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采用双光束—双散射模式对气流的流速进行了测量,得到了多普勒频移信号,并对信号进行了滤波处理,提高了信噪比。滤波后的信号经数字相关处理器进行二值化和自相关运算处理后,得出气流的流动速度,进而得到时间函数曲线和速度分布直方图。将测量结果与某时刻速度的理论计算结果进行比较,测得速度与计算值偏差为0.3%,根据统计结果,测得速度的标准差为5.29%。最后对影响测量精度的因素进行了分析,通过前置滤波放大器降低了系统噪声,实验结果表明该方法对气流速度测量具有较高的精度。
The double beam - double scattering mode was used to measure the airflow velocity, and the Doppler frequency shift signal was obtained. The signal was filtered and the signal to noise ratio was improved. The filtered signal is binarized and autocorrelated by the digital correlation processor to obtain the flow velocity of the airflow, and then the time function curve and the velocity distribution histogram are obtained. The measured results are compared with the theoretical calculation results at a certain instantaneous speed. The deviation between the measured speed and the calculated value is 0.3%. According to the statistical results, the standard deviation of the measured speed is 5.29%. Finally, the factors affecting the measurement accuracy are analyzed. The pre-filter amplifier is used to reduce the system noise. The experimental results show that this method has higher accuracy for the measurement of airflow velocity.