5 ms·

Old jet engines are super noisy. Modern jet engines are much much quieter.

by zip1234 4y ago

solardev 4y ago
What makes the newer engines so much quieter?
- HPsquared 4y ago
  They have larger fan blades, for one. That means they move a large volume of air relatively slowly, instead of a small volume of air moving quickly. Consider the difference between a large shop fan, and a small high pressure compressed air nozzle commonly used in workshops for cleaning, with both sized to give the same "reaction force" (i.e. the same thrust). The high-pressure nozzle makes much more noise.
  - chasil 4y ago
    The metallurgy of the fan blades has also vastly improved. Monocrystaline fan blades have very different material properties from the polycrystaline blades that (I am guessing) were used on Concorde. https://www.americanscientist.org/article/each-blade-a-single-crystal https://www.americanscientist.org/article/each-blade-a-singl...
    - solardev 4y ago
      Thanks for sharing that link! It's amazing what people were able to come up with in the 60s, before computers and Wikipedia and 3D modeling... wow. One of the patents mentioned is how VerSnyder was able to grow a turbine blade in a monodirectional crystalline structure: https://patents.google.com/patent/US3260505?oq=versnyder+1966 https://patents.google.com/patent/US3260505?oq=versnyder+196... just using a special mold and a specific alloy. That would later form the turbine blades of the SR-71 Blackbird.
      - chasil 4y ago
        I just reread it. All of it was familiar, but I had forgotten a few of the details. The first monodirectional blades were introduced to commercial jet engines in 1974, so Concorde definitely did not have this technology with the original engines.
gsnedders 4y ago
Plus a significant impact of Concorde was the (very turbulent) flow from the reheat; from memory it's not really dissimilar to many modern military aircraft with reheat today. They'll get a fair gain from just not having reheat, yet alone the rest of the benefit of decades of aerodynamic design around engine exhaust flows.
- solardev 4y ago
  Reheat = Afterburner, for any USAsians reading: https://en.wikipedia.org/wiki/Afterburner https://en.wikipedia.org/wiki/Afterburner (I didn't know and had to look it up)

Old jet engines are super noisy. Modern jet engines are much much quieter.

solardev 4y ago

What makes the newer engines so much quieter?

HPsquared 4y ago
They have larger fan blades, for one. That means they move a large volume of air relatively slowly, instead of a small volume of air moving quickly. Consider the difference between a large shop fan, and a small high pressure compressed air nozzle commonly used in workshops for cleaning, with both sized to give the same "reaction force" (i.e. the same thrust). The high-pressure nozzle makes much more noise.
- chasil 4y ago
  The metallurgy of the fan blades has also vastly improved. Monocrystaline fan blades have very different material properties from the polycrystaline blades that (I am guessing) were used on Concorde. https://www.americanscientist.org/article/each-blade-a-single-crystal https://www.americanscientist.org/article/each-blade-a-singl...
  - solardev 4y ago
    Thanks for sharing that link! It's amazing what people were able to come up with in the 60s, before computers and Wikipedia and 3D modeling... wow. One of the patents mentioned is how VerSnyder was able to grow a turbine blade in a monodirectional crystalline structure: https://patents.google.com/patent/US3260505?oq=versnyder+1966 https://patents.google.com/patent/US3260505?oq=versnyder+196... just using a special mold and a specific alloy. That would later form the turbine blades of the SR-71 Blackbird.
    - chasil 4y ago
      I just reread it. All of it was familiar, but I had forgotten a few of the details. The first monodirectional blades were introduced to commercial jet engines in 1974, so Concorde definitely did not have this technology with the original engines.

gsnedders 4y ago

Plus a significant impact of Concorde was the (very turbulent) flow from the reheat; from memory it's not really dissimilar to many modern military aircraft with reheat today. They'll get a fair gain from just not having reheat, yet alone the rest of the benefit of decades of aerodynamic design around engine exhaust flows.

solardev 4y ago
Reheat = Afterburner, for any USAsians reading: https://en.wikipedia.org/wiki/Afterburner https://en.wikipedia.org/wiki/Afterburner (I didn't know and had to look it up)