations were performed using a slide rule. At the time, today's exotic alloys were unavailable.

Sir Frank designed a very basic gas turbine engine (a "turbojet" as opposed to a turbofan) and constructed it using the materials available at the time.

Believe me - if I was able to understand it (and he explained it in such a way that yes, I DID understand it), even a bowling ball should be able to understand it!

We've come a long, long way since his initial design. We've optimized it seven ways to Sunday. But if you're willing to build an inefficient, low-temperature version then it will definitely work. Won't be the most reliable thing in the world, but it will definitely work.

For reference: https://en.wikipedia.org/wiki/Frank_Whittle

Note that I am specifically talking high bypass here in response to earlier comments. One of the big issue with Whittle style engines (centrifugal compression) is that to get more compression you have to make the compression disk wider and that is directly in opposition to a high bypass turbofan which needs a narrow core and high axial compression so you can pass most of the air around the outside at moderate compression as a ducted fan drive.

And now just to stir things up a bit!

When I read through this thread, and through others in this forum, I always have smile and ask myself - "Why do we keep finding perfectly logical reasons why something WON'T work, and think about how ingenious people can be when it comes to finding ways that DO make things work?"

Case in point: I watched an episode of "Mythbusters" one time where they made a cannon out of ice. Was it practical? Nope. Was it ultimately workable? Nope. Was it hilarious to see this ice cannon shattering into a million pieces on TV? You betcha! But was the concept at least feasible? I think it was. Not in the form that they actually built it, but as a starting point. And nothing more than that.

So as we move into the discussion of turbine engines, I think not about exotic materials and advanced mathematics, but about a caveman engine. Perhaps not practical, perhaps not durable, perhaps not even feasible in its first (or even its first half dozen) iterations.

But workable as a CONCEPT. Workable as a STARTING POINT.

Howsym's people have repeatedly shown how innovative they can be when someone just gives them an idea. Or when someone ties together two disparate ideas. And then turns them loose to think about it and explore a bit. Think about the revolver innovation with metal cartridges and how it came about, resulting in a crude sketch that was shown to Howsym. And from that one discussion came a dramatic increase in short-range firepower.

These are the things I really enjoy reading about in David's books, perhaps because he drives to the core of the human spirit - the spirit of exploration. The spirit of encountering a barrier and not just saying "too hard, too much trouble." Instead saying "If we can't go through it, can we work around it?" or "What if we make the shotgun cases out of reinforced paper?"

I think we as readers tend to project our Earth-like preconceptions and biases onto the Safeholdians. We unconsciously think that because we have the neat, mature technologies available today that the maturity of those things should be the starting point for the same innovations on Safehold. IMHO "It don't work that way."

Yes, I DO realize that today's technologies are (in most cases) the result of decades (or I guess centuries in many cases) of experimentation and thought. But global war is a most efficient way to spur innovation and new thinking. And innovations developed for wartime use often (dare I say very often) have non-wartime applications.

So ever time the Mad Wizard Weber throws a concept out, I put on my engineer hat and think about how it might be done given what they have as a technology base. What tradeoffs might they need to make? If something won't work, is there an alternative? Is there some other material? Some other path? Something that IS available to them that WOULD enable them to at least prove the concept? Personally, I think this might be Owl's most value - in guiding Howsym and others in the College to the possibilities, and to the allowable (under the proscriptions) alternatives.

WeberFan wrote:And now just to stir things up a bit!

When I read through this thread, and through others in this forum, I always have smile and ask myself - "Why do we keep finding perfectly logical reasons why something WON'T work, and think about how ingenious people can be when it comes to finding ways that DO make things work?"

Case in point: I watched an episode of "Mythbusters" one time where they made a cannon out of ice. Was it practical? Nope. Was it ultimately workable? Nope. Was it hilarious to see this ice cannon shattering into a million pieces on TV? You betcha! But was the concept at least feasible? I think it was. Not in the form that they actually built it, but as a starting point. And nothing more than that.

So as we move into the discussion of turbine engines, I think not about exotic materials and advanced mathematics, but about a caveman engine. Perhaps not practical, perhaps not durable, perhaps not even feasible in its first (or even its first half dozen) iterations.

But workable as a CONCEPT. Workable as a STARTING POINT.

Howsym's people have repeatedly shown how innovative they can be when someone just gives them an idea. Or when someone ties together two disparate ideas. And then turns them loose to think about it and explore a bit. Think about the revolver innovation with metal cartridges and how it came about, resulting in a crude sketch that was shown to Howsym. And from that one discussion came a dramatic increase in short-range firepower.

