CN1871438A - Diffuser for centrifugal compressor - Google Patents

Abstract

A diffuser (30) for a centrifugal compressor (60) having a flow slot (34) formed between the leading edge portion (36) of a diffuser vane (32) and an adjoining diffuser wall (70) for the passage of working fluid (67) over the vane from the pressure side ((40) to the suction side (42) of the vane. The portion (38) of the working fluid passing over the vane is injected into the flow boundary region (43), thereby minimizing the growth of a flow separation zone (58) along the suction side.

Description

The Diffuser of centrifugal compressor

Related application

It is the preference of 60/505885 U.S. Provisional Patent Application that the application requires in the application number that on September 24th, 2003 submitted.

Technical field

The application is usually directed to the turbo machine field, especially relates to the Diffuser of centrifugal compressor.

Background technique

As everyone knows, centrifugal compressor utilizes Diffuser that a part of kinetic energy that leaves the working fluid of compressor impeller is transformed into static pressure, and this transition process reduces flow velocity when passing through the expansion fluid zone by working fluid and realizes.Diffuser can have that to be commonly referred to be the aerofoil profile of blade, and it is used to guide working fluid and strengthens above-mentioned energy transition process by expander, and wherein each blade has pressure side and the suction surface with respect to the angle of attack of work incoming flow.Fig. 1 shows Diffuser 10 of the prior art and how forms big flow separation zone 12 at the suction surface 14 of diffuser vane 16 under certain condition.This flow separation zone 12 is flow boundary layer basically, and the speed here is lower than other places of fluid, so can hinder the flow rate of whole fluid.Flow separation zone 12 produces the compressor discharge currents 18 of distortion, therefore can reduce the efficient of compressor, may also can cause the stall and the surging phenomenon of compressor, can the downstream area of compressor and/or turbo-charged engine be damaged like this.For compressor as for the embodiment of diesel turbocharging device on the railway locomotive, when the condition following time of locomotive operation at high latitudes, low ambient temperature and upper air temperature degree, the easiest stall and the surge accident of occurring of this compressor; For example when locomotive just when the tunnel of high latitudes rolls away from.

As shown in Figure 1, the traditional theory of compressor diffuser blade 16 design provides from blade inlet edge 22 to trailing edge 24 continuous surface 20, thereby the blade table area the pressure reduction that is exposed between suction surface 14 and the pressure side 26 is under maximized.Need choose the position of blade and angle in a kind of compromise mode, that is, should prevent the stall of fluid, keep the various effective pressures that enter the angle of attack of air-flow that are expected to impact on the blade again and recover.

Description of drawings

Fig. 1 shows the flow boundary layer segregation phenomenon on the diffuser vane suction surface in the centrifugal compressor of prior art.

Fig. 2 shows the flox condition on the suction surface of slotted diffuser vanes.

Fig. 3 is the compressor map of the leaf grating Diffuser of prior art.

Fig. 4 is the compressor map with multistage Diffuser of slotted vanes.

Fig. 5 is the part sectioned view with compressor of slotted diffuser vanes.

Fig. 6 shows the throat region of the island formula Diffuser (island diffuser) with slotted vanes.

Fig. 7 shows the throat region of slotted vane cascade diffuser.

Fig. 8 is the part sectioned view that has the compressor diffuser of some runners from blade pressure surface to suction surface.

Fig. 9 is the perspective view that has a part of Diffuser of the slotted vanes with leading edge supporting element.

Embodiment

The claimant finds by experiment, for realizing in the optimized prior art of diffuser performance in the design of Centrifugal Compressor, owing on blade suction surface, be formed with the fluid breakdown zone, therefore the efficient of compressor may reduce, and blade causes surge possibly, thereby causes compressor stall.In addition, to describe in detail as following, the claimant has found by forming mobile perforate, allow the part working fluid flow through or flow through suction surface from blade pressure surface, thereby the fluid breakdown zone can diminish or eliminate, therefore efficient be improved, and the possibility of surge or stall generation also will reduce.

Fig. 2 shows the Diffuser 30 of the centrifugal compressor after the improvement.Diffuser vane 32 includes and allows part working fluid 38 to flow to the perforate of suction surface 42 from the pressure side 40 of blade profile.This perforate in Fig. 2 as be formed on blade 32 leading edge portion 36 and the coupling diffuser wall member between slit 34.For the clearer flow path of seeing blade profile and workflow, the wall member of this coupling is not shown in Fig. 1 and 2; Yet, will be appreciated that the relative wall member of Diffuser can be placed in the above and below of blade and extends between the blade, to limit the runner of working fluid betwixt.Slit 34 allows part working fluids 38 from blade pressure surface 40 to suction surface 42 and flow through blade 32, thereby the fluid boundary zone 43 of suction surface 42 flowing process fluid is being pasted in excitation again, and therefore any flow separation zone that may be tending towards forming 44 is minimized.Believe that the part working fluid 38 that flows through blade 32 has produced the eddy current of interfering the flow separation zone growth.Fig. 1 schematically illustrates under the identical inlet angle of attack and flox condition with the contrast of Fig. 2, compares with the blade 16 of prior art, and flow separation regions 44 sizes of blade 32 reduce and export the uniformity improvement of stream 46.

