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\chapter[CONCLUSION, RECOMMENDATIONS, AND FUTURE WORK]{CONCLUSION, RECOMMENDATIONS, AND FUTURE WORK}
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\section{Configuration One}
The experimental characterization of the
electromechanical performance of the partial-hybrid turbo-electric
aircraft ground test vehicle was accomplished. The peak power
generated was about 4-kW, which was used to power the right-wing
motor along with 13-kW of power from the battery. The total engine
output was around 150-kW. The electrical power generated was
significantly more than the 0.72-kW generated by the original
engine alternator. Based on the performance metrics of the engine,
the maximum power output and the speed of the turboprop were kept
well within the nominal range.\\
The interdependent time response of the combined machine was
interesting. The turbine engine was operating at 150-kW of shaft
power whenever the generator was fully engaged at 4-kW. The
battery met the required load, but the turboprop was slowed down by
the generator and took almost 5-s to return to the nominal RPM
value. The slow response of the turbine to such a minor adjustment in
power was unexpected. The power split between the generator and
the battery during the transition from low to medium throttle was
also of particular interest. The current flow from the generator
changed only slightly with the difference being made up by the
battery. The reason for the slight change was an impact on
the rotational speed of the generator and its effect on output voltage.
The slowdown from the near-constant turboprop shaft speed led to a
3-V decrease in the output of the generator. Because the output
voltage of the generator was so close to the battery voltage, this
decrease in voltage significantly impacted the current output and
prevented it from meeting the electrical system demand. Once the
turboprop rotational speed returned to normal, the generator was
able to produce more current.\\
Additionally, a failure mode caused by a short in the left ESC was
identified. The bus voltage dropped considerably from 106-V to
somewhere near 40-V. The current output of the ESC reached at
least 550-A and drew a minimum of 46-kW of power from the
battery. The power system was able to temporarily accommodate the
failure, but it highlighted that the power system needed to be able to
accommodate a power failure that pulled all available electrical
power in the system.\\
Finally, a qualitative analysis of the acoustic signature of the
aircraft testbed showed there was little difference between the
OASPL of the aircraft with and without the electric propeller
operating. This demonstrates that the dominant noise source is likely
the turboprop engine or acoustic interactions related to the turboprop
engine. A cowling with acoustic dampening material could
potentially change this outcome, especially since the engine in this
configuration is not enclosed.
