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| Turbine from:www.pr.afrl.af.mil |
Turbine Blade Mistuning:
Turbines resemble large fans and are critical components of a jet engine. Turbines extract the energy from
the fluid flow. A good explanation of turbine use can be found on Wikipedia
Here is a good schematic of a turbine engine:
Mistuning becomes a problem in turbines which are usually designed to be rotationally symmetric, but are slightly
assymmetrical due to manufacturing variation and foreign object damage (FOD). The assymmetry causes the repeated roots
of the tuned structure to split and the associated mode shapes to become mixed. The change of modeshape can lead to
disasterous consequences if the changes happen to concentrate the strain energy in a weak location on the turbine.
Operating the engine near this natural frequency can cause to accelerated failure in this location.
Curve Veering:
Curve veering describes the mathematical phemonae that occurs when the natural frequencies of different vibrational modes
approach one another when a system paramter is modified. Often in turbine design, this can be due to phase angle around the disk
or centrifugal stiffening from engine speed. Modes can simply cross or actually veering away from one another. At the point where
the frequencies cross, the modes will interact with one another leading to the problems described above.
Laser Shot Peening:
Laser Shot Peening is a processing technique used on airframe parts and turbine blades to increase
surface resistance, fatigue strength, and fretting resistance. It used a laser to create a pulse of
plasma from a piece of tape or paint. As the material is ablated, the plasma forms and the shock wave
retained by a water confinement zone. I am interested in this affect on residual stress and vibrational
consequences such as mistuning than can result from this process.
Click here for more details on LSP.
PowerMEMS:
PowerMEMS is a broad term for micromechanical components/assemblies being used for energy generation.
Specifically, I am interested in micro-scale turbine engines with the potential to replace batteries for
high power portable devices. The energy density of liquid fuels is still orders of magnitude greater than
than of batteries. Microscale turbines rotating at millions of RPM's can possibly fill this demand, although
there are a number of obstacles that must be overcome including bearing technology, and better fluidics.
Last Updated: 26 May 2006