【作者】 方成；

【导师】 欧阳明高；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2015， 博士

【摘要】 利用新燃料实现类均质充量压燃(Homogeneous Charge Compression Ignition,HCCI)的燃烧模式,是压燃发动机节能减排的重要途径,基于模型的燃烧反馈控制是实现新型燃烧的关键技术之一。本课题利用开发的汽车级发动机综合控制平台,在一台1.9 L高压共轨柴油机上,研究了低辛烷值燃料的燃烧模式优化和燃烧模式识别,基于缸压信息创建模型反馈各种燃烧指标,协调空气系统和燃油系统,进行燃烧反馈控制,实现了低辛烷值燃料的清洁燃烧。首先,基于汽车级的多核控制芯片,按照ISO 26262标准和AUTOSAR(AUTomotive Open System Architecture)规范,开发了新一代发动机综合控制平台。该平台集成了自主开发的实时操作系统、基于Flex Ray总线的XCP(Universal Measurement and Calibration Protocol)协议和多核协调控制技术,能同时进行混合动力系统控制、发动机控制、燃烧指标计算、燃烧模式识别和燃烧反馈控制。利用70%体积的汽油和30%体积的柴油,配制了低辛烷值燃料G70D30,利用燃烧早喷和废气再循环实现了该燃料的低温预混合燃烧,研究了控制参数对该燃烧模式的影响和该燃烧模式的局限,通过多燃烧模式的组合实现了清洁燃烧负荷拓展,根据优化结果提出了基于燃料特性和工况的燃烧模式识别算法。提出了一种基于等效等熵指数一次微分的燃烧始点检测方法;使用单区燃烧模型计算燃烧放热率,利用预测的纯压缩缸压曲线对燃烧放热率进行传热损失修正;建立了双区燃烧模型,利用物质守恒、能量守恒和化学平衡计算各区燃烧温度;在燃烧模型基础上,建立了氮氧化物排放灰盒模型、半物理模型和炭烟排放灰盒模型。在开发的发动机综合控制平台上,利用自适应转速预测算法,进行高频缸压采集,设计了各个模型计算任务的触发频率、优先级和计算时序,通过实验表明,燃烧始点模型和氮氧化物排放模型在各个工况下输出的指标能用于燃烧反馈控制。最后,针对低辛烷值燃料燃烧模式的特点,进行燃烧动力性、经济性、氮氧化物排放和燃烧边界的反馈控制。调节主喷油量进行平均指示压力闭环控制;调节喷射定时进行燃烧始点和50%放热相位的闭环控制;利用燃烧始点和废气再循环进行氮氧化物排放瞬态控制和稳态控制;通过最大压力升高率、最高爆发压力和燃烧稳定性反馈,对预混合燃烧的边界进行控制。通过发动机实验表明,基于缸压信息建立的燃烧反馈控制器,能够实现燃烧模式识别输出的燃烧目标。更多还原

【Abstract】 To realize HCCI(Homogeneous Charge Compression Ignition) like combustion pattern with new fuel, is one of the most important measures to save energy and reduce emission of compression ignition engine, while model-based combustion control technology is one of the keyprerequisites. This dissertation focuses on the research of combustion pattern optimization and recognition of a low octane number fuel, model-based combustion indices calculation, and combustion feed-back control, in a 1.9L common rail diesel engine, and on anautomotive grade controller developed.In compliance with ISO 26262 standard and AUTOSAR(AUTomotive Open System Architecture) framework, an advanced engine control unit is developedon a new automotive grade multi-core chip, in which a real-time operation system with proprietary intellectual property rights, XCP(Universal Measurement and Calibration Protocol)on FlexRay, and multi-core coordination mechanism are integrated. The control unit has the ability to do hybrid powertrain system coordination, engine control, combustion indices calculation, combustion pattern recognition and combustion feedback control.Partially premixed combustion is implementedby application of exhaust gas recirculation and early injection for alow octane number fuel, which is composed of 70% volume ratio gasoline and 30% volume ratio diesel.The influences of control parameters on such combustion and the limits of this combustion are investigated, and an algorithm combined multiple combustion patterns is presented to extend engine load for low emission combustion related to the test results. A combustion pattern recognition strategy is introduced to identify the combustion targets according to fuel properties and operation conditions subsequently.Anew start of combustion phase detection method base on the analysis of equivalent isentropic indexderivative is proposed. The single zone combustion model is created to calculate heat release rate, which is refined by heat loss calculated from motoring pressure predicted. One two zone combustion model is applied to calculate temperature of different zones on the basis of substance conservation, energy conservation and chemical equilibrium. Then a NOx(nitrogen oxide) grey-box model, a NOx semi-physical model and a soot grey-box model are developed on the combustion models.In the new developed engine control unit, aself-adaptive algorithm is used to esitimate engine speed to generate high frequency triggering event for cylinder pressure acquisition, meanwhile, running frequency, priority and computing sequence of model calculation tasks are determined.Experimental results show that start of combustion phase detected and NOx emission predicted by the control unitsatify the requirements of feedback combustion control under steady and transient engine running conditions.Finally, according to the combustion characteristics of G70D30, a combustion feedback controller, which consists of the power performance control, economic performance control, NOx emission control and combustion boundary control, is developed based on the coordination of air system and fuel system. Main injection quantity is adjusted to meet the requirements of power performance represented by indicated effective mean pressure. Start of combustion phase and 50% heat release phase are closed-loop controlled by means of injection timings modification. NOx emission control is carried out via adjustment of exhaust gas recirculation and start of combustion phase.Combustion boundary is protectedby feedback of combustion instability, maximum rate of pressure rise andpeak pressure. Tests on the dedicated engine demonstratedthat such feedback combustion controller can adapt combustion to the targets provided by combustion pattern recognition module.更多还原