Steam Turbines convert pressure energy (more specifically Heat Energy) into useful mechanical work. The mechanical work thus generated can be used either to drive equipment such as Pumps, Blowers, Fans etc. or to further generate electrical power. The amount of work converted depends on the difference in Inlet and Exhaust Enthalpy / Heat Content of the Steam and the Quantify of steam flowing through the Steam Turbine. Hence the work output from a Steam Turbine can be either increased by increasing the Enthalpy Drop or the Quantity of Steam Flow. Single Stage Steam Turbines as used where the Enthalpy Drop is reasonably low. If the high enthalpy drop needs to be achieved, Multistage Steam Turbines are used. The Amount of Enthalpy that can be dropped in a stage is limited by the diameter of the turbine wheel and the speed of the Steam Turbine. Theoretically, a Single Stage Steam Turbine can drop any amount of Enthalpy of we can increase the turbine speed and the turbine wheel diameter. Owing to the cost and design constraints, it is not possible to increase either the Steam Turbine wheel diameter or the turbine speed beyond a value. The Multistage Steam Turbine was thus invented to drop a large amount of enthalpy in a practical way to achieve maximum possible power generation from any given quality of steam flow. https://turtleturbines.com/multistage-steam-turbines/
