Study on Characteristics of Convergent versus Convergent-Divergent Nozzle of Steam Turbine with Circular and Square Cross Sections

The research objective is to determine which format, circular or square cross-section, is better for the convergent and convergent-divergent nozzles used in a double-row single-stage steam turbine. In this paper, it will carry out the simulation process using ANSYS and analyze several types of nozzles with different dimensions that have either circular or square cross-sections. The study was conducted for steam turbines of 800 kW and 1200 kW. Models for both types of nozzles were built based on dimensions and engineering data obtained from the palm oil industry, catalogues, and field surveys. The study will observe the characteristics of each test model by simulating the distribution of velocity, pressure, and temperature. The result of the simulation indicates that the largest outlet steam velocity is at a converging-divergent nozzle with a circular cross section of 1200 kW, where the steam coming out of the nozzle is 890.3 m/s. The smallest steam velocity of 652.3 m/s occurs when steam exits from a square nozzle with a power rating of 800 kW. The simulation of steam pressure shows that the largest is at 800 kW for the square-section nozzle with 7.73 bar. The smallest steam pressure is on the 1200 kW steam turbine, which implemented a converging-divergent circular nozzle with 2.69 bar. The highest steam temperature at 800 kW for the steam turbine, which implemented a square-section nozzle, was 181.69°C. The smallest is on a 1200 kW steam turbine, which implemented a converging-divergent circular nozzle, namely 108.34°C.