CoEC: Newsletter #1 released
6. April 2021
Read the first issue of the CoEC newsletter with updates about research, news about project partners and all things in between.
Fuel atomization and evaporation in practical applications
A Use Case by
Short description
Spray modelling for liquid fuels is another milestone to be covered for a successful engine simulation. Since the quality of atomization, evaporation and dispersion predictions directly affect the overall phenomena developing downstream, its proper modelling has a first-order impact on the whole results. In the context of LES and DNS, primary atomization can be described by deforming the mesh at the interface or by transporting Eulerian fields from which the interface is reconstructed a posteriori. After this process, the secondary atomization occurs in which the large droplets and ligaments are broken into small droplets. Although secondary atomization can be formulated in the frame of Eulerian transport equations, the size of the cells determines the minimum length that can be solved making attractive the use of the alternative Lagrangian approach. The behaviour of the droplets and their evolution have been object of an intense study over the years and, although a fruitful research has been carried out in this topic, much effort is still needed in order to develop comprehensive models for the primary atomization that can lead to physically accurate formulations for application to spray flames.
Objectives
It is considered a priority to contribute to the knowledge of liquid fuel injection and atomization due to its crucial influence on the combustion process and pollutants formation. This demonstrator includes the study of primary and secondary breakup, and the influence of heat conduction and droplet heating on the evaporation rates prior combustion takes place. The final objective will be the study of reacting sprays at relevant engine conditions.
Plasma assisted combustion
A Use Case by
Short description
Plasma-assisted combustion has recently gained renewed interest in the context of lean burning. Although lean combustion reduces the burn gas temperature and CO/CO2 content it leads, however, to less stable flames, and more difficult ignition. Short plasma discharges may counteract these effects, at a very low additional energy cost. In particular, Nanosecond Repetitively Pulse (NRP) plasma discharges have been proven to be efficient actuators to alter flame dynamics and facilitate flame stabilization while modifying the burning velocity. First studies on the impact of NRP discharges on combustion focused on kinetic mechanisms and gas heating processes. Different models have been developed in 0D, but no kinetic scheme for plasma-assisted combustion has been proposed so far. More recently 1D and 2D simulations have been conducted. Very few studies included a self-consistent simulation of the NRP discharge for combustion applications, although it was shown that thermal and chemical effects of the NRP discharge on ignition are of the same order. Because of their high computational cost, detailed simulations of 3D real cases have never been performed and only simplified formulations for the plasma effects have been used.
Objectives
The application of plasma in combustion simulations provides an unprecedented opportunity for combustion and emission control thanks to its capability to produce heat, active radical species and modify the transport properties of the mixture. This demonstrator is focused on the study of plasma-assisted combustion by Nanosecond Repetitively Pulsed (NRP) discharges in order to control the formation of combustion instabilities and pollutant formation.
Detailed chemistry DNS calculation of turbulent hydrogen and hydrogen-blends combustion
A Use Case by
Short description
A block of actions to decarbonize the EU is the use of low carbon content fuels, comprising natural gas and hydrogen blends. Regarding natural gas, its low carbon content leads to relatively low CO2 emissions while its higher resistance to knock compared to gasoline allows to achieve higher compression ratios and hence higher efficiencies. In spite of these benefits, such resilience may provoke a non-stable operation of the engine that can be avoided by the addition of hydrogen which expands the flammability region. The effects of hydrogen addition consist of the increase of the laminar flame speed and the induction of preferential diffusion which can result in thermo-diffusive instabilities. Although some works have analysed these phenomena, more effort has to be devoted. Finally, hydrogen blends and syngas, fuels with high hydrogen content (HHC), are other alternatives to reduce green house gas emissions that will also be investigated. Analogously, to natural gas blend with hydrogen, HHC fuels show thermo-diffusive instabilities which may lead to an unstable combustion process. Although some works have addressed these issues, there is still a lack of knowledge to be covered. In this context, LES and DNS come up as powerful techniques set in the context of HPC that can shed light in many open questions.
Objectives
The use case focusses on the study of thermo-diffusive instabilities in turbulent lean hydrogen flames and its effects on burning velocities, unstable combustion and noise. The effect of preferential diffusion will also be investigated due to its influence on equivalence ratio fluctuations and eventually on the local burning velocity. This work will be extended to syngas and high hydrogen content (HHC) fuels.
