Diffuser structure of non-axisymmetric end wall centrifugal compressor based on volute tongue position

Abstract

The invention discloses a volute tongue position-based centrifugal compressor diffuser structure with non-axisymmetric end walls, which can effectively inhibit asymmetric flow caused by a volute of a centrifugal compressor, improve the performance of the compressor and widen the stable operation range. Comprising a diffuser, the diffuser is provided with a wheel cover side end wall, a wheel back side end wall and a plurality of diffuser blades, diffuser channels are formed between the adjacent diffuser blades, and the diffuser channels comprise a volute tongue corresponding channel, a volute tongue corresponding channel left side channel and a volute tongue corresponding channel right side channel. The wheel cover side end wall and the wheel back side end wall of the volute tongue corresponding channel are both convex surfaces to reduce the circulation area, and the wheel cover side end wall and the wheel back side end wall of the volute tongue corresponding channel left channel and the volute tongue corresponding channel right channel are both concave surfaces to increase the circulation area, so that the airflow flow of the three diffuser channels is uniform under the influence of the volute.

Description

Technical Field

[0001] The invention relates to the technical field of centrifugal compressors, and in particular to a non-axisymmetric end wall centrifugal compressor diffuser structure based on a volute tongue position. Background Art

[0002] The centrifugal compressor uses the rotating impeller to generate centrifugal force to inhale, compress and discharge the gas to achieve the function of gas compression. Centrifugal compressors have the characteristics of small size and high single-stage pressure ratio. They are widely used in power systems in the fields of aviation, aerospace, shipbuilding, chemical industry, etc. The centrifugal compressor is mainly composed of a centrifugal impeller, a diffuser and a volute. The diffuser is connected to the compressor impeller on the top and the volute on the bottom. The airflow enters from the impeller inlet, flows through the diffuser, enters the volute, and is finally discharged. The flow in the diffuser is complex and directly affects the performance of the entire compressor stage. The diffuser is composed of diffuser blades and the end walls on both sides of the blades (the wheel cover side and the impeller side). The blades divide the diffuser into airflow channels equal to the number of blades. When the diffuser blades are evenly distributed circumferentially, the flow in each airflow channel should be the same, and the diffuser loss is the lowest at this time. However, since the volute after the diffuser is an asymmetric structure, the influence of the volute on the airflow will be transmitted upward to the diffuser, resulting in circumferential unevenness of the airflow in the diffuser, that is, the airflow in each channel is different, the diffuser loss increases, and the overall performance of the compressor decreases. This effect is most obvious in the diffuser channel corresponding to the volute tongue.

[0003] Patent application number CN201610378402.4 proposes an end wall treatment method to reduce the separation loss of the diffuser. This method takes the area surrounded by the arc line and the leading and trailing edges of two adjacent blades as a cycle, and uses NURBS surfaces to construct a pair of concave and convex structures with equal amplitudes in a single cycle to reduce the separation loss of the diffuser. However, this method does not take into account the circumferential non-uniformity of the flow in the diffuser caused by the asymmetry of the volute, so the improvement of the diffuser performance is relatively limited and has great limitations. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a non-axisymmetric end wall centrifugal compressor diffuser structure based on the position of the volute tongue, which can effectively suppress the asymmetric flow caused by the centrifugal compressor volute, improve the performance of the compressor, and widen the stable operating range.

[0005] The object of the present invention is achieved in that: A non-axisymmetric end wall centrifugal compressor diffuser structure based on the position of a volute tongue comprises a diffuser, wherein the diffuser has a wheel cover side end wall, a wheel back side end wall and a plurality of diffuser blades, a diffuser channel is formed between adjacent diffuser blades, and the diffuser channel comprises a volute tongue corresponding channel, a left channel of the volute tongue corresponding channel, and a right channel of the volute tongue corresponding channel. The wheel cover side end wall and wheel back side end wall of the channel corresponding to the volute tongue are both convex to reduce the flow area. The wheel cover side end wall and wheel back side end wall of the left channel and the right channel corresponding to the volute tongue are both concave to increase the flow area, thereby making the airflow flow of the three diffuser channels uniform under the influence of the volute.

[0006] Preferably, the concave surface and the convex surface are respectively formed by stretching a spline curve.

