PRINTING UPDATES
After the first round of printing was examined, it was determined that for manufacturing small intricate parts such as these, SLA would most likely yield better results. This led to the decision to investigate the difference in performance of the VAWTs depending on whether they were printed on a SLA machine or a FFF machine. This new parameter replaced the idea of changing the print densities of the parts. Changing the type of additive manufacturing process that was used required a change in material as well. A summation of all the printing sessions can be found in Table 1.
Table 1: Total Print Sessions
Printing with an SLA machine produced blades with a smoother surface finish and the desired cross-sectional shape was maintained.
TESTING
To test each of the turbines they were placed on a generator in front of a fan and allowed to spin. This can be viewed in the video below.
A collection of small tubes are connected to the front of the fan to create a more laminar flow. The velocity of the wind (V) was previously measured and found to be 2.93 m/s. Each of the turbines have a cross-sectional area (Ac) of 25 in2, along with an air density of 1.2 kg/m3 the following equation was used to calculate the wind power.
A resistor box and oscilloscope were attached to the generator to determine the electrical power produced.
The resistance was adjusted gradually in order to find the maximum possible efficiency for each of the wind turbine specimen.
The following plot depicts the efficiency of each turbines as a function of resistance.
The highest efficiency was achieved by the turbine with a high solidity and a twist angle of 120 degrees, printed by an SLA machine. This efficiency is 30 times higher than the max achieved by the low solidity turbine with a 0 degree twist angle, also printed by an SLA machine. This data also indicates that a higher solidity allows for a higher efficiency and that a twist angle of 120 degrees produces a higher efficiency than one of 0 degrees. However, it is inconclusive regarding SLA vs FFF.