CN115342068A - A method to improve the performance of agricultural ventilator - Google Patents

Abstract

The invention belongs to the field of mechanical application equipment, and particularly relates to a method for improving the performance of an agricultural ventilator. The method comprises the following steps: s1, carrying out performance test on the prototype agricultural ventilator to obtain ventilation volume, inlet static pressure and power parameters of the prototype agricultural ventilator; s2, reversely modeling the blade 4 of the prototype agricultural ventilator to obtain the radial position, chord length and air inlet geometric angle corresponding to the blade 4 of the prototype agricultural ventilator relative to the blade height; s3, selecting an airfoil profile matched with the blade 4 of the prototype agricultural ventilator as an airfoil profile of the front guide vane 6; s4, solving a function model of the front guide vane installation combination by taking the ventilation quantity as an optimization target; s5, manufacturing the front guide vane 6 according to the wing section of the front guide vane 6 obtained in the step S3; and then, installing the front guide vane 6 on the prototype agricultural ventilator according to the function model of the front guide vane installation combination obtained in the step S4.

Description

A method to improve the performance of agricultural ventilator

technical field

The invention belongs to the field of mechanical application equipment, and in particular relates to a method for improving the performance of an agricultural ventilator.

Background technique

With the development of the economy and society, my country has changed from the stage of pursuing rapid economic development to the stage of high-quality development. Social and economic transformation has put forward new requirements for the production scale and production quality of various industries, and put forward higher requirements for the supply of fluid machinery. Require. Axial flow fan is a typical fluid machine, and its wide application also puts forward higher requirements for axial flow fans. Among them, it is most urgent to solve the problems of high energy consumption and low utilization rate of axial flow fans. Therefore, improving the efficiency of axial flow fans and reducing the energy consumption of axial flow fans has become a bottleneck restricting the rapid development of the axial flow fan industry.

With the high-quality development of my country's modern aquaculture industry, higher requirements are put forward for agricultural axial flow fans with low energy consumption and large ventilation volume. The performance testing of agricultural axial flow fans conducted in the ventilation equipment performance testing laboratory of China Agricultural University has a ventilation energy efficiency in the range of 20% to 40%. Compared with high-efficiency fans worldwide, the efficiency of agricultural axial flow fans is generally low. Therefore, improving the energy conversion efficiency of agricultural axial flow fans is the key to energy saving and emission reduction. It is feasible to increase the ventilation rate and reduce energy consumption of agricultural axial flow fans by adding front guide vanes to change the air inlet angle, which is of great significance to energy conservation and environmental protection. At present, the front guide vanes have not been applied in the field of agricultural axial flow fans, and there are no ready-made achievements available for those skilled in the art. Based on the above background, the present invention is proposed.

Contents of the invention

In view of the above-mentioned technical problems, the purpose of the present invention is to provide a method for improving the performance of the agricultural ventilator. The airfoil adapted to the blade of the prototype agricultural ventilator is selected as the airfoil of the front guide vane. The installation structure parameters and function model of the front guide vane, the optimal value of the installation angle α ₁ of the front guide vane, the dynamic and static installation distance L of the guide vane, and the number n of guide vanes are obtained, so as to significantly improve the ventilation of the agricultural fan The volume and ventilation energy efficiency ratio can be improved, the internal flow state of the agricultural ventilator can be improved, and the working ability of the agricultural ventilator can be improved.

In order to achieve the above object, the present invention provides the following technical solutions:

A method for improving the performance of an agricultural ventilator, the agricultural ventilator includes a motor 1, a rotating shaft 2, a hub 3, blades 4 and a current collector 5; wherein, the inlet and outlet of the current collector 5 are circular rings with equal diameters, and the motor 1 is fixed on the wall of the current collector 5 through the motor bracket; the rotating shaft 2 of the motor 1 extends to the front end of the hub 3; the root of the blade 4 is placed in the groove reserved for the hub 3 and fixed on the hub 3;

Wherein, the method comprises the steps of:

S1. Perform a performance test on the prototype agricultural ventilator, and obtain the ventilation volume, inlet static pressure, and power parameters of the prototype agricultural ventilator;

