SU466347A1 - Streamlined surface " - Google Patents

Description

There are known devices for the diffusion of a diffuser with a positive pressure gradient, in which there is a slowing down of the flow rate, an increase in pressure and the associated flow separation from the wall. As the degree of expansion increases, the angle of the diffuser increases the thickness of the boundary layer, the notes are displaced from the solid surface farther and farther to the center, the irregularity of the flow velocity over the cross section increases, the flow begins to move in the opposite direction at the wall, the losses increase dramatically.

The purpose of the invention is to eliminate the phenomenon associated with flow separation, and a sharp decrease in friction and expansion notions.

This is achieved by the fact that in the proposed streamlined surface, the main dimensions of the expansion stage - alignment of the notok are as follows: the opening angle of the expansion section 7 is 30-15 °, the ratio of the larger diameter to the small one is no more than 1.25, the length of the cylindrical alignment section is 1-1.5. diameter.

The drawing shows the proposed streamlined surface. A.D. Altshul determined the length of the influence of local resistance

for pipes like, 5 D (-

   ,

where L is the length of the flow stabilization section; D is the diameter of the pipe;

c is the coefficient of local resistance; l - coefficient of pipe resistance for

local resistance. The smaller the value of local resistance, the shorter the length of the stabilization section. If now, not the income to the separation point, to place a cylindrical section in the diffuser to eliminate the influence of the previous section, then you can again have an expansion section, etc.

In the drawing, the arrow shows the direction of flow, the letters K indicate the flow expansion areas, and the letters C indicate the cylindrical sections with indices increasing towards the flow direction. The walls of the diffuser are shaded. If the KiUi section is considered as an expansion stage, then the diffuser should be considered as a multi-stage one.

For a round diffuser with backpressure, working on water, the ratio of large diameter to small should be no more than 1.25, the angle of the expansion section of the diffuser should be about 7 ° 30, and the length of the cylindrical section should be within 1-1.5 diameters the cylindrical section of the step and determine according to the formula A.D. Altshul depending on the magnitude of the expansion loss and loss factor

on friction.

Subject invention

A streamlined surface of a solid for gas or liquid, made in the form of a series of expansion stages - leveling the flow, characterized in that, in order to eliminate the effects associated with separation of the flow and drastically reduce losses

friction and expansion, the main dimensions of the expansion stage - flow equalization are as follows: the opening angle of the expansion section is 7 ° 30-15 °, the ratio of large diameter to small diameter is not more than 1.25, the length of the cylindrical leveling section 1 is 1.5 of its diameter.