[0007] Preferably, the starting point of the spline curve is 10% of the circumferential curve of the blade channel, and the end point is 90% of the circumferential curve of the blade channel. The spline curve has three control points, which are: a control point at 30% of the circumferential curve of the blade channel, a control point at 50% of the circumferential curve of the blade channel, and a control point at 70% of the circumferential curve of the blade channel. The curvature continuity is ensured when the spline curve is connected to the plane end wall.

[0008] Preferably, H1, H2 and H3 are set as three control points along the normal height in sequence, H is the blade height, H1, H2, H3 are all less than 0.5H, and the spline curve is controlled by adjusting the values ​​of H1, H2, H3, thereby controlling the shape of the concave / convex surface.

[0009] Preferably, H1 is 0.05H, H2 is 0.15H, and H3 is 0.05H.

[0010] Preferably, the diffuser outlet control point position and height are the same as those of the diffuser inlet.

[0011] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention can effectively reduce the pressure non-uniformity in different channels of the diffuser, reduce the diffuser loss, improve the compressor performance, and increase the stable working range of the compressor. When the compressor is working under normal conditions, the flow area of ​​the three channels with the greatest influence of the volute tongue is adjusted through the non-axisymmetric end wall, thereby making the airflow in different channels of the diffuser more similar, the airflow in the diffuser more uniform, reducing the flow loss in the diffuser, and the compressor efficiency can be improved by more than 1%.

[0012] When the compressor is operating at low or high flow rates, the non-axisymmetric end wall structure can improve the unevenness of the flow in each channel of the diffuser blade, inhibit airflow separation, and thereby increase the flow range in which the compressor can operate stably. By using the structure of the present invention, the flow range of the compressor can be increased by more than 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of volute and diffuser; 1- volute tongue; 2- volute; 3- diffuser; Figure 2Diffuser schematic diagram; 4-the channel on the left side of the channel corresponding to the volute tongue; 5-the channel corresponding to the volute tongue; 6-the diffuser blade; 7-the channel on the right side of the channel corresponding to the volute tongue; 8-the diffuser (channel) outlet; 9-the diffuser (channel) inlet; the channel corresponding to the volute tongue refers to a channel opposite to the volute tongue (separated by two adjacent diffuser blades); Figure 3 Schematic diagram of the plane development of the non-axisymmetric end wall; 6-diffuser blade; 10-wheel cover side control point 1; 11-wheel cover side control point 2; 12-wheel cover side control point 3; 13-wheel cover side control point 4; 14-wheel cover side control point 5; 15-wheel cover side control point 6; 16-wheel cover side control point 7; 17-wheel cover side control point 8; 18-wheel cover side control point 9; 19-impeller side control point 9; 20-impeller side control point 8; 21-impeller side control point 7; 22-impeller side control point 6; 23-impeller side control point 5; 24-impeller side control point 4; 25-impeller side control point 3; 26-impeller side control point 2; 27-impeller side control point 1.

[0014] The end wall refers to the two side planes in the thickness direction of the diffuser, the wheel cover side end wall and the wheel back side end wall, respectively. Figure 3 The upper and lower sides. DETAILED DESCRIPTION

[0015] A non-axisymmetric end wall centrifugal compressor diffuser structure based on the position of a volute tongue comprises a diffuser 3, wherein the diffuser 3 has a wheel cover side end wall, a wheel back side end wall and a plurality of diffuser blades 6, wherein a diffuser channel is formed between adjacent diffuser blades 6, wherein the diffuser channel comprises a volute tongue corresponding channel 5, a left channel 4 of the volute tongue corresponding channel, and a right channel 7 of the volute tongue corresponding channel. The wheel cover side end wall and the wheel back side end wall of the volute tongue corresponding channel 5 are both convex to reduce the flow area, and the wheel cover side end wall and the wheel back side end wall of the left channel 4 of the volute tongue corresponding channel and the right channel 7 of the volute tongue corresponding channel are both concave to increase the flow area, thereby making the airflow of the three diffuser channels uniform under the influence of the volute.

