KR100719103B1 - Hybrid Design Method for High-efficient and Low-Noise Multiple-sectioned Impeller of Backward-bladed Turbo Blower - Google Patents

Abstract

The present invention relates to a design method and a low noise implementation method of a turbo-type rear-wing three-dimensional impeller used in a centrifugal blower (fan) or a scrollless plenium blower (fan), in particular, the three-dimensional impeller and two-dimensional impeller unit shroud and back plate It combines in the middle height of to overcome the difficulty of manufacturing the injection mold of the three-dimensional impeller to achieve high efficiency, and also to reduce the low noise and load noise after applying the lean angle corresponding to 2.5 dimensions in the low noise method Design method, the rear curvature has more than one curvature radius other than the curvature on the rotating surface so that lift fluctuation caused by the vortex generated in the rear stage is amplified, and the noise emitted from the rear stage is canceled near the rear stage to make noise emission. Backward curvature design method to weaken, phase of vortex at the low and high point of tooth-shaped rear end is 360˚ Or, it is a multiple of it, and the toothed rear design method for reducing the rear noise by canceling the vortex and the curvature of the leading edge of the shroud inlet are adjusted to adjust the vane pass frequency of the turbofan and its harmonic frequency noise. The present invention relates to a method of realizing low noise by combining a method of designing curvature of the leading edge and the like.

Blower, multiple impeller, turbo type, rear wing, high efficiency, low noise design, rear noise

Description

Hybrid Design Method for High-efficient and Low-Noise Multiple-sectioned Impeller of Backward-bladed Turbo Blower}

1 is an explanatory diagram of an exit velocity triangle and velocity components of the rear wing.

2 is an explanatory diagram of the configuration and design parameters of the multiple impeller.

3 is a velocity triangle view of the three-dimensional impeller inlet of the multiple impeller components.

4 is a block diagram of a hybrid design embodiment according to the configuration and design of FIG.

5 is a low noise design embodiment according to the method of applying a lean angle (Lean Angle) and the lean angle (Lean Angle) 2.5D design.

Figure 6 is a block diagram of a low noise design embodiment through the rear end curvature design generated by different blower wake voltage distribution.

7 is an embodiment of a serrated rear end design and low noise design for offsetting turbo fan rear end (Vortex).

8 is a configuration diagram of a front edge curvature design low noise design embodiment to adjust the curvature of the leading edge (Leading Edge) of the shroud inlet to reduce the blade passing frequency and the harmonic frequency noise of the turbofan.

9A and 9B are exemplary graphs of frequency spectra of measured noise for a conventional turbo impeller and a leading edge curvature design low noise design impeller.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a design method and a low noise implementation method of a turbo type rear-wing three-dimensional impeller used in a centrifugal blower (fan) or a scrollless plenium blower (fan). In particular, the three-dimensional (3D) impeller portion and two-dimensional (2D) ) The impeller part is combined at the middle height of the shroud and the rear plate to overcome the difficulty of manufacturing the injection mold of the three-dimensional impeller and to achieve high efficiency. Also, the low-noise method employs a lean angle of 2.5 dimensions. Design method for reducing trailing noise and load noise, making the trailing curvature have more than one curvature radius other than the curvature on the rotating surface so that lift fluctuation caused by the vortex occurring in the rear stage is amplified and the noise emitted from the rear stage is near Design of the Backward Curvature to Offset the Noise Radiation by Offset at, and the Phases of the Vortex at the Low and High Points Tooth-shaped rear end design method to reduce rear end noise by canceling Vortex by 360 ° or multiples thereof, and shroud (top plate) of leading edge of shroud inlet It relates to a method for realizing low noise by adjusting the curvature of the inlet) by combining the blade passing frequency of the turbo fan and the leading edge curvature design method for reducing the harmonic frequency noise thereof.

As is well known, the research on the aerodynamic design of fans or blowers has continued for decades and many advances have been made in design techniques.

Recently, however, the demand for noise as well as performance has increased and the production cycle of products has been shortened, requiring the development of higher level design means.

