Fluid dynamics Optimization of racing engine inlet ducts at Aprilia Racing

Alberto Clarich, Giulio Cassio, Lorenzo Barzelatto (Esteco, Aprilia Racing)

CHALLENGE - Racing engines are experiencing a continuous evolution that brought them to extraordinary levels of performance and complexity. At the same time, racing regulations are restricting considerably development of the engine by adding constraints to the main design components. As a consequence, improving performances of racing engines has become increasingly challenging, where traditional design methods have become less effective and a significant and incremental contribution of simulation is required. 

SOLUTION - In this paper, a method to perform fluid dynamics optimization of intake valves and intake ports of the Aprilia RS-GP motorbike is presented. The purpose is to develop a procedure in which parametric geometry design, automatic mesh generation and three-dimensional CFD analysis are coupled with different optimization techniques – using modeFRONTIER, with the aim of improving fluid dynamic efficiency of valve and port while guaranteeing their feasibility. The parametric geometry has been built with PTC Creo Parametric. ANSYS ICEM CFD has been used to generate a structured mesh of tetrahedral elements using the octree algorithm. Finally, to quantify the fluid flow performances of each candidate solution, a full 3D steady state simulation model has been defined in ANSYS CFX. The fluid domain has been modeled in order to replicate the experimental bench used for results validation, considering a fixed valve position at the maximum lift and throttle wide open. To model the turbulent flow inside the cylinder the two equations k-omega SST model is used.











BENEFITS - As a result, the discharge coefficient – at maximum valve lift – of both valve and port has been improved, respectively of 1.5% and 2%. These results have been validated experimentally and confirmed the simulation phase outcome, with measured improvements of 1.2 % and 1.6 % respectively. It is interesting to note that the result obtained by the valve optimization approach has shown improvements even at lower valve lift ratios, while the optimization has been carried out only at fixed high valve lift ratio (0.4 h/D). This is essential to keep low computational effort and time and ensure a robust solution at other engine operating conditions.