The theoretical computation model of the composite journal bearing sealed and lubricated with ferrofluid is established The oil film pressure distribution,temperature field and heat conduction equation of the bearing...The theoretical computation model of the composite journal bearing sealed and lubricated with ferrofluid is established The oil film pressure distribution,temperature field and heat conduction equation of the bearing liner are jointly calculated The static and dynamic properties of the bearing under condition of different eccentricities and ratios of width to diameter are obtained and discussed The results show the feasibility of this type of bearing for smaller eccentricities and width to diameter ratios,and that the oil film temperature,which is more subject to be influenced by the rotating speed,is higher than that of the bearing with leakage flow The key problem of the further development and application of the bearing is to design more reasonable and effective types of seal structures展开更多
Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engin...Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engine main journal bearings may provide a prediction of the bearing load and lubrication. Due to the strong non-linear features in bearing lubrication procedure, it is difficult to predict those characteristics. A non-linear dynamic model is described for analyzing the characteristics of engine main journal bearings. Components such as crankshaft, main journals and con rods are found by applying the finite element method. Non-linear spring/dampers are introduced to imitate the constraint and supporting functions provided by the main bearing and oil film. The engine gas pressure is imposed as excitation on the model via the engine piston, con rod, etc. The bearing reaction force is calculated over one engine cycle, and meanwhile, the oil film thickness and pressure distribution are obtained based on Reynolds differential equation. It can be found that the maximum bearing reaction force always occurs when the maximum cylinder pressure arises in the cylinder adjacent to that bearing. The simulated minimum oil film thickness, which is 3 μm, demonstrates the reliability of the main journal bearings. This non-linear dynamic analysis may save computing efforts of engine main bearing design and also is of good precision and close connection to actual engine main journal bearing conditions.展开更多
This paper, based on a simplified model, researched the problem of liquid lubricant leakage caused by thermal expansion effects in a self-sealed journal bearing, The analysis indi- cated that mismatch between thermal ...This paper, based on a simplified model, researched the problem of liquid lubricant leakage caused by thermal expansion effects in a self-sealed journal bearing, The analysis indi- cated that mismatch between thermal expansion coefficient of oil-holding-space in bearing, σ_T, and that of liquid lubricant, α_(oi), is a subtle factor inducing leakage when bearing temperature varies. Measures like properly selecting liquid lubricant and carefully designing bearing structure could be taken to reduce the leakage by matching α_T and α_(oil), Several such ideas concerning bearing mate- rial choosing and structure designing were presented.展开更多
A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for id...A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations： constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.展开更多
文摘The theoretical computation model of the composite journal bearing sealed and lubricated with ferrofluid is established The oil film pressure distribution,temperature field and heat conduction equation of the bearing liner are jointly calculated The static and dynamic properties of the bearing under condition of different eccentricities and ratios of width to diameter are obtained and discussed The results show the feasibility of this type of bearing for smaller eccentricities and width to diameter ratios,and that the oil film temperature,which is more subject to be influenced by the rotating speed,is higher than that of the bearing with leakage flow The key problem of the further development and application of the bearing is to design more reasonable and effective types of seal structures
基金supported by National Natural Science Foundation of China (Grant No. 60879002)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2006AA110112)
文摘Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engine main journal bearings may provide a prediction of the bearing load and lubrication. Due to the strong non-linear features in bearing lubrication procedure, it is difficult to predict those characteristics. A non-linear dynamic model is described for analyzing the characteristics of engine main journal bearings. Components such as crankshaft, main journals and con rods are found by applying the finite element method. Non-linear spring/dampers are introduced to imitate the constraint and supporting functions provided by the main bearing and oil film. The engine gas pressure is imposed as excitation on the model via the engine piston, con rod, etc. The bearing reaction force is calculated over one engine cycle, and meanwhile, the oil film thickness and pressure distribution are obtained based on Reynolds differential equation. It can be found that the maximum bearing reaction force always occurs when the maximum cylinder pressure arises in the cylinder adjacent to that bearing. The simulated minimum oil film thickness, which is 3 μm, demonstrates the reliability of the main journal bearings. This non-linear dynamic analysis may save computing efforts of engine main bearing design and also is of good precision and close connection to actual engine main journal bearing conditions.
文摘This paper, based on a simplified model, researched the problem of liquid lubricant leakage caused by thermal expansion effects in a self-sealed journal bearing, The analysis indi- cated that mismatch between thermal expansion coefficient of oil-holding-space in bearing, σ_T, and that of liquid lubricant, α_(oi), is a subtle factor inducing leakage when bearing temperature varies. Measures like properly selecting liquid lubricant and carefully designing bearing structure could be taken to reduce the leakage by matching α_T and α_(oil), Several such ideas concerning bearing mate- rial choosing and structure designing were presented.
基金Supported by National Natural Science Foundation of China(Grant Nos.51505384,51575421)Fundamental Research Funds for the Central Universities,China(Grant No.3102015JCS05007)Aeronautical Science Foundation of China(Grant No.20140453008)
文摘A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations： constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.