In addition, in advanced societies where noise sources are generated as the industrial society's technology develops day by day, the improvement of human needs for noise sources varies according to noise sources, and the level is gradually increasing.

While efforts to improve the performance of blowers (fans) applied to industrial, automotive, office equipment, and home appliances have made some progress, many attempts have been made to reduce noise. It is even more difficult to evaluate the contribution of the company and its design.

The turbo fan belongs to a low-speed fan among the fans, has a relatively high flow resistance and relatively low rotational speed, and has a relatively high flow resistance and low noise environment, as in a fan filter unit, which is part of a clean room facility of a semiconductor factory. This applies if required. In general, centrifugal turbofans have an impeller composed of a rear wing, and the main design variables include airfoil lengths (C), wing thickness (t), and number of wings (Z). ( β ₁ ), exit angle ( β ₂ ), inlet height (b ₁ ), outlet height (b ₂ ). Therefore, the turbofan impeller is represented by a two-dimensional shape in which two-dimensional wings are stacked in the height direction.

Also, in fluid machinery that requires a very high pressure, such as in compressors, centrifugal turbo impellers are not stacked in two-dimensional planes from the back plate to the front shroud. Impeller is used. In other words, the two-dimensional impeller has a flat stream surface around the wing, while the three-dimensional impeller has a curvature of the stream surface around the wing, and the wing inlet flow is in the rotational axis direction and the wing outlet flow is in the radius. Direction in general.

However, in recent years, the application of an impeller having a three-dimensional shape has been attempted as a turbo fan of high efficiency and low noise is required. However, since the impeller used in the centrifugal compressor cannot be injection molded, a design technique of a three-dimensional impeller that can overcome this is necessary. Do. The three-dimensional impeller used in the pump or the compressor is formed by combining the inducer portion that guides the flow from the inlet and the centrifugal blade portion in which the pressure rise of the fluid is made. It is more efficient than ordinary two-dimensional impeller because it guides the flow from the inlet of the impeller and the blade is designed to be suitable for the velocity distribution in each section.

Accordingly, the present invention is to solve the three-dimensional impeller application problem and the low noise problem according to the demand for high efficiency of the turbo blower (fan), the three-dimensional impeller portion and the two-dimensional impeller portion in the middle part of the shroud and the back plate as a design method of the impeller To overcome the difficulties of manufacturing the injection mold of the three-dimensional impeller by combining in to achieve high efficiency, and also by applying the lean angle corresponding to 2.5 dimensions in a low noise method, the design method of the rear noise and load noise reduction, the rear stage The curvature has one or more curvature radii other than the curvature on the rotating surface, so that lift fluctuations caused by the vortices generated at the rear end are amplified, and the rear radiated noise is canceled near the rear end to weaken the noise emission. Curvature design method, Vortex phase is 360˚ at low and high point It is a multiplier to reduce the vortex passing frequency and its harmonic frequency noise of the turbofan by adjusting the design of the toothed rear end through the offset of the vortex and the curvature of the leading edge of the shroud inlet. Its purpose is to provide a curvature design method.

' 에 대하여 각 임펠러의 입구부 높이 비율(x₁), 출구폭 높이 비율(x₂) 및 각 임펠러 입출구각(β₁과 β₂)을 변화시켜가며 3D임펠러를 통과하는 유량'Q₁'과 2D임펠러를 통과하는 유량'Q₂'를 결정하되, 두(2D,3D) 임펠러가 자연스럽게 연결되도록 두 임펠러의 입출구각이 일치하며(

) 두 임펠러 연결선에서의 두 임펠러 면의 수직벡터가 일치하도록 하는 것을 특징으로 한다.In order to achieve the above object, the present invention provides a turbo-type rear wing three-dimensional impeller used in a centrifugal blower (fan) or a scrollless plenium blower (fan),
In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans),
Designed to satisfy the desired pressure distribution function by combining a general two-dimensional rear wing impeller and a high pressure three-dimensional impeller to satisfy a given performance (flow, pressure)

