Songyang Li

Review on chemical reactions of burning poly(methyl methacrylate) PMMA

Chemical reactions of burning Poly(methyl methacrylate) (PMMA) are reviewed in this paper although kinetics of thermal decomposition are believed to be fairly simple. Basically, there are three stages in the combustion of PMMA. Firstly, PMMA decomposes to produce monomer methyl methacrylate (MMA). Secondly, monomer MMA decomposes to generate small gaseous molecules that are usually combustible. Finally, these small molecules undergo combustion. Recent studies on the thermal decomposition kinetics and thermal stability of PMMA are also introduced. Results are useful for understanding the heat released of burning PMMA per unit mass of oxygen. Finally, the effects of additives on thermal decomposition are also discussed.

Preliminary studies on burning behavior of polymethylmethacrylate (PMMA)

The burning behavior and combustion mechanism of polymethylmethacrylate (PMMA) were studied by using cone calorimeter, mass spectrograph and gas chromatograph. Main combustion mechanisms of PMMA were reviewed. Results indicated that PMMA would burn steadily under low radiative heat flux; or with thicker samples. The yields of carbon dioxide and carbon monoxide would not be changed. Under high heating rate, there are three broad stages. Firstly, upon heating by external sources, PMMA would decompose to generate monomer MMA and a small amount of other products. Secondly, monomer MMA would decompose to produce small molecule products. Finally, these small gaseous molecules would undergo oxidation, i.e., burning. The main oxygen consumption reaction, i.e., the heat release reaction, is the burning of small molecule products. Main combustion products are found to be carbon dioxide and water, with a small amount of carbon monoxide. At high temperature, the monomer MMA would react with oxygen directly to produce methyl pyruvate, formaldehyde and acetone. However, these reactions are not important in the combustion process of PMMA.

Effect of Different Fuels on Confined Compartment Fire

Experimental simulations of confined compartment fires are conducted in a reduced-scale compartment. Different areas of fire source and different types of fuel are considered in order to investigate the fire growth process and critical condition for flashover according to the changeable fire source characteristics. For these experimental cases, profiles of mean upper layer temperatures and temperature fluctuations are measured. The mass flow rate out from two vents is extensively discussed. A dimensionless model of this compartment fire growth is developed based on the nonlinear dynamics model. The critical criterion for flashover to occur is revised later, which shows that the energy gain rate and loss rate intersect at the turning point of fuel controlled fire and ventilation controlled fire. Finally, the simulation results of the model are compared with experimental data and the critical boundary between flashover and nonflashover is illustrated to show that the theoretical prediction reasonably agreed with experimental results except for polyethylene, where a higher value of fuel property number, , existed.Experimental simulations of confined compartment fires are conducted in a reduced-scale compartment. Different areas of fire source and different types of fuel are considered in order to investigate the fire growth process and critical condition for flashover according to the changeable fire source characteristics. For these experimental cases, profiles of mean upper layer temperatures and temperature fluctuations are measured. The mass flow rate out from two vents is extensively discussed. A dimensionless model of this compartment fire growth is developed based on the nonlinear dynamics model. The critical criterion for flashover to occur is revised later, which shows that the energy gain rate and loss rate intersect at the turning point of fuel controlled fire and ventilation controlled fire. Finally, the simulation results of the model are compared with experimental data and the critical boundary between flashover and nonflashover is illustrated to show that the theoretical prediction reasonably agreed with experimental results except for polyethylene, where a higher value of fuel property number, δ, existed.

Improving Fire Suppression of Water Mist by Chemical Additives

Although water mist fire suppression system (WMFSS) is very common, there are concerns that the system is not efficient in controlling some fires. Additives are proposed to use in a WMFSS for better fire protection. In this paper, different groups of additives for WMFSS will be briefly reviewed. Experimental studies on the surface physical and chemical characteristic of polymethylmethacrylate (PMMA) under four groups of original polymer surface without treatment, self-extinguishment, suppressed by water mist and by water mist with sodium chloride NaCl, are reviewed. The surface profiles, element constitutions, binding energies and functional groups of PMMA surfaces were analyzed with scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR). The near surface molten polymer and bubble layers in burning polymethylmethacrylate (PMMA) are found to be very complicated. The melted surface of burning PMMA is not saturated with pure MMA. Results also demonstrated that chemical reactions do occur while applying water mist. Water mist with NaCl can penetrate deeper on the burning surface of PMMA, suggesting that NaCl might be involved in the extinguishment reactions. The chloride ion from NaCl might be responsible for the interaction with the melting surface of PMMA.

Experimental and Numerical Study of Ceiling Jet Fire in a Confined Reduced-scale Corridor

Safety evaluation and assessment becomes an important topic in the design and operation of tunnels and other underground corridors nowadays. The computational fluid dynamics (CFD) model is an indispensable tool in this process, which can predict the possible fire scenarios by calculating the temperature, concentration, velocity and heat transfer in the domain of concern. In this paper, a validation study for a newly developed CFD code SIMTEC is presented, and the modeling results are compared with experimental data which were obtained through a batch of fire tests in a reduced-scale corridor. The simulations agree reasonably well with measured results. In general, the CFD model predicts the hot layer temperature and CO2 concentration with good accuracy, especially at the position closer to the end of the corridor. The CO concentration close to the fire source is also well captured in the simulation. However, the CO concentration prediction downstream, far away from fire source, is poor. In this study, the effect of corridor fire intensity was also investigated, by varying the fire source size while with other parameters fixed. Both the measurements and the simulation indicate that the average hot layer temperature near the fire source did not change obviously despite the increase in the fire source size.