I. Overview

The fluid Rectifier traditional long-term research and practice has become mature, the general barrier-separated flow to adjust the speed of distribution channels, so as to achieve the purpose of rectifying; Rectifier mainly used for this type of laboratory and flow calibration system . However, this method easy to plug the cause dirt and increase resistance loss, in the industrial pipeline rarely used.
Vortex flowmeters because of its unique properties, has been subject to attention and to have a wide range of applications, but there are still two aspects of the problem of people, first because of resistance pipeline flow meters upstream of the interference, a distortion flow And affect the normal allocation from the vortex. In order to overcome the flow disturbance, meters long before the need for compatibility straight pipes (normally 15 to 40 times the diameter of the pipe length), whereas in reality it is very difficult to meet the scene. Second, the vortex flowmeter is one of the main features of wide range, generally about 10:1, it should be said that this wide range should be relatively good performance, but in practical industrial applications, much lower than the maximum flow of the instrument Values, the minimum flow will be lower than the instrument is often the lower limit, a number of instruments in the regular flow near the lower limit, causing the accuracy of the measurement instruments decline, the weaker signal at this time, the instrument of anti-disturbance capacity has fallen. In order to measure small flow, people often use intracavity shape for the Park of Taiwan's traditional adjustable, after necking improve the measurement of the flow. Vortex Flowmeter to work within the framework of the normal flow rate, but adjustable, the size of the structure (for the general length of the diameter of three to five times), at the same time, because of the fluid flowing through adjustable, adjustable Department A large number of rotating flow corporations, increased local resistance losses, but also in the flow distortion. So to be adjustable between the installation of meters and more than 15 times the diameter of the length of straight pipes for rectification, and increase the resistance losses along the way (as shown in Figure 1), this method increased construction costs, but also to Processing, installation of the inconvenience. End-use of special-shaped vertical line of adjustable Rectifier (f declaration of national patents), a rectifier, and improve the flow velocity changes in the distribution of multiple roles, and the structure of small size, the length of the diameter of only 1 / 3, the card can be loaded directly The two ends of the instrument, not only do not need another additional direct channels, but also can lower the upper reaches of the instrument straight pipe requirements. Experiments show that: Instrumentation upstream resistance of a plane for the two 90 bend under normal circumstances, Vortex Flowmeter upstream side should be the installation of more than 20 times the diameter pipeline length of the straight pipes, and the installation of Vortex Flowmeter The adjustable Rectifier greatly reduce the upper reaches of measuring the length of straight pipe requirements, its resistance far smaller than the traditional adjustable tube. More importantly, can the original minimum flow rate reduced to 1 / 3, compared to 15:1 range above.
Second, the theory and analysis
First of all it should be noted that the traditional adjustable tube can After necking, and supported by a smaller-diameter flowmeters to achieve the purpose of measuring small flow, but this method can not expand the range than the instrument, because it changes at the end of the pipeline Velocity distribution. We know that the vortex flow meter and deduced the theory is based on the infinite in uniform get in the flow field, and in the actual closing of the pipe, but the non-uniform flow, velocity cross-section of the distribution is a rotating parabolic, although a reasonable choice Columnar so that the cylinder on both sides of the arch-velocity distribution uniform, but in fact, the process pipeline rotating parabolic distribution of the velocity is an objective reality. Experiments show that in the relatively large flow, the less affected, the impact of this or that to the extent permitted, but with the decline in traffic, the impact of increasing, from the large number of calibration data, the instrument is always with the constant flow The decrease with the increase. This shows that the sampling points of the average velocity and velocity difference is increasing.