'Q ₁ ' and the flow rate through the 3D impeller with varying inlet height ratio (x ₁ ), outlet width height ratio (x ₂ ) and inlet / outlet angles (β ₁ and β ₂ ) of each impeller with respect to Determine the flow rate 'Q ₂ ' through the 2D impeller, but the entrance and exit angles of the two impellers coincide so that the two (2D, 3D) impellers are connected naturally (

The vertical vectors of two impeller faces at two impeller connecting lines are coincident with each other.

delete

In addition, the present invention is the intermediate form of the two-dimensional centrifugal blades and the three-dimensional blades used in the centrifugal compressors, the blades are not laid straight from the base plate to the shroud, but lying obliquely, the shape of the 2.5-dimensional blades is two-dimensional Compared to blades designed with a lean angle (with the wing lying outward (θ)), it has a coplanar profile, and the rear end is based on the outlet width direction (the direction perpendicular to the impeller back plate at the wing exit). It is inclined to reduce the rear noise and at the same time to reduce the load noise. In this case, the lean angle θ is characterized by having an angle within 20 ° so that the inlet of the pressure surface is not blocked.

Also, the tooth height (H) should not exceed 10% of the cord length (straight distance from the inlet to the outlet) of the tooth so that the vortices of the same frequency occur at the tooth surface formed at the rear end of the wing. The pitch P of vortex flows in the same phase by making it smaller than the correlation distance of the trailing vortex flow (distance Lc in the direction perpendicular to the streamline in which the vortices are considered to have the same phase). It occurs at least at the sawtooth mountain. In this case, the height H of the mountain is characterized in that the length of the vortex period having the same sign (+,-) direction of the vortex becomes an integer multiple.

In addition, the rear curvature formed on the impeller blade has one or more curvature radii other than the curvature on the rotating surface so that lift fluctuations caused by the vortices generated at the rear end are amplified so that noises emitted from the rear end are canceled near the rear end. It characterized by reducing the rear end noise.

In addition, in order to reduce the vane passing frequency and the harmonic frequency of the turbofan, the blade shroud leading edge of some blades is bent in the pressure plane direction, and the shroud inlet leading edge of some blades is in the negative pressure surface direction. The remaining edges of the remaining blades are characterized by reducing the noise level at the wing passing frequency and its harmonic frequency as compared to the existing frequency spectrum by maintaining the torque balance by maintaining the existing state.

Hereinafter, with reference to the accompanying drawings of the present invention will be described.

In general, the dimensionless variables to be considered when designing a turbo fan include the pressure and flow coefficients that have pressure and flow rate as impeller diameter D ₂ and the rotation speed N as shown in the following Equation 1, and the rotation speed and diameter as the amount of voltage increase. Δp _t and the air volume Q have dimensionless specific velocity and specific diameter.

The specific speed is a dimensionless variable that represents a specific fan, and is an important variable that is often used to compare fan characteristics, type, impeller selection, and comparison between the same fan type. If the specific speed is large, the fan has a higher air volume than the pressure increase, and if the specific speed is small, the pressure increase of the fan is high compared to the air volume. In addition, the impeller with a large specific speed has a wider impeller outlet width than the outlet diameter, and the impeller with a small specific speed has a narrow outlet width. In the case of centrifugal impellers, the specific speed is about 100 to 1000. In the case of 100 to 400, the specific speed is relatively low, and the main speed is mainly 400 to 700. Specific diameter (δ) can be used as a good measure of the size (diameter) of the impeller in the design.

The pressure rise of the impeller and the work by Euler equation have the following relationship.

은 임펠러의 효율로서 내부 유동에 의한 전압 손실량에 대한 퍼센트(%)이다.here

Is the efficiency of the impeller as a percentage of the voltage loss due to internal flow.

Therefore, assuming the efficiency of the impeller, the velocity component ( C _{θ 2} ) at the impeller outlet can be obtained and the impeller outlet diameter can be determined.

In general, the flow from the impeller does not flow along the exit wing and slip occurs, so the exit wing angle should be larger than the flow angle.

