IMECH-IR  > 高温气体动力学国家重点实验室
铝粉点火延时及燃烧时间的激波管实验与动力学模拟
英文题名Shock Tube Experiments and Kinetic Simulation of Ignition Delay and Burn Time of Aluminum Powders
熊壮
导师俞鸿儒 ; 王苏
2018-11-27
学位授予单位中国科学院大学
学位授予地点北京
培养单位中国科学院力学研究所
学位专业流体力学
关键词铝粉,点火延时,燃烧时间,激波管,动力学模拟
摘要铝粉因其高燃烧值的特点而被广泛用作高能推进剂的金属添加剂。为了深入理解高能推进剂的燃烧机理,铝粉点火和燃烧特性是重要的研究内容之一。在碳氢燃料中添加金属粉末等含能材料以提高燃料热值达到增大发动机推力的途径也受到关注。铝粉还可以在碳氢燃料燃烧产物H2O和CO2进行二次燃烧释放大量热量,铝粉与碳氢燃料燃烧产物H2O和CO2二次燃烧生成更稳定的Al2O3对碳氢燃料燃烧产物离解还起到了催化复合的作用。 在碳氢燃料中添加铝粉后,混合燃料的点火和燃烧性质与铝粉粒径大小、环境温度和压力都密切相关。目前纳米铝粉已得到广泛应用。随着铝粉粒径从微米减小到纳米,铝粉燃烧过程将从扩散控制过渡到反应动力学控制。因此,研究不同粒径铝粉的点火和燃烧特性,对发动机燃烧室中燃烧机理的建立和燃烧室设计及优化具有重要意义,也为建立及验证铝粉点火及燃烧化学动力学机理提供重要的基础数据,同时也为探索通过在碳氢燃料中添加铝粉实现二次燃烧以提高吸气式冲压发动机效率的途径提供基础。 本文以不同粒径尺度的铝粉在多种氧化剂条件下(O2、H2O、CO2)的点火延时和燃烧时间以及铝粉与碳氢燃料点火的相互影响为研究内容,通过激波管实验获得了铝粉点火延时和燃烧时间与环境温度、压力、氧化剂种类和浓度、颗粒粒径的关系。本文特别关注铝粉燃烧机理从扩散控制到反应动力学控制转变时,铝粉点火延时和燃烧时间与各种影响因素的依赖关系。同时,本文还将不同粒径的铝粉分别加入到H2和C2H4两种典型的燃料中,通过激波管实验考察了铝粉与H2和C2H4之间的相互作用。在激波管实验的基础上,本文利用现有的铝粉化学反应动力学机理对铝粉燃烧时间进行了动力学模拟。本文获得的主要结果如下: 1)温度在2320-2470 K之间、压力8atm时,6种粒径(50 nm、200 nm、1μm、10 μm、20 μm、50 μm)铝粉的点火延时和燃烧时间随着粒径的变化关系: τ_ign=236.2D^(0.45 ) (μs) τ_burn=1096.6D^0.23 (μs) D是铝粉粒径,单位μm。 2)在温度1400-3300 K、压力2 -13 atm和氧化剂浓度20%-80%的条件下,200 nm铝粉分别在三种氧化剂(O2、H2O、CO2)中的点火延时和燃烧时间与温度、压力和氧化剂浓度的拟合关系; τ_ign=10.6[〖X_(O_2 )]〗^(-0.93) P^(-0.95) exp⁡(26710/RT) τ_ign=16.7[〖X_(〖CO〗_2 )]〗^(-0.6) P^(-0.7) exp⁡(32158/RT) τ_ign=94.1[〖X_(H_2 O)]〗^(-0.99) P^(-0.41) exp⁡(56528/RT) τ_burn=12.3[〖X_(O_2 )]〗^(-0.43) P^(-0.54) exp⁡(21550/RT) τ_burn=42.8[〖X_(〖CO〗_2 )]〗^(-0.71) P^(-0.44) exp⁡(36981/RT) τ_burn=73.1[〖X_(H_2 O)]〗^(-0.69) P^(-0.28) exp⁡(39666/RT) τign、τburn分别为铝粉的点火延时和燃烧时间,单位均为μs; XO2、XCO2、XH2O分别为三种氧化剂的初始摩尔分数,T为环境温度,单位是K;P为环境压力,单位为MPa。 3)在温度2100-3000 K、压力2-13 atm和氧化剂浓度20%-80%的条件下,10 μm铝粉的点火延时和燃烧时间与温度、压力和氧化剂浓度的拟合关系; τ_ign=789.5/(P^0.32 T^0.31 (X_(O_2 )+0.64X_H2O+0.51X_CO2 ) ) τ_burn=1572.3/(P^0.34 T^0.29 (X_(O_2 )+0.67X_H2O+0.47X_CO2 ) ) τign、τburn分别为铝粉的点火延时和燃烧时间,单位均为μs; XO2、XCO2、XH2O分别为三种氧化剂的初始摩尔分数,T为环境温度,单位是K;P为环境压力,单位为MPa,R为气体常数,单位J•mol-1•K-1; 4)200 nm铝粉在O2、CO2、H2O三种氧化剂中的点火和燃烧过程均处在动力学控制阶段,其点火延时和燃烧时间随着温度、压力和氧化剂浓度的改变有明显的变化; 10 μm铝粉在O2中的点火和燃烧过程仍处于动力学控制,10 μm铝粉在CO2和H2O中的点火和燃烧过程逐渐转为扩散控制的过渡阶段; 5)纳米铝粉燃烧时间的动力学模拟结果与实验结果在随温度和氧化剂浓度的变化趋势上基本吻合,两者在数值上存在差异; 6)在温度1276 K、压力1.3 atm的条件下,1 μm铝粉能够在当量比为1、稀释度为70%的氢气中发生点火;在温度1277 K、压力1.2 atm的条件下,10 μm铝粉能够在当量比为1、稀释度为88%的乙烯中发生点火;随着铝粉粒径的减小可以在更高的稀释度条件下点火;在本文的实验条件范围内,铝粉在H2或C2H4环境中发生点火时,几乎与H2或C2H4同时发生点火,没有观察到铝粉滞后H2或C2H4点火的情况;同时观测到铝粉的加入促进了氢气和乙烯的点火,缩短了点火延时。
