Assessment of the Thermal Radiation Spread in Special Conditions

Increase of the requirements for the safety of hazardous production facilities stimulates the development and improvement of the methodological approaches to accidents consequences assessment on the main gas and other pipelines. Existing models for determining heat fluxes from radiating flame surfaces are focused on assessing damage under standard conditions when the epicenter of the accident is at the same altitude level with potential recipients and there are no barriers between them. In practice, special conditions are often implemented, in particular: fires on the pipelines located in the mountainous areas, safe passage of aircraft near the burning site, protection of objects from thermal radiation by installing impenetrable screens. Approaches are proposed related to assessing heat fluxes at the receiving sites located at different altitude levels with the fire source, as well as during accidents with ignition on the gas pipelines in the presence of screens protecting against thermal radiation. A parameter is introduced that describes the effect of the multilevel location of the source and the recipient on radiation — the coefficient of change in the thermal radiation flux from the side surface of a column-type fire in the absence of a wind, depending on the location height and distance in relation to the ground source of combustion of the site receiving the radiation. An expression is given for determining safe height of the flight of aircraft over a column-type fire in the range of flame heights from 50 to 850 m. Isolines of the fields of heat fluxes from the flame of a high-speed flat jet are calculated when the radiation is screened by a wall located at a normalized distance. The results obtained make it possible to predict the consequences of accidents on the main gas pipelines with gas ignition considering the relief, to assess the boundaries of safe corridors for flights of the aircraft near gas pipelines, and to efficiently develop means of protecting objects surrounding the main pipelines from thermal radiation from a flat torch.

3D graphene aerogel-supported copper azide nanoparticles as primary explosive with excellent initiation performance

Copper azide (CA), a high energy primary explosive, had been investigated with various supporter materials to reduce its sensitivity characteristics. However, effective supporter had not been designed to fully reduce CAs sensitivity characteristics. Hence, we presented a three-dimensional (3D) graphene aerogel-supported CA (CA-GAs) strategy to meet those needs. CA-GAs was prepared using 3D GA as the framework to uniformly grip CA. The SEM and XRD measurements revealed that CA nanoparticles were fully dispersed on GAs, the in-situ azidation reaction of Cu precursor and CAs crystalline structure were not affected by GAs. DSC further verified the thermal stability of CA-GAs. Moreover, electrostatic ignition experiment was employed to investigate CA-GAs’ ignition time, input energy, and electrical ignition performance. Those results showed that CA-GAs could be reliably detonated by a 3.5 [Formula: see text] SCB, the average electric ignition voltage, ignition time, and input energy of CA-GAs were 19.125 V, 21 [Formula: see text]s, and 0.56 mJ, respectively. All these results illustrated that GAs was an effective supporter for the stabilization of CA.

Study on the Mechanism of Gas Ignition by Friction Effect of Hard Quartz Sandstone Instability

When the upper part of a high gas coal seam has hard and thick sandstone roof, the gas explosion accident in goaf is even caused by roof collapse. Taking the mining of 1007 working face of 10 coal seam under Xia KuoTan Coal Mine as the engineering background, using the method of indoor experiment and theoretical analysis, the possibility of rock friction effect igniting gas is studied. Under the engineering geological conditions, the results show that the heat produced by the friction process of hard sandstone can ignite gas. According to the 3DEC numerical simulation, the instability characteristics of the overburden hard rock are studied. The results show that the size of the slab instability area is not changed when the length of the working face increases. When the thickness of the roof is increased, the area of sliding instability is increased and the degree of sliding instability is more intense. At the boundary of the tunnel, the overlying strata are subjected to the largest shear stress, and it tends to form a friction surface with greater slip instability.

Theoretical substantiation of the hypothesis on the nature of the formation of a cylindrical erup

