Aerospace engines must run at higher temperatures to meet the latest engine fuel efficiency requirements. But these higher temperatures require intricate schemes to cool the engines. To create the needed complex cooling passages, two ancient arts — brazing and investment casting — have re-emerged. These processes require strong metal alloys and ceramics because the core material must withstand the extremely high temperatures used to pour them.

Looking for any feedback, comments, or thoughts on this materials aerospace article here>>

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Hello Marshall, when I had just read the beginning of your comment I thought: "Higher temperatures? I think it's time to ceramics to step in aeropace engines.". I work on aerostructures not on engines. I'm familiar with the conventional aerostructures materials, Al alloys and composites. I don't know much about ceramics but I'm sure they will play a lead role on the future, and present, aerospace engines.
What kind of ceramics specifically are talking about?
Thanks,
Joao - I referenced the article where the details on the materials are covered. http://www.designworldonline.com/articles/4959/10/New-Materials-Tak...

best,
Marshall

João Lopes said:
Hello Marshall, when I had just read the beginning of your comment I thought: "Higher temperatures? I think it's time to ceramics to step in aeropace engines.". I work on aerostructures not on engines. I'm familiar with the conventional aerostructures materials, Al alloys and composites. I don't know much about ceramics but I'm sure they will play a lead role on the future, and present, aerospace engines.
What kind of ceramics specifically are talking about?
Thanks,
Although my background is aerospace I am not well schooled in engines. Why is it necessary for the engines to run at higher temperatures? Do higher temperatures release more energy from the combustion, or is it more engine crammed into smaller spaces, or do higher temperatures support better decomposition of waste and pollution products? I realize this is tangential to your main topic, but I was hoping to get better educated on the "why" before trying to learn more about the "how".

Thanks!
Interestingly, the struggling automotive industry may be the best place to look for expertise in the materials craft. Ten years ago, the indiana/ohio/michigan auto manufacturers were too busy to give aerospace companies the time of day. That was then... when auto production volumes were many times that of the aerospace industry. Yet with the ever-changing business environment, one might be surprized to find favorable assistance from this precious US talent pool. We hare having success in this area now where we were ignored in years past.
Hi Craig,
The main point of the news item you refer to was about new materials that could handle the higher temperatures now employed by jet engines. I have not worked on jet engines either, so I don’t have all the information you might want. But here are a few thoughts on the subject for you. Because a jet engine is essentially a form of heat engine, heat engine efficiency is determined by the ratio of temperatures reached in the engine and those exhausted from the propelling nozzle, which in turn is limited by the overall pressure ratio you can achieve from the design. Rocket engines, for example, have a high cycle efficiency of about 60% due in part to their ability to achieve extremely high combustion temperatures. This ability enables designers to choose very large, energy efficient propelling nozzles that form the exhaust jet used to deliver maximum velocity from the engine. Turbojets, on the other hand, typically have lower combustion temperatures and nozzle efficiencies, partly due to a typical cycle efficiency that is nearer to 30%. Hope this helps.

Craig Bondy said:
Although my background is aerospace I am not well schooled in engines. Why is it necessary for the engines to run at higher temperatures? Do higher temperatures release more energy from the combustion, or is it more engine crammed into smaller spaces, or do higher temperatures support better decomposition of waste and pollution products? I realize this is tangential to your main topic, but I was hoping to get better educated on the "why" before trying to learn more about the "how".

Thanks!
Hi Leslie:

So to test my understanding of what you explained, then the temperature in the combustion chamber is analogous to the available heat (energy) for increasing pressure at the exhaust, but some of this heat is lost as the energy moves from the combustion chamber to the exhaust. Heat loss is because no engine can be 100% efficient in transferring the heat energy. Consequently for a specific engine design, higher temperatures anywhere along this path equals additional energy available to increase the pressure at the exhaust.

So any material that allows higher temperatures anywhere along this path and/or decreases the amount of heat energy lost during the transfer improves the engine's ability to create thrust.

Have I got it?

Thanks!
Craig

Leslie Langnau said:
Hi Craig,
The main point of the news item you refer to was about new materials that could handle the higher temperatures now employed by jet engines. I have not worked on jet engines either, so I don’t have all the information you might want. But here are a few thoughts on the subject for you. Because a jet engine is essentially a form of heat engine, heat engine efficiency is determined by the ratio of temperatures reached in the engine and those exhausted from the propelling nozzle, which in turn is limited by the overall pressure ratio you can achieve from the design. Rocket engines, for example, have a high cycle efficiency of about 60% due in part to their ability to achieve extremely high combustion temperatures. This ability enables designers to choose very large, energy efficient propelling nozzles that form the exhaust jet used to deliver maximum velocity from the engine. Turbojets, on the other hand, typically have lower combustion temperatures and nozzle efficiencies, partly due to a typical cycle efficiency that is nearer to 30%. Hope this helps.

Craig Bondy said:
Although my background is aerospace I am not well schooled in engines. Why is it necessary for the engines to run at higher temperatures? Do higher temperatures release more energy from the combustion, or is it more engine crammed into smaller spaces, or do higher temperatures support better decomposition of waste and pollution products? I realize this is tangential to your main topic, but I was hoping to get better educated on the "why" before trying to learn more about the "how".

Thanks!
Wow, I must say, I AM familiar with Jet engines and that was a GREAT explanation! Kudos.

Leslie Langnau said:
Hi Craig,
The main point of the news item you refer to was about new materials that could handle the higher temperatures now employed by jet engines. I have not worked on jet engines either, so I don’t have all the information you might want. But here are a few thoughts on the subject for you. Because a jet engine is essentially a form of heat engine, heat engine efficiency is determined by the ratio of temperatures reached in the engine and those exhausted from the propelling nozzle, which in turn is limited by the overall pressure ratio you can achieve from the design. Rocket engines, for example, have a high cycle efficiency of about 60% due in part to their ability to achieve extremely high combustion temperatures. This ability enables designers to choose very large, energy efficient propelling nozzles that form the exhaust jet used to deliver maximum velocity from the engine. Turbojets, on the other hand, typically have lower combustion temperatures and nozzle efficiencies, partly due to a typical cycle efficiency that is nearer to 30%. Hope this helps.

Craig Bondy said:
Although my background is aerospace I am not well schooled in engines. Why is it necessary for the engines to run at higher temperatures? Do higher temperatures release more energy from the combustion, or is it more engine crammed into smaller spaces, or do higher temperatures support better decomposition of waste and pollution products? I realize this is tangential to your main topic, but I was hoping to get better educated on the "why" before trying to learn more about the "how".

Thanks!

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