DIFFUSER Russian patent published in 2017 - IPC F01D25/30 F04D29/44 

FIELD: machine engineering.

SUBSTANCE: diffuser comprises an external bypass 1 made conical, on which inner side there is a ribbing, the main ribs 2 and auxiliary ribs 3. The main ribs 2 are formed by wedge-shaped variable height increasing linearly from zero value in inlet edge area 4 located in the inlet section 5 of the diffuser to a value h₁ in the area of the outlet edge 6 located in the outlet section 7 of the diffuser. The angular installation pitchβ₁ between the main ribs 2 does not exceed 5°. The free edge 8 of the main ribs 2 is parallel to the longitudinal axis O of the diffuser. The auxiliary ribs 3 are installed in the middle between the main ribs 2. The angular installation stage β₂ between the main rib 2 and the auxiliary rib 3 is equal to half of the angle installation pitch β₁. The auxiliary ribs 3 are made with trapezoidal variable height. There are inlet edges 9 of the auxiliary ribs 3 located at distance L₁ from the inlet section 5 of the diffuser is chosen to be equal to the half of the axial diffuser length L. The outlet edges 10 of the auxiliary ribs 3 are arranged in the outlet section 7 of the diffuser. The free edge 11 of the auxiliary ribs 3 is parallel to the longitudinal axis O of the diffuser. The height of the auxiliary ribs 3 is linearly increasing from the value h₂ in the region of their input edge 9 to the value h₃ in the area of their output edge 10. In this case, the value of h₂ is selected equal to half the value of h₁, and the values of h₃ and h₁ are equal and chosen as , where is the Reynolds number, where c₁ - average velocity in the inlet section 5 of the diffuser, ν - coefficient of kinematic viscosity of the moving working medium.

EFFECT: improved reliability of the turbomachine elements by effectively stabilising the flow of wide-angle diffusers with opening angles of the running portion above 12 degrees due to prevention of tear-off zones formation which results in sharp increase of amplitudes of pressure pulsations.

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