[0016] The non-axisymmetric end wall structure is for the channel 5 corresponding to the volute tongue and the channels 4 and 7 on both sides. The wheel cover side and the impeller side of the channel corresponding to the volute tongue use convex surfaces instead of planes, and the channels 4 and 7 on both sides of the channel use concave surfaces to replace the wheel cover side and the impeller side planes. The concave and convex surfaces are stretched by spline curves. Taking the convex surface shape of the diffuser inlet 9 impeller side of the volute tongue corresponding channel 5 as an example, the spline curve is constructed using three control points 22, 23 and 24. The starting point of the spline curve is 10% of the circumferential curve of the blade channel, and the end point is 90%. Control point 4 (22) is at 30% of the curve, control point 5 (23) is at 50% of the curve, and control point 6 (22) is at 70% of the curve. The curvature continuity is ensured when the spline curve is connected to the original end wall. H1, H2 and H3 are the normal heights of control points 4, 5 and 6 respectively, H is the blade height, H1, H2 and H3 are all less than 0.5H, and the spline curve is controlled by adjusting the values ​​of H1, H2 and H3, thereby controlling the shape of the convex surface. In the example of the present invention, H1 is 0.05H, H2 is 0.15H and H3 is 0.05H.

[0017] The concave shapes of channels 4 and 6 on both sides of the volute tongue corresponding channel are also constructed with spline curves. Taking the concave shape of the diffuser inlet 9 impeller side of channel 4 on the left side of the volute tongue corresponding channel as an example, the concave shape can be adjusted by adjusting the position and height of control points 1-3 (27-25).

[0018] The 9 control points on the wheel cover side are 10-18 in the figure, and the 9 control points on the impeller side are 19-27 in the figure. By adjusting the percentage position and height of each control point, the non-axisymmetric end wall can be controlled in detail. The position and height of the diffuser outlet control point are usually the same as the inlet, and complex curved surface structures can also be constructed differently, making the structure suitable for compressor and compressor diffuser structures of different sizes, flow velocities, and working fluids. In addition, it can also be used for bladeless diffuser structures.

[0019] The present invention further reduces the loss of the centrifugal compressor diffuser and improves the stable working range of the compressor. The flow area is controlled by using NURBS surfaces on the end walls of the diffuser channel corresponding to the volute tongue and the two left and right channels. The diffuser channel corresponding to the volute tongue uses a convex surface shape to reduce the flow area, and the left and right channels use a concave shape to increase the flow area, thereby adjusting the airflow rate of the three channels, making the flow in the diffuser more uniform while considering the influence of the volute, reducing the compressor loss, improving the compressor performance, and increasing the stable working range of the compressor.

[0020] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A non-axisymmetric end wall centrifugal compressor diffuser structure based on the position of the volute tongue, comprising a diffuser, wherein the diffuser has a wheel cover side end wall, a wheel back side end wall and a plurality of diffuser blades, and a diffuser channel is formed between adjacent diffuser blades, and the diffuser channel includes a volute tongue corresponding channel and a left channel and a right channel of the volute tongue corresponding channel, characterized in that: The wheel cover side end wall and wheel back side end wall of the channel corresponding to the volute tongue are both convex to reduce the flow area. The wheel cover side end wall and wheel back side end wall of the left channel and the right channel corresponding to the volute tongue are both concave to increase the flow area, thereby making the airflow flow of the three diffuser channels uniform under the influence of the volute.

2. The non-axisymmetric end wall centrifugal compressor diffuser structure based on the volute tongue position according to claim 1, characterized in that: The concave surface and the convex surface are respectively formed by stretching a spline curve.

3. The non-axisymmetric end wall centrifugal compressor diffuser structure based on the volute tongue position according to claim 2, characterized in that: The starting point of the spline curve is 10% of the circumferential curve of the blade channel, and the end point is 90% of the circumferential curve of the blade channel. The spline curve has three control points, which are: a control point at 30% of the circumferential curve of the blade channel, a control point at 50% of the circumferential curve of the blade channel, and a control point at 70% of the circumferential curve of the blade channel. The curvature continuity is ensured when the spline curve is connected to the plane end wall.

4. The non-axisymmetric end wall centrifugal compressor diffuser structure based on the volute tongue position according to claim 3, characterized in that: H1, H2 and H3 are set as the three control points along the normal height in sequence, H is the blade height, H1, H2, H3 are all less than 0.5H, and the spline curve is controlled by adjusting the values ​​of H1, H2, H3, thereby controlling the shape of the concave / convex surface.

5. The non-axisymmetric end wall centrifugal compressor diffuser structure based on the volute tongue position according to claim 4, characterized in that: H1 is 0.05H, H2 is 0.15H, and H3 is 0.05H.

6. The non-axisymmetric end wall centrifugal compressor diffuser structure based on the volute tongue position according to claim 4, characterized in that: The position and height of the diffuser outlet control point are the same as those of the diffuser inlet.

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