Dynamic analysis of hydraulic turbine thrust bearing based on ANSYS

Kuang Tao and Qin Zhansheng

(School of Energy and Electricity, Hohai University, Nanjing, Jiangsu 21106)

Abstract: thrust bearing is an important part of a hydraulic turbine structure, and its running state is directly related to the operation of the hydraulic turbine.

It has a significant impact on safety and stability. Therefore, the dynamic simulation and structural analysis of the thrust bearing of hydraulic turbine are carried out.

It is of great significance to study the characteristics of thrust bearing in motion and provide theoretical support for real-time monitoring of thrust bearing. This paper introduces the internal kinematic relationship of hydraulic turbine bearing, establishes the finite element model of the bearing, simulates the movement process of the bearing by using the explicit dynamic module of ANSYS/LS-DYNA, and analyzes the stress and displacement distribution law of each component of the rolling bearing under normal conditions, which provides a theoretical basis for the normal operation of the hydraulic turbine thrust bearing.

Keywords: thrust bearing; Finite element analysis; Dominant dynamics; Dynamic simulation

5276 (2015) 01-0038-04 China map classification number: th133.33+1; TP39 1.9 Document ID: A ItemNo.: 167 1-

Dynamic analysis of steam turbine thrust bearing based on ANSYS

Kuang Tao, Qin Zhansheng

(School of Energy and Electrical Engineering, Hohai University, Nanjing 21106, China)

Abstract: Thrust bearing is an important part of hydraulic turbine structure, and its quality affects the safety and stability of hydraulic turbine.

Operation. Therefore, it is of great significance to carry out dynamic simulation and structural analysis and study its motion characteristics to provide theoretical support for real-time monitoring. The internal kinematics of turbine bearing is described, the finite element model of turbine bearing is established, and the motion of rolling bearing is simulated by ANSYS/LS-DYNA explicit dynamic module. Through the processing of the results by LS -PREPOST, the stress and displacement distribution of the bearing under normal working conditions are shown. It provides a theoretical basis for the smooth operation of steam turbines.

Keywords: thrust bearing; Finite element analysis; Dominant dynamics; Dynamic simulation

Figure 2

Local structural diagram of low-head turbine

.

Structural parameters of thrust ball bearing 5 1322

Value 13

Symbol physical meaning digital symbol physical meaning digital symbol physical meaning d

Bearing inner diameter110mm d 1 race inner diameter113mm.

z

Number of rollers

D bearing outer diameter 190mm D 1 collar outer diameter 187mm d z T.

Bearing height 63mm.

r

The radius of fillet is 2mm.

d r

Roller diameter14.85mm raceway diameter

15mm

Figure 3

Rotating loading process diagram

Three-dimensional solid 164 is selected as the finite element. In the process of grid division, the grid division adopts the combination of sweeping grid and mapping grid, and uses hexahedral elements. In order to simulate the boundary conditions, it is assumed that the surface interacting with other rigid structures is a rigid surface. Because the three-dimensional solid 164 element has no rotational freedom and cannot apply rotational speed, the rigid surface of bearing ring is set as thin shell 163 element to apply radial force and rotational speed. The finite element model of rolling bearing is shown in figure 1.

B) setting boundary conditions, material parameters and load parameters.

The materials of the shaft ring, the seat ring and the rolling elements are all GCr 15 steel, and the density is

2 1 1

7830kg /m, elastic modulus 2.06? 10Pa, Poisson's ratio is 0.

23; The cage is made of cold-rolled steel plate with a density of 7830kg /m and an elastic die.

1 1

The quantity is 1.96? 10Pa, Poisson's ratio is 0.24. In order to simulate the bearing fixture

Fig. 4 stress loading process diagram

Bearing seat fixed in working state, the rigid surface of the lower surface of bearing ring

set up

Mike Hein

building

Automatically generated, February 2015,44 (1): 38 41

39

Load the rotating speed from 0 to 136 rpm, and complete it within 0.5s (true water

The startup process of the turbine takes a long time, and the amount of calculation is too large, so the simulation effect is basically one), so it is set to 0.5s here. The stress did not change during the whole simulation process.

C) contact mode setting

Explicit analysis has no contact elements, which is different from implicit analysis.

It is necessary to define contact surface, contact type and contact related parameters for simulation.

Actual contact.

There are three kinds of contact when the rolling bearing works, namely, the contact between the rolling element and the raceway of the axle ring and the raceway of the seat ring, and the contact between the rolling element and the pocket hole of the cage.

. Therefore, automatic face-to-face contact is selected for analysis, and they are all face-to-face contact. According to the principle of specifying contact surface and target surface, the raceway table of axle ring is defined.

The raceway surface, raceway surface and cage pocket surface are the target surfaces, and the outer surface of the roller is 39 groups of contact pairs. According to the material properties and other parameters, the static friction coefficients of roller and raceway, collar and cage are 0.35 and 0.2, 0. 16 is 0.35, and the dynamic friction coefficients are 0. 16 and 0. 1 respectively.

Explicit dynamic analysis of three bearings

Figure 5

Equivalent stress nephogram of rolling bearing

According to the above finite element model, boundary and load conditions, the calculation time is 100ms, the output steps are 1000, and the post-processing adopts LS -PRE-POST. The calculation results are as follows.

