JPH0213933Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Technical Field) This invention relates to a positive displacement flowmeter suitable mainly for measuring the flow rate of gas.

(Prior Art) Generally, when measuring the volumetric flow rate of air or other gas, condensed liquid such as mist contained in the gas tends to accumulate between the rotor and the casing.
This causes fluid friction, increases the rotational torque of the rotor, and as a result, there is a problem in that the accuracy of measuring small flow rates decreases.

Apart from these problems, we have also solved the inconvenience of fluid leaking from the gap between the rotor and the casing.
JP-A-57-73624 discloses an invention in which a groove or a small hole with a bottom is provided in the gap between the rotor and the casing to provide a labyrinth effect, thereby improving the accuracy of measuring small flow rates. In other words, the fluid that is pressurized into the gap between the rotor and the casing expands rapidly in the groove or small hole with a bottom, causing a pressure drop, and the energy is lost due to the sealing effect, that is, the labyrinth effect. The aim is to improve accuracy in reducing fluid leakage. Therefore, although the grooves or bottomed small holes in this conventional example are formed on the end face of the rotor, they do not have the function of extending to the outer periphery and discharging fluid.

(Summary of the invention) This invention focuses on the above-mentioned points, and also creates radial grooves in the contact surface of the rotor with the casing, which is completely different from the technical configuration of the known example, and creates a gap between the rotor and the casing. Condensed liquid such as mist accumulated in the rotor is scattered in the circumferential direction of the rotor by the centrifugal force phenomenon caused by the rotation of the rotating body, eliminating disadvantages such as liquid friction, reducing rotational torque, and improving measurement accuracy for small flow rates. The present invention relates to obtaining a positive displacement flowmeter that can improve the flow rate.

In addition, this invention provides a positive displacement flowmeter that can be applied not only to small-sized but also large-sized flowmeters with various structures such as roots-type flowmeters and oval gear flowmeters (trade name: oval flowmeter). Pertains to.

(Example) An example of this invention will be described below with reference to the drawings.

Reference numeral 1 indicates a casing in which a pair of rotors 2 and 3 are rotatably disposed, and 4 indicates a measuring chamber of the casing 1, in which a fluid inlet 5 and a fluid outlet 6 are opened. Reference numeral 7 denotes a desired rotational speed extraction mechanism, which together with the casing 1 forms a flow meter main body a. Reference numeral 8 indicates a liquid discharge groove such as mist formed in the contact surface 9 of both or one of the rotors 2 and 3 with the casing 1. They are scattered radially in straight lines or curved lines such as arcuate lines toward the outer periphery of the area.

By the way, as shown in FIGS. 1 and 2, the liquid discharge grooves 8 extend radially in a straight line or an arcuate line over the entire area from a point in contact with the rotating shaft 10 to a point on the outer periphery of the rotors 2 and 3. Of course, as shown in FIG. 3, it is conceivable to have a configuration in which the installation is scattered over the entire area from locations slightly distant from the rotating shaft 10 to locations on the outer periphery of the rotors 2 and 3. The latter configuration is preferable in consideration of fluid leakage. Further, although the rotors 2 and 3 described above are elliptical gear rotors, any rotor may be used as long as it constitutes another positive displacement flowmeter such as a Roots rotor.

Note that the reference numeral 11 indicates a fluid inflow connection, and the reference numeral 12 indicates a fluid outflow connection.

The action will be explained based on the above structure.

First, the flow meter main body a is connected to a desired gas transfer conduit via the fluid inflow connection section 11 and the fluid outflow connection section 12 to allow the gas to be measured to flow.

By the way, it is known that gases, such as commercially available gases, generally contain vaporized moisture, and when they are subjected to temperature changes during transportation, dew condenses and accumulates in the pipes.

Therefore, while measuring the desired gas to be measured, vaporized moisture contained in the gas dews and liquefies in the gap between the rotors 2 and 3 and the casing 1. However, this condensed water flows into the radial liquid discharge grooves 8 of the rotors 2 and 3 and at the same time flows out of the rotors 2 and 3 through the grooves 8 due to the centrifugal force phenomenon based on the rotational action of the rotors 2 and 3. It can be effectively discharged by being scattered in both directions. As a result, measurement accuracy can be significantly improved in the measurement range of minute flow rates.

(Effect of the invention) According to this invention, the liquid condensed in the gap between the rotor and the casing is removed by the centrifugal force of the rotor through the radial liquid discharge grooves provided on the surface of the rotor on the casing side. Since it is designed to scatter and discharge to the outside of the rotor due to the phenomenon, it eliminates inconveniences such as friction between the rotor and casing caused by liquid such as dew water, and reduces the rotational torque of the rotor. This has the advantage of providing smooth rotational action and improving the accuracy of measuring minute flow rates.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the positive displacement flowmeter according to this invention, and Fig. 2 is a side view showing the structure of one side of a pair of rotors, taken along the - line. FIG. 3 is a side view showing the structure of a pair of rotors showing another example. 1...Casing, 2, 3...Rotor, 8...
Liquid drain groove, 9...contact surface.

Claims (1)

[Scope of utility model registration request] The end face of the rotor, which rotates in proportion to the flow rate in the measuring chamber, is provided with grooves extending radially from the rotating shaft to the outer periphery to drain liquid that has condensed between the rotor and the end face of the measuring chamber. A positive displacement flowmeter that measures gas.