External Cylindrical Nozzle with Controlled Vacuum

There is a developed design of the external cylindrical nozzle with a vacuum camera. The paper studies the nozzle controllability of flow rate via regulated connection of the evacuated chamber to the atmosphere through an air throttle. Working capacity of the nozzle with inlet round or triangular orifice are researched. The gap is provided in the nozzle design between the external wall of the inlet orifice and the end face of the straight case in the nozzle case. The presented mathematical model of the nozzle with the evacuated chamber allows us to estimate the expected vacuum amount in the compressed section of a stream and maximum permissible absolute pressure at the inlet orifice. The paper gives experimental characteristics of the fluid flow process through the nozzle for different values of internal diameter of a straight case and an extent of its end face remoteness from an external wall of the inlet orifice. It estimates how geometry of nozzle constructive elements influences on the volume flow rate. It is established that the nozzle capacity significantly depends on the shape of inlet orifice. Triangular orifice nozzles steadily work in the mode of completely filled flow area of the straight case at much more amounts of the limit pressure of the flow. Vacuum depth in the evacuated chamber also depends on the shape of inlet orifice: the greatest vacuum is reached in a nozzle with the triangular orifice which 1.5 times exceeds the greatest vacuum with the round orifice. Possibility to control nozzle capacity through the regulated connection of the evacuated chamber to the atmosphere was experimentally estimated, thus depth of flow rate regulation of the nozzle with a triangular orifice was 45% in comparison with 10% regulation depth of the nozzle with a round orifice. Depth of regulation calculated by a mathematical model appeared to be much more. The paper presents experimental dependences of the flow coefficients of nozzle input orifice on the vacuum depth in the chamber. Research findings allowed us to express opinion that accepted in the works on "Fluid Mechanics " equality of pressure values in the center of cross-stream gravity and in its surrounding steam-gas medium is incorrect. The paper shows a possibility to create the nozzle design with updated device to connect a chamber to the atmosphere by the air throttle, which is flow pressure-controlled thus providing the nozzle operation as the flow rate stabilizer. The publication supplements information on nozzles provided in literature on " Fluid Mechanics". The developed design of the external cylindrical nozzle with controlled vacuum and of research results of its working capacity can be taken into consideration in designing hydraulic systems and devices of hydro-automatic equipment.

external cylindrical nozzle with evacuated chamber, fluid flow through triangular orifice, flow capability of the nozzle, controlled vacuum in the chamber

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