A pilot valve design method based on boundary layer theory

Abstract

The present application relates to a pilot valve design method based on boundary layer theory, comprising the following steps: step one, based on the fluid boundary layer theory, calculating the effective fluid area, and establishing a relationship equation among the effective fluid area, actual fluid area and length, and obtaining relationship equation one; step two, establishing a relationship equation among the outlet length, the pilot hole cross-sectional area and the pilot hole length, and obtaining relationship equation two; step three, solving the range of the outlet length, the pilot hole cross-sectional area and the pilot hole length; the present invention effectively improves the design accuracy and adaptability of the pilot valve on the basis of considering the fluid boundary layer effect, especially when facing different pressure requirements, the stability and reliability of the valve performance can be ensured through flexible structural adjustment. Through this design method, the trial and error and optimization cycle in the design process can be greatly reduced, thereby improving engineering efficiency.

Description

Technical Field

[0001] The present application relates to the field of fluid control technology, and in particular to a pilot valve design method based on boundary layer theory. Background Art

[0002] Existing pilot valve design methods mostly rely on empirical formulas and data for design and optimization, lacking precise mathematical model analysis of the relationships between fluid flow patterns, pressure fluctuations, and valve body structure. In particular, existing design methods often rely on intuition or trial-and-error adjustments when designing pilot and exhaust port dimensions, making it difficult to ensure optimality and stability. While these methods can meet the needs of some common operating conditions, they often lack a scientific theoretical basis for complex operating conditions or variable inlet pressure requirements, making valve performance prediction and optimization difficult.

[0003] Specifically, existing pilot valve design methods often ignore the boundary layer effect in fluid mechanics, making it impossible to accurately calculate and control the pressure loss and flow distribution generated by fluid flow within the valve body. The boundary layer effect has a significant impact on fluid flow characteristics and pressure regulation. Especially in conditions of high pressure differentials and high flow rates, ignoring boundary layer theory can lead to problems such as poor valve stability, slow response, or excessive oscillation during operation, seriously affecting the performance and reliability of the equipment.

[0004] Therefore, existing design solutions lack scientific fluid dynamics theory support, especially in the design of the shape and area ratio of the pilot and exhaust ports, and lack optimization solutions based on fluid flow characteristics (such as boundary layer effects). This means that existing design methods often require repeated debugging and modification when facing different operating pressures and flow requirements, increasing development costs and time.

[0005] Therefore, there is an urgent need for a pilot valve design method based on fluid mechanics theory, especially boundary layer theory, which can provide a theoretical basis in the design stage, accurately control the shape and area ratio of the pilot port and the exhaust port, thereby optimizing the performance of the valve and adapting to a wider range of working conditions. Summary of the Invention

[0006] In order to solve the problems of poor stability, slow response, excessive oscillation, poor reliability and high cost in the existing pilot valve design proposed in the above background technology due to ignoring the boundary layer effect, the present application provides a pilot valve design method based on boundary layer theory.

[0007] This application provides a pilot valve design method based on boundary layer theory using the following technical solutions:

[0008] A pilot valve design method based on boundary layer theory includes the following steps:

[0009] Step 1: Based on the fluid boundary layer theory, calculate the effective fluid area and establish the relationship equation between the effective fluid area, actual fluid area and length, and obtain the relationship equation 1:

[0010]

[0011] In the formula:

[0012] L is the length of the flow channel in meters (m);

[0013] ΔP is the pressure difference between the two ends of the flow channel, the unit is Pascal (Pa);

[0014] f Darcy is the Darcy friction factor;

[0015] ρ is the fluid density in kilograms per cubic meter (kg / m 3 );

[0016] Step 2: Establish the relationship equation between the outlet length, the pilot hole cross-sectional area, and the pilot hole length, and obtain the second relationship equation:

[0017]

[0018] In the formula:

[0019] A 先有 is the effective area of ​​the pilot hole, in square meters (m 2 );

[0020] A 出有 is the effective area of ​​the outlet, in square meters (m 2 );

[0021] ΔP1 is the pressure difference between the two ends of the flow channel at the outlet position, the unit is Pascal (Pa);

