Difference between Velocity Compounding Turbine and Pressure Compounding Turbine

Velocity compounding pressure compounding
🔗What is meant by compounding of turbine? What are the advantages of compounding?
🔗Velocity compounding - working with pressure velocity curve
🔗Pressure compounding working, advantages and disadvantages

Comparison between velocity compounding and pressure compounding

Velocity Compounding turbine
Pressure compounding turbine
Velocity/ Kinetic energy of steam is converted to useful work in more than one stage.

Pressure energy of steam at turbine input gradually extracted in multiple steps
Pressure of steam remains constant in every fixed blade and moving blades except in the first nozzle.

Pressure of steam decrease in every nozzle (fixed blades)
Velocity of steam increase in the first nozzle. Steam velocity decreases in every moving blade, and remain constant in every fixed blade (there will be some frictional losses)
Velocity of steam increase in every nozzle (fixed blade). Steam velocity decrease in every moving blade
High velocity of steam inside the turbine.
Velocity of steam is low when compared to velocity compound turbine.

High frictional losses
Low frictional losses

Fewer number stages, and hence the turbine length is short, require less space
Large number of stages and it is bulky, require more space.

It gives maximum output at the first stage, work produced in the low-pressure stages is much less.

Same amount of work produced in each stage.
Less efficient
More efficient

High steam consumption
Less steam consumption when compared to velocity compounding.

Ratio of blade velocity to steam velocity is not constant (not optimum for all blades)
Ratio of blade velocity to steam velocity is constant.

Steam pressure inside the turbine is literally equal to the atmospheric pressure so there will be no problem of steam leakage.
High pressure of steam inside the turbine. The chance of steam leakage will be more when compared to velocity compounded turbine.

The casing of the turbine need not be airtight.

Turbine casing should be airtight.



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