低温工况润滑脂流变特性及本构方程研究

Research on Lubricating Grease Rheological Properties and Constitutive Equations at Low Temperature Conditions

润滑脂流变学行为与温度紧密相关,而流变行为决定润滑脂的本构方程。首先分别在不同温度工况下进行流变试验获得润滑脂流变学特性,并对低温工况进行研究;其次,基于Herschel-Bulkley、Power Law与Bingham本构方程对流变数据进行回归分析;最后,基于三种本构方程采用CFD方法深入分析润滑脂在管内的压力损失、粘度分布及速度分布规律。结果表明:在低剪切速率下,低温工况的剪切应力出现峰值,且润滑脂承受的最大剪切速率减小;不同工作温度下,三种本构方程回归精度均大于92%;Herschel-Bulkley本构方程粘度与速度计算结果均小于PowerLaw与Bingham本构方程;基于三种本构方程计算的速度在管道中心均出现明显的核流区域;Herschel-Bulkley本构方程压降计算结果最小。

The rheological properties which determines the lubricating grease rheological model is effected by temperature significantly. The rheological property under different temperature of lubricating grease is investigated using rotational rheometer firstly, and the rheological properties of greases are analyzed under low temperature;Secondly, the rheological data are regression studied based on the Herschel-Bulkley, Power Law and Bingham constitutive equations;Eventually, based on the three rheological models, the pressure drop, viscosity and velocity distribution are investigated by CFD. The results show that there is a largest shear stress under low temperature, and with decreasing the temperature, the maximum shear rate that the grease can bear is decreasing;the regression accuracy based on the three constitutive equations is greater than 92% under different temperatures;the viscosity and velocity calculated by Herschel-Bulkley rheological model are lower than the value simulated with Power Law and Bingham rheological models, and there has an obviously the plug flow region in the pipe center based on different rheological models;the pressure drop calculated by Herschel-Bulkley rheological model is minimum.