CN205559366U - Centrifugal compressor's diffuser - Google Patents

Abstract

The utility model discloses a centrifugal compressor's diffuser. Improve the structure of diffuser, further improve its working property and have important using value. The utility model discloses arrange the short blade of a slice in the runner of two adjacent linear leafs, the leading edge of linear leaf is curved surface and slope setting, and the leading edge line is 6~8 with rim plate the central axis's contained angle, the leading edge curvature radius of linear leaf is crescent along rim plate to wheel cap direction, the three zigzag shaped channel that runs through pressure face and suction surface is seted up to the linear leaf, the trailing edge of linear leaf is located and is equipped with the tail edge wingtip on the pressure face. The utility model discloses the short blade that is arranged in adjacent linear leaf runner restraines blade surface airflow separation's emergence, the zigzag shaped channel reduces the pressure differential of pressure face and suction surface, reduces adverse pressure gradient, effective blowdown part blade afterbody suction surface boundary layer separation air current, tail edge's parabola shape winglet can restrain the growth in the wing tip whirlpool of the pressure differential production of traditional airfoil fan trailing edge suction surface and pressure face.

Description

A diffuser for a centrifugal compressor

technical field

The utility model belongs to the field of ventilation equipment and relates to a centrifugal fan, in particular to a diffuser of a centrifugal compressor.

Background technique

As an energy conversion device, the centrifugal compressor mainly drives the movement of the gas in the impeller channel through the rotation of the impeller, and converts the mechanical energy of the prime mover into the energy of the gas. Due to its high pressure, wide range of stable working conditions, simple structure, and easy maintenance, centrifugal compressors are widely used in industries such as petroleum, aerospace, metallurgy, chemicals, and mines, and play an important role.

In centrifugal compressors, the diffuser is generally divided into two types: vaneless diffuser and bladed diffuser. The vaneless diffuser is usually composed of two flat walls forming an annular channel. The structure of the vaneless diffuser is simple, the cost is low, the performance curve is gentle, the stable working condition is wide, and the efficiency is low when the Mach number is high, but the airflow angle in the vaneless diffuser is basically unchanged, and the airflow is basically Moving along the angular helical line, the flow path is longer, the friction loss is larger, and the efficiency is lower than that of the vane diffuser under the design working condition. Generally, vaneless diffusers are often used in compressors with small pressure ratios. The vane diffuser has the characteristics of large degree of diffusion and small size, and the airflow loss is smaller than that of the vaneless diffuser under the design working condition, so the efficiency is higher. The vane diffuser can reduce the pressure by increasing the radius, and at the same time, the radial vane can deflect the airflow angle according to the desired angle, so that the flow area can be further increased to improve the diffusion capacity; and it can improve the efficiency and stage pressure ratio of the centrifugal compressor , changing the position of the best working point and expanding the stable working range play a very important role.

However, due to the existence of blades in the vane diffuser, the impact loss under variable working conditions is relatively large, and the efficiency drops significantly. Compressors generally work at low flow rates, and at low flow rates, the airflow at the inlet of the diffuser blades forms a positive angle of attack. When the angle of attack reaches a certain value, severe airflow separation easily occurs in the flow channel. Moreover, once the air flow in the boundary layer on the suction surface is separated in a large area, it is very easy to cause the compressor to enter a stall and surge state, thereby seriously affecting the working stability of the engine. If the flow rate is greater than the design flow rate, it is easy to block the throat of the vane diffuser, causing the vane diffuser to lose its diffusion capacity.

Usually, in order to improve the performance of the diffuser, the compressor will use airfoil blades. Although the performance of the airfoil blades is better than that of the general version blades, it is still unavoidable due to the unevenness of the impeller outlet airflow and the angle of attack under variable working conditions. Therefore, improving the structure of the diffuser on the basis of airfoil blades and further improving its working performance have very important application value and work prospects.

Contents of the invention

The purpose of this utility model is to provide a diffuser for a centrifugal compressor, aiming at the problem that the inlet airflow angle of the diffuser is too large under the condition of small flow rate, the diffuser is located at the short blade of the adjacent long blade flow channel It can guide the airflow direction to change, change the airflow angle distribution in the diffuser flow channel, enable more airflow to flow along the airflow surface, and inhibit the occurrence of airflow separation on the blade surface, which not only improves the working efficiency of the diffuser, but also Increased scope of work. The zigzag channel in the diffuser can reduce the pressure difference between the pressure surface and the suction surface, reduce the reverse pressure gradient, and effectively blow off the airflow separated by the boundary layer of the suction surface at the tail of some blades. The parabolic winglet at the trailing edge can suppress the growth of the wingtip vortex generated by the pressure difference between the suction surface and the pressure surface of the trailing edge of the traditional airfoil blade, so that the position where the wingtip vortex falls off moves successively, reducing the strength of the wingtip vortex .

