武汉理工大学毕业设计（论文）

面向车载显示屏印刷制造的基板气浮转移控制研究

学院（系）： 国际教育学院

专业班级： 车辆gj1601

学生姓名： 熊镜凯

指导教师： 邓小禾

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作者签名：熊镜凯

2020年 5月 28日

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Abstract

Nowadays, the vehicle mounted display shows the trend of large-scale development. Therefore, the stability of substrate transfer is particularly important in the printing and manufacturing process of vehicle mounted display screen. The traditional roller transmission system has been gradually eliminated because of the inevitable vibration in the transportation process. At present, both domestic and foreign manufacturers use the contactless air flotation platform to complete the transmission of printing substrate.

According to the different ways of pressure supply, the air flotation platform is divided into positive pressure air flotation platform and negative pressure adsorption air flotation platform. In this paper, a simple model of the air flotation platform is established firstly, and the grid division and simulation calculation of the basin are carried out by using CFD (Computational Fluid Dynamics) technology, and the working modes of the two air flotation platforms are simulated by modifying the boundary conditions. The simulation results show that the pressure distribution in the air film of the negative pressure adsorption air flotation platform is more uniform, which is suitable for the transfer of the printing substrate of the vehicle mounted display screen. At the same time, the simulation results show that the simple model of air flotation platform can not achieve the ideal throttling effect, and the pre throttling device is needed. In this paper, we continue to build a new model of "broken line" restrictor. The simulation results show that the restrictor has good capacity of throttling and stabilizing pressure. After changing the geometric parameters of the restrictor, the simulation results show that the cross-sectional area of the restrictor has the greatest impact on the throttling effect of the restrictor. Then the simple model of air floating platform is modified, and the improved model of air floating platform is established. After simulation and post-processing, the stability of air membrane in the basin is proved to be improved. After changing the air supply pressure, film thickness and other parameters of the negative pressure adsorption air flotation platform, the change law of its static characteristics is explored, and the conclusion is drawn: the largest pressure drop in the basin occurs in the "broken line" throttler; the mass flow at the inlet and outlet remains conservative; the bearing capacity and mass flow of the negative pressure air flotation platform are relatively affected by the positive pressure of air supply and film thickness.

Key word: air floating platform; CFD simulation; throttle; air film

Catalogue

Chapter 1 Introduction 1

1.1 Research background 1

1.2 Brief introduction of air flotation platform 4

1.3 Research status at home and abroad 5

1.3.1 Research status of ink jet printing at home and abroad 5

1.3.2 Research status of air flotation platform at home and abroad 7

1.4 Research purpose and significance 9

1.5 Main contents of the paper 9

Chapter 2 Theoretical basis of air flotation platform 11

2.1 Basic properties of fluid 11

2.1.1 Ideal fluid and viscous fluid 11

2.1.2 Laminar flow and turbulence 11

2.1.3 Sound speed and Mach number 11

2.2 Basic equations of fluid motion 12

2.2.1 Continuity equation 12

2.2.2 Navier Stokes equation 12

2.2.3 The momentum equation 12

2.2.4 Energy equation 13

2.2.5 Ideal gas state equation 13

2.3 Working principle and throttling method of aerostatic bearing 13

2.4 Theoretical derivation of air flotation platform 16

2.4.1 Gas flow in a tube 16

2.4.2 Compressed gas enters the gas film through the orifice 17

2.4.3 Compressed gas enters the gas film through the orifice 19

2.5 Loss of gas flow 20

2.6 Summary of this chapter 21

Chapter 3 CFD numerical simulation of air flotation table 22

3.1 An overview of computational fluid dynamics 22

3.2 Pre calculation 23

3.2.1 Derivation of negative pressure adsorption carrier unit model 23

3.2.2 Simple model construction of air flotation carrier unit 25

3.2.3 Finite element mesh generation 26

3.3 Fluent simulation calculation 28

3.3.1 Solvers and algorithms 29

3.3.2 Turbulence model setting 30

3.3.3 Relaxation factor 30

3.3.4 Boundary condition 30

3.3.5 Convergence judgment 31

3.4 Post-processing 32

3.4.1 Post-processing of negative pressure adsorption carrier unit 33

3.4.2 Post-processing of positive pressure air flotation carrier unit 38

3.5 Summary of this chapter 40

Chapter 4 Optimization of air flotation carrier unit 41

4.1 Throttling characteristics of " broken line " restrictor 41

4.1.1 Modeling of "broken line" single orifice restrictor 41

4.1.2 Mesh generation of "broken line" single orifice throttle model 42