Higher, Faster, Stronger -Recent trends in Steam Turbines

Ever since their invention and successful use as power generators in power plants, there has been a tremendous effort by many engineers, scientists, companies and research institutes in the field of steam turbines. Steam turbines did not work as efficiently as they do now, when they were invented. From the parson’s turbine to the impulse reaction turbine, the advancements have been propelled by thorough research and a hawk’s eye for inefficient performance. Steam turbine research has remained a hot area of research mainly because of the results that even a slight increase in efficiency could deliver. More than 80 % of the world’s energy sources are derived from the use of steam turbines in nuclear and thermal power plants. The importance of steam turbines and research in improving their efficiency and improvising on their design aspects need not be stressed any further.

How Can A Steam Turbine Be Improved?

A steam turbine has thousands of miniature components. From the gigantic blades that drive the rotor, to the bearings and nuts that keep the machine in place, the steam turbine has tremendous scope for improvement and effective design of every part plays a significant role in improving the turbine’s overall efficiency. Some of the areas where a lot of research goes into are those such as nozzle design, aerodynamic blade design, lubrication engineering, heat transfer mechanisms, part cooling, fabrication and part machining, pipe flow mechanisms, metallurgy etc.

Design of steam turbine machine parts such as nozzles and blades to make them aerodynamic using computational fluid dynamics has gained a lot of steam as a field in itself! A small advancement in the blade design could help in increasing efficiency tremendously. Blade design with Computational Fluid Dynamics or CFD focuses on reducing the local profile oriented loss on a Quasi 3 Dimensional (Q3D) basis. The design of proper inlet ducts from the turbines based on their operating time, economic considerations, size of the network and size of the turbine is also equally important. In this case, since the flow is highly unsteady and complex, the effects and degree of non uniformity in the flow has to be controlled to a large extent or predicted and taken care of suitably. Choosing proper materials for the different steam turbine components and parts is also an important aspect of design. The use of different lightweight yet strong and thermally resistant alloys to make steam turbine blades and moving parts is of very high importance. This also brings about the issue that the material should be as free from erosion as possible and should not succumb to rust and other chemical changes while under operation. Technologies such as anti erosion blade shields bear testimony to this.

Some of the world’s largest turbines manufacturing companies that are seeing the rewards of research and steam turbine advances are coming together to develop highly efficient turbines. The collaboration of Mitsubishi Heavy Machinery and General Electric Energy (GE Energy) for the conceptualization and design of a highly efficient “next- generation” steam turbine for its inception in combined cycle gas turbine power plants recently has further proved that there is still a lot to be achieved in steam turbine related research and development, and that the scope for improvement can be much higher.