| 摘要 |
998, 938. Automatic flow control. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Aug. 1, 1963 [Aug. 3, 1962], No. 30613/63. Heading G3R. In a system for automatically controlling the ratio of two rates of flow, electric pulses having repetition rates corresponding to each rate of flow operate switches to charge condensers and discharge them into a common reservoir condenser controlling the ratio, a further condenser being charged from a voltage dependent on some other variable of the material and discharged into the reservoir condenser to modify the control effect. In Fig. 1 flow meters F A , F B are respectively associated with pipes A, B the flowing media in which may be gasolene to be blended. Electric pulses produced by the flow meters at repetition rates dependent on the rates of flow are caused to operate switches O A , O B so that condensers C A , C B are respectively charged to voltages corresponding to the rates of flow and discharged in opposition into a reservoir condenser C so that any difference, reprepresenting a change in the flow ratio, is effective to adjust a valve controlling the rate of flow in pipe A. The desired ratio is set by means of a potentiometer R 1 P controlling the charging voltage of condenser C A . In order to introduce a variation of this ratio in dependence on another variable of the medium, such as viscosity, vapour tension, conductivity or temperature (e.g. for constant mass flow), the other variable is caused to vary a voltage E 2 , and an auxiliary condenser C E is periodically charged from this voltage and discharged into reservoir condenser C by a switch O E operating synchronously with switch O A . Alternatively switches O E and O B may be synchronized, in which case it is desirable to arrange for adjustment of voltage Eg when potentiometer R 1 P is adjusted or to supply condenser C A through a potentiometer instead of condenser C B . A bridge circuit, Fig. 4 (not shown), having preset resistors and resistors dependent on the temperature of the media, may be arranged to produce the voltage Eg variable with temperature for mass flow ratio control. Further auxiliary condenser circuits may introduce control in dependence on more than one additional variable. Maintenance of the relative rates of flow of more than two streams is also referred to. |
