A NEW CONCEPT FOR IMPROVING THE EFFICIENCY OF GAS TURBINES FOR POWER PLANT OPERATION

A method for enhancing the efficiency and power output of gas turbines is presented here. The concept relies on increasing the machine's pressure ratio without modification to the existing baseline Brayton cycle by adding independent topping gas generators in parallel. The mass flow through the compressors of the topping gas generators is higher than the baseline cycle. This additional mass flow is bled off from the topping compressors to do work through an external air expander. The conditions in the baseline cycle turbine remain unaffected. These topping gas generators are envisioned as being installed in place of the existing combustor(s), acting as high-pressure compressor and turbine, with the original GT compressor and turbine acting as their low-pressure counterparts. The air mass flow after the low-pressure compressor is divided into several parallel partial flows, which are fed to the gas generators. The gas generators consist of a compressor (in most cases a 1-stage centrifugal compressor will suffice), combustion chamber and turbine. They are, as a matter of fact, dimensionally small high-speed gas turbines that are free-running, like turbochargers or like the HP-section of aero engines. The concept can be applied to both new gas turbine designs and retrofits, resulting in increased power output and thermal efficiency. The paper describes the concept and presents sample calculations with various gas turbine types, indicating the possible achievable benefits under various assumptions.