Combustion Pattern Recognition And Feedback Control Based On Cylinder Pressure Information For CI Engines

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.