CN205639070U - Blade suction surface has broken structure in whirlpool and grooved axial fan in leaf top - Google Patents

Abstract

The utility model discloses an axial flow fan with a vortex crushing structure on the suction surface of the blade and grooves on the top of the blade. A vortex crushing structure is added on the suction surface of the impeller blade near the root, and the top of the blade is processed into an airfoil groove. The gap between the hub and the inner cylinder is equipped with a labyrinth seal structure, and the tail of the suction surface of the guide vane is processed with a rectangular groove, which can suppress the size of the channel vortex in the impeller flow channel and reduce the radial secondary flow; it can hinder the development of the leakage flow and weaken the The leakage flow is mixed with the main flow, thereby reducing the leakage loss at the tip of the blade; it can produce a strong throttling effect, improve the stability of the airflow at the outlet of the impeller, and reduce the leakage of the airflow at the root of the blade; it can well control the guide The thickness of the boundary layer at the blade tail prevents boundary layer separation, suppresses vortex shedding and reduces the frequency of vortex shedding. Through the improvement of different positions of the axial flow fan, the efficiency of this type of axial flow fan is higher, the noise is lower, and it is more energy-saving and environmentally friendly.

Description

An axial flow fan with a vortex breaking structure on the suction surface of the blade and grooves on the top of the blade

technical field

The utility model belongs to the technical field of axial flow fans, in particular to an axial flow fan with a vortex crushing structure on the blade suction surface and slots on the top of the blade.

Background technique

The axial flow fan is a machine that relies on the input mechanical energy to increase the gas pressure and discharge the gas. It is widely used in ventilation, dust extraction and cooling of factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induction of boilers and industrial furnaces; cooling and ventilation in air conditioning equipment and household appliances ; Grain drying and selection; wind tunnel wind source and hovercraft inflation propulsion, etc., have very important applications in various industries of the national economy. According to statistics, the power consumption of fans accounts for about 10% of the country's power generation, and the average power consumption of main coal mines accounts for about 16% of mine power consumption; the power consumption of fans in metal mines accounts for 30% of mining power; The electricity consumption accounts for 20% of its production electricity consumption; the electricity consumption of fans in the coal industry accounts for 17% of the electricity consumption of the coal industry. It can be seen that the status and role of fan energy saving in various sectors of the national economy is of great importance. Due to the high specific speed of the axial flow fan, it has the characteristics of large flow and low total pressure, and occupies an irreplaceable position in these industries.

Therefore, it is very important to design and optimize an axial flow fan with high efficiency, good performance, low noise and energy saving. However, the flow in the axial flow fan is very complicated, mainly reflected in: 1) the three-dimensionality of the flow; 2) the viscosity of the fluid; 3) the unsteadiness of the flow. It is difficult to consider the above three points in the traditional fan design. Even if CFD is used as an auxiliary design in the modern design method, the influence of the above three factors on the performance of the fan cannot be completely controlled. The most critical factor is the viscosity of the fluid. Viscosity does not only affect the blade wake vortices formed at the blade exit edge to satisfy the Kutta-Zhukovsky condition. Due to the viscosity, there will be a viscous boundary layer on the surface of the blade and the surface of the ring wall channel, and there will be a strong interaction between them and the main flow, resulting in the so-called "secondary flow" phenomenon. The secondary flow is the main source of the loss increase and efficiency decrease of the axial flow fan. At the same time, due to the influence of viscosity, there is aerodynamic noise in the axial flow fan. The aerodynamic noise of the axial flow fan is mainly composed of two parts: rotating noise and eddy current noise. If the fan outlet is directly discharged into the atmosphere, there will be exhaust noise.

To sum up, in order to design and optimize an axial flow fan with high efficiency, good performance, low noise and energy saving, it is necessary to control and reduce the secondary flow, control and reduce the thickness of the boundary layer, prevent eddy shedding, or control Vortex formation.

