Numerical analysis of transport phenomena for designing of ejector in PEM forklift system

• Using CFD to design ejectors in PEM fuel cell systems for forklift applications.
• Studying limitations of a single ejector at different loads.
• Suggesting to use of a dual-ejector and investigate its performance for a wide range of loads.
• Comparing part-load performance of a dual-ejector with a single ejector but with variable nozzle geometry.

In the present study, Computational Fluid Dynamics (CFD) technique is used to design an ejector for anode recirculation in an automotive PEMFC system. A CFD model is firstly established and tested against well-documented and relevant solutions from the literature, and then used for different ejector geometries under different operating conditions. Results showed that a single ejector with optimized geometry cannot cover the required recirculation in the entire range of the fuel cell current. Having two ejectors for different ranges of currents is thus proposed as an alternative solution in which the system can better take the advantage of ejectors for recirculation purpose. In addition, the operating mode of one variable nozzle ejector has been investigated and compared with aforementioned cases. The results showed that the variable nozzle ejector can work in the same operational mode as in the case with two ejectors. However, in practice, the latter one needs a more complicated control system and it is more difficult to manufacture.