이 되며 다음으로부터 출구 날개각도를 다음 식3과 같이 계산할 수 있다.If the slip coefficient is μ when the angle is β _2b ,

From this, the exit blade angle can be calculated as

The slip coefficient is expressed using the following equation (4) using the Strodola equation.

FIG. 1 is a block diagram of the present invention of the multiple hybrid lead impeller design method. In other words, based on the basic input part of the designer (flow rate, total pressure, rotational speed, etc.), the turbo impeller is a combination of a general two-dimensional (2D) rear wing impeller and a high-pressure three-dimensional (3D) impeller to satisfy the desired pressure distribution function. The width height ratio (x ₁ ), the exit width height ratio (x ₂ ), and the pseudo inlet diameter (D ₁ ) of the three-dimensional impeller are obtained to satisfy the following equations (5) and (6).

가 되고,For example, the increase in voltage force at design point (△ p _t ) is 20mmAq, the flow rate ( Q ₀ / is 45cmm, and the rotation speed (N) is 1,030rpm, and the geometric variables D ₀ , D ₁ , D ₂ , b ₁ , b ₂ is given by 0.263m, 0.315m, 0.485m, 0.098m, 0.076m, respectively,

Become,

가 된다.

Becomes

In addition, when the ratio of the exit width height (x ₂ ) to the ratio (W ₄ / W ₂ ) of the inlet and outlet relative speeds of the lower two-dimensional (2D) impeller shown in FIG. 2 is about 0.7, the following equation 7 is obtained.

However, since it is derived from the assumption that the previously designed inlet and outlet angles and flow angles used in Equation 7 are the same, the second stage must be designed to take into account the slip between the wing and the flow. That is, C _m2 and C _θ2 are obtained based on the exit wing angle obtained in step 1, and then the exit flow angle (β ₂ ^* ) is obtained by substituting the equation Slip Factor together with the U ₂ value. The width height ratio (x ₂ ) is obtained.

을 구한 후, 3차원 임펠러 입구속도 중 입구 날개선에 수직인 성분인 C ₁ 을 구하면 다음과 같다.In addition, assuming uniform axial velocity over the entire impeller inlet area,

After obtaining, the component C _1, which is a component perpendicular to the inlet wing line, is obtained as follows.

이다. 3D 임펠러의 입구 전연부(Leading Edge)에 대한 속도삼각형은 도 3에 나타난 속도벡터에 대하여, 입구부 중 z=x₁b₁과 z=b₁ 에서의 입구날개각 (β₁)의 분포를 구하면 다음과 같다.in this case,

to be. The velocity triangle of the inlet leading edge of the 3D impeller shows the distribution of the inlet blade angle (β ₁ ) at z = x ₁ b ₁ and z = b ₁ of the inlet for the velocity vector shown in FIG. Obtained as follows.

5 shows an exemplary design of the impeller shape obtained by applying the double impeller lower lid design method.

In addition, in the case of the two-dimensional impeller, the same flow rate does not flow along the space between the rear plate and the front plate, and a relatively large flow rate is mainly formed in the vicinity of the rear plate. As shown in FIG. 1, in order to compensate for the voltage change caused by the change in the absolute speed C ₀ in the rotational direction according to the change in the radial absolute speed C _m , the change in the blade width direction of the blade exit angle β _2b . Will be needed.

The operating Mach number of most blowers is 0.1 to 0.3 and can therefore be assumed to be incompressible flow. Inflow of the flow into the wing is inevitably uneven due to the wake of the installed structure, and thus abnormal flow around the wing contributes to noise emission. In addition, the boundary layer around the wheels is mainly a turbulent boundary layer, resulting in very strong noise radiation at the trailing edge. Accordingly, noise in a turbo fan is classified into inflow-turbulence noise, trailing edge noise, inflow vortex noise, and blunt-trailing edge noise.

