超高压压缩机管道内气流脉动的应变片测量方法研究

Study on Gas Pulsation Measuring Method by Strain Gauge for Ultra High Pressure Compressor Pipeline

由于超高压压缩机管道压力高,且很多介质为易燃易爆介质,出于安全性考虑,超高压管道的压力脉动一般不允许采用动态压力传感器侵入管道进行直接测量,只能采用间接测量的方法。本文对采用应变片测量管道表面应变,进而间接测量管道压力脉动的方法进行研究。首先,在静水压条件下,对管内压力—表面应变的关系进行标定。在该条件下,通过应变片测量得到的管内压力与管内实际压力的误差小于3%。然后,根据该标定关系对超高压压缩机管道的气流脉动进行测量。测量得到二级进气管道近气缸处脉动峰-峰值为21%,二级排气管道近气缸处的脉动峰-峰值为27%,脉动频率主要集中在前3阶。将测量得到的管内脉动压力作为振动激励,对二级进气管道振动应力进行有限元仿真。结果表明,有限元模型计算所得的管道表面应变与测量值在时域及频域特性上吻合较好。上述研究表明采用应变片测量压力脉动的方法具有一定的准确性,能较好地测量管道压力脉动的幅频特征,具有工程应用的可行性。

Due to high pressures,flammable and explosive medias,generally it is not allowed to use dynamic pressure sensors inserting into ultrahigh pressure pipeline to measure the pressure pulsation for safety reasons,and only indirect pressure measurement method can be used.Such a method using strain gauge was studied in this paper.Firstly,the relationship between the pressure in the pipeline and the surface strain of the pipeline was calibrated under the condition of hydrostatic pressure.Results show that the measurement error is less than 3%under the calibration conditions.Then,pressure pulsation in pipeline of an ultrahigh compressor was measured according to the calibration relationship.The measured results show that the pressure pulsation is 21%and 27%(peak-peak)at the suction and discharge pipeline near the second stage cylinder,respectively,and the first three order components are dominant.Vibration of the suction pipeline was calculated using FEM(Finite Element Method)based on the measured pressure pulsation as excitation force.The surface strain of the pipe solved by FEM matched well with the measured one both in time and frequency domain.Hence,the indirect pressure measurement method using strain gauge can be used in practical engineering.