Sliding bearing matching design method of high-power-density supersonic centrifugal fan

Abstract

The invention discloses a sliding bearing matching design method for a high-power-density supersonic centrifugal fan, which comprises the following steps of: analyzing the stress condition of a sliding bearing according to designed input parameters, and acquiring the bearing capacity and the bearing direction of a support bearing of a high-speed centrifugal impeller rotating subsystem; calculating kinetic parameters of the sliding bearing based on design input parameters of the sliding bearing, judging whether the obtained kinetic parameters meet design requirements or not, and if yes, ending calculation; and if not, adjusting the design input parameters of the sliding bearing, and repeating the steps to recalculate the kinetic parameters of the sliding bearing until the design requirements are met. According to the method, the dynamic characteristics of the high-speed centrifugal impeller rotating subsystem are taken as an optimization object, and the parameters are efficiently optimized according to sensitivity analysis on the sliding bearing and rotor system structure parameters, so that the optimal sliding bearing design scheme can be obtained; and the dynamic characteristics of the sliding bearing and the bearing clearance and the bearing width-diameter ratio matched with the sliding bearing can be ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of bearings, and in particular relates to a sliding bearing matching design method for a high power density supersonic centrifugal fan. Background Art

[0002] The high-speed centrifugal impeller rotor system of a high-power density supersonic centrifugal fan has a relatively fast operating speed, and has high requirements on the bearing capacity and dynamic characteristics of the supporting bearings. The linear speed at the maximum rim of the centrifugal impeller can reach 1.5 Ma, and the performance needs to be matched with the structural design of the rotor system to obtain good high-speed stability and vibration characteristics, and to ensure that the high-speed centrifugal impeller rotor system has low vibration and can smoothly cross the critical speed. Therefore, the design of the supporting bearings of the high-speed centrifugal impeller rotor of a high-power density supersonic centrifugal fan is extremely critical, otherwise the performance of the bearings may not meet the high-speed stability of the high-speed centrifugal impeller rotor system, resulting in instability of the high-speed centrifugal impeller rotor system and destructive damage to the centrifugal impeller rotor system.

[0003] At present, the supporting bearings of high-speed centrifugal impeller rotor systems are mainly static pressure bearings, dynamic pressure bearings or dynamic-static composite sliding bearings, which have the following main disadvantages:

[0004] (1) The design of sliding bearings mainly considers the stress analysis, rotation speed, bearing clearance, lubricating oil viscosity and other parameters of the high-speed centrifugal impeller rotor system, and outputs the parameters such as the stiffness matrix, damping matrix, lubricating oil quantity and bearing temperature rise of the sliding bearing. Then, the dynamic calculation of the high-speed centrifugal impeller rotor system is carried out. If the dynamic characteristics meet the design requirements, the rotor design scheme is determined. Otherwise, the structure of the high-speed centrifugal impeller rotor must be optimized. This method only optimizes the structural parameters of the rotor, and does not match the sensitive parameters of the sliding bearing. This results in limited rotor structure optimization, poor optimization effect, long optimization cycle, and high cost.

[0005] (2) The assembly clearance value of the supporting bearing of the high-speed centrifugal impeller rotor system has a great influence on its high-speed stability. If the assembly clearance value is too small, the bearing temperature will be too high, and the journal and shaft will be easily scratched due to load fluctuations. If the assembly clearance value is too large, the bearing lubricating oil leakage will increase and the oil supply will increase. The bearing clearance value is generally set according to the experience value, which may affect the high-speed performance of the high-speed centrifugal impeller rotor system.