S2. Carry out reverse modeling to the blade 4 of the prototype agricultural fan, and obtain the corresponding radial position, chord length and intake geometric angle of the blade 4 of the prototype agricultural fan relative to the blade height;

S3, select the airfoil adapted to the blade 4 of the prototype agricultural fan as the airfoil of the front guide vane 6; wherein,

为0.05～0.1的翼型作为前置导叶6的翼型；Select the chord length corresponding to the relative height of the blade 4 at 0.5 as the chord length of the front guide vane 6, select the lift coefficient as 0.9-1.1, and the relative thickness of the airfoil

The airfoil of 0.05-0.1 is used as the airfoil of the front guide vane 6;

S4. Taking the ventilation rate as the optimization target, solve the function model of the installation combination of the front guide vanes:

The function model of ventilation volume and guide vane installation angle α ₁ , the dynamic and static installation distance L of guide vanes, and the number n of guide vanes, that is, the function model of the installation combination of front guide vanes is:

Among them, x ₁ is the installation angle ɑ ₁ of the front guide vane, the unit is °; x ₂ is the dynamic and static installation distance L of the guide vane, the unit is mm; x ₃ is the number of guide vanes n;

S5, according to the airfoil profile of the front guide vane 6 obtained in step S3, make the front guide vane 6; then according to the function model of the installation combination of the front guide vane obtained in step S4, install the front guide vane 6 on the prototype agricultural on the ventilator.

为0.09。Wherein, in step S3, the chord length of the front guide vane 6 is 103mm, the lift coefficient of the airfoil of the front guide vane 6 is 0.96, and the relative thickness of the airfoil of the front guide vane 6

is 0.09.

Wherein, the hub 3 is divided into two parts, front and rear, and is fastened on the rotating shaft 2 by a nut ring.

Compared with prior art, the beneficial effect of the present invention is:

1) The method for improving the performance of the agricultural ventilator of the present invention selects the airfoil adapted to the blade of the prototype agricultural ventilator as the airfoil of the front guide vane, and through the function model of the ventilation volume and the installation structure parameters of the front guide vane, significantly Improve fan ventilation and energy efficiency ratio.

2) The method for improving the performance of the agricultural ventilator of the present invention can increase the ventilation energy efficiency ratio of the agricultural ventilator by 5.7% to 10.39%, and the ventilation rate by 6.62% to 10.89%.

3) The method for improving the performance of the agricultural ventilator of the present invention can effectively enhance the working ability of the fan blades.

Description of drawings

Fig. 1 a is the left view structural diagram of agricultural ventilator;

Fig. 1b is the front view structural diagram of agricultural ventilator;

Figure 1c is a rear view structural diagram of the agricultural ventilator;

Fig. 2 a is the first schematic diagram of the front guide vane airfoil selected by the front guide vane of the present invention;

Fig. 2b is the second schematic diagram of the front guide vane airfoil selected by the front guide vane of the present invention;

Fig. 3 a is the positive isometric structural view of the installation embodiment of the front guide vane of the agricultural ventilator of the present invention;

Fig. 3b is the rear view structural diagram of the front guide vane installation embodiment of the agricultural ventilator of the present invention;

Fig. 4a is the first schematic diagram of the installation angle α ₁ of the front guide vane and the dynamic and static installation distance L of the guide vane according to the present invention;

Fig. 4b is the second schematic diagram of the parameters of the installation angle α1 of the front guide vane and the dynamic and static installation distance L of the guide vane in the present invention;

Fig. 5 a is the contrast curve graph of the ventilation rate of the present invention and prototype agricultural ventilator;

Fig. 5 b is a comparative graph of the energy efficiency ratio of the present invention and the prototype agricultural ventilator;

Figure 6a is the pressure line graph when span=0.15 (low span);

Fig. 6b is the pressure line diagram when span=0.50 (mid-span);

Fig. 6c is a pressure line graph when span=0.85 (high span).

