Session: 04-05 High hydrogen I

Paper Number: 152427

Investigation of Critical Operating Conditions for Hydrogen Flames Under Typical Gas Turbine Conditions 

This paper reports on the demonstration of reliable operation of the core component of a modern jet-stabilized burner for large high-efficiency gas turbines with high power density and wide operating range in pressurized operation with 100 % hydrogen.

Innovative gas turbines are crucial for the energy transition as they can react flexibly to fluctuating renewable energy sources and optimize complex energy systems. The use of hydrogen is essential for a CO₂-free power supply. Jet-stabilized burner concepts are ideal for this - in contrast to conventional swirl burners, they are characterized by excellent flexibility and low pollutant emissions.

The presented work aims to develop a combustion system that enables the use of hydrogen and fuel mixtures with a high hydrogen content and to further optimize the combustor components.

In the HBK-S high-pressure combustor test rig at the DLR Institute of Combustion Technology, high-pressure tests were carried out mainly with hydrogen, but also with various hydrogen-natural gas mixtures, in order to investigate the critical operating conditions for hydrogen flames under conditions typical of gas turbines. A special optically accessible test rig with a single nozzle, representative of modern jet-stabilized gas turbine combustion systems, was used for this purpose.

The main investigations focused on operation at high pressures, high preheating temperatures and high flame temperatures, even beyond the specifications of state-of-the-art gas turbines, and addressed the high reactivity of hydrogen. The primary influencing variables such as pressure, inlet temperature and jet velocity were systematically varied, accompanied by optical and laser-based combustion diagnostics.

The feasibility of operation with hydrogen and hydrogen-natural gas mixtures was demonstrated.

The test series on flashbacks yielded several new findings. For example, a strong dependence on the respective pressure ratios was identified, with no flashbacks at very low pressure in the investigated flame temperature range and an asymptotic behavior of the operating limit at high combustion chamber pressures. Higher jet velocities have a positive effect on the stable adiabatic flame temperatures that can be achieved. Flame flashbacks could be directly observed and investigated with the aid of an optical mixing tube. It was found that they only last a few milliseconds and always occur close to the wall during the experiments.  A flashback through the center of the mixing tube was not observed, nor was self-ignition. The flashbacks were preceded by the lighting up of the exit edges of the optical mixing tube into the combustion chamber. The discussion with experts shows that further detailed investigations are necessary to understand this phenomenon. It is assumed that one possible explanation for this is the slower heating of the material of the mixing tube before the flashback. Further work will follow.

Presenting Author: Holger Ax German Aerospace Center (DLR)

Presenting Author Biography: tbd

Authors:

Holger Ax German Aerospace Center (DLR)
Oliver Lammel German Aerospace Center (DLR)
Rainer Lückerath German Aerospace Center (DLR)
Joshua Gray German Aerospace Center (DLR)
Benjamin Witzel Siemens Energy
Lutz Blätte Siemens Energy
Berthold Köstlin Siemens Energy