Determining Kinetic Parameters of Cellulose and Lignin Pyrolysis by Gaussian Process Regression (GPR) Method

The ignition and flame-spread processes in the forest and urban fires involve the pyrolysis reactions of biomass materials. One of the most common methods for estimating the fire performance of a material is the evaluation of kinetic parameters, i.e., activation energy (), pre-exponential factor (), and reaction model (()), from thermogravimetric analysis (TG) data. Typically, is estimated based on an Arrhenius-type equation such as Kissinger, Kissinger-Akahira-Sunose (KAS), and Friedman equations. Then, its value is adjusted along with other parameters by assuming a reaction model, e.g., the -order model. This study proposes a Gaussian process regression (GPR) method to determine more reliable kinetic parameters without any assumptions of reaction mechanisms. This paper studies both constant and variable kinetic parameters and compares the GPR method with the conventional methods that assume the -order model. The results of numerically calculated conversion () indicated that the GPR model achieves the best fit with the experimental data

Scale Model Experiments of Toxic Gas Production from the Combustion of Polymers when Applied with Different Droplet Sizes of Water Mist

This research experimentally investigated the combustion of polymeric materials with water mist application in an enclosure, with an emphasis on the production of toxic gases. Two different diameters, ~100 and ~260 μm, were tested. The experimental conditions were determined based on Froude similarity laws for low drop Reynolds number conditions. Droplets and polymers’ physical and chemical properties influence the burning/extinguishing behavior and toxic-gas evolution. In general, larger droplets can extinguish a fire in a shorter time, and toxic gas concentrations in a test chamber decreased more rapidly. However, the large droplets tended to cause the flame expansion phenomenon for thermoplastics by splashing molten polymer. This flame expansion phenomenon led to a rapid increase in toxic-gas production rate. For a smaller size of water droplets, the formation of a char layer tended to slow down the fire-extinguishing process, which caused continuous CO production

Open-field scale-model experiments of fire whirls over L-shaped line fires

This paper presents the results of open-field scale-model experiments of fire-whirl formation over line fires. L-shaped line fires were burned in crosswinds, and the processes of fire-whirl formation were observed. The flame height was measured using an image-processing technique, while two-dimensional velocity components were measured at two different locations using ultrasonic anemometers. Two tests were selected for comparison: test A, in which intense fire whirls repeatedly formed, and test B, in which no whirls were observed. In test A, the wind flow was bent by the fire plume, creating swirling flows near the burning area, thereby forming fire whirls. On the other hand, the crosswind in test B was too fast to be affected by the fire plume. These results confirmed the existence of critical wind velocity to form intense fire whirls. The critical wind velocity, approximately 1 m/s, agreed with the scaling law on the critical wind velocity which was previously developed based on similar experiments of a smaller scale

Assessment of Computer Simulation Software and Process Data for High Pressure Die Casting of Magnesium

Computer software for the numerical simulation of solidification and mold filling is an effective design tool for cast structural automotive magnesium components. A review of commercial software capabilities and their validation procedures was conducted. Aside form the software assessment, the program addressed five main areas: lubricant degradation, lubricant application, gate atomization, and heat transfer at metal mold interfaces. A test stand for lubricant application was designed. A sensor was used for the direct measurement of heat fluxes during lubricant application and casting solidification in graphite molds. Spray experiments were conducted using pure deionized water and commercial die lubricants. The results show that the sensor can be used with confidence for measuring heat fluxes under conditions specific to the die lube application. The data on heat flux was presented in forms suitable for use in HPDC simulation software. Severe jet breakup and atomization phenomena are likely to occur due to high gate velocities in HPDC. As a result of gate atomization, droplet flow affects the mold filling pattern, air entrapment, skin formation, and ensuing defects. Warm water analogue dies were designed for obtaining experimental data on mold filling phenomena. Data on break-up jet length, break-up pattern, velocities, and droplet size distribution were obtained experimentally and was used to develop correlations for jet break-up phenomena specific to die casting gate configurations