Uncertainties in multi-temperature nonequilibrium partition functions and application to CO2

International audienceInteraction and coupling terms in CO 2 Multi-temperature models Energy mode grouping a b s t r a c t Multi-temperature models are often used as a simplified way to describe nonequilibrium gases. These models assume Boltzmann distributions within each energy mode, which is useful for reducing the number of parameters in computations. This assumption requires that the energy modes are properly separated (which is valid, for instance, for vibration and rotation in low-lying rovibrational levels of diatomic molecules). For polyatomic molecules, several limitations arise. First, certain energy modes are often grouped together to further reduce the number of parameters, which requires additional hypotheses, and sometimes arbitrary grouping schemes. Moreover, the rovibrational levels of polyatomic molecules are often strongly coupled, and the assignment of the coupling terms to one or another energy mode is arbitrary. In this work, we present a method to quantify the influence of assignment or grouping schemes on nonequilibrium spectral models by comparing their impact on nonequilibrium partition functions, and we apply it to the CO 2 molecule. We show that significant differences arise when reducing the nonequilibrium model to two temperatures only, as often done in CFD or spectroscopy applications. In particular, one should carefully justify whether the vibrational bending mode is in equilibrium with the rotational mode or with the other vibrational modes. We then determine the nonequilibrium range where a simple Uncoupled Vibrating Rotor model is sufficient, where the coupling term assignment scheme becomes important, and where the uncertainty induced by the assignment of the coupling terms can no longer be neglected. This approach can be extended to other molecules

Investigations by Mid-IR QCLAS of pollutant emissions in High temperature exhaust gases released from plasma-assisted combustion

International audienc

Dynamic response of a weakly turbulent lean-premixed flame to nanosecond repetitively pulsed discharges

International audienc

Nonequilibrium in Thermal Plasmas with Applications to Diamond Synthesis

Atmospheric pressure plasmas are frequently considered to be in local thermodynamic equilibrium due to the high frequency of collisional processes which drive the plasma state towards a Maxwell-Boltzmann equilibrium. However, various forms of thermodynamic, ionizational, and chemical nonequilibrium have been demonstrated and investigated in atmospheric pressure plasma environments over the last several years, and the nonequilibrium behavior of such systems can be quite significant. The investigation, understanding, and exploitation of atmospheric pressure nonequilibrium plasma chemistry is necessary to the further expansion of plasma-based systems into mainstream manufacturing and processing applications. Several experimental programs to investigate the fundamental processes of atmospheric pressure nonequilibrium plasma chemistry, and the application of this nonequilibrium to various chemical systems have been undertaken in our laboratories. The results of these investigations have shed light on the kinetics behind various forms of atmospheric pressure nonequilibrium chemistry, and provided insights into the beneficial control of nonequilibrium plasma chemistry for processing applications

Ablation/radiation studies in the Ecole Centrale plasma torch facility

No abstract available

Ignition and development of flame kernel formed by nanosecond repetitively pulsed discharges in the quiescent lean premixed mixture

International audienc