【作者】 王颖；

【导师】 乐英；

【作者基本信息】 华北电力大学 ， 机械制造及其自动化， 2017， 硕士

【摘要】 汽轮机叶片是汽轮机中最重要的组成零件之一,对汽轮机工作效率有重要影响,目前汽轮机叶片的形状越来越复杂,扭曲的变截面叶片是常见的一种形状,如何提高扭叶片的加工质量和加工效率是目前研究热点。本文利用NURBS曲线曲面的理论知识对叶片进行了数学建模。为了达到叶片高速高质量的加工要求,深入研究了实时前瞻NURBS插补算法、基于牛顿迭代法的NURBS插补算法和速度自适应插补算法的基本理论和插补流程。速度自适应插补算法的速度跟弓高误差和曲率半径的大小有关,保证了加工精度;实时前瞻插补算法可以有效避免加速度超限,实现加工速度平滑;基于牛顿迭代法的NURBS插补算法对插补参数进行了计算优化,降低了进给速度波动率,从而保证了加工稳定性。然后以叶片的数学模型为基础,根据叶片横截面的结构特点选取叶片的顶部、中部和底部的横截面为研究对象,对叶片各截面同时采用实时前瞻NURBS插补算法、基于牛顿迭代法的NURBS插补算法和速度自适应插补算法进行数控插补仿真。为汽轮机叶片采用不同NURBS插补算法提高其加工质量和加工效率提供了理论依据。从仿真结果图中可以看出:利用实时前瞻NURBS插补算法、基于牛顿迭代法的NURBS插补算法和速度自适应插补算法对汽轮机叶片模型从弓高误差、进给速度、加速度和速度波动率等几个方面进行了分析比较,分析结果表明,相对于基于牛顿迭代法的插补算法和速度自适应插补算法,实时前瞻NURBS插补算法更能有效提高汽轮机叶片的加工质量和加工效率。更多还原

【Abstract】 The steam turbine blade is an important part of the steam turbine,and has an important influence on the efficiency of the stream turbine.It’s a common shape for stream turbine blade to be designed into complex and variable cross-section surface.Thus,ensuring the machining quality and efficiency of blade is very important.The paper researches theoretical knowledge of NURBS curves and surfaces,and uses the theoretical knowledge to establish the blade model.Meanwhile,in order to satisfy the requirements of high-speed and high accuracy blade processing,this paper researches three different NURBS curve interpolation algorithms.Through the case analysis,the characteristics of different interpolation algorithm have been illustrated.Then the paper bases on the mathematical model of blade,according to the structure characteristics of blade cross section,selecting different cross sections as the research object,adopting the three interpolation algorithms respectively.It provides a theoretical basis to improve the real machining quality and efficiency of turbine blade.It can be seen from the simulation results in the figure:the bottom,middle and top leaves using these three kinds of interpolation algorithms in interpolation simulation respectively,the curve trends of arch high error curve,the feed speed curve and acceleration curve and volatility curves are similar,Therefore,the interpolation result of whole blade can be known through the simulation results of the three different cross sections.These three kinds of interpolation algorithms can good meet the machining precision of blade,but synthesizing simulation results it is concluded that real-time preview NURBS interpolation algorithm is most suitable for high speed and high precision machining of the blade.更多还原