喷水对氩气循环天然气发动机爆震及热效率的影响分析

基于一台汽油/天然气两用燃料的涡轮增压三缸发动机，建立 GT-Power仿真模型，研究喷水对准氩气动力循环发动机工作过程的影响。结果表明，在低负荷工况下，喷水后缸内的温度和压力都下降；增大水气比 （水和甲烷的质量比） 和推迟点火则传热损失减少但排气损失增加，存在热效率提升的较宽水气比范围和最优的水气比，推迟点火时刻和喷水对于爆震有良好的抑制作用。在大负荷爆震工况下，喷水能够显著抑制爆震，提前点火时刻可以得到更优的燃烧效率，喷水可使制动平均有效压力 （Brake Mean Effective Pressure，BMEP） 为0.6 MPa时指示热效率提高0.2%、有效热效 率提高0.1%，0.8 MPa工况的指示热效率提高0.4%、有效热效率提高0.2%，1.2 MPa工况的指示热效率提高1.2%、有效热效率提高0.8% （水气比为1工况相对于水气比为0.4工况）。结合低负荷工况和高负荷工况的表现，发现喷水能有效抑制发动机的爆震，并能提升发动机的热效率。

Effect of Water Injection on Knock and Thermal Efficiency of Argon Power Cycle Natural Gas Engine

A GT-power simulation model is established for a turbocharged three-cylinders engine using gasoline/natural gas to study the influence of water injection on the working process of the quasi argon power cycle engine. The results show that under low load, the temperature and pressure in the cylinder decrease after water injection. Increasing the water-gas ratio (the mass ratio of water to methane) and delaying ignition reduce heat transfer loss and increase exhaust loss. There are a wide range of water-gas ratio and the optimal water-gas ratio with the improved thermal efficiency. The retarded spark timing and water injection lead to knock suppression. When engine knock occurs during heavy-load conditions, water injection can significantly inhibit knock. In addition, spark advance results in better combustion efficiency.Other important results are listed as follows: water injection can increase the indicated thermal efficiency by 0.2% and the brake thermal efficiency by 0.1% when BMEP is 0.6 MPa; the indicated thermal efficiency is increased by 0.4% and the brake thermal efficiency is increased by 0.2% under the condition of 0.8 MPa; the indicated thermal efficiency is increased by 1.2% and the brake thermal efficiency is increased by 0.8% under the condition of 1.2 MPa. Considering the performance under both low-and high-load conditions, we have found that water injection can effectively inhibit engine knock and improve the thermal efficiency of the engine.