Mechanical Engineering - Thermodynamics - Discussion

Nothing understood. Post the explanations clearly.

Rankine cycle used in thermal power plants deals on heating up water in constant pressure while changing its phase. The process will has greater thermal efficiency compared to any other cycles. Otto cycle can't be used because heat supplied to the system is in constant volume process, not allowing steam to expand properly.

If Otto cycle forced to used, the pressure will be too high for any material (vessel) to withstand. Diesel also can't be used, because while heat supplied to the system, the fluid deliver work to the surrounding. This not applicable because the work should be extracted by steam turbine.

But my question is that turbine is used to rotate the generator for generating the electricity & its rotate with the help of steam pressure. Then how we can calculate its efficiency & work ratio. But still we assure that the 70% of power from turbine is used to run the compressor itself. So it's correct but, how we can say its very low. Please suggest answer.

I think that, since the specific volume (reciprocal of density) of air is high, the compression of air requires more work.

Hence, the major fraction of the work developed by the turbine is utilized in driving the compressor.

Therefore, the efficiency of the simple gas turbine plant is too low.

The fuel consumption should be more in this.

Since efficiency is a function of pressure ratio in simple gas turbine (braton, joule) cycle.

Because, efficiency = 1- (heat reject / heat supply) in case of simple gas turbine.

Work ratio is just the fraction or percentage of the work that the turbine produces that is consumed by the pump.

Half and more the power produced by the turbine is used to complete motion in the compressor.

Maximum power turbine is consumed by compressor itself and also air is working Media so max Power loss.