배 만큼 원거리 강도가 증가한다. 여기서 r_o는 임펠러 후단으로 부터의 거리이며, 소음파장에 비해 훨씬 짧다고 가정된다. 또한 소음강도는 유동속도의 5승에 그리고 난류강도의 제곱, 후단 경계층두께 및 횡방향 상관거리에 비례하게 된다.Among the noise components, however, the most influential factor on the turbo fan noise is the trailing edge noise, and the turbulent flow around the impeller does not radiate much by sound. do. This model of trailing-edge noise was first developed by Ffowcs Williams and Hall in 1970 and according to them, both vertical and lateral quadrants perpendicular to the trailing edge.

Increases ranged strength by twice. Where r _o is the distance from the rear of the impeller and is assumed to be much shorter than the noise wavelength. The noise intensity is also proportional to the power of the flow rate and to the square of the turbulence intensity, the trailing boundary layer thickness, and the transverse correlation distance.

Also, the loading acting on the blades is the radial cause of the fan noise. The most dominant of the unsteady load noises in the rotational direction and the axial direction is the noise due to the load in the rotational direction.

In the present invention, as a middle form of a general two-dimensional centrifugal blade and a three-dimensional blade (blade) used in the centrifugal compressor, the blade is not lying straight from the base plate to the shroud, but is lying at an angle, and the shape of the 2.5-dimensional blade is 2 Compared with the blade designed in dimensions, the performance is similar because it has the same planar profile except for the Lean Angle, and the rear end is inclined based on the exit width direction, and thus the rear noise is expected to be reduced. Also, as shown in FIG. 5, even when the load applied to the blade is equal to the lean angle, the actual load is reduced as the lean angle θ is increased, but the reduction of the load noise is also expected. However, as the lean angle (θ) increases, the inlet portion of the pressure surface is clogged, and the performance is expected to decrease. Therefore, the use of a lean angle within 20 ° is required.

Unlike the previous increase of the same voltage in the exit width direction, the stroke relative frequency (f = St * W ₂ / in the rear exit width direction is changed by changing the exit relative speed (W ₂ ) to reduce the rear noise. δ) In order to reduce the noise, changing the voltage increase in the outlet width direction while maintaining the average voltage increase required at the design point has a rear end curvature other than the curvature on the blade rotation surface as shown in FIG. The rear curvature formed at this time has one or more curvature radii other than the curvature on the rotating surface, and the lift variation caused by the vortices amplified in the rear stage is amplified so that the noise radiated from the rear stage is canceled near the rear stage so that the noise radiation It has a weakening effect.

Another method of attenuating the rear end noise is to design the rear end of the impeller blade as serrated as shown in FIG. 7 so that the vortices generated at the inclined rear end are directly canceled. ) And the serration height are designed so that the vortices at the rear end are 360 ° or multiples of them at the tooth bottom and the high point, thereby increasing the offset of the vortices at each downstream position, so that the rear noise caused by the rear lift fluctuation It is a way to reduce it. More specifically, the height H of the tooth tooth does not exceed 10% of the cord length so that vortices of the same frequency occur on the tooth surface, and the pitch P of the tooth tooth is smaller than the correlation distance Lc between the trailing end and the shedding flow. Make small, so that shedding of the same phase occurs at least on the sawtooth mountain. The height H of the mountain is designed to be an integer multiple of the periodic length of the vortex of the same sign.

(1) H ≤0.1 × C

(2) P -m × L _c (where m is an integer multiple)

(3)

Where δ ^* is the wake boundary layer exclusion thickness, including the trailing thickness, and St is the number of strokes, with a value between 0.1 and 0.2.

In addition, in order to reduce the blade passing frequency and the harmonic frequency of the turbo fan, as shown in FIG. 8, two leading edges of the shroud inlet part are bent to the pressure side and two to the suction side. In the case of maintaining the torque balance by maintaining the existing state, only the first and second band pass filters (BPF) are shown as compared to the existing frequency spectrum as shown in FIGS. 9A and 9B, and the power is also reduced. It can be seen that.

As described above, in the hybrid design method of the turbo-type rear-wing multi-impeller according to the present invention, the three-dimensional centrifugal impeller including the inducer portion for guiding the flow from the inlet and the blade portion in which the pressure rises of the fluid cannot be manufactured as an injection mold. The high efficiency three-dimensional impeller part and the high wind two-dimensional impeller part are combined at the mid-height of the shroud and the back plate in order to satisfy the restriction condition, the high efficiency condition, and the high air flow condition simultaneously.