The reference signs therein are:

1 motor 2 shaft

3 hubs 4 blades

5 air collector 6 front guide vane

7Rotation axis direction 8Guide vane trailing edge

9 hub leading edge

α ₁ guide vane installation angle L guide vane dynamic and static installation distance

Detailed ways

In order to make the technical features of the present invention clearer, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in FIG. 1a , FIG. 1b and FIG. 1c , an agricultural ventilator includes a motor 1 , a rotating shaft 2 , a hub 3 , blades 4 and a collector 5 . in,

The inlet and outlet of the current collector 5 are circular rings with equal diameters, and the motor 1 is fixed on the wall of the current collector 5 through a motor bracket. The rotating shaft 2 of the motor 1 extends to the front end of the hub 3 . The hub 3 is divided into two parts, the front and the rear, and is buckled on the rotating shaft 2 by a nut ring. The root of the blade 4 is placed in the reserved groove of the hub 3 and fixed on the hub 3 .

A method for improving the performance of an agricultural ventilator, comprising the steps of:

S1. Perform a performance test on the prototype agricultural ventilator to obtain performance parameters;

The performance test of the prototype agricultural ventilator is carried out, and the ventilation volume, inlet static pressure and power parameters of the prototype agricultural ventilator are obtained.

S2. Carry out reverse modeling to the blade 4 of the prototype agricultural fan, and obtain the corresponding radial position, chord length and intake geometric angle of the blade 4 of the prototype agricultural fan relative to the blade height;

The blade 4 of the prototype agricultural ventilator was reversely modeled in 3D modeling software, and the radial position, chord length and intake geometric angle of the blade 4 of the prototype agricultural ventilator relative to the height of the blade were obtained.

S3, select the airfoil adapted to the blade 4 of the prototype agricultural fan as the airfoil of the front guide vane 6;

失速性能及翼型形状等都有些差别。选择升力系数为0.9～1.1、翼型相对厚度

为0.05～0.1的翼型作为前置导叶6的翼型。Optimal lift coefficient Cyopt of different airfoils, lift-to-drag ratio 1/μ (1/μ=Cy/Cx), relative thickness of airfoils

There are some differences in stall performance and airfoil shape. Select the lift coefficient as 0.9 to 1.1 and the relative thickness of the airfoil

The airfoil of 0.05-0.1 is used as the airfoil of the front guide vane 6 .

S4. Taking the ventilation rate as the optimization target, solve the function model of the installation combination of the front guide vanes:

Since the function model belongs to the surface equation, Design-Expert software is used to assist the solution.

Single factor analysis is carried out on guide vane installation angle α ₁ , guide vane dynamic and static installation distance L, and number n of guide vanes. The external characteristics are evaluated by the fan ventilation rate and energy efficiency ratio, and the internal characteristics are evaluated by the internal flow field characteristics of the fan. , to get the optimal value range of each factor.

Among them, the fan performance is better when the guide vane installation angle α ₁ is within the range of inlet geometric angle corresponding to the blade height of 0.3 to 0.7 times; the fan performance is better when the number of guide vanes is the same as the number of blades; the dynamic and static installation distance of guide vanes L The performance of the fan in the range of 0.85b _h to 1.2b _h (b _h is the chord length of the blade root) is better.

According to the principle of Box-Behnken test combination design, the installation angle of guide vane α ₁ , the dynamic and static installation distance L of guide vane, and the number n of guide vanes are used as test factors, and the ventilation rate is used as the response value to carry out response surface simulation experiments. The function model of the blade installation angle α ₁ , the dynamic and static installation distance L of the guide vane, and the number n of the guide vanes, that is, the function model of the installation combination of the front guide vanes is:

Among them, x ₁ is the installation angle ɑ ₁ of the front guide vane, the unit is °; x ₂ is the dynamic and static installation distance L of the guide vane, the unit is mm; x ₃ is the number n of guide vanes.

S5, according to the airfoil profile of the front guide vane 6 obtained in step S3, make the front guide vane 6; then according to the function model of the installation combination of the front guide vane obtained in step S4, install the front guide vane 6 on the prototype agricultural on the ventilator.

