CN111259559B - Flow control method for reducing loss by cantilever stator blade front loading design - Google Patents
Flow control method for reducing loss by cantilever stator blade front loading design Download PDFInfo
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- CN111259559B CN111259559B CN202010078012.1A CN202010078012A CN111259559B CN 111259559 B CN111259559 B CN 111259559B CN 202010078012 A CN202010078012 A CN 202010078012A CN 111259559 B CN111259559 B CN 111259559B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D19/00—Axial-flow pumps
- F04D19/02—Multi-stage pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/52—Casings; Connections of working fluid for axial pumps
- F04D29/54—Fluid-guiding means, e.g. diffusers
- F04D29/541—Specially adapted for elastic fluid pumps
- F04D29/542—Bladed diffusers
- F04D29/544—Blade shapes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2220/00—Application
- F05D2220/30—Application in turbines
- F05D2220/32—Application in turbines in gas turbines
- F05D2220/321—Application in turbines in gas turbines for a special turbine stage
- F05D2220/3216—Application in turbines in gas turbines for a special turbine stage for a special compressor stage
- F05D2220/3219—Application in turbines in gas turbines for a special turbine stage for a special compressor stage for the last stage of a compressor or a high pressure compressor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
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- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
A flow control method for reducing loss of a cantilever stator blade front loading design is characterized in that a first-stage compressor model consisting of an embedded third-stage rotor blade and a cantilever stator blade is established and is subjected to grid division, a numerical simulation method is adopted, a Reynolds average NS equation of a design point and a near surge point working condition is solved under an experimental working condition, and a front loading design structure for optimizing the uneven distribution of stator blade loads along chord lengths is obtained through a comparison analysis result. According to the invention, the axial position range of the maximum pressure coefficient difference is determined to be 8% -12%, the change of the blade load from the front edge to the tail edge is effectively controlled, the intensity and the flow loss of the leakage flow are further controlled, and the root loss of the cantilever stator blade at the near surge point is maintained at the design point level.
Description
Technical Field
The invention relates to the technology in the field of impeller machinery, in particular to a flow control method for reducing loss through a cantilever stator blade front loading design.
Background
The pneumatic development of the axial-flow compressor is a key technology for the research and development of an aero-engine. Stator blades of the axial-flow compressor mainly comprise two types, namely shrouded stator blades and cantilever stator blades. Compared with the shrouded stator blade, the cantilever stator blade has the advantages of simple structure, low weight and short axial clearance. The gap leakage flow of the cantilever stator blade can blow off part of low-energy fluid mass in the root corner region, so that the pneumatic performance of the compressor is improved. However, the leakage flow existing in the blade root clearance interacts with the boundary layer of the blade surface and the hub boundary layer, so that the structure of the flow field of the blade root is very complex, and the flow in the corner region of the root has stronger three-dimension and nonlinearity. The loss of the cantilever stator blade mainly comes from the leakage flow in the clearance, and the loss of the cantilever stator blade can be reduced by effectively controlling the strength and the range of the leakage flow.
At present, an aero-engine is developed to a new level, an axial-flow compressor pays more attention to efficient high-load design, and leakage flow loss of a cantilever stator blade becomes one of main influence factors restricting the performance of the aero-engine. Further study has found that the design point of the cantilever vane at the present stage can maintain a low aerodynamic loss level, and the total pressure loss at the root of the cantilever vane rises linearly at the near surge point. The method has the advantages that the reasonable load control method is adopted for the cantilever stator blade to reduce the aerodynamic loss of the root of the cantilever stator blade at a design point and a near surge point, and the method has important significance for improving the performance of an aircraft engine.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a flow control method for reducing loss by adopting cantilever stator blade front loading design, which effectively controls the change of blade load from the front edge to the tail edge by determining that the axial position range of the maximum pressure coefficient difference is 8-12%, further controls the intensity and the flow loss of leakage flow, and maintains the root loss of the cantilever stator blade at the near surge point at the design point level. A geometric modeling and numerical simulation method is adopted, distribution of aerodynamic parameters in a gap of the root of the cantilever stator blade along the chord direction under the working conditions of a design point and a near surge point is given, a root loss coefficient is determined, a proper front loading design scheme is finally given, and loss reduction in the axial flow compressor is achieved.
The invention is realized by the following technical scheme:
the method comprises the steps of establishing a first-stage compressor model consisting of an embedded third-stage rotor blade and a cantilever stator blade, dividing the first-stage compressor model into grids, solving Reynolds average NS equations of a design point and a near surge point under an experimental working condition by adopting a numerical simulation method, and obtaining a front loading design structure with the stator blade load distributed unevenly along the chord length through comparison and analysis results.
The root of the cantilever stator blade adopts a front loading design.
The primary compressor model comprises a cantilever stator blade model which is assembled in the axial compressor model and is designed by front loading and a rotor blade model which is arranged in front of the axial compressor model.
