Observation made
After experimenting by making models of windmills based on the current three-bladed wind turbine, I have discovered that making a flap on each of the blades improves the performance of the windmill. Thus, I have decided to do an experiment to explore how these flaps affect the performance of windmills.
Hypothesis statement
The larger the ratio of the surface area of the blades to surface area of flap of the windmill, the faster it will spin.
Topic of Investigation
Bernoulli's Principle: Factors affecting the performance of a windmill: Ratio of the surface area of the blades to the surface area of the flaps
Research Question
Main: How does the ratio of the surface area of the blade to the surface area of the flap affect the number of revolutions the windmill makes per minute?
Sub: What is the optimum ratio?
Short summary on research done on area of investigation
Windmills with three blades have been proved to be the most effective and efficient in harnessing the energy from the wind, able to make the most energy out of the smaller gusts of winds and able to withstand strong winds, thus I have decided to use a model of windmill based on the current design of wind turbines.
The blades of the windmill rotate by creating lift, much like an airplane. According to Bernoulli's Principle, "as the velocity of a fluid increases, its pressure decreases" (Quoted from: http://library.thinkquest.org/27948/bernoulli.html). In this case, when the wind blows, it causes high-pressure air to form under the flap, as the air has to travel a shorter distance, pushing the flap, causing the windmill to spin. This is called lift. On the other side of the flap, where the air has to travel a longer distance, low-pressure air is formed, thus pulling the blade towards it. This is called drag.
Bibliography
Bernoulli's Principle, http://library.thinkquest.org/27948/bernoulli.html, retrieved 13/4/13
Wind energy basics: How wind turbines work, http://www.nrel.gov/learning/re_wind.html, retrieved 13/4/13
Wind turbines, http://www.gurit.com/files/documents/2_aerodynamics.pdf, retrieved 13/4/13
The experiment
Independent variable:
-The surface area of the blade
Dependent variable:
-Speed of the windmill (Rpm)
Constant variables:
-Number of blades the windmill has
-Length of blades of the windmill
-Size of blades of windmill
-Position of windmill from the fan
-Time (1 min)
Apparatus and materials:
-Straws
-Pins
-A fan
-Camera
-iMovie software
Product:
4 windmills with blade to flap surface area ratios of 1:1, 2:1, 3:1, 4:1 respectively.
Procedures
How
to make the windmill (Self-designed)
1. Cut out an
equilateral triangle of sides 5cm. (I decided to change this to 7cm as I found 5cm too small to be effective)
2. Find the middle
of the triangle by drawing lines from each of the tips to the mid-point of the
respective opposite sides.
3. Mark points
0.5cm away from the middle of the triangle on the lines drawn. Link them by
drawing a straight line in between.
4. Connect the
points on either side of the lines marking the middle of the windmill and draw
it to touch the respective vertexes of the triangle.
5. Mark out points
1cm on the left of the lines that have just been drawn. Draw another line
connecting the point to the respective vertexes of the triangle.
6. Cut it out.
7. Fold the flaps
towards you.
8. Take the pin and
pierce it through the middle of the blades with the flaps facing you.
9. Cut off 1.5cm of
the straw.
1 Slide the straw
onto the pin and pin the blades onto the rest of the straw with the 1.5c, bit
of the straw between the blades and the straw.
Procedures
1. Paint one blade
of the windmill. This blade will be the marker to count how many revolutions it
makes in a minute.
2. Set the fan to
the lowest speed.
3. Align the
painted blade to the straw.
4. Hold the
windmill 140cm away from the fan. Let it spin for 1 minute. Film this on a
camera.
5 Repeat steps 1-4
with the other windmills.
Using the iMovie software,
slow down the video and count how many times the painted blade passes the
straw. This will be the number of revolutions the windmill makes per minute.
Assumptions and Limitations
Assumptions:
-There are no surrounding winds
-The wind is always blowing directly at the windmill
-No wind escapes the windmill
-The wind speed is constant
Limitations:
-The surrounding wind cannot be controlled, thus it may affect the results.
-Lack of apparatus to measure the wind speed
-Not the best representative of the current model of wind turbine--The flaps act as the curvature of the wind turbine blades, but is limited as the model's blades cannot curve like the real turbine. Also, the weight of the materials used in the model are not proportional to the weight of the materials used in the real turbine.
No comments:
Post a Comment