Studies on Ejector Systems for Hydrogen Fuel Cell

Abstract

An ejector is a pumping device which exchanges energy between a high energy primary fluid and a relatively low energy secondary fluid to produce a discharge of intermediate specific energy level but higher mass flow rate. The present study addresses a new method to control the performance of a variable ejector system which is applied to a hydrogen fuel-cell system to economize the fuel consumption. Although the variable ejector concept had been proved, its flow characteristics have not yet been established for meeting the industrial demands. Towards achieving this objective, in this paper, detailed experimental and numerical studies have been carried out and the characteristic curves are generated to understand the effects of the ejector throat area ratio and the operating pressure ratio on the entrainment of secondary stream. In the experimentation a movable cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio, which controls the mass flow rate of the suction flow. In the numerical study, a fully implicit finite volume scheme of the compressible, Reynolds-Averaged, Navier-Stokes equations employed. The results show that the variable ejector can control the recirculation ratio by changing the throat area ratio and the operating pressure ratio.