Rachel Weber, Gabby Ruhe, Elliott Dehnbostel, Daniel Keffer
System Analysis 1
Group G-Instr. John Schrock, GTA Jin Yang
October 13, 2015
Executive Summary
In this lab, engineers tested propulsion efficiency through a tunnel testing system. Engineers then
performed calculations for each type of propeller in order to determine which type was the most
efficient. Engineers used a wind tunnel, propeller, motor, and Wind Tunnel Testing Sheet (Table 1,
Appendix A) to complete this lab. Engineers focused on how to make their AEV more efficient during this
lab. To do this, they worked with the propulsion efficiency. Propulsion efficiency is a combination of the
propeller efficiency and the motor efficiency. In order to determine the total efficiency, engineers
calculated a ratio between the power output and total power input.
There are several conditions that may affect the propulsion efficiency. Friction, torque, speed, blade
size, blade angle, and blade design are all factors that affect propulsion efficiency. The wind tunnel
testing focused specifically on how blade design affects efficiency. The two blade designs used were a
push blade design and a pull blade design. The push blade design pushes air behind the AEV to help
propel the AEV forward. The pull blade design pulls air up into the AEV to help propel the AEV forward.
The wind tunnel was in charge of moving air through the propellers so that engineers could test each
propeller to determine power input/ output, calibrated thrust, advance ratio, and propulsion efficiency.
The power input calculates the amount of power that was initially applied to the propeller. The power
output calculates the power that the AEV is outputting by multiplying the thrust of the AEV by the
velocity of the AEV. The calibrated thrust is determined by taking the change in thrust from 0% power
and then multiplying that number by a constant of .411. The advance ratio is determined by taking the
velocity and dividing it by the propeller RPM ties the propeller diameter. The propulsion efficiency is
determined by dividing the power output by the power input. The goal was to have a high propulsion
efficiency, meaning less input of energy for maximum output.
After completing this lab, the team has decided to remain using a puller propeller system. When
comparing Figure A to Figure B, it is clear by the thrust curves that a puller system is more efficient for a
vehicle that will run on maximum motor power settings than a pusher system is. A puller system starts
with lower thrust but increases exponentially to a greater thrust than a pusher system, which starts with
a higher thrust but increases very little when using additional power.
One possible source of error that could occur during this lab and skew data would be an obstruction in
front of the wind tunnel caused by group members or furniture. If the wind tunnels were situated
further apart from each other and the students were given more space, this could resolve that error.
Another source of error would be that the Arduino board would display fluctuating results, forcing
students to either pick between two values or average them together.
For the future, sample data for this lab should be assembled and sent out to the students by the end of
the lab period. Not being able to reference the proper data made it difficult for the team to assess which
propulsion system would work better for their AEV. If possible, more stations to fetch data should be set
up.
Appendix A
Figure A
Figure A is a chart plotting the thrust Vs. the percent power of the arduino for a puller style propeller. It
shows that with an increase in power the thrust increases on an exponential curve. If thrust was the only
desired result maximum power would be the most ideal setting. The puller propeller is ideal for max
power situations.
Figure B
Figure B is a chart of thrust Vs. power but of a pusher style propeller. The pusher propeller had a higher
initial thrust but had a more gradual curve resulting in less high power thrust. This would suggest it
would be better for low RPM use.
Figure C
Figure C is a chart of the propulsion efficiency Vs. the advance ratio of the puller Propeller. This shows
the connection between the efficiency and the rotation of the blades. The system peaks efficiency at
about 0.40 advance ratio. This is the optimal setting to produce the maximum thrust for the least
amount of energy. If the advance ratio is any more or less either thrust or energy would be sacrificed.
