Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - VADEMECOM (VAlidation driven DEvelopment of Modern and Efficient COMbustion technologies)
Teaser
Combustion science will play a major role in the future quest for sustainable, secure and environmentally friendly energy sources. Two thirds of the world energy supply rely on combustion of fossil and alternative fuels today, and all scenarios forecast an increasing absolute...
Summary
Combustion science will play a major role in the future quest for sustainable, secure and environmentally friendly energy sources. Two thirds of the world energy supply rely on combustion of fossil and alternative fuels today, and all scenarios forecast an increasing absolute energy supply through combustion, with an increasing share of renewable sources. This implies that combustion will remain the major actor in transportation, power generation as well in food, cloth, sports and entertainment industries, and in important manufacturing processes like steel and glass making. Nevertheless, combustion science will need profound innovation to meet the future energy challenges. In particular, there is an urgent need for developing combustion technologies ensuring fuel flexibility, high energy efficiency and very low pollutant emissions, in the framework of a paradigm shift in energy systems towards more distributed energy production.
Given this background, the combustion community needs to face a grand-challenge in future years, namely the development of a validated, predictive, multi-scale modelling capability, to optimize the design and operation of evolving fuels in advanced technologies. While the use and value of turbulent combustion models continue to increase across combustion industries, current capabilities fall well short of what is needed in reliable design tools, especially when compared to the achievements in related fields such as solid mechanics
and fluid dynamics.
The objective of VADEMECOM is to drive the development of modern and efficient combustion technologies, by means of accurate and adaptive models, allowing a detailed description of the phenomena only where necessary. This is the key to transition from case-specific to generally applicable modelling approaches and to promote innovation in the energy sector. Indeed, combustion may appear as a mature technology, from the perspective of the old energy scenario. In today’s world, however, we must rethink the combustion field in the perspective of energy efficiency, fuel flexibility and environmental impact, to ensure future generations with affordable and sustainable energy and healthy environment.
Work performed
During the first 18 months of the action, significant progress has been made in the four technical areas of the project, namely the experimental investigation of novel combustion technologies, the assessment and optimisation of comprehensive chemical mechanisms for MILD combustion, the development of novel turbulent combustion models and the definition of strategies for the Validation and Uncertainty Quantification. The availability of additional human resources, with respect to the ones originally foreseen, allowed also to anticipate the beginning of the tasks foreseen in WP3 and WP4, form the second year to the first one. The major achievements during the first 18 months of the action can be summarised as follows:
WP1. Experiments on the ULB semi-industrial MILD furnace were carried out, with the objective of producing data that bridge the gap between the laboratory and the industrial scale. The investigation focused on the identification of the key features of such a combustion regime, and produced valuable validation experimental data (in-flame temperatures, flame chemiluminescence and chemical composition) for the validation of numerical simulation approaches (1 journal paper).
WP2. The predictivity of available chemical mechanisms for hydrogen, methane and their mixtures was assessed, at the conditions met in MILD combustion (relatively low temperature increase and high dilution). This has allowed to identify critical steps in existing schemes for their subsequent optimisation (1 submitted paper).
WP3. The previous work form the PI on the use of Principal Component Analysis has been extended, to develop reduced-order models for the simulation of lab-scale systems (3 journal papers). The approach can drastically reduce the cost associated to the resolution of chemical kinetics in Computational Fluid Dynamic (CFD) simulations, by finding and accounting only for the most energetic modes of the system. Moreover, new turbulent combustion closures for MILD combustion were developed and validated for a variety of fuels and systems, in the context of both Reynolds-Averaged Navier Stokes and Large Eddy Simulations (5 journal papers).
WP4. In the context of surrogate models, we have proposed a novel approach combining size reduction, via Principal Component Analysis, with advanced regression methods, to that allows to accurately predict the behaviors of combustion systems, characterized by high dimensionality, both in input and outputs. (2 journal papers).
Final results
We have made significant progress beyond the state of the art in several areas of the project:
- In the field of chemical kinetics, we have demonstrated the reduction potential of unsupervised learning methodologies such as Principal Component Analysis (PCA), using the state-of-the-arti comprehensive mechanisms available in the combustion community. This is a very relevant result considering the role of chemical kinetics in all modern combustion technologies and the current limitations in their use, due to their very large dimensionality.
- In the field of turbulent combustion modelling, we have proposed several turbulent combustion closures that allow to efficiently manage finite-rate chemistry and complex kinetic schemes. We have demonstrated the superior performances of these models with respect to the currently used ones, in the framework of novel combustion technologies, such as MILD combustion, where the interactions between chemical kinetics and turbulent mixing is of paramount important and sub-grid closure should account for that accurately. In particular, we have coupled combustion models based on the Partially-stirred reactor models with very accurate approaches for the estimation of the mixing and chemical time of the reacting species. The increase in model fidelity brought by this new development has been demonstrated on several reference systems in the combustion community.
- In the field of validation and uncertainty quantification, we have proposed novel approaches for the development of accurate surrogate models, that can be used for optimisation and uncertainty quantification with confidence and without the computational burden associated to full model. In particular, we have combined size reduction, via Principal Component Analysis, with advanced regression methods, to that allows to accurately predict the behaviours of combustion systems, characterised by high dimensionality, both in input and outputs.
In terms of perspectives, we maintain our overarching goal which consists in proposing a unified modelling approach that can predict the behaviour of advanced combustion technologies and be used, with confidence, in optimisation, new design and decision making. This implies:
- Demonstrating the feasibility of MILD combustion with a variety of fuels (hydrogen, ammonia, methane and their mixtures), by means of rigorous experimental investigation in systems bridging the scales between the laboratory and industrial installations.
- Developing optimised and validated comprehensive chemical mechanisms for MILD combustion conditions, for a variety of fuels (hydrogen, ammonia, methane and their mixtures), and develop strategies for their reduction and inclusion in large scale simulation.
- Developing models that can include realistic chemistry in the simulation of combustion systems, by means of a combination of approaches, including state-space parameterisation, mechanism reduction, machine learning, efficient chemistry management. While we have contributed to several of the areas mentioned above, we now face the challenge of bringing them together, and show the impact of such a unified approach on the simulation and prediction of practical combustion systems.
- Developing approaches to assess the confidence in the predictions from computational modelling, expanding our approaches for uncertainty quantification to realistic combustion systems.