The contrast of Fig. 3 and Fig. 4 provides a kind of example of diagrammatic, and it shows that the slotted diffuser vanes 32 by adopting Fig. 2 will make the performance of compressor be improved.Fig. 3 and Fig. 4 are the traditional compressor performance charts, each figure comprises some substantially horizontal lines, represents the performance (through the flow velocity of temperature correction and the ratio of compressor transfer pressure) of the compressor of compressor under the compressor operating speed of the temperature correction of respectively hanging oneself.Fig. 3 is to use performance curve Figure 50 of the compressor of leaf grating Diffuser in the prior art, and this Diffuser has the sort of blade shown in Figure 1.Thereby Fig. 4 has made the improved isoboles (equivalent map) 52 that comprises with the same compressor of those similar flow slot 34 shown in Figure 2.The flow rates (that is, extending to the longer horizontal component of the curve of relatively low and high flow velocities) that the operating rate of noting Fig. 4 compressor can both obtain to expand under any given compressor operating speed.Surge line 54,56th, left end (low-speed flow) the point formation by the speed line after connecting each and proofreading and correct.Usually, under the same conditions, the compression function of Fig. 4 just may operate at before the stall phenomenon takes place under the low flow velocity.The right side that equally also will note each performance line of improved design in Fig. 4 is generally come under the right side not as the performance line of Fig. 3 fast.Right-hand member (high speed flow) the point formation of line 58,60 (choked flow) by the speed line after connecting each and proofreading and correct.The difference of these two lines has shown that Fig. 4 compressor will have the flow rate efficiency of raising than Fig. 3 compressor of the prior art.Owing to the performance that has adopted flow openings 34 to obtain improves, can provide to prevent that improvement amplitude or Component Design person that the surge/stall accident produces from can adopt other mode to utilize it to improve the overall performance of Component Design.

Flow openings slit 34 be when assembling be formed at during Diffuser 30 blade 32 and and the diffuser walls of its coupling between gap (not shown in Fig. 2).Blade 32 normally forms one with basal disc, as processing these parts with a from one piece, perhaps the blade of independent formation is welded on the basal disc.Thereby can be before each vane tip surface be connected to separately corresponding diffuser walls with recess or groove processing in these surfaces, make its on the pressure side 40 and suction side 42 between extension.When assembling Diffuser 30, these recesses are represented material is removed, thereby define flow slot 34 along the blade inlet edge part 36 of the most approaching diffuser walls that is complementary.

Fig. 5 is the part sectioned view that comprises the compressor 60 of Fig. 2 improved diffuser 30.Impeller 62 is rotatable between air inlet housing 64 and compressor case 70, so that compression working fluid 67 flows through in Diffuser 30 and the intake duct air bells exhauster shell 66.Diffuser vane 32 is between relative diffuser walls; In this mode of execution, a wall is a Diffuser basal disc 68, and another relative wall is a compressor case 70.Flow slot 34 is formed on the leading edge place of the diffuser vane 32 adjacent with shell 70.

Fig. 6 is the fragmentary top pseudosection of improved vane island formula Diffuser (wedge type Diffuser) 72.Fig. 7 is the fragmentary top pseudosection of the multistage Diffuser 74 of modified model.These are the throat 76,78th of Diffuser 72,74 separately, and adjacent blades is along they distance of chord length direction between their closest approaches separately.Flow openings of the present invention can a bit be extended suitable distance along the blade chord length from blade inlet edge or from the leading edge downstream, and for example, its scope is from least 5% to no more than 25% or no more than 38% of the blade chord length in numerous embodiments.As shown in Figure 6, flow slot can only upstream be extended from the blade aditus laryngis along the blade inlet edge part, rather than extends to the point downstream of throat from throat.

The degree of depth of groove can be suitable dimensions, as in one embodiment, is 10% of no more than blade height perpendicular to the blade chord length, perhaps in another embodiment, and 5% of no more than this blade height.Because opening has defined the path that fluid flows, institute thinks and avoids working fluid to bring chip into and the blocking phenomenon that causes, so need set up actual lowest distance value, for example 50 mils.