According to the airfoil of the pre-guide vane 6 obtained in step S3, the pre-guide vane 6 is produced by 3D printing, and according to the guide vane installation angle ɑ ₁ , the dynamic and static installation distance L of the guide vane, and the number n of guide vanes obtained in step S4, Install the front guide vane 6 on the corresponding position of the motor 1 of the prototype agricultural ventilator, the grooves correspond one by one, and fix it with liquid glue. Among them, the installation angle of the front guide vane _ɑ1 is the angle between the chord line at the root of the guide vane and the direction of the rotating shaft; the dynamic and static installation distance L of the guide vane is the distance between the tail of the guide vane and the front edge of the hub.

Example

S1. Perform a performance test on the prototype agricultural ventilator to obtain the performance parameters

The structure of a 550 agricultural ventilator (hereinafter referred to as the prototype agricultural ventilator) is shown in Figure 1a, Figure 1b, and Figure 1c. The speed of the agricultural fan is 1440r/min, the diameter of the fan inlet and outlet is 550mm, the radial length of the blade is 221mm, the diameter of the fan hub is 98mm, the diameter of the motor is 125mm, the length is 148mm, and the axial distance of the inlet and outlet is 380mm .

Under the working condition (49.02Pa), the prototype agricultural fan has a ventilation volume of 6343m3/h and an energy efficiency ratio of 14.2m ³ /(h·W).

S2. Carry out reverse modeling on the blades of the prototype agricultural fan, and further analyze the related parameters of the blades

The blades of the prototype agricultural fan were reverse-modeled in 3D modeling software, and further analyzed to obtain the corresponding radial position, chord length and intake geometric angle of the blade relative to the height of the blade:

S3. Select the airfoil as the airfoil of the front guide vane

为0.09。如图2a和2b所示。According to the characteristics of the prototype agricultural fan blade and its adaptation, select NACA 0015 as the airfoil of the front guide vane 6, the chord length of the front guide vane 6 is 103mm, and the lift coefficient of the airfoil of the front guide vane 6 is 0.96. The relative thickness of the airfoil of the front guide vane 6

is 0.09. This is shown in Figures 2a and 2b.

S4. Taking the ventilation rate as the optimization target, solve the function model of the installation combination of the front guide vanes

Among them, x ₁ is the installation angle ɑ ₁ of the front guide vane, the unit is °; x ₂ is the dynamic and static installation distance L of the guide vane, the unit is mm; x ₃ is the number n of guide vanes.

As shown in Figures 3a, 3b, 4a and 4b, the parameters of the front guide vanes of the agricultural ventilator in this embodiment are set to the installation angle of the front guide vanes ɑ ₁ =21°, the dynamic and static installation distance of the guide vanes L=57mm, the guide vanes The number n=4.

S5, according to the airfoil profile of the front guide vane 6 obtained in step S3, make the front guide vane 6; according to the function model of the installation combination of the front guide vane obtained in step S4, install the front guide vane 6 on the prototype agricultural ventilation on board.

According to the airfoil of the pre-guide vane 6 obtained in step S3, the pre-guide vane 6 is produced by 3D printing, the guide vane installation angle ɑ ₁ =21°, the dynamic and static installation distance of the guide vane L=57mm, and the guide vane installation angle obtained according to step S4 The number of leaves is n=4, the front guide vane 6 is installed on the corresponding position of the motor 1 of the prototype agricultural ventilator, the grooves correspond one by one, and fixed with liquid glue.

The method for improving the performance of the agricultural ventilator of the present invention can improve the ventilation volume and ventilation energy efficiency ratio of the agricultural ventilator. Compared with the prototype agricultural ventilator, under the working condition (49.02Pa), the ventilation volume is 6772m ³ /h, an increase of 6.76%; the energy efficiency ratio is 15.3m ³ /(h·W), an increase of 7.75%.

In order to illustrate the performance of the present invention under all working conditions, the ventilation rate, energy efficiency ratio and blade surface pressure line are taken as examples for analysis.

Figure 5a is a graph comparing the ventilation rate between the present invention and the prototype agricultural ventilator. It can be seen that the ventilation rate gradually decreases with the increase of the inlet static pressure, and the present invention is better than the prototype agricultural ventilator under all working conditions.

