SU1726851A1 - Intermediate stage of centrifugal compressor - Google Patents

Abstract

The invention allows to increase the efficiency of the compressor. The intermediate stage of the centrifugal compressor contains an impeller 1, a diffuser (D) 2, a diffuser-confused channel (DCC) 3 and a return guide device (OHA) 4, sequentially located in the housing along the working medium flow. ВД 2, ДКК 3 and ОНА 4 perpendicular to the casing walls, blades 5–7 are installed, respectively. Blades D 2 are made curved, and in DCC 3 and L 7 SHE 4 are made flat. The blade setting angle L 6 DCC is equal to the exit angle of the blade L 5 D 2. The blade profile L 5 D 2 has the shape of a half loop of a lemniscate, facing convexity in the direction of rotation of the impeller 1. The node point of the lemniscate is located on the outer diameter D 2. The exit angle of the profile is 90 ° The blades L 76 DCC 3 are made in one piece with the blade L 5 D 2, and the blades L 7 OHA 4 are made radial. Each blade L 7 OHE can be integral with blade 6 of DCC 3. A 2, DCC 3 and OHA 4 can be equipped with additional blades installed in the housing between the main blades 5-7, with the input edge of the additional blades located between the inlet and the outlet from D 2, and the exit edge is between the inlet and outlet from the EAG 4.2 zp. f-ly, 6 ill. THX

Description

This invention relates to centrifugal compressor engineering. namely, the intermediate stages of compression of a multistage centrifugal compressor.

A centrifugal compressor stage is known, which comprises a blade diffuser mounted behind the impeller, in which the blades have a curved shape and with their convexity in the direction of rotation of the wheel, and the exit angle of the diffuser blades is substantially less than 90 °.

The disadvantage of this stage is the complex, spatial nature of the flow movement, which has a circumferential, radial and axial velocity components, at the exit of the diffuser and in the diffuser-confused channel. The flow in this stage moves in a spiral turn, which causes an increased flow path along the curved blades of the diffuser, in the diffuser-confused channel and along the blades of the return guide vane. As a result, increased eddy losses and friction losses occur and, consequently, the efficiency of the stage decreases.

A known intermediate stage of a centrifugal compressor, comprising an impeller, a diffuser, a diffuser-confused channel and a return guide vane, successively located in the housing along the flow of the working medium, equipped with blades installed perpendicular to the walls of the housing, the diffuser blades being curved, the diffuser-confusor blades the channel and the return guide vane are flat, and the installation angle of the vanes of the diffuser-confused channel is equal to the exit angle of the vanes of the diffuser.

The disadvantage of this stage is an increase in the length of the paths of flow in the stage, due to the fact that the convexity of the diffuser blade is formed by the radii of the circle and facing the direction of rotation of the impeller. In addition, the step does not provide a radial exit of the diffuser blade into the diffuser-confused channel. As a result, the unwinding of the flow from the circumferential to the radial direction in the diffuser and in the diffuser-confused channel does not end. Therefore, the flow leaves the diffuser section of the diffuser channel with residual swirling and moves in a reverse guide apparatus, having a circumferential velocity component.

The increased flow path in the step increases friction losses, and the circumference component at the exit from the diffuser forms in the diffuse-confused channel and in the return guide apparatus a circumferential and radial unevenness of the angles of exit from the step and the entrance of the stream to the impeller

the next stage, increasing the vortex and impact losses.

All this significantly reduces the efficiency of the stage.

The purpose of the invention is to increase efficiency

0 steps.

The goal is achieved by the fact that the profile of the blade of the diffuser has the form of a half-loop of a lemniscate, convex in the direction of rotation of the working

5 wheels, while the knot point of the lemniscate is located on the outer diameter of the diffuser, the exit angle of the profile is 90 °, the vanes of the diffuser-confused canal are integral with the vanes of the diffuser, and the blades of the reverse guide vane are installed radially.

Each paddle of the return guide vane is integral with the paddle of the diffuser confused channel.

The diffuser, the diffuser-confuser channel and the return guide device are equipped with additional blades installed in the housing between the main blades, the input edge of the additional blades located between the entrance and exit of the diffuser, and the output edge between the entrance and exit of the reverse guide apparatus.

