CN100580258C - A Method of Using Suction to Increase the Load of Compressor Cascade - Google Patents

Abstract

A method of using suction to increase the load on the cascade of the compressor. According to the geometric parameters of the blade surface, the flow field of the cascade is calculated by the computational fluid dynamics method, and the Mach number distribution curve of the blade back is obtained, and the position of the suction peak is determined according to this curve; according to The blade cascade flow field is calculated by the geometric parameters of the blade surface, and the starting position of the blade back separation area is obtained; the blade surface is processed according to the blade surface, and the suction surface of the blade is thinned by one layer; The air section; the width of the air blowing port is selected according to the theoretical and numerical research results; the suction section is arranged at the starting position of the blade back separation area; the width of the suction port is selected according to the theoretical and numerical research results; the extracted gas is pressurized by the booster device from The blowing port blows out; the blowing and inhaling volumes are determined according to theoretical and numerical research results. The invention utilizes the air-blowing combination on the blade surface to control the boundary layer of the blade surface, weakens the separation area of the air flow on the suction surface of the blade caused by the excessive camber of the blade, thereby greatly increasing the load of the blade and reducing the loss coefficient.

Description

A Method of Using Suction to Increase the Load of Compressor Cascade

technical field

The invention relates to the design of high-load fans and compressor blades in modern aero-engines, especially a method for increasing the load of compressor blade cascades.

Background technique

The requirement of high-performance aeroengine for the compression system is to continuously increase the boost ratio and reduce the size and weight. To achieve this, it is necessary to design fans and compressors with higher and higher single-stage boost ratios and larger loads. machine. At present, there are two main methods to increase the single-stage pressure ratio of the fan and the compressor: the first is to use advanced computational fluid dynamics technology to finely organize the internal flow of the fan and compressor blade channels, and use the bending and sweeping combination technology to control the shock wave Shape and strength, so as to achieve high-load fan and compressor design, this method has greatly improved the performance of aviation fans and compressors in the past two decades, but it does not solve the suction surface of fan and compressor blades The boundary layer is prone to serious separation problems under the condition of strong adverse pressure gradient, so the potential of improving the performance of fans and compressors by this method is not great.

The second type of method is to use new flow control technology to control the flow of the boundary layer, reduce or eliminate the separation of the boundary layer on the suction surface of the compressor blade, and realize the high-load compressor and fan design. Flow control methods are mainly developed in the outflow environment, and have been widely used in the control of wing boundary layer separation, for example. Typical methods mainly include: blade surface pumping or suction to control the boundary layer, leading and trailing edge tangential blowing and suction to control circulation, multi-section airfoil, jet flow and plasma control methods, etc.

The main idea of the method of controlling the boundary layer by pumping or sucking air on the blade surface is to thin the boundary layer or change the profile velocity by pumping the low-velocity fluid in the boundary layer on the blade surface or injecting high-energy fluid into the boundary layer, so that Improve the ability of the boundary layer to resist separation. This method has become one of the hot issues in domestic and foreign research in recent years. "Experimental Investigation of a Transonic Aspirated Compressor, Journal of Turbomachinery," Transactions of ASME, April 2005, Page 340-348, Vol.127 by Schuler B.J. et al. showed that in a blade tip Mach number of 0.7 and pressure ratio of 1.6 The numerical simulation and experimental research results of the flow control of the rotor and stator suction surface of the single-stage fan, the rotor blade tip and the stator blade root using the suction method are that the air suction on the rotor and the stator blade is 1% respectively, and the total suction is 1%. When the amount is 4.7%, the efficiency of the rotor can reach 96%, and the efficiency of the whole stage can reach 90%. Merchant A.A., Drela M., Kerrebrock J.L., et al, "Design and Analysis of a High Pressure Ratio Aspirated Compressor Stage," ASME Paper 2000-GT-619, ASME IGTIConference research obtained a single-stage compressor used in the rotor 4% of the incoming flow is sucked by the suction surface of the stator and the stator, and 3% of the incoming flow is sucked by the hub casing, and the total efficiency can reach 86% when the stage pressure ratio is 3.4.

