涡轮流量计时间常数校准技术研究

为了校准涡轮流量计的时间常数，建立液体阶跃流量试验装置，该装置利用螺杆泵输送流体形成平台流量，采用内啮合齿轮泵输送流体形成阶跃流量分量，通过控制高速电磁阀的开启与关闭实现阶跃流量分量与平台流量的叠加，最终产生阶跃流量。利用皮托管对阶跃流量产生时间进行评估，结果表明阶跃流量上升时间小于9 ms。在不同阶跃工况下对涡轮流量计开展时间常数校准试验，结果表明：涡轮流量计时间常数并非固定值，且受平台流量影响较大，具有随前平台流量增大而减小的趋势，受阶跃流量幅度影响较小；在小流量范围内，实际测量得到的动态流量系数与理论模型推导得到的动态流量系数偏差较大，而在大流量范围内二者较为吻合。最后对时间常数校准结果进行了不确定度评估，最大扩展不确定度约为10 ms（k = 2）。研究成果有助于评估流量计动态特性，有望提高非稳态流量测量的准确度。

Experimental study on time constant calibration technology of turbine flowmeter

In order to calibrate the time constant of the turbine flowmeter, a liquid step flow test device was established. The device uses a screw pump to transport fluid to form a platform flow, and an internal meshing gear pump to transport fluid to form a step flow component. The step flow component is superimposed on the platform flow by controlling the opening and closing of the high?speed solenoid valve, and the step flow is generated ultimately. The generation time of the step flow was evaluated by using a pitot tube, and the result showed that the rise time of the step flow was less than 9 ms. The time constant calibration tests of turbine flowmeter were carried out under different step conditions, and the results showed that the time constant of the turbine flowmeter was not invariable, and was greatly affected by the steady flow before the step flow, with a trend of decreasing with the increase of the steady flow before the step change, and the time constant was less affected by the step flow amplitude. In the small flow range, the dynamic flow coefficient obtained from actual measurement deviated significantly from the theoretical model derivation, while in the large flow range, the two were more consistent. Finally, the uncertainty of the calibration result of the time constant was evaluated, and the maximum expanded uncertainty was about 10 ms (k = 2). The research results are helpful for evaluating the dynamic characteristics of flowmeters and are expected to improve the accuracy of unsteady flow measurement.