Frequency testing on turbine wheels in a turbo
Frequency testing on turbine wheels in a turbo
(OP)
I am currently doing a study on the Natural frequency on Tubine wheels, The study consists on Hitting the blades of the wheels several times, recording the sound and using sigView software to show use the Natural Frequency.It is intended to find any harmfull blade resonant conditions when operating a max speed.
I am looking for ideas which maybe in the manufacturing stages of the wheel which may vary the frequency of the wheel. I have looking at the injection moulding pressure, temperture of the wheel, Blade Dampining( to find the individual frequency of each blade. My next step is going to be the tooling of part and position on the runner during manufacturing!
Does any one know any other areas which may cause this vary in frequency in turbine wheels in the turbo!
thanks
neil
I am looking for ideas which maybe in the manufacturing stages of the wheel which may vary the frequency of the wheel. I have looking at the injection moulding pressure, temperture of the wheel, Blade Dampining( to find the individual frequency of each blade. My next step is going to be the tooling of part and position on the runner during manufacturing!
Does any one know any other areas which may cause this vary in frequency in turbine wheels in the turbo!
thanks
neil





RE: Frequency testing on turbine wheels in a turbo
RE: Frequency testing on turbine wheels in a turbo
Another major factor will be aerofoil shape, since most modes will be perpendicular to the chord line. Axial flow units go to great pains to ensure that the neutral axis in bending and shear lie on the same point throughout the blade, ideally with mass centre at the same point.
You could use Master Series, with a simulated centrifugal acceleration, then do Modal Analysis. Really form change is going to be the main factor in "tuning" blades. You can increase gap from stators to rotors, or even soften the leading edge - this will reduce the input into the blade. Gas turbines used to use mid span snubbers to help damp any modes, but this is now considered a clumsy solution.
Eccentric solutions (always worth rejecting): Use silicon fluid in a central cavity to mechanically damp blade. Coat blade in polymer (depending on temp). Go for composite blades. Get a Gas Turbine expert like Alstom or Rolls-Royce in.
Above all, let us know how you get on - Knowledge exchange is the main purpose of this forum...
Mart