[0022] ΔP2 is the pressure difference between the two ends of the flow channel at the pilot hole position, the unit is Pascal (Pa);

[0023] L 先 is the length of the pilot hole flow channel, in meters (m);

[0024] L 出 is the outlet flow channel length, in meters (m);

[0025] Step 3: Calculate the range of outlet length, pilot hole cross-sectional area, and pilot hole length;

[0026] From the relationship 1, we can get the effective area A at the pilot hole position: 先有 , L 先 and A 先实The third relationship is:

[0027]

[0028] And the effective area A at the exit position can be obtained 出有 , L 出 and A 出实 The fourth relationship is:

[0029]

[0030] Since there is a specific proportional relationship between the length and diameter of the hole in the actual pilot valve design, when the actual outlet area A is known 出实 In this case, you can select the corresponding outlet length L 出 The maximum value of the outlet is obtained, and the effective outlet area A is obtained 出有 The minimum value of the valve is required to be opened, and the valve is equivalent to a flow channel of unit length, so Compare The value of must be greater than 1, which means that the relationship formula 5 is:

[0031] After combining equation 5 and equation 2, we get equation 6:

[0032] That is to say, the effective area A of the pilot hole is obtained 先有 The maximum value and pilot hole length L 先 The minimum value of the pilot hole is obtained to obtain the actual area A of the pilot hole. 先实 .

[0033] By adopting the above technical solution, based on the boundary layer theory, the relationship equation between the effective fluid area, actual fluid area and length in the pipeline is first determined. Then, based on the condition that the pilot hole flow rate and the outlet flow rate of the pilot valve are equal, the relationship between the effective area of ​​the pilot hole, the pilot hole flow channel length, the effective area of ​​the outlet and the outlet flow channel length is established. Finally, combined with the general design rules in the fluid pipeline, the maximum value of the effective area of ​​the pilot hole and the minimum value of the pilot hole length are obtained, thereby obtaining the actual area of ​​the pilot hole to meet the dimensional design requirements of the pilot valve. By considering the boundary layer effect of the fluid, the designed pilot valve has better stability, quick response and reliability during use, thus avoiding the problem of repeated debugging and modification, reducing costs and production cycles.

[0034] Optionally, in step 1, the process of obtaining the relational expression 1 includes the following steps:

[0035] S1. Calculation of boundary layer thickness δ(L), the formula is:

[0036] S2. Calculation of effective flow area, the second formula is: A 有 =π·(R-δ(L)) 2 ;

[0037] S3. In computational fluid dynamics, the relationship between flow velocity, flow channel length and effective area is as follows:

[0038]

[0039] Combining the above formulas 1, 2, and 3, we can get the relationship formula 1 in step 1;

[0040] In the three formulas:

[0041] U is the flow velocity in meters per second (m / s);

[0042] ν is the kinematic viscosity of the fluid, in square meters per second (m 2 / s);

[0043] R is the flow channel radius, in meters (m).

[0044] By adopting the above technical solution, the area occupied by the boundary layer thickness position is removed when calculating the effective flow area, so that the value of the effective flow area is more accurate after the calculation is completed, and a more accurate relationship between flow velocity, flow channel length and effective area is obtained.

[0045] Optionally, in step 2, the process of obtaining the second relational expression includes the following steps:

[0046] A1. Based on the Darcy-Weisbach equation, we can derive the relationship between flow rate, pressure difference between the two ends of the flow channel, cross-sectional area, and length in fluid mechanics. Formula 4 is:

[0047] Where Q is the flow rate in cubic meters per second (m 3 / s);

[0048] A2. At the exit position, establish the exit flow Q 出 , outlet flow channel length L 出 and outlet effective area A 出有 The relationship between them is:

[0049] A3. At the pilot hole position, establish the pilot hole flow Q 先 , pilot hole effective area A 先有 and pilot hole flow path length L 先 The relationship equation, that is, Formula 6 is:

[0050] Since the pilot hole flow Q 先and the outlet flow Q 出 Equal, by combining Formula 5 and Formula 6, we can get the relationship formula 2 in step 2.

