CN108374792B - A Centrifugal Compressor Using A/r Non-Linear Distribution of the Flow Channel Section of the Volute - Google Patents

Abstract

Spiral casing flow passage section A/r nonlinear Distribution centrifugal compressor is used the present invention relates to a kind of, belongs to impeller machinery technical field.Centrifugal compressor of the invention includes casing, centrifugal impeller, back disk and diffuser.The area radius ratio (A/r) in the spiral casing flow passage section in the present invention is nonlinear Distribution in the circumferential, and is lower than the rate of rise in other circumferential positions in volute tongue near zone spiral casing flow passage section A/r rate of rise.The present invention is able to suppress the flow distortion of Centrifugal Compressor, and flow field mixing loss is effectively reduced, while the heterogeneity in flow field is effectively reduced, to significantly improve the aeroperformance and flow stability of centrifugal compressor.

Description

A Centrifugal Compressor Using A/r Non-Linear Distribution of the Flow Channel Section of the Volute

technical field

The invention relates to a centrifugal compressor adopting the non-linear distribution of A/r of the volute channel section, belonging to the technical field of impeller machinery.

Background technique

The present invention relates to a centrifugal compressor adopting the non-linear distribution of volute channel cross section A/r, which relates to centrifugal compressors for superchargers for various purposes such as vehicles, ships, and aviation, and centrifugal compressors used in blowers, etc. compressor.

Compared with the existing reciprocating piston compressors, impeller compressors such as centrifugal compressors have the advantages of high efficiency, light volume and weight, and stable operation. However, the operating range of the centrifugal compressor is limited, especially in non-design conditions such as small flow, due to the circumferential asymmetry of the volute geometry and the influence of the volute tongue structure, the internal distortion of the centrifugal compressor is formed, and the flow field presents extreme Strong circumferential asymmetry induces premature unstable flow inside the centrifugal compressor, causing stall or even surge, which will directly lead to a decrease in the pressure ratio and efficiency of the centrifugal compressor, shorten the life of the centrifugal compressor and even damage the centrifugal compressor in a short time machine.

The volute is an important part of the centrifugal compressor. It mainly plays the role of collecting compressed gas. At the same time, because its flow cross-sectional area increases with a certain law in the circumferential direction, it also plays a certain role in reducing pressure (large flow) or diffuser (small flow) effect. The volute is a channel with a specific radius as the inlet, and the area-to-radius ratio (A/r) of the flow channel section along the circumferential direction increases continuously. The distribution law of the area-radius ratio (A/r) of the traditional volute flow channel section is determined by the design operating point of the centrifugal compressor, and the fluid pressure is theoretically guaranteed under the premise that the fluid parameters entering the volute are uniform in the circumferential direction. The circumferential direction is kept constant to achieve the effect of not introducing circumferential flow field distortion while collecting gas. Since it is assumed that the airflow parameters entering the volute from any circumferential position are the same (circumferential uniformity assumption), the traditional volute flow channel cross-sectional area radius ratio (A/r) is linearly distributed in the circumferential direction. In fact, under the influence of the volute tongue structure, the airflow entering the volute is different in the circumferential direction, especially the airflow parameters (such as static pressure) in the vicinity of the volute tongue will change drastically. Under this real flow condition, the volute with a linear distribution of the cross-sectional area radius ratio (A/r) of the volute channel tends to increase the inhomogeneity of the flow field, which brings severe flow stability problems and induces the premature failure of the centrifugal compressor. Unstable disturbances and even surges occur.

Contents of the invention

The purpose of the present invention is to propose a centrifugal compressor adopting the non-linear distribution of the cross-section A/r of the volute flow channel, to improve the volute flow channel of the existing centrifugal compressor, under the premise of ensuring that the structure does not change greatly , suppress the distortion of the flow field inside the centrifugal compressor, especially the distortion of the flow field near the volute tongue, improve the flow stability inside the centrifugal compressor, and broaden the stable working range of the centrifugal compressor.