From on the pressure side can changing according to different applications with geometrical shape of Diffuser aerofoil profile to the accurate position that suction side forms flow openings.Flow path can be a single opening or along blade chord length a plurality of openings at interval.In these a plurality of openings each can have identical or different geometrical shape.Flow slot is considered to be preferably formed in the junction point of blade and corresponding relative wall, and this is because flow separation generally at first is to produce along this corner.Yet in some embodiments, opening can be formed in the blade that shifts out adjacent wall a little, perhaps as shown in Figure 8, is formed in the wall member of coupling.Fig. 8 is the part sectioned view with compressor diffuser 80 of blade 82, and this blade is connected relative wall 84, thereby guides flowing of working fluid 88 between 86.Have a hole 90 that drills blade 82 at least, making has inlet on the pressure side near first wall 84, and suction surface has outlet, with the first portion that allows working fluid 88 there of flowing through.The outlet in hole 90 is positioned on the suction surface of throat location 89 upstream ends of blade 82 (dotted line is represented).The second portion of working fluid 88 can flow to suction surface one side from pressure side by the opening that is formed on as groove 92 in second wall 86.Can be selected as to optimize the influence that bypass flow forms the downstream flow separation zone along the hole 90 of blade 82 chord lengths and the position of groove 92.From manufacture view, be easily like this, make before wall and blade be complementary, flow openings is formed along the machining groove of blade upper surface on the pressure side and between the suction side, and/or be the machined recess that forms it in the diffuser walls.In some embodiments, it is desirable to, flow slot is formed on the blade two opposite sides of approaching two relative diffuser walls most.

Normally, wish to produce minimum bypass flow and pass through blade, it is to a certain degree necessary that wherein said bypass flow is that the expansion with the flow separation zone on the blade suction surface is suppressed to, thereby can make the low swiftly flowing performance of outlet distributions and Diffuser reach the raising of expected degree.Usually, more bypass flow will make low swiftly flowing performance obtain bigger improvement, the compressor peak efficiency is reduced accordingly, therefore, suggestion is for a certain specialized application, and reply reaches desirable bypass flow opening geometrical shape and carries out cost/performance analysis.Such as for the employed turbosupercharger Diffuser of the modern locomotive of present assignee manufacturing, diffuser vane can have about 4 inches chord length and about 0.9 inch blade height usually.In this device, width is 0.050 inch and 0.085 inch and has also approximately carried out successful test along 15% flow slot of extending of chord length.

Fig. 9 is another embodiment's a fragmentary, perspective view, has wherein used support link 94 between the leading edge 96 of blade 98 and diffuser walls 100, if necessary or it is desirable to provide machinery support for the leading edge 96 of blade 98.Flow openings 102 is from supporting that link 94 extends downstream along the leading edge portion of blade 98.This supports link 94 can be the whole extension part of blade material or for example can form by welding manufacturing, or the sheet material that connects separately.In an embodiment, for locomotive turbo, flow openings 102 can be from the about backward 0.1 inch beginning of the front edge 96 of blade as described above 98.The front edge supporter can be used for handling the vibration problem of diffuser vane, especially the vibration problem of slim vane Diffuser.This vibration can be caused by the interaction of flowing between compressor impeller blade and the diffuser vane.Supporter 94 can produce mechanical constraint to the front edge 96 of blade 98, so this supporting element can prevent the hurtful undue oscillation of component life.

Here to preferred features more of the present invention in addition diagram and introduce in, be only to be that the mode with example provides these embodiments significantly.Without departing from the scope of the present invention, for a person skilled in the art, can carry out various changes and replacement.Therefore, the present invention is only limited by the spirit and scope of claims.

Claims (10)

1, the Diffuser (30) of compressor (60), this Diffuser comprises:

Relative wall (68,70), they have defined the space that is positioned at compressor impeller (62) downstream part for the working fluid (67) that receives from impeller;

Blade (32), it comprises pressure side (26) and the suction surface (14) that is connected between the described relative wall, is used to guide working fluid to pass through described space;

Flow slot (34), it is formed between blade and the wall, this flow slot is upstream extended along partial blade from blade throat (76), makes part working fluid (38) flow to suction surface from the pressure side of blade, thereby suppresses the expansion of flow separation zone (44) on the blade suction surface.

2, Diffuser as claimed in claim 1 is characterized in that, flow slot comprises the groove (34) that is formed in the blade surface, and this groove is to form before this blade surface being connected on the corresponding adjacent wall.

3, Diffuser as claimed in claim 1 is characterized in that, flow slot extends to the leading edge (22) of blade.

4, Diffuser as claimed in claim 1 is characterized in that, this groove a bit extends downstream from blade inlet edge (22) downstream, supports link (94) thereby define between a wall at blade and leading edge place.

5, Diffuser as claimed in claim 1 is characterized in that, flow slot has the height perpendicular to the blade chord length, 5% of its no more than blade total height perpendicular to the blade chord length.

6, Diffuser as claimed in claim 1 is characterized in that, flow slot has the height perpendicular to the blade chord length, 10% of its no more than blade total height perpendicular to the blade chord length.

7, Diffuser as claimed in claim 1 is characterized in that, flow slot is extended along 25% of no more than blade chord length.

8, Diffuser as claimed in claim 1 is characterized in that, flow slot is extended along 38% of no more than blade chord length.

9, Diffuser as claimed in claim 1 is characterized in that, the groove that flows is along 5% extension of blade chord length at least.

10, a kind of compressor (60), it comprises Diffuser as claimed in claim 1 (30).

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