压力测试平台在燃料泵送系统中的应用

针对燃料泵送系统存在的水击压力过大、气液分离不足以及汽蚀等问题，采用压力传感器和数字信号采集系统建立燃料泵送系统压力测试平台。根据测得的压力信号，对燃料枪关闭瞬间流量、管长、溢流阀调定压力以及主阀弹簧刚度对水击效应引起的峰值压力的影响进行研究，并通过频率分析方法和小波分析方法较精确地获得系统的气液分离值和临界汽蚀压力点。该测试平台不仅能实时可靠地对系统压力进行定量诊断与识别，同时还可以为燃料泵送系统的性能优化提供依据。

Nonlinear Dynamic Characteristics of NC Table

The actions of nonlinear spring force and nonlinear frictional force on dynamic characteristics of NC table were emphatically studied by means of theoretical analysis and experimental verification. NC table was subjected to several kinds of forces such as axial forces, transverse forces, torques, frictional forces and cutting forces etc. Values of every kind of spring stiffness were intimately related to the support types of ball screw. Stiffness values varied with displacement and moving direction of NC table and shown nonlinear regulations such as soft spring property or hard spring property. The varying regulation of frictional force obeyed Streibeck curve. The conclusions are drown,that the effect of nonlinear spring can be described by Duffing equation, the effect of nonlinear frictional force can be described by van der Pol equation, and their coupling effect can be described by Lienard equation. The jump phenomenon caused by soft or hard spring property and the self-excited vibration and creep phenomenon caused by nonlinear frictional force make the stable zone of systemic responses complex.The jump phenomenon takes place under condition that the exciting frequency is close to the natural frequency and the creep phenomenon takes place under condition that the NC table moves at lower speed and in poor lubrication. The existence of limited cycles shows that nonlinear factors are stable factors to limit the unstable phenomenon expend infinitely. 