基于喷射策略的氨柴双燃料发动机燃烧和排放试验研究
Experimental Study on Combustion and Emissions in an Ammonia-Diesel Dual-Fuel Engine Based on Injection Strategy
关键词:氨-柴双燃料  燃烧  喷射策略  柴油双喷策略
Key Words:Ammonia-diesel dual-fuel  Combustion, Injection strategy, Dual diesel injection strategy
基金项目:
作者单位邮编
陈清楚 School of Vehicle and Mobility,Tsinghua University 100084
蔡开源 清华大学车辆与运载学院 
刘奕 清华大学车辆与运载学院 
齐运亮 清华大学车辆与运载学院 
陈虎 清华大学车辆与运载学院 
王志* 清华大学车辆与运载学院 100084
摘要:在一台重型柴油发动机试验平台的基础上改造氨柴双燃料发动机，加装了一套电控喷氨系统，采用氨气进气道喷射、柴油缸内直喷方式，通过柴油喷射策略的变化，在发动机1200r/min的中高负荷，50%氨能占比的工况下，开展了氨柴双燃料的燃烧和排放特性优化研究。试验结果表明：氨柴双燃料燃烧时，由于氨燃料燃烧速度慢、起燃温度高等特性，柴油原机的上止点附近单次喷射策略，使得氨燃烧与柴油燃烧不同步，燃烧放热率呈现“双峰”曲线，氨燃烧效率较低。采用柴油双喷策略，通过提前柴油预喷时刻，可推迟柴油起燃时间，活化活塞凹坑外的氨燃料，促使柴油和氨燃烧趋于同步，将“双峰”放热曲线转变成“单峰”放热曲线，从而加快燃烧速度，缩短燃烧持续期，减少未燃氨排放，提升氨燃烧效率。但过度提前预喷时刻会造成柴油撞壁，不利于发动机指示热效率。
Abstract:A dual-fuel engine using ammonia and diesel was modified, based on a heavy-duty diesel engine experimental platform. A set of electronic control ammonia injection systems was installed, with ammonia injected into the intake manifold and diesel directly injected into the diesel cylinders. By varying the diesel injection strategy, combustion and emission char-acteristics of the ammonia-diesel dual-fuel engine was optimized under 1200r/min medium loads with a 50% ammonia energy ratio. Experimental results showed that the slow combustion rate and high ignition temperature of ammonia fuel lead to an asynchronous combustion with diesel in the vicinity of the top dead center of the diesel engine's original injec-tion strategy, results in a "double-peak" heat release curve, leading to lower efficiency in ammonia combustion. By adopting a dual injection strategy for diesel, the ignition timing of diesel can be delayed by advancing the diesel pilot injection timing, which activates the ammonia fuel outside the piston cavity, promoting synchronization between diesel and ammonia combustion. The "double-peak" heat release curve is transformed into a "single-peak" curve, accelerating the combustion rate, shortening the combustion duration, reducing unburned ammonia emissions, and enhancing ammo-nia combustion efficiency. However, excessive advancement of the pilot injection timing may cause diesel wall im-pingement, which is detrimental to the indicated thermal efficiency.
查看/发表评论