Contents of the invention

The purpose of this utility model is to provide a vortex crushing structure on the blade suction surface and a blade top opening to solve the shortcomings of the existing technology that cannot be well controlled by design and optimization of the boundary layer, secondary flow and eddy current noise in the axial flow fan. The grooved axial flow fan has a vortex crushing structure near the root of the suction surface of the impeller blade, processes the airfoil groove on the top of the blade, adds a labyrinth seal structure between the hub and the inner cylinder, and processes the tail of the suction surface of the guide vane The rectangular groove can suppress the size of the channel vortex in the impeller flow channel and reduce the radial secondary flow; it can hinder the development of the leakage flow and weaken the mixing of the leakage flow and the main flow, thereby reducing the leakage loss at the tip of the blade; It produces a strong throttling effect, improves the stability of the airflow at the outlet of the impeller, and reduces the leakage of the airflow at the root of the blade; it can well control the thickness of the boundary layer at the tail of the guide vane, prevent the separation of the boundary layer, and inhibit the shedding and reduction of the vortex. Frequency of vortex shedding. Through the improvement of different positions of the axial flow fan, the efficiency of this type of axial flow fan is higher, the noise is lower, and it is more energy-saving and environmentally friendly.

The technical scheme of the utility model is as follows: an axial flow fan with a vortex crushing structure on the suction surface of the blade and grooves on the top of the blade, including a net cover, an impeller, a guide vane, an inner cylinder, an outer cylinder, a motor, and a shaft sleeve; The cover is braided with iron wire and fixed on the outer cylinder; it is characterized in that: the impeller includes a hub and blades, the suction surface of the blades has a vortex breaking structure near the root, and the top of the blades is processed into an airfoil groove structure. The gap of the inner cylinder has a labyrinth seal structure; the blade is an airfoil blade designed by the equal circulation isolated airfoil method, the twisting speed decreases with the increase of the variable diameter, the pressure is constant along the radial direction, and the thickness of the blade is distributed The thickness distribution of the four-digit airfoil is the same as that of NACA, the relative thickness of the airfoil is 10%-15%, the number of blades is 5-9, and the blade tip clearance is 1%-2% of the blade height; the upper vortex of the blade is broken structure, the cross-sectional shape is rectangular, the length of the vortex crushing structure is 25%-35% of the chord length of the blade at the location, the width is 1/4-1/3 of the length, and the thickness is 3-8mm. The distance between the tail of the vortex crushing structure is The distance b2 of the trailing edge of the airfoil section is 25%-35% of the chord length b1; The depth of the groove is 3-8mm; the labyrinth seal structure of the gap between the impeller hub and the inner cylinder is composed of rectangular serrations, and there are rectangular serrations on the hub and the inner cylinder, the size and spacing of the serrations are equal, and the number of rectangular serrations on both sides is 4-7 pieces, the distance between the hub and the inner cylinder is 8-15mm, the height of the teeth is 60%-80% of the distance, the width of the teeth is 1/5-1/3 of the height, and the gap between the teeth is the tooth height 1/8-1/5 of the guide vanes; the guide vanes are fixed on the inner cylinder and the outer cylinder, the guide vane blades are arc plate-shaped blades, and the number of guide vanes without twisting along the radial direction is 7-17. The thickness of the guide vane is 2-4mm, and there is a rectangular groove at the tail of the suction surface near the trailing edge of the guide vane; the rectangular grooves on the suction surface of the guide vane are evenly distributed on the trailing edge of the suction surface, the size is equal, and the distance from the trailing edge of the guide vane is the same. The length of the rectangular groove is 20%-30% of the root chord length of the guide vane, the depth of the rectangular groove is 1/3-1/2 of the thickness of the guide vane, the width of the rectangular groove is the same as the thickness of the guide vane, and the rectangular groove The distance from the trailing edge of the blade is 3%-5% of the root chord length of the guide vane, and the number of rectangular grooves is 5-10; the motor is a three-phase asynchronous motor, and the motor is fixed on the web of the inner cylinder. The impeller is connected with the motor shaft through the shaft sleeve.

