New solutions for the future of aviation and a smooth energy transition
In future, hydrogen produced in a climate-friendly way will play a key role in power and heat generation, in industry and in aviation. Hydrogen is a very versatile energy carrier and can be used across all sectors. If it is produced sustainably, it offers the opportunity to massively reduce emissions, especially of the harmful greenhouse gas CO2, in the energy, transport and industrial sectors. The DLR Institute of Combustion Technology has been researching how hydrogen can be utilised safely and efficiently in stationary gas turbines for many years.
European gas turbine manufacturers have committed to offering gas turbines by 2030 that are capable of cleanly burning pure hydrogen and hydrogen mixtures, even under varying operating conditions. The use of hydrogen-capable gas turbines is a good complement to the use of wind and solar energy: the surplus energy from times with plenty of wind and sun could be stored in the form of hydrogen for later use.
Gas turbines are also well suited for quick start-ups and operation under changing load conditions, as they can react quickly to grid requirements. They are therefore ideally suited as backup power plants. However, a prerequisite for the expected increase in the use of hydrogen in gas turbines is the development of a hydrogen infrastructure.
In collaboration with Siemens Energy, the operating limits of hydrogen combustion were systematically explored in a series of tests on the high-pressure combustion chamber test bench in order to further develop the concept of jet-stabilised combustion for medium and large gas turbines. The time-lapse video from the OptiSysKom project shows the smooth transition from natural gas to hydrogen combustion at double speed. As soon as the hydrogen begins to be fed in, the natural gas is reduced at the same rate. At 0:45, this process is halfway complete.
Time-lapse video from the HBK-S high-pressure combustion chamber test bench - from natural gas to 100 % hydrogen
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Time-lapse video from the HBK-S high-pressure combustion chamber test bench - from natural gas to 100 % hydrogen
In collaboration with Siemens Energy, the operating limits of hydrogen combustion were systematically explored in a series of tests on the high-pressure combustion chamber test bench in order to further develop the concept of jet-stabilised combustion for medium and large gas turbines. The time-lapse video from the OptiSysKom project shows the smooth transition from natural gas to hydrogen combustion at double speed. As soon as the hydrogen begins to be fed in, the natural gas is reduced at the same rate. At 0:45, this process is halfway complete.
One way to create such an infrastructure relatively quickly is to set up decentralised supply networks. We are researching the use of hydrogen-capable micro gas turbines as part of such decentralised power plant concepts (link). The advantage here is not only the scalability of the systems, but also their load and fuel flexibility for the gradual conversion from natural gas to hydrogen operation. For hydrogen utilisation in micro gas turbines, as well as for use in large, central gas turbines, the Institute's departments carry out detailed investigations into combustion phenomena, which are then incorporated into burner development at the Institute and with industrial partners.
In addition to the development of hydrogen-capable gas turbines, the retrofitting of existing plants will play a central role in the transition from natural gas to hydrogen. Gas turbines used in industry and heat generation sometimes have a service life of more than 30 years - this applies in particular to plants in the medium power range. Retrofitting these plants enables the sustainable utilisation of existing systems and at the same time a quick entry into the use of hydrogen, as the effort, costs and duration of a retrofit are only a fraction of the cost of a new build. For this reason, the Institute is working together with gas turbine service providers on retrofit concepts for the conversion of existing power plants.
Direct combustion of hydrogen in aircraft engines
Hydrogen is characterised by its extremely high reactivity, especially under the conditions typical of jet engines. This is a hurdle for the use of hydrogen in aviation and the development of next-generation gas turbines, because the significantly greater reactivity increases the risk of flashback in comparison to conventional kerosene; in addition, the flame stabilisation mechanisms are significantly different to conventional liquid fuel.
The direct use of hydrogen as a fuel therefore requires new design approaches and manufacturing concepts. Burner design for future aviation applications requires detailed investigations into the differences between the combustion behaviour of hydrogen and conventional fuels. The aim is to fulfil the certification requirements in order to ensure safe operation. In future, propulsion systems that rely on the direct combustion of hydrogen could be used primarily in regional to medium-haul aircraft.
Fuels based on hydrogen and electricity (power-to-liquid, PtL, SAF)
Liquid synthetic fuels produced using hydrogen can be used wherever conventional drive systems cannot be easily replaced by batteries or fuel cells. Switching to these chemical energy sources would have the advantage that existing drive components and infrastructures would only have to be adapted slightly. We are investigating the chemical-physical properties of novel hydrogen-based fuels as well as their performance, composition and production routes.
For both ground-based gas turbines and aircraft turbines - as shown by previous work at the Institute - the further development of the proven FLOX concept with an adapted burner design is a promising solution in terms of flame stability, emissions and load flexibility.
