A detailed experimental investigation has been undertaken into the isothermal flow field within a modern gas turbine annular combustor. In this paper data is presented which demonstrates the strong coupling that exists between the flow conditions within each feed annulus, that surround the flame tube, and the jets formed within the flame tube by the primary and secondary ports. The initial pitch angle of the jets, port discharge coefficient and the jets axial and radial momentum were influenced by well known bulk property variations, but also by less well known local conditions feeding the port. Furthermore, this strong coupling meant that differences were apparent in the initial conditions of each jet due to local variations in the feed annulus velocity profile. In most cases these differences, between opposing jets, affected the location of their impingement point and the fluid trajectory after impingement. However, for the primary jets in line with the fuel injector a dramatically increased sensitivity to feed conditions was displayed, caused by the low pressure associated with the swirling injector flow. This caused the jets to be deflected in opposite directions with no impingement. Numerical predictions were also used to demonstrate the coupling between the jets and the internal pressure field within the flame tube. Furthermore, the experimental data has implications as to how, in general, such numerical predictions should be conducted if the interactions between the flame tubes external and internal flow fields are to be accurately captured.

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