Investigation on performance of ejectors with adjustable nozzles.

In this study, the performance characteristics of adjustable nozzles were experimentally investigated. In these nozzles, a spindle is used to control the cross-sectional area of the ejector nozzle throat, and magnetic force is used to control the position of the spindle. The change in the throat area and the controller input for the spindle were found to have a nearly linear relationship. In the experiment, the generating pressure was set to 1.9 MPa, and the back pressure was set to 0.83 MPa. A de Laval nozzle and a converging nozzle with the same throat dimensions were used in the experiment. In the results, both ejectors showed peak performances as the throat area was changed. The de Laval nozzle performed better at its peak condition, but its performance quickly dropped under off-design conditions. In contrast, the converging nozzle showed only slight changes to the performance as it was adjusted with a lower peak performance. The converging nozzle is recommended for realizing a more stable change in performance by an adjustable ejector.