I am doing a bit of research on Brayton Cycle and find this T-S diagram for the cycle in https://www.grc.nasa.gov/www/k-12/airplane/brayton.html and have learned that the area encloses by the curve representes the heat going into the system. And I know entropy represetentes the amount of energy that can't do work. So is decreasing the area would make the gas turbine more efficient? How, on the graph, should the decrease make (lower the compressor exit temperature, raise the turbine entry temperature...)?
In the case of the Brayton cycle, the cold sink temperature is more or less fixed (ambient at 10,000 meters) so efficiency improvements require raising the temperature at which heat is added at constant pressure in the burner cans. This is the primary reason for the improvements in aircraft turbine efficiency which have occurred over the last 50 years: the development of turbine blade materials which can withstand higher and higher operating temperatures.