[0051] By adopting the above technical solution, the relationship between the effective area of ​​the pilot hole, the pilot hole flow path length, the effective area of ​​the outlet and the outlet flow path length is obtained mainly through the condition of the same inlet and outlet flow rate, so as to facilitate the subsequent solution process.

[0052] Optionally, in step three, the specific ratio between the length and the pore diameter is 10:1.

[0053] By adopting the above technical solution, which is used to comply with the general rules in fluid mechanics pipeline design, the problem of unstable fluid flow in the hole due to the hole length being too short can be avoided, thereby improving the stability of fluid flow and facilitating flow rate control and flow distribution.

[0054] Optionally, a verification stage is also included, and the steps of the verification stage are: based on the actual cross-sectional area, length and outlet length range of the manufactured pilot hole, reversely infer the inlet pressure range and the outlet cross-sectional area of ​​the pilot valve main piston to verify whether the valve design meets the expected functional requirements and working conditions.

[0055] By adopting the above technical solution, it is used to verify whether the valve design meets the working conditions, so as to facilitate further optimization.

[0056] Optionally, an optimization stage is also included, and the steps of the optimization stage are: when the inlet pressure requirement range changes, the cross-sectional area, length or outlet length of the pilot hole is adjusted according to the new requirements to ensure that the new inlet pressure range requirements are met.

[0057] By adopting the above technical solution, the size of the pilot valve can be adjusted according to actual needs, so as to improve the flexibility and adaptability of the overall design.

[0058] In summary, this application includes at least one of the following beneficial technical effects:

[0059] The present invention effectively improves the design accuracy and adaptability of the pilot valve based on consideration of the fluid boundary layer effect. In particular, when facing different pressure requirements, the stability and reliability of the valve performance can be ensured through flexible structural adjustment. Through this design method, the repeated trial and error and optimization cycle in the design process can be greatly reduced, thereby improving engineering efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a schematic diagram of the main piston of the pilot valve.

[0061] Description of reference numerals:

[0062] 1. Main piston; 2. Pilot hole; 3. Inlet length; 4. Outlet length; 5. Outlet; 6. Valve body. DETAILED DESCRIPTION

[0063] The present application is further described in detail below with reference to the accompanying drawings.

[0064] As shown in the figure, the embodiment of the present application discloses a pilot valve design method based on boundary layer theory, wherein the main piston 1 of the pilot valve is connected to the valve body 6, and has a pilot hole 2 and an outlet 5 connected to the inner cavity of the valve body 6 on the main piston 1, wherein the inlet length 3 of the pilot hole is L 先 , the outlet length 4 is L 出 .

[0065] The specific design method includes the following steps:

[0066] Step 1: Based on the fluid boundary layer theory, the effective fluid area is calculated, and a relationship equation among the effective fluid area, actual fluid area, and length is established, which specifically includes the following steps:

[0067] S1. The formation of a boundary layer is an important phenomenon in fluid mechanics. Especially when flowing in a pipe or channel, the fluid layer near the pipe wall has a slower velocity, while the fluid in the center of the channel has a faster velocity. This velocity gradient leads to the existence of a boundary layer and affects the effective flow area of ​​the fluid. The boundary layer thickness δ(L) is calculated using the following formula:

[0068]

[0069] Where, L is the length of the flow channel, in meters (m);

[0070] U is the flow velocity in meters per second (m / s);

[0071] ν is the kinematic viscosity of the fluid, in square meters per second (m 2 / s);

[0072] S2. After the calculation formula of the boundary layer thickness is obtained, the effective flow area in the pipeline can be obtained, which is recorded as formula 2: A 有 =π·(R-δ(L)) 2 ;

[0073] Where R is the flow channel radius, in meters (m);

[0074] S3. In fluid mechanics, there is a relationship between flow velocity, flow channel length, and effective area, which is expressed as Formula 3:

[0075]

[0076] Where ΔP is the pressure difference between the two ends of the flow channel, and the unit is Pascal (Pa);

[0077] f Darcy is the Darcy friction factor;

[0078] L is the length of the flow channel, in meters (m);

[0079] ρ is the fluid density in kilograms per cubic meter (kg / m 3 );

[0080] U is the flow velocity in meters per second (m / s);

[0081] By combining the above formulas 1, 2, and 3, we can derive the relationship between the effective fluid area, actual fluid area, and length, which is expressed as formula 1:

[0082]

[0083] Among them, A 实 is the actual area in square meters (m 2 ).