These are the things I really enjoy reading about in David's books, perhaps because he drives to the core of the human spirit - the spirit of exploration. The spirit of encountering a barrier and not just saying "too hard, too much trouble." Instead saying "If we can't go through it, can we work around it?" or "What if we make the shotgun cases out of reinforced paper?"

I think we as readers tend to project our Earth-like preconceptions and biases onto the Safeholdians. We unconsciously think that because we have the neat, mature technologies available today that the maturity of those things should be the starting point for the same innovations on Safehold. IMHO "It don't work that way."

Yes, I DO realize that today's technologies are (in most cases) the result of decades (or I guess centuries in many cases) of experimentation and thought. But global war is a most efficient way to spur innovation and new thinking. And innovations developed for wartime use often (dare I say very often) have non-wartime applications.

So ever time the Mad Wizard Weber throws a concept out, I put on my engineer hat and think about how it might be done given what they have as a technology base. What tradeoffs might they need to make? If something won't work, is there an alternative? Is there some other material? Some other path? Something that IS available to them that WOULD enable them to at least prove the concept? Personally, I think this might be Owl's most value - in guiding Howsym and others in the College to the possibilities, and to the allowable (under the proscriptions) alternatives.

I wonderful point of view, the problem is that like the Ice cannon you mention you run into the problem stated so elequently by one of the original Star Trek crew.

"I canna' change the laws of physics captain"

I don't think any readers object to things such as the improved revolvers or the use of paper cartridges as these are things that are known to be historically accurate solutions to these problems that are easily within the available materials and manufacturing techniques.

The problem arrises when you try to persuade us that a technology well beyond the demonstrated tech base is being implimented. This includes issues such as the tensile strength of ice in your cannon example . This is the core of the cannon problem you mention, I do not believe that ice will ever make a good cannon and the mythbusters themselves have demonstrated several times materials that would work better than ice. Some engineering problems can be solved creatively by adding mass or re-arranging the components or redistributing the forces in a novel way. E.g. suspension bridges being much better and lighter than traditional pylon designs. But even as in the suspension bridge design you are dependent on certain mechanical properties to achieve these results. Specifically you can't build a large suspension bridge without metal cable, a small one not built of metal is called a rope bridge and they don't scale very well at all.


This problem is particularly common in the area of engines. Often the principals of how they work are brain-dead easy but the mechanics of executing it are painfully difficult. So much of your performance is tied to micrometric precision, advanced materials and being able to model advanced mathematics concepts. Just look at petrol engines. All the core components were in place by the end of WW1, certainly by the early 30s but engines from that era only produce a small fraction of the power of modern engines for the same fuel consumption, weight and displacement because of those better materials and mathematical models.

Silverwall wrote:This problem is particularly common in the area of engines. Often the principals of how they work are brain-dead easy but the mechanics of executing it are painfully difficult. So much of your performance is tied to micrometric precision, advanced materials and being able to model advanced mathematics concepts. Just look at petrol engines. All the core components were in place by the end of WW1, certainly by the early 30s but engines from that era only produce a small fraction of the power of modern engines for the same fuel consumption, weight and displacement because of those better materials and mathematical models.

In relation to turbines I believe that Charis can match or possibly even exceed the efficiency of water turbines available today. Steam turbines will not surprise most readers, even if there will be several percent efficiency they will be leaving behind due to material and control issues. Jet turbines are still out due to much more severe material and control issues.

Water turbines work at basically room temp and at up to several hundred PSI, Safehold metallurgy has been able to produce materials that work here easily, pre-Merlin. The most Merlin and OWL could do to improve efficiency would be to provide better blade designs.

Steam turbines while not seen yet, are likely to appear in the next book or two. IF they start trying to max out the efficiencies of steam power, it will require insulated boilers and super critical steam. Steam with temps well in excess of 3000 degrees and 3000 PSI will strain if not exceed the ability Safehold has to build boilers and turbines. Then there is lubricating the valves and bearings. Note train engines never used super critical steam, with I believe most US steam locomotives maxing out around 300PSI. Ships have the room to mount a super critical plant, but by the time plants of this temp and pressure were developed, ships had mostly transitioned to diesel or gas turbine engines. In WWII the US used high pressure steam engines in its warships, but this was IIRC 600 PSI as compared to RN usage of 300 PSI.

I thought Howsmyn used steam turbines for his industrial air compressors?