[0006] (3) The aspect ratio of the sliding bearing has a great influence on the dynamic characteristics of the high-speed centrifugal impeller rotor system. It is currently set based on empirical values ​​and has not been combined with the structural design. This will result in an inharmonious aspect ratio, affecting the high-speed stability of the high-speed centrifugal impeller rotor system. Summary of the invention

[0007] The purpose of the present invention is to provide a sliding bearing matching design method for a high power density supersonic centrifugal fan. The present invention takes the dynamic characteristics of a high-speed centrifugal impeller rotor system as the optimization object, and through the joint optimization of the sliding bearing parameters and the structural parameters of the high-speed centrifugal impeller rotor, according to the sensitivity of the dynamic characteristics of the high-speed centrifugal impeller rotor system to the structural parameters of the sliding bearing and the rotor system, the parameters are efficiently optimized, rather than simply modifying the structural parameters of the rotor system, so that the best sliding bearing design scheme can be obtained, the dynamic characteristics of the sliding bearing and the bearing clearance and bearing width-to-diameter ratio of the matching sliding bearing are guaranteed. In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] According to one aspect of the present invention, the present invention provides a sliding bearing matching design method for a high power density supersonic centrifugal fan, the sliding bearing matching design method comprising the following steps:

[0009] Analyze the stress of the sliding bearing according to the design input parameters to obtain the bearing capacity and bearing direction of the high-speed centrifugal impeller rotor system;

[0010] The dynamic parameters of the sliding bearing are calculated based on the design input parameters of the sliding bearing, and it is judged whether the obtained dynamic parameters meet the design requirements. If so, the calculation is terminated; the design input parameters include the rotation speed of the sliding bearing, the bearing clearance, the bearing aspect ratio, and the viscosity of the lubricating oil; the dynamic parameters include the stiffness, damping, bearing temperature rise and power loss of the sliding bearing;

[0011] If not, adjust the design input parameters of the sliding bearing and repeat the above steps to recalculate the dynamic parameters of the sliding bearing until the design requirements are met.

[0012] In the above scheme, further preferably, judging whether the obtained kinetic parameters meet the design requirements comprises the following steps:

[0013] According to the stiffness and damping of the sliding bearing design output, a dynamic calculation model of the high-speed centrifugal impeller rotor system is established together with the high-speed centrifugal impeller rotor, and the critical speed and unbalance response of the dynamic calculation model are calculated;

[0014] Compare the critical speed N with the rated speed n, and check whether the unbalanced vibration response at the critical speed meets the design requirements; if so, adjust the bearing clearance and width-to-diameter ratio of the sliding bearing according to the required bearing stiffness and damping to ensure the best dynamic performance of the sliding bearing and the high-speed centrifugal impeller rotor system;

[0015] If the requirements are not met, the support stiffness and damping of the sliding bearing and the rotor structure are adjusted, the dynamic calculation model of the sliding bearing and the high-speed centrifugal impeller rotor is updated, and then the dynamic calculation model is calculated again until the design requirements are met.

[0016] The above scheme is further preferred, if the magnitude relationship between the critical speed N and the rated speed n satisfies: critical speed N≤0.45n, and unbalanced vibration response Vrms≤4mm / s, then the dynamic characteristics of the high-speed centrifugal impeller rotor system meet the design requirements.

[0017] In the above scheme, the analysis of the stress condition of the sliding bearing comprises the following steps:

[0018] Determine the eccentricity and offset angle of the high-speed centrifugal impeller rotor according to the design input parameters, and then determine the calculation boundary conditions;

[0019] Based on the two-dimensional Reynolds equation of incompressible steady flow, the thickness of the dynamic pressure oil film is calculated. Then, the thermodynamic analysis module of ANSYS is used to solve the two-dimensional Reynolds equation and calculate the centripetal force F of the pressure oil film of the sliding bearing. e Tangential force distributed;

[0020] The centripetal force F of the oil film in the sliding bearing e Tangential force The supporting force of the rotor system is formed, and the centripetal force F of the dynamic oil film is calculated respectively. e and tangential force Among them, the centripetal force of the oil film is F e Tangential force Respectively meet:

[0021]

[0022] Where: F e is the centripetal force of the dynamic oil film, in N; F φ is the tangential force of the dynamic oil film, in N;

[0023] l is the length of the sliding bearing, in N mm; is the circumferential direction of the cylindrical coordinate system, the unit is rad;

[0024] is the starting angle of the dynamic oil film, in rad;

[0025] is the cut-off angle of the dynamic oil film, in rad;

[0026] r is the hole radius of the sliding bearing, in mm;

[0027] z is the length direction of the cylindrical coordinate system, in mm;

[0028] p is the dynamic oil film pressure, unit is Pa.

