Carmen vortex air flow meter principle

As we all know, when the field overhead wire is blown by the wind, it will produce a "bang, bang" sound, and the higher the wind speed, the higher the sound frequency, which is caused by the vortex (or eddy current) formed after the gas flows through the wire. Liquids, gases and other fluids will produce this phenomenon.

Similarly, if we place a vortex generator, such as a column, in the air intake, when the air passes through, the two columns in the rear of the vortex generator will continue to rotate in opposite directions and alternately appear. Whirlpool. This vortex is called Karman vortex.

The Karman vortex air flow meter utilizes this principle of vortex formation to measure the gas flow rate and directly reflect the air flow through the measurement of the flow rate.

For a specific Karman vortex air flow meter, there are the following relationship: qv = kf, qv is the volume flow rate, f is the frequency of a single column vortex, k is the proportionality constant, it is related to the pipe diameter, column diameter and so on. From this relation, the volumetric flow rate is proportional to the output frequency of the Karman eddy current sensor. Using this principle, we can determine the air flow by simply detecting the frequency f of the Karman vortex. According to the detection method of vortex frequency, automotive eddy current air flow sensors are classified into two types: ultrasonic detection type and optical detection type.