The grid division refers to: the main flow area of the blade channel adopts O4H grid subareas, H-shaped grids are adopted in radial gaps between the main flow area and the wheel disc, and the height of the first-layer grid is set to be 3 x 10 -6 m。
The solving under the experimental condition is as follows: solving a Reynolds average Navier-Stokes equation by adopting a numerical simulation method:
wherein: />Is a conservative parameter vector, is> And &>Is respectively a non-viscosity vector flux and a viscosity vector flux and is based on the relative ratio of the viscosity vector to the viscosity vector> q i Is a heat source term>τ ij Is stressed and is taken>δ ij Is a Crohn's sign, is asserted>Q is the source term> Represents an external force, W f Represents the work done by these external forces>
The comparative analysis result refers to that: carrying out different aspects of comparative analysis on a flow field of a blade root, comprising the following steps: and comparing the distribution of the surface pressure coefficient difference, the total pressure loss coefficient and the circumferential leakage momentum along the chord direction of the blade root profile surface of the stator blade to obtain the circumferential leakage momentum taking the key aerodynamic parameter of the leakage loss of the cantilever stator blade root as the unit axial chord length, and adopting a front loading design to effectively control the leakage loss result within 2 percent of the blade height close to the surge point.
The optimized stator blade chord length design structure is as follows: the front loading design is adopted for 8% -12% of chord length.
Technical effects
The invention integrally solves the problem that the loss of the cantilever stator blade is sharply increased at a near surge point.
Compared with the prior art, the method can realize the optimal design of the optimal axial position of the front loading for reducing the loss under the working condition of the cantilever stator blade at the near surge point, obtain the key pneumatic parameters for determining the loss of the root clearance of the cantilever stator blade, provide a parameter control method for reducing the loss of the cantilever stator blade, is simple and effective, and achieve the aim of reducing the pneumatic loss through passive flow control.
Drawings
FIG. 1 is a schematic view of the computational domain of a compressor rotor blade and a forward-loaded designed cantilever stator blade;
FIG. 2 is a graph showing the difference in surface pressure coefficient of a cantilever stator vane at 2% of the vane height;
FIG. 3 is a schematic view of the chordwise distribution of circumferential leakage momentum per axial chord length within the gap at the root of a cantilever stator blade;
FIG. 4 is a graph illustrating a comparison of 2% tip height total pressure loss coefficient and circumferential leakage momentum distribution along the chord direction at the root of a cantilevered stator blade.
Detailed Description
As shown in fig. 1, in the embodiment, a first-stage compressor model composed of an embedded third-stage rotor blade and a cantilever stator blade is established and is subjected to grid division, a numerical simulation method is adopted, the reynolds average Navier-Stokes equation of the working conditions of a design point and a near-surge point is solved under the experimental working condition, and a front loading design structure with the stator blade load distributed unevenly along the chord length is obtained through the comparison and analysis result.
The root gap of the cantilever stator blade is 0.95mm, namely 1.1% of the blade height.
The grid division refers to: the main flow area adopts O4H grid partition, the sealing cavity adopts H-shaped grids, the height of the first layer of grids is set to be 3 x 10 -6 m。
The solving specifically includes: solving a Reynolds average Navier-Stokes equation by adopting a numerical simulation method:
wherein: />Is a conservative parameter vector, is> And &>Is respectively a non-viscosity vector flux and a viscosity vector flux and is based on the relative ratio of the viscosity vector to the viscosity vector> q i Is a heat source term>τ ij Is stressed and is taken>δ ij Is a Crohn's sign, is asserted>Q is the source term> Represents an external force, W f Represents the work done by these external forces>
As shown in fig. 2, the comparative analysis refers to: the load of the blade root section is measured by the difference of the surface pressure coefficients of the cantilever stator blade with the 2 percent blade height, wherein: coefficient of pressure of blade surface For total pressure at the inlet of the blade channel, p in For static pressure at the inlet of the vane passage, p blade Is the blade surface static pressure. Pressure coefficient difference Δ C p =C p,ps -C p,ss Subscripts ps and ss denote the pressure side and suction side, respectively.
As can be seen from FIG. 2, at 2% blade height, the blade loads at the design and near-tip-to-tip points gradually increase from the leading edge, followed by a gradual decrease in load. The maximum loading position of the near wheezing point is shifted forward from the 12% chord position to the 8% chord position compared to the design point, and the load of the near wheezing point is lower than the design point after 15% chord.
