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°.
The Russian park of power steam turbines contains a large number of turbines with adjustable steam extraction from the flow path where rotary control diaphragms are used as flow controllers, which structurally easily fit into the flow path of these turbines. This method of regulating the steam flow rate is accompanied by a decrease in the efficiency of the subsequent stages of the turbine and causes the appearance, at reduced loads, of additional disturbing forces acting on the rotor blades. In the presented materials, a variant of a post-sampling stage with a radial rotary control diaphragm is considered. The performed mathematical modeling of the working fluid flows in such a stage showed that in this case, at all turbine loads, a relatively uniform velocity field is provided when steam enters the nozzle apparatus, which naturally entails the elimination of the noted drawbacks.
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