Diffuser (thermodynamics)

About: Diffuser (thermodynamics) is a research topic. Over the lifetime, 6731 publications have been published within this topic receiving 54738 citations.

Effect of J-Groove on the Suppression of Swirl Flow in a Conical Diffuser

Abstract: The purpose of this study is to examine the validity of J-grooves in controlling and suppressing the swirl flow in a conical diffuser, for draft surge suppression in a Francis turbine, which is caused by the swirl flow from the runner outlet into the draft tube. "J-groove" composed of shallow grooves and mounted parallel to the pressure gradient on the diffuser wall is a very simple passive device to suppress several abnormal phenomena in turbomachinery. The experimental study has been performed using the conical diffuser with a divergent angle of 20 deg. The measured results of the velocity distribution in the diffuser show that a considerable reduction in the swirl intensity is attained by using J-grooves. Besides, the amplitude of pressure fluctuation caused by the rotation of the vortex core around the dead water region near the diffuser inlet is reduced by J-grooves.

Numerical Simulation and Flow Analysis of an Elbow Diffuser

Abstract: Numerical simulation of the unsteady turbulent flow in a three-dimensional elbow diffuser is performed. The investigation is carried out with a commercial finite volume solver implementing the Reynolds averaged Navier-Stokes equations. Against the background of current research in DNS and LES, the modeling of most practically relevant turbulent flows continues to be based on this system of equations. For this reason it is important to evaluate the limitations of the Reynolds averaging approach with the associated turbulence modeling, in particular for the prediction of time-dependent flows. Verification and validation are presented; detailed measurements are compared with computations. While a great deal of research has focused on draft tube design, relatively little is known about the complex flow features present. The flow is analyzed over a wide range of operating conditions including part load. Topological changes in the flow patterns with the global characteristics of the diffuser are presented. Visualization provides extra insight into the complex flow. Forced and self-sustained time-dependent flow phenomena are captured. Falling into these categories are flow field fluctuations introduced by the runner, self-sustained vortex shedding phenomena, and the typical rotating helical vortex observed at part load. Additionally, the linear stability of measured inlet profiles is investigated, providing a fuller understanding of the basic instability mechanism.

Variable pipe diffuser for centrifugal compressor

Abstract: A variable pipe diffuser (14) is disclosed for use in a centrifugal compressor (10). The variable pipe diffuser (14) includes an outer ring (42) and an inner ring (40) which is rotatable circumferentially within the outer ring (42) between a first, open position and a second, closed position. In an open position, complementary air channel sections of the inner and outer rings (40,42) are aligned with one another to allow a maximum flow of refrigerant through the diffuser (14). In a closed position, the flow channels (44,46) of the ring sections are misaligned and the flow of refrigerant through the diffuser is restricted. By adjusting the diffuser rings toward a closed position, surge conditions can be avoided even in the case where a high compressor pressure ratio is required.