Table 1
Table 2
Table 3
Table 4
Table 5
Individual Calculations
Rachel
Arduino power setting of 25% and 0.5 Amps
Calibrated Thrust:
Tc = 0.411 (T-T0)
T = 178.6g
T0 = 167.3g
Tc = 0.411(178.6-167.3)
Tc = 4.64g
Power Input:
Pin = V*I*(P%/100)
V = 7.4 Volts
I = 0.5 Amps
P% = 25%
Pin = 7.4 V * .5A *(25/100)
Pin = 0.93 watts
Power Output:
Pout = Tc * V
Tc = 0.0455 N
V = 2.8 m/s
Pout = 0.0455 *2.8
Pout = 0.1273 watts
Advance Ratio:
J = V/ (RPM/60)*D)
V= 2.8 m/s
RPM = 4670 RPM
D = 0.0762 m
J = 2.8/((4670/60)*0.0762)
J = 0.47
Propulsion Efficiency:
Nsys = (Pin / Pout)*100
Pin = 0.93 watts
Pout = 0.1273 watts
Nsys = (0.93/0.1273)*100
Nsys =13.78%
Daniel
Arduino power setting of 40% and .83 Amps
Power Input
P = V*I*(P / 100)
V=7.4 Volts
I= .83 Amps
P = 40%
P = 7.4V * .83A*(40/100)
P = 2.46 watts
in
%
%
in
in
Power Output
P =T *v
T = .1237 N
v = 2.8 m/s
P = .1237 * 2.8
P = .3463 watts
out
c
c
out
out
Calibrated Thrust
T = .411(T-T )
T = 198g
T =167.3 g
T = .411(198-167.3)
T = 12.62 g
c
0
0
c
c
Advance Ratio
J = V/((RPM/60)*D)
V= 2.8 m/s
RPM= 6946 RPM
D= .0762 m
J = 2.8/((6946/60)*.0762)
J= .32
Propulsion efficiency
N = (P / P )*100
P = 2.46 watts
P = .3463 watts
N =(.3463/2.46)*100
N = 14.09 %
sys
in
in
out
sys
sys
out
Gabby
These calculations use the reference point of current being 0.2 amps.
Calibrated Thrust
T = .411(T-T )
T = 167.3 g
T = 168.6 g
T = .411(167.3-168.6)
T = .53 g
c
0
0
c
c
Power Input
P = V * I * (P / 100)
V = 7.4 volts
I = .2 amps
P = 10 watts
P = (7.4)*(.2)*(10/100)
P = .15 watts
in
%
%
in
in
Power Output
P =T *v
T = .0052 N
v = 2.8 m/s
P = (.0052)*(2.8)
P = .01 watts
out
c
c
out
out
Advance Ratio
J = v/((RPM/60)*D)
v = 2.8 m/s
RPM = 2035
D = .0762 m
J = 2.8/((2035/60)*.0762)
J = 1.08
Propulsion Efficiency
n = (P /P )*100%
P = .01 watts
P = .15 watts
n = (.01/.15)*100%
n = 9.91%
sys
out
in
sys
sys
out
in
Elliott
Arduino power setting of 30% and 0.61 Amps
Power Input
P = V*I*(P / 100)
V=7.4 Volts
I= .62 Amps
P = 30%
P = 7.4V * .61A*(30/100)
P = 1.37 watts
in
%
%
in
in
Power Output
P =T *v
T = 0.0722 N
v = 2.8 m/s
P = .0722 * 2.8
P = .2021 watts
out
c
c
out
out
Calibrated Thrust
T = .411(T-T )
T = 185.2g
T =167.3 g
T = .411(185.2-167.3)
T = 7.36 g
c
0
0
c
c
Advance Ratio
J = V/((RPM/60)*D)
V= 2.8 m/s
RPM= 5508 RPM
D= .0762 m
J = 2.8/((5508/60)*.0762)
J= .400
Propulsion efficiency
N = (P / P )*100
P = 1.37 watts
P = 0.2021 watts
N =(0.2021/1.37)*100
N = 14.75 %
sys
in
in
out
sys
sys
out