二甲基醚/天然气双燃料均质压燃的燃烧特性

应用零维热力学模型和化学反应动力学模型计算并分析了二甲基醚(DME)／天然气(CNG)双燃料均质压燃(HCCI)运行工况范围，计算与试验结果相吻合．采用DME／CNG双燃料方式可以有效地扩展HCCI的运行工况范围，发动机转速为1400r／min，最大平均有效压力可达O．52MPa．在一台单缸直喷式柴油机上进行了DME／CNG双燃料HCCI燃烧过程的试验研究，结果表明，DME／CNG双燃料燃烧过程表现出明显的两阶段放热过程，随着CNG浓度增大，缸内最大爆发压力增大，燃烧始点略有推迟，燃烧第二放热峰值增大．而DME浓度对燃烧过程的影响主要通过影响第一阶段放热过程，进而影响第二阶段放热，随着DME浓度加大，第一放热峰值增大，燃烧始点提前，导致第二放热峰值增大，缸内最大爆发压力增大，主燃期缩短，当DME浓度太高时，发动机将出现爆震．

Study on the HCCI Combustion Process of DME/CNG Dual Fuel

This paper reports the investigation of the homogeneous charge compression ignition (HCCI) combustion on a test engine dual-fueled by dimethyl ether (DME) with a high-cetane number and compressed natural gas (CNG) with a high-octane number. This study is based on both theoretical modeling and experimental research.In the modeling a zero-dimensional thermodynamic model is coupled with a detailed chemical kinetic model to calculate the operating range of this HCCI engine. The experiment was carried out on a single-cylinder direct-injection diesel engine. The calculated results agree well with the experimental results. The results show that adjusting the proportions of DME and CNG is an effective technique for controlling HCCI combustion and extending the HCCI operating range. The maximum brake mean effective pressure (BMEP) for DME/CNG dual fueled HCCI operation is 0.52 MPa at a speed of 1 400 r/min. It is found that the HCCI combustion process of DME/CNG is characterized by a two-stage heat release process. As CNG concentration increases, the peak cylinder pressure gets higher,the ignition delay becomes slightly longer, and the peak heat release rate in the second stage goes up. On the other hand, a higher DME concentration leads to a higher peak cylinder pressure, shorter ignition delay, and an increased peak heat release rate in the first stage. However, when DME concentration increases to a certain level, the engine will knock.