The utility model comprises long blades, short blades, a wheel disc and a wheel cover; the long blades have twelve pieces, which are evenly distributed on the wheel disc along the circumferential direction; a short blade is arranged in the flow channel of two adjacent long blades, and the short blade The side near the pressure side of the long blade. The intersection points of the leading edge lines of the pressure surfaces of the short blades and the long blades on the same longitudinal section are located on the same circle centered on the center of the disc, and on this circumference, the intersection points of the leading edge lines of the short blades are the same as those of the adjacent two blades. The central angles between the intercept points of the leading edge lines of the long blades are 9° and 21° respectively.

The leading edge of the long blade is curved and inclined, and the angle between the leading edge line and the central axis of the wheel is 6-8°; the curvature radius of the leading edge of the long blade gradually increases along the direction from the wheel to the wheel cover. The long blades are provided with three zigzag grooves running through the pressure surface and the suction surface. The three zigzag channels have the same shape, are arranged side by side along the length direction of the long blade, and the lengths of the three zigzag channels gradually decrease from the front edge to the rear edge of the long blade. The broken line groove is a two-section groove, the front section is the air inlet section, the rear section is the air outlet section, and the groove width of the air inlet section and the air outlet section is 10mm; the upper wall surface of the broken line shape groove and the long blade root The distance is 45% of the height of the long blade, and the distance between the lower wall and the root of the long blade is 5% of the height of the long blade.

The trailing edge of the long blade is located on the pressure surface and is provided with a trailing edge tip; the included angle between the side of the trailing edge tip and the tangent plane of the pressure surface at the trailing edge is 90°; the width value of the trailing edge tip is along the The direction from the wheel disc to the wheel cover increases according to the law of parabola, the width near the wheel disc is 0, and the maximum width does not exceed 5% of the chord length of the long blade.

The long blade adopts an airfoil structure, and the bolt is connected with the long blade threaded hole provided by the long blade to fix the long blade on the wheel disk.

The short blade adopts an airfoil structure, and the height and length are 0.7 of the long blade; the bolt is connected with the short blade threaded hole provided by the short blade to fix the short blade on the wheel disk.

The lengths of the arc segments between the inlets of the three zigzag slots along the center line in the height direction of the long blade and the suction front edge line of the long blade respectively account for 1/3 and 1/3 of the arc length of the suction surface of the long blade 1/2 and 2/3.

On the longitudinal section of the long blade, the inclination angle of the center line of the inlet section of the zigzag channel relative to the shape line of the blade at the intersection with the center line of the inlet section is 45°, and the center line of the outlet section is relative to the shape line of the blade in the outlet section. The inclination of the tangent at the intersection of the centerlines is 30°.

The beneficial effects of the utility model:

The utility model can improve the problem of changing the air flow angle at the inlet of the diffuser under variable working conditions. The short blades located in the adjacent long blade flow channels can guide the air flow direction to change, changing the air flow angle distribution in the diffuser flow channel. Allows more airflow to flow along the airflow surface, inhibits the occurrence of airflow separation on the blade surface, and prevents the occurrence of surge. In this way, not only the reasonable operating range of the centrifugal fan can be improved, but also the diffusion capacity and operating efficiency of the diffuser can be improved. The inclined structure of the leading edge of the long blade keeps the distance between the inlet of the diffuser and the outlet of the impeller at different positions in the direction of blade height, and adjusts the high-speed three-dimensional airflow from the impeller, especially reducing the Mach number of the airflow at the inlet of the diffuser. Reduced impact loss. The existence of short blades can effectively improve the incident airflow angle under variable working conditions. When the airflow enters the flow channel of the diffuser, the zigzag channel in the diffuser can reduce the pressure difference between the pressure surface and the suction surface, reduce the reverse pressure gradient, and effectively blow off the airflow separated by the surface layer of the suction surface at the end of the blade. , thereby reducing the area of the separation zone of the boundary layer, increasing the actual area of the blade channel, and increasing the flow rate of the compressor. The parabolic winglet at the trailing edge can suppress the growth of the wingtip vortex generated by the pressure difference between the suction surface and the pressure surface of the trailing edge of the traditional airfoil blade, so that the position where the wingtip vortex falls off moves successively, reducing the strength of the wingtip vortex , reducing the aerodynamic noise and improving the overall performance of the diffuser.

