The compound-choking theory as an explanation of the entrainment limitation in supersonic ejectors
(2018) Energy — Vol. 158, p. 524-536 (2018)
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- Abstract
- While the limitation of the entrainment ratio in supersonic ejectors is a well-known phenomenon, there is still a need to gain insight on the choking phenomena at play in on-design operation. In state-of-the-art simplified models of supersonic ejectors, the secondary stream is assumed to reach sonic velocity in a hypothetical throat (Fabri-choking). However, an alternative explanation of the entrainment limitation known as the compound-choking theory states that a nozzle flow with two streams at different stagnation pressures may be choked with a subsonic stream if the other one is supersonic. In this paper, the compound-choking is highlighted in a supersonic ejector through a thorough analysis of numerical simulations validated against experimental data. In addition, comprehensive experimental data of supersonic ejectors are used to assess the performance of the compound-choking theory to predict the entrainment ratio in the on-design regime in various configurations. Most predictions are in the ±10% range when compared to the experimental data. Compared to state-of-the-art 1D models relying on the Fabri-choking assumption, the compound-choking theory is shown to generally perform better regarding the prediction of the on-design entrainment ratio. This study suggests that the compound-choking theory is well suited to model the choking process in supersonic ejectors.
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Citations
Lamberts, O., Chatelain, P., Bourgeois, N., & Bartosiewicz, Y. (2018). The compound-choking theory as an explanation of the entrainment limitation in supersonic ejectors. Energy, 158, 524-536. https://doi.org/10.1016/j.energy.2018.06.036 (Original work published 2018)