Investigation of Hydrogen CombustionCopyright: © KHI
To implement the international climate targets, the further expansion of renewable energy sources is necessary. Due to difficult forecasting and natural fluctuations in solar and wind occurrence, fluctuations in generated power increase as renewables are expanded. These local and temporary over- and undersupplies must be balanced to ensure the security of supply. This requires controllable system components that can be switched on or off as needed. Gas turbines are suitable as dispatchable and flexible components in a regenerative-dominated energy supply system due to their short start-up times, high load gradients and a wide operating range.
Hydrogen is an ideal CO2-free gas turbine fuel, as it can be produced regeneratively via electrolysis, for example. However, the combustion characteristics of a hydrogen flame are very different from those of a natural gas flame. In particular, the laminar flame speed and the adiabatic, stoichiometric flame temperature of a hydrogen flame are significantly greater. Conventional DLE (dry low emission) combustors, which are designed to use natural gas, therefore cannot be operated with fuel mixtures containing a high proportion of hydrogen. A high-pressure combustor test rig has been set up at the Institute of Power Plant Technology, Steam and Gas Turbines to investigate novel fuel-flexible combustion concepts for gas turbine combustors.
The test rig enables investigations on can-type combustion chambers of industrial gas turbines under real operating conditions. Combustion chambers with a maximum thermal output of up to 10 MW and an exhaust gas temperature of up to 1350°C can be tested. The air supply is capable of providing an air mass flow of up to 12 kg/s at maximum 24 bar and 550°C. The fuel supply has access to hydrogen and natural gas. In addition, the fuel composition can be varied continuously between 100 % natural gas and 100 % hydrogen via a blending system.
The aim of the various investigations is the influence of the fuel composition on the nitrogen oxide emissions and the flame stability of the combustion chamber in particular. The test rig offers the possibility to use reduction strategies for nitrogen oxides, such as water injection. The air supply is ensured by a six-stage geared radial compressor. The first four stages of this compressor are intercooled, which on the one hand improves the efficiency and on the other hand ensures a constant outlet temperature of the air. The air is then heated to the desired temperature level by a separate air preheater. An injection cooler (quench cooler) is installed behind the combustion chamber to cool down the exhaust gas before it is fed into the chimney through a backpressure valve. This makes it possible to adjust the temperature, pressure and mass flow in the combustion chamber independently of each other over a wide range.