Abstract Computational Fluid Dynamics (CFD) simulation was employed to investigate the scale-up effect in ejectors with the Realizable k-ε turbulent model. Two kinds of ejector models, with and without diffuser angle, were established. Keeping the velocities of jet flow and suction flow, the geometric sizes of ejectors were enlarged to 3, 5, 8 and 10 times based on the original sizes and the simulations were carried out respectively. The results showed that the velocity and turbulent kinetic energy were not changed apparently after scaled up, while the turbulent dissipation rate reduced significantly as well as the vorticity magnitude. There was an approximate inverse proportional relationship between the turbulent dissipation rate and the geometric size. Moreover, the distance required for mixing completely was proportional to the scale-up factor and the dimensionless distance changed slightly. Since the turbulent dissipation rate and the vorticity were important parameters to describe the turbulent flow, it might imply that the turbulent extent would drop significantly after scaled up,which was unfavorable for the mixing behavior. It had no relationship with the angle of the diffuser.
