Ignition and combustion characteristics of composites materials of DAP-4 and nano-tungsten particles

Copper–chromium alloy material, as one of the most important electrode contact materials in the field of electrical contact, has been widely used in vacuum interrupters. To replace the SF6 circuit breakers at higher voltage levels and larger breaking capacities, there is an urgent need for new electrode contact materials to meet the comprehensive electrical performance requirements of high withstand voltage, high insulation, and erosion resistance. In this study, a novel electrode contact material, CuCr55, for a 252 kV single break vacuum interrupter was prepared by the arc melting method, and the microstructures of arc-cast CuCr25, melt-infiltrated CuCr50, and arc-melted CuCr55 materials were compared. The vacuum arc ignition and erosion characteristics of arc-melted CuCr55 contact materials were analyzed in detail. A high-speed camera was used to capture the arc ignition characteristics of short-circuit currents, and the critical currents for the formation of anode spots for different materials were obtained. The micro-morphology of the contact surface after erosion was observed using electron microscopy. The research results showed that the arc-melted CuCr55 contacts had a fine and uniform distribution of chromium particles with spherical and dispersed microstructures. After vacuum arc erosion, there was no material fracture or significant protrusion on the surface of CuCr55 contacts, and they exhibited a higher critical current for anode spot formation and good uniform erosion characteristics.

To investigate closed-cycle diesel engine (CCDE) ignition and combustion characteristics, a new kinetic model (Carbon-dioxide Oxygen Environment, COE) is presented, which considered the CO 2 chemical effect based on diesel surrogate fuel (n-heptane, C 7 H 16 ). Firstly, the COE model is established by simplifying the LLNL mechanism, adding the new reaction pathways using quantum chemistry and modifying the kinetic parameters. Secondly, a visualization constant volume combustion chamber experimental system is constructed to record the non-premixed ignition and combustion process of C 7 H 16 under different CO 2 /O 2 environments (35% CO 2 /65% O 2 , 40% CO 2 /60% O 2 , 50% CO 2 /50% O 2 , 60% CO 2 /40% O 2 ). Finally, ignition characteristics, combustion characteristics, sensitivity analysis, and chemical effect of CO 2 under different CO 2 /O 2 environments are discussed between simulation and experiment. The results show that the COE model is suitable for studying the closed-cycle diesel engine ignition and combustion characteristics, whose maximum errors of ignition delay time and ignition location are 6.1% and 6.7%, respectively. The phenomenon of combustion decay appears before the end of combustion at 35% CO 2 and 40% CO 2 . The average flame length decreases significantly by 47.8% due to flame lift-off at 60% CO 2 . The cumulative flame intensity decreases by 34.4% at 60% CO 2 compared to 50% CO 2 . The sensitivity coefficient of H 2 O 2 + M → 2OH + M to temperature increases by 6.2% as CO 2 increases from 40% to 60%. The ratio of the chemical to physical effects of CO 2 rises from 7.6% to 17.3% as the CO 2 volume fraction increases. The third-body effect promoting OH formation more significantly than the inhibitory effect of the direct chemical effect.

Effects of ambient density and injection pressure on ignition and combustion characteristics in diesel spray under plateau cold-start conditions

Ignition and lateral flame spread characteristics of certain composite materials

Effect of Ultrafine Al/B, Ti/B, and Fe/B Powders on the Ignition and Combustion Characteristics of High-Energy Materials

Numerical modeling of endothermic pyrolysis and ignition delay of composite materials exposed to an external radiant heat flux

A feature of Chinese historical buildings is the preservation of many traditional customs, such as using candles and incense burners, and decorating the rooms with some textiles. Therefore, there are both many fire sources and combustible materials indoors, which puts a huge threat to fire safety. Although some researchers have experimentally studied the ignition and fire spread characteristics of several combustible materials, to better conduct fire risk assessment in historical buildings, the dynamic burning behavior of common fuels should be further analyzed. This paper carried out experimental investigations for flammability and fire spread behaviors of combustible materials usually used in Chinese historical buildings, which are made of both natural fiber and synthetics. Considering practical applications, the size of each sample is chosen from standard-testing size to real size. It is summarized that there are large deviations among different materials due to their ingredients, textures, structures, etc. The natural-based materials are easy to be ignited and burn up quickly, and some synthetics reveal sharp increase in heat release rate. For the synthetics, as it can melt during burning, the flame spread process is accompanied by dripping. Once there are some combustibles near it, the dripping part is liable to ignite the combustibles and cause damage to cultural relics. Based on these knowledges, fire hazards of different materials in Chinese historical buildings are evaluated.

