Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Joshua Crawford - Virginia State University
This research primarily studied the properties and abilities of propellers. Using a small experimental setup, the thrust force of three spinning propellers were recorded in direct comparison to the amount of voltage (and current) received by the motor. The three propellers being the ultimate dependent variables differed by only their number of blades; three blades, four blades, and five blades. It is important to note that each blade across all propellers are the same in area. This results in the only difference between trials to be the area of water contact across each propeller. Prior to the experiment it was hypothesized that the three blade propeller would be the most efficient of the propellers. Although, much of the evidence gathered imply that this hypothesis is presumed correct, more data and research are needed in a more stable experiment to exercise this claim as true. It was hypothesized that out of a three blade, four blade, and five blade propeller the three blade propeller would have the highest efficiency and resistance to cavitation as theorized from the above background information. The logic guiding this hypothesis being that cavitation is said to occur faster on propellers moving at equal RPMs with more blades. Therefore, the lower number of blades takes an increase of load at the cost of more efficient thrust force from reduced cavitation. After analyzing the given information it appears that all three began undergoing cavitation at roughly the same time, approximately at 6.5 volts. I believe the reason the 4 blade propeller stayed consistent in its thrust force through 6-7 volts was because it was also the only propeller made of the black slightly more sturdier plastic. This plastic also proved to be sturdier after the experiment finished when the 3 blade’s and 5 blade’s propellers (both made of the blue plastic) began breaking and wearing heavily on their edges. This might also explained why the 4 blade propeller outperformed the other propellers so easily. Observational wise, the highest amount of force produce was indeed by the 4 blade propeller at 2.3 newtons of force. Although, all three propellers were supposedly printed from the same 3D printing machine, the type of ABS+ plastic may have different. That was one of the unforeseen sources of error in the experiment. In addition, all of the measured readings in this experiment came with numerous deviations (±)that steadily became more inaccurate the longer the experiment was perform, but still enough to make reading the scale difficult and the outcomes not as specific as desired. Overall the experiment was a great learning experience that must be improved if its data is to be more clear and accurate for future testing.
Funder Acknowledgement(s): This work was supported in part by the HBCU-UP of the National Science Foundation under NSF Cooperative Agreement No. HRD-1036286. Any Opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation.
Faculty Advisor: Jahangir Ansari, email@example.com
Role: All parts except ordering parts which was done by my advisor.