Multi-objective optimization design algorithm of dynamic and thermal performances of high speed spindle bearing
A multi-objective optimization design algorithm model for dynamic and thermal properties analysis of high speed spindle bearing is constructed. Stiffness of bearing can be obtained by solving equilibrium equations of inner ring of bearing. Heat generation of the high speed ball bearing is studied by analyzing the local friction in the bearing considering coupling of dynamic properties, a new model for evaluating bearing temperature is set up treating the contact surfaces between rolling elements and raceways as moving heat sources. Based on this model, multi-objective optimization of stiffness and temperature rising of high speed spindle bearings are studied. Pareto-optimal solution of high speed spindle bearing are given.
Operating temperatures in mist lubricated rolling element bearings for gas turbines
In addition to geometry and environmental factors, the operating temperatures of bearings are directly affected by the applied load, the operating speed, the friction torque, and the lubricant type and viscosity. If heat dissipation is not adequate, the bearing system temperature will increase to the point that the lubricant is distressed, ultimately leading to bearing failure. Current studies are investigating both mist and vapor phase lubrication which have the potential to increase lubricant operating temperature from 200/spl deg/C for a conventional recirculating polyolester liquid to as high as 600/spl deg/C for a tertiary-butyl phenylphosphate. The primary benefit of these lubrication methods is the potential to reduce the lubricant on-board storage requirements, in particular for expendable engine applications. However, this technique removes the primary mode for heat rejection, and the bearing operating temperature may become the critical factor for life considerations. A process has been developed to numerically investigate the operating temperature of a rolling element bearing using the finite element method. Predicted steady-state temperature responses for a 30 mm ball bearing operating with mist lubricant delivered at 325/spl deg/C for three different shaft operating speeds are presented. This analysis process can be used to evaluate thermal conditions and to determine cooling requirements for future bearing system designs.
Quantitative and qualitative relationship between swirl burner operatingconditions and pulverized coal flame length
Abstract Currently, there are used in power plants two types of burners to combustion the pulverized coal: jet burners and swirl burners. Most of the published works in the field of analysis of burners operating conditions are related to jet burners and are limited to initial region of the flame at the outlet of the burner. For jet burners an offset between the burner outlet and the flame beginning point could be analyzed. In the case of swirl burners with the pre-mixing diffuser chamber an offset between flame ignition point and burner outlet is usually not visible. Because already in the pre-mixing diffuser chamber of swirl burner occurs the ignition of coal-dust together with oxidant-gas cloud and thereby the formation of the flame. Therefore, the analysis of operating conditions for this types of burners requires a different approach. There is a lack of researches, in which will be analyzed changes of the flame length, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. Therefore the aim of this study was to implement and verify the methodology for estimating the flame length, which will allow monitoring changes of operating conditions, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. To carry out the analysis of the image of the coal flame, the two algorithms have been presented. This two algorithms, being based on the video images of the coal flame allows to specify and detect the end point of the flame and on that basis the length of the flame, as well as the fluctuation changes of flame length can be later determined. Both, the change thermal loads of coal burner, streams of secondary air, as well as the constructional change of the angle of swirler assemblies, resulted in distinct changes in the length of the pulverized coal flame.