Mechanism of metal ignition due to fracture

Bolobov, V. I.; Podlevskikh, N. A.

doi:10.1007/s10573-007-0055-9

Cited by 8 publications

(3 citation statements)

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“…式中, ρ g 为气体密度, 在起燃温度附近, 其大小约为1.29 kg/m 3 ; v g 为气体流速, 其数值为33 m/s; η g 为气体黏度, 数值为1.8×10 -5 Pa•s, 计算得出Re≈ 5.9×10 5 , 为湍流条件. 因此对于薄板模型的湍流条件, Nu可进一步表示为 [15] N u = 0.023Re 计的热传导项远低于这一结果 [15][16][17][18] , 故在研究起燃问题时可以忽略 , 当达到着火温度T ig 时,…”

Section: 由于起燃时反应机理为氧吸附机制故单位时unclassified

“…然而, 关于TiO气相对TiO 2 保护性氧化层失效的贡献程度, 目前尚未见研究进行报道. 在钛合金的起燃模型研究方面, 能量方程的基本形式已被广泛研究, 其难点在于起燃阶段反应放热速率的计算 [15][16][17] . NASA等开展的研究工作中, 将近α型高温钛合金燃烧温度(>1800 K)代入实验测定的氧化阶段(1300 K)左右的反应热函数, 但计算得出的燃烧程度与激光着火实验的结果存在较大偏差 [18] .…”

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Ignition mechanism of near α high temperature titanium alloy

Wu,

Mi,

2024

Acta Phys. Sin.

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The risk of titanium fire increases significantly with the development of future aero-engine, however, the burning mechanisms of titanium alloys remain uncertain. Therefore, the ignition behaviors and mechanisms of near α high-temperature titanium alloy are studied in this paper by employing an integrated experiment method, including laser-oxygen concentration ignition method, infrared temperature measurement and observation of molten metal by high-speed camera. Based on this, the ignition boudary curve is determined and the ignition temperatures of the alloy are found to decrease from 1610 to 1550 ℃ with the increasing of laser power from 200 to 325 W and of oxygen concentration from 21% to 60%. The ignition microstructure was characterized by FIB and TEM to study the evolution of reaction products. Pores are found to form under the TiO2 surface layer, which can be attributed to the instablity of TiO. The failure mechanism of protective oxide layer is further analyzed according the oxide layer damage model caused by thermal stress. As temperature approaches the ignition temperature, which locates below the melting point, the high vapor pressure of TiO causes the formation of porous defects under the TiO2 surface, thus accelerating the fracture and failure of the TiO2 layer under thermal stress. It is revealed that critical conditions of temperature and instantaneous temperature change rate are both required to fulfill the ignition. Based on this, an ignition model is futher constructed to discuss the relationship among ignition temperature, laser power and oxgyen concentration. According to the experimental data fitting, the reaction activation energy of TA19 alloy during the ignition stage is calculated as approximately 300 kJ/mol, and the function for ignition temperature calculation is concluded as 8.3×109e-300000/RTigc1/2＋0.52PL-331=0. This provides a theoretical reference for predicting the ignition temperatures of near α high temperature titanium alloy and other types of titanium alloys under complex airflow conditions in aircraft engines.

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