Abstract
It is shown theoretically that the efficiency of wide-angle diffusers mainly depends on the method of supplying the working medium to the diffuser channel and on the nature of the interaction of this medium with the subsequent streamlined surface of the diffuser. The first condition is due to those changes in the acting force factors within the wall (boundary layer), which occur during the transition from the inlet confuser channel to the subsequent diffuser, and the second follows from the need to ensure an uninterrupted flow of the working medium moving against the increasing (in the direction of travel) static pressure. The above computational studies of wide-angle diffusers have shown that, subject to theoretically justified conditions, it is possible to ensure uninterrupted flow in flat and conical diffusers with an increase in the opening angle α of their flow path to 20° and with the same degrees of expansion ration to obtain pressure recovery coefficients commensurate with those in diffusers with an angle α = 7°.
Highlights
Conical and annular diffusers with a straight axis are structurally the simplest, but very effective, devices that convert the kinetic energy of moving liquid and gaseous media into potential energy, determined by the value of static pressure in these media.the final effect of such energy conversion depends on a number of additional factors, among which, naturally, the first place is occupied by the geometric parameters of the diffusers
The first condition is due to those changes in the acting force factors within the wall, which occur during the transition from the inlet confuser channel to the subsequent diffuser, and the second follows from the need to ensure an uninterrupted flow of the working medium moving against the increasing static pressure
As a result of the analysis, the deformation of the velocity profile during the supply of working media to the inlet section of the diffuser showed that this deformation primarily limits the opening angles of the flow paths of flat and conical diffusers, exceeding which causes a local separation of the flow immediately behind the inlet section
Summary
Conical and annular diffusers with a straight axis are structurally the simplest, but very effective, devices that convert the kinetic energy of moving liquid and gaseous media into potential energy, determined by the value of static pressure in these media. At the inlet section of the diffuser, the nature of the change in the longitudinal velocity near the streamlined surface, as shown in Fig. 3 turns out to be significantly different from the average flow rate. 4 shows a diagram of a setup for studying diffusers, where pressure oscillograms were taken in a flat diffuser with an opening angle α = 15 ° along its longitudinal axis using lowinertia pressure sensors [2]
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