Quantitative classification of autocatalytic strength for material decomposition based on the ratio of heat release

Effects of swirl number on flame tip oscillation of a Bunsen type premixed flame with burner rotation are experimentally investigated. The flame tip oscillation frequency v remains unchanged as the Swirl number S is bellow 0.11, and decreases with increasing S for S>0.11. This suggests that the effect of burner rotation on the flame tip oscillation frequency becomes significant as S exceeds 0.11. When S=0, value of St^<*2>/Ri almost coincides with an empirical correlation (St^<*2>/Ri=0.00028Re^<*2/3>, here, St^*, Rt, and Re^* are, the Strouhal number normalized by the heat release ratio, the Richardson number, and the Reynolds number normalized by the heat release ratio, respectively) proposed by Kostiuk and Cheng. As S is further increased, the gradient of the relationship between St^<*2>/Ri and Re^<*2/3> decreases and finally becomes flat as S exceeds around unity. These results indicate that the Swirl number plays an important role in determining the flame tip oscillation frequency as well as the Reynolds number.

Vent sizing of cumene hydroperoxide (CHP) system under fire scenario considering emergency flooding measure

Cumene hydroperoxide (CHP) and its derivatives have caused many serious explosions and fires in Taiwan as a consequence of thermal instability, chemical contamination, and even mechanical shock. It has been employed in polymerization for producing phenol and dicumyl peroxide (DCPO). Differential scanning calorimetry (DSC) was used to analyze the thermal hazard of CHP in the presence of sodium hydroxide (NaOH), sulfuric acid (H2SO4), and sodium bisulfite (Na2SO3). Thermokinetic parameters for decomposition, such as exothermic onset temperature (T0), maximum temperature (Tmax), and enthalpy (ΔH), were obtained from the thermal curves. Isothermal microcalorimetry (thermal activity monitor, TAM) was employed to investigate the thermal hazards during CHP storage and CHP mixed with NaOH, H2SO4, and Na2SO3 under isothermal conditions in a reactor or container. Tests by TAM indicated that from 70 to 90 °C an autocatalytic reaction was apparent in the thermal curves. According to the results from the TAM test, high performance liquid chromatography (HPLC) was, in turn, adopted to analyze the result of concentration versus time. By the Arrhenius equation, the activation energy (Ea) and rate constant (k) were calculated. Depending on the process conditions, NaOH was one of the incompatible chemicals or catalysts for CHP. When CHP is mixed with NaOH, the T0 is induced earlier and the reactions become more complex than for pure CHP, and the Ea is lower than for pure CHP.

A combined theoretical and experimental analysis of thermoacoustic interaction mechanisms of a lean pre-mixed swirl-stabilized gas turbine burner is presented. A full-scale gas turbine burner has been tested in an atmospheric test rig. The test facility was equipped with loudspeakers to excite the acoustic field and with arrays of microphones to measure the response of the acoustic field to the forcing signal. With this set-up transfer matrices relating the acoustic pressure and velocity on both sides of the flame front have been measured. A laser absorption measurement technique allowed for measurement of the fluctuations of fuel concentration in the mixture. Heat release fluctuations were monitored using a photo-multiplier. The measurement of the acoustic field, heat release and equivalence ratio fluctuations have been measured simultaneously. Special attention has been given to the role of fuel concentration fluctuations in the thermoacoustic interaction mechanism. In order to be able to clearly separate this mechanism from other possible mechanisms, all the experiments have been performed in pre-premixing mode as well. In pre-premixing mode the fuel is injected far upstream of the burner in order to avoid fuel concentration fluctuations at the burner location. This is in contrast with premixing mode where fuel and air are mixed in the burner. An acoustic flame model has been derived. The model includes the well-known interaction mechanism of equivalence ratio fluctuations but also includes a novel mechanism that is caused by fluctuations of vorticity. This latter mechanism relates the turbulent flame speed via turbulence intensity fluctuations to the acoustic field. The idea is that periodic acoustic fluctuations cause periodic changes of the turbulence intensity. The turbulence intensity strongly affects the turbulence flame speed. The fluctuations of the turbulent flame speed result in fluctuations of the heat release. This turbulence intensity fluctuation model has been compared with the measured pre-premix transfer functions and shows an excellent agreement. The measured transfer functions in premix mode have been compared with the model that includes fluctuations of fuel concentration and turbulence intensity. Also in this case a very good agreement is found. Moreover, it has been demonstrated that the phase relation between measured equivalence ratio fluctuation and heat release corresponds to the model.

