Objective Conventional capillary laminar flow measurement technology has nonlinear problems such as inlet and outlet pressure loss due to the structure of laminar flow sensing element. Therefore, it is necessary to improve the laminar flow sensor to solve the nonlinear problem.

Methods A conical laminar flow element was proposed, which could effectively solve the nonlinear pressure loss problem in the initial stage of laminar flow by taking advantage of direct pressure extraction in the fully developed stage of laminar flow and directly reflect the linear relationship between flow and differential pressure. Three kinds of conical laminar flow elements with different gaps were designed and manufactured, and the gas micro and small flow measurement system was built.

Results Within the flow range of 0.015 0-2.348 1 kg/h, the measurement errors of the three sets of devices are in the range of ±2%, and the measurement error of the conical laminar flow element device based on the gap of 0.7 mm is the smallest, in the range of ±1%.

Conclusion It is proved that the conical laminar flow element has good performance in measuring small and micro natural gas and other gas flow.