What type of turbine uses the principle of steam expansion for work output?

An impulse turbine operates on the principle of steam expansion, where high-pressure steam is directed through nozzles to produce a jet that strikes the turbine blades. This action converts the kinetic energy of the steam into mechanical energy, causing the turbine blades to rotate. The key aspect of an impulse turbine is that the steam expands in the nozzle and then does work directly on the blades, resulting in a difference in momentum that drives the turbine.

The other types of turbines operate on different principles. A reaction turbine, for instance, utilizes both the pressure and the velocity of the steam expanding through the turbine blades, allowing for a continuous interaction between the steam and the blades as the steam expands within the machine. This is distinct from the impulse principle where the work is done primarily by the momentum of the steam jets. The combined cycle turbine is typically a system that integrates both gas and steam turbines for improved overall efficiency but does not specifically focus on steam expansion alone as a method of work output. A gas turbine, on the other hand, relies on the combustion of gas to produce high-speed exhaust gases to perform work, making it also fundamentally different from the steam expansion mechanism of an impulse turbine.

Thus, the correct identification of an impulse turbine showcases its unique function in utilizing