Dependents of velocity distribution in exit section of converging channel on shape of inlet channel in regulating valve

The design of regulating valves for steam turbines, specifically the problem of profiling their inlet channel, is analyzed theoretically from the standpoint of achieving the optimum velocity distribution in the exit section of the converging channel. Limit (maximum-flow) valves with quasiconical stem are considered, their capacity being 50% higher than that of globe valves under the same pressure head. Smooth acceleration of the vapor stream up to nominal velocity is found to be attainable by replacement of the cylindrical channel segment with a converging one and by thus lengthening the seat. This contributes to a more uniform velocity field in the diffuser entrance section, a higher velocity in the neck, and in maintenance of the required flow rate with the same or even a smaller seating diameter.