Research on the design and characteristics of gap-type laminar flow modules based on small gas flow rates

Due to the numerous problems of traditional laminar flowmeters, such as poor linearity, complex processing and usage, and the susceptibility of component structures to fluid influence, a laminar flow generator based on a conical structure was designed. By adding cones on both sides of a straight pipe for fluid diversion and selecting pressure tapping points on the two cones to reflect the linear relationship between flow and differential pressure, the working principle of the conical laminar flow measurement device was derived based on the differential pressure flow measurement method and combined with the double-cone flowmeter. A corresponding flow measurement structural model and calculation formula were established. In the conical laminar flow measurement device, the gap between the straight pipe and the pipe was designed in two sizes, namely 0.1 mm and 0.05 mm, and flow measurement was conducted in a 55 mm diameter pipe. The measurement experiments for air medium were carried out under the working condition flow range of 0.0006 to 0.006 m 3 /h. Within this range, the measurement errors of both devices were less than ±0.91%, and the measurement error of the conical laminar flow measurement device with a 0.1 mm gap was the smallest, less than 0.6%. There is a clear linear relationship between the flow and differential pressure based on the conical laminar flow measurement device, indicating that this device can effectively overcome the non-linear influence of traditional laminar flow-meters.