[0084] Step 2: Establish the relationship equation between the outlet length, the pilot hole cross-sectional area, and the pilot hole length. The specific steps are as follows:

[0085] A1. According to the Darcy-Weisbach equation, the relationship between flow rate, pressure difference at both ends of the flow channel, cross-sectional area, and length in fluid mechanics can be derived. It can be calculated using Formula 4:

[0086] Where Q is the flow rate in cubic meters per second (m 3 / s);

[0087] μ is the dynamic viscosity of the fluid, the unit is P*s;

[0088] L is the length of the flow channel in meters (m);

[0089] ΔP is the pressure difference across the flow channel, measured in Pascals (Pa);

[0090] A2. At the exit position, establish the exit flow Q 出 , outlet flow channel length L 出 and outlet effective area A 出有 For the outlet, since the pilot-operated high-pressure valve has a maximum opening pressure, the actual outlet area A can be designed based on the maximum opening pressure. 出实 In the equation, the pressure difference ΔP1 and the fluid dynamic viscosity μ are known, and the outlet flow rate Q can be established. 出 and outlet channel length L 出 and outlet effective area A出有 The relationship between them is:

[0091]

[0092] A3. Similarly, in the equation at the pilot hole, the pressure difference ΔP2 and the fluid dynamic viscosity μ are known, and the effective area of ​​the pilot hole A 先有 and pilot hole flow path length L 先 Unknown, so the pilot hole flow Q can be established 先 and the effective area A of the pilot hole 先有 and pilot hole flow path length L 先 The relationship between them is:

[0093] Since the pilot hole flow Q 先 and the outlet flow Q 出 are equal, so the effective area A of the pilot hole can be established 先有 , pilot hole flow channel length L 先 , effective outlet area A 出有 and outlet channel length L 出 The relationship formula is recorded as the second relationship formula:

[0094]

[0095] Step 3: Calculate the range of outlet length, pilot hole cross-sectional area, and pilot hole length;

[0096] By the same logic, we can get the effective area A at the pilot hole position: 先有 , L 先 and A 先实 The third relationship is:

[0097]

[0098] And the effective area A at the exit position can be obtained 出有 , L 出 and A 出实 The fourth relationship is:

[0099]

[0100] In actual pilot valve design, there is a specific proportional relationship between the length and diameter of the hole, that is, the ratio between the length and diameter of the hole is 10:1, as shown in Table 1 below:

[0101]

[0102]

[0103] Therefore, when the actual outlet area A is known出实 In this case, you can select the corresponding outlet length L 出 The maximum value of the outlet is obtained, and the effective outlet area A is obtained 出有 The minimum value of the valve is required to be opened, and the valve is equivalent to a flow channel of unit length, so Compare The value of must be greater than 1, which means that the relationship formula 5 is:

[0104] After combining equation 5 and equation 2, we get equation 6:

[0105] That is to say, the effective area A of the pilot hole is obtained 先有 The maximum value and pilot hole length L 先 The minimum value of the pilot hole is obtained to obtain the actual area A of the pilot hole. 先实 In this way, as long as the values ​​are within the design requirements and size requirements, our inlet pressure working requirements can be met.

[0106] After the above design, a verification stage is also included. The steps of the verification stage are: based on the actual cross-sectional area, length and outlet length range of the manufactured pilot hole, reversely infer the inlet pressure range and the outlet cross-sectional area of ​​the pilot valve main piston to verify whether the valve design meets the expected functional requirements and working conditions.

[0107] Specifically, it also includes an optimization stage, and the steps of the optimization stage are: when the inlet pressure requirement range changes, according to the new requirements, the cross-sectional area, length or outlet length of the pilot hole is adjusted to ensure that the new inlet pressure range requirements are met.