Figure 5b is a comparison curve of the energy efficiency ratio between the present invention and the prototype agricultural ventilator. It can be seen that the energy efficiency ratio gradually decreases with the increase of the inlet static pressure, and the present invention is better than the prototype agricultural ventilator under all working conditions.

Fig. 6 a is the pressure line figure (low span) when span=0.15, can find out from the figure that the prototype agricultural fan blade surface pressure difference is less and the maximum pressure difference is about 300Pa; Can obviously find out according to the blower fan after the present invention handles The pressure line wraps the pressure line of the prototype agricultural fan, the pressure difference of the blades is significantly increased, and the working ability of the blades is enhanced.

Figure 6b is a pressure line diagram when span=0.50 (mid-span), the surface pressure difference of the prototype agricultural fan blade increases, and the maximum pressure difference is about 520Pa; the pressure line difference of the fan after processing according to the present invention is also further increased.

Figure 6c is a (high-span) pressure line graph when span=0.85, the surface pressure difference of the prototype agricultural fan blade continues to increase, and the maximum value is about 600Pa; the pressure line difference of the fan after processing according to the present invention is also further increased.

Combining Figures 6a, 6b and 6c, it can be seen intuitively that at low spans, there is an inverse pressure gradient at the leading edge of the blade. This is because the inlet angle of the blade is a negative angle of attack, and the incoming flow first contacts the suction surface of the blade. The pressure on the suction side at the leading edge of the blade is significantly higher than that on the pressure side, resulting in greater losses at the blade root. The pressure difference between the pressure surface and the suction surface in the middle and upper part of the blade is relatively large, which is the main work area of the blade.

Claims (3)

1. A method for improving the performance of the agricultural ventilator, which comprises a motor (1), a rotating shaft (2), a hub (3), a blade (4) and a current collector (5); wherein the current collector The inlet and outlet of (5) are equal-diameter rings, and the motor (1) is fixed on the wall surface of the current collector (5) by the motor bracket; the rotating shaft (2) of the motor (1) extends to the front end of the wheel hub (3) The front end; the root of the blade (4) is placed in the reserved groove of the hub (3), and fixed on the hub (3); It is characterized in that: the method comprises the following steps: S1. Perform a performance test on the prototype agricultural ventilator, and obtain the ventilation volume, inlet static pressure, and power parameters of the prototype agricultural ventilator; S2, carry out reverse modeling to the blade (4) of prototype agricultural ventilator, obtain the corresponding radial position, chord length and inlet geometric angle of blade 4 of prototype agricultural ventilator relative to blade height; S3, select the airfoil adapted to the blade (4) of the prototype agricultural fan as the airfoil of the front guide vane (6); wherein, Select the chord length corresponding to the blade (4) relative to the blade height of 0.5 as the chord length of the front guide vane (6), select the lift coefficient to be 0.9 to 1.1, and the relative thickness of the airfoil

The airfoil of 0.05～0.1 is used as the airfoil of the front guide vane (6); S4. Taking the ventilation rate as the optimization target, solve the function model of the installation combination of the front guide vanes: The function model of ventilation volume and guide vane installation angle α ₁ , the dynamic and static installation distance L of guide vanes, and the number n of guide vanes, that is, the function model of the installation combination of front guide vanes is:

Among them, x ₁ is the installation angle ɑ ₁ of the front guide vane, the unit is °; x ₂ is the dynamic and static installation distance L of the guide vane, the unit is mm; x ₃ is the number of guide vanes n; S5, make the front guide vane (6) according to the airfoil of the front guide vane (6) obtained in step S3; then according to the function model of the front guide vane installation combination obtained in step S4, the front guide vane ( 6) Installed on a prototype agricultural ventilator. 2. The method for improving the performance of the agricultural ventilator as claimed in claim 1, characterized in that: in step S3, the chord length of the front guide vane (6) is 103mm, and the lift of the airfoil of the front guide vane (6) The coefficient is 0.96, the relative thickness of the airfoil of the front guide vane (6)

is 0.09. 3. The method for improving the performance of an agricultural ventilator according to claim 1, characterized in that: the hub (3) is divided into two parts, front and rear, and is fastened on the rotating shaft (2) by a nut ring.

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