5 Fig, 1 shows a fragment of the proposed stage, a longitudinal section; figure 2 - section aa in figure 1; Fig. 3 shows a step with blades of a reverse guiding apparatus, made in one piece with the blades of the diffuser-confused channel and with additional blades, a longitudinal section; Fig. 4 is a section B-B in Fig. 3; an embodiment with blades of a reverse guide vane made in one piece with

5 vanes diffuser confused channel; Fig. 5 shows a section B-B in Fig. 3, an embodiment with additional blades; figure 6 is a graphical determination of the parameters of the lemniscate forming the scapula

0 diffuser.

The centrifugal compressor stage contains an impeller 1, a diffuser 2, a diffuser 5 confusing channel 3 and a return guide device 4, successively located in the housing along the flow of the working medium. In the diffuser 2, diffuser-confusing channel 3 and the return guide device 4, blades 5 are installed -7, located perpendicularly to the confining walls of the diffuser, the diffuser-confused channel and the return guide. The vanes 5 of the diffuser 2 are curved (Figs. 2-5), and the vanes 6 of the diffuser-confuser channel 3 and the vanes 7 of the return guide vane 4 are flat (Figures 4 and 5). The installation angle of the blades 6 of the diffuser-confused channel 3 is equal to the angle u (Fig. 2) of the exit of the blades 5 of the diffuser 2. The profile of each of the blades 5 of the diffuser 2 has the shape of a half-loop part of the lemniscate 8 (Fig. 6), turned by its bulge in the direction of rotation w of the worker wheels 1.

The nodal point d of lemniscate 8 is located on the diameter D4 of the exit of the blades 5 (FIG. 2) of the diffuser 2. The exit angle OD of the profile of the blades 5 of the diffuser 2 is 90 °. The vanes b (Figs. 1-5) of the diffuser-confused channel 3 are made in one piece with the vanes 5 of the diffuser 2, and the vanes 7 of the reverse guide vane 4 are radial.

Each blade 7 of the return guide vane can be one whole (Figure 4) with the blade 6 of the diffuser-confuser channel 3.

The diffuser 2, the diffuser-confused channel 3 and the return guide vane 4 can be equipped with additional blades 9 (Fig. 3, 5) installed in the housing between the main blades 5-7, with the input edge of the additional blades 9 located on the diameter 0П1 between the entrance Oz and the DA output from the diffuser 2, and the output edge on the diameter 0П2 between the input OB 04 and the output De from the reverse guide vanes 4.

The impeller 10 (Fig. 1, 5) of the following stage 11 is installed after the return guide vane 4.

During operation of the centrifugal compressor, the gas after the impeller 1 moves along the trajectory kk (Fig. 4) along the surfaces of the blades 5 of the diffuser 2 and exits the latter into the diffuser confusing channel 3 at an angle equal to the angle QA of the output of the blades 5 of the diffuser 2. Since the angle is OA 90 °, the flow enters the diffuser-confused channel 3 radially and moves in the latter along flat blades 6, made in one piece with the blades 5 of diffuser 2. Then the flow, having a radial direction, enters the return guide device 4 and moves along the surfaces p Adially mounted blades 7. And after exiting the reverse guide vane 4, it enters the entrance of the impeller 10 of the next stage 11.

The formation of the profile of the blade 5 of the diffuser 2 half-leaf lemniscate 8, facing its bulge in the direction of rotation of the impeller 1

1.5-2 times reduces the flow path of the working medium in the diffuser 2 and in the diffuser-confusion channel 3 and, thanks to the properties of the lemniscate curve, makes the curvature 5 of the diffuser 5 change

2 from the diameter Oz entrance to the diameter DA output. As a result, friction losses are reduced and smooth flow movement in the diffuser 2 is ensured without tearing off and vortex formation.

reduction of vortex losses significantly increases the efficiency of the stage.

Due to the fact that the vanes 5 of the diffuser 2 have an exit angle equal to OQ 90 °, and the vanes 6 of the diffuser-confused channel 3 are integral with the vanes 5 of the diffuser 2, the flow along the surfaces of the blades 6 of the diffuser-confused channel 3 is significantly stabilized due to further

in the course of the flow, the intensity of breaks and vortex formation in diffusive-confused channel 3 decreases. This further increases the efficiency of the stage.

