Comparison of novel variable area convergent-divergent nozzle performances obtained by analytic, computational and experimental methods

•A novel model of variable area convergent-divergent nozzle is presented.•Experimental and numerical studies of the supersonic ejector have been conducted.•The flow is visualized for different values of spindle positions and outlet pressures.•The velocity of the primary fluid at the nozzle exit is in accordance with the one dimesional analysis.•The performances are presented through relations between entrainment ratio, outlet pressure and spindle position. Different applications of a variable area convergent-divergent nozzle are found in various parts of the industry. This paper presents the development of a new design methodology for a variable area convergent-divergent nozzle, to maintain constant nozzle area ratio for different values of mass flow rates. The validation of the presented model was carried out on an example supersonic ejector using experimental, numerical and analytical data. Analytical (one dimensional) and computational fluid dynamics models showed satisfactory prediction performance in comparison with the experiment. The average entrainment ratio error was between 10% and 7%, respectively. Results confirmed that the velocity of the primary fluid at the nozzle outlet is in accordance with the one dimensional analysis. Although disturbances (strong and weak shock waves) are visible, their effects are negligible. Also, supersonic ejector performances are presented through relations between entrainment ratio, outlet pressure and spindle position. Disadvantages of variable area nozzle utilization in ejector applications are emphasized.