When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly a ects the fr...When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly a ects the frequency response and control accuracy of the servo cylinder. Based on this partial load, increased friction can lead to cylinder bore scu ng, leakage, lack of output power, or even system failure. In this paper, a novel asymmetric static-pressure support structure is proposed based on the principle of hydrostatic support. The radial component force of a dynamic partial load is balanced by cooperation between the support oil cushion of the variable hydraulic pressure support structure, oil cushion of the supportive force, and the damper. Adaptive control of the servo cylinder piston rod, guide sleeve, and piston, as well as the cylinder oil film friction between lubricated surfaces is achieved. In this paper, theoretical design and analysis of the traditional hydrostatic bearing structure and novel structure are presented. A hydraulic dynamic shear scissor is used as a research target to derive a structural dynamic model. Comparative simulations are performed using Matlab Simulink. Additionally, flow field analysis of the novel structure is performed, which verifies the rationality and feasibility of the proposed structure and system.展开更多
Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per-...Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.展开更多
This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physi...This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physical and mathematical models are reasonable.The results show that the flame height and the excess air ratios depend on the system pressure drop but not on the absolute pressure at the combustion chamber.The pressure drop and the amount of combustion air have an inverse relationship with CO generation,and they also impact on the temperature and velocity fields.To reduce CO emission,a stronger fan is needed to provide extra pressure head to ensure that enough combustion air is introduced into the system.This study provides a useful research tool to develop products through computational fluid dynamic analysis and laboratory testing.展开更多
大尺寸汽轮机动压轴承与传统汽轮机以及其他常用的更小尺寸动压轴承相比,其尺寸更大、比压更高,并不完全符合经典润滑理论的层流假设,在估算其特性参数时需要进行进一步的研究。采用有限体积法,考虑滑油温黏效应和油膜空化效应,对某典...大尺寸汽轮机动压轴承与传统汽轮机以及其他常用的更小尺寸动压轴承相比,其尺寸更大、比压更高,并不完全符合经典润滑理论的层流假设,在估算其特性参数时需要进行进一步的研究。采用有限体积法,考虑滑油温黏效应和油膜空化效应,对某典型核电动压轴承在不同转速下的静态特性进行数值分析;对比层流和紊流模型以及不同空化模型得到的数值分析结果,并与文献数据进行比较。结果表明:Realizable k-Epsilon紊流模型结合Singhal et al.空化模型适用于该型动压轴承的模拟。在此基础上获得了大尺寸汽轮机动压轴承在不同转速下的油膜厚度规律、压力分布、温度分布、润滑油流量等静态特性规律以及轴承刚度阻尼动态特性数据。展开更多
基金Supported by Nation Youth Science Foundation of China(Grant No.51505315)Collaboration Innovation Center of Taiyuan Heavy Machinery Equipment and Shanxi Provincial Natural Science Foundation of China(Grant No.201701D221135)Innovative Project of Graduate Education in Shanxi Province of China(Grant No.2016BY132)
文摘When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly a ects the frequency response and control accuracy of the servo cylinder. Based on this partial load, increased friction can lead to cylinder bore scu ng, leakage, lack of output power, or even system failure. In this paper, a novel asymmetric static-pressure support structure is proposed based on the principle of hydrostatic support. The radial component force of a dynamic partial load is balanced by cooperation between the support oil cushion of the variable hydraulic pressure support structure, oil cushion of the supportive force, and the damper. Adaptive control of the servo cylinder piston rod, guide sleeve, and piston, as well as the cylinder oil film friction between lubricated surfaces is achieved. In this paper, theoretical design and analysis of the traditional hydrostatic bearing structure and novel structure are presented. A hydraulic dynamic shear scissor is used as a research target to derive a structural dynamic model. Comparative simulations are performed using Matlab Simulink. Additionally, flow field analysis of the novel structure is performed, which verifies the rationality and feasibility of the proposed structure and system.
文摘Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.
文摘This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physical and mathematical models are reasonable.The results show that the flame height and the excess air ratios depend on the system pressure drop but not on the absolute pressure at the combustion chamber.The pressure drop and the amount of combustion air have an inverse relationship with CO generation,and they also impact on the temperature and velocity fields.To reduce CO emission,a stronger fan is needed to provide extra pressure head to ensure that enough combustion air is introduced into the system.This study provides a useful research tool to develop products through computational fluid dynamic analysis and laboratory testing.
文摘大尺寸汽轮机动压轴承与传统汽轮机以及其他常用的更小尺寸动压轴承相比,其尺寸更大、比压更高,并不完全符合经典润滑理论的层流假设,在估算其特性参数时需要进行进一步的研究。采用有限体积法,考虑滑油温黏效应和油膜空化效应,对某典型核电动压轴承在不同转速下的静态特性进行数值分析;对比层流和紊流模型以及不同空化模型得到的数值分析结果,并与文献数据进行比较。结果表明:Realizable k-Epsilon紊流模型结合Singhal et al.空化模型适用于该型动压轴承的模拟。在此基础上获得了大尺寸汽轮机动压轴承在不同转速下的油膜厚度规律、压力分布、温度分布、润滑油流量等静态特性规律以及轴承刚度阻尼动态特性数据。