In addition, education is excluded.

oblique cut between the shoulder blades 6 at the exit of the dkfuzorno-confused channel 3, which increases the effective length of the diffuser 2 and further increases the efficiency of the stage. Due to the fact that the blades 7 of the reverse guide vane 4 are installed radially, the aerodynamic conditions for supplying flow to the impeller 10 of the next stage 11 are improved. This reduces the vortex and impact losses at the entrance to

wheel 10 and increases the efficiency of the next stage. In addition, friction losses are reduced, since the length of the blades 7 of the return guide vane 4 due to their radial position decreases in

1.15-1.25 times. It also increases the efficiency of the stage. Installing additional blades 9 between the main blades of the 5-7 step allows to optimize the diffusivity of the channels between the blades of the step and thereby further improve the efficiency of the proposed step by improving the hydraulic characteristics of the diffuser 2, the diffuser-confuser channel 3 and the reverse guide

apparatus 4.

The design of the proposed stage is performed as follows.

From the calculation of the step, the diameter of the entrance Oz and the diameter of the exit 04 of the diffuser 2 are obtained.

The SI node point (Fig. 6) is assigned lemiskates 8 on diameter D4 and the axis X is restored from point Oi at an angle of 45 ° to the axis Y of wheel 1 in the radial plane passing through the node Oi. On the X axis, using a well-known method, build a Lemniscate 8 with a focal distance C OiF equal to

WITH

D4-Oz

Calculations show that with the radial extent of the diffuser 2 taken in the centrifugal compressor building area equal to

 “Oh 202

where D2 is the diameter of the impeller 1, is tangent aa to the half-eye of OchoAoz (Fig.6) of lemniscate 8, having dimensionless

WITH

the focal length, forming a tangent b-b to the diameter Oz of the entrance of the diffuser 2 at the point Oa of intersection with the lemniscate 8, makes an angle of 30–32 °. This value of the angle "with no-substance is above the limiting values of the angle" with the installation of the blade 5 of the diffuser 2 at the entrance. Therefore, the acceptance of C 1 is justified, since the optimum angle of installation of the blade 2 at the entrance to the diffuser 2 is in the range O C 1.

After the construction of the lemniscate 8, the radius-vector / eot of the nodal point From to the point 02 of the intersection of Lemniscate 8 with the diameter Oz of the entrance of the diffuser 2 and the angle p between the X axis and the radius vector p are measured.

Next, based on the properties of the lemniscate, build the tangent aa to lemniscate 8 at point 02 and graphically find the angle az between the tangent b-b in diameter Oz at point 02 and the tangent a-a. If the ccr angle turns out to be larger than the calculated angle of installation of the software 5 of the path 5 of the diffuser 2, the focal distance C should be reduced and the construction should be repeated. If the angle "si is less than the calculated angle" sp. focal distance. With the increase and repeat the construction. After several constructions, a graphical dependence of f (C) is obtained, but for which, for a given degree of incidence angle, the required focal distance C is found. Lemniscates 10. The required focal distance C can also be determined using known computational methods.

FORUMAWLAH AND ISLANDS

Claims (3)

1. An intermediate stage of a centrifugal compressor, comprising an impeller, a diffuser, a diffuser-confused channel and a return guide vane, successively located in the housing along the working medium flow, equipped with blades installed perpendicular to the walls of the housing, and the diffuser blades are curved, and the blades of the diffuser-confused channel and the return guide vanes are made flat, the angle of the blades of the diffuser-confused channel is equal to the exit angle of the diffuser blades, which is so that, in order to increase the efficiency of the stage, the profile of the diffuser blade is in the shape of a semi-loop lemniscate, reversed convexity in the direction of rotation of the impeller, while the knot point of the lemniscate is located on the outer diameter of the diffuser, the exit angle of the profile is 90 °, the blades of the diffuser-confused channel are made in one piece with diffusers, and blades reverse guide vanes are radial. 2. A step according to claim 1, characterized in that each blade of the return guide vane is integral with spatula diffuser-confused channel. 3. Step according to claims 1 and 2, characterized in that the diffuser, the diffuser-confused channel and the reverse guide the apparatus is equipped with additional blades installed in the housing between the blades, with the input edge of the additional blades located between the inlet and outlet of the diffuser, and the output the edge is between the entrance and the exit of the return guide vanes. Fy