【作者】 石磊；

【导师】 邓康耀；

【作者基本信息】 上海交通大学 ， 动力机械及工程， 2007， 博士

【摘要】 均质压缩燃烧(Homogeneous Charge Compression Ignition, HCCI)技术具有高效和同时降低NOx和碳烟排放的潜力,均质混合气的制备和燃烧过程的有效控制一直是柴油HCCI燃烧研究的关键问题。为此,本文提出了一种采用内外部EGR结合控制的柴油HCCI燃烧系统。该系统通过在负气门重叠期进行燃油喷射并利用残余高温废气热氛围促进燃油蒸发实现均质混合气的制备,通过外部冷却EGR实现燃烧相位和速率的控制。并进一步采用负气门重叠期结合压缩冲程末期两段燃油喷射策略研究了中高负荷下发动机排放与效率控制问题。本文详细研究了该系统燃烧相位、燃烧速率和排放特性的控制规律,并着重探讨了其负荷扩展问题。围绕负气门重叠期燃油喷射(ETCI:Exhaust TDC Injection)组织柴油HCCI燃烧的思想,首先建立了柴油HCCI燃烧循环模拟程序,并通过将化学动力学和经验模型耦合实现了HCCI燃烧放热率模拟。深入了解了负气门重叠对均质混合气形成和缸内燃烧过程的影响,并模拟研究了内部和外部EGR对HCCI燃烧相位控制的作用。在理论研究的基础上,以单缸柴油机为基础进行了电控可变进排气门正时系统、外部冷却EGR系统和电控高压共轨燃油喷射系统的设计研制,完成了柴油HCCI燃烧试验样机的开发。研究发现采用负气门重叠期喷射燃油可以实现柴油HCCI燃烧,其放热率呈现低温和高温两阶段放热的特点,在HCCI燃烧可以运行的低负荷范围内(负荷上限为原机最高负荷的65%),其NOx排放较相同负荷下的传统柴油机燃烧降低90%~95%,同时碳烟也维持在较低的水平。在试验样机上,进一步详细研究了柴油HCCI燃烧相位、燃烧速率和排放特性的控制规律。从燃烧相位控制的分析来看,使缸内温度升高和燃空当量比增加的影响因素都会造成燃烧相位的提前,不利于负荷上限的扩展。对柴油HCCI燃烧稳定性的分析说明HCCI燃烧在负荷下限时容易出现失火,在负荷上限时容易出现燃烧相位过早和燃烧粗暴,是造成其运行范围较窄的主要原因。以扩展HCCI燃烧负荷范围为目的,着重讨论了内外部EGR对HCCI燃烧负荷更多还原

【Abstract】 Homogeneous Charge Compression Ignition (HCCI) has the potential to significantly reduce NO_x and smoke emissions simultaneously, while achieving high efficiency. The difficulties of homogeneous mixture preparation and combustion control are the key problems for diesel HCCI combustion. So, this paper presents a new diesel HCCI combustion system which is controlled by the internal and external EGR. In this system, fuel is injected in negative valve overlap (NVO) and the high-temperature residual gas benefits the fuel vaporization. All these can solve the problem of homogeneous mixture preparation. Then, the external cooled EGR is used to control the combustion phase and speed. Two-stage injection strategy which includes premix injection in NVO and auxiliary injection in the end of compression stroke is used to achieve high indicated efficiency and low emissions in middle-high load range. The control of combustion phase, speed and emissions of diesel HCCI combustion are studied, and the operation range enlarging problem is discussed.A program for diesel HCCI cycle simulation was developed, in order to understand the effects of NVO on the formation of homogeneous mixture and the combustion process. In this program, the HCCI combustion model coupled chemistry kinetics and experiential model. The effects of internal and external EGR on the combustion phase of diesel HCCI were studied.A diesel HCCI prototype engine was modified from a single-cylinder diesel engine. The variable valve timing (VVT) system, external EGR system and electrical-control common-rail multi-injection system were also developed. It was found that diesel HCCI can be achieved by fuel injection in NVO. In this HCCI combustion, the heat release showed low and high temperature stages, the NO_x emission was reduced about 90%~95% compared with the original diesel engine in the HCCI combustion operation range(below更多还原