Physicochemical properties and thermal behavior of nitrocellulose granules with eutectic mixtures of stabilizers

Examinations of two-component mixtures, namely: triphenylamine + centralite I (TPA + CI) and triphenylamine + akardite II (TPA + AkaII) were carried out using differential scanning calorimetry (DSC), which served to determine phase diagrams. Experimental data were described with NRTL model and eutectic points for both systems were determined. For TPA + CI system, they were equal to xEu,TPA = 0.2899, TEu = 62.9 °C, whereas for TPA + AkaII system they amounted to xEu,TPA = 0.7868, TEu = 117.5 °C. Granules contain mixtures of eutectic composition were obtained. The physicochemical and thermal properties of resultant single base granules were studied. The helium density of both granules was approx. 1.47 g cm−3, the average dynamic force amounted to 0.55–0.60 bar−1 s−1, and the calorific value ranged from 3060 to 3095 J g−1. Both granules should be chemically stable for 10 years of storage at 25 °C; they meet the requirements of STANAG 4582 standard. DSC analysis of decomposition processes was used to determine kinetic parameters and to adjust the chemical reaction model of nth order with autocatalysis (CnB). Reaction order ranged from 2.6 to 3.0, while the activation energy was similar (197–198 kJ mol−1). Based on examination of thermal properties, it was observed that both eutectic mixtures of stabilizers prevent the decomposition reaction more efficiently than the use of individual compounds as stabilizers.

A cubic autocatalator chemical reaction model with limit cycle analysis and consistency preserving discretization

This article deals with the study of some qualitative properties of a cubic autocatalator chemical reaction model. Particularly, we obtain a dynamically consistent cubic autocatalator discrete-time model by applying a nonstandard difference scheme. Analysis of the existence of equilibria and their stability is carried out. It is proved that a continuous system undergoes the Hopf bifurcation at its interior equilibrium, whereas the discrete-time version undergoes Neimark-Sacker bifurcation at its interior fixed point. Moreover, numerical simulation is provided to strengthen our theoretical discussion.

Bifurcation analysis of a discrete-time four-dimensional cubic autocatalator chemical reaction model with coupling through uncatalysed reactant

In this manuscript, we discuss a four-dimensional cubic autocatalator chemical reaction model in continuous form. We investigate the existence of one and only positive fixed point and then we have obtained some parametric conditions for local stability of continuous system by using Routh-Hurwitz stability criteria. Moreover, we discretize the four-dimensional continuous cubic autocatalator chemical reaction model by using Euler’s forward method and then by using a nonstandard difference scheme we obtained a consistent discrete-time counterpart of four-dimensional cubic autocatalator chemical reaction model. Parametric conditions for local asymptotic stability of one and only positive fixed point of obtained system are also discussed. It is shown that the obtained system experiences the Neimark-Sacker bifurcation at one and only positive fixed point by using a general standard for Neimark-Sacker bifurcation. The discrete-time counterpart of genuine four-dimensional system displays chaotic dynamics at different standards of bifurcation parameter. Furthermore, the control of Neimark-Sacker bifurcation and chaos is also deliberated by using a generalized hybrid control scheme, which is based on parameter perturbation and feedback control. Finally, some numerical examples are given to strengthen our theoretical results.

Combustion characteristics of biomass and bituminous coal co-firing in non-isothermal and isothermal conditions

A thermogravimetric method was used to study the combustion of bituminous coal (BC), diverse biomass (wood chips: WC, chaff: CH), and their blends under non-isothermal conditions and isothermal conditions. A higher blending amount of WC or CH under non-isothermal conditions resulted in a lower ignition temperature, burnout temperature, and a greater comprehensive combustion characteristic index. Meanwhile, the co-combustion of BC, WC, and CH all showed inhibiting effects. The inhibition effect was prominent when the blending ratio of WC was below 30%. Under isothermal conditions, with the increase of oxygen concentration and blending amount, the combustion performance of BC improved gradually. The synergistic effect between BC and biomass dominated, and the interaction was more distinct when WC content exceeded 50%. Under both non-isothermal and isothermal conditions, the interaction between CH and BC did not vary at diverse blending ratios. The dynamic results suggested that the chemical reaction model O1 was suitable for stage 1 of the co-combustion of WC and BC, the model diffusion controlled D4 controlled the co-combustion of CH and BC and stage 2 of the co-combustion of WC and BC. The blending ratio of WC or CH with the lowest activation energy was 50%.

Effects of Chamber Width on H2/Air Rotating Detonations

To get the effects of chamber width on the H2/Air rotating detonations, several models with different widths have been investigated. By using a one-step chemical reaction model, one wave is induced in all models. The chamber width has a significant effect on the flow field. When the chamber width is small, the variation of the flow field with the radius is not obvious. But when the width increases, the curvature of the detonation wave reflecting between the inner and outer walls at the head would become enlarged. The height of the detonation wave both on the inner wall and the outer wall has been presented. When the width reaches a limited value, the detonation wave cannot sustain on the inner wall. The normal velocity is used to characterize the detonation wave. The normal velocities on the outer wall and average diameter are almost the same. The former one is approximately the CJ value.