The increased demand and limited supply of fossil fuels drives the search for alternative fuels for all modes of transportation and electrical power generation.
Also, we are witness to an increasing awareness of environmental issues and the human impact. In particular, air transport’s contribution to climate change represents 2% of human-created CO2 emissions. This is motivating active policies to make air transport greener and more sustainable: The International Air Transport Association (IATA) and the European Union have set targets for the reduction of 50% CO2 and 80% NOx emissions in 2050.
Hydrogen is a promising candidate for replacing fossil fuels in aviation. If produced from a regenerative source it is a carbon-free (green hydrogen). The direct emissions are free of carbon oxides and other contaminants; the only emissions are water vapour and oxides of nitrogen (NOx). Still, hydrogen combustion is promising in further reducing the NOx emission compared to conventional fuels. In addition, hydrogen’s high specific energy makes it an ideal candidate for aviation.
The use of hydrogen in combustors of gas turbines presents a number of technological challenges. The high reactivity of hydrogen may lead to flame auto-ignition, flashback, and other thermo-diffusive instabilities. Hence, novel fuel injection/mixing solutions are key towards the viability of burning hydrogen in gas turbines, making the most of the opportunities it provides (additional to the decarbonization): shorter combustion (smaller – cheaper- combustion chamber) and flatter traverse/cycle efficiency.
Combustion chambers need to be redesigned to meet the simultaneous requirements of hydrogen use (for GHG reduction/suppression), high combustion efficiency and flame stability, and with minimal nitric oxide emissions
The particular objectives of the first subproject, carried out at UPM are:
Development of RANS simulations of the complete combustion chamber capturing the coupled hydrodynamics and complex chemistry
Development of new high-fidelity models and simulation strategy for hydrogen combustion.
Identification and suppression of instability mechanisms during hydrogen combustion.
Identification of strategies and parameters for flame optimization regarding stability and thermal NOx generation.
The specific objectives of the second subproject, carried out at CMT-UPV, are:
Development and construction of novel test bench for hydrogen combustion studies.
Flow and flame characterization under relevant gas turbine operating conditions.
Creation of an experimental database for model validation.
MIXSHY proposes the use of the micromix combustion concept as a technology with high potential for this purpose. The concept is based on the use of multiple evenly spaced micro-nozzles through which hydrogen is injected forming small hydrogen jets that mix with the incident air perpendicular to the axis of the jet (crossflow configuration).
This leads to intense mixing and combustion through multiple small diffusion flames that significantly reduce the residence time of the reactants in the combustion zone, with the consequent reduction in NOx emissions. Another fundamental advantage of this type of combustion is the absence of flashback, this being a notable advantage from the point of view of the safety and integrity of the combustion equipment. A coordinated research plan is proposed, in which the research group at UPM focuses on the computational part, and the group at UPV on the experimental part.
MIXSHY aims at making contributions beyond the state-of-the-art in different scientific/technological aspects: burner concepts, dry-low-NOx hydrogen combustion, turbulence-combustion interactions, etc, which will boost hydrogen applications towards higher TRL. More understanding will be gained on the use of this fuel that will help build a scientific understanding of its applicability within the current context of hydrogen deployment.
MIXSHY plans the extensive study of micromixers by means of data-driven methods. This will help the digitalization of gas turbine engines, which is another major field of activity in the sector, and it will pave the path towards creating a digital twin of the experimental facility. The proposed burner concept can also be used in power generation systems, the other major field of gas turbine applications.
MIXSHY project will expand the experience of the project partners, who will integrate other activities into a holistic way, and help improve their competitiveness in the current research, development, and innovation context, where strong players are needed to meet EU demands of energy transition. It will foster the leadership of the group at international level.
MIXSHY activities will also be embedded in a scientific collaboration that the applicant groups already have with relevant scientific institutions. Contribution to education and training for high-skilled jobs in the aerospace sector. The European aeronautics industry plays an important role in employment. Currently this industry employs 435.000 directly and a further 800.000 indirectly through its supply chain which
includes a significant number of SMEs. The European aeronautics industry has a long-term goal not just to sustain existing market share but also to increase it. MIXSHY will take steps in securing the long-term high-quality employment in this industry. The physical insight gained and simulation and modelling tools to be developed will subsequently be transferred to industry.
