Experimental investigation of a double-slider adjustable ejector under off-design conditions

An undesirable working performance and relatively narrow operating conditions range restrict the ejector popularization and application in the industry. In this study, a novel double-slider adjustable ejector was proposed, which can adjust the throat diameters of the primary nozzle and mixing section synchronously so as to achieve its continuous and smooth operation with a high entrainment ratio in a wide operation condition. Firstly, mathematical model of the adjustable mechanism was developed, and the test device of the ejector performance was established. Secondly, the experiments of the primary flow pressure and the reduction rate of the primary mass flow rate as variables were investigated for the double-slider adjustable ejector. The results indicated the critical adjustment range of the primary flow pressure was 0.7-1.0 MPa. Within the range, the critical adjustment range of the reduction rate of the primary mass flow rate should be lower than 42.27%, and the optimal range should be within 31.27%. In this optimal range, the entrainment ratio was 0.23-0.29. Finally, the performance of the single-slider and double-slider adjustable ejectors was compared, and it was concluded that the double-slider ejector had a higher entrainment ratio and a more stable working range, the maximum increment in average entrainment ratio of the double-slider adjustable ejector was 34.5% than that of the single-slider adjustable ejector. But the critical backpressure of the double-slider adjustable ejector was lower, the phenomenon was more prominent when the reduction rate of the primary mass flow rate exceeded 42.27% and the primary fluid pressure was lower than 0.8 MPa. This study can provide a beneficial reference for the further design of adjustable ejectors under off-design conditions.