Wind Tunnel Testing

Summary:

Testing was performed using a wind tunnel to determine the effects of different power settings on the efficiencies of a propellor’s output. This information is critical for determining a power setting that will ensure maximum output while efficiently using the power of the battery. If the battery’s power is inefficiently used throughout the AEV run, it could result in the battery being drained and a suboptimal performance.

Figure 1 – Wind Tunnel Settings

Wind Tunnel Air Speed Propeller Configuration Battery
m/s volts
2.8 Pull 7.4

 

Figure 2 – Results for Variable Power Settings

Current Thurst Scale Reading RPM Arduino Power Setting
amps grams RPM %
-0.01 143.5 0 0
0.08 144.3 2095 10
0.16 145.9 3113 15
0.26 147.9 3952 20
0.35 150.3 4670 25
0.45 153.3 5449 30
0.55 156.7 6167 35
0.65 160.3 6946 40
0.75 164.1 7544 45
0.84 168 8143 50
0.93 172.3 8802 55
1.04 176.5 9401 60

 

Figure 3 – Power Settings Analysis

Thrust Calibration RPM Power Input Power Output Power Output2 Propulsion Efficiency Advance Ratio
grams RPM Watts Horsepower Watts %
0 0 0 0 0 #DIV/0! #DIV/0!
0.3288 2095 0.0592 1.20991E-05 0.009022272 15.24032432 0.943422715
0.9864 3113 0.1776 3.62972E-05 0.027066816 15.24032432 0.634908637
1.8084 3952 0.3848 6.65449E-05 0.049622496 12.89565904 0.500119076
2.7948 4670 0.6475 0.000102842 0.076689312 11.84390919 0.423227107
4.0278 5449 0.999 0.000148214 0.110522832 11.06334655 0.362721708
5.4252 6167 1.4245 0.000199635 0.148867488 10.45050811 0.32049142
6.9048 6946 1.924 0.00025408 0.189467712 9.847594179 0.284548026
8.4666 7544 2.4975 0.000311551 0.232323504 9.302242402 0.26199239
10.0695 8143 3.108 0.000370534 0.27630708 8.890189189 0.2427202
11.8368 8802 3.7851 0.000435566 0.324801792 8.581062376 0.224547897
13.563 9401 4.6176 0.000499086 0.37216872 8.059786902 0.210240463

 

Results:

Testing shows that there is a direct correlation between a lower power setting for the Arduino and an increase in propulsion efficiency. A minimal propeller output will be required to propel the AEV to the caboose as efficiently as possible. If this is not done at maximum efficiency, then when the AEV needs to pull the caboose at a higher required thrust there could be reduced performance. Also, as the battery’s power is decreased it could cause inconsistent results leading to the AEV performing differently than anticipated. The motors will be tested to determine the lowest possible power setting to ensure that power efficiency is maximized, while also ensuring that the run’s time remains reasonable.