The variable geometry ejector (VGE) used in solar-powered ejector refrigeration systems enables performance regulation with unstable heat input, which is important in solar energy utilization; however, the ejector performance is significantly affected by the nozzle configuration. To study the effects of the nozzle configuration on the VGE and to optimize the VGE configuration, experimental investigations are conducted on a supersonic nozzle and a subsonic nozzle used in the VGE under a variety of operating conditions. The experimental results show a close relationship between the driving flow behavior and the ejector performance. The driving flow behavior is influenced by the occurrence of Mach waves, which is significantly influenced by the nozzle configuration. Numerical simulations are conducted that further explain the Mach wave behavior as well as the driving flow development inside the VGE. The results are significant for the optimization and application of the variable geometry ejector in solar-powered ejector refrigeration systems. (C) 2017 Elsevier Ltd. All rights reserved.