| 摘要 |
The invention is related to a method and an apparatus for measuring the flow velocity of a flow, stream or jet of molten radiation emitting material, in particular a freely falling jet of molten glass. The intensity of the radiation emitted from a limited section (2, 3) of the material flow is detected by means of two radiation detectors (S1, S2) at two separate locations mutually spaced apart by a given distance (L) along the flow path of the material flow. All pulse-like amplitude variations having an amplitude exceeding a given magnitude are discriminated from the output signals of the two radiation detectors. These pulse-like amplitude variations originate from randomly occurring, local, discrete, short variations in the intensity of the radiation emitted by the material flow caused by randomly occurring inhomogeneities in the material, for instance in the form of air bubbles in a jet of molten glass. The time interval between a pulse-like amplitude variation in the output signal from the up-stream detector (S1) caused by an inhomogeneity in the material flow (1) and the occurrence of a pulse-like amplitude variation in the output signal from the down-stream detector (S2) caused by the same inhomogeneity in the material flow, is measured and used as a measure of the time taken by the material flow to travel between the detector locations, for calculating the flow velocity of the material flow. Also the volumetric flow rate of the material flow can be determined by measuring also the diameter of the material flow with the aid of a linear array of photodiodes and calculating the volumetric flow rate on the basis of measured values of the flow velocity and the diameter. |
