Development of a flow control valve with digital flow compensator

Abstract

Flow control valves typically use mechanical pressure drop compensator or dynamic flow meter to lessen the impact of pressure drop on outlet flow. However, there are some disadvantages, such as complex mechanical structure and small flow capacity. In this paper, a kind of digital flow compensator with bilinear interpolation algorithm is presented to compensate the pressure drop, in which the pressure drop and the desired outlet flow are the two input parameters. A two-stage proportional flow control valve with the proposed compensator is investigated. Pressure drop across the metering orifice of the valve is measured and fed back to the proposed compensator. If the detected pressure drop has deviated from the threshold, then the compensator will generate a compensation signal to adjust the poppet opening of the valve, which ensures that the output flow is independent of the pressure drop. Performances of the valve with the proposed compensator are investigated by simulation and experiment. Results show that it has a reasonable static control characteristics. In addition, there is no dead-zone in its steady flow curve; pressure drop have little impact on its output flow. Its dynamics will be affected by pressure drop and input voltage. Increasing pressure drop can improve system dynamics under constant input signal conditions. On the other hand, increasing input signal can shorten the poppet's closing time, but it will result in the longer opening time and the greater overshoot in the opening stage.