A calculation method for the tension control of compressor impeller tie rod with end-face torque transmission

Abstract

The present invention combines theoretical design with on-site operation fault analysis to disclose a method for calculating the pull force control of the impeller pull rod of a compressor with end-face torque transmission. The impeller pull rod pull force F is: the pull force F to overcome the deformation of the impeller 2 , the tensile force F of the transmitted load 3 , compressor impeller axial aerodynamic thrust F 1 sum.

Description

Technical Field

[0001] The invention relates to the technical field of compressors, and in particular to a calculation method for controlling the tension of an impeller pull rod of an end-face torque-transmitting compressor. Background Art

[0002] A compressor is a device used to increase gas pressure and transport gas. During normal operation, the compressor impeller rotates at high speed, and the blades work on the gas to increase the pressure, speed and temperature of the gas. The gas then passes through the diffuser volute and other diffusion components, converting part of the kinetic energy into pressure energy. Compressors have gradually been widely used in the petroleum, chemical, pharmaceutical, sewage treatment and other industries.

[0003] As compressors are used more and more widely, the problems they encounter are also increasing. Many problems on-site at compressors are caused by loose impellers and broken tie rods. A major reason for this phenomenon is improper control of the tie rod tension, which has caused great economic losses to various companies. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, combine theoretical design with on-site operation fault analysis, and provide a calculation method for controlling the pull force of the compressor impeller pull rod with end face torque transmission.

[0005] The object of the present invention is achieved in that:

[0006] A calculation method for controlling the pull force of a compressor impeller rod with end-face torque transmission is provided. The impeller rod pull force F is the sum of the pull force F2 for overcoming impeller deformation, the pull force F3 for transmitting load, and the axial aerodynamic thrust F1 of the compressor impeller.

[0007] Preferably, the compressor impeller intake pressure is higher than the exhaust pressure, and the wheel back pressure is greater than the compressor impeller inlet side pressure. Therefore, the compressor impeller aerodynamic thrust direction is from the wheel back to the impeller inlet end, and the compressor impeller axial aerodynamic thrust F1 is obtained by software simulation.

[0008] Preferably, the impeller deformation under the centrifugal force is contraction, and the impeller deformation is obtained by software simulation. The calculation formula for the pull rod force to overcome the impeller contraction deformation is:

[0009] σ1=E×ε (1)

[0010]

[0011] A=π×r 2 (3)

[0012] From formula 1-3, it can be concluded that the pulling force F2 required by the tie rod to overcome the shrinkage deformation of the impeller is:

[0013] F2=πEεr 2(4)

[0014] Where σ1 is the stress generated by the tension required for the tie rod to overcome the impeller deformation, ε is the shrinkage deformation of the impeller due to centrifugal force, E is the Young's modulus of the tie rod material, F2 is the tension to overcome the impeller deformation, A is the cross-sectional area of ​​the tie rod, and r is the radius of the tie rod.

[0015] Preferably, the compressor impeller and the main shaft mating end surface generate friction to transfer the load, and the residual preload required by the impeller tie rod is:

[0016]

[0017] The friction torque of the disk is:

[0018]

[0019]

[0020] Where T is the torque of the impeller transmitting the corresponding power, P is the power transmitted by the impeller, n is the rotor speed, r1 and r2 are the inner and outer radii of the end faces of the main shaft and the compressor impeller, f is the friction coefficient of the joint surface between the compressor impeller and the main shaft, σ2 is the unit area pressure of the end faces of the main shaft and the compressor impeller, and F3 is the tensile force of the transmitted load;

[0021] From formula 5-7, it can be concluded that the residual preload of the impeller required to transmit the corresponding power of the impeller is:

[0022]

[0023] Preferably, the minimum tension allowed by the pull rod is:

[0024]

[0025] The maximum tension of the tie rod should make the tie rod stress less than its yield stress:

[0026] F max =π×σ×r 2 (10)

[0027] Then the force F range of the tie rod should be:

[0028] F min ≤F≤F max (11)

[0029] Right now

[0030] Preferably, the safety factor K1 and the safety factor K2 are taken respectively, and the suitable range of the impeller pull rod tension F of the end face torque transmission is:

[0031]

[0032] Preferably, the value range of K1 and K2 is 2-3.

[0033] By adopting the above technical scheme, the present invention prevents the compressor impeller tie rod from being broken due to excessive stress during operation, while ensuring that the tie rod has sufficient pre-tightening force to avoid damage to the tie rod and impeller due to loosening of the rotor caused by impeller deformation and inertia when the compressor is running at high speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the compressor rotor with torque transmission on the end face of the compressor impeller.

[0035] Reference numerals

[0036] In the attached drawings, there are thrust plate 1, main shaft 2, impeller tie rod 3, cylindrical pin 4, compressor impeller 5, and locking nut 6. DETAILED DESCRIPTION

[0037] Figure 1 The present invention relates to a typical compressor rotor with end face torque transmission of the compressor impeller, which is mainly composed of a thrust plate, a main shaft, an impeller tie rod, a cylindrical pin, a compressor impeller, and a locking nut. The thrust plate 1 mainly bears the axial thrust (the outer circle of the thrust plate 1 can also be keyed to measure the rotation speed); the main shaft 2 and the compressor impeller 5 are in contact with each other through the end faces, and the contacting end faces are responsible for transmitting the torque transmitted by the main shaft 2 to the compressor impeller, thereby driving the compressor impeller to rotate. The end face torque transmission is simple to manufacture and has low cost; the cylindrical pin 4 is a positioning pin, which is mainly used for positioning for the dynamic balance of the rotor; the locking nut 6 and the impeller tie rod 3 apply a certain preload force to the compressor impeller 5, which forms a certain pressure on the end faces of the compressor impeller 5 and the main shaft 2, and then the end faces transmit the torque through friction.

