Keywords: Erosion,
turbines, pipes
1. Introduction
A multidisciplinary
field concerned with the generation and application of knowledge relating to
the composition, structure, and processing of materials to their properties and
uses. This field needed the complete knowledge of material behavior. It forms a
bridge of knowledge from the basic sciences to various engineering disciplines.
The study of metallic
materials constitutes a major division of the materials science and engineering
field. Most metals have a crystalline structure of closely packed atoms
arranged in an orderly manner. In general they are good electrical and thermal
conductors. Many are relatively strong at room temperature and retain good
strength at elevated temperatures. Metals and alloys are often cast into the
nearly final shape in which they will be used as different parts of fluid
machinery. Ferrous metals and alloys contain iron as their major metallic
element; nonferrous metals and alloys contain elements other than iron as their
major metallic element.
Erosion is
described as the progressive loss of original material from a solid surface due
to mechanical Interaction between the surface and a fluid which may be a
multi-component fluid or impinging solid or liquid Particles. Corrosion is a material
degradation process which occurs due to chemical or electrochemical action,
while erosion is a mechanical wear process.[1] But my study is based
upon the only erosion. The erosion rate of blades is 10 times greater than the
erosion wear of hub. The erosion rate is found to be more severe near the
leading edge as compared to other parts of impeller. The simulations which were
carried out on impeller show that particle size affects the erosion rate only
up to certain size of particles and depends on the impact angle. Slurry is a
mixture of solids and liquids. Its physical characteristics are dependent on
many factors such as size and distribution of particles, concentration of
solids in the liquid phase, size of the conduit, level of turbulence,
temperature, and absolute (or dynamic) viscosity of the carrier. Microstructure
investigation was carried out in order to reveal the nature of damage of the
specimen under various test conditions using a scanning electron microscope. Although
several factors influence the formation of deposits on turbine components, the
general effect is the same no matter what the cause. Adherent deposits form in
the water passage, distorting the original shape of turbine nozzles and blades.
These deposits often rough or uneven which are at the surface increase
resistance to the flow of steam. Distortion of water passages alters water
velocities and pressure drops, reducing the capacity and efficiency of the
turbine. Where conditions are severe, deposits can cause excessive rotor
thrust. Uneven deposition can unbalance the turbine rotor, causing vibration
problems.
