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Development of a competent hydrogen storage material is the foremost task to produce the hydrogen economy feasible. In this work, nitrogen rich porous graphitic carbon nitride (g-C 3 N 4 ) is decorated with palladium−cobalt alloy nanoparticles through a simple cost-effective synthesis method. It is shown, from the solid-hydrogen gas interaction studies, that Pd 3 Co/g-C 3 N 4 has a room temperature hydrogen uptake capacity of 5.3 ± 0.1 wt % at 3 MPa pressure irrespective of its small surface area. Through the perfect alloying of cobalt with palladium in the g-C 3 N 4 matrix, the synergic interaction of Pd 3 Co catalyst centers with g-C 3 N 4 support material is increased by an efficient hydrogen spillover, which has improved the hydrogen uptake capacity of pristine g-C 3 N 4 by about 65%.

We experimentally study thermoacoustic transitions in an annular combustor consisting of sixteen premixed, swirl-stabilized turbulent flames. We show the changes in the characteristics of bifurcations leading to the state of longitudinal thermoacoustic instability (TAI) when equivalence ratio and bulk velocity are systematically varied. Depending upon the bulk velocity, we observe different states of combustor operation when the equivalence ratio is varied. These states include combustion noise, intermittency, low-amplitude TAI, mixed-mode oscillations (MMO), and high-amplitude TAI. We closely examine the special case of MMO that is encountered during the transition from low-amplitude TAI to high-amplitude TAI. We also discuss the global and local flame dynamics observed during the state of MMO. We find that during epochs of low-amplitude oscillations of MMO, all the flames are partially synchronized, while during epochs of high-amplitude oscillations, all the flames are perfectly synchronized. Finally, we replicate the criticalities of bifurcation of the annular combustor in a phenomenological model containing sixth-order nonlinearities.

We experimentally study thermoacoustic transitions in an annular combustor consisting of sixteen premixed, swirl-stabilized turbulent flames. We show the changes in the characteristics of bifurcations leading to the state of longitudinal thermoacoustic instability (TAI) when equivalence ratio and bulk velocity are systematically varied. Depending upon the bulk velocity, we observe different states of combustor operation when the equivalence ratio is varied. These states include combustion noise, intermittency, low-amplitude TAI, mixed-mode oscillations (MMO), and high-amplitude TAI. We closely examine the special case of MMO that is encountered during the transition from low-amplitude TAI to high-amplitude TAI. We also discuss the global and local flame dynamics observed during the state of MMO. We find that during epochs of low-amplitude oscillations of MMO, all the flames are partially synchronized, while during epochs of high-amplitude oscillations, all the flames are perfectly synchronized. Finally, we replicate the criticalities of bifurcation of the annular combustor in a phenomenological model containing sixth-order nonlinearities.

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