The present invention proposes a centrifugal compressor that adopts the non-linear distribution of the volute flow channel section A/r, including a casing, a centrifugal impeller, a back plate and a diffuser; the centrifugal impeller and the diffuser are coaxially installed, The centrifugal impeller is driven by the rotating shaft of the centrifugal compressor. The casing and the back plate are relatively fixed. In the radial range between the outer end of the casing and the outer edge of the centrifugal impeller, the casing and the back plate form an annular flow channel. A diffuser is formed, guide blades can be installed on the diffuser part, or no blades can be installed, the outer end of the annular flow channel is connected to the volute flow channel defined by the volute, and the volute is the outer end of the casing part, the inlet of the volute flow channel communicates with the outlet of the annular flow channel, and it is characterized in that: the area-radius ratio (A/r) of the volute flow channel cross-section changes nonlinearly in the circumferential direction, specifically embodied as: near the volute tongue In the area (centered on the volute tongue, the area covered by 90°-180° in the circumferential direction), the growth rate of the volute flow channel cross-sectional area radius ratio (A/r) is smaller than that in other circumferential positions.

The present invention proposes a centrifugal compressor that adopts the non-linear distribution of the volute flow channel section A/r, and its advantage is: the centrifugal compressor involved in the present invention, due to the area radius ratio (A /r) The growth rate in the area near the volute tongue is smaller than that in other circumferential positions, which can suppress the flow field distortion caused by the volute tongue structure, effectively reduce the mixing loss of the flow field and reduce the internal flow field of the centrifugal compressor Non-uniformity, thereby delaying the occurrence of flow instability, alleviating the flow instability caused by excessive flow field distortion in the circumferential direction, which induces the overall surge of the compressor, and greatly improving the aerodynamic performance and flow stability of the centrifugal compressor sex. At the same time, since only the local fine-tuning of the volute flow channel is involved, the main structure such as the casing is not changed, so no additional cost will be generated in the production and processing process.

Description of drawings

Fig. 1 is a cross-sectional view of a centrifugal compressor with a non-linear distribution of the volute channel section A/r proposed by the present invention.

Fig. 2 is a schematic cross-sectional view of the volute flow channel in the centrifugal compressor shown in Fig. 1 .

Fig. 3 is a front view of the centrifugal compressor shown in Fig. 1 and a schematic diagram of definition of circumferential angles.

Fig. 4 is the circumferential position of the shape correction factor ε in one embodiment of the present invention Distribution.

Fig. 5 is the modified growth rate k along the circumferential direction of the volute channel section A/r in one embodiment of the present invention Distribution.

Fig. 6 is the position along the circumferential direction of the section A/r of the flow path of the volute in one embodiment of the present invention Distribution.

In Figure 1, Figure 2 and Figure 3, 1 is the inlet of the centrifugal compressor, 2 is the centrifugal impeller, 3 is the diffuser, 4 is the back plate, 5 is the volute flow channel, 6 is the casing, 7 is the volute tongue, 8 is the outlet channel of the volute, 9 is the inlet of the volute, and 10 is the cross section of the volute.

Detailed ways

Below in conjunction with accompanying drawing, content of the present invention is described in detail:

The present invention proposes a centrifugal compressor adopting a volute with flow path section A/r non-linear distribution. Its structure is shown in FIG. The centrifugal impeller 2 and the diffuser 3 are installed coaxially, and the centrifugal impeller 2 rotates under the drive of the shaft. The casing 6 is relatively fixed to the back plate 4 , and the outer end of the casing 6 forms a volute flow channel 5 . As shown in FIG. 2 , the cross section 10 of the volute channel increases continuously along the impeller rotation direction in the circumferential direction, essentially the volute channel section area radius ratio (A/r) increases continuously along the impeller rotation direction. The area-to-radius ratio (A/r) of the volute flow channel section is defined as:

Among them, R represents the radial position, which is the distance from the center of the rotating shaft, and S is the cross-sectional area of the volute flow channel. According to the centrifugal compressor of the present invention, the area-to-radius ratio (A/r) of the volute flow channel cross-section is non-linearly distributed in the circumferential direction, which is characterized by the area-to-radius ratio (A/r) of the volute flow channel cross-section in the region near the volute tongue 7 ( A/r) Growth rate is lower than other circumferential positions. The definition of the circumferential position is shown in Figure 3, with the axis of rotation as the origin of the coordinates, the x direction is defined as the direction perpendicular to the outlet channel 8 of the volute, then the 0° circumferential position is the position corresponding to the positive direction of the x-axis, One rotation along the direction of impeller rotation corresponds to 360°. The cochlear tongue is shown in FIG. 3 in the vicinity of the approximately 60° position. Compared with other centrifugal compressor volute channel cross-sectional designs (generally A/r is linearly distributed along the circumferential direction), the volute channel design of the centrifugal compressor in the present invention can effectively suppress the flow field distortion caused by the volute tongue 7 , reduce the mixing loss of the flow field and the unevenness of the flow field, and effectively improve the aerodynamic performance and flow stability of the centrifugal compressor; at the same time, the invention does not involve the main structural changes of the centrifugal compressor, and the design is simple and does not increase additional manufacturing costs .

