Control of the Bulk Condensation Rate in a Radial-Type Refrigeration Turbine Stage by Changing the Initial Temperature

Abstract

The problem of deep purification of industrial gases of various impurities is urgent. Two-phase turbomachines with bulk condensation of the impurity in the flow path are proposed as an alternative to the known methods (i.e., adsorption and absorption technologies). The study is devoted to numerical simulation of the process of bulk condensation in the flow path of a radial-type refrigeration turbomachine, which is controlled by changing the initial temperature of the flow. The calculations were performed for a mixture of air as an incondensable gas carrier and carbon dioxide as an impurity. It has been demonstrated that the process of bulk condensation proper and its depth (the actual range of operating conditions) can be controlled by changing the gas mixture temperature at the stage inlet. The conditions have been determined at which the process is localized predominantly in the impeller channels that is the safest regime from the standpoint of the risk of erosive wear and subsequent damage to the stage elements. For the first time, the reduction in the isentropic efficiency per percent of the degree of condensation, should it occur, was numerically estimated for refrigeration turbomachines. The obtained data are close to the values for wet steam turbines presented in the literature. A procedure for calculating the characteristic and analyzing the results has been developed. It yields the optimal regimes using a multicriteria search with the requirements for the region where the phase transition should occur, and for the radius of the particles. It is shown that increasing/decreasing the stage inlet temperature may be insufficient to meet the specified requirements for the degree of condensation and isentropic efficiency offering deep purification of gases of impurities. Therefore, assessment is required as to whether the process rate can be controlled by changing the expansion ratio and/or the impeller speed, both individually and in combination.