The beneficial effects of the utility model:

In the utility model, by adding a vortex breaking plate near the root of the blade suction surface of the axial flow fan impeller, a channel vortex close to the blade root can be shredded, the size of the channel vortex can be suppressed, and the secondary vortex caused by radial force imbalance can be reduced. The secondary flow is also beneficial to control the thickness of the boundary layer on the suction surface;

The utility model can effectively improve the performance of the fan by opening airfoil grooves on the top of the blade of the axial flow fan. The structure of the grooved blade top disturbs the distribution of the leakage flow field in the gap, and the vortex gradient and disorder in the gap increase significantly, hindering The development of the leakage flow is weakened, and the mixing of the leakage flow and the mainstream is weakened, thereby reducing the leakage loss at the tip of the blade and improving the efficiency of the fan;

The utility model adds a labyrinth sealing structure to the gap between the hub of the axial flow fan and the inner cylinder, the structure can produce a strong throttling effect, play the role of non-contact sealing, improve the stability of the airflow at the outlet of the impeller, and reduce the airflow. Leakage, reduce volume loss, improve efficiency;

The utility model can well control the thickness of the boundary layer at the tail of the guide vane by adding a rectangular groove near the rear part behind the suction surface of the guide vane of the axial flow fan, prevent the separation of the boundary layer, suppress the shedding of the mine and reduce the loss of the vortex shedding Frequency, as a whole, reduces energy loss and suppresses eddy noise due to guide vane wake.

Through the improvement of different positions of the axial flow fan, the efficiency of this type of axial flow fan is higher, the noise is lower, and it is more energy-saving and environmentally friendly.

Description of drawings

Fig. 1 is a three-dimensional view of the axial flow fan of the present invention.

Fig. 2 is a partially enlarged view of the gap labyrinth sealing structure of the present invention.

Fig. 3 is a three-dimensional view of the impeller of the present invention.

Fig. 4 is a schematic cross-sectional view of the vortex crushing structure of the present invention.

Fig. 5 is a structure diagram of the blade top groove of the utility model.

Fig. 6 is a schematic diagram of the structure of the guide vane blade of the present invention.

Fig. 7 is a schematic diagram of the groove on the suction surface of the guide vane of the present invention.

Fig. 8 is a schematic diagram of the section design of the blade airfoil of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

As shown in Figure 1, the axial flow fan consists of 7 parts, including 1. impeller, 2. guide vane, 3. outer cylinder, 4. inner cylinder, 5. motor, 6. shaft sleeve, 7. net cover; The cylinder 3, the guide vane 2 and the inner cylinder 4 are fixed together by welding, and the motor 5 is fixed on the web of the inner cylinder 4. The working parameters of the motor 5 are 720r/min, and the power is 4KW; the impeller 1 passes through the shaft sleeve 6 It is fixed on the shaft of the motor 5, and the gap between the hub of the impeller 1 and the inner cylinder 4 is 10mm; the net cover 7 is installed on the outer cylinder 3, and has the functions of rectifying and preventing foreign matter from entering.

As shown in Figures 1 and 3, the impeller 1 is driven by a motor 5 to do work on the gas, increasing the dynamic pressure and static pressure of the gas. The blades 1-2 on the impeller 1 are airfoil blades designed by the isocircumference isolated airfoil method. The torsional speed decreases with the increase of the variable diameter, the pressure is constant along the radial direction, the relative thickness of the blade is 10%, the number of blades is 6, and the blade tip clearance is 2% of the blade height. The specific method of impeller blade design is as follows:

The simple radial balance equation of the fluid inside the axial flow fan:

Among them, P represents the pressure on the fluid microcluster, Cu is the speed of the fluid microcluster rotating around the axis, and r is the radius of rotation of the fluid microcluster. The formula indicates that assuming that there is no radial flow inside the axial flow fan, the pressure P received by the fluid cluster at any position in the radial direction is balanced with the centrifugal force generated by the rotational movement of the fluid cluster.