Prediction of pollutants and design of low-emission burners
A Use Case by
Short description
The harmful effects for human health of pollutants like NOx and CO have boosted their experimental and numerical study during the last years. However, their relatively long timescales have required to increase the level of complexity of turbulent combustion models in order to obtain accurate predictions as emphasized in Valera-Medina et al. 2019 and Karagöz et al. 2019. Moreover, the use of alternative hydrogen-based fuels, even reducing CO and other HC emissions (Cappelletti and Martelli, 2017) and increasing engine efficiency (Verhelst et al.,2009), may have dramatic effects on NOx emissions compared to conventional fuels. For these fuels three times higher amounts of NOx have been measured compared to gas natural in some operational conditions for gas turbines (Riccio et al. 2009) although some studies show that the combined use of ammonia and hydrogen have potential to reduce NOx production (Xiao and Valera-Medina, 2017). Finally, technologies with hydrogen burners need development as the mixing strategies have to be adjusted since H2 is much lighter than natural gas(Cappelletti and Martelli, 2017). Therefore, there is need to extend the knowledge about pollutant emissions not only for conventional fuels used in current engines but for hydrogen blends in order to produce innovative concepts.
Objectives
To optimize burner performance in terms of pollutant emissions making use of large-scale simulations. Advanced combustion and soot models will be used to pursue this objective. This use case will make tangible the potential of HPC as an important tool to increase reliability and accuracy in numerical simulations for practical applications with a strong industrial focus.
Technologies
CLIO, Alya, Nek5000, OpenFOAM, PRECISE_UNS
Use Case Owner
Barcelona Supercomputing Center (BSC)
Collaborating Institutions
BSC, RWTH, TUE, UCAM, TUD, ETHZ, AUTH
Prediction of soot formation in practical applications
A Use Case by
Short description
Soot formation is a complex phenomenon which requires the use of large chemical mechanisms not only to account for a detailed description of the small gas phase molecules but for the enormous variety of PAH. These expensive requirements have made its modelling elusive for the scientific community although acceptable results have been obtained in the last years (Yang et al. 2019, Rodrigues et al. 2018, Hoerlle and Pereira 2019). In order to increase the reliability of the simulations, a lot of work has to be done to improve PAH chemistry and their interaction with turbulence, soot modelling oxidation and simulation of particle size distribution. To sort out the difficulties that the soot solid phase introduces in the fluid mechanics simulations, the Method of Moments (MOM) (Mueller et al., 2009, Chong et al. 2019, Salenbauch et al. 2019) and the sectional model (Rodrigues et al. 2018, Hoerlle and Pereira 2019) have been used. Both methods have been coupled with flamelet combustion models providing stateof-the-art results (Rodrigues et al. 2018, Yang et al. 2019). Finally, another approach is the coupling of soot models with the Conditional Moment Closure (CMC) model for which promising results have also been obtained (Giusti et al. 2018).
Objectives
The objective of this use case is to demonstrate the predictive capabilities of Exascale simulations to provide accurate results of soot formation when applied to large-scale simulations. This ECD will narrow the gap between simulations and experiments obtaining state-of-the-art soot models and showing that satisfactory degrees of accuracy can be achieved for the prediction of an extremely complex process such as soot formation in engines.
Technologies
CLIO, OpenFOAM, PRECISE_UNS, Alya, Nek5000
Use Case Owner
Barcelona Supercomputing Center (BSC)
Collaborating Institutions
UCAM, TUD, TUE, AUTH, ETHZ
ETP4HPC handbook 2020 released
6. November 2020
The 2020 edition of the ETP4HPC Handbook of HPC projects is available. It offers a comprehensive overview over the European HPC landscape that currently consists of around 50 active projects and initiatives. Amongst these are the 14 Centres of Excellence and FocusCoE, that are also represented in this edition of the handbook.
CoEC is hiring: job opportunities for PhD students and postdocs
4. November 2020
Do you want to make a difference and contribute to combustion research that could transform Europe´s power and transportation sectors? CoEC is looking for PhD students and postdocs in Barcelona and Darmstadt.
New Centre of Excellence CoEC targets breakthroughs in combustion through Exascale computing
2. November 2020
The European Union is committed to achieving net-zero greenhouse gas emissions by 2050. To reach this goal, there is a need for coordinated research and innovation efforts to make low and zero-carbon solutions economically viable.
The recently launched Center of Excellence in Combustion (CoEC) addresses this challenge using advanced modelling and simulation technologies to study the combustion of sustainable fuels and new combustion technologies in order to transform Europe’s power and transportation sectors.
