Colloquia

Summary

Piston pumps are frequently used in hydraulic systems. A drawback of these pumps is the unsteady flow out of these pumps, which is better known as the flow ripple. This fluctuating flow is transported through the hydraulic system causing vibrations of parts, and noise generation. This noise is not desired in for instance the automotive industry.

One of the manufacturers of piston pumps for this industry is Power-Packer. The company manufactures radial piston pumps for rooftop actuation. Power-Packer designed a new integrated design with a BLDC motor and a radial piston pump with seven pistons to meet the customer demands. However, this design is suffering from the flow ripple problem. Therefore, an investigation is necessary to identify the influencing factors of the flow ripple problem to develop design rules to generate a more steady flow.

Literature shows that different factors influence the flow out of the pump, and multiple simulation tools are used to investigate the problem. After the literature research, a simplified drawing with a functional decomposition is made to understand the product. This step is followed by a stakeholders' analysis to check whether the design is understood correctly and to check their opinion on the root causes of the flow ripple. Out of this analysis, a parametric selection is made, and the significant parameters are taken into account in further research. This information enables to make a model made in MatLab Simulink of the design.

Defining the experiments by a Design of Experiments is the next step to identify the root causes. In this DoE, five varying parameters are checked, the chopping option, the rotational speed, the excentre, the pressure, and the mass inertia. In the experiments, the minima and maxima are investigated, resulting in 48 experiments. Furthermore, some additional research is desired to check its influence on the flow ripple. These experiments enable the investigation of the effect of the motor characteristics on the flow ripple.

The results of the experiments identify the root causes, which are the rotational velocity and the excentre. These factors result in the greatest flow variation. Another significant factor is pressure, which increases the backflow dip when it increases from 50 bar to 200 bar. The other parameters show less influence on the flow ripple. In the comparison of the simulation with the lowest flow ripple and the highest ripple, the maximum flow is 9.5x higher, and the backflow dip is around 6.4x lower in the configuration with a minimum rotational speed, the pressure and excentre. All the information enables the development of the design rules to minimize the flow ripple.