Jet Control Valves

The principle of converting pressure into kinetic energy and then reconverting this energy into a controlled pressure can be utilized as a control means. The various types of jet control valves use this mode of operation. Proportional control is obtained beither deflecting or directing the high-velocity stream of fluid in relationship t.o a fixed receiving pressure element. These valves can use either a stationary jet or a movable jet.

An example of the stationary jet type of control valve is given by Fig. 1.31. The given valve was invented in 1929 by Mr. A. Luthy of Switzerland and used in controls produced by Escher Wyss, Ltd. The fluid jet originates in an ejecting nozzle which aims the fluid across a free air space directly into a receiving nozzle. Approximately half-way between the two nozzles there is located a knile-edge jet deflector, which is the controlling member of the valve. As the deflector edge is introduced into the free jet stream, the fluid is deflected away from the receiving nozzle so that less of the kinetic energy of the jet is converted into pressure within the receiving nozzle. The operation of the valve is dependent upon having a smooth and stable jet. Therefore, extreme care must be taken in the design and the manufacture of the ejecting nozzle 80 as to eliminate any roughness in the surface of the nozzle that might cause turbulence. Because of the p088ible turbulence problem, this type of valve is limited to low-preasure operation. With
proper line-up of the ejecting nozzle and the receiving nozzle, the impact of the jet will creat.e a maximum pressure in the receiving nozzle of about 95 per cent of the supply pressure to the valve.

stationary jet control valve

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