Diffuser (thermodynamics)

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

System for coupling flow from a centrifugal compressor to an axial combustor for gas turbines

Abstract: A system is provided for aerodynamically coupling air flow from a centrifugal compressor (200) to an axial combustor (202). The system includes a diffuser (204), a deswirl assembly (206), combustor inner and outer annular liners (226, 228), a combustor dome (230), and a curved annular plate (244). The diffuser (204) has an inlet (214) that communicates with the centrifugal compressor (200), an outlet (216), and a flow path (218) that extends radially outward. The deswirl assembly (206) has an inlet (220) that communicates with the diffuser outlet (216) to receive air flowing in a radially outward direction, an outlet (222), and a flow path (224) configured to redirect the air in a radially inward and axial direction through the deswirl assembly outlet (222) at an angle toward a longitudinal axis (207). The curved annular plate (244) is coupled to combustor inner and outer annular liner upstream ends (234, 238) to form a combustor subplenum (241) therebetween and has a first opening (250) and a second opening (252) formed therein, the first opening (250) aligned with the deswirl assembly outlet (222) to receive air discharged therefrom.

Cavitation Surge in a Small Model Test Facility Simulating a Hydraulic Power Plant

Abstract: Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rate, both with and without a surge tank placed just upstream of the inlet volute. The surge frequency at smaller flow rate was much smaller than the swirl mode frequency caused by the whirl of vortex rope. An unsteady CFD was carried out with two boundary conditions: (1) the flow rate is fixed to be constant at the volute inlet, (2) the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.

Guide tube flow diffuser

Abstract: Nuclear reactor upper internal guide tube having a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

Experimental and Computational Study of Hybrid Diffusers for Gas Turbine Combustors

Abstract: The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the pre-diffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This paper will report on one such unconventional diffuser; the hybrid diffuser which, under the action of bleed, has been shown to achieve high rates of diffusion in relatively short lengths. However, previous studies have not been conducted under representative conditions and have failed to provide a complete description of the relevant flow mechanisms making optimization difficult. Utilizing an isothermal representation of a modern gas turbine combustor an experimental investigation was undertaken to study the performance of a hybrid diffuser compared to that of a conventional, single-passage, dump diffuser system. The hybrid diffuser achieved a 53% increase in area ratio within the same axial length generating a 13% increase in the pre-diffuser static pressure recovery coefficient which, in turn, produced a 25% reduction in the combustor feed annulus total pressure loss coefficient. A computational investigation was also undertaken in order to investigate the governing flow mechanisms. A detailed examination of the flow field, including an analysis of the terms within the momentum equation, demonstrated that the controlling flow mechanisms were not simply a boundary layer bleed but involve a more complex interaction between the accelerating bleed flow and the diffusing mainstream flow. A greater understanding of these mechanisms enabled a more practical design of hybrid diffuser to be developed that not only simplified the geometry but also improved the quality of the bleed air making it more attractive for use in component cooling.