Sam Evans, Anthony Lokar, System Analysis 3
Alejandro Nunez, Benjamin Schneider
Group A – Instr. Richard Busick, GTA Jin Yang March 5th, 2015
Executive Summary
During the third system analysis procedure, the team became familiar with propulsion system efficiency and with the wind tunnel and thrust stand equipment. The team also conducted wind tunnel testing on an electric motor and propeller and analyzed the wind tunnel testing results, and, once all the recordings were conducted, the propulsion efficiency performance characteristics were updated. This analysis procedures assists in recording new performance data to create a more accurate efficiency equation to then build a more efficient code.
From the data collected during lab, the group could tell that the propellers are more efficient when put in the pusher orientation. From the graph, the difference between the pusher and puller orientation grows as the advanced ratio grows (see Figures 1 and 2 in the Appendix). This will help the group decide which way to orientate the propellers on the AEV. In order to make the AEV more efficient, the vehicle should be in the pusher orientation both ways. The AEV has already been designed with propellers at both ends to account for this efficiency. Also, from the graph, it was noted that as the AEV revolutions per minute (RPM) of the propeller increased, the power also increased (see Figure 1 in the Appendix). This can aid the group with the coding for the AEV. The group should be able to discover a power for the AEV that will maximize the RPM, while keeping the power as low as possible. The team also calculated measures of calibrated thrust, power input, and power output. These values can be seen in Tables 2,4,6, and 8 in the Appendix for comparisons of individual wind tunnel reading comparisons.
Although no errors were encountered during the conducting the lab procedure, possible errors could have been made during the data analysis. If the team failed to note small details such as the diameter of the propeller tested in the wind tunnel or misread values in the chart, the calculations could have been thrown off. These incorrect calculations have the potential to skew the new advanced propeller ratio equation found in the lab. The team avoided such errors by inquiring instructional staff during multiple points of the data collection process.
The team recommends that any equations used during data analysis are checked multiple times. By using a program such as excel, small errors in one cell can propagate when referenced to others. This effect can skew results and cause misinterpretations to occur. It is also recommended that adequate time is given before collecting data from the wind tunnel between power changes. If a team member takes readings directly after the power has been decreased in the wind tunnel, the values will be skewed. By allowing the Thrust Stand Data Acquisition System time to update results, accurate values for RPM and thrust can be attained.
This lab allowed the team to gain experience modifying standards by comparing them to experimental results. The team utilized the EP-3030 Pusher Propeller to obtain readings of thrust and RPM, which were converted to measures such as propulsion efficiency and advanced ratio (See Tables 1-8 in the Appendix). By plotting this data and adding a trend line, a new, more accurate equation to calculate the propulsion efficiency were found for each of the 4 propeller configurations. It was also noted that as the revolutions per minute increased, the efficiency of the propeller decreased. The team will utilize this information during the first performance test in order to determine an efficient code for the AEV to complete the tasks outlined in the Mission Concept Review Statement.
(Due to the number of images, the click “Appendix” to open it in a new page)