Numerical optimization of a novel gas-gas ejector for fuelling of hydrogen vehicles

This paper focuses on the potential replacement of expansion valves in the fuelling process of hydrogen vehicle by use of ejectors. The main advantage of the ejectors is to exploit the kinetic energy of a high-pressure primary flow to entrain a lower pressure secondary flow resulting in an improved and efficient fuelling process.
First, a one-dimensional thermodynamic model was developed to characterise the ejector's performances such as its entrainment ratio and compression ratio. Then, the ejector's components efficiencies of the one-dimensional model were extracted from CFD simulations with the use of a genetic algorithm. Three regression models were compared to express the efficiencies as a function of the boundary conditions (pressure inlets) and the ejector's geometry (aspect ratio). Finally, the one-dimensional model was used to optimize the performance of the ejector for fuelling of hydrogen vehicles by using a simple transient simulation model of the vehicle tank. The new ejector fuelling procedure was compared with the traditional use of expansion valves. The results show that a reduction of the high-pressure hydrogen demand is possible using the optimized ejector, leading to reduced energy consumption, as well as fuelling time.