Anyone who wants to operate gas turbines or large engines with hydrogen or hydrogen blends needs to know how the materials used respond to the combination of high temperatures, mechanical loads, and hydrogen contact. Fraunhofer Institute for Mechanics of Materials IWM has validated a testing procedure using hollow specimens, which can vary these three stress factors independently of one another. This issue is highly relevant, as an increasing share of hydrogen is to be burned in gas-fired power plants in order to gradually make them climate-neutral.
Hollow specimen delivers meaningful results regarding material fatigue
The central challenge: Conventional hydrogen pressure chambers cannot be combined with the high and fluctuating operating temperatures encountered in turbines and engines. The researchers in Freiburg therefore rely on hollow specimens with an internal bore. Hydrogen flows through this bore while the specimen is subjected to thermomechanical loading from the outside. In this way, hydrogen pressure, temperature changes, and tensile and compressive load cycles can be adjusted separately, allowing various operating scenarios to be simulated.
In ongoing experiments within publicly funded projects, Fraunhofer IWM has reported that hollow specimens deliver meaningful results both at constant temperatures and at varying temperatures. The data obtained on stress, strain, and service life provide a basis for decisions regarding material selection and component design. Hydrogen-related reductions in service life can thus be evaluated depending on the pressure. These relationships are incorporated into material models, which are used in component simulations.
New testing method could make turbines for hydrogen power plants more economical
Up to now, the insufficiently quantified influence of hydrogen on material fatigue has, according to Fraunhofer IWM, led to higher safety margins in component design, the use of more expensive materials, or elaborate component tests. The new method aims to reduce these costs. Demand for such testing is expected to increase: gas turbines are increasingly needed as flexible backup power plants, and many manufacturers are working to qualify their machines for operation with rising hydrogen shares.
