City Research Online

Abstract

A research programme was conducted to investigate extensively the effect of "solid- body" and Rankine vortex swirl addition on the performance of conical diffusers.
An extensive survey of available literature on theoretical and experimental work has been presented with particular emphasis on areas not covered by previous surveys. Criteria used for defining performance have been reviewed and extended to swirling flow cases. Some degree of ambiguity exists in the estimation of performance; thus experimental results were assessed against all the theoretical models to seek a trend.
Flow visualization studies have indicated that both types of swirl improve the diffusion process of the 10°, 20° and 30° diffusers. The degree of improvement depends on double conical angle and degree of swirl induced.
The experimental analyses have indicated that solid-body swirl modifies the pressure drop in the inlet pipe, improves the diffusion process, eliminates separation tendencies completely or partly, improves the diffuser performance and there is a prospect of further improvement with higher swirl severity.
The characteristics of the free vortex generator showed that the optimum influence of Rankine vortex swirl on diffuser performance was obtained when the number of blades was 8 and the blade angle of the generator was 6º, 10° and 10° for the 10°, 20° and 30° diffusers respectively. The flow in the diffusers deteriorated when the blade angle was increased above its appropriate optimum angle. The experimental analysis indicated that optimum Rankine vortex swirl eliminates the separation tendencies completely or partly, improves the diffusion process, modifies the pressure drop in the inlet pipe, improves the diffusers’ performance and for the 20° and 30° diffusers, the axial velocity at the centre of the vortex was found to be low and the solid-body core of the Rankine vortex approximately coincided with the displacement area of axial velocity to the centre.
Application of experimental data to theoretical analysis showed that for 10° and 20° diffusers, optimum Rankine vortex swirl was seen to be best whereas for the 30° diffuser, best improvement resulted from solid-body swirl 3.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses

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