The characteristics of ignition and combustion and activation energy of YiMin coal and organic waste liquid and their blends in different blending ratio are studied by thermogravimetric analysis. The experimental results show that ignition and burning characteristics of coal are better than organic waste liquid. The ignition temperature of organic waste liquid will decrease, while the maximum weight loss rate will increase and the time corresponded to maximum weight loss rate will get earlier with the increase amount of the coal added. Activation energy of samples is calculated. Compared with the coal, the activation energy of the low temperature zone of organic waste liquid is lower and its ignition characteristic is better. The activation energy of the high temperature zone is bigger and its combustion characteristic is worse. The coal added will reduce the ignition characteristic but promote the combustion characteristic of organic waste liquid. The analysis of the combustion index S indicates that the comprehensive combustion characteristic of the organic waste improves significantly when coal is blended, and the best blending ratio is 2:3.

The experimental results of studies of the ignition and subsequent combustion processes of the single drops of organic coal–water fuels (OCWFs) arranged on the junction of a quick-response thermocouple (thermal inertia, <1 s) in an atmosphere of heated (600–1000 K) air are presented. The particles of 2B brown coal and D coal, water, and oils of different types (turbine, motor, and transformer oils) were used as the main OCWF components. The effect of the degree of grinding (fineness) of the solid fuel components of OCWFs on the following integral characteristics of the ignition and combustion of prepared fuel compositions was established: the delay times of ignition and complete combustion. A decrease in the delay times of ignition and complete combustion with decreasing the degree of grinding was detected (in a range of 40–200 μm used as an example). The reasons and special features of the influence of this factor on the integral characteristics of the test processes were recognized.

Since there exist discharge problems in gas insulated metal-enclosed switchgear due to internal metal particle movement, the study in this paper thus, conducted an experiment and simulation research on the movement characteristics of particles, where the charge on particle and the collision recovery coefficient (CRC) was obtained. When the electrode is brass, the charge on the particle is close to the theory one and the CRC of aluminum, stainless steel and particle are 0.52, 0.75 and 0.79 respectively. Accordingly, the study, in order to take the particle charge and its collision process into consideration, established a particle movement model, and conducted a test has thereof. The results show that there exists excellent consistency between charge and its collision. According to the research, the relationship between particle size, material and collision characteristics was revealed. The result shows that under DC voltage the metal particle collision frequency decreases with the increase of particle size when the material of the particles is the same. The time difference between particles' moving to high voltage electrode and ground electrode becomes greater with the increase of the size of the particle. When the particle material is different, the collision characteristics are influenced by its density and collision recovery coefficient of restitution. Particle motion velocity loss becomes less before and after the collision when its collision recovery coefficient of restitution is larger. So the collision frequency is higher. The research results in this paper can offer some reference value to particles suppression measures in gas insulated metal-enclosed transmission line.

The features of ignition and combustion of composite propane-hydrogen fuel: Modeling study

