1. WIND TUNNEL TEST - INTRODUCTION
Performance test of wind turbine in wind tunnel can be conducted in
either constant wind speed or constant rotor rpm. Under constant wind
speed, the rotor rotation speed was varied by increasing or decreasing
the load while under constant rotor rpm, the changing wind speed was matched
with load which will maintain the same rotor rpm. Both type of wind turbine
operations produce different performance curve as the average Reynolds
number on the blades is different.
The following test in wind tunnel was conducted under constant wind
speed operation as the inertia acceleration method (Musgrove, 1977) was
used. This test was conducted upon the completion of the trial test using
multiple large fans. It was hoped that a more accurate performance data
for the small 0.5mx0.5m Darrieus wind turbine model can be obtained.
The previous attempt to measure the model performance in wind tunnel
was not completed due to the unexpected lower maximum wind tunnel speed
than stated. The rotor was unable to accelerate to its maximum speed due
to this low wind speed. This testing was conducted hastily so possible
solution might be overlooked.
However, during the current second attempt, the highest wind tunnel
speed of 3.1m/s proved again to be too low for the model to operate. In
order to produce higher wind speed, a huge sidewall opening on the wind
tunnel was left open. This produce non-uniform and curved wind which will
introduce errors and limits the reliability of the result. Since this
was the only available option other than canceling the test during the
time, the test was continued in this nonstandard fashion. Careful steps
were taken in positioning the rotor in wind tunnel and measuring the wind
speeds distribution using anemometer instead of the tunnel pitot tube.
Detail result was presented here with comparison with previous fan test
result.
|