英文摘要Aluminum powders are widely used as a metal additive in various high-energy propellants because of its high combustion enthalpy. In order to understand the combustion mechanism of high-energy propellants, the ignition and combustion characteristics of aluminum powder are two of the important factors. It has been concerned to increase fuel heat value to improve engine thrust performance by adding metal powder and other energetic materials to hydrocarbon fuels. Aluminum powder can also release a large amount of heat through secondary combustion with hydrocarbon fuel combustion products H2O and CO2. Aluminum powder produces more stable Al2O3 by secondary combustion, which also plays a catalytic recombination role for the decomposition of hydrocarbon fuel combustion products. When aluminum powders are added to hydrocarbon fuels, the ignition and combustion properties of the mixtures are closely related to aluminum particle size, ambient temperature and pressure. At present, nano-aluminum powders have been widely applied. As the particle size of aluminum powder decreases from micron to nanometer, the combustion control process of aluminum powder will exhibit a transition from diffusion limit to reaction kinetic limit. Therefore, the study of ignition delay and burn time of aluminum powders with various particle sizes is of great significance to the establishment of combustion mechanism in engine combustor and the design and optimization of combustor, it also provides important basic data for establishing and validating the aluminum powder ignition and combustion chemical kinetic mechanisms. At the same time, the present study will provide a basis for exploring the new approach to increase engine thrust in a scramjet. The ignition delay and burn time of aluminum powders with various particle sizes under various oxidant environments (O2, H2O, and CO2) and the combustion interaction between aluminum powder and hydrocarbon fuel were studied in this dissertation. The dependence of the ignition delay and burn time of aluminum powders with the environmental temperature, pressure, type and concentration of oxidant, as well as aluminum particle size was systematically obtained in shock tube experiments. The special attention was paid to the dependence of ignition delay and burn time of aluminum powders with various factors in the transition regime from the diffusion limit to kinetic limit in combustion. Furthermore, aluminum powders with various particle sizes were added into two typical fuels H2 and C2H4 to investigate the combustion interaction between aluminumpowder and fuel. Based on the shock tube experiments, the existing chemical kinetic mechanisms of aluminum powder were applied to kinetically simulate the burn time of aluminum powders.The main conclusions are as follow: 1) The relations of the ignition delay time and burn time of aluminum powders with particle size (50 nm, 200 nm, 1 μm, 10 μm, 20 μm, 50 μm) were obtained at the temperatures from 2320 to 2470 K and the pressure of 8atm as follow: τ_ign=236.2D^0.45 (μs) τ_burn=1096.6D^0.23 (μs) D is the aluminum powder size in μm 2) The relations of the ignition delay time and burn time of 200 nm