Compressible swirling flow through convergent-divergent nozzles

Abstract

The effects of swirl on the rate of mass flow and on the velocity field in the throat region of axi-symmetric nozzles are studied analytically and experimentally, tn the analytical phase, methods are developed for treating either the direct or the inverse problem for flow in de Laval and annular nozzles, taking account of either weak or strong swirl. The experiments were performed in an annular nozzle, with swirl being imparted to the flow by adjustable vanes situated upstream of the test section.The analytical results facilitated an examination of the effects of swirl strength, distribution of swirl, and nozzle geometry. The rate of mass flow was found to decrease with increasing swirl strength. The mass flow results were well correlated by a swirl strength parameter evaluated at the throat, with swirl type and geometry being of secondary importance. Another effect of swirl was to shift the sonic line upstream of the geometric nozzle throat. The experimentally determined mass flow results were in agreement with the analytical predictions. Also, all of the qualitative characteristics of the local flow field measurements were reproduced by the analytical results. Nomendamre

Computational Fluid Dynamics Study for Flow of Natural Gas through High-pressure Supersonic Nozzles: Part 2. Nozzle Geometry and Vorticity

“…Radial velocity w vanishes at the axis of symmetry .r D 0/; while the flow is parallel to the nozzle wall at .r D R/: Before proceeding to the results, it is relevant to select a parameter to characterize the swirl strength. The matter of the swirl parameter was first discussed by Boerner (1970). Although there does not appear to be any Downloaded by [Gazi University] at 00:50 03 January 2015 compelling logic favoring the choice of any one parameter, there is reason to believe that the tangential velocity v should be involved via an integral.…”

“…For isentropic flow of a perfect gas, it is known that the critical speed a*, the sound velocity a, and the velocity components u, v, and, w are related by the following equation (Boerner, 1970):…”

“…Although there does not appear to be any Downloaded by [Gazi University] at 00:50 03 January 2015 compelling logic favoring the choice of any one parameter, there is reason to believe that the tangential velocity v should be involved via an integral. The swirl parameter S is chosen as the area-average of v at the throat (Boerner et al, 1972), that is:…”

“…Boerner (1970) and Boerner et al (1972) studied the vorticity effects for an ideal gas in a supersonic nozzle. The vortex effect can significantly increase the energy loss when the gas passes through the nozzle.…”

Supersonic gas separators: Review of latest developments

“…It is further proposed that the elimination of swirls is a significant achievement, as it reduces pressure head losses due to swirl generation and dissipation, providing unparalleled design simplicity and flexibility due to lack of need for an inner body or restriction to a circular or annular cross section, taking advantage of a purely axial flow inside the nozzle which prevents much turbulence and flow separation, and reducing the liquid film and gas shear force by limiting the slip to the axial direction. 3 is mislabelled on the vertical axis) and compared with Beoner's data [23]. While this brings a certain level of validity to the models, a validation of the results using absolute field data (as opposed to dimensionless ratio) is normally used when a highly compressible fluid is considered.…”