Description of drawings

Fig. 1 is a perspective view of the overall structure of the utility model;

Fig. 2 is a schematic diagram of the distribution of long and short blades on the wheel disk in the utility model;

Fig. 3 is a side perspective view of the long blade in the utility model;

Fig. 4 is another side perspective view of the long blade in the utility model;

Figure 5 is a partially enlarged view of Figure 4;

Fig. 6 is a schematic cross-sectional view of a broken-line channel of a long blade in the present invention;

Fig. 7 is a perspective view of the structure of the medium and short blades of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

As shown in Figures 1 and 2, a diffuser of a centrifugal compressor includes long blades 1, short blades 2, a wheel 3 and a wheel cover; the long blades 1 have 12 pieces, which are evenly distributed on the wheel along the circumferential direction; A short blade 2 is arranged in the flow channel adjacent to two long blades, and the short blade 2 is close to the side of the pressure surface of the long blade. The intersection points of the leading edge lines of the pressure surfaces of the short blade 2 and the long blade 1 on the same longitudinal section are located on the same circle with the center of the disc as the center, and on this circumference, the intersection points of the leading edge lines of the short blade 2 and the corresponding The central angles between the leading edge line intercept points of two adjacent long blades are α=9° and β=21° respectively.

As shown in Figures 3, 4 and 5, the long blade 1 adopts an airfoil structure, and the bolt is connected with the long blade threaded hole 1-2 provided by the long blade 1 to fix the long blade 1 on the wheel disk 3; the leading edge of the long blade 1-1 is a curved surface and is inclined. The angle between the leading edge line and the central axis of the wheel is 6°; the curvature radius of the leading edge of the long blade gradually increases along the direction from the wheel to the wheel cover. The long blade 1 is provided with three zigzag channels 1-3 passing through the pressure surface and the suction surface. The three zigzag channels have the same shape and are arranged side by side along the length direction of the long blade 1 , and the lengths of the three zigzag channels gradually decrease from the front edge to the rear edge of the long blade 1 . The zigzag channel is a two-section slot, the front section is the air inlet section, and the rear section is the air outlet section. The slot width of the inlet section and the air outlet section are both 10mm; the inlet section of the three zigzag slots is along the height of the long blade. The lengths of the arc segments between the central line of the direction and the suction front edge line of the long blade account for 1/3, 1/2 and 2/3 of the arc length of the suction surface of the long blade 1 respectively.

As shown in Figure 6, on the longitudinal section of the long blade 1, the inclination angle of the center line of the air inlet section of the zigzag channel relative to the blade profile line at the intersection with the center line of the air inlet section is 45°, and the center line of the air outlet section is opposite The inclination angle of the tangent line at the intersection point of the blade profile line with the center line of the air outlet section is 30°.

The distance between the upper wall of the zigzag channel and the root of the long blade 1 is 45% of the height of the long blade 1, and the distance between the lower wall and the root of the long blade 1 is 5% of the height of the long blade 1.

As shown in Figure 5, the trailing edge of the long blade is positioned at the pressure surface and is provided with trailing edge wing tip 1-4; °; the width value of trailing edge wing tip 1-4 increases according to the law of parabola along the direction from the disc to the wheel cover, and the width near the disc is 0, and the maximum width does not exceed 5% of the chord length of the long blade.

As shown in Figure 7, the short blade 2 adopts an airfoil structure, and the height and length are 0.7 of the long blade 1; the bolt is connected with the short blade threaded hole 2-1 provided by the short blade 2, and the short blade 2 is fixed on the wheel 3 superior.

The utility model is mainly aimed at the problem that the air flow angle at the inlet of the diffuser changes greatly under variable working conditions. The short blades located in the flow channel of the adjacent long blades can guide the direction of the air flow to change, changing the air flow angle in the flow channel of the diffuser. Distribution, so that more airflow can flow along the airflow surface, inhibit the occurrence of airflow separation on the surface of the blade, and prevent the occurrence of surge. This not only improves the reasonable operating range of the centrifugal fan, but also improves the diffusion capacity and operating efficiency of the diffuser.