[0029] Determine whether the calculated eccentricity and deflection angle meet the design conditions. If so, end the calculation. If not, correct the deflection angle and recalculate the dynamic pressure oil film thickness and the centripetal force F of the oil film. e Tangential force distributed.

[0030] In the above scheme, the relationship between the eccentricity and the offset angle satisfies: eccentricity ε=eccentricity e / bearing radius clearance c; wherein the bearing radius clearance c satisfies:

[0031] c=rr s , where r is the hole radius of the sliding bearing, r s is the journal radius.

[0032] In summary, the invention adopts the above technical solution, and the invention has the following technical effects:

[0033] (1) According to the force analysis of the high-speed centrifugal impeller rotor, the present invention clarifies the design input parameters of the sliding bearing (rotating speed, bearing clearance, bearing width-to-diameter ratio, lubricating oil viscosity and other parameters), and then calculates the performance parameters of the sliding bearing based on the Reynolds equation, including the bearing support stiffness matrix, damping matrix, bearing temperature rise and power loss, etc. In addition, with the good dynamic characteristics of the sliding bearing-high-speed centrifugal impeller rotor system as the optimization goal, the sliding bearing performance parameters (bearing stiffness and damping) and the high-speed centrifugal impeller rotor structural parameters (centrifugal impeller weight, bearing span) are optimized to achieve the best dynamic performance. On the premise of ensuring the best dynamic characteristics of the sliding bearing-high-speed centrifugal impeller rotor system, the appropriate bearing clearance is matched, and the clearance is accurately controlled during the assembly process to meet the best dynamic characteristics. On the premise of meeting the good dynamic characteristics of the high-speed centrifugal impeller rotor system, the appropriate bearing width-to-diameter ratio is matched;

[0034] (2) The present invention couples the design of the sliding bearing with the design of the high-speed centrifugal impeller rotor, which can more effectively match the dynamic performance of the sliding bearing-high-speed centrifugal impeller rotor system. Through repeated iterative optimization, the bearing clearance of the sliding bearing is no longer a fixed value, but a calculated value that is highly matched with the sliding bearing-high-speed centrifugal impeller rotor system, which can ensure the optimal dynamic performance of the sliding bearing-high-speed centrifugal impeller rotor system.

[0035] (3) Through repeated iterative optimization, the width-to-diameter ratio of the sliding bearing is not a fixed value, but a calculated value that is highly matched with the sliding bearing-high-speed centrifugal impeller rotor system, which can ensure the optimal dynamic performance of the sliding bearing-high-speed centrifugal impeller rotor system;

[0036] (4) The present invention takes the dynamic characteristics of the high-speed centrifugal impeller rotor system as the optimization object, and through the joint optimization of the sliding bearing parameters and the high-speed centrifugal impeller rotor structural parameters, according to the sensitivity of the dynamic characteristics of the high-speed centrifugal impeller rotor system to the sliding bearing and the rotor system structural parameters, the parameters are efficiently optimized instead of simply modifying the rotor system structural parameters, thereby obtaining the best sliding bearing design scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a design flow diagram of a sliding bearing matching design method for a high power density supersonic centrifugal fan of the present invention;

[0038] Figure 2 is the centripetal force F of the oil film of the sliding bearing of the present invention e Tangential force Distribution diagram.

[0039] Figure 3 It is a schematic diagram of the position structure of the rotor structure and the bearing position of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the invention more clearly understood, the invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be realized even without these specific details.

[0041] Combination Figures 1 to 2 As shown in the figure, the present invention provides a sliding bearing matching design method for a high power density supersonic centrifugal fan, and the sliding bearing matching design method comprises the following steps:

[0042] Step 1: Analyze the force condition of the dynamic bearing according to the designed input parameters to obtain the bearing capacity and bearing direction of the support bearing of the high-speed centrifugal impeller rotor system; in the embodiment of the present invention, Figure 3 As shown, the calculation and analysis of sliding bearings includes the following steps:

