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The present work aims at the optimum design and the optimum operating condition of a S-shaped diffuser by studying the effect of inlet velocity, turning angle and area ratio using Computational Fluid Dynamics. Fluent 17.1 software has been used for this simulation work. It is found that the static pressure recovery coefficient (Cp) increases and the total pressure loss coefficient (Cl) decreases as the inlet velocity increases. It is also found that cross-flow velocity becomes more prominent as turning angle increases and the magnitude of in-plane velocity increases with the increase in area ratio. It is further found that flow separation at the bottom wall increases with the increment in area ratio and decreases with the increase in turning angle. Finally, it is found that AR 4 is the optimum area ratio and 75°/75° is the optimum turning angle. [ABSTRACT FROM AUTHOR]

An annular diffuser is a critical component of the turbomachinery, and its prime function is to reduce the flow velocity. The current work is carried to study the effect of four different geometrical designs of an annular diffuser using the ANSYS Fluent. The numerical simulations were carried out to examine the effect of fully developed turbulent swirling and non-swirling flow. The flow behavior of the annular diffuser is analyzed at Reynolds number 2.5 × 105. The simulated results reveal pressure recovery improvement at the casing wall with adequate swirl intensity at the diffuser inlet. Swirl intensity suppresses the flow separation on the casing and moves the flow from the hub wall to the casing wall of the annulus region. The results also show that the Equal Hub and Diverging Casing (EHDC) annular diffuser in comparison to other diffusers has a higher static pressure recovery (Cp = 0.76) and a lower total pressure loss coefficient of (CL = 0.12) at a 17° swirl angle. [ABSTRACT FROM AUTHOR]

In this paper, the effects of non-swirling and swirling flow on the performance of parallel hub axial annular diffuser has been investigated. The study was conducted on a fully developed swirling flow and non-swirling flow to predict the separation of the flow from the wall. Three different annular diffusers were used with casing wall angles of 3°, 6°, and 9°. Furthermore, various swirl angles (0–25°) at the inlet of diffusers have been investigated to analyze the performance across the length. It was found that parallel hub axial annular diffuser performance increases up to a certain length as the inlet swirl angle increases. However, the performance also improves as the diffuser area ratio (AR) increases. The performance is evaluated based on the static pressure recovery coefficient (Cp) and the total pressure loss coefficient (CTL). The highest possible pressure recovery is achieved by the 12° swirl angle with a casing angle of 6°. [ABSTRACT FROM AUTHOR]

In the present work, the parallel hub axial flow annular diffuser's performance characteristics with divergent casing varying between equivalent cone angle (10°, 15°, and 20°) with area ratio 3 have been evaluated computationally as well as experimentally. The performance of three diffusers was tested at different inlet swirl angles (from 0° to 25°) for swirling and nonswirling flow. Simulations have been carried out on a fully developed flow at Reynolds number 2.5×105. The results were analyzed based on the velocity profiles, static pressure recovery coefficient, and the total pressure loss coefficient. The result analysis shows that the inlet swirl flow improves the recovery of pressure and also delays the flow separation on the casing. Moreover, the findings also show that the best performance was achieved in equivalent cone angle 10° at the inlet swirl angle of 7.5° compared to other diffusers. [ABSTRACT FROM AUTHOR]