Metal-based nanoenergetic materials: Synthesis, properties, and applications

An insight into ignition factors and mechanisms of magnesium based materials: A review

Explosion characteristics of micron- and nano-size magnesium powders were determined using CSIR-CBRI 20-L Sphere, Hartmann apparatus and Godbert-Greenwald furnace to study influence of particle size reduction to nano-range on these. The explosion parameters investigated are: maximum explosion pressure (Pmax), maximum rate of pressure-rise (dP/dt)max, dust explosibility index (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), minimum ignition temperature (MIT), limiting oxygen concentration (LOC) and effect of reduced oxygen level on explosion severity. Magnesium particle sizes are: 125, 74, 38, 22, 10 and 1 μm; and 400, 200, 150, 100, 50 and 30 nm. Experimental results indicate significant increase in explosion severity (Pmax: 7–14 bar, KSt: 98–510 bar·m/s) as particle size decreases from 125 to 1 μm, it is maximum for 400 nm (Pmax: 14.6 bar, KSt: 528 bar·m/s) and decreases with further decrease of particle size to nano-range 200–30 nm (Pmax: 12.4–9.4 bar, KSt: 460–262 bar·m/s) as it is affected by agglomeration of nano-particles. MEC decreases from 160 to 30 g/m3 on decreasing particle size from 125 to 1 μm, its value is 30 g/m3 for 400 and 200 nm and 20 g/m3 for further decrease in nano-range (150–30 nm). MIE reduces from 120 to 2 mJ on decreasing the particle size from 125 to 1 μm, its value is 1 mJ for 400, 200, 150 nm size and <1 mJ for 50 and 30 nm. Minimum ignition temperature is 600 °C for 125 μm magnesium, it varies between 570 and 450 °C for sizes 38–1 μm and 400–350 °C for size range 400–30 nm. Magnesium powders in nano-range (30–200 nm) explode less violently than micron-range powder. However, likelihood of explosion increases significantly for nano-range magnesium. LOC is 5% for magnesium size range 125–38 μm, 4% for 22–1 μm, 3% for 400 nm, 4% for 200, 150 and 100 nm, and 5% for 50 and 30 nm. Reduction in oxygen levels to 9% results in decrease in Pmax and KSt by a factor of 2–3 and 4–5, respectively, for micron as well as nano-sizes. The experimental data presented will be useful for industries producing or handling similar size range micron- and nano-magnesium in order to evaluate explosibility of their magnesium powders and propose/design adequate safety measures.

Explosion characteristics of micron- and nano-size magnesium powders

Experimental research of particle size and size dispersity on the explosibility characteristics of coal dust

Experimental and numerical study on flame propagation behaviors in coal dust explosions

An experimental investigation was carried out on magnesium dust explosions. Tests of explosion severity, flammability limit and solid inerting were conducted thanks to the Siwek 20 L vessel and influences of dust concentration, particle size, ignition energy, initial pressure and added inertant were taken into account. That magnesium dust is more of an explosion hazard than coal dust is confirmed and quantified by contrastive investigation. The Chinese procedure GB/T 16425 is overly conservative for LEL determination while EN 14034-3 yields realistic LEL data. It is also suggested that 2000–5000 J is the most appropriate ignition energy to use in the LEL determination of magnesium dusts, using the 20 L vessel. It is essential to point out that the overdriving phenomenon usually occurs for carbonaceous and less volatile metal materials is not notable for magnesium dusts. Trends of faster burning velocity and more efficient and adiabatic flame propagation are associated with fuel-rich dust clouds, smaller particles and hyperbaric conditions. Moreover, Inerting effectiveness of CaCO 3 appears to be higher than KCl values on thermodynamics, whereas KCl represents higher effectiveness upon kinetics. Finer inertant shows better inerting effectiveness.

Experiment-based investigations of magnesium dust explosion characteristics


 The shaft seal of the pre-lubricated oil pump for the emergency diesel engine in a nuclear power plant is a skeleton oil seal. After about one year of operation, oil will leak from the shaft seal and enter the drive motor, affecting the operation reliability of the emergency diesel engine. By building a numerical simulation platform, the thermal-structure coupling analysis of the skeleton oil seal were carried out and the contact pressure, deformation, Von Misses stress contour and temperature contour of the skeleton oil seal under actual working conditions were studied. Through the establishment of a sealing test device, sealing tests for the concentric smooth shaft, the concentric shaft with a groove on the sealing contact surface, and the eccentricity shaft with a groove on the contact surface were carried out under different shaft surface roughness and hardness. And the influence on the sealing performance of the oil seal was analyzed. The morphology of the sealing lip and the change of material functional groups before and after the trial were analyzed. The study results show that the accuracy and surface quality of the shaft where the oil seal is installed will affect the sealing performance of the oil seal; the main reason for the failure of the skeleton oil seal of the pre-lubricating oil pump is the long-term wear of the transmission shaft and oil seal, which forms grooves on the shaft; and the formation of the grooves will lead to increased leakage. Therefore, improving the wear resistance of the drive shaft is a key. The research results have high reference value for the exploration of the sealing principle of the same type of skeleton oil seal and the analysis of the reasons for the failure of the seal.

Jianming Li

Papers

Experiment-based investigations of magnesium dust explosion characteristics

Cause Analysis of Oil Leakage of the Skeleton Oil Seal for a Diesel Engine Pre-Lubricated Oil Pump