J. R. Henry, "Design of Power Plant Installations, Pressure-Loss Characteristics of Duct Components." NACA Wartime Report L-208, June 1944.J. T. Higgenbotham, C. C. Wood, and E. F. Valentine, "A Study of the High-speed Performance Characteristics of 90"
适用范围
The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible.With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2. Athigher velocities and for large loss coefficients (Kt and 4fUD), compressible flow analysisshould be used.