Multi-Factor Design for a Vacuum Ejector Improvement by In-Depth Analysis of Construction Parameters

A vacuum supersonic ejector is an indispensable pneumatic device placed in nearly all industrial production lines. This device, also called a zero-secondary flow ejector, is characterized by the maximum entrained flow and the minimum secondary pressure. Numerical simulations were carried out by means of the CFD toolbox OpenFOAM v8 and its solver HiSA, which uses the AUSM+up upwind scheme. A single-factor analysis of eight parameters was performed to find how the ejector's performance was enhanced or decreased, while other parameters were fixed. Four parameters were subject to further analysis to find the geometry that improves the standalone performance of the ejector. The mixing chamber length is the parameter that most improves its performance; alone it leads to a 10% improvement. A multi-factor analysis, based on a fractional factorial design, is carried out with the four relevant parameters. Results indicate that the multi-factor analysis enhances the performance of the ejector by 10.4% and the mixing chamber length is the factor that most influences the improvement. Although a multi-factor design improves the performance, no significant relevance has been detected with respect to the mixing chamber length improvement alone. The improved performance of this device leads to a reduction in operating time and, as a consequence, results in significant energy savings.