Question

The process of draining steam from the turbine, at certain points during its expansion and using this steam for heating the feed water is known as .

• A. Bleeding
• B. Cooling
• C. Compounding
• D. Governing

Hint:

Think of the turbine as a pipe carrying energy. "Bleeding" is like making a small prick in the pipe to let a little energy out early to warm up the incoming water. It sounds wasteful, but it actually saves a lot of fuel in the long run!

Answer 1

The Correct Option is A

In modern steam power plants operating on the Rankine cycle, regenerative feed water heating is employed to significantly improve the overall thermal efficiency of the plant. 1. The Process of Bleeding:

Bleeding (also known as steam extraction) involves withdrawing a small percentage of steam from the turbine at intermediate stages before it has completed its full expansion.

• Instead of allowing this steam to expand all the way to the condenser pressure, it is directed to a "feed water heater."

• In the heater, the extracted steam condenses and transfers its latent heat to the high-pressure feed water coming from the pump.

2. Why Bleeding Increases Efficiency: The primary goal of bleeding is to increase the average temperature of heat addition to the cycle.

• By pre-heating the water before it enters the boiler, the boiler has to do less "sensible heating" (heating the water to its boiling point).

• This reduces the external heat input required from the fuel while the reduction in turbine work output (due to the extracted steam) is relatively small.

3. Comparison with Other Terms:

• Compounding: Using multiple stages to reduce the high rotational speed of the turbine.

• Governing: The method of controlling the turbine speed and output power to match the load on the generator.

• Cooling: The general removal of heat, which is not the specific term for this regenerative process.