| 摘要 |
The proposed straight-tube Coriolis type mass flowmeter is shown on Fig. 2. Its design consists of a mechanically hard outer cylindrical enclosure 1. Inside the enclosure is a hollow string 2. String is attached to the hole on the left side of the enclosure. The measured substance flows inside the string through the left hole to the right one. Disc 3 is attached to the right end of the string. The outer diameter of the disc is equal to the inner diameter of the enclosure. This ensures that the disc can move only in the longitudinal direction and prevents string's cross movement. To the disc 3 and the right end of the enclosure 1 pre-stretched springs 4 are attached, so the string is stretched. Harmonic oscillator 6 by means of the actuators 7 causes the string to vibrate at its fundamental resonance frequency in a circular pass. The resonant frequency is adjusted by spring tension. To compensate small movements due to temperature changes, an elastic bellows 5 connecting the right end of the string and the enclosure are used. Sensors 8 convert string's cross movement in two mutually perpendicular directions into the electrical signals. These signals are processed by an electronic control unit 9. It contains analog-to-digital converter and a microprocessor, which uses the saved in read-only memory calibration tables or calibration equation and phase shift to calculate the mass flow and convert it into an electrical signal, to show it on the display. In this design springs are not exposed to the negative impacts of the measured substance, therefore, retain their stiffness over time, and as a result, may be made of material with stable mechanical properties, but poor corrosion resistance. |