1) Analysis of Equivalent Stress Distribution of Rolling Bearing Components

In order to reflect the whole process, as shown in Figure 5(a)- Figure 5(d), the equivalent stress nephogram of each part of 5 1322 bearing at 70ms, 85ms and 100ms is taken as 40 ms..

The equivalent stress nephogram of his moment is similar. The maximum equivalent stress of normal rolling bearing at 40ms and 70ms is 193.4MPa.

At 85ms, the maximum equivalent stress of the bearing is 349.9MPa and 336.8MPa.

The maximum equivalent stress at 100ms is 347.6MPa. Comparing the three diagrams, it can be seen that the greater stress of the bearing appears at the contact between the roller and the raceway and the collar.

Area, that is, the contact area between the roller and the shaft ring and the seat ring in the figure is darker in color. In the process of bearing operation, the maximum stress value and the maximum stress position change with the movement of the rolling elements.

.

In order to comprehensively analyze the stress of bearing system,

The equivalent stress nephogram of each element of the rolling bearing at 70ms is given, and the stress nephogram of other elements is similar, as shown in Figure 6(a)- Figure 6(d).

.

40 E-mail: zzhd @ chainajournal.net.cn "Mechanical Manufacturing and Automation"

Some necessary simplification, choose the appropriate unit type and material model, bearing.

The geometric model is established and the finite element model is generated by grid division. Then, effective constraints and loads are set according to the actual working conditions of the hydraulic turbine thrust bearing, and contact pairs are set to establish a good connection between bearing components. Finally, the dynamic simulation of bearing is completed in AN-SYS/LS-DYNA, and the results are post-processed in LS -PREPOST, and the simulation results are analyzed. The results show that:

1) The relatively large equivalent stress of bearings appears in rollers, collars and seats.

Fig. 6 Equivalent stress nephogram of bearing parts

In the contact area of the ring, the maximum stress appears at a certain depth below the contact surface and gradually attenuates outward. The contact stress of the ball bearing is elliptical on the contact surface.

2) In the working process of the bearing, the peak stress occurs at the contact position between the node and the collar and raceway, and is located on the surface of the roller. 3) During the operation of the bearing, the maximum stress value and the maximum stress position change with the movement of the roller, and the contact stress and stress level are roller, shaft ring, seat ring and cage in descending order.

4) Based on the simulation, the change characteristics of equivalent stress of bearing are analyzed. Using this method can accurately provide some data reference for the normal operation of bearings, and further analyze the faults of bearings on this basis, and provide more reliable data and theoretical basis for the safe operation of bearings. References:

[1] High purity. Explicit dynamic simulation and vibration characteristics analysis of rolling bearing faults.

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[8] Gao tenderness, Wang Chengdong, Miao Qiangji. Dynamic simulation and analysis of rolling bearing [J]

As can be seen from Figure 5- Figure 6, the roller, collar, seat ring and cage

At the same time, the maximum equivalent stress is different, among which the roller stress is the largest, which is 336.8MPa, followed by the axle ring 236.5MPa, the seat ring 222.9MPa and the cage 6 1.8MPa is the smallest. The greater stress of the roller appears in the contact area with the axle ring and the raceway, and the stress in the contact area between the roller and the raceway is greater than that in the contact area between the roller and the raceway. Shaft ring and race ring are the main parts of bearing that directly contact and bear the rolling elements, and their stress distribution is closely related to the stress distribution of the rolling elements. Therefore, the larger stress of the race and the race is also distributed in the contact area with the roller, and the stress distribution area on the contact surface is oval. The stress distribution of cage between pockets is relatively uniform, and the greater stress appears in the contact area between pockets and rollers. At the same time, as can be seen from the stress distribution in Figure 6(a), the stress peaks all appear at the contact position between the roller and the shaft ring and the race, which is located above the roller.

2) Contact analysis of rolling elements, race and shaft rings of rolling bearings.

In order to clearly reflect the contact between roller and raceway, displacement curves of some nodes are made in the post-processing of LS -PREPOST, from which the contact between roller and raceway can be clearly seen. As shown in fig. 7, the Z-direction displacement curves of the seat ring node 27793 and the axle ring node 7 149 are given.

.

Fig. 7 Z-direction displacement curve seat ring of the node on the collar,

2011:193-195. Mechanical design and manufacturing,

Huang Gangui, Deng, Teng. Present situation and development of simulation technology for rolling bearing system

j】。 Bearing, 2002 (4): 34-37. Exhibition [

Gao Hongbin. Research on structure and modal analysis of rolling bearing based on finite element method.

[J]。 Mechanical Engineering and Automation, 2007 (4): 90-92.

[1 1] Xiong Xiaojin, Zhang Xiao, Xiong Xiaoyan. Nonlinear finite element analysis of rolling bearing contact

[J]。 Journal of Testing Technology, 2009,23 (1): 23-27.09-29 Date of receipt: 20 13-

It can be clearly seen that the displacement is periodic because the model is based on the use of.

The purpose is to apply stress in the z direction. For the shaft link point, the peak is the displacement at the moment of contact with the roller, and the trough is the displacement farthest from the roller. Due to the influence of gap change and strain during the movement, the whole curve tends to move down. The case of raceway node is also the case that the peak is the contact torque and the valley is the torque farthest from the roller.

4 conclusion

Firstly, according to the actual situation of simulation, the thrust bearing of hydraulic turbine is made.

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4 1