[0043] Step 11, determining the eccentricity and offset angle of the high-speed centrifugal impeller rotor according to the designed input parameters, and then determining the calculation boundary conditions; the relationship between the eccentricity and the offset angle satisfies: eccentricity ε = eccentricity e / bearing radius clearance c; wherein the bearing radius clearance c satisfies:

[0044] c=rr s , where r is the hole radius of the sliding bearing, r s is the journal radius, and the eccentricity of ε is generally 0.6 to 0.8;

[0045] Step 12: Calculate the thickness h of the dynamic oil film based on the two-dimensional Reynolds equation for incompressible steady flow, and then use the thermodynamic analysis module of ANSYS to solve the two-dimensional Reynolds equation to calculate the centripetal force F of the oil film of the sliding bearing. e Tangential force Distribution; the thickness of the dynamic pressure oil film h satisfies:

[0046]

[0047] In the formula, h is the thickness of the dynamic oil film, in mm; μ is the dynamic viscosity of the lubricating oil, in pa·s;

[0048] p is the dynamic oil film pressure, Pa; Ω is the shaft speed, unit is m / s;

[0049] is the circumferential direction of the cylindrical coordinate system, the unit is rad;

[0050] z is the length direction of the cylindrical coordinate system, in mm;

[0051] Step 13: Use the centripetal force F of the oil film of the sliding bearing e Tangential force The supporting force of the rotor system is formed, and the centripetal force F of the dynamic oil film is calculated respectively. e and tangential force Among them, the centripetal force of the oil film is F e Tangential force Respectively meet:

[0052]

[0053] Where: F e is the centripetal force of the dynamic oil film, in N; F φ is the tangential force of the dynamic oil film, in N;

[0054] l is the length of the sliding bearing, in mm;

[0055] is the circumferential direction of the cylindrical coordinate system, the unit is rad;

[0056] is the starting angle of the dynamic oil film, in rad;

[0057] is the cut-off angle of the dynamic oil film, in rad;

[0058] r is the hole radius of the sliding bearing, in mm;

[0059] z is the length direction of the cylindrical coordinate system, in mm;

[0060] p is the dynamic oil film pressure, in Pa;

[0061] Step 14, determine whether the calculated eccentricity and deflection angle meet the design conditions. If so, end the calculation. If not, correct the deflection angle and recalculate the dynamic pressure oil film thickness and the centripetal force F of the oil film. e Tangential force Distribution; Through force analysis, we can clearly know the centripetal force Fe and tangential force of the sliding shaft The resulting support force distribution enables the rotor to operate stably and reliably;

[0062] Step 2, calculating the dynamic parameters of the sliding bearing based on the design input parameters of the sliding bearing, judging whether the obtained dynamic parameters meet the design requirements, and if so, ending the calculation; the design input parameters include the rotation speed, bearing clearance, bearing aspect ratio, and lubricating oil viscosity of the sliding bearing; the dynamic parameters include the stiffness, damping, bearing temperature rise and power loss of the sliding bearing; in an embodiment of the present invention, judging whether the obtained dynamic parameters meet the design requirements includes the following steps:

[0063] Step 21, based on the stiffness and damping of the sliding bearing design output, together with the high-speed centrifugal impeller rotor, a dynamic calculation model of the rotor system is established, and the critical speed and unbalance response of the dynamic calculation model are calculated;

[0064] Step 22, compare the critical speed N with the rated speed n, and whether the unbalanced vibration response at the critical speed meets the design requirements, that is, if the size relationship between the critical speed N and the rated speed n satisfies: the critical speed N≤0.45n, and the unbalanced vibration response Vrms≤4mm / s, then the dynamic characteristics of the high-speed centrifugal impeller rotor system meet the design requirements; if the requirements are met, the bearing clearance and the width-to-diameter ratio of the sliding bearing are adjusted according to the bearing stiffness and damping that meet the requirements to ensure the best dynamic performance of the sliding bearing and the high-speed centrifugal impeller rotor system; the dynamic characteristics of the high-speed centrifugal impeller rotor system meet the design requirements, if the above conditions are not met, it is necessary to adjust the structural parameters of the sliding bearing and the rotor structural parameters according to the sensitivity of the dynamic characteristics to the structural parameters until the above requirements are met; the dynamic parameters mainly consider the bearing stiffness and damping, or the rotor structure mainly considers the centrifugal impeller weight, bearing span, etc.;

