Some Factors in the Use of High Temperatures in Gas Turbines

A comparison is made between gas-turbine cycles with inlet temperatures of 1,250 and 2,200 deg. F. The use of high inlet temperatures necessitates cooling; the effect of air and water cooling in turbines is examined, and equations are given and used to show the factors controlling cooling loss. A cooling-loss factor is also derived which gives the turbine efficiency obtainable with various degrees of cooling. A cycle with an inlet temperature of 2,200 deg. F. is examined to show the effect of air or water cooling. With water cooling the steam generated is then considered either to provide an increase in useful power or to pre-cool the inlet air. For greater efficiency the steam should be used to increase the power delivered. Practical considerations and a proposed marine layout are given, together with a series of conclusions. Appendices are also included giving the assumptions made and derivations of the equations.