[0108] The following describes in detail the pilot valve in this embodiment during the design, verification, and optimization stages using specific numerical values.

[0109] 1. Design stage

[0110] During the design phase, it is assumed that the fluid is water. The inlet pressure P is known. 进 The range is 8MPa-100MPa, the electromagnetic force is 20N, and considering the design principle of leaving one-third of the margin, the maximum opening pressure is 100MPa multiplied by the actual outlet area A 出实 The value must be less than 13N, so the actual outlet area A 出实 =4π×10 -8 m 2 , with a radius of 0.2mm. The mass of the main piston M = 10g. In order to open the pilot valve, the pressure difference ΔP2 at both ends of the pilot hole is multiplied by the effective area A of the lower surface of the main piston. 下 The value must be greater than the gravity of the main piston, and the effective area A of the lower surface of the main piston 下 =1.2×10-6 m 2 In order to ensure that the pilot valve can open, the pressure difference ΔP2 = 3MPa. The pressure difference ΔP1 = 5MPa, the Darcy friction factor f Darcy =0.05, kinematic viscosity ν = 1 × 10 -6 m 2 / s, density ρ=1000kg / m 3 ,From Table 1, we know that the radius of 0.2mm corresponds to the maximum processing length of 2mm. Through the relationship formula 4:

[0111]

[0112] It can be concluded that A 出有 The minimum value is 1.92×10 -18 m 2 From equation 6, we can know that:

[0113]

[0114] Calculate the pilot hole length L 先 Greater than 2.49mm, from Table 1, we can get the actual area A of the pilot hole corresponding to 2.5mm 先实 The minimum value is 19.63×10 -8 m 2 , from the second relation:

[0115]

[0116] Get the effective area A of the pilot hole 先有 The maximum value is 2.77×10 -18 m 2 , from equation 3 we can get:

[0117]

[0118] The actual area A of the pilot hole can be calculated 先实 The maximum value is 26.66×10 -8 m 2 , the maximum radius is 0.3mm, corresponding to the maximum pilot hole length L 先 is 3mm. Finally, it is concluded that 0<L 出 ≤2mm, 2.5mm≤L 先 ≤3mm, 19.63×10 -8 m 2 ≤A 先实 ≤26.66×10 -8 m 2 All dimensions within this processing range can meet the working requirements of the pilot valve.

[0119] 2. Verification phase

[0120] During the verification phase, the fluid is assumed to be water. After the pilot valve main piston has been designed and manufactured, the Darcy friction factor f is known. Darcy =0.05, kinematic viscosity ν = 1 × 10 -6 m 2 / s, density ρ=1000kg / m 3 , actual area A 出实 =4π×10 -8 m 2 , the electromagnetic force is 20N, considering the design principle of leaving one-third of the margin, the maximum opening pressure P max Multiply by the actual area of ​​the outlet A 出实 The value must be less than 13N, so the maximum inlet pressure P max =100MPa. Pilot valve outlet length L 出 2mm, pilot hole length L 先 is 2.5mm, the actual area A 先实 =26.66×10 -8 m 2 , the mass of the main piston M = 10g, in order to allow the pilot valve to open, the pressure difference ΔP2 at both ends of the pilot hole is multiplied by the effective area A of the lower surface of the main piston 下 The value must be greater than the gravity of the main piston, and the effective area A of the lower surface of the main piston 下 =1.2×10 -6 m 2 In order to fully ensure that the pilot valve can open, the pressure difference ΔP2 = 3MPa. First, according to the third relationship, we can know:

[0121]

[0122] It can be concluded that A 先有 =2.77×10 -18 m 2 , we can also use the relationship 4 and relationship 2 to find A 出有 and ΔP1:

[0123]

[0124] It can be concluded that ΔP1=5MPa and A 出有 =1.92×10 -18 m 2 , from which we can get the minimum inlet pressure P min =ΔP1+ΔP2=8MPa, so the inlet pressure range is 8MPa-100MPa.

