Dynamics Of Combustion Process Research Articles

Study of the Combustion Mechanism of Zn/KMnO4 Pyrotechnic Composition.

This work aims to investigate the combustion mechanism for a pyrotechnic delay composition (PDC), consisting of zinc powder as a fuel and KMnO4 as an oxidising agent. For this purpose, the compositions were thermally conditioned at several set temperatures, chosen based on our previous work. Tests were also performed for post-combustion residues obtained via combustion of the PDCs in a manometric bomb. The samples were examined by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffractometry (XRD). Furthermore, the obtained results were correlated with previous studies by the authors and compared with data available in the literature. On the basis of tests carried out for thermally conditioned samples, a combustion mechanism was determined for Zn/KMnO4 as a function of temperature. The results show that the combustion process dynamics are independent of equilibrium ratio and limited mainly by diffusion of liquid fuel into the solid oxidising agent. Moreover, it has been revealed that Raman spectroscopy can be effectively used to determine combustion mechanisms for pyrotechnic compositions.

Combustion Dynamics of a Propane–Air Gas Mixture when It Is Ignited by a Streamer Microwave Discharge

The results of experimental studies of combustion of propane–air gaseous mixture when it was ignited by a microwave discharge have been described. The mixture with different propane content fills a sealed radio-transparent tube placed along the axis of a focused linearly polarized quasi-optical microwave beam at atmospheric pressure. Multi-point ignition of the mixture is carried out near one end of the tube by a pulsed microwave discharge with a surface-developed streamer structure. The growth of gas pressure in the tube as propane burned was recorded in the experiments. The microwave pulse energy being invested in high-temperature discharge plasma has been estimated in them. The minimum percentage of propane in the mixture at which the microwave discharge ignites it has been determined in experiments. The time dependence of the pressure increase in the tube as the propane burns determines the combustion process dynamics.

Quasi-gradient models of the dynamics of combustion processes in closed systems

Quasi-gradient models of the dynamics of combustion processes in closed systems

Combustion Oscillations in Bluff Body Stabilized Diffusion Flames With Variable Length Inlet

This paper describes the results of an experimental study to understand the influence of inlet flow disturbances on the dynamics of combustion process in bluff body stabilized diffusion flames of liquid petroleum gas and air. The results show the influence of weak disturbances created by the change in incoming pipe length on the amplitude of pressure oscillations and the phase angle between pressure and heat release. It is seen that the phase delay increases as the entry length increases. The rms value of pressure, however, generally falls with the increase in length. The phase angle is seen to be in the second quadrant, showing that the heat release oscillations damp the pressure oscillations. Therefore, the decrease in the phase angle results in the reduction in damping and hence an increase in pressure fluctuations. The dominant frequencies of combustion oscillations are found to be the low frequency oscillations, and the frequency of oscillations increases with a decrease in the inlet pipe length and an increase in the flow Reynolds number. It is suggested that such low frequency oscillations are driven by vortex shedding at the wake of the bluff body, which energizes the diffusion and mixing process.

Dynamics of combustion processes of n.heptane, i.octane and their mixtures and knocking

Cool flames and multistage ignitions can be regarded as dynamic phenomena of hydrocarbon combustion processes. Any kinetic mechanism must also meet dynamic requirements in order to model the combustion process. Studies of the dynamics of combustion processes were rediscovered only recently, mainly with the help of the CSTR technique. Knocking is regaining interest among combustion researchers and consequently there should be a new interest in the auto ignition of hydrocarbons. Predictive models of the evolution of the end-gas are particularly needed. Knowledge of its dynamic behaviour places more constraints on the modeler. Dynamic behaviours of combustion processes of n .heptane, i .octane and their mixtures (0–100 O.N.) have been studied in a CSTR. Experiments were performed at atmospheric pressure and fuel-rich conditions. Behaviors of systems were studied for different temperatures (510–790 K) and residence time (8–21 s). The n .heptane combustion process exhibits unstable states at low temperatures, whereas i .octane evolves through unstable states at higher temperatures. Mixtures having O.N. less than 97 exhibit unstable states. Heat release rates were experimentally evaluated and compared. The overall results indicate that instability, and hence knocking, is thermokinetic in nature, with kinetics playing the major role.