Research of influence of the installation of perforated plates on the flow in the diffuser ducts with turning of the flow at 90°

Diffuser channels with 90° rotation of the flow are used in a number of technical devices to slow down and turn the flow of the working fluid. Besides slowing down and turning of the flow at the outlet of the channels, it is necessary, as a rule, to possibly provide a uniform field of velocities. However, it is necessary to take into account the requirements for the compactness, which, in some cases, are crucial and lead to the need for nonoptimal channels in terms of aerodynamics, including wide-angle diffusers, which are highly likely to cause the flow breakaway with sharply uneven output velocity field. The results of experimental research method of alignment of the velocity field at the output of the wide-angle flat diffuser channel with 90° rotation of the flow by installing plates with round and square holes and varying degrees of perforation inside of the channel are presented in this paper. The studies were carried out on an open-type wind tunnel changing the dimensionless velocity at the inlet of the diffuser channel section in the range from 0.18 to 0.72. The values of the coefficients of the total energy loss in a channel were determined. Which of the installed perforated plates lead to the lowest increase of the energy loss was established. The optimal location of these plates within the duct was determined. The measurements of the velocity fields at the outlet of the channel were carried out. Simultaneously, the measurements of the pressure pulsations on the side wall at the outlet of the channel were carried out. It was shown that the minimal increase in energy losses due to the installation of plates can substantially equalize the output of the velocity field and reduce the dynamic loads on the walls. The obtained results allow us to recommend this method of aligning the output of the velocity field for real technical devices that require the simultaneous slowdown in the flow and its rotation.