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Unifying the Piaggio 125cc and 150cc engine intake systems by means of multi-objective optimization, coupling WAVE and modeFRONTIER

The present work describes the definition of a unified intake system for the 125cc and 150cc Piaggio engines, re-designed after the adoption of a new fuel and intake port system.

This challenging task could be accomplished, thanks to the integration of the parametric model of the system, which has been built with the 1D CFD code Ricardo WAVE, and the multi-objective optimization tool modeFRONTIER.

Piaggio multi-objective optimization
Fig. 1 - modeFRONTIER Workflow

Challenge description
The internal geometries (length, diameter, equivalent diameter, etc.) of the throttle body, butterfly valve, inlet air manifolds, intake port have been parameterized by means of 6 independent variables.

Then, 6 technological constraints, 9 objective functions and 2 target values have been assigned, in order to look – simultaneously - for the best power output curves of both the engines sharing the same intake system. In the modeFRONTIER workflow, the above mentioned input variables modify the WAVE models of the two engines, that are both updated and launched automatically in batch mode, driven by the logic of the optimizer: the simultaneous optimization of the intake system in order to guarantee good performances of both engines takes place in a fully automated way.

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Results
Approximately 7000 possible configurations of the intake system have been explored by modeFRONTIER driving corresponding runs of both WAVE models. All the obtained power curves are shown in figure 2.
Thanks to the flexibility of WAVE and the link with modeFRONTIER, the previous phase has been fully automated, and thus allowed to achieve evaluation results and to reach the decision process phase in a fast and accurate way, avoiding repetitive and time-consuming operations.

Piaggio multi-objective optimization Piaggio multi-objective optimization

Fig. 2 - “Cloud” of 7000 power curves (left, the ones of the 125cc engine, right the corresponding ones of the 150cc engine) obtained for each explored intake system configuration.

Fig. 3 - Scatter chart of the intake system configurations in the plane of power for 150cc (X) and 125cc (Y) at the same RPM

In the chart of fig. 3, each point represents a particular engine configuration, where its X-coordinate represents the power of the 150cc engine, while Y axis is the power of the 125cc engine at the same RPM. Red points are the best solutions marked by modeFRONTIER, with respect to all the objectives assigned simultaneously (the so-called “Pareto Frontier”). In particular the optimized configurations are the last ones in the design table.
The chosen optimal configuration found by modeFRONTIER has been then experimentally verified, and results confirmed the accuracy of the WAVE models predictions and the “goodness” of the optimization process.
The validated power output improvements, obtained all over the engines’ function range, are shown in figure 4.

Piaggio multi-objective optimization

Fig. 4 - Power curve improvements (HP, Y axis) of the optimized intake system, respect to its initial configuration, when mounted on the 150cc engine. Similar improvements, over the whole function range, have been confirmed also for the 125cc.

Conclusions
Coupling WAVE with modeFRONTIER allowed to define a common optimal geometry for the intake system to be adopted in both the 125cc and 150cc engine. This provides cost savings, as with regard to economy of scale, it means producing one instead of two different component systems, which adapts very well to the different engines in the catalogue. Another advantage of the automated and multi-objective approach, is the full exploitation of the WAVE models, that allowed to reduce drastically the number of engine test rig experiments needed to define the final solutions: this obviously leads to the reduction of design costs. Such results cannot be obtained following a traditional trial-verify approach, or a simple Design Of Experiment strategy. This, not only due to the dramatic cost in terms of tests and time needed, but also because of the physics of the problem: complex outputs and non linear responses of the considered input parameters.
Moreover, only this truly multi-objective approach and the seamless integration between WAVE and modeFRONTIER, allow to find a unified solution for the two different engines in very short time.

 

 

 


 

Articolo pubblicato sulla Newsletter EnginSoft Anno 5 n°1

 

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