轮毂电驱动技术的研究是未来新能源驱动体系研究的重要方向。随着轮毂电驱动对转速的要求越来越高,搅油功率损失成为不可忽略的部分,甚至高达功率总损失的50%~80%。现有的计算搅油损失的方法主要是采用简单的经验公式,无法适用于复杂的...轮毂电驱动技术的研究是未来新能源驱动体系研究的重要方向。随着轮毂电驱动对转速的要求越来越高,搅油功率损失成为不可忽略的部分,甚至高达功率总损失的50%~80%。现有的计算搅油损失的方法主要是采用简单的经验公式,无法适用于复杂的行星齿轮传动。为此,采用计算流体力学(Computational Fluid Dynamics,CFD)软件与C语言用户自定义函数(User Defined Function,UDF)对两级行星齿轮传动飞溅润滑进行联合仿真,实现了油-气两相瞬态流场可视化;通过提取表面的压力和黏性力,得到了太阳轮、行星轮及行星架的搅油损失;对25种工况进行仿真与分析,得到了搅油功率损失随转速和浸油深度的变化趋势。结果表明,搅油功率损失随转速和浸油深度的增加而增大,且无明显的拐点,实现最小搅油损失应当在保证充分润滑的前提下取最小的浸油深度。展开更多
温湿度是评价文物保存微环境的重要因素。目前,基于文物预防性保护工作的要求产生了大量文物保存微环境监测数据。如何更好地分析、利用现有的数据,建立有效的数学分析模型,用以评估并优化现有的环境调控措施是预防性保护工作的重要课...温湿度是评价文物保存微环境的重要因素。目前,基于文物预防性保护工作的要求产生了大量文物保存微环境监测数据。如何更好地分析、利用现有的数据,建立有效的数学分析模型,用以评估并优化现有的环境调控措施是预防性保护工作的重要课题。本研究使用计算流体力学(computational fluid dynamics,CFD)的方法,建立能够反映展柜所处环境温度瞬态变化的三维CFD仿真模型,通过瞬态温度边界建模方法,将展柜外实测温度数据使用UDF(user defined function)编译,作为模型的瞬态边界条件。模型使用夏季工况的柜内温度实测数据进行标定,并将标定后的模型直接应用于冬季工况。结果表明,经标定后的模型在夏季工况中运行良好,模拟值与实测值间的平均偏差为0.18℃,最大偏差为0.33℃。模型直接应用于冬季工况,表现出很好的预测效果,模拟值与实测值之间的平均偏差为0.029℃,最大偏差为0.081℃,进一步验证了模型的有效性。本研究为预防性保护的监测数据利用及定量化研究提供了一种新的思路,同时证明了CFD技术在文物保护领域的广阔应用前景。展开更多
Journal bearings are important parts to keep the high dynamic performance of rotor machinery. Some methods have already been proposed to analysis the flow field of journal bearings, and in most of these methods simpli...Journal bearings are important parts to keep the high dynamic performance of rotor machinery. Some methods have already been proposed to analysis the flow field of journal bearings, and in most of these methods simplified physical model and classic Reynolds equation are always applied. While the application of the general computational fluid dynamics （CFD）-fluid structure interaction （FSI） techniques is more beneficial for analysis of the fluid field in a journal bearing when more detailed solutions are needed. This paper deals with the quasi-coupling calculation of transient fluid dynamics of oil film in journal bearings and rotor dynamics with CFD-FSI techniques. The fluid dynamics of oil film is calculated by applying the so-called ＂dynamic mesh＂ technique. A new mesh movement approacb is presented while the dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. The proposed mesh movement approach is based on the structured mesh. When the joumal moves, the movement distance of every grid in the flow field of bearing can be calculated, and then the update of the volume mesh can be handled automatically by user defined function （UDF）. The journal displacement at each time step is obtained by solving the moving equations of the rotor-bearing system under the known oil film force condition. A case study is carried out to calculate the locus of the journal center and pressure distribution of the journal in order to prove the feasibility of this method. The calculating results indicate that the proposed method can predict the transient flow field of a journal bearing in a rotor-bearing system where more realistic models are involved. The presented calculation method provides a basis for studying the nonlinear dynamic behavior of a general rotor-bearing system.展开更多