[0125] 3. Optimization phase

[0126] During the optimization phase, if the inlet pressure requirement changes, the new inlet pressure requirement can be achieved by adjusting the size of the outlet and pilot hole. Assuming the original inlet pressure range is 8MPa-100MPa, the electromagnetic force is 20N, the main piston mass M = 10g, and the effective area of ​​the main piston bottom surface A 下 =1.2×10 -6 m 2 Then through calculation in the design stage we can know that 0<L 出 ≤2mm, 2.5mm≤L 先 ≤3mm, 19.63×10 -8 m 2 ≤A 先实 ≤26.66×10 -8 m 2 , A 出实 =4π×10 -8 m 2 , pressure difference ΔP2=3MPa, pressure difference ΔP1=5MPa, Darcy friction factor f Darcy =0.05, kinematic viscosity ν = 1 × 10 -6 m 2 / s, density ρ=1000kg / m 3 Now, due to certain work requirements, the inlet pressure range is changed to 8MPa-150MPa. Considering the design principle of leaving one-third of the margin, the maximum opening pressure 150MPa is multiplied by the actual outlet area A. 出实 The value must be less than 13N, so the actual outlet area A 出实 =2.25π×10 -8 m 2 , the radius is 0.15mm. From Table 1, we know that the maximum processing length corresponding to a radius of 0.15mm is 1.5mm. From the fourth equation, we can know that:

[0127]

[0128] It can be concluded that A 出有 The minimum value is 2.85×10 -16 m 2 From equation 6, we can know that:

[0129]

[0130] The pilot hole length L 先 Greater than 1.77mm, from Table 1, we can get the actual area A of the pilot hole corresponding to 1.8mm 先实 The minimum value is 10.18×10 -8 m 2 , we can know from the second relation:

[0131]

[0132] Get the effective area A of the pilot hole 先有 The maximum value is 4.25×10 -16 m 2 , we can know from equation 3:

[0133]

[0134] The actual area A of the pilot hole can be calculated 先实 The maximum value is 13.34×10 -8 m 2 , the maximum radius is 0.2mm, corresponding to the maximum pilot hole length L 先 is 2mm. Finally, it is concluded that 0<L 出 ≤1.5mm, 1.8mm≤L 先 ≤2mm, 10.18×10 -8 m 2 ≤A 先实 ≤13.34×10 -8 m 2 , so that you can get a new size that meets the work requirements.

[0135] This pilot valve design method based on boundary layer theory determines the range of values ​​of the cross-sectional area, length and outlet length of the pilot port according to the inlet pressure range and the cross-sectional area of ​​the pilot valve main piston outlet during the design phase, and optimizes the valve body structure through mathematical models or calculation formulas to ensure that the valve performance matches the pressure range; during the verification phase, the inlet pressure range and the cross-sectional area of ​​the pilot valve main piston outlet are reversed based on the actual cross-sectional area, length and outlet length range of the manufactured pilot port to verify whether the valve design meets the expected functional requirements and working conditions; during the optimization phase, when the inlet pressure requirement range changes, the cross-sectional area, length or outlet length of the pilot port is adjusted according to the new requirements to ensure that the new inlet pressure range requirements are met, thereby improving the flexibility and adaptability of the design.

[0136] This design method can effectively improve the design accuracy and adaptability of the pilot valve, especially when facing different pressure requirements, and can ensure the stability and reliability of valve performance through flexible structural adjustment. This method can significantly reduce the repeated trial and error and optimization cycle in the design process, and improve engineering efficiency.