Some units in China have also carried out research in this area. "One of the influences of BLS on the consistency characteristics of compressor cascades: air intake and position changes" by Chen Fu et al., China Engineering Thermophysics Society, Aerodynamic Thermodynamics of Heat Engines, 2004. For a compressor with a medium consistency, the suction method is used to control the flow at different positions. The principle of determining the best suction position is found, and the conditions of different consistency are compared. The results show that the total pressure loss at low consistency The coefficient is smaller.

To sum up, at present, in the flow control of fans and compressors, the flow control method of simply blowing or sucking air is still adopted. The disadvantage of this method is that the pumping or sucking of air must be completed by complex actuators and the extracted gas cannot Utilization, so that the flow rate is reduced, can not increase the load on the blade and reduce the loss coefficient.

Contents of the invention

The technical problem of the present invention is to overcome the deficiencies of the prior art, provide a combination of air blowing and suction on the surface of the blade to control the boundary layer on the surface of the blade, weaken or even eliminate the separation zone of the airflow on the suction surface of the blade due to the excessive curvature of the blade, thereby The method of increasing the load of the blade and reducing the loss coefficient to a large extent is realized to increase the load of the compressor cascade.

Technical solution of the present invention: utilize suction to improve the method for compressor cascade load, it is characterized in that the steps are as follows:

(1) According to the geometric parameters of the blade surface, such as the consistency of the cascade, the bending angle of the blade shape and the chord length of the blade, etc., the flow field of the cascade is calculated by the computational fluid dynamics method, and the Mach number distribution curve of the blade back is obtained, and the blade is determined according to this curve. Point A of the back suction peak position, which is the highest point of Mach number;

(2) Calculate the cascade flow field according to the geometric parameters of the blade surface, and obtain the starting point B of the blade back separation area;

(3) Process the blade profile according to the blade profile, and thin the profile of the suction surface of the blade, that is, the profile between the suction peak position A of the blade back and the starting position point B of the separation area of the blade back, to form a new Profile AA'B'B, where line segments AA' and B'B represent the blade surface perpendicular to point A of the blade back suction peak position and point B of the starting position point of the blade back separation zone, respectively;

(4) Arrange the blowing section at the line segment AA';

(5) Arrange the suction section at the line segment B'B;

(6) The gas sucked from the suction section at the line segment B'B is pressurized by the booster device and then blown out from the blowing section at the line segment AA'.

The blowing port width of the blowing section in the step (4) is 0.9-1.2% times the blade chord length.

The suction port width of the suction section in the step (5) is 0.9-1.2% times the chord length of the blade.

The blowing volume in the step (6) ranges from 1 to 3% of the total flow, and the suction volume ranges from 1 to 3% of the total flow.

The thinning distance s in the step (3) is 1-2 times of the width of the blowing port or the width of the suction port.

The principle of the present invention: the suction section is arranged at the initial position of the blade back separation area (point B in Fig. 1), which can absorb the low-energy fluid with low velocity inside the boundary layer, thin the boundary layer, and improve the resistance of the boundary layer The ability to reverse pressure gradients to delay or eliminate separation. When the Mach number of the incoming flow is constant, the blowing position and the blowing flow rate are basically unchanged, different suction positions have a great influence on the flow field, resulting in a large change in the performance parameters of the cascade. There is an optimal position for the inlet, which is at the flow separation point. For the flow control method in which the direction of the blowing and suction ports is tangential to the blade profile, after cutting the blade profile, the suction port is perpendicular to the incoming flow. A certain thickness of low-energy fluid in the boundary layer can be sucked in at the same time, so that when the opening of the suction port is at the separation point, on the one hand, the low-energy fluid in the mainstream boundary layer can be sucked in time to make the mainstream fluid reattach to the wall; on the other hand, it can also Make the diffuser section after the suction port not too long, preventing the flow from separating again.