[0065] Step 23, if the requirements are not met, adjust the support stiffness and damping of the sliding bearing and the rotor structure, update the dynamic calculation model of the sliding bearing and the high-speed centrifugal impeller rotor, and then calculate the dynamic calculation model until the design requirements are met, and obtain the appropriate bearing stiffness and damping according to the above steps, and then return to step 1, by optimizing the parameters such as the bearing clearance c and the aspect ratio B / d of the sliding bearing, until the required bearing stiffness K and damping C are obtained;

[0066] Step 3, if not, adjust the design input parameters of the sliding bearing, repeat the above steps to recalculate the dynamic parameters of the sliding bearing until the design requirements are met, thereby optimizing the parameters such as the bearing radius clearance c and the aspect ratio B / d of the sliding bearing until the required bearing stiffness K and damping C are obtained;

[0067] In the embodiment of the present invention, the above-mentioned calculation and analysis method is used to solve the key parameters such as the bearing capacity, minimum oil film thickness, and support stiffness and damping of the dynamic oil film according to the load and rotation speed of the ultra-high-speed centrifugal impeller rotor system, so as to obtain good dynamic characteristics; because the load of the ultra-high-speed centrifugal impeller rotor system is stable during operation, the radial load is mainly the dead weight of the rotor, and the bearing stiffness and damping at full speed are used as the calculation basis, so as to meet the engineering calculation accuracy requirements and make its deviation between 2% and 3%; because the bearing capacity of the dynamic oil film is obtained by integrating its pressure distribution P, the derivative of the pressure with respect to the displacement and velocity disturbance directly determines the dynamic characteristics of the dynamic oil film of the sliding bearing (the stiffness coefficient and damping coefficient of the dynamic oil film). According to the Reynolds boundary condition, at the rupture of the dynamic oil film Pressure is equal to zero, that is Then, eight dynamic characteristic coefficients of the hydrodynamic oil film of the high-speed sliding bearing are obtained, and their stiffness and damping coefficients are:

[0068]

[0069] In the present invention, the matching design of HGB500 sliding bearing-high-speed centrifugal impeller rotor system is taken as an example: the rotor structure of HGB500 and the bearing position are as follows: Figure 3 As shown in the figure, the rated speed of the fan is 16000rpm, the motor power is 500kW, the rotor weight is 56kg, and the journal is 60mm; according to the bearing support position, rotor weight and gear meshing force, the radial bearing capacity of bearing 1 and bearing 2 is 5400N and 4000N respectively. Based on the input parameters such as upper bearing capacity, speed, rotor journal, etc., the bearing clearance and bearing width-diameter ratio of the sliding bearing are preset, and based on the Reynolds equation, the performance parameters of the technical sliding bearing are obtained, and the stiffness and damping of the sliding bearing are obtained as shown in Table 1:

[0070] Table 1: Stiffness and damping parameters of sliding bearings

[0071]

[0072] According to the stiffness and damping values ​​of the above-mentioned bearings, a dynamic calculation model of the high-speed centrifugal impeller rotor system is established. The stiffness and damping values ​​of the supporting bearings are set, and calculations are performed to obtain the critical speed N of the high-speed centrifugal impeller rotor system and the unbalanced vibration response value Vrms at the critical speed N.

[0073] After calculation, it is known that the first-order critical speed of the rotor is 5712r / min, which is 35.7% of the rated speed. In the unbalanced response analysis, the vibration response Vrms at the critical speed is 1.18mm / s, which meets the design requirements. If it does not meet the design requirements, adjust the support stiffness and damping, rotor structure, etc. until the design requirements are met. According to the bearing stiffness and damping that meet the requirements, adjust the bearing clearance, width-to-diameter ratio and other parameters of the sliding bearing to ensure the best dynamic performance of the sliding bearing-high-speed centrifugal impeller rotor system.

[0074] The above is only a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the invention. These improvements and modifications should also be regarded as the scope of protection of the invention.

