Key composition of aviation alternative fuel on ignition performance at low temperature
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摘要:
液体燃料低温条件下挥发的燃油组分对于点火启动有显著影响。通过对航空煤油RP-3和煤基费托F-T燃料低温条件气相组分分析,得到了-40℃到15℃燃料挥发组分及含量分布规律,确定低温条件发动机点火关键物质并进行点火边界测试及分析。通过加入轻烃物质煤基费托燃料点火性能有显著提高作用,其改善顺序为环烷烃最优,其次是支链烷烃,直链烷烃。对航空替代燃料应用于发动机低温冷启动及高空再点火过程有一定指导意义。
Abstract:Liquid fuel volatile compositions play an important role for ignition at low temperatures. The composition distribution of aviation kerosene RP-3 and coal-based Fischev-Tropsch F-T fuel in the vapor phase under low temperatures were analyzed in this research. The volatile components and content distribution of the fuel from -40℃ to 15℃ were obtained, and the key materials for engine ignition in low temperature conditions were determined and the ignition boundary test and analysis were carried out. The addition of light hydrocarbons significantly improves the ignition performance of coal-based Fischer-Tropsch fuel. Cycloalkanes are preferential, which are followed by branched alkanes and n-alkanes. It is of significance for the application of aviation alternative fuels in engine cold start and high-altitude relight process.
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Key words:
- alternative fuel /
- light hydrocarbons /
- low temperature ignition /
- vapor pressure /
- liquid fuel
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表 1 航空煤油RP-3和煤基费托F-T理化性质
Table 1. Physicocemical properties of aviation kerosene RP-3 and coal-based F-T
测试燃料 密度/(kg·m-3) 闪点/℃ 冰点/℃ 20℃黏度/(mm2·s-1) 热值/(MJ·kg-1) RP-3 788 43.0 -47 1.72 42.8 F-T 758 55.5 -28 2.22 47.4 表 2 航空煤油RP-3和煤基费托F-T液相组分分布
Table 2. Distribution of components in liquid phase of aviation kerosene RP-3 and coal-based F-T
% 碳数 RP-3 F-T 直链烷烃 支链烷烃 环烷烃 芳香烃 烯烃和萘 直链烷烃 支链烷烃 7 0.18 0.21 1.31 3.06 0 0 0 8 1.01 0.84 4.75 2.02 0 0.43 0 9 3.53 1.96 3.55 7.00 0 9.46 2.21 10 5.75 6.53 2.51 5.49 1.26 11.33 5.32 11 6.73 9.56 0.38 0.45 2.24 12.18 4.26 12 6.25 5.41 0 0 0 11.42 3.55 13 4.47 4.63 1.56 0 0 10.29 2.33 14 2.39 1.89 0 0 0 8.41 1.30 15 0.88 0.17 0 0 0 6.30 0 16 0.17 0.90 0 0 0 4.55 0 17 0 0.67 0 0 0 3.05 0 ≥18 0 0 0 0 0.27 3.61 0 总计 31.36 32.77 14.06 18.02 3.77 81.03 18.97 表 3 15℃条件下航空煤油RP-3与煤基费托F-T气相组分分布
Table 3. Distribution of components in gas phase of aviation kerosene RP-3 and coal-based F-T at 15℃
% 碳数 RP-3 F-T 6 8.36 0 7 28.32 2.13 8 23.27 10.21 9 27.39 63.96 10 10.89 21.87 11 0.42 1.83 表 4 直链烷烃蒸气压随温度变化
Table 4. Variation of vapor pressure of n-alkanes with temperature
kPa 正构烷烃 25℃[18] 25℃ 15℃ -10℃ -20℃ -30℃ C6 20.2 2.337 12.921 3.426 1.834 0.920 C7 6.1 6.077 3.598 0.776 0.377 0.170 C8 1.9 1.844 1.031 0.192 0.088 0.037 C9 0.6 0.594 0.313 0.049 0.021 0.008 C10 - 0.191 0.095 0.012 0.005 0.002 表 5 37.8℃时F-T添加5%C7烃类物质油气比
Table 5. Fuel-to-air ratio of F-T added with 5% C7 hydrocarbons at 37.8℃
试样 密度/(g·cm-3) 供气压力/kPa 供气质量/g 供油质量/g 油气比 降低程度/% RP-3 0.788 0 27.18 1.471 9 0.394 0 0.267 7 F-T 0.758 0 22.25 1.204 6 0.379 0 0.314 6 0 FT+5%甲基环己烷 0.758 8 29.75 1.611 1 0.379 4 0.235 5 25.15 F-T+5%2-甲基己烷 0.754 1 28.65 1.551 2 0.377 0 0.243 0 22.75 F-T+5%正庚烷 0.754 3 24.22 1.311 6 0.377 2 0.287 5 8.60 表 6 RP-3和F-T添加不同比例C7理化性质及油气比
Table 6. Physical properties and fuel-to-air ratio of RP-3 and F-T added with different proportions of C7
试样 闪点/℃ 蒸气压/kPa 热值(MJ·kg-1) 37.8℃油气比 RP-3 43.0 0.6 42.81 0.267 7 RP-3+2%甲基环己烷 39.0 1.0 42.81 0.237 4 RP-3+3%正庚烷 37.5 1.1 42.85 0.244 8 RP-3+1.5%2-甲基己烷 37.5 0.9 42.83 0.258 1 F-T 55.5 0.3 47.40 0.314 6 F-T+5.5%甲基环己烷 37.5 1.2 47.18 0.232 6 F-T+7.5%正庚烷 38.5 1.6 47.19 0.238 7 F-T+3%2-甲基己烷 39.0 1.5 47.31 0.254 4 表 7 添加C7碳氢燃料可燃蒸汽分压与燃烧下限
Table 7. Flammable vapor partial pressure and flammable lower limit of hydrocarbons added with C7
试样 燃油蒸汽分压(总压30 kPa) 分压占比/% 燃烧下限/%(30 kPa修正值) 煤基费托F-T 0.22 0.733 3 0.905 6 F-T+5%甲基环己烷 0.31 1.033 3 1.031 8 F-T+5%2-甲基己烷 0.32 1.066 7 1.107 1 F-T+5%正庚烷 0.30 1.000 0 1.148 3 -
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