Experimental study on frictional heating due to return idler seizure failure in belt conveyors
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摘要:
回程托辊卡死是导致带式输送机火灾的主要原因之一。为研究带式输送机回程托辊卡死故障摩擦升温特性，采用平台实验与数值模拟相结合的方法，研究了输送带速度、巷道风速和环境温度对卡死回程托辊温度的影响，结果表明：卡死回程托辊温度随环境温度和输送带速度的增加而显著升高，温度达到稳态的时间延长；巷道风速的提高有效降低了卡死回程托辊温度并缩短了温度达到稳态的时间。考虑到输送带磨穿卡死的回程托辊导致托辊内部煤粉积聚并引发火灾的情况，进一步研究了输送带速度、巷道风速、环境温度及卡死回程托辊内煤粉积存比例（煤粉在托辊内部积存体积与托辊可容纳煤粉最大体积之比）对煤粉最高温度的影响，结果表明：输送带速度、巷道风速和环境温度对卡死回程托辊内煤粉最高温度的影响，与对卡死回程托辊温度的影响规律一致；卡死回程托辊内煤粉积存比例的增加会加剧煤粉温度的升高；在环境温度为20 ℃、输送带速度为3.5 m/s、巷道风速为1 m/s、100%煤粉积存比例的工况下，煤粉最高温度达87.5 ℃，较25%煤粉积存比例时升高了43.2 ℃，高于中低阶煤的自燃临界温度，火灾风险显著增加。
Abstract:Seized return idlers are one of the main causes of fire in belt conveyors. To investigate the frictional heating characteristics of seized return idlers in belt conveyors, a combination of platform experiments and numerical simulations was used to study the effects of conveyor belt speed, roadway airflow velocity, and ambient temperature on the temperature of the seized return idlers. The results indicated that the temperature of the seized return idler increased significantly with the rise in ambient temperature and conveyor belt speed, and the time required to reach thermal equilibrium was prolonged. An increase in roadway airflow velocity effectively reduced the temperature of the seized return idlers and shortened the time to reach thermal equilibrium. To further assess the fire risk from coal dust accumulation within stuck rollers due to belt wear, the study explored the effects of conveyor belt speed, roadway airflow velocity, ambient temperature, and coal dust accumulation ratio in the seized return idlers (defined as the ratio of accumulated coal dust volume to the maximum capacity of coal dust volume in the idlers) on the maximum temperature of the coal dust. The results revealed that the effects of conveyor belt speed, roadway airflow velocity, and ambient temperature on the maximum temperature of coal dust in the seized return idlers were consistent with their effects on seized roller temperature. Additionally, an increase in the coal dust accumulation ratios in the seized return idlers resulted in a more significant rise in coal dust temperature. Under conditions of an ambient temperature of 20 °C, conveyor belt speed of 3.5 m/s, roadway airflow velocity of 1 m/s, and a 100% coal dust accumulation ratio, the maximum temperature of coal dust reached 87.5°C, which was 43.2 °C higher than that at a 25% accumulation ratio. This temperature exceeded the threshold value of spontaneous combustion for low- to medium-grade coal, indicating a substantial increase in fire risk.
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Keywords:
- belt conveyor /
- return idler /
- idler seizure failure /
- frictional heating /
- externally caused fire
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图 5 不同工况下卡死回程托辊最高温度及温度达到稳态所需时间
Figure 5. Maximum temperature of seized return idlers and time to reach thermal equilibrium under different conditions
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图 7 平台实验数据与数值模拟数据对比
Figure 7. Comparison between platform experimental data and numerical simulation data
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图 8 卡死回程托辊温度数值模拟结果
Figure 8. Numerical simulation results for seized return idler temperatures
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图 9 不同工况下卡死回程托辊内煤粉最高温度变化曲线
Figure 9. Variation curves of the maximum coal dust temperature in seized return idlers under different conditions
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图 10 不同工况下卡死回程托辊内煤粉最高温度
Figure 10. The maximum coal dust temperature in seized return idlers under different conditions
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图 11 不同工况下卡死回程托辊及煤粉温度场截面
Figure 11. Temperature field cross-section of seized return idlers and coal dust under different conditions
表 1 实验工况
Table 1 Experimental conditions
工况 输送带速度/（m·s−1） 环境温度/℃ 巷道风速/（m·s−1） 1 0.5 15 1 2 1.0 15 1 3 1.0 15 4 4 1.0 20 1 
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表 2 模型基本参数
Table 2 Basic parameters of the model
模拟物体 比热容/（J·kg−1·K−1） 密度/（kg·m−3） 导热系数/（W·m−1·K−1） 托辊 440 7 878 76.20 煤粉 1 400 1 600 0.10
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表 3 模拟数据与平台实验数据的Pearson相关系数
Table 3 Pearson correlation coefficients between simulation data and platform experimental data
工况 不同测点处模拟数据与平台实验数据之间的Pearson相关系数 输送带与卡死回程托辊摩擦接触点 卡死回程托辊底部 1 0.998 55 0.966 13 2 0.993 03 0.989 92 3 0.994 38 0.956 21 4 0.991 57 0.994 33
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表 4 模拟工况
Table 4 Simulation conditions
工况 输送带速度/（m·s−1） 环境温度/℃ 巷道风速/（m·s−1） 托辊内煤粉
积存比例/%5 2.0 15 1 25，50，75，100 6 2.0 15 2 25，50，75，100 7 3.5 15 1 25，50，75，100 8 3.5 20 1 25，50，75，100
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