No abstract

Studies of the hyperfine anomaly has found a renewed interest with the recent development of techniques to study the properties of long chains of unstable nuclei. By using the hyperfine structure for determining the nuclear magnetic dipole moments, the hyperfine anomaly puts a limit to the accuracy. In this paper, the differential Breit–Rosenthal effect is calculated for the 6s6p3P1,2 states in 199Hg as a function of the change in nuclear radii, using the MCDHF code, GRASP2018. The differential Breit–Rosenthal effect was found to be of the order of 0.1%fm−2, in most cases much less than the Bohr-Weisskopf effect. The results also indicate that large calculations might not be necessary, with the present accuracy of the experimental values for the hyperfine anomaly.

An increasing amount of recent experimental evidence indicates that sequential combustion is particularly well-suited for burning highly-reactive fuels like hydrogen, while maintaining low emissions. A convenient feature of the sequential combustion system, resulting in a fundamental advantage compared to alternative approaches, is the possibility of controlling the second-stage flame position through its combustion characteristics, defined by a complex balance of propagation versus spontaneous ignition, based mainly on the reactants’ inlet temperature. At full-load conditions, requiring high pressure and high flame temperature, fuel mixtures with a hydrogen content approaching 100% still bring significant challenges, it is therefore of key importance for the further development of hydrogen-firing capabilities of the gas turbine to improve our present understanding of the interaction between flame propagation and spontaneous ignition and of its role in controlling flame stability and emissions. A series of DNS and LES calculations, featuring complex chemical kinetics and a fully-compressible representation of the reactive flow, are performed on simplified geometrical configurations, yet representative of a sequential combustion system. The present research effort provides novel insight about the combustion characteristics of hydrogen reheat flames at nominal part- and full-load conditions, defining their structure and stabilization mechanism for a range of reactants temperature, as well as modelling guidelines for a reliable numerical approach to reheat combustion.