Provided that it is produced from renewable sources, hydrogen is an energy carrier that exhibits distinct advantages when compared to fossil fuels, such as a higher heat release per unit mass and a wider range of burning equivalence ratios. Decreasing the minimum value of hydrogen concentration leading to burner-stabilised flames is crucial to enabling the viability of this fuel as a substitute for hydrocarbons. Lean combustion of hydrogen mixtures is thus the key to unlock the potential use of this energy carrier as fuel for practical applications, thus enabling the advent of sustainable communities.
Fuel-oxidizer mixtures with low hydrogen content, when burned in ultra-lean conditions (high air-to-fuel ratio), exhibit intrinsic thermo-diffusive instability due to their low heat-to-mass diffusivity ratio (Lewis number). This means that heat diffuses significantly slower than the fuel, disrupting the flame front and leading to unsteady combustion. This unstable burning leads to a fluctuating heat release rate that, in turn, can couple with the acoustic modes of the burners, thus triggering thermo-acoustic instability. These combustion instabilities limit the operation range of practical combustion devices, since they may lead to destructive damages.
The goal of this internship is to conduct a preliminary investigation of the use of heterogeneous catalysis using low-cost materials to control these (intrinsic and thermo-acoustic) combustion instabilities and, thus, to significantly reduce the minimum equivalence ratio leading to flame stabilization.
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CDD Technicien-ne électronicien-ne - 12 Mois - Catégorie B
POST-DOC (M/F) - Control by Machine Learning of bluff body wakes
At the CNRS-Laboratory PPRIME, based at the Futuroscope, this post-doctorate position is part of the French ANR COWAVE program between the laboratories PRISME in Orleans, Pprime in Poitiers, LHEEA in Nantes and the PSA automotive industry. This Post-Doc position concerns the Pprime contribution to the COWAVE project which aims the experimental exploration of closed-loop wake control strategies with mobile flaps in a water tunnel facility. Three-dimensional bluff-body wakes generate pressure drag and side forces and thus contribute significantly to the fuel consumption and pollutant emission of road vehicles. Despite this crucial impact and the numerous attempts to reduce harmful environmental effect of bluff body wakes by flow control it is still unclear what is the most efficient control strategy! In this context, the ANR project COWAVE addresses two fundamental aspects of wake control: - First, what kind of actuators are most efficient? While most closed-loop control strategies use viscous entrainment effects to actuate the shear layers in the wake, the exploitation of pressure forces produced by mobile deflectors could be an interesting alternative to be tested. - Second, for the implementation of closed-loop control, we want to test if control strategies obtained by machine learning techniques allow to obtain better efficiency and robustness than the more classical model-based approaches? The proposed Post-Doc position is part of the French ANR COWAVE program between the laboratories PRISME in Orleans, Pprime in Poitiers, LHEEA in Nantes and the PSA automotive industry. This Post-Doc position concerns the Pprime contribution to the COWAVE project which aims the experimental exploration of closed-loop wake control strategies with mobile flaps in a water tunnel facility. APPLY Follow link / Application Deadline : 12 March 2021 https://bit.ly/3qDG6Ml