MODELING THE CHARACTERISTICS DURING THE FLOW OF A SUBCOOLED LIQUID OUT OF GEOMETRICALLY SIMILAR LAVAL NOZZLES

To design hydrosteam turbines of the Segner-wheel type, it is necessary to have reliable characteristics of a Laval nozzle with a large expansion ratio when water strongly subcooled to a saturation temperature is fed to the nozzle. The authors have given a review of a number of works on determining the fl ow-rate coeffi cient μ and the coeffi cient of velocity ϕ when water subcooled to a saturation temperature fl ows out of Laval nozzles. The complexity of the process of outfl ow of a steam–water mixture has been noted, which is dependent on the relation of the temperature and pressure at entry into the nozzle, pressure behind the nozzle and the nozzle expansion ratio, and the confi guration of the entrance region. Experimental data have been given on blowdowns of geometrically similar nozzles with measuring the jet thrust and determining the fl ow-rate and velocity coeffi cients. It has been shown that the linear dimensions of the nozzle throat do not infl uence μ when a constant relation of the length of the throat to its diameter is observed. The velocity coeffi cient during the outfl ow of a boiling liquid depends on the linear dimensions of the expanding section of the nozzle, i.e., testing of geometrically similar nozzles do not ensure a correct determination of . It has been shown that the nozzles' effi ciency must be compared in the design regime when the pressure on the exit section is equal to the pressure in the chamber where the steam–water mixture fl ows. Analysis results will be useful for calculating and designing a reaction hydrosteam turbine.
To design hydrosteam turbines of the Segner-wheel type, it is necessary to have reliable characteristics of a Laval nozzle with a large expansion ratio when water strongly subcooled to a saturation temperature is fed to the nozzle. The authors have given a review of a number of works on determining the fl ow-rate coeffi cient μ and the coeffi cient of velocity ϕ when water subcooled to a saturation temperature fl ows out of Laval nozzles. The complexity of the process of outfl ow of a steam–water mixture has been noted, which is dependent on the relation of the temperature and pressure at entry into the nozzle, pressure behind the nozzle and the nozzle expansion ratio, and the confi guration of the entrance region. Experimental data have been given on blowdowns of geometrically similar nozzles with measuring the jet thrust and determining the fl ow-rate and velocity coeffi cients. It has been shown that the linear dimensions of the nozzle throat do not infl uence μ when a constant relation of the length of the throat to its diameter is observed. The velocity coeffi cient during the outfl ow of a boiling liquid depends on the linear dimensions of the expanding section of the nozzle, i.e., testing of geometrically similar nozzles do not ensure a correct determination of . It has been shown that the nozzles' effi ciency must be compared in the design regime when the pressure on the exit section is equal to the pressure in the chamber where the steam–water mixture fl ows. Analysis results will be useful for calculating and designing a reaction hydrosteam turbine.
Author:  O. O. Mil′man, A. S. Goldin, B. A. Shifrin V. B. Perov, A. V. Ptakhin, V. S. Krylov, A. V. Kondrat′ev
Keywords:  Laval nozzle, effi ciency, throat, fl ow-rate coeffi cient, velocity coeffi cient, expansion ratio, reactive force, pressure, temperature, steam–water mixture
Page:  1296