aluminum powders with temperature, pressure and oxidant concentration were obtained at the temperatures from 1400 to 3200 K, the pressures from 2 to 13 atm, and oxidant concentrations from 20% to 80% as follow: τ_ign=10.6[〖X_(O_2 )]〗^(-0.93) P^(-0.95) exp⁡(26710/RT) τ_ign=16.7[〖X_(〖CO〗_2 )]〗^(-0.6) P^(-0.7) exp⁡(32158/RT) τ_ign=94.1[〖X_(H_2 O)]〗^(-0.99) P^(-0.41) exp⁡(56528/RT) τ_burn=12.3[〖X_(O_2 )]〗^(-0.43) P^(-0.54) exp⁡(21550/RT) τ_burn=42.8[〖X_(〖CO〗_2 )]〗^(-0.71) P^(-0.44) exp⁡(36981/RT) τ_burn=73.1[〖X_(H_2 O)]〗^(-0.69) P^(-0.28) exp⁡(39666/RT) where the ignition delay time τign and the burn time τburn are in μs, T is the temperature in Kelvin, XO2、XCO2、XH2O are the mole fraction of O2、CO2、H2O in Ar, and P is the pressure in MPa, R is gas constant in J•mol-1•K-1. 3)The relations of the ignition delay and burn time of 10 μm aluminum powders with temperature, pressure and oxidant concentration were obtained at the temperatures from 2100 to 3000 K, the pressure from 2 to 13 atm, and the oxidant concentrations from 20% to 80% as follow: τ_ign=789.5/(P^0.32 T^0.31 (X_(O_2 )+0.64X_H2O+0.51X_CO2 ) ) τ_burn=1572.3/(P^0.34 T^0.29 (X_(O_2 )+0.67X_H2O+0.47X_CO2 ) ) where the ignition delay time τign and the burn time τburn are in μs, T is the temperature in Kelvin, XO2、XCO2、XH2O are the mole fraction of O2、CO2、H2O in Ar, and P is the pressure in MPa. 4) The ignition and combustion of 200 nm aluminum powders in the O2, CO2 and H2O are kinetically controlled. The ignition and combustion of 10μm aluminum powders in the O2 are kinetically controlled. The ignition and combustion of 10 μm aluminum powders in the CO2 and H2O gradually transit from kinetically controlled to diffusion-controlled. 5) The kinetic simulation results of burn times of 200 nm aluminum powders show a good consistency with the experimental results on the change trend with temperature, pressure and oxidant concentration, but there are some numerical differences between the simulation and the experimental results. 6) 1μm aluminum powders can ignite in H2 with 70% dilution at 1276 K and 1.3atm. 10μm aluminum powders can ignite in C2H4 with 88% dilution at 1277 K and 1.2 atm. As the particle size decreases, the aluminum powders can ignite more easily in hydrogen and ethylene with the higher dilution. The aluminum powders ignition and H2 or C2H4 ignition take place simultaneously under present experimental conditions. The ignition of aluminum powder delayed to H2 or C2H4 was not observed. The addition of aluminum powders can shorten the ignition delay of hydrogen and ethylene.
语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/78046
专题高温气体动力学国家重点实验室
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熊壮. 铝粉点火延时及燃烧时间的激波管实验与动力学模拟[D]. 北京. 中国科学院大学,2018.
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