[0038] See also Figure 1 For compressor impeller rotors that transmit torque by end face friction, the impeller pull rod force mainly overcomes the impeller deformation and the axial aerodynamic thrust of the compressor impeller, and the remaining preload force is used to transmit the load. Therefore, when calculating the required tension of the pull rod, the tension is the sum of the tension to overcome the impeller deformation, the tension to transmit the load, and the aerodynamic axial force.

[0039] The inlet pressure of the compressor impeller is higher than the exhaust pressure, and the back pressure of the wheel is greater than the inlet pressure of the compressor impeller. Therefore, the direction of the aerodynamic thrust of the compressor impeller is from the back of the wheel to the inlet end of the impeller. The thrust is obtained by software simulation and is F1.

[0040] The deformation of the impeller is mainly due to the centrifugal force at high speed. The deformation size is calculated by software simulation. Under the action of centrifugal force, the impeller deforms to shrink. The calculation formula for the pull rod force to overcome the impeller shrinkage deformation is:

[0041] σ1=E×ε (1)

[0042]

[0043] A=π×r 2 (3)

[0044] From formula 1, formula 2 and formula 3, the pulling force F2 required by the tie rod to overcome the shrinkage deformation of the impeller is:

[0045] F2=πEεr 2 (4)

[0046] Where σ1 is the stress generated by the tension required by the tie rod to overcome the impeller deformation, ε is the shrinkage deformation of the impeller due to centrifugal force, E is the Young's modulus of the tie rod material, F2 is the tension required by the tie rod to overcome the shrinkage deformation of the impeller, A is the cross-sectional area of ​​the tie rod, and r is the radius of the tie rod.

[0047] The residual preload after the pull rod force overcomes the impeller shrinkage deformation and aerodynamic thrust is transmitted to the end surface of the compressor impeller and the main shaft, where friction is generated to transfer the load. The residual preload required by the impeller pull rod is:

[0048]

[0049] The friction torque of the disk is:

[0050]

[0051]

[0052] Where T is the torque of the impeller transmitting the corresponding power, P is the power transmitted by the impeller, n is the rotor speed, r1 and r2 are the inner and outer radii of the mating end faces of the main shaft and the compressor impeller respectively, f is the friction coefficient of the joint surface between the compressor impeller and the main shaft, and σ2 is the unit area pressure of the mating end faces of the main shaft and the compressor impeller.

[0053] According to Formula 5, Formula 6 and Formula 7, the residual preload of the impeller required to transmit the corresponding power of the impeller is:

[0054]

[0055] Therefore, the minimum tension allowed by the pull rod is:

[0056]

[0057] The maximum tension of the tie rod should make the tie rod stress less than its yield stress:

[0058] F max =π×σ×r 2 (10)

[0059] The reasonable force F range of the pull rod should be:

[0060] F min ≤F≤F max (11)

[0061] Right now

[0062] Take the safety factor K1 and safety factor K2 respectively (where K1 and K2 are generally 2-3 and can be adjusted accordingly according to different working conditions), then the appropriate range of the impeller pull rod tension F of the end face torque transmission is:

[0063]

[0064] Table 1 Symbols

[0065]

[0066]

[0067] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for calculating the tension control of the compressor impeller rod with end face torque transmission, characterized in that: The impeller pull rod tension F is the sum of the tension F2 to overcome the impeller deformation, the tension F3 to transfer the load, and the axial aerodynamic thrust F1 of the compressor impeller. The inlet pressure of the compressor impeller is higher than the exhaust pressure, and the wheel back pressure is greater than the pressure on the compressor impeller inlet side. Therefore, the aerodynamic thrust direction of the compressor impeller is from the wheel back to the impeller inlet end. The axial aerodynamic thrust F1 of the compressor impeller is obtained by software simulation. The impeller deformation under the centrifugal force is contraction. The impeller deformation is obtained by software simulation. The calculation formula for the pull rod force to overcome the impeller contraction deformation is: σ1=E×ε (1) A＝π×r 2 (3) From formula 1-3, it can be concluded that the pulling force F2 required by the tie rod to overcome the shrinkage deformation of the impeller is: F2=πEεr 2 (4) Where σ1 is the stress generated by the tension required by the tie rod to overcome the deformation of the impeller, ε is the shrinkage deformation of the impeller due to centrifugal force, E is the Young's modulus of the tie rod material, F2 is the tension to overcome the deformation of the impeller, A is the cross-sectional area of ​​the tie rod, and r is the radius of the tie rod; The compressor impeller and the main shaft produce friction to transfer the load. The residual preload required by the impeller tie rod is: The friction torque of the disk is: Where T is the torque of the impeller transmitting the corresponding power, P is the power transmitted by the impeller, n is the rotor speed, r1 and r2 are the inner and outer radii of the end faces of the main shaft and the compressor impeller, f is the friction coefficient of the joint surface between the compressor impeller and the main shaft, σ2 is the unit area pressure of the end faces of the main shaft and the compressor impeller, and F3 is the tensile force of the transmitted load; From formula 5-7, it can be concluded that the residual preload of the impeller required to transmit the corresponding power of the impeller is: The minimum tension allowed for the tie rod is: The maximum tension of the tie rod should make the tie rod stress less than its yield stress: F max =π×σ×r 2 (10) Then the force F range of the tie rod should be: F min ≤F≤F max (11) Right now Taking the safety factor K1 and the safety factor K2 respectively, the appropriate range of the impeller pull rod tension F for end face torque transmission is:

2. The method for calculating the tension control of the compressor impeller rod with end face torque transmission according to claim 1 is characterized in that: The value range of K1 and K2 is 2-3.

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