Mechanism analysis and evaluation of thermal effects on the operating point drift of servo valves

Abstract

Operating point drift over large temperature spans can significantly degrade the performance of servo valves. The direction and magnitude of the deviation of the operating point are uncertain. To analyze and evaluate the mechanism of this complex system with a multi-level structure and multi-variables, it is necessary to construct a theoretical model with a clear physical concept to describe it. However, since the physical processes contain complex variations of structural parameters and flow properties, there is a problem of simplifying approximations in deriving analytical mathematical relations. The advantages of multi-physics field numerical analysis can compensate for this shortcoming of analytical formulations. Based on this, we constructed a whole-valve transfer function model to realize the mechanism analysis and evaluate the operating point drift when a thermal effect acts on a servo valve. The results show that the asymmetric fit relationship between the armature-nozzle assemblies is an important reason for the drift of the operating point caused by the thermal effect. Differences in structural parameters and fluid medium characteristics at different temperatures lead to nonlinear changes in the operating point. When the deviation angle reaches ±1°, an increase in temperature will cause the absolute value of the tangent slope of the displacement deviation of the spool to decrease from 1.44×10⁻⁵ m/°C to 1.25×10⁻⁶ m/°C. The influence of the deviation angle is reflected in the change in the absolute value of the tangent slope of the pressure deviation from 1. 14×10³ Pa/°C to 110 Pa/°C.

概要

目的:大温度范围内的工作点漂移会显著降低伺服阀的性能,但工作点偏差的方向和幅度具有不确定性。本文旨在建立一个清晰的理论模型物理概念来描述、分析和评估这个具有多层次结构和多变量机制的复杂系统。 创新点:由于物理过程包含结构参数和流动特性的复杂变化,因此在推导解析数学关系时存在简化近似的问题。本文采用的多物理场数值分析的优点可以弥补分析公式的这一缺点。 方法:在建立理论模型和进行数值分析的基础上,构建全阀传递函数模型,实现热效应作用于伺服阀时的机理分析和工作点漂移评估。 结论:1. 衔铁-喷嘴组件之间的不对称配合关系是热效应引起工作点漂移的重要原因。2. 不同温度下结构参数和流体介质特性的差异可导致工作点非线性变化。3. 当偏差角达到±1°时,温度升高会导致阀芯位移偏差的切线斜率绝对值从1.44×10⁻⁵减小到1.25×10⁻⁶ m/°C;偏差角的影响体现在压力偏差的切线斜率绝对值从1. 14×10³ Pa/°C到110 Pa/°C的变化。