Electricity has become an essential part of life in all spheres of modern society. In the home, electricity is used to power fans, air conditioners that provide a comfortable atmosphere, electricity is used to power the network of computer systems used comprehensively in commercial inventory organization, and in the computerized processes that govern manufacturing processes in the manufacturing industry.
Currently, a major part of power needs are met by steam turbines. With a huge amount of electrical power being generated by steam turbine generators, it is the need of the hour to make these power generation systems as efficient and as sustainable as possible. And one of the vital factors influencing the efficiency of these turbines is the design of turbine blades. It is the design and material of turbines blades that make a key role in determining the power output and emissions.
The type of material used for turbine blades is based on the stage of the turbine in which the blades will operate. There are three such stages: high-pressure (HP), intermediate pressure (IP), and low-pressure (LP), which are named according to the relative pressure of the steam in the stage.
Nowadays, titanium alloys have been used for a number of reasons. First, the density of titanium alloy is lower than steel which makes it possible to lengthen the LP blades and thereby increase turbine efficiency without increasing stresses in the blades due to centrifugal forces. Second, titanium alloys boast of higher corrosion resistance than steels; this makes titanium alloys perfect for use in LP stages where there are high levels of moisture. Eventually, titanium alloys are resistant enough to water droplet erosion that they can be used without erosion protection in certain applications.
If you discuss the design part with a turbine blades manufacturer, he will tell you that an efficient and reliable blade design must meet the following requirements.
1. The blade material must have enough yield strength to fight plastic deformation, and must be able to recollect such yield strength, or at least most of it, at high temperatures.
2. The blade material must be able to be processed and worked with ease.
3. Blade materials must display a moderate elastic modulus so that the blade neither deforms exceedingly nor breaks unexpectedly under normal operating stresses.
4. Preferably, blade materials must be of low-density in a bit to bring down the centrifugal forces, and therefore centrifugal strains, on the blades.
5. The blades should be corrosion-resistant, even in the presence of hostile ionic solutions formed by impurities in the steam.
6. Blades must be prepared in such a way as to diminish introduction of cracks during the manufacturing process.