Experimental and numerical studies on the performance of supersonic multi-nozzle ejector

•The starting characteristics, the operating characteristics and the mixing characteristics of four-nozzle and single-nozzle ejectors with the same design parameters were compared by experiment and numerical simulation.•The different starting states of the multi-nozzle ejector were clarified through the experimental data, and furthermore, the generation mechanism of different states were explained through numerical simulation.•Through experimental studies, it is clear that the multi-nozzle ejector is more suitable for high compression ratio conditions, compared with the single-nozzle ejector.•It was found that the non-mixed length for the single-nozzle ejector has a linear relationship with the entrainment ratio. The nozzle number influence the performance of the supersonic ejector. To figure out the different characteristic of the supersonic multi-nozzle ejector (MNE), this paper focused on two specific MNE (single nozzle and four nozzles), compared the starting characteristics, operating characteristics, and mixing characteristics based on the experiment and numerical simulation. Results revealed that the interaction between primary total pressure and the diffuser exit pressure played a major role in determining the starting states for the MNE. The four-nozzle ejector required a higher starting pressure than the single-nozzle ejector, due to the shock loss and friction loss, meanwhile, it showed priority when the compression ratio exceeded 8 or the entrainment ratio droped to below 0.068. The non-mixing length of the four-nozzle ejector is shorter than that of the single-nozzle ejector under the same conditions, and there is a linear relationship between the non-mixing length and the entrainment ratio for the single-nozzle ejector.