In formulas (2)-(3), Pt is the total pressure of the gas, ρ is the density of the gas, C is the total velocity of the gas, Cu, Ca, and Cr are the circumferential velocity, circumferential velocity, and radial velocity of the gas, respectively. Speed, but with the above assumptions, it can be seen that Cr=0, the total pressure of the gas is equal to the dynamic pressure plus the static pressure.

From the formulas (2)-(3), the differential relations of Pt, P, Cu, and Ca can be obtained as the formula (4). Substituting the formula (4) back into the formula (1) can get another more general and simple The radial balance equation (5).

The equal circulation design method assumes that the total pressure Pt is constant along the radial direction, and the axial velocity Ca is also constant along the radial direction. Substituting it into formula (5), we can know:

It can be seen from the above formula that the equal circulation design method assumes that Cr=0 inside the fan, and the total pressure Pt is constant along the radial direction, the axial velocity Ca is also constant along the radial direction, and the circumferential velocity decreases with the increase of the radius. Small.

Equation (7) is derived from the cascade theory, a , blade twist speed , cascade lift coefficient , and the average relative velocity in the cascade The relationship between.

The isolated airfoil design method assumes that the lift coefficient of the cascade No interference from the blades between the cascades, which is the lift coefficient of the cascades lift coefficient of an isolated airfoil same.

The design method of isocircumference isolated airfoil is as mentioned above, through the above method, the chord length and installation angle of each section of the blade can be calculated, and the blade inlet airflow machine and the blade outlet airflow machine can be calculated from the above parameters plus some experience The shape of the mid-arc can be calculated by the formula, and the relative thickness of the airfoil is taken as 10%. Then, the NACA four-digit airfoil thickness distribution is superimposed on the mid-arc of each section to obtain each airfoil section. NACA airfoil is an airfoil series published by the National Advisory Committee for Aeronautics. The four-digit airfoil is its commonly used airfoil series. The design method is as follows:

The NACA four-digit airfoil thickness distribution function equation is:

Where: t represents the relative thickness, , b is the chord length, the airfoil black line is the X axis, and the coordinate origin is placed on the leading edge point of the airfoil blade, .

The method is as follows, first, take the relative thickness as 10%, and obtain N discrete points of the thickness distribution function of different sections of the blade , and then, at the same time, the arcs in each section are equally divided to obtain N discrete points , and calculate the slope of the normal line at each point by difference method, and then calculate the inclination angle , so that the coordinate points of the upper and lower surfaces of the transformed airfoil can be obtained Then connect the required airfoil with curves smoothly, as shown in Figure 8, a1 is the thickness distribution function, a4 is the mid-arc of the blade, a2 and a3 are the normal and tangent of any point on the mid-arc .

As shown in Fig. 2, it is a labyrinth seal structure A between the hub 1-1 and the inner cylinder 4-1. The labyrinth sealing structure A consists of two parts, including: a rectangular sawtooth structure on the hub 1-1 and a rectangular sawtooth structure on the inner cylinder 4-1. The size and spacing of the saw teeth are equal, the number of saw teeth on the hub 1-1 is 5, the number of saw teeth on the inner cylinder is 4, the distance d1 between the hub and the inner cylinder is 10mm, the height d4 of the teeth is 72% of the gap, and the size is 7.5mm, the width d3 of the sawtooth is 1/3 of the height, the size is 2.5mm, and the gap between the sawtooth is 1mm;

As shown in Figures 3 and 4, there is a vortex breaking structure 1-3 near the blade root on the suction surface of the blade 1-2. The cross-section shape of the vortex crushing structure is rectangular. The length of the vortex crushing structure 1-3 is 30% of the chord length b1 of the blade at the location, the size is 80mm, the width b3 is 37.5% of the length, the size is 30mm, and the thickness is 3mm. The distance b2 between the tail of the airfoil and the trailing edge of the airfoil section is 30% of the chord length b1, and the size is 80mm;

