Numerical study of flow irregularity in a new type control section of steam turbine high-pressure module

In order to improve the flow part of the control system and enhance energy performance, A. Podgorny Institute of Mechanical Engineering Problems NAS of Ukraine has developed a three-stage control system section of the K-325-23.5 steam turbine high-pressure module (HP), that has no equalization chamber. To determine the effectiveness of the control section’s gas-dynamic improvement, the problem of the turbulent flow spatial structure studying was stated. For this, a numerical simulation of the steam flow was carried out in the rated mode, taking into account the partiality of the supply. The main task of the numerical simulation was to identify the magnitude of circumferential irregularity of gas-dynamic parameters in the first stages of the section and at the outlet. Spatial calculations of the steam flow in the studied flow parts were carried out using the IPMFlow software package for the spatial turbulent flow modeling in turbomachines developed at Institute of Mechanical Engineering Problems NAS of Ukraine. The study of the steam flow circular irregularity for modes with mass flow rates of 100%, 70% and 50% was carried out. The 70% and 50% modes are characterized by two closed control valves out of four, which corresponds to 37% of open blade channels. The results and analysis of the three modes calculations are presented in the form of distributions of mass flow rates and pressures in the stage gaps and at the section outlet. The graphs clearly show that the irregularity of the specific flow rate remains until the last stage, meanwhile the pressure irregularity is insignificant for all the considered modes. An analysis of the simulation results shows a rather slight irregularity of the steam parameters at the outlet of the control section in the partial modes and insignificant irregularity in the design mode. Based on the results of the analysis, a conclusion about the effectiveness of the new control section use for the steam turbine K-325-23.5 modernization was made. To implement the new control section, it is reasonable to study the level of unsteady loads on the HP blades further