【作者】 张强；

【导师】 隆武强；

【作者基本信息】 大连理工大学 ， 动力机械及工程， 2015， 博士

【摘要】 预混合压燃发动机综合了柴油机和汽油机的优点,可实现高效、NOx和PM的超低排放,而着火相位控制一直是预混合压燃实用化的难点。为了实现直接控制柴油预混合气压缩着火相位,本文提出并开发了射流控制压缩着火(Jet Controlled Compression Ignition, JCCI)燃烧系统,利用点火室内燃烧产生的射流触发缸内柴油预混合气着火。开发了基于CF186FA单缸柴油机的JCCI原理样机,确定了JCCI燃烧系统点火室的设计准则,并以此设计了点火室及气体燃料供给系统,完成了点火室在缸盖上的布置。将活塞顶形状由深ω形改造为适宜于预混合燃烧的浅盆形,并降低几何压缩比。采用高扰动喷油嘴结合早喷策略,用于形成分布均匀的柴油预混合气。基于CompatRIO平台搭建了JCCI发动机测控系统,编写了基于曲轴转角的喷气阀控制与点火控制程序,运用状态机和生产-消费的结合实现了喷气、点火与缸压采集的相位同步控制与测量,并采用Lab VIEW和Matlab混合编程方法开发了离线燃烧分析系统。JCCI发动机实验结果表明：在大多数工况范围内,JCCI发动机的CA10和CA50与点火正时成线性关系,且滞燃期对负荷并不敏感,表明主燃室内柴油预混合气在射流进入前没有发生自燃,之后的着火主要受点火室内的射流影响,可以通过点火正时实现柴油预混合气着火相位的主动控制。在满负荷工况附近,由于压缩比不够低,缸内温度较高,滞燃期较短,柴油预混合气可被压燃,柴油预混合气的着火主要受缸内热力学条件影响。在没有进气增压和EGR的前提下,采用机械供油系统JCCI发动机的NOx和烟度排放均比原柴油机降低较多,最大降幅均超过90%。JCCI发动机数值模拟结果表明：点火室内的火焰在经过点火室与主燃室的小喷孔后,基本发生了淬熄,之后围绕淬熄后的高温活性基射流附近的柴油预混合气首先着火。主燃室内没有明显的火焰传播,而以类似多点自燃的方式发生,燃烧温度低,NO生成量较少。将机械燃油喷射系统改装为电控高压共轨燃油喷射系统,进行了初步实验,结果表明：在较高负荷,NOx降幅超过90%,烟度排放几乎为零；在高负荷,NOx降幅接近80%,烟度排放仍维持在极低的水平,且热效率略高于原柴油机。更多还原

【Abstract】 By synthesizing the advantages of gasoline and diesel engines, Premixed Charge Compression Ignition (PCCI) system with low temperature combustion can achieve ultra-low NOx and PM emissions as well as high efficiency. One of the key obstacles that preventing PCCI from practical use is the control of its combustion phasing. To achieve a direct ignition control of diesel premixed mixture, the Jet Controlled Compression Ignition (JCCI) combustion system was proposed and developed. Triggered with the jets issued from an ignition chamber, the ignition of diesel premixed diesel charge can be directly controlled.A JCCI experimental engine was developed based on a single-cylinder diesel engine CF186FA. The design criterions of the ignition chamber in JCCI combustion system were determined, based on which the ignition chamber and gas fuel supply system was designed and installed in the cylinder head. The shape of piston cavity was modified from the deep co type to a shallow bowl shape which is suitable for premixed combustion and the compression ratio was reduced. High disturbance nozzles combined with early injection strategy was used to form uniform premixed charge. Using CompactRIO platform, the gas injection and spark timing control programs were developed based on the crank angle signal. Using a combination of state machine and producer-consumer, cylinder pressure can be measured simultaneously with gas fuel injection and ignition control. The off-line combustion analysis system was developed using hybrid program of Matlab and Lab VIEW.The experimental results of JCCI engine showed good linear relationships between spark timing and CA10or CA50at most operating conditions, and ignition delay was not sensitive to load, indicating no auto-ignition in main combustion chamber before jet injected from the ignition chamber, and the combustion system possesses the ability of direct combustion phasing control. At about full load, the ignition delay decreased and are a relative early auto-ignition in the main combustion chamber was observed due to high in-cylinder temperature as well as relatively high compression ratio. At these conditions, ignition and combustion of the diesel mixture were controlled by the in-cylinder thermal conditions. Without inlet boost and EGR, the NOx and smoke in JCCI engine with mechanical fuel injection pump were reduced greatly. The max reductions of them were both over90%compared with the original diesel engine.The simulation results of JCCI showed that most of the flame was quenched after passing through the small orifices of the ignition chamber. Then the combustion in the main chamber was initiated around the high temperature radical jets. Due to the absence of flame propagation, the multiple auto-ignition sites can be expected as well as the low temperature and low NO emissions.The high pressure common rail system was used to replace the mechanical fuel injection system. The preliminary experimental results showed that the maximum reduction of NOx was over90%at relatively high load and the smoke was almost zero. At high load, the maximum reduction of NOx was near80%, and the smoke was also very low. The brake thermal efficiency was a little higher than that of original diesel engine.更多还原