A NUMERICAL STUDY ON THE PERFORMANCE OF A SUDDEN EXPANSION WITH MULTISTEPS AS A DIFFUSER

Abstract

In this paper, the numerical analysis and performance simulation of a sudden expansion with multisteps viewed as a diffuser have been carried out. The two-dimensional steady differential equations for conservation of mass and momentum have been solved using the SIMPLE algorithm. The Reynolds number is in the range of 20 to 100. In this study, the configurations of plain sudden expansion and sudden expansion with two, three, four and five steps have been considered. An aspect ratio of 2 is fixed for all the computations. The effect of Reynolds number and number of steps on average static pressure, diffuser effectiveness, distance of maximum static pressure rise from throat and average stagnation pressure have been studied in detail. From the study, it is revealed that sudden expansion with multisteps always offers benefits in any Reynolds number (20–100) at aspect ratio of 2 with respect to a plain sudden expansion as far as its effectiveness and stagnation pressure drop are concerned. At lower Reynolds number, effectiveness of the sudden expansion with multisteps offers substantial benefit without much benefit in its performance at higher flow Reynolds number. The effective length of diffuser increases with Reynolds number, while, increase in number of steps does not have much impact on effective length at a particular value of flow Reynolds number.