The blowing section is arranged at the position of the suction peak on the back of the blade (point A in Figure 1), and high-energy fluid can be injected into the boundary layer to thin the boundary layer or change the profile velocity distribution, thereby improving the ability of the boundary layer to resist separation ;The gas extracted from point B is blown out from point A after being pressurized by the booster device, thereby realizing zero flow control and avoiding the flow control method of simply blowing or sucking air from where the gas used for blowing comes from and how to extract it. Where does the gas go.

In addition, when the incoming flow velocity and geometric shape are constant (that is, the blowing and suction position is constant), there is a critical value for the air blowing volume. When the air blowing volume is less than this value, the increase of the air blowing volume can make the flow control effect Significant improvement, manifested as a substantial increase in the static pressure boost ratio and a substantial reduction in the loss coefficient; however, when the blowing air flow rate reaches a critical value, the increase in the blowing air volume has very limited improvement on the flow performance, and the cascade's adding capacity is already close to its maximum value. extreme load. During the change of the intake air volume, the static pressure boost ratio, the loss coefficient and the diffusion factor all change very little.

In the present invention, the width of the blowing port is 0.9 to 1.2% of the chord length of the blade, the width of the suction port is 0.9 to 1.2% of the chord length of the blade, the blowing volume is 1 to 3% of the total flow, and the air intake is 1 to 3% of the total flow. The selection principle of the four parameters of 1 to 3% is based on the results of a large number of computational fluid dynamics numerical simulation experiments, that is, to select different above-mentioned parameters as the initial and boundary conditions of the three-dimensional viscous flow field calculation software, and to analyze and compare the impact of the above-mentioned parameters on the control The influence law of the results, and finally the above parameter selection principle was obtained through optimization.

The advantage of the present invention compared with prior art is:

(1) The main disadvantages of existing fan and compressor design techniques for high-load fan and compressor design by finely organizing the flow inside the fan and compressor blade passages are that they do not address the growth of the boundary layer on the suction surface of the blade and are prone to failure under strong adverse pressure gradients. Severe separation problems occur, so the potential for such methods to increase fan and compressor blade loads is limited. However, the present invention adopts the combined method of blowing and suction, and the suction can absorb the low-energy fluid with low velocity inside the boundary layer, thin the boundary layer, improve the ability of the boundary layer to resist the adverse pressure gradient, and delay or eliminate the occurrence of separation . Air blowing can inject high-energy fluid into the boundary layer to thin the boundary layer or change the profile velocity distribution, thereby improving the ability of the boundary layer to resist separation; therefore, both blowing and suction can control the boundary layer. growth, improve the boundary layer’s ability to resist separation, and then achieve the effect of increasing the load on the blade;

(2) The current method of using flow control to increase the blade load mainly adopts the control method of simple air blowing or air suction. It is necessary to solve the problem of where the air source for blowing air is provided, because the aero-engine has very strict weight requirements, so the complicated mechanism (suction or blowing pipeline, air source equipment, etc.) The application of the method is limited. The method adopted in the present invention is to blow out the sucked gas through a pressurizing device, so that the problem of whereabouts of the low-energy fluid and the source of the gas for blowing are solved at the same time, zero flow control can be realized (that is, no external flow is required), and the The complexity of the blowing and suction system is simplified, and the problems of weight increase and failure increase caused by complex mechanisms are avoided.

Description of drawings

Fig. 1 is a schematic diagram of blade type of the present invention;

Fig. 2 is a schematic diagram of the original leaf shape;

Fig. 3a and Fig. 3b are comparison diagrams of isentropic Mach number distribution, in which Fig. 3a is the reference, and Fig. 3b is the combination of blowing and sucking air.

Detailed ways

Taking the NACA0012 airfoil as an example, considering the thin trailing edge of the airfoil, the middle and rear part of the airfoil is thickened according to the requirements of the processing technology and other aspects of the method of controlling the boundary layer by blowing and sucking air. The middle arc adopts a circular arc, and the schematic diagram of the comparison of the blade shape before and after the modification is shown in Figure 1, where the dotted line shows the prototype. The consistency of the cascade is 0.87, the bending angle of the blade shape is 60 degrees, and the chord length of the blade is 113.2mm.