Claims

1. A sliding bearing matching design method for a high power density supersonic centrifugal fan, characterized in that: The sliding bearing matching design method comprises the following steps: Analyze the stress of the sliding bearing according to the design input parameters to obtain the bearing capacity and bearing direction of the high-speed centrifugal impeller rotor system; The dynamic parameters of the sliding bearing are calculated based on the design input parameters of the sliding bearing, and it is judged whether the obtained dynamic parameters meet the design requirements. If so, the calculation is terminated; the design input parameters include the rotation speed of the sliding bearing, the bearing clearance, the bearing aspect ratio, and the viscosity of the lubricating oil; the dynamic parameters include the stiffness, damping, bearing temperature rise and power loss of the sliding bearing; If not, adjust the design input parameters of the sliding bearing and repeat the above steps to recalculate the dynamic parameters of the sliding bearing until the design requirements are met.

2. The sliding bearing matching design method for a high power density supersonic centrifugal fan according to claim 1 is characterized in that: Judging whether the obtained kinetic parameters meet the design requirements includes the following steps: According to the stiffness and damping of the sliding bearing design output, a dynamic calculation model of the high-speed centrifugal impeller rotor system is established together with the high-speed centrifugal impeller rotor, and the critical speed and unbalance response of the dynamic calculation model are calculated; Compare the critical speed N with the rated speed n, and check whether the unbalanced vibration response at the critical speed meets the design requirements; if so, adjust the bearing clearance and width-to-diameter ratio of the sliding bearing according to the required bearing stiffness and damping to ensure the best dynamic performance of the sliding bearing and the high-speed centrifugal impeller rotor system; If the requirements are not met, the support stiffness and damping of the sliding bearing and the rotor structure are adjusted, the dynamic calculation model of the sliding bearing and the high-speed centrifugal impeller rotor is updated, and then the dynamic calculation model is calculated again until the design requirements are met.

3. The sliding bearing matching design method for a high power density supersonic centrifugal fan according to claim 2 is characterized in that: If the relationship between the critical speed N and the rated speed n satisfies: critical speed N≤0.45n, and the unbalanced vibration response Vrms≤4mm / s, the dynamic characteristics of the high-speed centrifugal impeller rotor system meet the design requirements.

4. The sliding bearing matching design method for a high power density supersonic centrifugal fan according to claim 1 is characterized in that: The analysis of the stress conditions of the sliding bearing includes the following steps: Determine the eccentricity and offset angle of the high-speed centrifugal impeller rotor according to the design input parameters, and then determine the calculation boundary conditions; Based on the two-dimensional Reynolds equation of incompressible steady flow, the thickness of the dynamic pressure oil film is calculated. Then, the thermodynamic analysis module of ANSYS is used to solve the two-dimensional Reynolds equation and calculate the centripetal force F of the pressure oil film of the sliding bearing. e Tangential force distributed; The centripetal force F of the oil film in the sliding bearing e Tangential force The supporting force of the rotor system is formed, and the centripetal force F of the dynamic oil film is calculated respectively. e and tangential force Among them, the centripetal force of the oil film is F e Tangential force Respectively meet: Where: F e is the centripetal force of the dynamic oil film, in N; F φ is the tangential force of the dynamic oil film, in N; l is the length of the sliding bearing, in mm; is the circumferential direction of the cylindrical coordinate system, the unit is rad; is the starting angle of the dynamic oil film, in rad; is the cut-off angle of the dynamic oil film, in rad; r is the hole radius of the sliding bearing, in mm; z is the length direction of the cylindrical coordinate system, in mm; p is the dynamic oil film pressure, unit is Pa. Determine whether the calculated eccentricity and deflection angle meet the design conditions. If so, end the calculation. If not, correct the deflection angle and recalculate the dynamic pressure oil film thickness and the centripetal force F of the oil film. e Tangential force distributed.

5. The sliding bearing matching design method for a high power density supersonic centrifugal fan according to claim 2 is characterized in that: The relationship between the eccentricity and the offset angle satisfies: eccentricity ε=eccentricity e / bearing radius clearance c; wherein the bearing radius clearance c satisfies: c=rr s , where r is the hole radius of the sliding bearing, r s is the journal radius.

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