Action of the Fluid in the Air-Micrometer : 4th Report, Characteristics of Double-Disc Nozzle No. 2, In the Case of Compressibility Being Considered

Abstract

Using the same double-disc nozzles as in the third report, their discharge characteristics as high-pressure type air-micrometer were investigated under the following conditions : (1) The pressure difference up to 3 kg/cm2 (2) The range of pressure ratio from 0.25 to 0.85 (3) The ratio of gap to inner diameter up to 0.1 The results are summarized as follows : 1. In using a double-disc nozzle available for the high-pressure type air-micrometer, there may occur two regions depending on the pressure ratio, the ratio of outer to inner diameter of nozzle, the inner diameter itself and the gap. In one region the viscous friction loss is prominent but in the other it is not. 2. Almost satisfactory empirical formulas which express the product of the discharge coefficient and the expansion factor, cε, were obtained for these two regions.