Abstract

The rapidly growing requirements in en¬gine development in terms of fuel con¬sumption and emission values call not on¬ly for the optimization of the engine en¬ergy balance but also for the reduction of the power consumption of the accessories. During last years, these needs have led to the introduction of a new concept of oil pump into the automotive market, the so-called variable displacement vane pump (VOP). The oil supply to the engine is adapted to the actual needs according to each engine's working condition. Pierburg Pump Technology Italy has been one of the first companies to identify this trend and to develop and sell such type of products. The pre-design phase of a VOP is entirely performed through the analytical approach: the customer specifications usually provide the design point in terms of requested delivery flow rate at given delivery pressure and engine rotating speed (hence pump speed, for a given transmission ratio). To define the functional dimensions of the pump a specific routine has been developed in Matlab language: this basically consists of the geometrical calculation of the displacement of the pump but it also includes the evaluation of the volumetric efficiency by the calculation of the oil flow through the internal leakages of the pump. Once the geometry of the pump has been defined, a further Matlab routine is run to predict the power absorption. Each major pump internal clearance is considered to evaluate the single contribution to the total adsorbed torque due to the Coulombian and the internal fluid viscous frictions and to evaluate each contribution to the amount of oil flow provided. Anyway, there are theoretically infinite solutions that comply with a given set of specification requirements: however, the best design among all the possible solutions is the one that ensures the lowest power absorption leading to the maximum benefit in terms of vehicle's fuel consumption. At the same time, some constraints have to be taken into account due to spatial limitations of the design room and due to functional reasons linked to the product's reliability. Therefore, the design process becomes a constrained optimization problem. To perform this task Pierburg Pump Technology has introduced ESTECO modeFRONTIER as a working environment: as a first step, all the pre-design analytical tools have been linked to create one only calculation procedure. As a second step, the optimization task is performed efficiently through the available algorithms. In conclusion, the integrated process of a VOP's pre-design is carried out entirely in one tool leading to the optimum pump for each considered application.