抄録
Critical flow nozzles are commonly used as gas flow measuring instruments. However, this device has not received the degree of users acceptance it deserves, probably primarily because of the lack of a convenieht source of design data.
This paper presents essential datum for designing a small critical flow nozzle to be used as a standard of gas flow rate. The relation between the nozzle dimensions such as the entrance radius, the throat length, the exit diffuser angle, and the discharge coefficient is experimentally studied and it is found that the ratio of throat diameter to its length gives a great effect to discharge coefficient and that the other factors do not count so much.
From this result, a geometrically similar nozzle is designed and a certain relation between the Reynolds number and the discharge coefficient is obtained. The conclusion is that the discharge coefficient can be inferred by utilizing this relation if the nozzle is geometrically similarly made.
