SU1765743A1 - Stand for wind tunnel test of turbomachine blade - Google Patents

Abstract

Use: for gas-dynamic studies of elements of turbomachines, in particular their ring and sector grids. The essence of the invention: providing a maximum approximation of the radial pressure gradient at the output of the lattice to full-scale values with minimal distortion of the flow structure in the measurement cross section (which increases the reliability of the test results). The bench contains a gas supplying annular nozzle, an annular body for accommodating an annular or sector blade grille, and a gas evacuating annular nozzle. New in the design is the construction of a diaphragm placed in the gas outlet pipe with the formation of the last ledge with the wall in order to maximally approximate the radial pressure gradient at the outlet of the lattice to full-scale values with minimal distortion of the flow structure. 4 il. sl C

Description

The invention relates to experimental equipment for gas-dynamic studies of elements of turbomachines, in particular, to stands for blowing their annular and sector grids.

There are known stands for purging ring grids containing a feed channel, a housing for accommodating the grid under test, and a discharge channel with a device for creating a radial pressure gradient at the exit of the grid, made, for example, in the form of an annular disk with slots of variable through blade height. abilities, either in the form of a grid of radial pins, etc. 1

The disadvantage of this design is the occurrence of transients in front of the fixed elements of the specified device in transonic modes of operation, which significantly distorts the flow field behind the ring grating.

Also known is a stand for purging turbomachine blade grids, comprising a feed channel, a housing for accommodating the test grid, and a discharge channel with a resistance of 2 located therein.

The disadvantage of this design is also the emergence of a system of jumps on the input edges of the spacing vanes in Azad 0.9-1 modes. In addition, it is possible to reflect the edge shocks appearing behind the grating under study from the surface of the spinning blades back into the flow. This distorts the structure of the flow behind the grate and significantly increases the measurement error. Finally, a similar device can provide close to us

00

radial pressure gradient in only one mode (for which it was designed). When changing the mode of operation of this grid (and even more so when examining another grid), the device does not provide the required radial gradient at the output.

The aim of the invention is to provide a full-scale radial pressure gradient at the outlet of the annular (sector) lattice with minimal distortion of the flow structure in the cross section of measurements.

The goal is achieved by the fact that the stand for blowing turbomachine blade grids contains an annular body in which a blade grille is installed, connected at the inlet and at the outlet respectively to the gas supply and flue gas pipes and the diaphragm placed in the flue gas pipe forming the last the ledge, in order to maximally approximate the radial pressure gradient at the exit of the lattice to full-scale values with minimal distortion of the flow structure, the diaphragm is made annular and reinforced a pipe wall with the possibility of radial movement and the ratio of the distance from the output to the cutoff blade lattice aperture of the lattice to step is 0.5-2.0.

Figure 1 shows a longitudinal section of the stand; figure 2 shows a view of the stand from the exhaust side (view A in figure 1); on fig.Z and 4 shows the results obtained using the proposed device.

The stand contains a gas supplying annular pipe 1, an annular body 2 for accommodating the test annular or sector grille 3 and a gas evacuating circular pipe 4 with a diaphragm 5 in it, which forms a ledge with the wall of the latter, in order to maximize the outlet radial pressure gradient grids to full-scale values with minimal distortion of the flow structure. The diaphragm 5 is annular and fixed in the wall of the nozzle with the possibility of radial movement, and the ratio of the distance from the exit slice of the scapular grille to the diaphragm 5 to the grille pitch is 0.5-2.0.

When testing the ring (sector) lattice 3 to create the required radial pressure gradient at the outlet with the help of diaphragm 5, an annular step is formed at the outer diameter of the gas exhaust channel 4. In the flow, due to the curvature of the current lines to

A radial pressure gradient arises in the sleeve. By changing the depth of immersion of the elements of the diaphragm 5 into the flow part (the height of the step (5), any given pressure gradient can be obtained.

Wrapping an annular ledge at an angle of / fe 15-30 ° to the circumferential direction, even in supersonic modes of operation, does not lead to additional compaction surges in the flow. Since the height of the ledge does not exceed a few millimeters, it practically does not affect the shape and intensity of the outer edges.

jumps behind the shoulder blades and does not lead to their reflection. All this contributes to the preservation of the regular flow structure behind the grating, which is close to full-scale under the conditions of the turbine stage.

The device allows you to easily set an arbitrary (required) radial gradient of the static pressure at the outlet depending on the lattice and the mode of its operation during the experiment. Measurements of gas-dynamic parameters and gas-dynamic efficiency in this case will be accompanied by a minimum error. The presence of a smooth sleeve significant axial extension ()

contributes to a continuous flow on the inside diameter behind the grille.

Fig. 3 illustrates, as an illustration, the ratio of averaged pressures at the periphery and at the P2nar / P2w sleeve, depending on the superficial velocity behind the ring grating on the average diameter Azadsr at different heights of the protrusion 5 on the outer diameter of the discharge channel. It is seen that with an increase of 6 radial pressure gradient

growing fast. Figure 4 shows the static pressure distribution over the height of the blades on the Yazadr modes -1.1 and 1.15 with the height of the protrusion g 3 mm.

45

Claims (1)

Invention Formula A bench for purging turbomachine blade grids, comprising a housing with a blade grid connected to inlet and outlet respectively to the gas supplying and gas exhausting annular branch pipes, and the diaphragm placed in the latter with the formation of a step with the wall of the branch pipe, characterized in that In order to maximally approximate the radial pressure gradient at the exit of the lattice to the full-scale one with minimal distortion of the flow structure, the diaphragm is made annular and fixed in the wall a nozzle with the possibility of radially cutting the blades to the diaphragm to the displacement step, and the ratio of the distance from the grate is 0.5-2.0. 1 Rnar Ot9 1.0 1.1 1.2 1.3 FIG. J FIG. 2 ABOUT W 0, b8 0.52 FIG. four