As shown in Figures 2 and 5, there is an airfoil groove structure 1-4 on the top of the blade 1-2, and the shape of the blade top airfoil groove 1-4 is completely similar to the shape of the blade top section, and the blade top section is reduced by 0.9 times to obtain , the depth of the airfoil groove is 4mm;

As shown in Figures 6 and 7, the guide vanes 2 are fixed on the inner cylinder 4 and the outer cylinder 3. The guide vanes 2 are arc plate-shaped blades, and the number of guide vanes without twisting along the radial direction is 9. The guide vanes 4 The guide vane 2 with a thickness of 4mm has a rectangular groove 2-1 at the tail of the suction surface near the trailing edge; 2 trailing edge distance is the same, the length of the rectangular groove 2-1 is 25% of the root chord length C4 of the guide vane 2, the size is 80mm, the depth of the rectangular groove 2-1 is 1/2 of the thickness of the guide vane 2, the rectangular groove The width of the groove 2-1 is 4mm the same as the thickness of the guide vane 2, the distance C3 between the rectangular groove and the trailing edge of the blade is 5% of the chord length C4 of the blade root of the guide vane 2, the size is 15mm, and the number of rectangular grooves is 9 .

The utility model first adds a vortex crushing structure 1-3 near the root of the suction surface of the blade 1-2 of the impeller 1, because the installation angle of the blade root is large, the blade is seriously twisted, and it is also affected by the boundary layer of the hub, which is very easy Boundary layer separation occurs under the influence of channel vortices, resulting in large energy losses. This structure can chop up a channel vortex close to the blade root, suppress the size of the channel vortex, reduce the secondary flow caused by radial force imbalance, and help control the thickness of the boundary layer on the suction surface. The formation mechanism of the channel vortex is that in the flow field of the impeller 1, the kinetic energy of the airflow in the mainstream area is large, and the static pressure obtained by the conversion of kinetic energy near the pressure surface of the blade 1-2 is high, while the kinetic energy of the airflow in the boundary layer of the end wall area is small , the static pressure obtained by kinetic energy conversion near the pressure surface of the end wall is low, so the airflow near the pressure surface of the blade 1-2 will flow from the middle area of the blade with high static pressure to the end wall area of low static pressure, occupying the end wall area. The air flow channel at the wall, and flows along the end wall to the corner area of the suction face with lower static pressure, where it rolls up and forms a vortex flow across the entire cascade channel. This is the channel vortex, which is characterized by appearing in pairs, with opposite rotations, and the upper and lower parts roughly account for half of the cascade channel. Then open the airfoil groove 1-4 on the top of the blade 1-2. The proper groove length can effectively improve the performance of the fan. The grooved blade top structure 1-4 disturbs the distribution of the leakage flow field in the gap, and the vorticity in the gap Gradient and chaos increase significantly, which hinders the development of leakage flow and weakens the mixing of leakage flow and mainstream, thereby reducing the leakage loss at the tip of the blade and improving the efficiency of the fan. Then the gap between the hub 1-1 and the inner tube 4-1 is added with a labyrinth seal structure A, which can produce a strong throttling effect and play the role of non-contact seal, improve the stability of the airflow at the outlet of the impeller, and reduce the airflow Leakage, reduce volume loss, improve efficiency. The internal mechanism of the sealing structure A is that after the air flow enters the annular cavity through the sealing gap, it suddenly expands to generate a strong vortex, so that most of the energy of the air flow is converted into heat and dissipated, so that the enthalpy value returns to the value close to the value before the gap. Only a small part of the kinetic energy still enters the next gap at the remaining speed, and the above process is repeated step by step. At this time, the gas pressure drops step by step, so as to achieve the sealing effect. Finally, a rectangular groove 2-1 is added near the rear part of the suction surface of the guide vane 2. The reason for adding this structure is that the guide vane 2 is not only affected by its own boundary layer, but also affected by the wake interference of the front impeller 1. Because the flow of gas in the impeller 1 is very complicated, the air flow angle at the inlet of the guide vane 2 fluctuates greatly in the radial and circumferential directions, the fluid is very unstable in the flow channel of the guide vane 2 and the boundary layer of the suction surface is thicker than the boundary layer of the pressure surface more, leading to more complex flow on the suction surface, and as the fluid moves from the leading edge to the trailing edge of the guide vane, the boundary layer continues to thicken, and the fluid is easily separated at the tail of the suction surface of the guide vane, forming a vortex, causing serious damage Energy loss and wake vortex shedding noise. The function of the groove 2-1 at the tail of the guide vane 2 is to well control the thickness of the boundary layer at the tail of the guide vane 2, prevent the separation of the boundary layer, suppress the shedding of mine and reduce the frequency of vortex shedding. Overall, the energy is reduced Loss, suppression of eddy current noise caused by guide vane wake. Through the improvement of different positions of the axial flow fan, the efficiency of this type of axial flow fan is higher, the noise is lower, and it is more energy-saving and environmentally friendly.

