No abstract

When a PIV flowmeter is used to measure a large flow of natural gas, the flow field fluctuation and particle distribution have a significant influence on the measurement accuracy and the particle injection mode plays a key role in the flow field fluctuation and particle distribution. To improve the measurement accuracy of PIV flowmeters, the method of filling tracer particles in single pipes, multiple pipes, and L pipes of a natural gas DN100 pipeline under high-pressure working conditions was compared and analyzed through numerical calculation and testing. The results show that the disturbance distance of filling particles in L pipes was the shortest, but the particle distribution area was small, whereas the flow metering error was large. By shortening the intersection distance between the L tube injection flow field and the main flow field, the problem that the particles failed to fill the test area was effectively solved, and the peak turbulence intensity at the intersection of the flow field decreased from 13.4% to 8%. Furthermore, the optimized structure was used to measure a flow of 100–600 m3/h with different flow rates. The relative error between the flowmeter and the ultrasonic flowmeter was approximately 2%, and the metering deviation was significantly improved.

To measure the natural gas flow in the natural gas pipeline, a flow measurement method based on a laser Doppler velocimeter (LDV) is proposed, and the flow field in the natural gas pipeline is accurately measured. The flow laws of the flow field in the pipeline are obtained. In this paper, the influence of the jet flow on the flow field in the main pipe during the injection of tracer particles is analyzed by numerical calculations, and the reliability of the calculation is verified by the LDV test. The results show that the influence of the jet on the flow field in the main pipe weakens rapidly within a short distance, which provides good conditions for measuring the flow in the LDV test pipeline. The error between the flow measured by LDV and the turbine standard device is within 0.47%. Meanwhile, the uncertainty of the LDV measurement test system of a natural gas pipeline is evaluated. The system uncertainty is less than 2%, which satisfies the uncertainty requirements of the metering system, verifying the feasibility of the LDV metering flow and providing a reliable basis for the accurate metering of natural gas.