MONTANA STATE UNIVERSITY
DEPARTMENT OF MECHANICAL ENGINEERING
ETME 491 Fall 2015
Wind Energy Engineering
R. Larson
Lab 4: Wind Turbine Component Vibration
Discussion:
Loading scenarios in wind turbines can often result in component vibration. As
outlined in the Manwell text, turbine towers and individual turbine blades are
essentially cantilever beams.
In this laboratory, students will investigate harmonic response of structures,
and utilize advanced measurement equipment to analyze vibration modes of
representative components.
Equipment:
Laser Vibrometer with associated computer DAQ system and power
electronics
Power Amplifier
Function Generator
Mini-Shaker and Brass rod test article
Small wind turbine blade test articles (2)
Ruler / calipers
Exercise:
OBJECTIVE:
Determine the natural frequencies and mode shapes of beams from
experiment, and compare theoretical predictions with experimental results.
both from theory and, and compare the results. Observe the phenomena of
nodes and resonance.
DATA: The mass and relevant geometry of test rods: use 8.4 Mg/m and 110
GPa for the mass density and elastic modulus of brass, respectively, 3.18 mm
(0.125 in) diameter, and 450.9 mm (17.75 in) length (verify in the lab).
2) Determine the first three natural frequencies of the brass rod detailed
above in fixed-free
configuration.
LAB PROCEDURE:
1) Take the round brass rod and center it in the shaker clamp (which
now simulates two
cantilevered beams). Measure the length of the rod in this configuration.
2) Knowing approximately where to look, find experimentally the first natural
frequency of the
brass cantilever beam by increasing the frequency of the shaker and noting
the changes in the
mode shape as a natural frequency is encountered. Note the magnitude of
the first natural
frequency.
3) Now excite the beam to mode 2. Note the magnitude of the mode 2
frequency and record the
position of the corresponding node(s) on the beam. Repeat for mode 3.
QUESTIONS AND CALCULATIONS FOR CONSIDERATION:
1) Compute the theoretical natural frequencies of the round brass beam and
compare these to
the measured values (% difference). From theory, predict the nodal locations
and compare to
the measured nodal locations (% difference). Assemble these results in a
table and discuss
the comparisons.
2) Why is it important that a mechanical designer know the mode shapes and
node locations of
a vibrating beam or other structure? Give specific examples.
Results:
1. Calculate theoretical wind power. (You'll need to use the Ideal Gas
Law ρ=p/RT to find density)
2. Determine power produced from measurements of voltage and current.
3. Calculate system efficiency. as a function of KEwind versus Wind Turbine
Kinetic Energy (i.e. Power produced during some known time period:The time
period can be found from a sample of your data, knowing sample rates and
point count you can determine time.)
4. Report on availability and capacity factor:
For your Availability calculation, use the percentage of time that your
completed rotor assembly is ready to produce power -versus- the entire 1hour
50 minute lab duration.
For your Capacity Factor calculation, you'll need a turbine output power
rating: For this exercise, RATE your turbine at 5 milli-watts nameplate
capacity.
5. Submit an ELECTRONIC lab report via D2L Drop Box, using proper format. One
report per group. List all participating group members.