Runaway reaction and thermal explosion evaluation of cumene hydroperoxide (CHP) in the oxidation process

Organic peroxides have caused many serious explosions and fires that were promoted by thermal instability, chemical pollutants, and even mechanical shock. Cumene hydroperoxide (CHP) has been employed in polymerization and for producing phenol and dicumyl peroxide (DCPO). Differential scanning calorimetry (DSC) has been used to assess the thermal hazards associated with CHP contacting sodium hydroxide (NaOH). Thermokinetic parameters, such as exothermic onset temperature (T0), peak temperature (Tmax), and enthalpy (ΔH) were obtained. Experimental data were obtained using DSC and curve fitting using thermal safety software (TSS) was employed to obtain the kinetic parameters. Isothermal microcalorimetry (thermal activity monitor, TAM) was used to investigate the thermal hazards associated with storing of CHP and CHP mixed with NaOH under isothermal conditions.

Chemiluminescence, as an effective diagnostic method, is often used to study the flame structure, heat release, and equivalence ratio, which are significantly important for describing the complex combustion process. In this work, the time histories of chemiluminescence emission from OH*(A2Σ+) and CH*(A2Δ) in reacting methane/oxygen/argon mixtures have been simultaneously measured behind reflected shock waves. Experiments were conducted at pressures around 1.0 and 2.0 atm, equivalence ratios of 0.5 and 1.0, a fuel concentration of 0.2%, and temperatures ranging from approximately 1725 to 2743 K. Based on the measured OH* chemiluminescence time histories, the rate constant of reaction CH + O2 ⇒ OH* + CO was determined to be 9.24 × 1015 × T-0.4 exp(-4150 cal·mol-1/RT) cm3 mol-1 s-1. A methane combustion mechanism involving the OH* and CH* reaction kinetics was constructed. The reliability of the constructed kinetic mechanism was verified by using the experimental kinetic data of OH* and CH* chemiluminescence, including the time histories and relative peak intensities.

Diallyl orthophthalate as a reactive plasticizer for improving PVC processability, Part III: Curing, properties, and phase separation

Investigation of the mechanism of cumene oxidation in the liquid phase by an inhibition technique: Formation of the reaction products and their effect on decomposition of the hydroperoxide onto radicals

The self-accelerating decomposition temperature (SADT) of solids of the quasi-autocatalytic decomposition type

Supercooling suppression and thermal behavior improvement of erythritol as phase change material for thermal energy storage

Effects of adjacent space on spill flame of chemical hazardous materials container fire

Kinetic parameter estimation for decomposition of organic peroxides by means of DSC measurements

Certain polymers, such as polyvinylidene fluoride (PVDF), polyimide (PI), and poly (phthalazinone ether sulfone ketone) (PPESK), are commonly used separator materials in batteries. However, during the thermal runaway (TR) processing of batteries, significant heat is released by the combustion of the polymer separator. Therefore, analysis of the fire behaviors of polymer separator materials will facilitate a more comprehensive quantitative evaluation of battery thermal risk. This paper investigated the combustion properties of three types of polymers, namely, PVDF, PI, and PPESK, as potential separator materials by cone calorimetry and thermogravimetry (TG). A series of characteristic parameters, including ignition time (TTI), heat release rate (HRR), smoke production rate (SPR), and total heat release (THR), were evaluated for three polymers and blends (PI/PVDF, PPESK/PVDF) under an external heat flux of 45 or 60 kW/m2, respectively. The combustion characteristics and fire hazards of the three polymers and corresponding mixtures were analyzed through the comparative analysis of experimental data and phenomena. Under 60 kW/m2, the HRR curves of all polymers presented two peaks, while PI/PVDF and PPESK/PVDF mixtures exhibited one obvious peak. Moreover, the peak HRR (pHRR) for the mixed polymers was higher, indicating a relatively higher fire risk. However, in the application scenario, the mixed state represents the main polymer form as the active separator materials in batteries. The results showed that the specific coupling behaviors were related primarily to the component type. This work will help evaluate the fire risk of polymeric separator materials based on the combustion characteristics to predict the safety of mixtures in batteries and develop new methods for fire suppression.

Oxidation and spontaneous combustion characteristics of particulate coal under stress–heat–gas interactions