Research On Application And Lubricating Theory About Sliding Bearing On Heavy Duty And Low Revolution

With the advantages of energy saving, simple structure and high reliability, oil-film hybrid bearings have been widely applied in industries of power-generating, mineral-milling, cement-producing, etc. However, related researches are not systematic about oil-film bearing working on low-revolution and heavy-duty (LRHD), and there is gap between these researches and engineering. So, based on engineering application, this article systematically analyzed the lubricating mechanism of oil-film bearing on LRHD condition, and researched on related Reynolds equation and solved it numerically via computer programming, then summarized a design method.This article analyzed the lubricating characteristics of oil-film bearing on LRHD condition, and systematically made a theory about it. Because oil-film bearing in large size always has low revolution and heavy duty, the loading direction of oil film is nearly straight downward, and the sideslip angle was about 6 to 9 degrees. When the bearing rotates nominally, an oil wedge effect forms between its journal and rush, and there is a pressure distribution of the oil wedge separated to positive zone and negative zone with the position of thinnest film, so bearing works. However, the oil wedge fails to form when the bearing rotates with a low revolution especially at its starting and stopping step, hence oil with high pressure is pumped to the gap between journal and rush to raise the journal and an oil wedge forms forcedly. These bearings remarkably rotate nominally with dynamic pressure oil film and start and stop with static pressure oil film.This article listed the differential equations of dynamic pressure oil film and made its nondimensionalization, and solved it numerically. Based on the Reynolds equation of general fluid and the working characteristics of oil-film bearing on LRHD condition, the equations about dynamic pressure and static pressure oil film are obtained. Dynamic pressure characteristic equation is an elliptic equation, only in some special cases can obtain its analytical solution. This article firstly nondimensionalized the dynamic pressure equation, and obtained the general solution by differential numerical method, then, made the calculation software based on the visual basic language.This article verified reliability and accuracy of the solution combined with the engineering examples, and made a design chart. The pressure distribution of oil film under different sizes and working conditions can be calculated by the software, so bearing capacity can be obtained. The reliability of the calculation results was verified by an example of the main bearing of ball mill. Then this article analyzed the quantitative relations between bearing capacity and size, radial clearance, journal rotating speed, oil film thickness. Then it summed up a method of oil film bearing design, and according to the method, it concluded the size-capacity charts for engineering design.