(1) Calculate the flow field of the cascade according to the geometric parameters of the blade surface, such as the cascade consistency, blade bending angle and blade chord length, etc., and obtain the Mach number distribution curve of the blade back, and determine the suction peak position of the blade back according to this curve, that is, Point A in Figure 1 is at 8% of the chord length. The specific calculation process is as follows: using the general three-dimensional viscous flow field calculation method and corresponding calculation software, according to the geometric parameters of the blade surface and the cascade geometric parameters, the planar two-dimensional calculation grid of the cascade and the calculation domain is constructed. Working conditions Set the boundary conditions, and then execute the above calculation software to calculate the internal flow field of the cascade, including the distribution of parameters such as pressure, velocity, and temperature at each point in the calculation area, and the internal flow field of the cascade obtained from the calculation The distribution curve of the blade back Mach number can be extracted from the distribution results;

(2) According to the geometric parameters of the blade surface, the cascade flow field is calculated, and the starting position of the blade back separation area is obtained, that is, point B in Fig. 1 is 73% of the chord length. The specific calculation process is as follows: using the general three-dimensional viscous flow field calculation method and corresponding calculation software, according to the geometric parameters of the blade surface and the cascade geometric parameters, the planar two-dimensional calculation grid of the cascade and the calculation domain is constructed. Working conditions Set the boundary conditions, and then execute the above calculation software to calculate the internal flow field of the cascade, including the distribution of parameters such as pressure, velocity, and temperature at each point in the calculation area. The characteristic data of the blade back separation area can be extracted from the calculated results of the internal flow field distribution of the blade cascade, and the starting position of the blade back separation area can be obtained;

(3) Process the blade profile according to the blade profile, and thin the part of the blade suction surface, that is, between point A and point B in Figure 1; according to the results of a large number of numerical simulation experiments, the thinning method is A The surface of the blade between point B and point B moves a distance s in parallel to the inner direction of the blade along the normal direction of the blade surface, that is, the new surface curve of the blade is parallel to the original surface curve, and the two are separated by a fixed distance s, forming a new blade The surface curve consists of line segment AA', curve A'B', and line segment B'B (Fig. 1), where line segments AA' and B'B are perpendicular to the blade surface at points A and B, respectively. The thinning distance s is 1.5 times the width of the blowing port or the width of the suction port;

(4) Arrange the blowing section at the position of the blade back suction peak calculated in step (1), that is, 8% of the chord length, and the blowing section is arranged on the line segment AA'. According to the basic flow relation of aerodynamics and the optimization selection results of different blowing port widths and positions using the flow field calculation program described in step (1), it is obtained that the blowing port width is 0.96% times the chord length, located on the line segment AA' The middle part, that is, the blowing port is symmetrical to the center of the line segment AA';

(5) Arrange the suction section at the position of the blade back separation area calculated in step (2), that is, the position of 73% of the chord length, and the suction section is arranged on the line segment BB'. According to the basic flow relation of aerodynamics and the optimization selection results of different suction port widths and positions using the flow field calculation program described in step (1), it is obtained that the blowing port width is 1.12% times the chord length, located on the line segment BB 'The middle part (that is, the suction port is symmetrical to the center of the line segment BB';

(6) The gas extracted from point B is blown out from point A after being pressurized by the booster device;

(7) Utilize the calculation result that the flow field calculation program described in the step (1) influences different blowing volumes to draw the blowing volume to be 1.5%;

(8) Using the calculation results of the flow field calculation program described in step (1) on the influence of different inhalation volumes, the inhalation volume is 1.8%.

Implementation Effect: Table 1 Performance Parameter Comparison

Mach number Static boost ratio Airflow loss coefficient Diffusion factor Blow volume Inspiratory volume Benchmark 0.731 1.158 0.0687 0.524 0 0 Blow and inhale 0.729 1.305 0.0128 0.820 1.8% 1.5%

Keep the Mach number in front of the grid basically unchanged, about 0.73. It can be seen from Table 1 that the incoming Mach number is within ±0.2% of the design Mach number. It can be seen from Table 1 that under the condition that the incoming flow velocity is basically the same, the method of blowing and sucking air in the boundary layer can greatly increase the blade load, which is specifically reflected in the relatively large increase in the static pressure ratio of the cascade. 15%, while the maximum diffusion factor can be increased to 0.82; at the same time, the loss coefficient is greatly reduced to 19% of the prototype.