Claims (1)

1. An axial flow fan with a vortex crushing structure and blade top slots on the suction surface of the blade, comprising a net cover, an impeller, a guide vane, an inner cylinder, an outer cylinder, a motor, and a shaft sleeve; It is fixed on the outer cylinder; it is characterized in that: the impeller includes a hub and blades, the suction surface of the blade has a vortex breaking structure near the root, the top of the blade is processed into an airfoil groove structure, and there is a labyrinth in the gap between the impeller hub and the inner cylinder Sealing structure; the blade is an airfoil blade designed by the equal circulation isolated airfoil method, the torsion speed decreases with the increase of the variable diameter, the pressure is constant along the radial direction, and the blade thickness distribution is the same as that of the NACA four-digit airfoil The thickness distribution of the airfoil is the same, the relative thickness of the airfoil is 10%-15%, the number of blades is 5-9, and the blade tip clearance is 1%-2% of the blade height; the upper vortex crushing structure of the blade has a rectangular cross-sectional shape The length of the vortex crushing structure is 25%-35% of the chord length of the blade at the location, the width is 1/4-1/3 of the length, and the thickness is 3-8mm. The distance between the tail of the vortex crushing structure and the trailing edge of the airfoil section The distance b2 is 25%-35% of the chord length b1; the shape of the blade top airfoil groove structure is the same as that of the blade top section and reduced in proportion, the reduction factor is 0.95-0.8, and the airfoil groove depth is 3-8mm ; The labyrinth seal structure of the gap between the impeller hub and the inner cylinder is composed of rectangular sawtooth, there are rectangular sawtooth on the hub and the inner cylinder, the size and spacing of the sawtooth are equal, the number of rectangular sawtooth on both sides is 4-7, the hub The distance between it and the inner cylinder is 8-15mm, the height of the sawtooth is 60%-80% of the distance, the width of the sawtooth is 1/5-1/3 of the height, and the gap between the teeth is 1/8-1 of the tooth height /5; the guide vanes are fixed on the inner cylinder and the outer cylinder, the guide vane blades are circular arc plate blades, the number of guide vanes without twisting along the radial direction is 7-17, and the thickness of the guide vane blades is 2-4mm , there is a rectangular groove at the tail of the suction surface near the trailing edge of the guide vane; the rectangular grooves on the suction surface of the guide vane are evenly distributed on the trailing edge of the suction surface, the size is equal, and the distance from the trailing edge of the guide vane is the same, and the length of the rectangular groove is 20%-30% of the chord length of the blade root, the depth of the rectangular groove is 1/3-1/2 of the thickness of the guide vane, the width of the rectangular groove is the same as the thickness of the guide vane, and the distance between the rectangular groove and the trailing edge of the blade It is 3%-5% of the root chord length of the guide vane, and the number of rectangular grooves is 5-10; the motor is a three-phase asynchronous motor, the motor is fixed on the web of the inner cylinder, and the impeller is connected to the motor through the bushing Axes are connected.