Question

The efficiency of the Brayton cycle increases with an increase in the pressure ratio across the compressor. What limits our use of this tactic to increase cycle efficiency? What trade-offs have to be made?

plase typr the answer no hand writing

Answer 1

Actual gas turbine cycle works between two temperature limits one is maximum temperature that depends upon the metallurgical condition of turbine blades and second the minimum temperature that normally depends on atmospheric condition.

When pressure ratio is equal to 1 both efficiency and work net will be zero as pressure ratio increases both start increasing and efficiency becomes maximum when the compression process ends at maximum temperature limit, at this point efficiency becomes equal to carnot efficiency but net work output again become zero.

To get better efficiency and maximum work output the brayton cycle works at the optimum value of pressure ratio and its value is square root of maximum pressure ratio.

The shaded area shows the working range of Brayton cycle in which we can get optimum efficiency and work.