In addition, the rear noise and load noise reduction design method applying 2.5-degree lean angle, the vortex generated at the rear end by making the rear end curvature have one or more curvature radius other than the curvature on the rotating surface The method of designing the rear curvature to amplify the lift fluctuation by the amplification and the noise radiated from the rear stage is canceled near the rear stage to weaken the noise emission, and the phase of the vortices at the low and high point of the rear end of the tooth is 360˚ or its multiple To reduce the trailing noise, the design of the toothed trailing end of the rear end noise reduction and the curvature of the leading edge of the shroud inlet are used to reduce the blade passing frequency and the harmonic frequency noise of the turbofan. By combining edge curvature design method, it has the effect of achieving lower noise than the existing turbofan.

It is apparent to those skilled in the art that the present invention is not limited to the embodiments described and that various modifications and variations can be made without departing from the spirit and scope of the invention. Therefore, such modifications or variations will have to be belong to the claims of the present invention.

Claims (5)

In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans), Designed to satisfy the desired pressure distribution function by combining a general two-dimensional rear wing impeller and a high pressure three-dimensional impeller to satisfy a given performance (flow, pressure)

'Q ₁ ' and the flow rate through the 3D impeller with varying inlet height ratio (x ₁ ), outlet width height ratio (x ₂ ) and inlet / outlet angles (β ₁ and β ₂ ) of each impeller with respect to Determine the flow rate 'Q ₂ ' through the 2D impeller, The entry and exit angles of the two impellers coincide so that the two (2D, 3D) impellers are connected naturally (

A hybrid design method for a turbo type rear-wing multiple impeller in which vertical vectors of two impeller faces on two impeller connecting lines coincide with each other. In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans), It is the intermediate form of the general two-dimensional centrifugal blade and the three-dimensional blade used in the centrifugal compressor. It is a shape in which the blade does not stand straight from the base plate to the shroud and is laid at an angle. The shape of the 2.5-dimensional blade is compared with the blade designed in two-dimensional. It has a coplanar profile except for the lean angle (the angle of the wing lying outwards (θ)), and the rear end is inclined with respect to the exit width direction (the direction perpendicular to the impeller back plate at the wing exit). At the same time, the load noise is also reduced, in which case the lean angle (θ) has an angle of less than 20 degrees so as not to block the inlet portion of the pressure surface hybrid design method of the turbo-type rear-wing multi-impeller. In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans), The tooth height (H) should not exceed 10% of the cord length (straight distance from the inlet to the outlet of the blade) so that the vortices of the same frequency occur on the tooth surface formed at the rear of the blade. (P) is less than the correlation distance of the trailing vortex shedding flow (the distance Lc in the direction perpendicular to the streamline in which the vortices are considered to be in the same phase) so that the vortic shedding of the same phase is at least And the height (H) of the tooth is such that the length of the vortex period is equal to an integer multiple of the same sign (+,-) direction of the vortex. In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans), The rear curvature formed on the impeller blade has one or more curvature radii other than the curvature on the rotating surface, so that lift fluctuations caused by vortices amplified in the rear stage are amplified so that the noise radiated from the rear stage is canceled near the rear stage. Hybrid design method of the turbo type rear-wing multi-impeller characterized in that the noise is reduced. In the turbo type rear wing three-dimensional impeller used in centrifugal blowers (fans) or scrollless plenium blowers (fans), To reduce the blade passage and the harmonic frequency of the turbofan, bend the shroud inlet leading edges of some vanes in the direction of the pressure plane and the shroud inlet leading edges of some vanes in the negative pressure plane. In addition, the front edge of the remaining wing to maintain the existing state of the torque balance to reduce the noise level at the wing passing frequency and its harmonic frequency compared to the existing frequency spectrum hybrid of the turbo type rear-wing multi-impeller Design method.

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