[0137] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A pilot valve design method based on boundary layer theory, characterized in that: The following steps are involved: Step 1: Based on the fluid boundary layer theory, calculate the effective fluid area and establish the relationship equation between the effective fluid area, actual fluid area and length, and obtain the relationship equation 1: In the formula: L is the length of the flow channel in meters (m); ΔP is the pressure difference between the two ends of the flow channel, the unit is Pascal (Pa); f Darcy is the Darcy friction factor; ρ is the fluid density in kilograms per cubic meter (kg / m 3 ); Step 2: Establish the relationship equation between the outlet length, the pilot hole cross-sectional area, and the pilot hole length, and obtain the second relationship equation: In the formula: A 先有 is the effective area of ​​the pilot hole, in square meters (m 2 ); A 出有 is the effective area of ​​the outlet, in square meters (m 2 ); ΔP1 is the pressure difference between the two ends of the flow channel at the outlet position, the unit is Pascal (Pa); ΔP2 is the pressure difference between the two ends of the flow channel at the pilot hole position, the unit is Pascal (Pa); L 先 is the length of the pilot hole flow channel, in meters (m); L 出 is the outlet flow channel length, in meters (m); Step 3: Calculate the range of outlet length, pilot hole cross-sectional area, and pilot hole length; From the relationship 1, we can get the effective area A at the pilot hole position: 先有 , L 先 and A 先实 The third relationship is: And the effective area A at the exit position can be obtained 出有 , L 出 and A 出实 The fourth relationship is: Since there is a specific proportional relationship between the length and diameter of the hole in the actual pilot valve design, when the actual outlet area A is known 出实 In this case, you can select the corresponding outlet length L 出 The maximum value of the outlet is obtained, and the effective outlet area A is obtained 出有 The minimum value of the valve is required to be opened, and the valve is equivalent to a flow channel of unit length, so Compare The value of must be greater than 1, which means that the relationship formula 5 is: After combining equation 5 and equation 2, we get equation 6: That is to say, the effective area A of the pilot hole is obtained 先有 The maximum value and pilot hole length L 先 The minimum value of the pilot hole is obtained to obtain the actual area A of the pilot hole. 先实 .

2. A pilot valve design method based on boundary layer theory according to claim 1, characterized in that: In step 1, the process of obtaining the relational expression 1 includes the following steps: S1. Calculation of boundary layer thickness δ(L), the formula is: S2. Calculation of effective flow area, the second formula is: A 有 =π·(R-δ(L)) 2 ; S3. In computational fluid dynamics, the relationship between flow velocity, flow channel length and effective area is as follows: Combining the above formulas 1, 2, and 3, we can get the relationship formula 1 in step 1; In the three formulas: U is the flow velocity in meters per second (m / s); ν is the kinematic viscosity of the fluid, in square meters per second (m 2 / s); R is the flow channel radius, in meters (m).

3. The pilot valve design method based on boundary layer theory according to claim 1 is characterized in that: In step 2, the process of obtaining the second relational expression includes the following steps: A1. Based on the Darcy-Weisbach equation, we can derive the relationship between flow rate, pressure difference between the two ends of the flow channel, cross-sectional area, and length in fluid mechanics. Formula 4 is: Where Q is the flow rate in cubic meters per second (m 3 / s); A2. At the exit position, establish the exit flow Q 出 , outlet flow channel length L 出 and outlet effective area A 出有 The relationship between them is: A3. At the pilot hole position, establish the pilot hole flow Q 先 , pilot hole effective area A 先有 and pilot hole flow path length L 先 The relationship equation, that is, Formula 6 is: Since the pilot hole flow Q 先 and the outlet flow Q 出 Equal, by combining Formula 5 and Formula 6, we can get the relationship formula 2 in step 2.

4. The pilot valve design method based on boundary layer theory according to claim 1 is characterized in that: In step three, the specific ratio between the length and the diameter of the hole is 10:

1.

5. The pilot valve design method based on boundary layer theory according to claim 1 is characterized in that: It also includes a verification stage, the steps of which are: based on the actual cross-sectional area, length and outlet length range of the manufactured pilot hole, reversely infer the inlet pressure range and the outlet cross-sectional area of ​​the pilot valve main piston to verify whether the valve design meets the expected functional requirements and working conditions.

6. The pilot valve design method based on boundary layer theory according to claim 5, characterized in that: The method further includes an optimization phase, wherein the steps of the optimization phase are: when the required range of the inlet pressure changes, the cross-sectional area, length or outlet length of the pilot hole is adjusted according to the new requirements to ensure that the new inlet pressure range requirements are met.

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