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Direct injection lean-burning technique is one of the most efficient energy-saving technologies nowadays. In this paper, CNG mixture stratification was formed by direct split injection, and by which CNG rapid stratified lean-burning can be carried out when ignited at critical condition. In some certain conditions, pre-injection and main-injection control strategy can be successfully implemented by using a high-speed response spray valve. Fuel well stratified with this control strategy at all condition.The main contents of study contain: CNG direct injection spark-ignited engine system was developed, including a new type combustor, an ignition system, the ECU and the research of single-cylinder GDI natural gas test engine. The control software is based on the AUTOSAR software architecture, divided into four levels: the user application layer, data swap, ECU layer and the MCU level. The control software is based on the AUTOSAR architecture, divided into four layers: the user application layer, data exchange area, ECU layer and the MCU layer. ECU layer provides the various analog signal acquisition, digital signal acquisition, signal analysis on crankshaft and camshaft, injection control, ignition control and other functions, and provides the interface function of each functional module. Layer provides the operation of XC164CM pin, ASC, SSC, CAN, RAM, CC2, and other external equipment. Data exchange area provides data communication services for the user application layer based on software programs and ECU basic software. The application layer loads various types of data MAP and algorithm. It contains input signal fault diagnose, running error diagnose, working condition judgments and compensation control, etc.Tests were aimed at understanding the effect factors on combustion characteristic. Results were as followed: Combustion characteristic and cyclic variation got worse with excess air coefficientΦa increased. And cyclic variation sharply deteriorated until the engine could not work followedΦa reached to lean-burn limitation. An“injection window”exits in low-pressure CNG direct injection engine. An optimal combustion characteristic obtained when injected at this window. Thermal efficiency offset by ignited advance, as a result, combustion process and power improved, gas consumption rate declined, engine dynamic performance could partially recovered. Split injection can improve stratified combustion on low-pressure CNG direct injection engine and combustion efficiency and stability can also be boosted even at lean-burning condition.
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