Mg粉/CO2两相湍流燃烧特性研究

In order to reduce the cost, the In Situ Resource Utilization(ISRU) has been paid more and more attention by the countries in the exploration of Mars. The rich CO2 on Mars has become the preferred target of ISRU. Magnesium powder and CO2 as propellant used in powder rocket motor is the best feasible solution to realize ISRU in the Mars exploration. At present, many scholars have carried on the related research on ignition and combustion of the static single particle or particles of magnesium in the carbon dioxide environment. The phenomenon and mechanism of particle ignition and combustion are studied, and the combustion model of single particle is developed. However, the combustion reaction of magnesium powder and CO2 as propellant is two phase turbulent combustion. In order to realize the efficient combustion of powder Mg and CO2 in the powder rocket engine, the turbulent combustion characteristics must be understood well. Therefore, in this project, propagation characteristics of the Mg powder/CO2 laminar burning flame will be studied experimentally. On this basis, considered phenomenon involved in the turbulent combustion process of Mg and CO2, turbulent combustion model will be established. The turbulent combustion flame structure characteristics and the influence of turbulent intensity, particle size, ambient temperature and pressure on the flow field and flame structure and combustion rate will be researched by numerical simulation and experiment, which results can be as a reference to the designing powder rocket engine of magnesium particles and carbon dioxide.

为了降低成本,火星探索中原位资源利用(ISRU)已受到各国家的关注，火星上丰富的CO2成为ISRU首选对象，Mg粉/CO2作为粉末火箭发动机推进剂是实现火星探索中ISRU可行的最佳方案。目前，许多学者对静态的单个Mg颗粒或者粒子群在CO2环境中点火燃烧过程的现象及机理进行了相关研究，建立了单个颗粒的燃烧模型。然而，Mg粉和CO2作为推进剂在发动机中燃烧反应属于两相湍流燃烧，为实现Mg粉/CO2在粉末火箭发动机中高效燃烧，必须充分了解Mg粉/CO2湍流燃烧特性。因此，本项目拟应用实验方法研究Mg粉/CO2层流燃烧火焰传播特性，在此基础上，考虑Mg粉/CO2燃烧过程中所涉及的现象建立其湍流燃烧模型，应用数值模拟与实验相结合方法研究Mg粉/CO2湍流燃烧火焰结构特征，以及湍流强度、颗粒尺寸、环境温度和压强对颗粒周围流场和多样性火焰结构及燃烧速率的影响规律，为Mg粉/CO2粉末火箭发动机设计提供参考。

为了要实现Mg粉/ CO2二元推进剂为原料的动力装置在火星探测中最大限度地进行原位资源利用，本研究开展了Mg粉/CO2的点火及燃烧特性研究。基于辐射图像比色法建立彩色CCD测温系统，组建了Mg/CO2燃烧火焰温度场测量实验系统，通过控制变量，设计实验工况，研究了Mg粉颗粒粒径、预混气流雷诺数、CO2/Mg氧燃比对Mg/CO2燃烧火焰温度场的影响规律：稳定燃烧火焰温度在2500K-2900K之间，且随着颗粒直径、雷诺数Re和氧燃比的增大，火焰温度呈现下降趋势。基于准稳态和塑性强度理论，考虑固体产物在内外氧化膜颗粒表面堆积，分别建立了Mg单个颗粒与粒子群在CO2点火燃烧模型，基于实验结果验证了该模型的准确性，并应用数值模型研究了镁粒子与二氧化碳的着火特性，结果表明，颗粒的着火温度随环境压力和温度的升高而升高，粒度和氧化剂浓度对着火温度影响不大；着火延迟时间随粒径的增大近似抛物线增大，随环境压力的增大近似成反比减小，随环境温度的升高近似抛物线减小，随氧化剂浓度的增大近似直线减小。对于颗粒粒径、预混气流雷诺数和CO2/Mg氧燃比对动态Mg粉/CO2点火燃烧的影响，结果表明，粒径在5um-20um中，粒径为5um时，平均点火时间最短；粒径为10um时，平均温度及燃烧效率最高；粒径和CO2/Mg氧燃比相同，雷诺数为1500时，平均温度最高，平均点火时间最短；雷诺数为2500时，燃烧效率最高；粒径和雷诺数相同，CO2/Mg氧燃比为1.0时，燃烧效率最高；CO2/Mg氧燃比为1.5时，平均温度最高，平均点火时间最短。研究结果可为Mg粉/CO2粉末发动机设计提供参考。