模拟发动机工况下二甲醚喷雾燃烧实验及仿真研究

在定容弹内模拟发动机实机工况的高温、高压环境(920K,6.0 MPa),借助专用共轨系统产生100 MPa压力进行二甲醚喷射实验,通过定容弹内混合气体中的氧气浓度来控制二甲醚的燃烧,使用高速摄像机观察并记录二甲醚在超临界和亚临界条件下的喷雾及燃烧形态。基于实验结果,采用FORTE软件开发二甲醚喷雾燃烧仿真模型,其中耦合了二甲醚氧化还原反应动力学模型。实验和仿真结果表明,二甲醚在两种喷射条件下的喷雾贯穿距离无明显差异,而超临界条件下的液相贯穿距离较短;与亚临界条件相比,超临界条件下二甲醚喷雾着火时刻略早,火焰举升距较小,并且燃烧时释放出了更多的热量;仿真模型较好地拟合了二甲醚喷雾燃烧实验结果。

Experiment and simulation of dimethyl ether spray combustion in engine-like conditions

Dimethyl ether (DME) spray at injection pressure up to 100 MPa produced by a common rail DME injection system was tested in a constant volume vessel, whose ambient temperature and pressure were 920 K and 6.0 MPa simulating the real engine. The combustion of DME was controlled by oxygen concentration of the mixture gas in the constant volume vessel. The patterns of DME spray combustion in supercritical and subcritical conditions were observed and recorded by a high-speed video camera. On the basis of experiments, FORTE software was used to establish DME spray combustion numerical model coupled with the chemical kinetic model for the oxidation of DME. Experiment and simulation results show that there is no significant difference in DME spray tip penetration length in the two injection conditions, but liquid phase penetration length of DME spray in supercritical condition is shorter than that in subcritical condition. Compared with subcritical spray, supercritical DME spray has slightly earlier ignition time and shorter flame lift-off length, and releases more combustion heat. The simulation model shows a reasonable agreement with the experiments.