Hi Slawomir,

do you have an idea, how big can be the amplitude of the vibration? or with which precision you need to measure?

best regards,

Guilherme

I would propose this way: the narrow laser ray reflected by the blade and compared by any processing algorithm (correlation for instance) with insident laser wave. This is used special service in technology of the eavesdropping talk through window glass.

Tip timing is very expensive (more than 100 k€), so forget about it. Strain gages are cheap but it is unlikely you can measure the vibration of all the blades. You have to select a subset of blades. The problem is to bring the signal out from the rotor to the stator. In our lab (www.aermec-dimec.polito.it) at Politecnico di Torino we use a 24-channel telemetry system. To stay cheaper (but with a higher noise/signal ratio) you could use slip rings.

well a very good alternative for your problem would be an interferometer or an oct.

Depending on the system construction, with an oct you can get measurement frequencies over 100kHz with a measurement range in milimeters.

Another interesting system is the interferometric displacement sensor of the company attocube. (http://www.attocube.com/attoMETROLOGY/introduction.html). Which can measure even in mega herz.

Howdy Slawomir,

How are you doing? Valarm (www.valarm.net) provides an economical way to measure vibrations using an accelerometer.

Use a cheap $30 or less Android device and you're doing data acquisition! Your data can later be viewed on a map and downloaded in kml or csv. Full sensor list is here: http://www.valarm.net/about/device-features-list/

Have a great day.

Sincerely,

-Edward.

http://www.valarm.net

Fist, look at static frequency response of your device (without dynamic loads due to rotation): a simple measuremet with one accelerometer an an impact hammer can give you helpfull results about your structure behaviour. However, dynamic loads due to rotation should not be neglected.

For this kind of measurements, you can use a cheap accelerometer mounted on the axis bearings and correlate the measurement with a trigger given a (white) mark on the axis, detected by an optical sensor. This will give you a good idea abour the rotor out ov axis movement that you may correlate to blades vibrations.

You also may use piezoelectric film (pvdf) stuck directly onto the blades and measure the blade vibration, but you will then need a rotating contact (with all the problems it may cause).

The better, however all but cheap: use Polytec laser scanning system with de-rotator an you will measure the blade vibrations. Well it is worth the price of several 100 000 $ ... if you get the fundings. You also may rent such a test device.

http://www.polytec.com/us/news/videos/derotator-video/

If your blade is metallic, then take for the first simple vibration measurement, an eddy current sensor and apply the displacement function. e.g. micro epsilon systems ca. 5000,00 € or develop one coil yourself and use existing electronic devices from your lab (amplifiers, oscilloscope).

You may use SLAM STICK Vibration recorder. It has a 3D accelerometer with recording facility. Details can be found at http://www.mide.com/products/slamstick/slamstick_vr001.php

Hi,

To measure rotating blades amplitude you need to use data acquisition and accelerometer to measure overall vibration . Thereafter you can analysis collected data using Empirical mode decomposition method to decompose data into intrinsic mode functions(IMF) that related to each component of rotating machinery from high to low frequencies. You can determine shaft, bearings, gear and fan pass frequency .......

I hope that helps

Thank you for all helpful answers

You can use uniaxial accelerometer 100mV/g with DT9837 DAQ sampling rate 52.7 kHz and use the MATLAB to perform the analysis.Total cost of system is about 1800 euro only. you will get precise measurement with these low cost system.

You can use the blade tip timing method - See papers of PIWG and EVI-GTI member. The idea this method is desribed also in my articles and monography.