The method for determining the circumferential distribution of the volute flow passage section A/r is described through an embodiment of the present invention, and the process is as follows:

1) Based on the assumption that the flow field is uniform in the circumferential direction, and according to the design parameters of the centrifugal compressor, the growth rate k _linear of the volute flow channel cross-sectional area radius ratio (A/r) in the circumferential direction is obtained through mathematical derivation (that is, the traditional volute flow channel The growth rate corresponding to the linear distribution design of the cross-sectional area radius ratio (A/r), and determine the A/r at the throat position of the volute flow channel according to the matching conditions of the components. In one embodiment of the present invention, the values of the growth rate k _linear and the A/r at the throat position of the volute are respectively k _linear =0.0314[mm/°] and Among them, the corresponding circumferential position of the throat is

2) Determine the value of the shape correction factor ε at different circumferential positions. Wherein, the value range of ε is 0<ε≤5, and it is required that ε<1 at the circumferential position near the cochlear tongue and ε>1 at the circumferential position away from the cochlear tongue. In one embodiment of the present invention, the position of the cochlear tongue is at 60°, and the distribution of the shape correction factor ε in the circumferential direction is shown in FIG. 4 .

3) According to the formula k=ε·k _linear + δk, determine the corrected growth rate k of the volute runner section area radius ratio (A/r) at each circumferential position, where δk is a correction parameter, and values are taken at different circumferential positions Can be different, and the value range is -0.5·k _linear <δk<0.5·k _linear . In one embodiment of the present invention, δk=0 is used at all circumferential positions, and the distribution of the obtained corrected growth rate k in the circumferential direction is shown in Figure 5;

4) According to the formula Determine each circumferential position A/r, so as to obtain the distribution law of the volute channel section A/r in the circumferential direction. The distribution of the volute flow channel section A/r in the circumferential direction determined in one embodiment of the present invention is shown in Figure 6 (Note: The volute flow channel 5 and the volute outlet flow channel 8 in the range of 0° to 60° are the same The volute tongue is formed through, in fact, this section of the volute flow channel is included in the volute outlet flow channel, so this section is indicated by a dotted line in the figure). Due to the limitation of relevant parameters in 2) and 3), the obtained volute channel area radius ratio (A/r) is nonlinearly distributed in the circumferential direction, and the area radius ratio (A/r) in the vicinity of the volute tongue is r) Growth rate is lower than other circumferential positions.

Claims (1)

1. A centrifugal compressor comprises a shell, a centrifugal impeller, a back disc and a diffuser; the outer end of the diffuser is connected with a volute flow channel limited by a volute, the volute is the outer end part of the casing, and the inlet of the volute flow channel is communicated with the outlet of the annular flow channel, and the volute flow channel is characterized in that: the area-radius ratio (A/r) of the cross section of the volute flow channel is nonlinearly changed in the circumferential direction, and specifically comprises the following steps:

wherein,in order to be a circumferential position,is the area radius ratio of the flow passage section at the throat of the volute and is determined by the matching condition of components,the circumferential position of a throat of the volute is shown, k is the corrected growth rate of the area-radius ratio (A/r) of the cross section of the flow passage of the volute in the circumferential direction, and k is epsilon.k_linearThe + delta k and the epsilon are shape correction factors, depend on the static pressure circumferential distribution at the inlet position of the volute, can have different values at different circumferential positions, and have a value range of 0<Epsilon is less than or equal to 5, and the circumferential position epsilon of static pressure decreasing along the rotating direction of the impeller>1, and epsilon at a circumferential position where static pressure increases in the direction of rotation of the impeller<The static pressure circumferential distribution can be obtained by engineering measurement or numerical simulation, k_linearThe theoretical growth rate of the area-radius ratio (A/r) of the volute flow channel section in the circumferential direction is obtained through theoretical calculation, delta k is a correction parameter, values can be different at different circumferential positions, and the value range is-0.5 k_linear<δk<0.5·k_linear。