Elliptical gear flow meters , also known as constant displacement flow meters or PD flow meters, are a type of flow meter with high accuracy, particularly suitable for measuring the flow rate of high-viscosity media. Elliptical gear flow meters utilize mechanical measuring elements to continuously divide the fluid into individual, known volume portions. The total fluid volume is measured by the number of times the measuring chamber is repeatedly filled and discharged into each volume portion. They can be manufactured from various materials (cast steel, stainless steel, and 316), and are suitable for flow measurement in industries such as chemical, petroleum, pharmaceutical, power, metallurgy, and food processing.
Before installing an oval gear flow meter, the pipeline should be cleaned. If the liquid contains solid particles, a filter must be installed upstream of the pipeline; if it contains gas, an venting device should be installed. There are no specific requirements for the straight pipe sections before and after the oval gear flow meter. It can be installed horizontally or vertically. During installation, the rotation axis of the oval gear of the flow meter should be parallel to the ground.
Working principle of oval gear flow meter
The measuring section of the LY-LC and AFLC series oval gear flow meters mainly consists of two meshing oval gears and their housing (measuring chamber). Under the pressure difference Δp = pl - p2 of the measured medium, the oval gears generate a torque that causes them to rotate. In position (a), since P1 > P2, the resultant torque generated by P1 and P2 causes wheel 1 to rotate clockwise, discharging the medium in the semi-circular volume between wheel 1 and the housing to the outlet, and driving wheel 2 to rotate counterclockwise. In this case, 1 is the driving wheel and 2 is the driven wheel. Position (b) shows the intermediate position, where both 1 and 2 are driving wheels. In position (c), the resultant torque of P1 and P2 acting on wheel 1 is zero, while the resultant torque acting on wheel 2 causes it to rotate counterclockwise, discharging the medium already drawn into the semi-circular volume to the outlet. In this case, 2 is the driving wheel and 1 is the driven wheel, exactly the opposite of the situation shown in (a). This cycle repeats continuously, with wheel 1 and wheel 2 alternately driving each other's rotation, discharging the measured medium from the inlet to the outlet in units of half-moon volume. Clearly, figures (a), (b), and (c) only represent the case where the elliptical gear has rotated 1/4 of a revolution, and the discharged measured medium is one half-moon volume. Therefore, the amount of measured medium discharged per revolution of the elliptical gear is four times the half-moon volume. Thus, the volumetric flow rate Q through the elliptical gear meteorometer is:
Q=4nυ0
In the formula:
n—rotational frequency of the elliptical gear (revolutions per second); υ0—volume of the crescent-shaped section (shells).
Thus, under the condition that the semi-circular volume υ0 of the elliptical gear flow meter is constant, the flow rate of the measured medium can be determined by measuring the rotational speed n of the elliptical gear.
The flow signal (i.e., the rotational speed n of the elliptical gear) of the elliptical gear flow meter can be displayed in two ways: local display and remote display.
