Challenge
Pipistrel’s engineers faced the challenge of designing a propeller
driven by a hybrid-electric propulsion system while taking into
account the different conditions an aircraft encounters during
the four phases of flight: takeoff, climb, cruise, and descent.
Considering that the requirements for speed, power, and thrust
change during flight, the objective was to maximize takeoff thrust
and power recovery during descent and minimize power use during
the climb and cruise phases. The optimization involved three
stages: the preliminary optimization of the propeller, optimization
of the airfoil, and the final optimization of the propeller.
Solution
For this multi-phase optimization project, Rok Lapuh and David
Eržen, aerodynamics engineers at Pipistrel, used modeFRONTIER
coupled with CHARM (Comprehensive Hierarchical
Aeromechanics Rotorcraft Model) and XFOIL, an interactive
program for designing and analyzing subsonic isolated airfoils.
By taking advantage of ESTECO’s process automation technology,
Pipistrel could automate the simulation workflows, evaluate
thousands of designs simultaneously and identify innovative
optimized results. This process was conducted completely
autonomously leaving Pipistrel’s engineers only with the task of
selecting the most appropriate design.
In the first propeller optimization, Pipistrel optimized the chord
and torque distribution to achieve maximum thrust and minimum
power for a given set of airfoils. These results were then used as
the requirements for the airfoil optimization. The design team used
modeFRONTIER to design the airfoil based on specific geometric
constraints (thickness, curvature, or leading-edge radius), while
increasing lift and reducing drag. They initiated a Design-of-
Experiments phase and then used the HYBRID genetic algorithm to
successfully perform the airfoil optimization and obtain the Pareto
front with the optimal designs. Lastly, they used the optimal airfoil
for the final propeller optimization. With the ESTECO optimization
algorithms, Pipistrel’s engineers were able to evaluate nearly five
thousand designs in a limited time and increase thrust by 30%
during takeoff.
Benefits
Before using modeFRONTIER, Pipistrel used a manual process
to simulate multiple designs and choose the preferred one. After
introducing the ESTECO technology, Pipistrel’s engineers were not
only able to automate this process but could also evaluate options
that would otherwise not have been considered. "modeFRONTIER
optimization technology gave me the opportunity to think outside the box," said Rok Lapuh, Aerodynamics Engineer at Pipistrel,
“We could find a design that is completely different to what we
are used to, but that may work even better.” The company has
also dramatically reduced its time to market as it has moved
from the simulation directly to production. “We trust the results
we get with modeFRONTIER so much that we do not expect to
require a prototype,” stated David Eržen, Aerodynamics Engineer
at Pipistrel, "We will go straight into production."
Newsletter EnginSoft Year 18 n°3
About Esteco
ESTECO is an independent software company, highly specialized
in numerical optimization and simulation process and data
management. With a 20-year experience, ESTECO supports
over 300 international organizations in excelling in their digital
engineering experience, accelerating the decision making process
and reducing development time. Ford Motor Company, Honda,
Lockheed Martin, Toyota and Whirlpool are just a few of the major
companies relying on ESTECO technology. ESTECO is the owner of
VOLTA, the collaborative web platform for Simulation Process and
Data Management and design optimization, and modeFRONTIER,
the comprehensive solution for process automation and optimization
in the engineering design process.
esteco.com
