原型水泵水轮机压力脉动测量中的几个问题

Several Problems on Pressure Pulsation Measurements of Hydraulic Prototype Pump-Turbine

本文对水力机械压力脉动数据测量时的影响因素迚行了详细讨论,包括测量管路的条件、传感器的选型、数据采集系统要求以及信号采样频率的选择、采样时间长度的选择等若干问题。研究结果表明:测量管路长度L_c应由采样频率f_s和波速a_c应满足L_c≤0.1a_c/f_s,对于不满足条件的测量管路应重新评估测量条件;压力传感器的精度应不低于±0.1%;数据采集系统应采用不低于16位的模数转换装置;信号采样频率不低于两倍的有效信号频率的同时,所用的采样率应充分考虑采样后数据的分布情况不发生严重偏差;压力脉动数据采集时长应充分考虑长引水管路对测量结果的影响;在误差不超过5%的情况下,压力脉动的采样时间长度t_r与信号中所关注的频率f_i以及旋转周期N_r应满足公式:t_r≥N_r/f_i。本文研究结果亦为其它类型水力机械压力脉动测量提供了参考。

In this literature, several factors influencing pressure pulsation measurements of prototype pump-turbine have been discussed, including measuring pipe length, selection of pressure sensors, data acquisition system requirements, sampling frequency and sampling periods. The research indicates that: measuring pipe length L_c is determined by sampling frequency f_s and pressure wave speed a_c, and L_c complies the formula L_c≤0.1 a_c/f_s, and for the pipe length dissatisfies with the formula, the measurement should be re-estimated; the pressure sensor should have the accuracy not less than ±0.1%; the data acquisition system should have at least 16 bit analog/digital(A/D) converter; the sampling frequency should not less than twice signal effective frequency, meanwhile the data acquired by the sampling frequency should thoroughly reflect the data distribution; the recording period has close relation with the long water passage system(penstock and draft tube system), and within the error of ±5% the recording time t_r is determined by focused frequency f_i and rotating periods N_r, and t_r meets the formula t_r≥N_r/f_i. The research provides meaningful references for other hydraulic machinery pulsation measurements.