Thermal efficiency measures the process of converting chemical energy of the fuel into energy available for propulsion Function of overall pressure ratio and component efficiencies Current engines at 40: 1 overall pressure ratIo Future engines at 60: 1 overall pressure ratioThermal efficiency measures the process of converting chemical energy of the fuel into energy available for propulsion - Function of overall pressure ratio and component efficiencies - h s Current engines at 40:1 overall pressure ratio Future engines at 60:1 overall pressure ratio