Question

Investigate the 'turbine blade (for jet engine) making process'

Hint: Turbine blade is made of superalloy. Recently, it shows the single crystalline structure.

Format: Format is the same with previous homework. A4 up to 4-5 page. Photo and figures are welcome. References should be written.

Answer 1

Turbine blade (for jet engine)making process

Turbine blade is an important part of a jet engine.The turbine blades are usually made of stainless steel,titanium,nickel alloys and ceramic materials.The number of turbine blades is going to vary depending on the manufacture,the size of engine,and technology advancement.

Turbine blades are made by a different method than that used to form compressor blades.because they are subjected to even greater stress due to the intense heat of the combustor that lies just infront of them.The steps of making process are,

# Copies of the blades are formed by pouring wax into metal molds.

# When wax shapes has set it is removed from the mould and immersed in a ceramic slurry bath.It forming a ceramic coating of 0.25 inch thick.ie 0.63 centimeter.

# Each cluster is then heated to harden the ceramic and melt the wax.

# Molten metal is poured into the hollow left by the melted wax.

# Internal air cooling passages within each blade are also formed during this stage.

# The metal grains in the blade are now aligned parallel to the blade by the process of directional solidifying.The grain direction is very important because turbine blades are subjected to somuch stress,also if the grains are aligned correctly the chances of fracturing of blades are also less.

# The solidifying process is takesplace in computer-controlled ovens in which the blades are carefully heated according to precise directions.

# After the removal from the oven there is cooling process.It can be classified into two major sections.

a-The internal:-In it the heat is removed by a variation of convection and impingement cooling configurations,where high velocity air flows and hits the inner surface of the turbine vanes and blades.

b-The external:-In external blade cooling cold air is injected through the film cooling holes on the external blade surface inorder to create a thin film cooling layer.

# The final stages in preparing turbine blades are machine shaping and either laser drilling or spark erosion.

# The blade is first honed to the final desired shape through a machining process.Then parallel lines of tiny holes are formed in each blade.It is used as a supplement to the interior cooling passageways.The holes are formed by either a small laser beam or by spark erosion,in which carefully controlled sparks are permitted to heat holes in the blades.