Relevance of the work. Cryovolcanic phenomena in the permafrost zone of the Earth are at the very initial stage of study. Purpose of this paper is to form and study theoretical ideas about the nature and mechanism of formation of a cylindrical vent in order to obtain scientifically substantiated knowledge that can subsequently be useful in developing the methodology and content of field studies, laboratory experiments and predictive calculations. The implementation of this goal is based on the main working hypotheses of the formation of the studied cryogenic volcano and the cryogenic processes that caused it in the permafrost massif: gassing (gas saturation) associated with the existence of stratal underground ice and the response of permafrost to climate fluctuations; degassing, accompanied by pneumatic release of rock and ice to the adjacent territory. Attention is also drawn to a hypothesis based on the concept of the migration and accumulation of hydrocarbons in the permafrost strata as a result of macro- and micro-seepage of gases, leading to the formation of near-surface redox zones favorable for the biodegradation of hydrocarbons with the formation of secondary microbial gases, primarily, methane. Methodology of research provides for a comparative analysis of characteristics of the composition and properties of homogeneous elements of the object under study, identified as a result of primary measurements and visual examinations and presented theoretical hypotheses. Results of work and scope of their application made it possible to reveal the theoretical prerequisites for substantiating the hypothesis about the complex nature of the formation of a cylindrical vent of a cryogenic volcano, which is expressed by a combination of long-term mechanical and thermobiochemical processes in permafrost. Conclusions. The authors put forward a hypothesis about the significant contribution of biochemical processes with the participation of hydrocarbons, including in the liquid phase, in the formation of a primary cavity (vent) of a regular cylindrical shape in the rock mass at the stages preceding the explosive outburst of crater rocks. As an interconnected one, the authors theoretically substantiated the hypothesis of the formation of a meromictic reservoir with an established unmixed stratified anaerobic deep part in the cryovolcano vent after the explosive destruction of the heaving mound. An explanation of the nature of the source of gas ignition (from a spark formed during the collision of solid rock fragments at the time of cryovolcanic outburst of rocks), as well as the ferroelectric effect that occurs during deformation of frozen rocks is presented. Keywords: permafrost, ice, permafrost mound, cryovolcanism, vent, thermobiochemical process.

Evolution of Microwave Electric Field on Power Coupling to Plasma during Ignition Phase

During the gas ignition process, the plasma and the microwave electric fields are evolved with time together in the plasma volume. The spatio-temporal evolution pattern of microwave-radiated plasma parameters is reported here, highlighting the role of these electric fields on power coupling processes. Evolutions of electric field and so power coupling processes are calculated using the finite element method (FEM). It is observed that the main power coupling mechanism is electron cyclotron resonance (ECR) method; however, with the evolution of plasma, the mode shifts from ECR to off-ECR-type heating with time. Off-ECR heating in the form of upper hybrid resonance (UHR) method, electrostatic (ES) ion acoustic wave heating method is important heating mechanisms during highly dense plasma condition, when density is above critical density for launched frequency, 2.45 GHz. The conclusions on the shifting of heating mechanisms are also drawn based on the 3D maps of spatio-temporal plasma density and hot electron temperature evolution.

Study of Visualization Experiment on the Influence of Injector Nozzle Diameter on Diesel Engine Spray Ignition and Combustion Characteristics

The elementary research of spray and combustion is of great significance to the development of compactness of modern diesel engines. In this paper, three injectors with different nozzle orifice diameters (0.23 mm, 0.27 mm and 0.31 mm) were used to study the diesel spray, ignition and flame-wall impingement visualization experiment. This paper studied the influence of different nozzle sizes on the trends of spray, ignition and flame diffusion under the flame-wall impinging combustion and used the flame luminosity to characterize the soot generation in combustion. By analyzing the quantitative data, such as spray penetration, ignition delay, flame area and flame luminosity systematically, it was shown that the smaller nozzle benefitted diesel combustion to some extent. The 0.23 mm nozzle injector in these experiments had the best fuel-air mixing effect under 800 K. The length of the spray liquid under the 0.23 mm nozzle condition was 19% and 23% shorter than that of 0.27 and 0.31 mm, respectively. Smaller orifice size of the nozzle can help to reach the gas ignition conditions more effectively. Without liquid fuel impingement, the simple flame-wall impingement will not change the trend of the nozzle influence on combustion. The total amount of accumulated soot according to the approximate luminosity spatial integral calculation in the combustion process was reduced by 37% and 43% under 0.27 mm and 0.23 mm nozzles, respectively, which is favorable for the clean combustion of diesel engines.

INFLUENCE OF NONEQUILIBRIUM FACTORS OF KEY REACTIONS ON SYNTHESIS GAS IGNITION

The nonequilibrium processes of ignition and combustion of a syngas-air mixture behind a shock wave is studied using the mode model approach.

DEVELOPMENT OF MODERNIZED GAS BURNER DEVICE OF SERIES GS-M FOR TUNNEL KILNS OF CERAMIC BRICK FIRING

On the basis of gas-burning devices of the GS series, new devices have been developed, in which gas channels are installed for operation in the mode of maximum or minimum flame length. This allows to increase the stability of the flame at low temperatures of the working space (below the natural gas ignition temperature), which in turn provides an increase in the economic performance of the tunnel kiln firing ceramic bricks. Bibl. 5, Fig. 2.