Figure 3 shows the distribution comparison of the isentropic Mach number. It can be seen from Figure 3 that the suction peak at the leading edge of the blade is relatively large, and the maximum Mach number is close to 1.4, which is mainly related to the acceleration of the leading edge. Comparing the Mach number distribution on the entire blade surface, it can be seen that after the flow control is adopted, the change of the Mach number is mainly reflected in two aspects, one is the load increase within the full chord length range. The pressure value changes on the pressure surface and the suction surface are also different at different suction positions. The better the flow control effect, the greater the increase in the load level of the cascade. The increase in load is mainly due to the fact that the airflow can be turned after the flow control is adopted. The second is that the Mach number distribution on the blade suction surface is more reasonable. The Mach number at the rear of the suction surface of the prototype is almost a horizontal straight line. After the flow control is adopted, the Mach number of the suction surface decreases gradually after the suction peak. The main reason is that the prototype has large-scale flow separation at the middle and rear part of the suction surface, and the cascade pressure diffusion capacity at the middle and rear part of the suction surface is lost. The large-scale separation flow of the suction surface has a good inhibitory effect, and can delay or even eliminate the large-scale separation of the suction surface. This point can also be seen from the streamline diagrams in Figures 3a and 3b. The rear flow of the prototype has been severely separated in the middle of the suction surface, forming a large area of low-velocity zone. After adopting the method of blowing and sucking air for flow control, although the separation zone still exists, the separation point moves back obviously, and the range of the low-velocity zone is obviously reduced. When the suction position is at 73% of the chord length, the flow control basically reaches the ideal state, and the low-velocity region only exists near the trailing edge.

Claims (6)

1, a kind of method of utilizing suction to improve air compressor blade load is characterized in that step is as follows:

(1) according to the blade profile geometric parameter, adopt the computational fluid mechanics method to calculate cascade flow field, draw blade back Mach Number Distribution curve, determine blade back suction peak position point A, i.e. Mach number peak according to this curve;

(2) according to the blade profile geometric parameter, calculate cascade flow field, draw blade back separation zone starting position point B;

(3) handle blade profile according to blade profile, with blade suction surface part profile, it is the profile skiving one deck between blade back suction peak position point A and the blade back separation zone starting position point B, form new profile AA ' B ' B, its middle conductor AA ' and B ' B are respectively perpendicular to the blade surface at blade back suction peak position point A point and blade back separation zone starting position point B point place;

(4) locate to arrange blowing section at line segment AA ';

(5) arrange air-breathing cross section at line segment B ' B place;

(6) gas from line segment B ' B air-breathing cross section sucking-off blows out from line segment AA ' blowing section after the supercharging device supercharging.

2, utilization suction according to claim 1 improves the method for air compressor blade load, and it is characterized in that: the inflatable mouth width of the blowing section of described step (4) is 0.9～1.2% times a blade chord length.

3, utilization suction according to claim 1 improves the method for air compressor blade load, and it is characterized in that: the intakeport width in the air-breathing cross section of described step (5) is 0.9～1.2% times a blade chord length.

4, utilization suction according to claim 1 improves the method for air compressor blade load, and it is characterized in that: the air-blowing quantity scope of described step (6) is in 1～3% of total discharge.

5, utilization suction according to claim 1 improves the method for air compressor blade load, and it is characterized in that: the gettering quantity scope of described step (6) is in 1～3% of total discharge.

6, utilization according to claim 1 suction improves the method for air compressor blade load, it is characterized in that: the skiving of described step (3) apart from s be the inflatable mouth width of blowing section or air-breathing cross section the intakeport width 1-2 doubly.

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