As shown in FIG. 3, the distribution of leakage flow circumferential momentum in the root gap of the front-loaded design cantilevered stator blade in chordwise direction under two conditions is given, and FIG. 4 shows the total pressure loss coefficient of the cantilevered stator blade at 2% blade height below versus the variation of the circumferential leakage momentum distribution along chordwise direction: cantilever stator blade root clearance internal leakage flowρ is density, vn is velocity perpendicular to the mean camber line of the blade, c is chord length, and/or>For inlet flow, r is the radius, subscript hub represents blade root position and casting represents hub position. Circumferential leakage momentum based on unit axial chord length in root gap> μ t Representing circumferential momentum, vt is circumferential velocity, and subscript in is the inlet parameter. Total pressure loss coefficient-> Total pressure at the inlet of the blade channel, p * The total pressure of the channels at different blade heights is the local pressure. The circumferential leakage momentum of the unit axial chord length is taken as an important parameter for judging the leakage loss of the root part of the cantilever stator blade.
As can be seen from FIG. 4, within the first 83% of the axial chord length, the circumferential momentum at the near-surge point is reduced, and the loss of the cantilever stator blade within 2% of the blade height at the near-surge point is lower than the design point, which proves that the key aerodynamic parameter affecting the total pressure loss of the cantilever stator blade is the circumferential leakage momentum. As can be seen from the comparison graph of the total pressure loss coefficient and the circumferential leakage momentum along the chord direction in different blade height ranges, the total pressure loss coefficient increases along with the increase of the circumferential momentum, and hysteresis exists. In the 2% blade height range, the total pressure loss at the cantilever vane design point is 15.4%, while the total pressure loss at the near chunking point is 14.5%. When the cantilever stator blade is changed from a design point to a working condition close to a surge point, the total pressure loss is reduced by 0.9 percent. The circumferential flow of the leakage flow per unit axial chord length of the design point is higher than the near-surge point, and within 2 percent of the blade height, the total pressure loss at the near-surge point is lower than the design point.
The analysis shows that the key aerodynamic parameter determining the leakage loss of the root part of the cantilever stator blade is the circumferential leakage momentum of the unit axial chord length, the leakage loss within 2% of the blade height at the near-surge point can be effectively controlled by adopting the front loading design, the loss level is maintained near the design point, and the total pressure loss at the near-surge point is reduced by 0.9% for the cantilever stator blade of the case. Therefore, the front loading design of 8-12% chord length of the cantilever stator blade is an effective passive flow control means, and the flow loss within 2% of the blade height close to the surge point can be reduced.
Compared with the prior art that only a design point is concerned for controlling the cantilever stationary blade loss, the total pressure loss of the design point can be controlled at a lower level, the total pressure loss of a near surge working condition point is greatly increased, and the understanding of the influence of a root loading mode on the total pressure loss of the root of the cantilever stationary blade is lacked. The invention adopts the design of loading before the root, ensures that the leakage loss at the design point maintains a low level, effectively controls the total pressure loss level at the near surge point, and ensures that the root loss is slightly lower than the design point.
Through specific practical experiments, in the third-stage cantilever stationary blade embedded stage experiment verification of the multistage axial-flow compressor, the cantilever stationary blade adopting the front loading design can effectively control the total pressure loss within 2% of the blade height, and aiming at the cantilever stationary blade of the case, the total pressure loss at a near-surge point is reduced by 0.9% compared with a design point.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (1)
1. A flow control method for reducing loss of a cantilever stator blade front loading design is characterized in that a first-stage compressor model consisting of an embedded third-stage rotor blade and a cantilever stator blade is established and is subjected to grid division, a numerical simulation method is adopted, a Reynolds average NS equation of a design point and a near surge point working condition is solved under an experimental working condition, and a front loading design structure for optimizing the uneven distribution of stator blade load along the chord length is obtained through comparison and analysis results;
the primary compressor model comprises a cantilever stator blade model which is assembled in the axial compressor model and is in front loading design and a rotor blade model which is arranged in front of the axial compressor model;
the root of the cantilever stator blade adopts a front loading design;
the grid division refers to: the main flow area of the blade channel is divided into O4H grids, the radial clearance between the main flow area and the wheel disc is H-shaped grids, and the height of the first layer of grids is set to be 3 x 10 -6 m;
The solving under the experimental condition is as follows: solving a Reynolds average Navier-Stokes equation by adopting a numerical simulation method:wherein:is a conservative type parameter vector of the vector, andrespectively, a non-adhesive flux and a viscous flux,qi is a heat source item and is a heat source item,τ ij is the stress that is applied,δ ij in the case of the kronecker symbol,q is the source term of the signal, represents an external force, W f Representing the work done by these external forces,
the comparative analysis result refers to that: carrying out different aspects of comparative analysis on a flow field of a blade root, comprising the following steps: comparing the distribution of the surface pressure coefficient difference, the total pressure loss coefficient and the circumferential leakage momentum along the chord direction of the blade root profile surface of the stator blade to obtain the circumferential leakage momentum taking the key aerodynamic parameter of the leakage loss of the cantilever stator blade root as the unit axial chord length, and adopting a front loading design to effectively control the leakage loss result within 2 percent of the blade height at the near surge point;
the optimized stator blade chord length design structure is as follows: the front loading design is adopted for 8% -12% of chord length.
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