In dredging operations, the efficient transportation of dredged materials presents a significant and intricate challenge. This study focuses on the motion and resistance characteristics of coarse-grained dredged materials during pipeline conveyance. A specialized simulation experiment platform was developed to investigate the horizontal pipeline transport of coarse-grained materials. The experimental design encompassed varying particle diameters, material volume concentrations, and mixed average flow rates to analyze the motion and resistance characteristics of these materials in horizontal pipelines. Three distinct particle beds were identified based on different coarse particle motion states. This study statistically analyzed the impact of the particle diameter and material volume concentration on the transport efficiency of coarse particle populations. The key findings indicate that the mixed mean flow rate significantly influences the transportation efficiency of coarse particle groups, whereas the particle diameter and material volume concentration have a minimal effect. Specifically, coarse particles with a diameter of 0.9 mm demonstrated optimal water flow following, and higher mixed mean flow rates correlated with increased transportation efficiency of the coarse particle group. The transition speed of the coarse particle group flow type was notably affected by the material volume concentration and particle diameter, exhibiting a linear relationship. Therefore, when the particle size of the dredged material increases or the concentration increases, the average flow rate of the mixture is appropriately increased to ensure that the flow pattern of the dredged material in the pipeline remains in a non-homogeneous suspended flow pattern, thereby improving the efficiency and stability of the transportation system. By optimizing the conveying characteristics of coarse-grained materials, the pipeline conveying efficiency can be improved and the risk of pipeline wear and clogging can be reduced, thus lowering engineering costs and energy consumption and promoting technological innovation in related industries. In addition, this research can enhance engineering safety, reduce resource waste and environmental pollution, promote sustainable development, and provide important theoretical support and practical guidance for emerging fields such as deep-sea mining and environmental engineering.

The kinetic parameters of high temperature decomposition kinetics are widely used in evaluating the characteristics of thermal explosion, ignition and combustion of energetic materials. At present, the true and correct data on the high temperature kinetics of energetic materials condensed phase reactions are unknown and probably will remain unattainable in the nearest future. This is because of enormous technical difficulties to obtain such information and the absence of proper theoretical approaches for treatment of non-isothermal data. Evidently, with highly exothermic reactions it is impossible to conduct experiments at elevated temperatures using approaches of a low heating rate or isothermal ones. The improvement of characteristics of existing devices for thermal analysis is impeded by both technical complications and difficulties of performing experiments with ultrathin specimens of energetic material to ensure the conditions of uniform heat-up of the bulk of the substance. Based on the results of numerical simulation it is shown in this paper that the approach suggested 50 years ago by A. G. Merzhanov of using ignition delay data for deriving high temperature kinetics was not theoretically justified and can provide only very approximate values for such kinetics. The paper concludes on the today’s relevance of the tasks on elaboration of mathematically justified techniques for determining kinetic parameters of global exothermic condensed-phase reaction, which will be based on the experiments on EMs ignition.

A system has been fabricated to study the combustion characteristics of non-metallic materials in stationary and flowing oxygen-enriched atmospheres at ambient conditions. A description of the system and two current research programs underway are presented. In the first program five materials (Kydex V, Kydex 100, Kydex 200, Acrylonitrile Butadiene Styrene (ABS) plastic and polycarbonate) were evaluated under ambient conditions for their ignition and self-extinguishment characteristics according to two standardized ASTM tests. These five materials are vacuum-formable plastics currently under consideration for use in a series of new ground-transport vehicles being produced for the Olympics to be held in Sydney in 2000. Before these candidate materials can be approved, however, it was necessary to collect data on their ignition and combustion characteristics to ensure that they meet relevant Australian standards. These materials are ranked, from most ignition and burn resistant to least ignition and burn resistant, in the following order: Kydex 200, Kydex 100, Kydex V, polycarbonate, and ABS. The second program evaluated six materials (clear and blue polyethylene, butyl rubber, nitrile rubber, Polyvinylchloride, and silicone rubber) due to their common use as endotracheal tube materials. These materials, in a standard configuration, are evaluated as a function of tube material and combustion characteristics. Results given include flame characteristics, burn time, flame spread velocity and fuel burn rate. None of the six materials evaluated are appropriate choices for an endotracheal tube material if any ignition sources are present due to the vigorous burning exhibited.

The behavior of a bed of fibrous combustile material, exemplified by pure cotton (ASTM, 1982), when subjected to a controlled stream of heated air, was examined experimentally. The effects of some controlling basic physical parameters, such as sample compactness and ventilation, air stream temperature, and air stream velocity on the spontaneous ignition and combustion characteristics were established. Moreover, the observed spontaneous ignition delay time was correlated in terms of these variables. The effective activation energy during the ignition reactions was derived and shown to be dependent on the compactness of the sample.