One-dimensional treatments of the flows in high pressure gas ejectors

Hanbury, William T (1968) One-dimensional treatments of the flows in high pressure gas ejectors. PhD thesis, University of Glasgow.

Abstract

Possible methods of describing the flows in constant area ejectors in terms of one-dimensional theories are examined and discussed. Both sonic and supersonic injection are considered, but the analysis is limited to the mixing of two streams of the same perfect gas. Three simple one-dimensional theories describing the primary expansion and a single theory describing the mixing process are presented initially. These theories allow for choking to occur either at the end of the primary expansion or at the end of the mixing duct. Some numerical results comparing the predictions of these theories with each other and experiment are given. The results from an extensive numerical survey of the total solution according to the combined Polytropic Two Stream theory and Straight Mixing theory are also presented, A generalised theory of choking based on small disturbance velocities is put foreward. This theory is applicable to non-uniform flows. It considers choking to be a property of the flow as a whole, rather than a local phenomenon. A parameter B, pertaining to a cross-section of flow as a whole, is defined such that it is positive for "supersonic' negative for "subsonic" and zero for choked flow, A one-dimensional method of describing the mixing process is proposed which, when combined with the general theory of choking, may be used to predict choking within the mixing process. An experimental programme designed to investigate the applicability of the one-dimensional theory and the general phenomenon of choking is described and discussed. A plane flow air-air ejector is used. The full programme is not completed but some initial experimental results are given. It is indicated that the Polytropic Two Stream theory may give reasonably good predictions of the choked flows in ejectors with high total pressure ratios, low total enthalpy ratios and high primary injection Mach numbers. Flows in ejectors of the opposite characteristics are liable to become choked within the mixing process and thus may not be predicted by any of the simple one-dimensional theories. The Straight Mixing theory is found only to be of limited use in that flows are not usually found to be completely mixed by the end of the duct. An alternative theory is suggested.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: T RF Nonwieler
• Keywords: Mechanical engineering, Fluid mechanics
• Date of Award: 1968
• Depositing User: Enlighten Team
• Unique ID: glathesis:1968-72814
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 11 Jun 2019 11:06
• URI: https://theses.gla.ac.uk/id/eprint/72814