Power Augmentation of Gas Turbines using Water or Steam Injection

A typical technology of power and emissions control in industry uses water or steam injection into the combustion chamber of a gas turbine. Significant advantages of this method are a positive influence on the flame temperature as well as reduced emissions. Applied examples of this technology are the STIG (STeam Injected Gas turbine) cycle, the HAT (Humidified Air Turbine) cycle and the Cheng cycle.

Advantages of water or steam injection

Addition of water to a fuel-air mixture increases the heat capacity of the overall mixture. Therefore the overall temperature level is reduced significantly when using the same amount of fuel. The resulting lower peak temperatures influence the gas turbine process in various ways. First of all the lifetime of the gas turbine engine can be increases as thermo-mechanical stresses are reduced. In addition the volume flow through the turbine is increased which also results in a higher power output of the turbine. Consequently the electrical energy produced by the generator is increased, too. Furthermore NOx and CO emissions can be clearly reduced using this technique.

Characterization of humid combustion

In context of the Energy Valley Bavaria project, a detailed investigation of humid combustion will be conducted. The aim of this project is to improve the basic understanding of the processes occurring during the combustion of natural gas with humidified air.

Therefore experimental research is conducted on a premixed methane-fired swirl-burner test rig. The influence of various ways of water and steam injection into the combustion chamber on the flame structure and behavior is investigated. Therefore velocity fields, temperature fields and heat release distributions of dry and humid flames are compared. These various distributions are obtained using optical diagnostic methods like PIV-measurements, OH-LIF measurements and the measurement of OH*-chemiluminescence. It is desired to gain a fundamental understanding of the processes during the combustion with water or steam addition.