Study On The Lubricity Of Rape-seed Biodiesel And Its Blends With Diesel Oil

The adoption of low sulfur diesel(LSD) with the aim of reducing the deleterious matters in the emission of diesel poses the problem of poor lubricity. The poor lubricity of LSD leads to the fail of the key parts which depends on the lubricity of fuel in the diesel. Biodiesel draws the attention of the public as the sanitary and reproducible substitute and additive of fossil diesel. As have been verified, the physical properties of biodiesel have the best resemblance to the fossil diesel, the power performance of biodiesel when used as fuel in the diesel is similar to that of fossil diesel and the emission behavior is better than that of fossil diesel. The research on the lubricity of biodiesel and the mechanism, discipline, lubricity of its blends with fossil diesel has important realistic significance on the base of other norms satisfied.The rape-seed biodiesel is taken as the object of the research of the essay. The lubricity of rape-seed biodiesel and its blends with 0# diesel sold in the market is studied using the mechanism of wear and lubrication as the foundation and experiment and theory analysis as the method. The research on the inherent lubricity of rape-seed biodiesel is firstly carried on the reciprocating wear tester. The two kinds of fuels are used as the lubricant of the specimens. The method of Ferrography, SEM, stereo microscope and the measure of weightlessness of wear are used to analyze the lubricity of the two kinds of fuels. At the same time, in order to make pointed study on the plunger and barrel assembly whose lubrication mainly depends on the lubricity of the fuels used, wear tester of plunger and barrel assembly is made.The rape-seed biodiesel,0# diesel oil and the blends with different volume ratio of biodiesel in it are used in the experiments on the wear tester of plunger and barrel assembly. The real-time friction force between the upper and lower specimens is measured during the experiment. The real-time curve of friction force-displacement is also drawn in the experiment with the aim of analyzing the lubricity of different fuels. At last, the free fatty acid in the fuels are analyzed by gas chromatograph and the results provides the reasons for the lubricity of biodiesel in the perspective of boundary lubrication. In the term of theoretical analysis, the mathematical models of piston ring- cylinder and plunger-barrel are established. The analytic solutions of friction force, flow capacity of lubricating oil and etc are deduced. The results are compared with that of the experiments. Through the experiments and theoretical analysis above, the lubricity of rape-seed biodiesel and 0# diesel, the reason for the lubricity are studied. The basic discipline and the influence factors are found. The research provide scientific experiment data and theoretical foundation for the research, usage and popularization of rape-seed biodiesel as fuel and additive for fossil diesel oil in internal combustion engine.The following conclusions are got through the research.1,The inherent lubricity of rape-seed biodiesel is better than that of fossil diesel oil.2,The lubricity of the blends becomes better and better with the increase of the volume ratio of biodiesel in it. The effect of lubricity enhancement become less obvious when the volume ratio is higher than 20%. The effect of anti-wear of the fuel gets worse with the decrease of the relative velocity of the moving parts.3,The experiment of GC indicates that the content of free fatty acid is one of the reasons for the better lubricity of biodiesel and the fuel that has biodiesel in it.4,The results of the measuration of the viscosity of fuels and the analysis theoretical modeling show that the viscosity of biodiesel is higher than that of other fuels and that of the blends gets bigger with the increase of volume ratio of biodiesel in it. The higher viscosity avoid the direct contact of the friction pairs and the friction force between the friction pairs is lower. The results of the analysis are coincident with that of the experiments.