Experimental and numerical studies of downward flame spread over polymethyl methacrylate (PMMA) with and without addition of triphenyl phosphate (TPP) are reported. Using the micro-thermocouple technique and molecular beam spectrometry, detailed flame structures of PMMA and PMMA+10%TPP were measured. From the experiments and quantum chemistry calculations, the retardancy capability of TPP on gas-phase reaction is proposed. Addition of flame retardant (10%, 20% TPP) results in reduction of the flame spread rate, the mass burning rate and conductive heat flux from the flame to the polymer surface. Numerical calculation was carried out to simulate the downward flame spread over PMMA and PMMA-TPP slabs. Based on the assumption of the TPP gas phase retardancy performance, a modified one-step reaction rate constant with pre-exponent dependent on the TPP mass content in the polymer and TPP retardancy effectivity is proposed. The predicted results have been compared with the data from sophisticated experimental measurement on thermal and chemical structures of both PMMA and PMMA+TPP flames.

Experimental and numerical studies of downward flame spread over PMMA with and without addition of tri phenyl phosphate

In the present paper, the laminar burning velocity and structure of near-stoichiometric premixed laminar flames of methyl methacrylate (MMA) with and without trimethylphosphate (TMP) additives have been studied experimentally and by numerical modeling. The MMA+TMP combustion system is considered as a model system, which simulates gas-phase combustion of polymethyl methacrylate (PMMA) with additive of phosphorus-containing fire retardants (PFRs). The motivation of the present research is to provide a basis for development of a predictive gas-phase chemical kinetic model for inhibition of PMMA by PFRs. The flame sampling molecular beam mass spectrometry was used to determine the spatial variation of the mole fractions of H, OH, PO, PO2, HOPO, HOPO2 and some intermediate hydrocarbons in the one-dimensional burner-stabilized flames. The effect of TMP on the hydrocarbon intermediates in the flames is investigated. The reaction mechanism for combustion of MMA+TMP system has been validated against the novel laminar burning velocity and chemical speciation data. Performances and deficiencies of the kinetic mechanism for MMA flame inhibition are discussed. The sensitivity analysis showed that the insufficiently accurate prediction of mole fraction of H, O and OH results in disagreement for mole fraction profiles of hydrocarbon intermediates in the inhibited flame. Inhibition effectiveness of MMA flame by TMP is compared with that derived from experimental data for other fuels and the observed tendencies are discussed.

Inhibition of premixed flames of methyl methacrylate by trimethylphosphate

The knowledge of the combustion chemistry of oxygenated fuels is essential for the development of detailed kinetic mechanisms suitable for the combustion processes involving biofuels. Moreover, epoxidized olefins, are increasingly used as chemical intermediates or as bulk chemicals. Nevertheless, a dearth of data for their reactivity in the oxidative environment can be observed in the current literature. This study reports the experimental and the model characterization of the flame structure of propylene oxide at stoichiometric and fuel-rich conditions at atmospheric pressure. To this aim, the species mole fractions in three premixed flames stabilized on a flat-flame burner have been quantitatively measured by using the flame sampling molecular beam mass spectrometry. Three chemical kinetic mechanisms retrieved from the current literature involving propylene oxide chemistry have been validated against the novel experimental data. In general, the predictions appeared to be in satisfactory agreement with measurements except for acetaldehyde and ketene. The rate of production analysis in the flame has shown that the discrepancies observed for these species are related basically to the incorrect ratio between the rates of primary reaction pathways of propylene oxide destruction.

Structure of premixed flames of propylene oxide: Molecular beam mass spectrometric study and numerical simulation

https://hal.archives-ouvertes.fr/hal-02934473/document

Methyl-3-hexenoate combustion chemistry: Experimental study and numerical kinetic simulation

Methyl methacrylate (MMA) is the main pyrolysis product of the widely used polymer polymethyl methacrylate; therefore, a compact mechanism of MMA oxidation is of interest for CFD modeling of flame propagation over this polymer. A reduced mechanism of MMA combustion consisting of 263 elementary reactions involving 66 species was developed based on a detailed chemical-kinetic mechanism of MMA oxidation in flames using Chemical Workbench software. The developed mechanism was validated against experimental data on the speed of premixed MMA/air flame at an equivalence ratio 	$$0.9 < \phi < 1.3$$	
 and against literature data on the structure of a MMA/O2/Ar (
 	$$\phi$$	
  = 1) flame stabilized on a flat burner at a pressure of 1 atm. The proposed reduced kinetic model for MMA describes the experimental data with satisfactory accuracy, and the modeling results for the full and reduced mechanisms of MMA oxidation are in good agreement with each other in terms of the concentrations of the major flame species and the concentrations of most combustion intermediates, including hydrogen, methane, ethylene, acetylene, propane, acetaldehyde, methyl acrylate, etc.

Reduced Chemical Kinetic Mechanism for the Oxidation of Methyl Methacrylate in Flames at Atmospheric Pressure

Synthetic and natural polymeric esters find applications in transport and construction sectors, where fire safety is an important concern. One polymer that is widely used is poly (methyl me...

Shanmugasundaram Dakshnamurthy

Papers

Experimental Study and a Short Kinetic Model for High-Temperature Oxidation of Methyl Methacrylate