直喷式柴油机起动过程燃烧分析

Analysis of Direct Injection Diesel Engine Combustion During Start

为了快速、定性分析柴油机起动过程中的燃烧状态,在直喷式柴油机上进行冷机与热机起动过程实验,提出用瞬时转速和示功图对柴油机起动进行燃烧分析的方法．实验结果表明,冷机起动过程中有失火现象,用瞬时转速可以判断着火首循环和失火循环．根据示功图形状及燃烧状态,定义了4种燃烧状态以及相对应的4种典型示功图形式,将起动过程划分为4个阶段．热机起动初始期和过渡期很短,而冷机起动有明显的4个阶段．不完全燃烧或失火是柴油机起动过程、燃烧过程控制优化的重点,多出现在起动初始期和过渡期．

In order to clearly analyze and define the combustion state of diesel engine during start, cold and warm start experiments were conducted on a direct injection diesel engine. An estimation method based on transient crank speed and cylinder pressure diagram was put forward to study diesel engine start combustion. It is found that there are misfires during cold start; the first ignition cycle and misfire cycle can be judged by crankshaft transient speed variation. Four different combustion states are defined, with four corresponding cyhnder pressure diagram types. From crank to steady idle speeds it is divided into four phases. The preliminary phase and transitional phase during warm start are short. The four phases are distinct during cold start. And it is important to optimize combustion during preliminary phase and transitional phase to improve diesel engine cold start performance, because incomplete combustion and misfires appear in these phases.