文摘轮毂电驱动技术的研究是未来新能源驱动体系研究的重要方向。随着轮毂电驱动对转速的要求越来越高,搅油功率损失成为不可忽略的部分,甚至高达功率总损失的50%~80%。现有的计算搅油损失的方法主要是采用简单的经验公式,无法适用于复杂的行星齿轮传动。为此,采用计算流体力学(Computational Fluid Dynamics,CFD)软件与C语言用户自定义函数(User Defined Function,UDF)对两级行星齿轮传动飞溅润滑进行联合仿真,实现了油-气两相瞬态流场可视化;通过提取表面的压力和黏性力,得到了太阳轮、行星轮及行星架的搅油损失;对25种工况进行仿真与分析,得到了搅油功率损失随转速和浸油深度的变化趋势。结果表明,搅油功率损失随转速和浸油深度的增加而增大,且无明显的拐点,实现最小搅油损失应当在保证充分润滑的前提下取最小的浸油深度。
文摘温湿度是评价文物保存微环境的重要因素。目前,基于文物预防性保护工作的要求产生了大量文物保存微环境监测数据。如何更好地分析、利用现有的数据,建立有效的数学分析模型,用以评估并优化现有的环境调控措施是预防性保护工作的重要课题。本研究使用计算流体力学(computational fluid dynamics,CFD)的方法,建立能够反映展柜所处环境温度瞬态变化的三维CFD仿真模型,通过瞬态温度边界建模方法,将展柜外实测温度数据使用UDF(user defined function)编译,作为模型的瞬态边界条件。模型使用夏季工况的柜内温度实测数据进行标定,并将标定后的模型直接应用于冬季工况。结果表明,经标定后的模型在夏季工况中运行良好,模拟值与实测值间的平均偏差为0.18℃,最大偏差为0.33℃。模型直接应用于冬季工况,表现出很好的预测效果,模拟值与实测值之间的平均偏差为0.029℃,最大偏差为0.081℃,进一步验证了模型的有效性。本研究为预防性保护的监测数据利用及定量化研究提供了一种新的思路,同时证明了CFD技术在文物保护领域的广阔应用前景。
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA04Z413)Zhejiang Provincial Natural Science Foundation of China (Grant No. Y1110109)
文摘Journal bearings are important parts to keep the high dynamic performance of rotor machinery. Some methods have already been proposed to analysis the flow field of journal bearings, and in most of these methods simplified physical model and classic Reynolds equation are always applied. While the application of the general computational fluid dynamics （CFD）-fluid structure interaction （FSI） techniques is more beneficial for analysis of the fluid field in a journal bearing when more detailed solutions are needed. This paper deals with the quasi-coupling calculation of transient fluid dynamics of oil film in journal bearings and rotor dynamics with CFD-FSI techniques. The fluid dynamics of oil film is calculated by applying the so-called ＂dynamic mesh＂ technique. A new mesh movement approacb is presented while the dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. The proposed mesh movement approach is based on the structured mesh. When the joumal moves, the movement distance of every grid in the flow field of bearing can be calculated, and then the update of the volume mesh can be handled automatically by user defined function （UDF）. The journal displacement at each time step is obtained by solving the moving equations of the rotor-bearing system under the known oil film force condition. A case study is carried out to calculate the locus of the journal center and pressure distribution of the journal in order to prove the feasibility of this method. The calculating results indicate that the proposed method can predict the transient flow field of a journal bearing in a rotor-bearing system where more realistic models are involved. The presented calculation method provides a basis for studying the nonlinear dynamic behavior of a general rotor-bearing system.
