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.