液氧固碳闭式循环柴油机着火机理研究

Study on the Ignition Mechanism of Closed Cycle Diesel Engine System with Liquid Oxygen Carbon Sequestration

为研究液氧固碳闭式循环柴油机的着火特性,提出柴油表征燃料正庚烷(n-C7H16)在O_(2)/CO_(2)环境中的化学反应机理(简称COCD机理)。该机理考虑CO_(2)的两种效应(热效应和第三体效应)对正庚烷着火过程的影响,计算多个工况下的着火延迟时间,采用定容燃烧弹(Constant volume combustion chamber,CVCC)可视化试验平台模拟液氧固碳闭式循环柴油机的真实工况并进行试验,对COCD机理的计算结果进行验证。研究CO_(2)的两种效应对着火延迟时间的影响,采用敏感性分析和产率分析的方法研究不同工况下着火过程中的关键反应。结果表明,COCD机理的预测值在61%O_(2)/39%CO_(2)、53%O_(2)/47%CO_(2)、45%O_(2)/55%CO_(2)以及40%O_(2)/60%CO_(2)的工况下的最大误差为7.5%,最小误差为1.3%。在O_(2)/CO_(2)环境中,反应C_(7)H_(14)O_(2)H+O_(2)→C_(7)H_(14)O_(2)HO_(2)和H2O_(2)+M→2OH分别是影响正庚烷第一阶段和第二阶段放热的主要反应。

In order to study the ignition characteristics of liquid oxygen solid carbon closed cycle diesel engine,a diesel surrogate fuel n-heptane(n-C7H16)mechanism(COCD mechanism)in the O_(2)/CO_(2)atmospheres is proposed.The mechanism considers two effects of CO_(2)(thermal third body effects)on n-heptane ignition process,which are employed to calculate the ignition delay time under multiple working conditions.The constant volume combustion chamber(CVCC)visual test platform are established to simulate the real working conditions of the liquid oxygen solid carbon closed cycle diesel engine for relevant experiment,which is also used for verifying the COCD mechanism.The two effects of CO_(2)on the ignition delay time are compared and the key reactions in the ignition process under different conditions are studied by sensitivity analysis and rate of production(ROP)analysis.The maximum and minimum errors of the COCD mechanism predictions are 7.5%and 1.3%under the working conditions of 61%O_(2)/39%CO_(2),53%O_(2)/47%CO_(2),45%O_(2)/55%CO_(2)and 40%O_(2)/60%CO_(2).In the O_(2)/CO_(2)atmospheres,the reaction C_(7)H_(14)O_(2)H+O_(2)→C_(7)H_(14)O_(2)HO_(2)and H_(2)O+M→2OH are the main reactions that affect the n-heptane first and second stages heat release,respectively.