燃料改性与进气预处理降低甲醇-柴油PAHs的数值模拟

Numerical Simulation of Reducing Methanol-diesel PAHs through Fuel Modification and Intake Pretreatment

通过构建由228种组分和1 584个基元反应组成的甲醇-柴油PAHs计算模型,研究了燃料改性方案、空气稀释比以及过量空气系数、初始温度,初始压力对甲醇-柴油PAHs的影响。结果表明,甲醇-柴油PAHs模型能准确预测甲醇-柴油燃烧过程中的反应温度,甲醇摩尔分数,反应中间产物CO,CO2,O2浓度随时间的变化规律和着火延迟。通过进气预处理,降低空气稀释因子可以有效降低甲醇-柴油燃烧过程中PAHs的浓度;采用氢气、甲烷作为燃料添加剂进行燃料改性可以有效改善油气混合,提高火焰温度和火焰的绝热燃烧速度,有利于PAHs的氧化分解。提高过量空气系数可以增加反应中间产物H和OH自由基的数量,降低芳香烃各组分的浓度;提高反应的初始温度,降低反应初始压力,使得燃烧化学反应始点提前,有利于降低PAHs的浓度。

Based on the numerical model of methanol‐diesel PAHs composed of 228 composition and 1 584 elementary reac‐tions ,the influences of fuel modification scheme ,air dilution ratio ,excess air coefficient ,initial temperature and pressure on methanol‐diesel PAHs were studied .The results show that the model can predict the reaction temperature of methanol‐diesel combustion ,the mole fraction of methanol ,CO ,CO2 and O2 concentration variation with time and the ignition delay time accu‐rately .Through the intake pretreatment ,the air dilution factor can be decreased so as to reduce PAH formation effectively dur‐ing the methanol‐diesel combustion .Taking hydrogen and methane as fuel additive ,the fuel modification is realized so as to im‐prove the air‐fuel mixing ,increase the flame temperature and adiabatic combustion velocity and facilitate the oxidation and de‐composition of PAHs .Increasing the excess air coefficient can increase the quantity of H and OH radicals intermediate products and decrease the concentration of each component for PAHs .The increase of initial reaction temperature and the decrease of ini‐tial reaction pressure advance the starting point of chemical reaction ,which decrease the concentration of PAHs .