The inclined structure adopted by the leading edge of the long blade keeps the distance between the inlet of the diffuser and the outlet of the impeller at different positions in the direction of blade height, which adjusts the uneven airflow from the impeller and greatly reduces the Mach flow at the inlet of the diffuser The number improves the distribution of the inlet airflow, reduces the impact loss at the inlet of the diffuser, and thus improves the operating efficiency of the diffuser.

As shown in Figures 3 and 6, the side-by-side channel structure in the diffuser further improves the distribution of the gas flow in the diffuser flow channel. The channel adopts a broken line shape, with the inlet section at the front and the outlet section at the back, which conforms to the characteristics of the airflow moving forward, and the channel connects the pressure surface and the suction surface of the diffuser, thus reducing the pressure surface and the suction surface. The pressure difference reduces the reverse pressure gradient and effectively blows off part of the air flow separated by the boundary layer on the suction surface of the blade tail, thereby reducing the area of the boundary layer separation zone and increasing the actual area of the blade channel, which not only improves the compressor flow, and can reduce eddy current noise.

As shown in Figures 4 and 5, the trailing edge of the long blade is distributed in a parabolic shape along the height of the blade, with a wide top and a narrow bottom, mainly because the distribution of the outlet airflow along the height of the blade is also uneven. The wingtip structure can suppress the increase of the wingtip vortex, reduce the strength of the wingtip vortex, and reduce the drag. The suppression of the wingtip vortex also makes the flow at the outlet of the runner more uniform and reduces the flow loss.

Claims (5)

1. A diffuser of a centrifugal compressor, comprising long blades, short blades, a wheel disc and a wheel cover, characterized in that: the long blades have twelve pieces, which are evenly distributed on the wheel disc along the circumferential direction; adjacent two A short blade is arranged in the flow channel of a long blade, and the short blade is close to the side of the pressure surface of the long blade; On the circumference, and on the circumference, the central angles between the intercept points of the leading edge lines of the short blades and the intercept points of the leading edge lines of two adjacent long blades are 9° and 21° respectively; The leading edge of the long blade is curved and inclined, and the angle between the leading edge line and the central axis of the wheel is 6-8°; the curvature radius of the leading edge of the long blade increases gradually along the direction from the wheel to the wheel cover; the long blade has three A zigzag channel that runs through the pressure surface and the suction surface; the three zigzag slots have the same shape and are arranged side by side along the length direction of the long blade, and the length of the three zigzag slots is from the front edge to the rear edge of the long blade The direction gradually decreases; the broken line groove is a two-section groove, the front section is the air inlet section, and the rear section is the air outlet section, and the groove width of the air inlet section and the air outlet section is 10mm; the upper wall of the broken line groove is The distance from the root of the long blade is 45% of the height of the long blade, and the distance between the lower wall and the root of the long blade is 5% of the height of the long blade; The trailing edge of the long blade is located on the pressure surface and is provided with a trailing edge tip; the included angle between the side of the trailing edge tip and the tangent plane of the pressure surface at the trailing edge is 90°; the width value of the trailing edge tip is along the The direction from the wheel disc to the wheel cover increases according to the law of parabola, the width near the wheel disc is 0, and the maximum width does not exceed 5% of the chord length of the long blade. 2. The diffuser of a centrifugal compressor according to claim 1, characterized in that: the long blade adopts an airfoil structure, and the bolt is connected with the long blade threaded hole provided by the long blade to fix the long blade on the on roulette. 3. The diffuser of a centrifugal compressor according to claim 1, characterized in that: the short blade adopts an airfoil structure, and the height and length are both 0.7 of the long blade; the short distance between the bolt and the short blade is Blade threaded hole connections to secure the short blades to the wheel. 4. The diffuser of a centrifugal compressor according to claim 1, characterized in that: the inlets of the intake section of the three zigzag channels are along the center line in the height direction of the long blades and the suction front edge of the long blades The lengths of the arc segments occupied by the lines respectively account for 1/3, 1/2 and 2/3 of the arc length of the suction surface of the long blade. 5. The diffuser of a centrifugal compressor according to claim 1, characterized in that: on the longitudinal section of the long blade, the center line of the inlet section of the zigzag channel is in the same position as the inlet section relative to the shape line of the blade. The inclination angle of the tangent line at the intersection point of the center line is 45°, and the inclination angle of the tangent line at the intersection point of the center line of the air outlet section relative to the blade profile line and the center line of the air outlet section is 30°.